diff --git a/pkg/_fe_analyzer_shared/lib/src/messages/codes_generated.dart b/pkg/_fe_analyzer_shared/lib/src/messages/codes_generated.dart
index 3cd5e84..afd418a 100644
--- a/pkg/_fe_analyzer_shared/lib/src/messages/codes_generated.dart
+++ b/pkg/_fe_analyzer_shared/lib/src/messages/codes_generated.dart
@@ -1515,6 +1515,33 @@
         r"""Try to have all constructors eventually redirect to a non-redirecting constructor.""");
 
 // DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const Template<Message Function(String name)>
+    templateConstructorInitializeSameInstanceVariableSeveralTimes =
+    const Template<Message Function(String name)>(
+        messageTemplate:
+            r"""'#name' was already initialized by this constructor.""",
+        withArguments:
+            _withArgumentsConstructorInitializeSameInstanceVariableSeveralTimes);
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const Code<Message Function(String name)>
+    codeConstructorInitializeSameInstanceVariableSeveralTimes =
+    const Code<Message Function(String name)>(
+        "ConstructorInitializeSameInstanceVariableSeveralTimes",
+        templateConstructorInitializeSameInstanceVariableSeveralTimes,
+        analyzerCodes: <String>["FIELD_INITIALIZED_BY_MULTIPLE_INITIALIZERS"]);
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+Message _withArgumentsConstructorInitializeSameInstanceVariableSeveralTimes(
+    String name) {
+  if (name.isEmpty) throw 'No name provided';
+  name = demangleMixinApplicationName(name);
+  return new Message(codeConstructorInitializeSameInstanceVariableSeveralTimes,
+      message: """'${name}' was already initialized by this constructor.""",
+      arguments: {'name': name});
+}
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
 const Template<Message Function(String name)> templateConstructorNotFound =
     const Template<Message Function(String name)>(
         messageTemplate: r"""Couldn't find constructor '#name'.""",
@@ -3728,6 +3755,60 @@
 }
 
 // DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const Template<
+    Message Function(
+        String
+            name)> templateFieldAlreadyInitializedAtDeclaration = const Template<
+        Message Function(String name)>(
+    messageTemplate:
+        r"""'#name' is a final instance variable that was initialized at the declaration.""",
+    withArguments: _withArgumentsFieldAlreadyInitializedAtDeclaration);
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const Code<Message Function(String name)>
+    codeFieldAlreadyInitializedAtDeclaration =
+    const Code<Message Function(String name)>(
+        "FieldAlreadyInitializedAtDeclaration",
+        templateFieldAlreadyInitializedAtDeclaration,
+        analyzerCodes: <String>[
+      "FIELD_INITIALIZED_IN_INITIALIZER_AND_DECLARATION"
+    ]);
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+Message _withArgumentsFieldAlreadyInitializedAtDeclaration(String name) {
+  if (name.isEmpty) throw 'No name provided';
+  name = demangleMixinApplicationName(name);
+  return new Message(codeFieldAlreadyInitializedAtDeclaration,
+      message:
+          """'${name}' is a final instance variable that was initialized at the declaration.""",
+      arguments: {'name': name});
+}
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const Template<Message Function(String name)>
+    templateFieldAlreadyInitializedAtDeclarationCause =
+    const Template<Message Function(String name)>(
+        messageTemplate: r"""'#name' was initialized here.""",
+        withArguments: _withArgumentsFieldAlreadyInitializedAtDeclarationCause);
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const Code<Message Function(String name)>
+    codeFieldAlreadyInitializedAtDeclarationCause =
+    const Code<Message Function(String name)>(
+        "FieldAlreadyInitializedAtDeclarationCause",
+        templateFieldAlreadyInitializedAtDeclarationCause,
+        severity: Severity.context);
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+Message _withArgumentsFieldAlreadyInitializedAtDeclarationCause(String name) {
+  if (name.isEmpty) throw 'No name provided';
+  name = demangleMixinApplicationName(name);
+  return new Message(codeFieldAlreadyInitializedAtDeclarationCause,
+      message: """'${name}' was initialized here.""",
+      arguments: {'name': name});
+}
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
 const Code<Null> codeFieldInitializedOutsideDeclaringClass =
     messageFieldInitializedOutsideDeclaringClass;
 
@@ -3871,58 +3952,6 @@
 }
 
 // DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
-const Template<Message Function(String name)>
-    templateFinalInstanceVariableAlreadyInitialized =
-    const Template<Message Function(String name)>(
-        messageTemplate:
-            r"""'#name' is a final instance variable that has already been initialized.""",
-        withArguments: _withArgumentsFinalInstanceVariableAlreadyInitialized);
-
-// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
-const Code<Message Function(String name)>
-    codeFinalInstanceVariableAlreadyInitialized =
-    const Code<Message Function(String name)>(
-        "FinalInstanceVariableAlreadyInitialized",
-        templateFinalInstanceVariableAlreadyInitialized,
-        analyzerCodes: <String>["FINAL_INITIALIZED_MULTIPLE_TIMES"]);
-
-// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
-Message _withArgumentsFinalInstanceVariableAlreadyInitialized(String name) {
-  if (name.isEmpty) throw 'No name provided';
-  name = demangleMixinApplicationName(name);
-  return new Message(codeFinalInstanceVariableAlreadyInitialized,
-      message:
-          """'${name}' is a final instance variable that has already been initialized.""",
-      arguments: {'name': name});
-}
-
-// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
-const Template<Message Function(String name)>
-    templateFinalInstanceVariableAlreadyInitializedCause =
-    const Template<Message Function(String name)>(
-        messageTemplate: r"""'#name' was initialized here.""",
-        withArguments:
-            _withArgumentsFinalInstanceVariableAlreadyInitializedCause);
-
-// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
-const Code<Message Function(String name)>
-    codeFinalInstanceVariableAlreadyInitializedCause =
-    const Code<Message Function(String name)>(
-        "FinalInstanceVariableAlreadyInitializedCause",
-        templateFinalInstanceVariableAlreadyInitializedCause,
-        severity: Severity.context);
-
-// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
-Message _withArgumentsFinalInstanceVariableAlreadyInitializedCause(
-    String name) {
-  if (name.isEmpty) throw 'No name provided';
-  name = demangleMixinApplicationName(name);
-  return new Message(codeFinalInstanceVariableAlreadyInitializedCause,
-      message: """'${name}' was initialized here.""",
-      arguments: {'name': name});
-}
-
-// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
 const Code<Null> codeForInLoopExactlyOneVariable =
     messageForInLoopExactlyOneVariable;
 
@@ -6128,14 +6157,14 @@
 }
 
 // DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
-const Code<Null> codeMoreThanOneSuperOrThisInitializer =
-    messageMoreThanOneSuperOrThisInitializer;
+const Code<Null> codeMoreThanOneSuperInitializer =
+    messageMoreThanOneSuperInitializer;
 
 // DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
-const MessageCode messageMoreThanOneSuperOrThisInitializer = const MessageCode(
-    "MoreThanOneSuperOrThisInitializer",
-    analyzerCodes: <String>["SUPER_IN_REDIRECTING_CONSTRUCTOR"],
-    message: r"""Can't have more than one 'super' or 'this' initializer.""");
+const MessageCode messageMoreThanOneSuperInitializer = const MessageCode(
+    "MoreThanOneSuperInitializer",
+    analyzerCodes: <String>["MULTIPLE_SUPER_INITIALIZERS"],
+    message: r"""Can't have more than one 'super' initializer.""");
 
 // DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
 const Code<Null> codeMultipleExtends = messageMultipleExtends;
@@ -6802,6 +6831,15 @@
 }
 
 // DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const Code<Null> codeNullableSpreadError = messageNullableSpreadError;
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const MessageCode messageNullableSpreadError = const MessageCode(
+    "NullableSpreadError",
+    message:
+        r"""An expression whose value can be 'null' must be null-checked before it can be dereferenced.""");
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
 const Template<Message Function(String name)> templateNullableSuperclassError =
     const Template<Message Function(String name)>(
         messageTemplate:
@@ -7606,6 +7644,17 @@
     message: r"""An optional named parameter can't start with '_'.""");
 
 // DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const Code<Null> codeRedirectingConstructorWithAnotherInitializer =
+    messageRedirectingConstructorWithAnotherInitializer;
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const MessageCode messageRedirectingConstructorWithAnotherInitializer =
+    const MessageCode("RedirectingConstructorWithAnotherInitializer",
+        analyzerCodes: <String>["FIELD_INITIALIZER_REDIRECTING_CONSTRUCTOR"],
+        message:
+            r"""A redirecting constructor can't have other initializers.""");
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
 const Code<Null> codeRedirectingConstructorWithBody =
     messageRedirectingConstructorWithBody;
 
@@ -7618,6 +7667,29 @@
         r"""Try removing the body, or not making this a redirecting constructor.""");
 
 // DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const Code<Null> codeRedirectingConstructorWithMultipleRedirectInitializers =
+    messageRedirectingConstructorWithMultipleRedirectInitializers;
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const MessageCode
+    messageRedirectingConstructorWithMultipleRedirectInitializers =
+    const MessageCode("RedirectingConstructorWithMultipleRedirectInitializers",
+        analyzerCodes: <String>["MULTIPLE_REDIRECTING_CONSTRUCTOR_INVOCATIONS"],
+        message:
+            r"""A redirecting constructor can't have more than one redirection.""");
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const Code<Null> codeRedirectingConstructorWithSuperInitializer =
+    messageRedirectingConstructorWithSuperInitializer;
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const MessageCode messageRedirectingConstructorWithSuperInitializer =
+    const MessageCode("RedirectingConstructorWithSuperInitializer",
+        analyzerCodes: <String>["SUPER_IN_REDIRECTING_CONSTRUCTOR"],
+        message:
+            r"""A redirecting constructor can't have a 'super' initializer.""");
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
 const Code<Null> codeRedirectionInNonFactory = messageRedirectionInNonFactory;
 
 // DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
@@ -8413,15 +8485,6 @@
     message: r"""Expected identifier, but got 'this'.""");
 
 // DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
-const Code<Null> codeThisInitializerNotAlone = messageThisInitializerNotAlone;
-
-// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
-const MessageCode messageThisInitializerNotAlone = const MessageCode(
-    "ThisInitializerNotAlone",
-    analyzerCodes: <String>["FIELD_INITIALIZER_REDIRECTING_CONSTRUCTOR"],
-    message: r"""Can't have other initializers together with 'this'.""");
-
-// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
 const Template<Message Function(String string)>
     templateThisOrSuperAccessInFieldInitializer =
     const Template<Message Function(String string)>(
diff --git a/pkg/front_end/lib/src/fasta/builder/constructor_builder.dart b/pkg/front_end/lib/src/fasta/builder/constructor_builder.dart
index ad746d7..8cec3c9 100644
--- a/pkg/front_end/lib/src/fasta/builder/constructor_builder.dart
+++ b/pkg/front_end/lib/src/fasta/builder/constructor_builder.dart
@@ -24,9 +24,11 @@
 import '../messages.dart'
     show
         Message,
-        messageMoreThanOneSuperOrThisInitializer,
+        messageMoreThanOneSuperInitializer,
+        messageRedirectingConstructorWithAnotherInitializer,
+        messageRedirectingConstructorWithMultipleRedirectInitializers,
+        messageRedirectingConstructorWithSuperInitializer,
         messageSuperInitializerNotLast,
-        messageThisInitializerNotAlone,
         noLength;
 
 import '../source/source_library_builder.dart' show SourceLibraryBuilder;
@@ -68,8 +70,8 @@
   /// The [Constructor] built by this builder.
   Constructor get constructor;
 
-  void injectInvalidInitializer(
-      Message message, int charOffset, ExpressionGeneratorHelper helper);
+  void injectInvalidInitializer(Message message, int charOffset, int length,
+      ExpressionGeneratorHelper helper);
 
   void addInitializer(
       Initializer initializer, ExpressionGeneratorHelper helper);
@@ -273,14 +275,14 @@
   Member get member => constructor;
 
   @override
-  void injectInvalidInitializer(
-      Message message, int charOffset, ExpressionGeneratorHelper helper) {
+  void injectInvalidInitializer(Message message, int charOffset, int length,
+      ExpressionGeneratorHelper helper) {
     List<Initializer> initializers = _constructor.initializers;
     Initializer lastInitializer = initializers.removeLast();
     assert(lastInitializer == superInitializer ||
         lastInitializer == redirectingInitializer);
     Initializer error = helper.buildInvalidInitializer(
-        helper.buildProblem(message, charOffset, noLength));
+        helper.buildProblem(message, charOffset, length));
     initializers.add(error..parent = _constructor);
     initializers.add(lastInitializer);
   }
@@ -290,32 +292,64 @@
       Initializer initializer, ExpressionGeneratorHelper helper) {
     List<Initializer> initializers = _constructor.initializers;
     if (initializer is SuperInitializer) {
-      if (superInitializer != null || redirectingInitializer != null) {
-        injectInvalidInitializer(messageMoreThanOneSuperOrThisInitializer,
-            initializer.fileOffset, helper);
+      if (superInitializer != null) {
+        injectInvalidInitializer(messageMoreThanOneSuperInitializer,
+            initializer.fileOffset, "super".length, helper);
+      } else if (redirectingInitializer != null) {
+        injectInvalidInitializer(
+            messageRedirectingConstructorWithSuperInitializer,
+            initializer.fileOffset,
+            "super".length,
+            helper);
       } else {
         initializers.add(initializer..parent = _constructor);
         superInitializer = initializer;
       }
     } else if (initializer is RedirectingInitializer) {
-      if (superInitializer != null || redirectingInitializer != null) {
-        injectInvalidInitializer(messageMoreThanOneSuperOrThisInitializer,
-            initializer.fileOffset, helper);
-      } else if (_constructor.initializers.isNotEmpty) {
-        Initializer first = _constructor.initializers.first;
-        Initializer error = helper.buildInvalidInitializer(helper.buildProblem(
-            messageThisInitializerNotAlone, first.fileOffset, noLength));
-        initializers.add(error..parent = _constructor);
+      if (superInitializer != null) {
+        // Point to the existing super initializer.
+        injectInvalidInitializer(
+            messageRedirectingConstructorWithSuperInitializer,
+            superInitializer.fileOffset,
+            "super".length,
+            helper);
+      } else if (redirectingInitializer != null) {
+        injectInvalidInitializer(
+            messageRedirectingConstructorWithMultipleRedirectInitializers,
+            initializer.fileOffset,
+            noLength,
+            helper);
+      } else if (initializers.isNotEmpty) {
+        // Error on all previous ones.
+        for (int i = 0; i < initializers.length; i++) {
+          Initializer initializer = initializers[i];
+          int length = noLength;
+          if (initializer is AssertInitializer) length = "assert".length;
+          Initializer error = helper.buildInvalidInitializer(
+              helper.buildProblem(
+                  messageRedirectingConstructorWithAnotherInitializer,
+                  initializer.fileOffset,
+                  length));
+          error.parent = _constructor;
+          initializers[i] = error;
+        }
+        initializers.add(initializer..parent = _constructor);
+        redirectingInitializer = initializer;
       } else {
         initializers.add(initializer..parent = _constructor);
         redirectingInitializer = initializer;
       }
     } else if (redirectingInitializer != null) {
+      int length = noLength;
+      if (initializer is AssertInitializer) length = "assert".length;
       injectInvalidInitializer(
-          messageThisInitializerNotAlone, initializer.fileOffset, helper);
+          messageRedirectingConstructorWithAnotherInitializer,
+          initializer.fileOffset,
+          length,
+          helper);
     } else if (superInitializer != null) {
-      injectInvalidInitializer(
-          messageSuperInitializerNotLast, superInitializer.fileOffset, helper);
+      injectInvalidInitializer(messageSuperInitializerNotLast,
+          initializer.fileOffset, noLength, helper);
     } else {
       initializers.add(initializer..parent = _constructor);
     }
diff --git a/pkg/front_end/lib/src/fasta/kernel/body_builder.dart b/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
index 8558d1f..f643d50 100644
--- a/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
@@ -3048,7 +3048,11 @@
     // set or map in some situations, consider always deferring determination
     // until the type resolution phase.
     final int typeArgCount = typeArguments?.length;
-    bool isSet = typeArgCount == 1 ? true : typeArgCount != null ? false : null;
+    bool isSet = typeArgCount == 1
+        ? true
+        : typeArgCount != null
+            ? false
+            : null;
 
     for (int i = 0; i < setOrMapEntries.length; ++i) {
       if (setOrMapEntries[i] is! MapEntry &&
@@ -5852,7 +5856,7 @@
         field,
         value,
         new VariableDeclaration.forValue(buildProblem(
-            fasta.templateFinalInstanceVariableAlreadyInitialized
+            fasta.templateConstructorInitializeSameInstanceVariableSeveralTimes
                 .withArguments(name),
             offset,
             noLength)))
@@ -5907,12 +5911,12 @@
         ];
       } else if (builder.isFinal && builder.hasInitializer) {
         addProblem(
-            fasta.templateFinalInstanceVariableAlreadyInitialized
+            fasta.templateFieldAlreadyInitializedAtDeclaration
                 .withArguments(name),
             assignmentOffset,
             noLength,
             context: [
-              fasta.templateFinalInstanceVariableAlreadyInitializedCause
+              fasta.templateFieldAlreadyInitializedAtDeclarationCause
                   .withArguments(name)
                   .withLocation(uri, builder.charOffset, name.length)
             ]);
diff --git a/pkg/front_end/lib/src/fasta/kernel/class_hierarchy_builder.dart b/pkg/front_end/lib/src/fasta/kernel/class_hierarchy_builder.dart
index 0046492..29e6bd3 100644
--- a/pkg/front_end/lib/src/fasta/kernel/class_hierarchy_builder.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/class_hierarchy_builder.dart
@@ -523,6 +523,10 @@
     for (int i = 0; i < nodes2.length; i++) {
       ClassHierarchyNode node = nodes2[i];
       if (node == null) continue;
+      if (node.classBuilder.cls.isAnonymousMixin) {
+        // Never find unnamed mixin application in least upper bound.
+        continue;
+      }
       if (nodes1.contains(node)) {
         DartType candidate1 = getTypeAsInstanceOf(
             type1, node.classBuilder.cls, clientLibrary, coreTypes);
diff --git a/pkg/front_end/lib/src/fasta/kernel/inference_visitor.dart b/pkg/front_end/lib/src/fasta/kernel/inference_visitor.dart
index ec7bc61..7560e5b 100644
--- a/pkg/front_end/lib/src/fasta/kernel/inference_visitor.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/inference_visitor.dart
@@ -1328,19 +1328,19 @@
     return const StatementInferenceResult();
   }
 
-  DartType getSpreadElementType(DartType spreadType, bool isNullAware) {
-    DartType typeBound = inferrer.resolveTypeParameter(spreadType);
-    if (inferrer.coreTypes.isNull(typeBound)) {
+  DartType getSpreadElementType(
+      DartType spreadType, DartType spreadTypeBound, bool isNullAware) {
+    if (inferrer.coreTypes.isNull(spreadTypeBound)) {
       if (inferrer.isNonNullableByDefault) {
         return isNullAware ? const NeverType(Nullability.nonNullable) : null;
       } else {
         return isNullAware ? inferrer.coreTypes.nullType : null;
       }
     }
-    if (typeBound is InterfaceType) {
+    if (spreadTypeBound is InterfaceType) {
       List<DartType> supertypeArguments = inferrer.typeSchemaEnvironment
           .getTypeArgumentsAsInstanceOf(
-              typeBound, inferrer.coreTypes.iterableClass);
+              spreadTypeBound, inferrer.coreTypes.iterableClass);
       if (supertypeArguments == null) {
         return null;
       }
@@ -1377,9 +1377,10 @@
       DartType spreadType = spreadResult.inferredType;
       inferredSpreadTypes[element.expression] = spreadType;
       Expression replacement = element;
+      DartType spreadTypeBound = inferrer.resolveTypeParameter(spreadType);
+      DartType spreadElementType = getSpreadElementType(
+          spreadType, spreadTypeBound, element.isNullAware);
       if (typeChecksNeeded) {
-        DartType spreadElementType =
-            getSpreadElementType(spreadType, element.isNullAware);
         if (spreadElementType == null) {
           if (inferrer.coreTypes
                   .isNull(inferrer.resolveTypeParameter(spreadType)) &&
@@ -1396,7 +1397,7 @@
                 element.expression.fileOffset,
                 1);
           }
-        } else if (spreadType is InterfaceType) {
+        } else if (spreadTypeBound is InterfaceType) {
           if (!inferrer.isAssignable(inferredTypeArgument, spreadElementType)) {
             replacement = inferrer.helper.buildProblem(
                 templateSpreadElementTypeMismatch.withArguments(
@@ -1405,13 +1406,18 @@
                     inferrer.isNonNullableByDefault),
                 element.expression.fileOffset,
                 1);
+          } else if (inferrer.isNonNullableByDefault &&
+              spreadType.isPotentiallyNullable &&
+              spreadType is! DynamicType &&
+              spreadType != inferrer.coreTypes.nullType &&
+              !element.isNullAware) {
+            replacement = inferrer.helper.buildProblem(
+                messageNullableSpreadError, element.expression.fileOffset, 1);
           }
         }
       }
       // Use 'dynamic' for error recovery.
-      element.elementType =
-          getSpreadElementType(spreadType, element.isNullAware) ??
-              const DynamicType();
+      element.elementType = spreadElementType ?? const DynamicType();
       return new ExpressionInferenceResult(element.elementType, replacement);
     } else if (element is IfElement) {
       DartType boolType =
@@ -1802,8 +1808,9 @@
           spreadType, entry.isNullAware, actualTypes, length);
       DartType actualKeyType = actualTypes[length];
       DartType actualValueType = actualTypes[length + 1];
+      DartType spreadTypeBound = inferrer.resolveTypeParameter(spreadType);
       DartType actualElementType =
-          getSpreadElementType(spreadType, entry.isNullAware);
+          getSpreadElementType(spreadType, spreadTypeBound, entry.isNullAware);
 
       MapEntry replacement = entry;
       if (typeChecksNeeded) {
@@ -1833,7 +1840,7 @@
                 new NullLiteral())
               ..fileOffset = entry.fileOffset;
           }
-        } else if (spreadType is InterfaceType) {
+        } else if (spreadTypeBound is InterfaceType) {
           Expression keyError;
           Expression valueError;
           if (!inferrer.isAssignable(inferredKeyType, actualKeyType)) {
@@ -1854,6 +1861,14 @@
                 entry.expression.fileOffset,
                 1);
           }
+          if (inferrer.isNonNullableByDefault &&
+              spreadType.isPotentiallyNullable &&
+              spreadType is! DynamicType &&
+              spreadType != inferrer.coreTypes.nullType &&
+              !entry.isNullAware) {
+            keyError = inferrer.helper.buildProblem(
+                messageNullableSpreadError, entry.expression.fileOffset, 1);
+          }
           if (keyError != null || valueError != null) {
             keyError ??= new NullLiteral();
             valueError ??= new NullLiteral();
@@ -2331,9 +2346,12 @@
         return new ExpressionInferenceResult(inferredType, setLiteral);
       }
       if (canBeSet && canBeMap && node.entries.isNotEmpty) {
-        Expression error = inferrer.helper.buildProblem(
-            messageCantDisambiguateNotEnoughInformation, node.fileOffset, 1);
-        return new ExpressionInferenceResult(const BottomType(), error);
+        Expression replacement = node;
+        if (!inferrer.isTopLevel) {
+          replacement = inferrer.helper.buildProblem(
+              messageCantDisambiguateNotEnoughInformation, node.fileOffset, 1);
+        }
+        return new ExpressionInferenceResult(const BottomType(), replacement);
       }
       if (!canBeSet && !canBeMap) {
         Expression replacement = node;
diff --git a/pkg/front_end/messages.status b/pkg/front_end/messages.status
index cbf22b3..3844240 100644
--- a/pkg/front_end/messages.status
+++ b/pkg/front_end/messages.status
@@ -334,7 +334,6 @@
 FinalAndCovariant/part_wrapped_script2: Fail
 FinalAndCovariant/script2: Fail
 FinalFieldWithoutInitializer/example: Fail
-FinalInstanceVariableAlreadyInitialized/example: Fail
 ForInLoopElementTypeNotAssignable/example: Fail
 ForInLoopExactlyOneVariable/analyzerCode: Fail # The analyzer doesn't recover well.
 ForInLoopExactlyOneVariable/part_wrapped_statement: Fail
@@ -550,6 +549,8 @@
 NullablePropertyAccessError/example: Fail
 NullablePropertyAccessWarning/analyzerCode: Fail
 NullablePropertyAccessWarning/example: Fail
+NullableSpreadError/analyzerCode: Fail
+NullableSpreadError/example: Fail
 NullableSuperclassError/analyzerCode: Fail
 NullableSuperclassError/example: Fail
 NullableSuperclassWarning/analyzerCode: Fail
diff --git a/pkg/front_end/messages.yaml b/pkg/front_end/messages.yaml
index b3ccbbe..d568f05 100644
--- a/pkg/front_end/messages.yaml
+++ b/pkg/front_end/messages.yaml
@@ -832,21 +832,34 @@
   template: "'#name' isn't an instance field of this class."
   analyzerCode: INITIALIZER_FOR_STATIC_FIELD
 
-MoreThanOneSuperOrThisInitializer:
-  template: "Can't have more than one 'super' or 'this' initializer."
-  analyzerCode: SUPER_IN_REDIRECTING_CONSTRUCTOR
+MoreThanOneSuperInitializer:
+  template: "Can't have more than one 'super' initializer."
+  analyzerCode: MULTIPLE_SUPER_INITIALIZERS
   script:
     - "class C { C.bad() : super(), super(); }"
+
+RedirectingConstructorWithSuperInitializer:
+  template: "A redirecting constructor can't have a 'super' initializer."
+  analyzerCode: SUPER_IN_REDIRECTING_CONSTRUCTOR
+  script:
     - "class C { C(); C.bad() : super(), this(); }"
     - "class C { C(); C.bad() : this(), super(); }"
+
+RedirectingConstructorWithMultipleRedirectInitializers:
+  template: "A redirecting constructor can't have more than one redirection."
+  analyzerCode: MULTIPLE_REDIRECTING_CONSTRUCTOR_INVOCATIONS
+  script:
     - "class C { C(); C.bad() : this(), this(); }"
 
-ThisInitializerNotAlone:
-  template: "Can't have other initializers together with 'this'."
+RedirectingConstructorWithAnotherInitializer:
+  template: "A redirecting constructor can't have other initializers."
+  # also ASSERT_IN_REDIRECTING_CONSTRUCTOR
   analyzerCode: FIELD_INITIALIZER_REDIRECTING_CONSTRUCTOR
   script:
     - "class C { int x; C(); C.bad() : x = 5, this(); }"
     - "class C { int x; C(); C.bad() : this(), x = 5; }"
+    - "class C { int x; C(); C.bad() : assert(true), this(); }"
+    - "class C { int x; C(); C.bad() : this(), assert(true); }"
 
 SuperInitializerNotLast:
   template: "Can't have initializers after 'super'."
@@ -2801,17 +2814,23 @@
   template: "Switch case may fall through to the next case."
   analyzerCode: CASE_BLOCK_NOT_TERMINATED
 
-FinalInstanceVariableAlreadyInitialized:
-  template: "'#name' is a final instance variable that has already been initialized."
-  # TODO(ahe): Strictly speaking, as of
-  # 3b5874a332b24f326775b3520f32b9a818731aca, this is a compile-time error in
-  # legacy mode.
-  analyzerCode: FINAL_INITIALIZED_MULTIPLE_TIMES
+FieldAlreadyInitializedAtDeclaration:
+  template: "'#name' is a final instance variable that was initialized at the declaration."
+  analyzerCode: FIELD_INITIALIZED_IN_INITIALIZER_AND_DECLARATION
+  script:
+    - "class C { final int x = 2; C(): this.x = 3 {} }"
 
-FinalInstanceVariableAlreadyInitializedCause:
+FieldAlreadyInitializedAtDeclarationCause:
   template: "'#name' was initialized here."
   severity: CONTEXT
 
+ConstructorInitializeSameInstanceVariableSeveralTimes:
+  template: "'#name' was already initialized by this constructor."
+  analyzerCode: FIELD_INITIALIZED_BY_MULTIPLE_INITIALIZERS
+  script:
+    - "class C { final int x; C(): this.x = 1, this.x = 2 {} }"
+    - "class C { int x; C(): this.x = 1, this.x = 2 {} }"
+
 TypeVariableInStaticContext:
   template: "Type variables can't be used in static members."
   analyzerCode: TYPE_PARAMETER_REFERENCED_BY_STATIC
@@ -4071,6 +4090,9 @@
 NullableTearoffError:
   template: "Can't tear off method '#name' from a potentially null value."
 
+NullableSpreadError:
+  template: "An expression whose value can be 'null' must be null-checked before it can be dereferenced."
+
 ThrowingNotAssignableToObjectError:
   template: "Can't throw a value of '#type' since it is neither dynamic nor non-nullable."
 
diff --git a/pkg/front_end/test/spell_checking_list_common.txt b/pkg/front_end/test/spell_checking_list_common.txt
index c9f67ed..5882a79 100644
--- a/pkg/front_end/test/spell_checking_list_common.txt
+++ b/pkg/front_end/test/spell_checking_list_common.txt
@@ -793,6 +793,7 @@
 deprecated
 depromotes
 depth
+dereferenced
 derivation
 derive
 derived
diff --git a/pkg/front_end/test/spell_checking_list_tests.txt b/pkg/front_end/test/spell_checking_list_tests.txt
index a825e87..f858baf 100644
--- a/pkg/front_end/test/spell_checking_list_tests.txt
+++ b/pkg/front_end/test/spell_checking_list_tests.txt
@@ -151,6 +151,7 @@
 decrease
 decrements
 dectcem
+deduplication
 defaulting
 defintions
 deleting
@@ -163,6 +164,7 @@
 deviation
 dfast
 di
+diagnosticable
 dictionaries
 dictionary
 differences
@@ -216,6 +218,7 @@
 execute
 exercised
 exercises
+existence
 exitcode
 exiting
 expanded
diff --git a/pkg/front_end/testcases/general/initialzation_errors.dart b/pkg/front_end/testcases/general/initialzation_errors.dart
new file mode 100644
index 0000000..0b399c2
--- /dev/null
+++ b/pkg/front_end/testcases/general/initialzation_errors.dart
@@ -0,0 +1,104 @@
+// Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+class A {
+  int x;
+  A()
+      : this.x = 41,
+        this.x = 42 {}
+}
+
+class B {
+  final int x;
+  B()
+      : this.x = 41,
+        this.x = 42 {}
+}
+
+class C {
+  final int x = 2;
+  C()
+      : this.x = 41,
+        this.x = 42 {}
+}
+
+class D {
+  final int x;
+  final int y;
+  D()
+      : this.x = 41,
+        this.named(),
+        this.y = 42 {}
+  D.named()
+      : this.x = 41,
+        this.y = 42 {}
+}
+
+class E {
+  final int x;
+  final int y;
+  E()
+      : this.named(),
+        this.x = 1,
+        this.y = 2 {}
+  E.named()
+      : this.x = 41,
+        this.y = 42 {}
+  E.named2()
+      : this.x = 1,
+        this.named(),
+        this.y = 2;
+  E.named3()
+      : super(),
+        this.named(),
+        this.x = 1,
+        this.y = 2;
+  E.named4()
+      : this.x = 1,
+        this.y = 2,
+        this.named();
+  E.named5()
+      : assert(true),
+        this.named();
+  E.named6()
+      : this.named(),
+        assert(true);
+}
+
+class F {
+  F()
+      : this.named(),
+        super() {}
+  F.named() {}
+}
+
+class G {
+  G()
+      : super(),
+        this.named(),
+        super() {}
+  G.named() {}
+}
+
+class H {
+  H()
+      : this.named(),
+        this.named();
+  H.named() {}
+}
+
+class I {
+  I()
+      : super(),
+        super() {}
+}
+
+class J {
+  int x;
+  J()
+      : super(),
+        this.x = 42 {}
+}
+
+main() {}
diff --git a/pkg/front_end/testcases/general/initialzation_errors.dart.outline.expect b/pkg/front_end/testcases/general/initialzation_errors.dart.outline.expect
new file mode 100644
index 0000000..df79178
--- /dev/null
+++ b/pkg/front_end/testcases/general/initialzation_errors.dart.outline.expect
@@ -0,0 +1,174 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+class A extends core::Object {
+  field core::int* x;
+  constructor •() → self::A*
+    ;
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+class B extends core::Object {
+  final field core::int* x;
+  constructor •() → self::B*
+    ;
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+class C extends core::Object {
+  final field core::int* x;
+  constructor •() → self::C*
+    ;
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+class D extends core::Object {
+  final field core::int* x;
+  final field core::int* y;
+  constructor •() → self::D*
+    ;
+  constructor named() → self::D*
+    ;
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+class E extends core::Object {
+  final field core::int* x;
+  final field core::int* y;
+  constructor •() → self::E*
+    ;
+  constructor named() → self::E*
+    ;
+  constructor named2() → self::E*
+    ;
+  constructor named3() → self::E*
+    ;
+  constructor named4() → self::E*
+    ;
+  constructor named5() → self::E*
+    ;
+  constructor named6() → self::E*
+    ;
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+class F extends core::Object {
+  constructor •() → self::F*
+    ;
+  constructor named() → self::F*
+    ;
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+class G extends core::Object {
+  constructor •() → self::G*
+    ;
+  constructor named() → self::G*
+    ;
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+class H extends core::Object {
+  constructor •() → self::H*
+    ;
+  constructor named() → self::H*
+    ;
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+class I extends core::Object {
+  constructor •() → self::I*
+    ;
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+class J extends core::Object {
+  field core::int* x;
+  constructor •() → self::J*
+    ;
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+static method main() → dynamic
+  ;
diff --git a/pkg/front_end/testcases/general/initialzation_errors.dart.strong.expect b/pkg/front_end/testcases/general/initialzation_errors.dart.strong.expect
new file mode 100644
index 0000000..fc29ac4
--- /dev/null
+++ b/pkg/front_end/testcases/general/initialzation_errors.dart.strong.expect
@@ -0,0 +1,321 @@
+library;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:9:16: Error: 'x' was already initialized by this constructor.
+//         this.x = 42 {}
+//                ^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:16:16: Error: 'x' was already initialized by this constructor.
+//         this.x = 42 {}
+//                ^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:22:16: Error: 'x' is a final instance variable that was initialized at the declaration.
+//       : this.x = 41,
+//                ^
+// pkg/front_end/testcases/general/initialzation_errors.dart:20:13: Context: 'x' was initialized here.
+//   final int x = 2;
+//             ^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:23:16: Error: 'x' was already initialized by this constructor.
+//         this.x = 42 {}
+//                ^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:30:16: Error: A redirecting constructor can't have other initializers.
+//       : this.x = 41,
+//                ^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:32:16: Error: A redirecting constructor can't have other initializers.
+//         this.y = 42 {}
+//                ^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:43:16: Error: A redirecting constructor can't have other initializers.
+//         this.x = 1,
+//                ^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:44:16: Error: A redirecting constructor can't have other initializers.
+//         this.y = 2 {}
+//                ^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:49:16: Error: A redirecting constructor can't have other initializers.
+//       : this.x = 1,
+//                ^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:51:16: Error: A redirecting constructor can't have other initializers.
+//         this.y = 2;
+//                ^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:53:9: Error: A redirecting constructor can't have a 'super' initializer.
+//       : super(),
+//         ^^^^^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:55:16: Error: Can't have initializers after 'super'.
+//         this.x = 1,
+//                ^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:56:16: Error: Can't have initializers after 'super'.
+//         this.y = 2;
+//                ^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:58:16: Error: A redirecting constructor can't have other initializers.
+//       : this.x = 1,
+//                ^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:59:16: Error: A redirecting constructor can't have other initializers.
+//         this.y = 2,
+//                ^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:62:9: Error: A redirecting constructor can't have other initializers.
+//       : assert(true),
+//         ^^^^^^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:66:9: Error: A redirecting constructor can't have other initializers.
+//         assert(true);
+//         ^^^^^^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:72:9: Error: A redirecting constructor can't have a 'super' initializer.
+//         super() {}
+//         ^^^^^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:78:9: Error: A redirecting constructor can't have a 'super' initializer.
+//       : super(),
+//         ^^^^^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:80:9: Error: Can't have more than one 'super' initializer.
+//         super() {}
+//         ^^^^^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:87:14: Error: A redirecting constructor can't have more than one redirection.
+//         this.named();
+//              ^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:94:9: Error: Can't have more than one 'super' initializer.
+//         super() {}
+//         ^^^^^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:101:16: Error: Can't have initializers after 'super'.
+//         this.x = 42 {}
+//                ^
+//
+import self as self;
+import "dart:core" as core;
+
+class A extends core::Object {
+  field core::int* x;
+  constructor •() → self::A*
+    : self::A::x = 41, final dynamic #t1 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:9:16: Error: 'x' was already initialized by this constructor.
+        this.x = 42 {}
+               ^", super core::Object::•() {}
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+class B extends core::Object {
+  final field core::int* x;
+  constructor •() → self::B*
+    : self::B::x = 41, final dynamic #t2 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:16:16: Error: 'x' was already initialized by this constructor.
+        this.x = 42 {}
+               ^", super core::Object::•() {}
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+class C extends core::Object {
+  final field core::int* x = 2;
+  constructor •() → self::C*
+    : final dynamic #t3 = throw new core::_DuplicatedFieldInitializerError::•("x"), final dynamic #t4 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:23:16: Error: 'x' was already initialized by this constructor.
+        this.x = 42 {}
+               ^", super core::Object::•() {}
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+class D extends core::Object {
+  final field core::int* x;
+  final field core::int* y;
+  constructor •() → self::D*
+    : final dynamic #t5 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:30:16: Error: A redirecting constructor can't have other initializers.
+      : this.x = 41,
+               ^", final dynamic #t6 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:32:16: Error: A redirecting constructor can't have other initializers.
+        this.y = 42 {}
+               ^", this self::D::named() {}
+  constructor named() → self::D*
+    : self::D::x = 41, self::D::y = 42, super core::Object::•() {}
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+class E extends core::Object {
+  final field core::int* x;
+  final field core::int* y;
+  constructor •() → self::E*
+    : final dynamic #t7 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:43:16: Error: A redirecting constructor can't have other initializers.
+        this.x = 1,
+               ^", final dynamic #t8 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:44:16: Error: A redirecting constructor can't have other initializers.
+        this.y = 2 {}
+               ^", this self::E::named() {}
+  constructor named() → self::E*
+    : self::E::x = 41, self::E::y = 42, super core::Object::•() {}
+  constructor named2() → self::E*
+    : final dynamic #t9 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:49:16: Error: A redirecting constructor can't have other initializers.
+      : this.x = 1,
+               ^", final dynamic #t10 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:51:16: Error: A redirecting constructor can't have other initializers.
+        this.y = 2;
+               ^", this self::E::named()
+    ;
+  constructor named3() → self::E*
+    : final dynamic #t11 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:53:9: Error: A redirecting constructor can't have a 'super' initializer.
+      : super(),
+        ^^^^^", final dynamic #t12 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:55:16: Error: Can't have initializers after 'super'.
+        this.x = 1,
+               ^", final dynamic #t13 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:56:16: Error: Can't have initializers after 'super'.
+        this.y = 2;
+               ^", super core::Object::•()
+    ;
+  constructor named4() → self::E*
+    : final dynamic #t14 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:58:16: Error: A redirecting constructor can't have other initializers.
+      : this.x = 1,
+               ^", final dynamic #t15 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:59:16: Error: A redirecting constructor can't have other initializers.
+        this.y = 2,
+               ^", this self::E::named()
+    ;
+  constructor named5() → self::E*
+    : final dynamic #t16 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:62:9: Error: A redirecting constructor can't have other initializers.
+      : assert(true),
+        ^^^^^^", this self::E::named()
+    ;
+  constructor named6() → self::E*
+    : final dynamic #t17 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:66:9: Error: A redirecting constructor can't have other initializers.
+        assert(true);
+        ^^^^^^", this self::E::named()
+    ;
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+class F extends core::Object {
+  constructor •() → self::F*
+    : final dynamic #t18 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:72:9: Error: A redirecting constructor can't have a 'super' initializer.
+        super() {}
+        ^^^^^", this self::F::named() {}
+  constructor named() → self::F*
+    : super core::Object::•() {}
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+class G extends core::Object {
+  constructor •() → self::G*
+    : final dynamic #t19 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:78:9: Error: A redirecting constructor can't have a 'super' initializer.
+      : super(),
+        ^^^^^", final dynamic #t20 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:80:9: Error: Can't have more than one 'super' initializer.
+        super() {}
+        ^^^^^", super core::Object::•() {}
+  constructor named() → self::G*
+    : super core::Object::•() {}
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+class H extends core::Object {
+  constructor •() → self::H*
+    : final dynamic #t21 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:87:14: Error: A redirecting constructor can't have more than one redirection.
+        this.named();
+             ^", this self::H::named()
+    ;
+  constructor named() → self::H*
+    : super core::Object::•() {}
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+class I extends core::Object {
+  constructor •() → self::I*
+    : final dynamic #t22 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:94:9: Error: Can't have more than one 'super' initializer.
+        super() {}
+        ^^^^^", super core::Object::•() {}
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+class J extends core::Object {
+  field core::int* x;
+  constructor •() → self::J*
+    : final dynamic #t23 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:101:16: Error: Can't have initializers after 'super'.
+        this.x = 42 {}
+               ^", super core::Object::•() {}
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+static method main() → dynamic {}
diff --git a/pkg/front_end/testcases/general/initialzation_errors.dart.strong.transformed.expect b/pkg/front_end/testcases/general/initialzation_errors.dart.strong.transformed.expect
new file mode 100644
index 0000000..fc29ac4
--- /dev/null
+++ b/pkg/front_end/testcases/general/initialzation_errors.dart.strong.transformed.expect
@@ -0,0 +1,321 @@
+library;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:9:16: Error: 'x' was already initialized by this constructor.
+//         this.x = 42 {}
+//                ^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:16:16: Error: 'x' was already initialized by this constructor.
+//         this.x = 42 {}
+//                ^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:22:16: Error: 'x' is a final instance variable that was initialized at the declaration.
+//       : this.x = 41,
+//                ^
+// pkg/front_end/testcases/general/initialzation_errors.dart:20:13: Context: 'x' was initialized here.
+//   final int x = 2;
+//             ^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:23:16: Error: 'x' was already initialized by this constructor.
+//         this.x = 42 {}
+//                ^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:30:16: Error: A redirecting constructor can't have other initializers.
+//       : this.x = 41,
+//                ^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:32:16: Error: A redirecting constructor can't have other initializers.
+//         this.y = 42 {}
+//                ^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:43:16: Error: A redirecting constructor can't have other initializers.
+//         this.x = 1,
+//                ^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:44:16: Error: A redirecting constructor can't have other initializers.
+//         this.y = 2 {}
+//                ^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:49:16: Error: A redirecting constructor can't have other initializers.
+//       : this.x = 1,
+//                ^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:51:16: Error: A redirecting constructor can't have other initializers.
+//         this.y = 2;
+//                ^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:53:9: Error: A redirecting constructor can't have a 'super' initializer.
+//       : super(),
+//         ^^^^^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:55:16: Error: Can't have initializers after 'super'.
+//         this.x = 1,
+//                ^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:56:16: Error: Can't have initializers after 'super'.
+//         this.y = 2;
+//                ^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:58:16: Error: A redirecting constructor can't have other initializers.
+//       : this.x = 1,
+//                ^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:59:16: Error: A redirecting constructor can't have other initializers.
+//         this.y = 2,
+//                ^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:62:9: Error: A redirecting constructor can't have other initializers.
+//       : assert(true),
+//         ^^^^^^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:66:9: Error: A redirecting constructor can't have other initializers.
+//         assert(true);
+//         ^^^^^^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:72:9: Error: A redirecting constructor can't have a 'super' initializer.
+//         super() {}
+//         ^^^^^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:78:9: Error: A redirecting constructor can't have a 'super' initializer.
+//       : super(),
+//         ^^^^^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:80:9: Error: Can't have more than one 'super' initializer.
+//         super() {}
+//         ^^^^^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:87:14: Error: A redirecting constructor can't have more than one redirection.
+//         this.named();
+//              ^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:94:9: Error: Can't have more than one 'super' initializer.
+//         super() {}
+//         ^^^^^
+//
+// pkg/front_end/testcases/general/initialzation_errors.dart:101:16: Error: Can't have initializers after 'super'.
+//         this.x = 42 {}
+//                ^
+//
+import self as self;
+import "dart:core" as core;
+
+class A extends core::Object {
+  field core::int* x;
+  constructor •() → self::A*
+    : self::A::x = 41, final dynamic #t1 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:9:16: Error: 'x' was already initialized by this constructor.
+        this.x = 42 {}
+               ^", super core::Object::•() {}
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+class B extends core::Object {
+  final field core::int* x;
+  constructor •() → self::B*
+    : self::B::x = 41, final dynamic #t2 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:16:16: Error: 'x' was already initialized by this constructor.
+        this.x = 42 {}
+               ^", super core::Object::•() {}
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+class C extends core::Object {
+  final field core::int* x = 2;
+  constructor •() → self::C*
+    : final dynamic #t3 = throw new core::_DuplicatedFieldInitializerError::•("x"), final dynamic #t4 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:23:16: Error: 'x' was already initialized by this constructor.
+        this.x = 42 {}
+               ^", super core::Object::•() {}
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+class D extends core::Object {
+  final field core::int* x;
+  final field core::int* y;
+  constructor •() → self::D*
+    : final dynamic #t5 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:30:16: Error: A redirecting constructor can't have other initializers.
+      : this.x = 41,
+               ^", final dynamic #t6 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:32:16: Error: A redirecting constructor can't have other initializers.
+        this.y = 42 {}
+               ^", this self::D::named() {}
+  constructor named() → self::D*
+    : self::D::x = 41, self::D::y = 42, super core::Object::•() {}
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+class E extends core::Object {
+  final field core::int* x;
+  final field core::int* y;
+  constructor •() → self::E*
+    : final dynamic #t7 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:43:16: Error: A redirecting constructor can't have other initializers.
+        this.x = 1,
+               ^", final dynamic #t8 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:44:16: Error: A redirecting constructor can't have other initializers.
+        this.y = 2 {}
+               ^", this self::E::named() {}
+  constructor named() → self::E*
+    : self::E::x = 41, self::E::y = 42, super core::Object::•() {}
+  constructor named2() → self::E*
+    : final dynamic #t9 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:49:16: Error: A redirecting constructor can't have other initializers.
+      : this.x = 1,
+               ^", final dynamic #t10 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:51:16: Error: A redirecting constructor can't have other initializers.
+        this.y = 2;
+               ^", this self::E::named()
+    ;
+  constructor named3() → self::E*
+    : final dynamic #t11 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:53:9: Error: A redirecting constructor can't have a 'super' initializer.
+      : super(),
+        ^^^^^", final dynamic #t12 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:55:16: Error: Can't have initializers after 'super'.
+        this.x = 1,
+               ^", final dynamic #t13 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:56:16: Error: Can't have initializers after 'super'.
+        this.y = 2;
+               ^", super core::Object::•()
+    ;
+  constructor named4() → self::E*
+    : final dynamic #t14 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:58:16: Error: A redirecting constructor can't have other initializers.
+      : this.x = 1,
+               ^", final dynamic #t15 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:59:16: Error: A redirecting constructor can't have other initializers.
+        this.y = 2,
+               ^", this self::E::named()
+    ;
+  constructor named5() → self::E*
+    : final dynamic #t16 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:62:9: Error: A redirecting constructor can't have other initializers.
+      : assert(true),
+        ^^^^^^", this self::E::named()
+    ;
+  constructor named6() → self::E*
+    : final dynamic #t17 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:66:9: Error: A redirecting constructor can't have other initializers.
+        assert(true);
+        ^^^^^^", this self::E::named()
+    ;
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+class F extends core::Object {
+  constructor •() → self::F*
+    : final dynamic #t18 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:72:9: Error: A redirecting constructor can't have a 'super' initializer.
+        super() {}
+        ^^^^^", this self::F::named() {}
+  constructor named() → self::F*
+    : super core::Object::•() {}
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+class G extends core::Object {
+  constructor •() → self::G*
+    : final dynamic #t19 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:78:9: Error: A redirecting constructor can't have a 'super' initializer.
+      : super(),
+        ^^^^^", final dynamic #t20 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:80:9: Error: Can't have more than one 'super' initializer.
+        super() {}
+        ^^^^^", super core::Object::•() {}
+  constructor named() → self::G*
+    : super core::Object::•() {}
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+class H extends core::Object {
+  constructor •() → self::H*
+    : final dynamic #t21 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:87:14: Error: A redirecting constructor can't have more than one redirection.
+        this.named();
+             ^", this self::H::named()
+    ;
+  constructor named() → self::H*
+    : super core::Object::•() {}
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+class I extends core::Object {
+  constructor •() → self::I*
+    : final dynamic #t22 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:94:9: Error: Can't have more than one 'super' initializer.
+        super() {}
+        ^^^^^", super core::Object::•() {}
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+class J extends core::Object {
+  field core::int* x;
+  constructor •() → self::J*
+    : final dynamic #t23 = invalid-expression "pkg/front_end/testcases/general/initialzation_errors.dart:101:16: Error: Can't have initializers after 'super'.
+        this.x = 42 {}
+               ^", super core::Object::•() {}
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+static method main() → dynamic {}
diff --git a/pkg/front_end/testcases/general/initialzation_errors.dart.textual_outline.expect b/pkg/front_end/testcases/general/initialzation_errors.dart.textual_outline.expect
new file mode 100644
index 0000000..f1eb7f2
--- /dev/null
+++ b/pkg/front_end/testcases/general/initialzation_errors.dart.textual_outline.expect
@@ -0,0 +1,100 @@
+class A {
+  int x;
+  A()
+      : this.x = 41,
+        this.x = 42 {}
+}
+
+class B {
+  final int x;
+  B()
+      : this.x = 41,
+        this.x = 42 {}
+}
+
+class C {
+  final int x = 2;
+  C()
+      : this.x = 41,
+        this.x = 42 {}
+}
+
+class D {
+  final int x;
+  final int y;
+  D()
+      : this.x = 41,
+        this.named(),
+        this.y = 42 {}
+  D.named()
+      : this.x = 41,
+        this.y = 42 {}
+}
+
+class E {
+  final int x;
+  final int y;
+  E()
+      : this.named(),
+        this.x = 1,
+        this.y = 2 {}
+  E.named()
+      : this.x = 41,
+        this.y = 42 {}
+  E.named2()
+      : this.x = 1,
+        this.named(),
+        this.y = 2;
+  E.named3()
+      : super(),
+        this.named(),
+        this.x = 1,
+        this.y = 2;
+  E.named4()
+      : this.x = 1,
+        this.y = 2,
+        this.named();
+  E.named5()
+      : assert(true),
+        this.named();
+  E.named6()
+      : this.named(),
+        assert(true);
+}
+
+class F {
+  F()
+      : this.named(),
+        super() {}
+  F.named() {}
+}
+
+class G {
+  G()
+      : super(),
+        this.named(),
+        super() {}
+  G.named() {}
+}
+
+class H {
+  H()
+      : this.named(),
+        this.named();
+  H.named() {}
+}
+
+class I {
+  I()
+      : super(),
+        super() {}
+}
+
+class J {
+  int x;
+  J()
+      : super(),
+        this.x = 42 {}
+}
+
+main() {}
diff --git a/pkg/front_end/testcases/general/initialzation_errors.dart.textual_outline_modelled.expect b/pkg/front_end/testcases/general/initialzation_errors.dart.textual_outline_modelled.expect
new file mode 100644
index 0000000..f09d803
--- /dev/null
+++ b/pkg/front_end/testcases/general/initialzation_errors.dart.textual_outline_modelled.expect
@@ -0,0 +1,100 @@
+class A {
+  A()
+      : this.x = 41,
+        this.x = 42 {}
+  int x;
+}
+
+class B {
+  B()
+      : this.x = 41,
+        this.x = 42 {}
+  final int x;
+}
+
+class C {
+  C()
+      : this.x = 41,
+        this.x = 42 {}
+  final int x = 2;
+}
+
+class D {
+  D()
+      : this.x = 41,
+        this.named(),
+        this.y = 42 {}
+  D.named()
+      : this.x = 41,
+        this.y = 42 {}
+  final int x;
+  final int y;
+}
+
+class E {
+  E()
+      : this.named(),
+        this.x = 1,
+        this.y = 2 {}
+  E.named()
+      : this.x = 41,
+        this.y = 42 {}
+  E.named2()
+      : this.x = 1,
+        this.named(),
+        this.y = 2;
+  E.named3()
+      : super(),
+        this.named(),
+        this.x = 1,
+        this.y = 2;
+  E.named4()
+      : this.x = 1,
+        this.y = 2,
+        this.named();
+  E.named5()
+      : assert(true),
+        this.named();
+  E.named6()
+      : this.named(),
+        assert(true);
+  final int x;
+  final int y;
+}
+
+class F {
+  F()
+      : this.named(),
+        super() {}
+  F.named() {}
+}
+
+class G {
+  G()
+      : super(),
+        this.named(),
+        super() {}
+  G.named() {}
+}
+
+class H {
+  H()
+      : this.named(),
+        this.named();
+  H.named() {}
+}
+
+class I {
+  I()
+      : super(),
+        super() {}
+}
+
+class J {
+  J()
+      : super(),
+        this.x = 42 {}
+  int x;
+}
+
+main() {}
diff --git a/pkg/front_end/testcases/general/many_errors.dart.outline.expect b/pkg/front_end/testcases/general/many_errors.dart.outline.expect
index 0493c42..623c813 100644
--- a/pkg/front_end/testcases/general/many_errors.dart.outline.expect
+++ b/pkg/front_end/testcases/general/many_errors.dart.outline.expect
@@ -15,7 +15,7 @@
 //   const A.named2() : x = new Object();
 //                          ^^^
 //
-// pkg/front_end/testcases/general/many_errors.dart:10:24: Error: 'x' is a final instance variable that has already been initialized.
+// pkg/front_end/testcases/general/many_errors.dart:10:24: Error: 'x' is a final instance variable that was initialized at the declaration.
 //   const A.named2() : x = new Object();
 //                        ^
 // pkg/front_end/testcases/general/many_errors.dart:6:9: Context: 'x' was initialized here.
diff --git a/pkg/front_end/testcases/general/many_errors.dart.strong.expect b/pkg/front_end/testcases/general/many_errors.dart.strong.expect
index 5dcbf8b..c04f498 100644
--- a/pkg/front_end/testcases/general/many_errors.dart.strong.expect
+++ b/pkg/front_end/testcases/general/many_errors.dart.strong.expect
@@ -15,7 +15,7 @@
 //   const A.named2() : x = new Object();
 //                          ^^^
 //
-// pkg/front_end/testcases/general/many_errors.dart:10:24: Error: 'x' is a final instance variable that has already been initialized.
+// pkg/front_end/testcases/general/many_errors.dart:10:24: Error: 'x' is a final instance variable that was initialized at the declaration.
 //   const A.named2() : x = new Object();
 //                        ^
 // pkg/front_end/testcases/general/many_errors.dart:6:9: Context: 'x' was initialized here.
diff --git a/pkg/front_end/testcases/general/many_errors.dart.strong.transformed.expect b/pkg/front_end/testcases/general/many_errors.dart.strong.transformed.expect
index 5dcbf8b..c04f498 100644
--- a/pkg/front_end/testcases/general/many_errors.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/general/many_errors.dart.strong.transformed.expect
@@ -15,7 +15,7 @@
 //   const A.named2() : x = new Object();
 //                          ^^^
 //
-// pkg/front_end/testcases/general/many_errors.dart:10:24: Error: 'x' is a final instance variable that has already been initialized.
+// pkg/front_end/testcases/general/many_errors.dart:10:24: Error: 'x' is a final instance variable that was initialized at the declaration.
 //   const A.named2() : x = new Object();
 //                        ^
 // pkg/front_end/testcases/general/many_errors.dart:6:9: Context: 'x' was initialized here.
diff --git a/pkg/front_end/testcases/general/mixin_application_lub.dart b/pkg/front_end/testcases/general/mixin_application_lub.dart
new file mode 100644
index 0000000..a144b92
--- /dev/null
+++ b/pkg/front_end/testcases/general/mixin_application_lub.dart
@@ -0,0 +1,31 @@
+// Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+class Diagnosticable {}
+
+// Originally the existence of this (unused) class (which has an anonymous mixin
+// that matches that of `State<T>`) caused an error in the VM's mixin
+// deduplication code. This was due to the inferred type for `var x = a ?? b`
+// was the anonymous mixin application that got removed during deduplication.
+//
+// See https://github.com/flutter/flutter/issues/55345
+class SomeClass with Diagnosticable {}
+
+class State<T> with Diagnosticable {}
+
+class StateA extends State {}
+
+class StateB extends State<int> {}
+
+StateA a = StateA();
+StateB b = StateB();
+
+foo<T>(T x) {
+  print(T);
+}
+
+main() {
+  var x = a ?? b;
+  foo(x);
+}
diff --git a/pkg/front_end/testcases/general/mixin_application_lub.dart.outline.expect b/pkg/front_end/testcases/general/mixin_application_lub.dart.outline.expect
new file mode 100644
index 0000000..cf58674
--- /dev/null
+++ b/pkg/front_end/testcases/general/mixin_application_lub.dart.outline.expect
@@ -0,0 +1,70 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+class Diagnosticable extends core::Object {
+  synthetic constructor •() → self::Diagnosticable*
+    ;
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+abstract class _SomeClass&Object&Diagnosticable = core::Object with self::Diagnosticable /*isAnonymousMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_SomeClass&Object&Diagnosticable*
+    : super core::Object::•()
+    ;
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+class SomeClass extends self::_SomeClass&Object&Diagnosticable {
+  synthetic constructor •() → self::SomeClass*
+    ;
+}
+abstract class _State&Object&Diagnosticable = core::Object with self::Diagnosticable /*isAnonymousMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_State&Object&Diagnosticable*
+    : super core::Object::•()
+    ;
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+class State<T extends core::Object* = dynamic> extends self::_State&Object&Diagnosticable {
+  synthetic constructor •() → self::State<self::State::T*>*
+    ;
+}
+class StateA extends self::State<dynamic> {
+  synthetic constructor •() → self::StateA*
+    ;
+}
+class StateB extends self::State<core::int*> {
+  synthetic constructor •() → self::StateB*
+    ;
+}
+static field self::StateA* a;
+static field self::StateB* b;
+static method foo<T extends core::Object* = dynamic>(self::foo::T* x) → dynamic
+  ;
+static method main() → dynamic
+  ;
diff --git a/pkg/front_end/testcases/general/mixin_application_lub.dart.strong.expect b/pkg/front_end/testcases/general/mixin_application_lub.dart.strong.expect
new file mode 100644
index 0000000..e277693
--- /dev/null
+++ b/pkg/front_end/testcases/general/mixin_application_lub.dart.strong.expect
@@ -0,0 +1,78 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+class Diagnosticable extends core::Object {
+  synthetic constructor •() → self::Diagnosticable*
+    : super core::Object::•()
+    ;
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+abstract class _SomeClass&Object&Diagnosticable = core::Object with self::Diagnosticable /*isAnonymousMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_SomeClass&Object&Diagnosticable*
+    : super core::Object::•()
+    ;
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+class SomeClass extends self::_SomeClass&Object&Diagnosticable {
+  synthetic constructor •() → self::SomeClass*
+    : super self::_SomeClass&Object&Diagnosticable::•()
+    ;
+}
+abstract class _State&Object&Diagnosticable = core::Object with self::Diagnosticable /*isAnonymousMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_State&Object&Diagnosticable*
+    : super core::Object::•()
+    ;
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+class State<T extends core::Object* = dynamic> extends self::_State&Object&Diagnosticable {
+  synthetic constructor •() → self::State<self::State::T*>*
+    : super self::_State&Object&Diagnosticable::•()
+    ;
+}
+class StateA extends self::State<dynamic> {
+  synthetic constructor •() → self::StateA*
+    : super self::State::•()
+    ;
+}
+class StateB extends self::State<core::int*> {
+  synthetic constructor •() → self::StateB*
+    : super self::State::•()
+    ;
+}
+static field self::StateA* a = new self::StateA::•();
+static field self::StateB* b = new self::StateB::•();
+static method foo<T extends core::Object* = dynamic>(self::foo::T* x) → dynamic {
+  core::print(self::foo::T*);
+}
+static method main() → dynamic {
+  self::Diagnosticable* x = let final self::StateA* #t1 = self::a in #t1.{self::_State&Object&Diagnosticable::==}(null) ?{self::Diagnosticable*} self::b : #t1;
+  self::foo<self::Diagnosticable*>(x);
+}
diff --git a/pkg/front_end/testcases/general/mixin_application_lub.dart.strong.transformed.expect b/pkg/front_end/testcases/general/mixin_application_lub.dart.strong.transformed.expect
new file mode 100644
index 0000000..421798b
--- /dev/null
+++ b/pkg/front_end/testcases/general/mixin_application_lub.dart.strong.transformed.expect
@@ -0,0 +1,78 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+class Diagnosticable extends core::Object {
+  synthetic constructor •() → self::Diagnosticable*
+    : super core::Object::•()
+    ;
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+abstract class _SomeClass&Object&Diagnosticable extends core::Object implements self::Diagnosticable /*isAnonymousMixin,isEliminatedMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_SomeClass&Object&Diagnosticable*
+    : super core::Object::•()
+    ;
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+class SomeClass extends self::_SomeClass&Object&Diagnosticable {
+  synthetic constructor •() → self::SomeClass*
+    : super self::_SomeClass&Object&Diagnosticable::•()
+    ;
+}
+abstract class _State&Object&Diagnosticable extends core::Object implements self::Diagnosticable /*isAnonymousMixin,isEliminatedMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::_State&Object&Diagnosticable*
+    : super core::Object::•()
+    ;
+  abstract member-signature get _identityHashCode() → core::int*; -> core::Object::_identityHashCode
+  abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → core::bool*; -> core::Object::_instanceOf
+  abstract member-signature method _simpleInstanceOf(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOf
+  abstract member-signature method _simpleInstanceOfTrue(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfTrue
+  abstract member-signature method _simpleInstanceOfFalse(dynamic type) → core::bool*; -> core::Object::_simpleInstanceOfFalse
+  abstract member-signature operator ==(dynamic other) → core::bool*; -> core::Object::==
+  abstract member-signature get hashCode() → core::int*; -> core::Object::hashCode
+  abstract member-signature method toString() → core::String*; -> core::Object::toString
+  abstract member-signature method noSuchMethod(core::Invocation* invocation) → dynamic; -> core::Object::noSuchMethod
+  abstract member-signature get runtimeType() → core::Type*; -> core::Object::runtimeType
+}
+class State<T extends core::Object* = dynamic> extends self::_State&Object&Diagnosticable {
+  synthetic constructor •() → self::State<self::State::T*>*
+    : super self::_State&Object&Diagnosticable::•()
+    ;
+}
+class StateA extends self::State<dynamic> {
+  synthetic constructor •() → self::StateA*
+    : super self::State::•()
+    ;
+}
+class StateB extends self::State<core::int*> {
+  synthetic constructor •() → self::StateB*
+    : super self::State::•()
+    ;
+}
+static field self::StateA* a = new self::StateA::•();
+static field self::StateB* b = new self::StateB::•();
+static method foo<T extends core::Object* = dynamic>(self::foo::T* x) → dynamic {
+  core::print(self::foo::T*);
+}
+static method main() → dynamic {
+  self::Diagnosticable* x = let final self::StateA* #t1 = self::a in #t1.{self::_State&Object&Diagnosticable::==}(null) ?{self::Diagnosticable*} self::b : #t1;
+  self::foo<self::Diagnosticable*>(x);
+}
diff --git a/pkg/front_end/testcases/general/mixin_application_lub.dart.textual_outline.expect b/pkg/front_end/testcases/general/mixin_application_lub.dart.textual_outline.expect
new file mode 100644
index 0000000..5603659
--- /dev/null
+++ b/pkg/front_end/testcases/general/mixin_application_lub.dart.textual_outline.expect
@@ -0,0 +1,14 @@
+class Diagnosticable {}
+
+class SomeClass with Diagnosticable {}
+
+class State<T> with Diagnosticable {}
+
+class StateA extends State {}
+
+class StateB extends State<int> {}
+
+StateA a = StateA();
+StateB b = StateB();
+foo<T>(T x) {}
+main() {}
diff --git a/pkg/front_end/testcases/general/mixin_application_lub.dart.textual_outline_modelled.expect b/pkg/front_end/testcases/general/mixin_application_lub.dart.textual_outline_modelled.expect
new file mode 100644
index 0000000..0d56a51
--- /dev/null
+++ b/pkg/front_end/testcases/general/mixin_application_lub.dart.textual_outline_modelled.expect
@@ -0,0 +1,15 @@
+StateA a = StateA();
+StateB b = StateB();
+
+class Diagnosticable {}
+
+class SomeClass with Diagnosticable {}
+
+class State<T> with Diagnosticable {}
+
+class StateA extends State {}
+
+class StateB extends State<int> {}
+
+foo<T>(T x) {}
+main() {}
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart.weak.expect b/pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart.weak.expect
index b3f3142..c4c2ced 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart.weak.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart.weak.expect
@@ -15,7 +15,7 @@
 //   const A.named2() : x = new Object();
 //                          ^^^
 //
-// pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart:12:24: Error: 'x' is a final instance variable that has already been initialized.
+// pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart:12:24: Error: 'x' is a final instance variable that was initialized at the declaration.
 //   const A.named2() : x = new Object();
 //                        ^
 // pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart:8:9: Context: 'x' was initialized here.
diff --git a/pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart.weak.transformed.expect b/pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart.weak.transformed.expect
index b3f3142..c4c2ced 100644
--- a/pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart.weak.transformed.expect
@@ -15,7 +15,7 @@
 //   const A.named2() : x = new Object();
 //                          ^^^
 //
-// pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart:12:24: Error: 'x' is a final instance variable that has already been initialized.
+// pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart:12:24: Error: 'x' is a final instance variable that was initialized at the declaration.
 //   const A.named2() : x = new Object();
 //                        ^
 // pkg/front_end/testcases/general_nnbd_opt_out/many_errors.dart:8:9: Context: 'x' was initialized here.
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/issue_32366.yaml b/pkg/front_end/testcases/incremental_initialize_from_dill/issue_32366.yaml
new file mode 100644
index 0000000..c049a7d
--- /dev/null
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/issue_32366.yaml
@@ -0,0 +1,38 @@
+# Copyright (c) 2020, the Dart project authors. Please see the AUTHORS file
+# for details. All rights reserved. Use of this source code is governed by a
+# BSD-style license that can be found in the LICENSE.md file.
+
+# Reproduction of https://github.com/dart-lang/sdk/issues/32366.
+type: newworld
+worlds:
+  - entry: main.dart
+    sources:
+      main.dart: |
+        abstract class AIterator extends Iterator {
+        }
+        class Foo {
+          final a;
+          Foo(this.a);
+        }
+        main() {
+          new Foo(5);
+          return 1;
+        }
+    expectedLibraryCount: 1
+  - entry: main.dart
+    invalidate:
+      - main.dart
+    errors: true
+    sources:
+      main.dart: |
+        abstract class BIterator extends Iterator {
+        }
+        class Foo {
+          final a kjsdf ksjdf ;
+          Foo(this.a);
+        }
+        main() {
+          new Foo(5);
+          return 2;
+        }
+    expectedLibraryCount: 1
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/issue_32366.yaml.world.1.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/issue_32366.yaml.world.1.expect
new file mode 100644
index 0000000..886b31c
--- /dev/null
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/issue_32366.yaml.world.1.expect
@@ -0,0 +1,40 @@
+main = <No Member>;
+library from "org-dartlang-test:///main.dart" as main {
+
+  abstract class AIterator extends dart.core::Iterator<dynamic> {
+    synthetic constructor •() → main::AIterator*
+      : super dart.core::Iterator::•()
+      ;
+    abstract member-signature method moveNext() → dart.core::bool*; -> dart.core::Iterator::moveNext
+    abstract member-signature get _identityHashCode() → dart.core::int*; -> dart.core::Object::_identityHashCode
+    abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → dart.core::bool*; -> dart.core::Object::_instanceOf
+    abstract member-signature method _simpleInstanceOf(dynamic type) → dart.core::bool*; -> dart.core::Object::_simpleInstanceOf
+    abstract member-signature method _simpleInstanceOfTrue(dynamic type) → dart.core::bool*; -> dart.core::Object::_simpleInstanceOfTrue
+    abstract member-signature method _simpleInstanceOfFalse(dynamic type) → dart.core::bool*; -> dart.core::Object::_simpleInstanceOfFalse
+    abstract member-signature operator ==(dynamic other) → dart.core::bool*; -> dart.core::Object::==
+    abstract member-signature get hashCode() → dart.core::int*; -> dart.core::Object::hashCode
+    abstract member-signature method toString() → dart.core::String*; -> dart.core::Object::toString
+    abstract member-signature method noSuchMethod(dart.core::Invocation* invocation) → dynamic; -> dart.core::Object::noSuchMethod
+    abstract member-signature get runtimeType() → dart.core::Type*; -> dart.core::Object::runtimeType
+  }
+  class Foo extends dart.core::Object {
+    final field dynamic a;
+    constructor •(dynamic a) → main::Foo*
+      : main::Foo::a = a, super dart.core::Object::•()
+      ;
+    abstract member-signature get _identityHashCode() → dart.core::int*; -> dart.core::Object::_identityHashCode
+    abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → dart.core::bool*; -> dart.core::Object::_instanceOf
+    abstract member-signature method _simpleInstanceOf(dynamic type) → dart.core::bool*; -> dart.core::Object::_simpleInstanceOf
+    abstract member-signature method _simpleInstanceOfTrue(dynamic type) → dart.core::bool*; -> dart.core::Object::_simpleInstanceOfTrue
+    abstract member-signature method _simpleInstanceOfFalse(dynamic type) → dart.core::bool*; -> dart.core::Object::_simpleInstanceOfFalse
+    abstract member-signature operator ==(dynamic other) → dart.core::bool*; -> dart.core::Object::==
+    abstract member-signature get hashCode() → dart.core::int*; -> dart.core::Object::hashCode
+    abstract member-signature method toString() → dart.core::String*; -> dart.core::Object::toString
+    abstract member-signature method noSuchMethod(dart.core::Invocation* invocation) → dynamic; -> dart.core::Object::noSuchMethod
+    abstract member-signature get runtimeType() → dart.core::Type*; -> dart.core::Object::runtimeType
+  }
+  static method main() → dynamic {
+    new main::Foo::•(5);
+    return 1;
+  }
+}
diff --git a/pkg/front_end/testcases/incremental_initialize_from_dill/issue_32366.yaml.world.2.expect b/pkg/front_end/testcases/incremental_initialize_from_dill/issue_32366.yaml.world.2.expect
new file mode 100644
index 0000000..ef7453c
--- /dev/null
+++ b/pkg/front_end/testcases/incremental_initialize_from_dill/issue_32366.yaml.world.2.expect
@@ -0,0 +1,70 @@
+main = <No Member>;
+library from "org-dartlang-test:///main.dart" as main {
+//
+// Problems in library:
+//
+// org-dartlang-test:///main.dart:4:11: Error: Expected ';' after this.
+//   final a kjsdf ksjdf ;
+//           ^^^^^
+//
+// org-dartlang-test:///main.dart:4:11: Error: Final field 'kjsdf' is not initialized.
+// Try to initialize the field in the declaration or in every constructor.
+//   final a kjsdf ksjdf ;
+//           ^^^^^
+//
+// org-dartlang-test:///main.dart:4:17: Error: Variables must be declared using the keywords 'const', 'final', 'var' or a type name.
+// Try adding the name of the type of the variable or the keyword 'var'.
+//   final a kjsdf ksjdf ;
+//                 ^^^^^
+//
+// org-dartlang-test:///main.dart:4:9: Error: 'a' isn't a type.
+//   final a kjsdf ksjdf ;
+//         ^
+//
+// org-dartlang-test:///main.dart:4:9: Error: Type 'a' not found.
+//   final a kjsdf ksjdf ;
+//         ^
+//
+// org-dartlang-test:///main.dart:5:12: Error: 'a' isn't an instance field of this class.
+//   Foo(this.a);
+//            ^
+//
+
+  abstract class BIterator extends dart.core::Iterator<dynamic> {
+    synthetic constructor •() → main::BIterator*
+      : super dart.core::Iterator::•()
+      ;
+    abstract member-signature method moveNext() → dart.core::bool*; -> dart.core::Iterator::moveNext
+    abstract member-signature get _identityHashCode() → dart.core::int*; -> dart.core::Object::_identityHashCode
+    abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → dart.core::bool*; -> dart.core::Object::_instanceOf
+    abstract member-signature method _simpleInstanceOf(dynamic type) → dart.core::bool*; -> dart.core::Object::_simpleInstanceOf
+    abstract member-signature method _simpleInstanceOfTrue(dynamic type) → dart.core::bool*; -> dart.core::Object::_simpleInstanceOfTrue
+    abstract member-signature method _simpleInstanceOfFalse(dynamic type) → dart.core::bool*; -> dart.core::Object::_simpleInstanceOfFalse
+    abstract member-signature operator ==(dynamic other) → dart.core::bool*; -> dart.core::Object::==
+    abstract member-signature get hashCode() → dart.core::int*; -> dart.core::Object::hashCode
+    abstract member-signature method toString() → dart.core::String*; -> dart.core::Object::toString
+    abstract member-signature method noSuchMethod(dart.core::Invocation* invocation) → dynamic; -> dart.core::Object::noSuchMethod
+    abstract member-signature get runtimeType() → dart.core::Type*; -> dart.core::Object::runtimeType
+  }
+  class Foo extends dart.core::Object {
+    final field invalid-type kjsdf = null;
+    field dynamic ksjdf = null;
+    constructor •(dynamic a) → main::Foo*
+      : final dynamic #t1 = invalid-expression "org-dartlang-test:///main.dart:5:12: Error: 'a' isn't an instance field of this class.\n  Foo(this.a);\n           ^"
+      ;
+    abstract member-signature get _identityHashCode() → dart.core::int*; -> dart.core::Object::_identityHashCode
+    abstract member-signature method _instanceOf(dynamic instantiatorTypeArguments, dynamic functionTypeArguments, dynamic type) → dart.core::bool*; -> dart.core::Object::_instanceOf
+    abstract member-signature method _simpleInstanceOf(dynamic type) → dart.core::bool*; -> dart.core::Object::_simpleInstanceOf
+    abstract member-signature method _simpleInstanceOfTrue(dynamic type) → dart.core::bool*; -> dart.core::Object::_simpleInstanceOfTrue
+    abstract member-signature method _simpleInstanceOfFalse(dynamic type) → dart.core::bool*; -> dart.core::Object::_simpleInstanceOfFalse
+    abstract member-signature operator ==(dynamic other) → dart.core::bool*; -> dart.core::Object::==
+    abstract member-signature get hashCode() → dart.core::int*; -> dart.core::Object::hashCode
+    abstract member-signature method toString() → dart.core::String*; -> dart.core::Object::toString
+    abstract member-signature method noSuchMethod(dart.core::Invocation* invocation) → dynamic; -> dart.core::Object::noSuchMethod
+    abstract member-signature get runtimeType() → dart.core::Type*; -> dart.core::Object::runtimeType
+  }
+  static method main() → dynamic {
+    new main::Foo::•(5);
+    return 2;
+  }
+}
diff --git a/pkg/front_end/testcases/nnbd/issue43256.dart b/pkg/front_end/testcases/nnbd/issue43256.dart
new file mode 100644
index 0000000..5c72c9e
--- /dev/null
+++ b/pkg/front_end/testcases/nnbd/issue43256.dart
@@ -0,0 +1,59 @@
+// Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+var i = 1;
+
+Map<int, String>? nullableMap = {1: "Let", 2: "it", 3: "be"};
+
+List<int>? nullableList = [1, 2, 3];
+
+dynamic dynamicMap = {1: "Let", 2: "it", 3: "be"};
+
+dynamic dynamicList = [1, 2, 3];
+
+var map1 = {
+  if (i > 0) ...nullableMap, // error
+  if (i > 0) ...dynamicMap, // ok
+  if (i > 0) ...nullableMap!, // ok
+};
+
+var set1 = {
+  0,
+  if (i > 0) ...nullableList, // error
+  if (i > 0) ...dynamicList, // ok
+  if (i > 0) ...nullableList! // ok
+};
+
+var list1 = [
+  if (i > 0) ...nullableList, // error
+  if (i > 0) ...dynamicList, // ok
+  if (i > 0) ...nullableList!, // ok
+];
+
+testMap<X extends dynamic, Y extends Map<int, String>?,
+    Z extends Map<int, String>>(X x, Y y, Z z) {
+  var map2 = {
+    if (i > 0) ...x, // error
+    if (i > 0) ...y, // error
+    if (i > 0) ...z, // ok
+    if (i > 0) ...y!, // ok
+  };
+}
+
+testIterables<X extends dynamic, Y extends List<int>?, Z extends List<int>>(
+    X x, Y y, Z z) {
+  var set2 = {
+    0,
+    if (i > 0) ...x, // error
+    if (i > 0) ...y, // error
+    if (i > 0) ...z, // ok
+  };
+  var list2 = [
+    if (i > 0) ...x, // error
+    if (i > 0) ...y, // error
+    if (i > 0) ...z, // ok
+  ];
+}
+
+main() {}
diff --git a/pkg/front_end/testcases/nnbd/issue43256.dart.outline.expect b/pkg/front_end/testcases/nnbd/issue43256.dart.outline.expect
new file mode 100644
index 0000000..d008a19
--- /dev/null
+++ b/pkg/front_end/testcases/nnbd/issue43256.dart.outline.expect
@@ -0,0 +1,18 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+import "dart:core" as core;
+
+static field core::int i;
+static field core::Map<core::int, core::String>? nullableMap;
+static field core::List<core::int>? nullableList;
+static field dynamic dynamicMap;
+static field dynamic dynamicList;
+static field core::Map<dynamic, dynamic> map1;
+static field core::Set<dynamic> set1;
+static field core::List<dynamic> list1;
+static method testMap<X extends dynamic = dynamic, Y extends core::Map<core::int, core::String>? = core::Map<core::int, core::String>?, Z extends core::Map<core::int, core::String> = core::Map<core::int, core::String>>(self::testMap::X% x, self::testMap::Y% y, self::testMap::Z z) → dynamic
+  ;
+static method testIterables<X extends dynamic = dynamic, Y extends core::List<core::int>? = core::List<core::int>?, Z extends core::List<core::int> = core::List<core::int>>(self::testIterables::X% x, self::testIterables::Y% y, self::testIterables::Z z) → dynamic
+  ;
+static method main() → dynamic
+  ;
diff --git a/pkg/front_end/testcases/nnbd/issue43256.dart.strong.expect b/pkg/front_end/testcases/nnbd/issue43256.dart.strong.expect
new file mode 100644
index 0000000..0d7d725
--- /dev/null
+++ b/pkg/front_end/testcases/nnbd/issue43256.dart.strong.expect
@@ -0,0 +1,140 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:16:17: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+//   if (i > 0) ...nullableMap, // error
+//                 ^
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:23:17: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+//   if (i > 0) ...nullableList, // error
+//                 ^
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:29:17: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+//   if (i > 0) ...nullableList, // error
+//                 ^
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:37:19: Error: Unexpected type 'X' of a map spread entry.  Expected 'dynamic' or a Map.
+//     if (i > 0) ...x, // error
+//                   ^
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:38:19: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+//     if (i > 0) ...y, // error
+//                   ^
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:48:19: Error: Unexpected type 'X' of a spread.  Expected 'dynamic' or an Iterable.
+//     if (i > 0) ...x, // error
+//                   ^
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:49:19: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+//     if (i > 0) ...y, // error
+//                   ^
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:53:19: Error: Unexpected type 'X' of a spread.  Expected 'dynamic' or an Iterable.
+//     if (i > 0) ...x, // error
+//                   ^
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:54:19: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+//     if (i > 0) ...y, // error
+//                   ^
+//
+import self as self;
+import "dart:core" as core;
+import "dart:collection" as col;
+
+static field core::int i = 1;
+static field core::Map<core::int, core::String>? nullableMap = <core::int, core::String>{1: "Let", 2: "it", 3: "be"};
+static field core::List<core::int>? nullableList = <core::int>[1, 2, 3];
+static field dynamic dynamicMap = <core::int, core::String>{1: "Let", 2: "it", 3: "be"};
+static field dynamic dynamicList = <core::int>[1, 2, 3];
+static field core::Map<dynamic, dynamic> map1 = block {
+  final core::Map<dynamic, dynamic> #t1 = <dynamic, dynamic>{};
+  if(self::i.{core::num::>}(0))
+    #t1.{core::Map::[]=}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:16:17: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+  if (i > 0) ...nullableMap, // error
+                ^", null);
+  if(self::i.{core::num::>}(0))
+    for (final core::MapEntry<dynamic, dynamic> #t2 in (self::dynamicMap as{TypeError,ForDynamic,ForNonNullableByDefault} core::Map<dynamic, dynamic>).{core::Map::entries})
+      #t1.{core::Map::[]=}(#t2.{core::MapEntry::key}, #t2.{core::MapEntry::value});
+  if(self::i.{core::num::>}(0))
+    for (final core::MapEntry<dynamic, dynamic> #t3 in self::nullableMap!.{core::Map::entries})
+      #t1.{core::Map::[]=}(#t3.{core::MapEntry::key}, #t3.{core::MapEntry::value});
+} =>#t1;
+static field core::Set<dynamic> set1 = block {
+  final core::Set<dynamic> #t4 = col::LinkedHashSet::•<dynamic>();
+  #t4.{core::Set::add}(0);
+  if(self::i.{core::num::>}(0))
+    #t4.{core::Set::add}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:23:17: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+  if (i > 0) ...nullableList, // error
+                ^");
+  if(self::i.{core::num::>}(0))
+    for (final dynamic #t5 in self::dynamicList as{TypeError,ForDynamic,ForNonNullableByDefault} core::Iterable<dynamic>)
+      #t4.{core::Set::add}(#t5);
+  if(self::i.{core::num::>}(0))
+    for (final dynamic #t6 in self::nullableList!)
+      #t4.{core::Set::add}(#t6);
+} =>#t4;
+static field core::List<dynamic> list1 = block {
+  final core::List<dynamic> #t7 = <dynamic>[];
+  if(self::i.{core::num::>}(0))
+    #t7.{core::List::add}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:29:17: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+  if (i > 0) ...nullableList, // error
+                ^");
+  if(self::i.{core::num::>}(0))
+    for (final dynamic #t8 in self::dynamicList as{TypeError,ForDynamic,ForNonNullableByDefault} core::Iterable<dynamic>)
+      #t7.{core::List::add}(#t8);
+  if(self::i.{core::num::>}(0))
+    for (final dynamic #t9 in self::nullableList!)
+      #t7.{core::List::add}(#t9);
+} =>#t7;
+static method testMap<X extends dynamic = dynamic, Y extends core::Map<core::int, core::String>? = core::Map<core::int, core::String>?, Z extends core::Map<core::int, core::String> = core::Map<core::int, core::String>>(self::testMap::X% x, self::testMap::Y% y, self::testMap::Z z) → dynamic {
+  core::Map<dynamic, dynamic> map2 = block {
+    final core::Map<dynamic, dynamic> #t10 = <dynamic, dynamic>{};
+    if(self::i.{core::num::>}(0))
+      #t10.{core::Map::[]=}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:37:19: Error: Unexpected type 'X' of a map spread entry.  Expected 'dynamic' or a Map.
+    if (i > 0) ...x, // error
+                  ^", null);
+    if(self::i.{core::num::>}(0))
+      #t10.{core::Map::[]=}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:38:19: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+    if (i > 0) ...y, // error
+                  ^", null);
+    if(self::i.{core::num::>}(0))
+      for (final core::MapEntry<dynamic, dynamic> #t11 in z.{core::Map::entries})
+        #t10.{core::Map::[]=}(#t11.{core::MapEntry::key}, #t11.{core::MapEntry::value});
+    if(self::i.{core::num::>}(0))
+      for (final core::MapEntry<dynamic, dynamic> #t12 in y!.{core::Map::entries})
+        #t10.{core::Map::[]=}(#t12.{core::MapEntry::key}, #t12.{core::MapEntry::value});
+  } =>#t10;
+}
+static method testIterables<X extends dynamic = dynamic, Y extends core::List<core::int>? = core::List<core::int>?, Z extends core::List<core::int> = core::List<core::int>>(self::testIterables::X% x, self::testIterables::Y% y, self::testIterables::Z z) → dynamic {
+  core::Set<dynamic> set2 = block {
+    final core::Set<dynamic> #t13 = col::LinkedHashSet::•<dynamic>();
+    #t13.{core::Set::add}(0);
+    if(self::i.{core::num::>}(0))
+      #t13.{core::Set::add}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:48:19: Error: Unexpected type 'X' of a spread.  Expected 'dynamic' or an Iterable.
+    if (i > 0) ...x, // error
+                  ^");
+    if(self::i.{core::num::>}(0))
+      #t13.{core::Set::add}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:49:19: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+    if (i > 0) ...y, // error
+                  ^");
+    if(self::i.{core::num::>}(0))
+      for (final dynamic #t14 in z)
+        #t13.{core::Set::add}(#t14);
+  } =>#t13;
+  core::List<dynamic> list2 = block {
+    final core::List<dynamic> #t15 = <dynamic>[];
+    if(self::i.{core::num::>}(0))
+      #t15.{core::List::add}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:53:19: Error: Unexpected type 'X' of a spread.  Expected 'dynamic' or an Iterable.
+    if (i > 0) ...x, // error
+                  ^");
+    if(self::i.{core::num::>}(0))
+      #t15.{core::List::add}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:54:19: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+    if (i > 0) ...y, // error
+                  ^");
+    if(self::i.{core::num::>}(0))
+      for (final dynamic #t16 in z)
+        #t15.{core::List::add}(#t16);
+  } =>#t15;
+}
+static method main() → dynamic {}
diff --git a/pkg/front_end/testcases/nnbd/issue43256.dart.strong.transformed.expect b/pkg/front_end/testcases/nnbd/issue43256.dart.strong.transformed.expect
new file mode 100644
index 0000000..ef9e80c
--- /dev/null
+++ b/pkg/front_end/testcases/nnbd/issue43256.dart.strong.transformed.expect
@@ -0,0 +1,180 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:16:17: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+//   if (i > 0) ...nullableMap, // error
+//                 ^
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:23:17: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+//   if (i > 0) ...nullableList, // error
+//                 ^
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:29:17: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+//   if (i > 0) ...nullableList, // error
+//                 ^
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:37:19: Error: Unexpected type 'X' of a map spread entry.  Expected 'dynamic' or a Map.
+//     if (i > 0) ...x, // error
+//                   ^
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:38:19: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+//     if (i > 0) ...y, // error
+//                   ^
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:48:19: Error: Unexpected type 'X' of a spread.  Expected 'dynamic' or an Iterable.
+//     if (i > 0) ...x, // error
+//                   ^
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:49:19: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+//     if (i > 0) ...y, // error
+//                   ^
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:53:19: Error: Unexpected type 'X' of a spread.  Expected 'dynamic' or an Iterable.
+//     if (i > 0) ...x, // error
+//                   ^
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:54:19: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+//     if (i > 0) ...y, // error
+//                   ^
+//
+import self as self;
+import "dart:core" as core;
+import "dart:collection" as col;
+
+static field core::int i = 1;
+static field core::Map<core::int, core::String>? nullableMap = <core::int, core::String>{1: "Let", 2: "it", 3: "be"};
+static field core::List<core::int>? nullableList = <core::int>[1, 2, 3];
+static field dynamic dynamicMap = <core::int, core::String>{1: "Let", 2: "it", 3: "be"};
+static field dynamic dynamicList = <core::int>[1, 2, 3];
+static field core::Map<dynamic, dynamic> map1 = block {
+  final core::Map<dynamic, dynamic> #t1 = <dynamic, dynamic>{};
+  if(self::i.{core::num::>}(0))
+    #t1.{core::Map::[]=}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:16:17: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+  if (i > 0) ...nullableMap, // error
+                ^", null);
+  if(self::i.{core::num::>}(0)) {
+    core::Iterator<core::MapEntry<dynamic, dynamic>> :sync-for-iterator = (self::dynamicMap as{TypeError,ForDynamic,ForNonNullableByDefault} core::Map<dynamic, dynamic>).{core::Map::entries}.{core::Iterable::iterator};
+    for (; :sync-for-iterator.{core::Iterator::moveNext}(); ) {
+      final core::MapEntry<dynamic, dynamic> #t2 = :sync-for-iterator.{core::Iterator::current};
+      #t1.{core::Map::[]=}(#t2.{core::MapEntry::key}, #t2.{core::MapEntry::value});
+    }
+  }
+  if(self::i.{core::num::>}(0)) {
+    core::Iterator<core::MapEntry<core::int, core::String>> :sync-for-iterator = self::nullableMap!.{core::Map::entries}.{core::Iterable::iterator};
+    for (; :sync-for-iterator.{core::Iterator::moveNext}(); ) {
+      final core::MapEntry<dynamic, dynamic> #t3 = :sync-for-iterator.{core::Iterator::current};
+      #t1.{core::Map::[]=}(#t3.{core::MapEntry::key}, #t3.{core::MapEntry::value});
+    }
+  }
+} =>#t1;
+static field core::Set<dynamic> set1 = block {
+  final core::Set<dynamic> #t4 = new col::_CompactLinkedHashSet::•<dynamic>();
+  #t4.{core::Set::add}(0);
+  if(self::i.{core::num::>}(0))
+    #t4.{core::Set::add}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:23:17: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+  if (i > 0) ...nullableList, // error
+                ^");
+  if(self::i.{core::num::>}(0)) {
+    core::Iterator<dynamic> :sync-for-iterator = (self::dynamicList as{TypeError,ForDynamic,ForNonNullableByDefault} core::Iterable<dynamic>).{core::Iterable::iterator};
+    for (; :sync-for-iterator.{core::Iterator::moveNext}(); ) {
+      final dynamic #t5 = :sync-for-iterator.{core::Iterator::current};
+      #t4.{core::Set::add}(#t5);
+    }
+  }
+  if(self::i.{core::num::>}(0)) {
+    core::Iterator<core::int> :sync-for-iterator = self::nullableList!.{core::Iterable::iterator};
+    for (; :sync-for-iterator.{core::Iterator::moveNext}(); ) {
+      final dynamic #t6 = :sync-for-iterator.{core::Iterator::current};
+      #t4.{core::Set::add}(#t6);
+    }
+  }
+} =>#t4;
+static field core::List<dynamic> list1 = block {
+  final core::List<dynamic> #t7 = <dynamic>[];
+  if(self::i.{core::num::>}(0))
+    #t7.{core::List::add}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:29:17: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+  if (i > 0) ...nullableList, // error
+                ^");
+  if(self::i.{core::num::>}(0)) {
+    core::Iterator<dynamic> :sync-for-iterator = (self::dynamicList as{TypeError,ForDynamic,ForNonNullableByDefault} core::Iterable<dynamic>).{core::Iterable::iterator};
+    for (; :sync-for-iterator.{core::Iterator::moveNext}(); ) {
+      final dynamic #t8 = :sync-for-iterator.{core::Iterator::current};
+      #t7.{core::List::add}(#t8);
+    }
+  }
+  if(self::i.{core::num::>}(0)) {
+    core::Iterator<core::int> :sync-for-iterator = self::nullableList!.{core::Iterable::iterator};
+    for (; :sync-for-iterator.{core::Iterator::moveNext}(); ) {
+      final dynamic #t9 = :sync-for-iterator.{core::Iterator::current};
+      #t7.{core::List::add}(#t9);
+    }
+  }
+} =>#t7;
+static method testMap<X extends dynamic = dynamic, Y extends core::Map<core::int, core::String>? = core::Map<core::int, core::String>?, Z extends core::Map<core::int, core::String> = core::Map<core::int, core::String>>(self::testMap::X% x, self::testMap::Y% y, self::testMap::Z z) → dynamic {
+  core::Map<dynamic, dynamic> map2 = block {
+    final core::Map<dynamic, dynamic> #t10 = <dynamic, dynamic>{};
+    if(self::i.{core::num::>}(0))
+      #t10.{core::Map::[]=}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:37:19: Error: Unexpected type 'X' of a map spread entry.  Expected 'dynamic' or a Map.
+    if (i > 0) ...x, // error
+                  ^", null);
+    if(self::i.{core::num::>}(0))
+      #t10.{core::Map::[]=}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:38:19: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+    if (i > 0) ...y, // error
+                  ^", null);
+    if(self::i.{core::num::>}(0)) {
+      core::Iterator<core::MapEntry<core::int, core::String>> :sync-for-iterator = z.{core::Map::entries}.{core::Iterable::iterator};
+      for (; :sync-for-iterator.{core::Iterator::moveNext}(); ) {
+        final core::MapEntry<dynamic, dynamic> #t11 = :sync-for-iterator.{core::Iterator::current};
+        #t10.{core::Map::[]=}(#t11.{core::MapEntry::key}, #t11.{core::MapEntry::value});
+      }
+    }
+    if(self::i.{core::num::>}(0)) {
+      core::Iterator<core::MapEntry<core::int, core::String>> :sync-for-iterator = y!.{core::Map::entries}.{core::Iterable::iterator};
+      for (; :sync-for-iterator.{core::Iterator::moveNext}(); ) {
+        final core::MapEntry<dynamic, dynamic> #t12 = :sync-for-iterator.{core::Iterator::current};
+        #t10.{core::Map::[]=}(#t12.{core::MapEntry::key}, #t12.{core::MapEntry::value});
+      }
+    }
+  } =>#t10;
+}
+static method testIterables<X extends dynamic = dynamic, Y extends core::List<core::int>? = core::List<core::int>?, Z extends core::List<core::int> = core::List<core::int>>(self::testIterables::X% x, self::testIterables::Y% y, self::testIterables::Z z) → dynamic {
+  core::Set<dynamic> set2 = block {
+    final core::Set<dynamic> #t13 = new col::_CompactLinkedHashSet::•<dynamic>();
+    #t13.{core::Set::add}(0);
+    if(self::i.{core::num::>}(0))
+      #t13.{core::Set::add}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:48:19: Error: Unexpected type 'X' of a spread.  Expected 'dynamic' or an Iterable.
+    if (i > 0) ...x, // error
+                  ^");
+    if(self::i.{core::num::>}(0))
+      #t13.{core::Set::add}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:49:19: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+    if (i > 0) ...y, // error
+                  ^");
+    if(self::i.{core::num::>}(0)) {
+      core::Iterator<core::int> :sync-for-iterator = z.{core::Iterable::iterator};
+      for (; :sync-for-iterator.{core::Iterator::moveNext}(); ) {
+        final dynamic #t14 = :sync-for-iterator.{core::Iterator::current};
+        #t13.{core::Set::add}(#t14);
+      }
+    }
+  } =>#t13;
+  core::List<dynamic> list2 = block {
+    final core::List<dynamic> #t15 = <dynamic>[];
+    if(self::i.{core::num::>}(0))
+      #t15.{core::List::add}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:53:19: Error: Unexpected type 'X' of a spread.  Expected 'dynamic' or an Iterable.
+    if (i > 0) ...x, // error
+                  ^");
+    if(self::i.{core::num::>}(0))
+      #t15.{core::List::add}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:54:19: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+    if (i > 0) ...y, // error
+                  ^");
+    if(self::i.{core::num::>}(0)) {
+      core::Iterator<core::int> :sync-for-iterator = z.{core::Iterable::iterator};
+      for (; :sync-for-iterator.{core::Iterator::moveNext}(); ) {
+        final dynamic #t16 = :sync-for-iterator.{core::Iterator::current};
+        #t15.{core::List::add}(#t16);
+      }
+    }
+  } =>#t15;
+}
+static method main() → dynamic {}
diff --git a/pkg/front_end/testcases/nnbd/issue43256.dart.textual_outline.expect b/pkg/front_end/testcases/nnbd/issue43256.dart.textual_outline.expect
new file mode 100644
index 0000000..8fbb6e9
--- /dev/null
+++ b/pkg/front_end/testcases/nnbd/issue43256.dart.textual_outline.expect
@@ -0,0 +1,26 @@
+var i = 1;
+Map<int, String>? nullableMap = {1: "Let", 2: "it", 3: "be"};
+List<int>? nullableList = [1, 2, 3];
+dynamic dynamicMap = {1: "Let", 2: "it", 3: "be"};
+dynamic dynamicList = [1, 2, 3];
+var map1 = {
+  if (i > 0) ...nullableMap,
+  if (i > 0) ...dynamicMap,
+  if (i > 0) ...nullableMap!,
+};
+var set1 = {
+  0,
+  if (i > 0) ...nullableList,
+  if (i > 0) ...dynamicList,
+  if (i > 0) ...nullableList!
+};
+var list1 = [
+  if (i > 0) ...nullableList,
+  if (i > 0) ...dynamicList,
+  if (i > 0) ...nullableList!,
+];
+testMap<X extends dynamic, Y extends Map<int, String>?,
+    Z extends Map<int, String>>(X x, Y y, Z z) {}
+testIterables<X extends dynamic, Y extends List<int>?, Z extends List<int>>(
+    X x, Y y, Z z) {}
+main() {}
diff --git a/pkg/front_end/testcases/nnbd/issue43256.dart.textual_outline_modelled.expect b/pkg/front_end/testcases/nnbd/issue43256.dart.textual_outline_modelled.expect
new file mode 100644
index 0000000..51913c7
--- /dev/null
+++ b/pkg/front_end/testcases/nnbd/issue43256.dart.textual_outline_modelled.expect
@@ -0,0 +1,26 @@
+List<int>? nullableList = [1, 2, 3];
+Map<int, String>? nullableMap = {1: "Let", 2: "it", 3: "be"};
+dynamic dynamicList = [1, 2, 3];
+dynamic dynamicMap = {1: "Let", 2: "it", 3: "be"};
+main() {}
+testIterables<X extends dynamic, Y extends List<int>?, Z extends List<int>>(
+    X x, Y y, Z z) {}
+testMap<X extends dynamic, Y extends Map<int, String>?,
+    Z extends Map<int, String>>(X x, Y y, Z z) {}
+var i = 1;
+var list1 = [
+  if (i > 0) ...nullableList,
+  if (i > 0) ...dynamicList,
+  if (i > 0) ...nullableList!,
+];
+var map1 = {
+  if (i > 0) ...nullableMap,
+  if (i > 0) ...dynamicMap,
+  if (i > 0) ...nullableMap!,
+};
+var set1 = {
+  0,
+  if (i > 0) ...nullableList,
+  if (i > 0) ...dynamicList,
+  if (i > 0) ...nullableList!
+};
diff --git a/pkg/front_end/testcases/nnbd/issue43256.dart.weak.expect b/pkg/front_end/testcases/nnbd/issue43256.dart.weak.expect
new file mode 100644
index 0000000..0d7d725
--- /dev/null
+++ b/pkg/front_end/testcases/nnbd/issue43256.dart.weak.expect
@@ -0,0 +1,140 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:16:17: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+//   if (i > 0) ...nullableMap, // error
+//                 ^
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:23:17: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+//   if (i > 0) ...nullableList, // error
+//                 ^
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:29:17: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+//   if (i > 0) ...nullableList, // error
+//                 ^
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:37:19: Error: Unexpected type 'X' of a map spread entry.  Expected 'dynamic' or a Map.
+//     if (i > 0) ...x, // error
+//                   ^
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:38:19: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+//     if (i > 0) ...y, // error
+//                   ^
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:48:19: Error: Unexpected type 'X' of a spread.  Expected 'dynamic' or an Iterable.
+//     if (i > 0) ...x, // error
+//                   ^
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:49:19: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+//     if (i > 0) ...y, // error
+//                   ^
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:53:19: Error: Unexpected type 'X' of a spread.  Expected 'dynamic' or an Iterable.
+//     if (i > 0) ...x, // error
+//                   ^
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:54:19: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+//     if (i > 0) ...y, // error
+//                   ^
+//
+import self as self;
+import "dart:core" as core;
+import "dart:collection" as col;
+
+static field core::int i = 1;
+static field core::Map<core::int, core::String>? nullableMap = <core::int, core::String>{1: "Let", 2: "it", 3: "be"};
+static field core::List<core::int>? nullableList = <core::int>[1, 2, 3];
+static field dynamic dynamicMap = <core::int, core::String>{1: "Let", 2: "it", 3: "be"};
+static field dynamic dynamicList = <core::int>[1, 2, 3];
+static field core::Map<dynamic, dynamic> map1 = block {
+  final core::Map<dynamic, dynamic> #t1 = <dynamic, dynamic>{};
+  if(self::i.{core::num::>}(0))
+    #t1.{core::Map::[]=}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:16:17: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+  if (i > 0) ...nullableMap, // error
+                ^", null);
+  if(self::i.{core::num::>}(0))
+    for (final core::MapEntry<dynamic, dynamic> #t2 in (self::dynamicMap as{TypeError,ForDynamic,ForNonNullableByDefault} core::Map<dynamic, dynamic>).{core::Map::entries})
+      #t1.{core::Map::[]=}(#t2.{core::MapEntry::key}, #t2.{core::MapEntry::value});
+  if(self::i.{core::num::>}(0))
+    for (final core::MapEntry<dynamic, dynamic> #t3 in self::nullableMap!.{core::Map::entries})
+      #t1.{core::Map::[]=}(#t3.{core::MapEntry::key}, #t3.{core::MapEntry::value});
+} =>#t1;
+static field core::Set<dynamic> set1 = block {
+  final core::Set<dynamic> #t4 = col::LinkedHashSet::•<dynamic>();
+  #t4.{core::Set::add}(0);
+  if(self::i.{core::num::>}(0))
+    #t4.{core::Set::add}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:23:17: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+  if (i > 0) ...nullableList, // error
+                ^");
+  if(self::i.{core::num::>}(0))
+    for (final dynamic #t5 in self::dynamicList as{TypeError,ForDynamic,ForNonNullableByDefault} core::Iterable<dynamic>)
+      #t4.{core::Set::add}(#t5);
+  if(self::i.{core::num::>}(0))
+    for (final dynamic #t6 in self::nullableList!)
+      #t4.{core::Set::add}(#t6);
+} =>#t4;
+static field core::List<dynamic> list1 = block {
+  final core::List<dynamic> #t7 = <dynamic>[];
+  if(self::i.{core::num::>}(0))
+    #t7.{core::List::add}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:29:17: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+  if (i > 0) ...nullableList, // error
+                ^");
+  if(self::i.{core::num::>}(0))
+    for (final dynamic #t8 in self::dynamicList as{TypeError,ForDynamic,ForNonNullableByDefault} core::Iterable<dynamic>)
+      #t7.{core::List::add}(#t8);
+  if(self::i.{core::num::>}(0))
+    for (final dynamic #t9 in self::nullableList!)
+      #t7.{core::List::add}(#t9);
+} =>#t7;
+static method testMap<X extends dynamic = dynamic, Y extends core::Map<core::int, core::String>? = core::Map<core::int, core::String>?, Z extends core::Map<core::int, core::String> = core::Map<core::int, core::String>>(self::testMap::X% x, self::testMap::Y% y, self::testMap::Z z) → dynamic {
+  core::Map<dynamic, dynamic> map2 = block {
+    final core::Map<dynamic, dynamic> #t10 = <dynamic, dynamic>{};
+    if(self::i.{core::num::>}(0))
+      #t10.{core::Map::[]=}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:37:19: Error: Unexpected type 'X' of a map spread entry.  Expected 'dynamic' or a Map.
+    if (i > 0) ...x, // error
+                  ^", null);
+    if(self::i.{core::num::>}(0))
+      #t10.{core::Map::[]=}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:38:19: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+    if (i > 0) ...y, // error
+                  ^", null);
+    if(self::i.{core::num::>}(0))
+      for (final core::MapEntry<dynamic, dynamic> #t11 in z.{core::Map::entries})
+        #t10.{core::Map::[]=}(#t11.{core::MapEntry::key}, #t11.{core::MapEntry::value});
+    if(self::i.{core::num::>}(0))
+      for (final core::MapEntry<dynamic, dynamic> #t12 in y!.{core::Map::entries})
+        #t10.{core::Map::[]=}(#t12.{core::MapEntry::key}, #t12.{core::MapEntry::value});
+  } =>#t10;
+}
+static method testIterables<X extends dynamic = dynamic, Y extends core::List<core::int>? = core::List<core::int>?, Z extends core::List<core::int> = core::List<core::int>>(self::testIterables::X% x, self::testIterables::Y% y, self::testIterables::Z z) → dynamic {
+  core::Set<dynamic> set2 = block {
+    final core::Set<dynamic> #t13 = col::LinkedHashSet::•<dynamic>();
+    #t13.{core::Set::add}(0);
+    if(self::i.{core::num::>}(0))
+      #t13.{core::Set::add}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:48:19: Error: Unexpected type 'X' of a spread.  Expected 'dynamic' or an Iterable.
+    if (i > 0) ...x, // error
+                  ^");
+    if(self::i.{core::num::>}(0))
+      #t13.{core::Set::add}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:49:19: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+    if (i > 0) ...y, // error
+                  ^");
+    if(self::i.{core::num::>}(0))
+      for (final dynamic #t14 in z)
+        #t13.{core::Set::add}(#t14);
+  } =>#t13;
+  core::List<dynamic> list2 = block {
+    final core::List<dynamic> #t15 = <dynamic>[];
+    if(self::i.{core::num::>}(0))
+      #t15.{core::List::add}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:53:19: Error: Unexpected type 'X' of a spread.  Expected 'dynamic' or an Iterable.
+    if (i > 0) ...x, // error
+                  ^");
+    if(self::i.{core::num::>}(0))
+      #t15.{core::List::add}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:54:19: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+    if (i > 0) ...y, // error
+                  ^");
+    if(self::i.{core::num::>}(0))
+      for (final dynamic #t16 in z)
+        #t15.{core::List::add}(#t16);
+  } =>#t15;
+}
+static method main() → dynamic {}
diff --git a/pkg/front_end/testcases/nnbd/issue43256.dart.weak.transformed.expect b/pkg/front_end/testcases/nnbd/issue43256.dart.weak.transformed.expect
new file mode 100644
index 0000000..ef9e80c
--- /dev/null
+++ b/pkg/front_end/testcases/nnbd/issue43256.dart.weak.transformed.expect
@@ -0,0 +1,180 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:16:17: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+//   if (i > 0) ...nullableMap, // error
+//                 ^
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:23:17: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+//   if (i > 0) ...nullableList, // error
+//                 ^
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:29:17: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+//   if (i > 0) ...nullableList, // error
+//                 ^
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:37:19: Error: Unexpected type 'X' of a map spread entry.  Expected 'dynamic' or a Map.
+//     if (i > 0) ...x, // error
+//                   ^
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:38:19: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+//     if (i > 0) ...y, // error
+//                   ^
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:48:19: Error: Unexpected type 'X' of a spread.  Expected 'dynamic' or an Iterable.
+//     if (i > 0) ...x, // error
+//                   ^
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:49:19: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+//     if (i > 0) ...y, // error
+//                   ^
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:53:19: Error: Unexpected type 'X' of a spread.  Expected 'dynamic' or an Iterable.
+//     if (i > 0) ...x, // error
+//                   ^
+//
+// pkg/front_end/testcases/nnbd/issue43256.dart:54:19: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+//     if (i > 0) ...y, // error
+//                   ^
+//
+import self as self;
+import "dart:core" as core;
+import "dart:collection" as col;
+
+static field core::int i = 1;
+static field core::Map<core::int, core::String>? nullableMap = <core::int, core::String>{1: "Let", 2: "it", 3: "be"};
+static field core::List<core::int>? nullableList = <core::int>[1, 2, 3];
+static field dynamic dynamicMap = <core::int, core::String>{1: "Let", 2: "it", 3: "be"};
+static field dynamic dynamicList = <core::int>[1, 2, 3];
+static field core::Map<dynamic, dynamic> map1 = block {
+  final core::Map<dynamic, dynamic> #t1 = <dynamic, dynamic>{};
+  if(self::i.{core::num::>}(0))
+    #t1.{core::Map::[]=}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:16:17: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+  if (i > 0) ...nullableMap, // error
+                ^", null);
+  if(self::i.{core::num::>}(0)) {
+    core::Iterator<core::MapEntry<dynamic, dynamic>> :sync-for-iterator = (self::dynamicMap as{TypeError,ForDynamic,ForNonNullableByDefault} core::Map<dynamic, dynamic>).{core::Map::entries}.{core::Iterable::iterator};
+    for (; :sync-for-iterator.{core::Iterator::moveNext}(); ) {
+      final core::MapEntry<dynamic, dynamic> #t2 = :sync-for-iterator.{core::Iterator::current};
+      #t1.{core::Map::[]=}(#t2.{core::MapEntry::key}, #t2.{core::MapEntry::value});
+    }
+  }
+  if(self::i.{core::num::>}(0)) {
+    core::Iterator<core::MapEntry<core::int, core::String>> :sync-for-iterator = self::nullableMap!.{core::Map::entries}.{core::Iterable::iterator};
+    for (; :sync-for-iterator.{core::Iterator::moveNext}(); ) {
+      final core::MapEntry<dynamic, dynamic> #t3 = :sync-for-iterator.{core::Iterator::current};
+      #t1.{core::Map::[]=}(#t3.{core::MapEntry::key}, #t3.{core::MapEntry::value});
+    }
+  }
+} =>#t1;
+static field core::Set<dynamic> set1 = block {
+  final core::Set<dynamic> #t4 = new col::_CompactLinkedHashSet::•<dynamic>();
+  #t4.{core::Set::add}(0);
+  if(self::i.{core::num::>}(0))
+    #t4.{core::Set::add}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:23:17: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+  if (i > 0) ...nullableList, // error
+                ^");
+  if(self::i.{core::num::>}(0)) {
+    core::Iterator<dynamic> :sync-for-iterator = (self::dynamicList as{TypeError,ForDynamic,ForNonNullableByDefault} core::Iterable<dynamic>).{core::Iterable::iterator};
+    for (; :sync-for-iterator.{core::Iterator::moveNext}(); ) {
+      final dynamic #t5 = :sync-for-iterator.{core::Iterator::current};
+      #t4.{core::Set::add}(#t5);
+    }
+  }
+  if(self::i.{core::num::>}(0)) {
+    core::Iterator<core::int> :sync-for-iterator = self::nullableList!.{core::Iterable::iterator};
+    for (; :sync-for-iterator.{core::Iterator::moveNext}(); ) {
+      final dynamic #t6 = :sync-for-iterator.{core::Iterator::current};
+      #t4.{core::Set::add}(#t6);
+    }
+  }
+} =>#t4;
+static field core::List<dynamic> list1 = block {
+  final core::List<dynamic> #t7 = <dynamic>[];
+  if(self::i.{core::num::>}(0))
+    #t7.{core::List::add}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:29:17: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+  if (i > 0) ...nullableList, // error
+                ^");
+  if(self::i.{core::num::>}(0)) {
+    core::Iterator<dynamic> :sync-for-iterator = (self::dynamicList as{TypeError,ForDynamic,ForNonNullableByDefault} core::Iterable<dynamic>).{core::Iterable::iterator};
+    for (; :sync-for-iterator.{core::Iterator::moveNext}(); ) {
+      final dynamic #t8 = :sync-for-iterator.{core::Iterator::current};
+      #t7.{core::List::add}(#t8);
+    }
+  }
+  if(self::i.{core::num::>}(0)) {
+    core::Iterator<core::int> :sync-for-iterator = self::nullableList!.{core::Iterable::iterator};
+    for (; :sync-for-iterator.{core::Iterator::moveNext}(); ) {
+      final dynamic #t9 = :sync-for-iterator.{core::Iterator::current};
+      #t7.{core::List::add}(#t9);
+    }
+  }
+} =>#t7;
+static method testMap<X extends dynamic = dynamic, Y extends core::Map<core::int, core::String>? = core::Map<core::int, core::String>?, Z extends core::Map<core::int, core::String> = core::Map<core::int, core::String>>(self::testMap::X% x, self::testMap::Y% y, self::testMap::Z z) → dynamic {
+  core::Map<dynamic, dynamic> map2 = block {
+    final core::Map<dynamic, dynamic> #t10 = <dynamic, dynamic>{};
+    if(self::i.{core::num::>}(0))
+      #t10.{core::Map::[]=}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:37:19: Error: Unexpected type 'X' of a map spread entry.  Expected 'dynamic' or a Map.
+    if (i > 0) ...x, // error
+                  ^", null);
+    if(self::i.{core::num::>}(0))
+      #t10.{core::Map::[]=}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:38:19: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+    if (i > 0) ...y, // error
+                  ^", null);
+    if(self::i.{core::num::>}(0)) {
+      core::Iterator<core::MapEntry<core::int, core::String>> :sync-for-iterator = z.{core::Map::entries}.{core::Iterable::iterator};
+      for (; :sync-for-iterator.{core::Iterator::moveNext}(); ) {
+        final core::MapEntry<dynamic, dynamic> #t11 = :sync-for-iterator.{core::Iterator::current};
+        #t10.{core::Map::[]=}(#t11.{core::MapEntry::key}, #t11.{core::MapEntry::value});
+      }
+    }
+    if(self::i.{core::num::>}(0)) {
+      core::Iterator<core::MapEntry<core::int, core::String>> :sync-for-iterator = y!.{core::Map::entries}.{core::Iterable::iterator};
+      for (; :sync-for-iterator.{core::Iterator::moveNext}(); ) {
+        final core::MapEntry<dynamic, dynamic> #t12 = :sync-for-iterator.{core::Iterator::current};
+        #t10.{core::Map::[]=}(#t12.{core::MapEntry::key}, #t12.{core::MapEntry::value});
+      }
+    }
+  } =>#t10;
+}
+static method testIterables<X extends dynamic = dynamic, Y extends core::List<core::int>? = core::List<core::int>?, Z extends core::List<core::int> = core::List<core::int>>(self::testIterables::X% x, self::testIterables::Y% y, self::testIterables::Z z) → dynamic {
+  core::Set<dynamic> set2 = block {
+    final core::Set<dynamic> #t13 = new col::_CompactLinkedHashSet::•<dynamic>();
+    #t13.{core::Set::add}(0);
+    if(self::i.{core::num::>}(0))
+      #t13.{core::Set::add}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:48:19: Error: Unexpected type 'X' of a spread.  Expected 'dynamic' or an Iterable.
+    if (i > 0) ...x, // error
+                  ^");
+    if(self::i.{core::num::>}(0))
+      #t13.{core::Set::add}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:49:19: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+    if (i > 0) ...y, // error
+                  ^");
+    if(self::i.{core::num::>}(0)) {
+      core::Iterator<core::int> :sync-for-iterator = z.{core::Iterable::iterator};
+      for (; :sync-for-iterator.{core::Iterator::moveNext}(); ) {
+        final dynamic #t14 = :sync-for-iterator.{core::Iterator::current};
+        #t13.{core::Set::add}(#t14);
+      }
+    }
+  } =>#t13;
+  core::List<dynamic> list2 = block {
+    final core::List<dynamic> #t15 = <dynamic>[];
+    if(self::i.{core::num::>}(0))
+      #t15.{core::List::add}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:53:19: Error: Unexpected type 'X' of a spread.  Expected 'dynamic' or an Iterable.
+    if (i > 0) ...x, // error
+                  ^");
+    if(self::i.{core::num::>}(0))
+      #t15.{core::List::add}(invalid-expression "pkg/front_end/testcases/nnbd/issue43256.dart:54:19: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
+    if (i > 0) ...y, // error
+                  ^");
+    if(self::i.{core::num::>}(0)) {
+      core::Iterator<core::int> :sync-for-iterator = z.{core::Iterable::iterator};
+      for (; :sync-for-iterator.{core::Iterator::moveNext}(); ) {
+        final dynamic #t16 = :sync-for-iterator.{core::Iterator::current};
+        #t15.{core::List::add}(#t16);
+      }
+    }
+  } =>#t15;
+}
+static method main() → dynamic {}
diff --git a/pkg/front_end/testcases/rasta/super_initializer.dart.strong.expect b/pkg/front_end/testcases/rasta/super_initializer.dart.strong.expect
index 4ccdd4a..03f043f 100644
--- a/pkg/front_end/testcases/rasta/super_initializer.dart.strong.expect
+++ b/pkg/front_end/testcases/rasta/super_initializer.dart.strong.expect
@@ -2,16 +2,16 @@
 //
 // Problems in library:
 //
-// pkg/front_end/testcases/rasta/super_initializer.dart:14:15: Error: Can't have initializers after 'super'.
-//       : super.arg0(),
+// pkg/front_end/testcases/rasta/super_initializer.dart:15:15: Error: Can't have initializers after 'super'.
+//         field = 42;
 //               ^
 //
-// pkg/front_end/testcases/rasta/super_initializer.dart:17:15: Error: Can't have initializers after 'super'.
-//       : super.arg1(a),
+// pkg/front_end/testcases/rasta/super_initializer.dart:18:15: Error: Can't have initializers after 'super'.
+//         field = 42;
 //               ^
 //
-// pkg/front_end/testcases/rasta/super_initializer.dart:20:15: Error: Can't have initializers after 'super'.
-//       : super.arg2(a, b),
+// pkg/front_end/testcases/rasta/super_initializer.dart:21:15: Error: Can't have initializers after 'super'.
+//         field = 42;
 //               ^
 //
 import self as self;
@@ -41,18 +41,18 @@
 class Sub extends self::Super {
   field dynamic field;
   constructor arg0() → self::Sub*
-    : final dynamic #t1 = invalid-expression "pkg/front_end/testcases/rasta/super_initializer.dart:14:15: Error: Can't have initializers after 'super'.
-      : super.arg0(),
+    : final dynamic #t1 = invalid-expression "pkg/front_end/testcases/rasta/super_initializer.dart:15:15: Error: Can't have initializers after 'super'.
+        field = 42;
               ^", super self::Super::arg0()
     ;
   constructor arg1(dynamic a) → self::Sub*
-    : final dynamic #t2 = invalid-expression "pkg/front_end/testcases/rasta/super_initializer.dart:17:15: Error: Can't have initializers after 'super'.
-      : super.arg1(a),
+    : final dynamic #t2 = invalid-expression "pkg/front_end/testcases/rasta/super_initializer.dart:18:15: Error: Can't have initializers after 'super'.
+        field = 42;
               ^", super self::Super::arg1(a)
     ;
   constructor arg2(dynamic a, dynamic b) → self::Sub*
-    : final dynamic #t3 = invalid-expression "pkg/front_end/testcases/rasta/super_initializer.dart:20:15: Error: Can't have initializers after 'super'.
-      : super.arg2(a, b),
+    : final dynamic #t3 = invalid-expression "pkg/front_end/testcases/rasta/super_initializer.dart:21:15: Error: Can't have initializers after 'super'.
+        field = 42;
               ^", super self::Super::arg2(a, b)
     ;
 }
diff --git a/pkg/front_end/testcases/rasta/super_initializer.dart.strong.transformed.expect b/pkg/front_end/testcases/rasta/super_initializer.dart.strong.transformed.expect
index 4ccdd4a..03f043f 100644
--- a/pkg/front_end/testcases/rasta/super_initializer.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/rasta/super_initializer.dart.strong.transformed.expect
@@ -2,16 +2,16 @@
 //
 // Problems in library:
 //
-// pkg/front_end/testcases/rasta/super_initializer.dart:14:15: Error: Can't have initializers after 'super'.
-//       : super.arg0(),
+// pkg/front_end/testcases/rasta/super_initializer.dart:15:15: Error: Can't have initializers after 'super'.
+//         field = 42;
 //               ^
 //
-// pkg/front_end/testcases/rasta/super_initializer.dart:17:15: Error: Can't have initializers after 'super'.
-//       : super.arg1(a),
+// pkg/front_end/testcases/rasta/super_initializer.dart:18:15: Error: Can't have initializers after 'super'.
+//         field = 42;
 //               ^
 //
-// pkg/front_end/testcases/rasta/super_initializer.dart:20:15: Error: Can't have initializers after 'super'.
-//       : super.arg2(a, b),
+// pkg/front_end/testcases/rasta/super_initializer.dart:21:15: Error: Can't have initializers after 'super'.
+//         field = 42;
 //               ^
 //
 import self as self;
@@ -41,18 +41,18 @@
 class Sub extends self::Super {
   field dynamic field;
   constructor arg0() → self::Sub*
-    : final dynamic #t1 = invalid-expression "pkg/front_end/testcases/rasta/super_initializer.dart:14:15: Error: Can't have initializers after 'super'.
-      : super.arg0(),
+    : final dynamic #t1 = invalid-expression "pkg/front_end/testcases/rasta/super_initializer.dart:15:15: Error: Can't have initializers after 'super'.
+        field = 42;
               ^", super self::Super::arg0()
     ;
   constructor arg1(dynamic a) → self::Sub*
-    : final dynamic #t2 = invalid-expression "pkg/front_end/testcases/rasta/super_initializer.dart:17:15: Error: Can't have initializers after 'super'.
-      : super.arg1(a),
+    : final dynamic #t2 = invalid-expression "pkg/front_end/testcases/rasta/super_initializer.dart:18:15: Error: Can't have initializers after 'super'.
+        field = 42;
               ^", super self::Super::arg1(a)
     ;
   constructor arg2(dynamic a, dynamic b) → self::Sub*
-    : final dynamic #t3 = invalid-expression "pkg/front_end/testcases/rasta/super_initializer.dart:20:15: Error: Can't have initializers after 'super'.
-      : super.arg2(a, b),
+    : final dynamic #t3 = invalid-expression "pkg/front_end/testcases/rasta/super_initializer.dart:21:15: Error: Can't have initializers after 'super'.
+        field = 42;
               ^", super self::Super::arg2(a, b)
     ;
 }
diff --git a/pkg/kernel/lib/class_hierarchy.dart b/pkg/kernel/lib/class_hierarchy.dart
index e461ce3..446a07f 100644
--- a/pkg/kernel/lib/class_hierarchy.dart
+++ b/pkg/kernel/lib/class_hierarchy.dart
@@ -635,8 +635,14 @@
       }
       ++i2;
       ++i1;
+      if (next.classNode.isAnonymousMixin) {
+        // Never find unnamed mixin application in least upper bound.
+        continue;
+      }
       if (next.depth != currentDepth) {
-        if (numCandidatesAtThisDepth == 1) return candidate;
+        if (numCandidatesAtThisDepth == 1) {
+          return candidate;
+        }
         currentDepth = next.depth;
         numCandidatesAtThisDepth = 0;
         candidate = null;
diff --git a/pkg/kernel/lib/transformations/scanner.dart b/pkg/kernel/lib/transformations/scanner.dart
new file mode 100644
index 0000000..5083fa6
--- /dev/null
+++ b/pkg/kernel/lib/transformations/scanner.dart
@@ -0,0 +1,51 @@
+library kernel.transformations.scanner;
+
+import '../ast.dart';
+import '../kernel.dart';
+
+abstract class Scanner<X extends TreeNode, Y extends TreeNode> {
+  final Scanner<Y, TreeNode> next;
+  Scanner(this.next);
+  bool predicate(X x);
+  ScanResult<X, Y> scan(TreeNode node);
+}
+
+class ScanResult<X extends TreeNode, Y extends TreeNode> {
+  Map<X, ScanResult<Y, TreeNode>> targets;
+  Map<X, ScanError> errors;
+}
+
+class ScanError {}
+
+abstract class ClassScanner<Y extends TreeNode> implements Scanner<Class, Y> {
+  final Scanner<Y, TreeNode> next;
+
+  ClassScanner(this.next);
+
+  bool predicate(Class node);
+
+  ScanResult<Class, Y> scan(TreeNode node) {
+    ScanResult<Class, Y> result = new ScanResult();
+    result.targets = new Map();
+    if (node is Class) {
+      if (predicate(node)) {
+        result.targets[node] = next?.scan(node);
+      }
+    } else if (node is Library) {
+      for (Class cls in node.classes) {
+        if (predicate(cls)) {
+          result.targets[cls] = next?.scan(cls);
+        }
+      }
+    } else if (node is Component) {
+      for (Library library in node.libraries) {
+        for (Class cls in library.classes) {
+          if (predicate(cls)) {
+            result.targets[cls] = next?.scan(cls);
+          }
+        }
+      }
+    }
+    return result;
+  }
+}
diff --git a/pkg/kernel/lib/transformations/value_class.dart b/pkg/kernel/lib/transformations/value_class.dart
index afda4be..9e38786 100644
--- a/pkg/kernel/lib/transformations/value_class.dart
+++ b/pkg/kernel/lib/transformations/value_class.dart
@@ -8,15 +8,31 @@
 import '../kernel.dart';
 import '../core_types.dart' show CoreTypes;
 import '../class_hierarchy.dart' show ClassHierarchy;
+import './scanner.dart';
+
+class ValueClassScanner extends ClassScanner<Null> {
+  ValueClassScanner() : super(null);
+
+  bool predicate(Class node) {
+    for (Expression annotation in node.annotations) {
+      if (annotation is ConstantExpression &&
+          annotation.constant is StringConstant) {
+        StringConstant constant = annotation.constant;
+        if (constant.value == 'valueClass') {
+          return true;
+        }
+      }
+    }
+    return false;
+  }
+}
 
 void transformComponent(
     Component node, CoreTypes coreTypes, ClassHierarchy hierarchy) {
-  for (Library library in node.libraries) {
-    for (Class cls in library.classes) {
-      if (isValueClass(cls)) {
-        transformValueClass(cls, coreTypes, hierarchy);
-      }
-    }
+  ValueClassScanner scanner = new ValueClassScanner();
+  ScanResult<Class, Null> valueClasses = scanner.scan(node);
+  for (Class valueClass in valueClasses.targets.keys) {
+    transformValueClass(valueClass, coreTypes, hierarchy);
   }
 }
 
diff --git a/pkg/kernel/lib/verifier.dart b/pkg/kernel/lib/verifier.dart
index a826d66..5ad6c85 100644
--- a/pkg/kernel/lib/verifier.dart
+++ b/pkg/kernel/lib/verifier.dart
@@ -796,6 +796,21 @@
           " type arguments, but the class declares"
           " ${node.classNode.typeParameters.length} parameters.");
     }
+    if (node.classNode.isAnonymousMixin) {
+      if (currentParent is FunctionNode) {
+        TreeNode functionNodeParent = currentParent.parent;
+        if (functionNodeParent is Constructor ||
+            functionNodeParent is Procedure &&
+                functionNodeParent.kind == ProcedureKind.Factory) {
+          if (functionNodeParent.parent == node.classNode) {
+            // We only allow references to anonymous mixins in types as the
+            // return type of its own constructor.
+            return;
+          }
+        }
+      }
+      problem(currentParent, "Type $node references an anonymous mixin class.");
+    }
   }
 
   @override
diff --git a/tests/language/compile_time_constant/p_test.dart b/tests/language/compile_time_constant/p_test.dart
index 031e929..133519f 100644
--- a/tests/language/compile_time_constant/p_test.dart
+++ b/tests/language/compile_time_constant/p_test.dart
@@ -9,7 +9,7 @@
     this.x
     //   ^
     // [analyzer] COMPILE_TIME_ERROR.FINAL_INITIALIZED_IN_DECLARATION_AND_CONSTRUCTOR
-    // [cfe] 'x' is a final instance variable that has already been initialized.
+    // [cfe] 'x' is a final instance variable that was initialized at the declaration.
     //   ^
     // [cfe] Cannot invoke a non-'const' constructor where a const expression is expected.
       );
diff --git a/tests/language/const/constructor_syntax_test.dart b/tests/language/const/constructor_syntax_test.dart
index d214271..ea34671 100644
--- a/tests/language/const/constructor_syntax_test.dart
+++ b/tests/language/const/constructor_syntax_test.dart
@@ -36,7 +36,6 @@
   const C1();
 //      ^^
 // [analyzer] COMPILE_TIME_ERROR.CONST_CONSTRUCTOR_WITH_NON_FINAL_FIELD
-//      ^
 // [cfe] Constructor is marked 'const' so all fields must be final.
   var modifiable;
 }
@@ -51,7 +50,7 @@
       //^^^^^
       // [analyzer] COMPILE_TIME_ERROR.FIELD_INITIALIZED_IN_INITIALIZER_AND_DECLARATION
       //      ^
-      // [cfe] 'field' is a final instance variable that has already been initialized.
+      // [cfe] 'field' is a final instance variable that was initialized at the declaration.
       //      ^
       // [cfe] Cannot invoke a non-'const' constructor where a const expression is expected.
       //        ^^^^^^^^
diff --git a/tests/language/const/syntax_test.dart b/tests/language/const/syntax_test.dart
index d9eb889..138d30c 100644
--- a/tests/language/const/syntax_test.dart
+++ b/tests/language/const/syntax_test.dart
@@ -9,14 +9,12 @@
   const f1;
   //    ^^
   // [analyzer] COMPILE_TIME_ERROR.CONST_NOT_INITIALIZED
-  //      ^
-  // [cfe] The const variable ';' must be initialized.
+  // [cfe] The const variable 'f1' must be initialized.
   const int f2 = 87;
   const int f3;
   //        ^^
   // [analyzer] COMPILE_TIME_ERROR.CONST_NOT_INITIALIZED
-  //          ^
-  // [cfe] The const variable ';' must be initialized.
+  // [cfe] The const variable 'f3' must be initialized.
   Expect.equals(42, f0);
   Expect.equals(87, f2);
 
@@ -59,10 +57,9 @@
 // [cfe] The const variable 'F1' must be initialized.
 const int F2 = 87;
 const int F3;
-//        ^
-// [cfe] The const variable 'F3' must be initialized.
 //        ^^
 // [analyzer] COMPILE_TIME_ERROR.CONST_NOT_INITIALIZED
+// [cfe] The const variable 'F3' must be initialized.
 
 class Point {
   final x, y;
@@ -113,7 +110,7 @@
       //^
       // [analyzer] COMPILE_TIME_ERROR.FIELD_INITIALIZED_IN_INITIALIZER_AND_DECLARATION
       //  ^
-      // [cfe] 'x' is a final instance variable that has already been initialized.
+      // [cfe] 'x' is a final instance variable that was initialized at the declaration.
       //  ^
       // [cfe] Cannot invoke a non-'const' constructor where a const expression is expected.
   ;
diff --git a/tests/language/constructor/duplicate_initializers_test.dart b/tests/language/constructor/duplicate_initializers_test.dart
index 1b4125a..4f6699e 100644
--- a/tests/language/constructor/duplicate_initializers_test.dart
+++ b/tests/language/constructor/duplicate_initializers_test.dart
@@ -10,7 +10,7 @@
     //^^^^^^
     // [analyzer] COMPILE_TIME_ERROR.FIELD_INITIALIZED_BY_MULTIPLE_INITIALIZERS
     //       ^
-    // [cfe] 'field_' is a final instance variable that has already been initialized.
+    // [cfe] 'field_' was already initialized by this constructor.
    ;
    Class.field(this.field_)
    // Test against duplicate final field initialization between initializing
@@ -19,15 +19,15 @@
     //^^^^^^
     // [analyzer] COMPILE_TIME_ERROR.FIELD_INITIALIZED_IN_PARAMETER_AND_INITIALIZER
     //       ^
-    // [cfe] 'field_' is a final instance variable that has already been initialized.
+    // [cfe] 'field_' was already initialized by this constructor.
    ;
    // Test against duplicate final field initialization in initializing formals.
    Class.two_fields(this.field_
     , this.field_
     //     ^^^^^^
-    // [cfe] 'field_' is a final instance variable that has already been initialized.
-    //     ^^^^^^
     // [analyzer] COMPILE_TIME_ERROR.FINAL_INITIALIZED_MULTIPLE_TIMES
+    // [cfe] 'field_' was already initialized by this constructor.
+    //     ^
     // [cfe] Duplicated parameter name 'field_'.
        );
    final field_;
diff --git a/tests/language/constructor/redirect2_test.dart b/tests/language/constructor/redirect2_test.dart
index 0999747..30d7ab6 100644
--- a/tests/language/constructor/redirect2_test.dart
+++ b/tests/language/constructor/redirect2_test.dart
@@ -18,20 +18,20 @@
   //                         ^^^^^
   // [analyzer] COMPILE_TIME_ERROR.FIELD_INITIALIZER_REDIRECTING_CONSTRUCTOR
   //                           ^
-  // [cfe] Can't have other initializers together with 'this'.
+  // [cfe] A redirecting constructor can't have other initializers.
 
   // Redirecting constructor must not have initializing formal parameters.
   A.illegalFormal(this.x) : this(3);
   //              ^^^^^^
   // [analyzer] COMPILE_TIME_ERROR.FIELD_INITIALIZER_REDIRECTING_CONSTRUCTOR
   //                   ^
-  // [cfe] Can't have other initializers together with 'this'.
+  // [cfe] A redirecting constructor can't have other initializers.
 
   // Redirection constructors must not call super constructor.
   A.illegalSuper() : this(3), super(3);
   //                          ^^^^^^^^
   // [analyzer] COMPILE_TIME_ERROR.SUPER_IN_REDIRECTING_CONSTRUCTOR
-  // [cfe] Can't have other initializers together with 'this'.
+  // [cfe] A redirecting constructor can't have other initializers.
   //                               ^^^
   // [analyzer] COMPILE_TIME_ERROR.EXTRA_POSITIONAL_ARGUMENTS
   // [cfe] Too many positional arguments: 0 allowed, but 1 found.
diff --git a/tests/language/final/attempt_reinitialization_test.dart b/tests/language/final/attempt_reinitialization_test.dart
index 2db5efe..67c2de9 100644
--- a/tests/language/final/attempt_reinitialization_test.dart
+++ b/tests/language/final/attempt_reinitialization_test.dart
@@ -6,7 +6,7 @@
   Foo(this.x);
   //       ^
   // [analyzer] COMPILE_TIME_ERROR.FINAL_INITIALIZED_IN_DECLARATION_AND_CONSTRUCTOR
-  // [cfe] 'x' is a final instance variable that has already been initialized.
+  // [cfe] 'x' is a final instance variable that was initialized at the declaration.
   final int x = 42;
 }
 
@@ -17,7 +17,7 @@
       //     ^^^^^^^^
       // [analyzer] COMPILE_TIME_ERROR.FIELD_INITIALIZED_IN_INITIALIZER_AND_DECLARATION
       //              ^
-      // [cfe] 'shopName' is a final instance variable that has already been initialized.
+      // [cfe] 'shopName' is a final instance variable that was initialized at the declaration.
 }
 
 void main() {
diff --git a/tests/language/variable/initializer_super_last_test.dart b/tests/language/variable/initializer_super_last_test.dart
index 8a4ab9d..5a96d03 100644
--- a/tests/language/variable/initializer_super_last_test.dart
+++ b/tests/language/variable/initializer_super_last_test.dart
@@ -41,63 +41,71 @@
         super(),
 //      ^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.INVALID_SUPER_INVOCATION
-// [cfe] Can't have initializers after 'super'.
         x = x;
+        //^
+        // [cfe] Can't have initializers after 'super'.
   C.cc10(int x)
       : //
         super.named(),
 //      ^^^^^^^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.INVALID_SUPER_INVOCATION
-//            ^
-// [cfe] Can't have initializers after 'super'.
         x = x;
+        //^
+        // [cfe] Can't have initializers after 'super'.
   C.cc11(this.x)
       : //
         super(),
 //      ^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.INVALID_SUPER_INVOCATION
-// [cfe] Can't have initializers after 'super'.
         assert(x == x);
+//      ^
+// [cfe] Can't have initializers after 'super'.
   C.cc12(this.x)
       : //
         super.named(),
 //      ^^^^^^^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.INVALID_SUPER_INVOCATION
-//            ^
-// [cfe] Can't have initializers after 'super'.
         assert(x == x);
+//      ^
+// [cfe] Can't have initializers after 'super'.
   C.cc13(int x)
       : //
         super(),
 //      ^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.INVALID_SUPER_INVOCATION
-// [cfe] Can't have initializers after 'super'.
         x = x,
+        //^
+        // [cfe] Can't have initializers after 'super'.
         assert(x == x);
+//      ^
+// [cfe] Can't have initializers after 'super'.
   C.cc14(int x)
       : //
         super.named(),
 //      ^^^^^^^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.INVALID_SUPER_INVOCATION
-//            ^
-// [cfe] Can't have initializers after 'super'.
         x = x,
+        //^
+        // [cfe] Can't have initializers after 'super'.
         assert(x == x);
+//      ^
+// [cfe] Can't have initializers after 'super'.
   C.cc15(int x)
       : x = x,
         super(),
 //      ^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.INVALID_SUPER_INVOCATION
-// [cfe] Can't have initializers after 'super'.
         assert(x == x);
+//      ^
+// [cfe] Can't have initializers after 'super'.
   C.cc16(int x)
       : x = x,
         super.named(),
 //      ^^^^^^^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.INVALID_SUPER_INVOCATION
-//            ^
-// [cfe] Can't have initializers after 'super'.
         assert(x == x);
+//      ^
+// [cfe] Can't have initializers after 'super'.
 
   const C.cc17(int x)
       : x = x,
@@ -126,63 +134,71 @@
         super(),
 //      ^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.INVALID_SUPER_INVOCATION
-// [cfe] Can't have initializers after 'super'.
         x = x;
+        //^
+        // [cfe] Can't have initializers after 'super'.
   const C.cc26(int x)
       : //
         super.named(),
 //      ^^^^^^^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.INVALID_SUPER_INVOCATION
-//            ^
-// [cfe] Can't have initializers after 'super'.
         x = x;
+        //^
+        // [cfe] Can't have initializers after 'super'.
   const C.cc27(this.x)
       : //
         super(),
 //      ^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.INVALID_SUPER_INVOCATION
-// [cfe] Can't have initializers after 'super'.
         assert(x == x);
+//      ^
+// [cfe] Can't have initializers after 'super'.
   const C.cc28(this.x)
       : //
         super.named(),
 //      ^^^^^^^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.INVALID_SUPER_INVOCATION
-//            ^
-// [cfe] Can't have initializers after 'super'.
         assert(x == x);
+//      ^
+// [cfe] Can't have initializers after 'super'.
   const C.cc29(int x)
       : //
         super(),
 //      ^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.INVALID_SUPER_INVOCATION
-// [cfe] Can't have initializers after 'super'.
         x = x,
+        //^
+        // [cfe] Can't have initializers after 'super'.
         assert(x == x);
+//      ^
+// [cfe] Can't have initializers after 'super'.
   const C.cc30(int x)
       : //
         super.named(),
 //      ^^^^^^^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.INVALID_SUPER_INVOCATION
-//            ^
-// [cfe] Can't have initializers after 'super'.
         x = x,
+        //^
+        // [cfe] Can't have initializers after 'super'.
         assert(x == x);
+//      ^
+// [cfe] Can't have initializers after 'super'.
   const C.cc31(int x)
       : x = x,
         super(),
 //      ^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.INVALID_SUPER_INVOCATION
-// [cfe] Can't have initializers after 'super'.
         assert(x == x);
+//      ^
+// [cfe] Can't have initializers after 'super'.
   const C.cc32(int x)
       : x = x,
         super.named(),
 //      ^^^^^^^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.INVALID_SUPER_INVOCATION
-//            ^
-// [cfe] Can't have initializers after 'super'.
         assert(x == x);
+//      ^
+// [cfe] Can't have initializers after 'super'.
 }
 
 main() {
diff --git a/tests/language_2/compile_time_constant/p_test.dart b/tests/language_2/compile_time_constant/p_test.dart
index 031e929..133519f 100644
--- a/tests/language_2/compile_time_constant/p_test.dart
+++ b/tests/language_2/compile_time_constant/p_test.dart
@@ -9,7 +9,7 @@
     this.x
     //   ^
     // [analyzer] COMPILE_TIME_ERROR.FINAL_INITIALIZED_IN_DECLARATION_AND_CONSTRUCTOR
-    // [cfe] 'x' is a final instance variable that has already been initialized.
+    // [cfe] 'x' is a final instance variable that was initialized at the declaration.
     //   ^
     // [cfe] Cannot invoke a non-'const' constructor where a const expression is expected.
       );
diff --git a/tests/language_2/const/constructor_syntax_test.dart b/tests/language_2/const/constructor_syntax_test.dart
index d214271..ea34671 100644
--- a/tests/language_2/const/constructor_syntax_test.dart
+++ b/tests/language_2/const/constructor_syntax_test.dart
@@ -36,7 +36,6 @@
   const C1();
 //      ^^
 // [analyzer] COMPILE_TIME_ERROR.CONST_CONSTRUCTOR_WITH_NON_FINAL_FIELD
-//      ^
 // [cfe] Constructor is marked 'const' so all fields must be final.
   var modifiable;
 }
@@ -51,7 +50,7 @@
       //^^^^^
       // [analyzer] COMPILE_TIME_ERROR.FIELD_INITIALIZED_IN_INITIALIZER_AND_DECLARATION
       //      ^
-      // [cfe] 'field' is a final instance variable that has already been initialized.
+      // [cfe] 'field' is a final instance variable that was initialized at the declaration.
       //      ^
       // [cfe] Cannot invoke a non-'const' constructor where a const expression is expected.
       //        ^^^^^^^^
diff --git a/tests/language_2/const/syntax_test.dart b/tests/language_2/const/syntax_test.dart
index 375fb6a..138d30c 100644
--- a/tests/language_2/const/syntax_test.dart
+++ b/tests/language_2/const/syntax_test.dart
@@ -110,7 +110,7 @@
       //^
       // [analyzer] COMPILE_TIME_ERROR.FIELD_INITIALIZED_IN_INITIALIZER_AND_DECLARATION
       //  ^
-      // [cfe] 'x' is a final instance variable that has already been initialized.
+      // [cfe] 'x' is a final instance variable that was initialized at the declaration.
       //  ^
       // [cfe] Cannot invoke a non-'const' constructor where a const expression is expected.
   ;
diff --git a/tests/language_2/constructor/duplicate_initializers_test.dart b/tests/language_2/constructor/duplicate_initializers_test.dart
index 1b4125a..4f6699e 100644
--- a/tests/language_2/constructor/duplicate_initializers_test.dart
+++ b/tests/language_2/constructor/duplicate_initializers_test.dart
@@ -10,7 +10,7 @@
     //^^^^^^
     // [analyzer] COMPILE_TIME_ERROR.FIELD_INITIALIZED_BY_MULTIPLE_INITIALIZERS
     //       ^
-    // [cfe] 'field_' is a final instance variable that has already been initialized.
+    // [cfe] 'field_' was already initialized by this constructor.
    ;
    Class.field(this.field_)
    // Test against duplicate final field initialization between initializing
@@ -19,15 +19,15 @@
     //^^^^^^
     // [analyzer] COMPILE_TIME_ERROR.FIELD_INITIALIZED_IN_PARAMETER_AND_INITIALIZER
     //       ^
-    // [cfe] 'field_' is a final instance variable that has already been initialized.
+    // [cfe] 'field_' was already initialized by this constructor.
    ;
    // Test against duplicate final field initialization in initializing formals.
    Class.two_fields(this.field_
     , this.field_
     //     ^^^^^^
-    // [cfe] 'field_' is a final instance variable that has already been initialized.
-    //     ^^^^^^
     // [analyzer] COMPILE_TIME_ERROR.FINAL_INITIALIZED_MULTIPLE_TIMES
+    // [cfe] 'field_' was already initialized by this constructor.
+    //     ^
     // [cfe] Duplicated parameter name 'field_'.
        );
    final field_;
diff --git a/tests/language_2/constructor/redirect2_test.dart b/tests/language_2/constructor/redirect2_test.dart
index 0999747..30d7ab6 100644
--- a/tests/language_2/constructor/redirect2_test.dart
+++ b/tests/language_2/constructor/redirect2_test.dart
@@ -18,20 +18,20 @@
   //                         ^^^^^
   // [analyzer] COMPILE_TIME_ERROR.FIELD_INITIALIZER_REDIRECTING_CONSTRUCTOR
   //                           ^
-  // [cfe] Can't have other initializers together with 'this'.
+  // [cfe] A redirecting constructor can't have other initializers.
 
   // Redirecting constructor must not have initializing formal parameters.
   A.illegalFormal(this.x) : this(3);
   //              ^^^^^^
   // [analyzer] COMPILE_TIME_ERROR.FIELD_INITIALIZER_REDIRECTING_CONSTRUCTOR
   //                   ^
-  // [cfe] Can't have other initializers together with 'this'.
+  // [cfe] A redirecting constructor can't have other initializers.
 
   // Redirection constructors must not call super constructor.
   A.illegalSuper() : this(3), super(3);
   //                          ^^^^^^^^
   // [analyzer] COMPILE_TIME_ERROR.SUPER_IN_REDIRECTING_CONSTRUCTOR
-  // [cfe] Can't have other initializers together with 'this'.
+  // [cfe] A redirecting constructor can't have other initializers.
   //                               ^^^
   // [analyzer] COMPILE_TIME_ERROR.EXTRA_POSITIONAL_ARGUMENTS
   // [cfe] Too many positional arguments: 0 allowed, but 1 found.
diff --git a/tests/language_2/final/attempt_reinitialization_test.dart b/tests/language_2/final/attempt_reinitialization_test.dart
index 2db5efe..67c2de9 100644
--- a/tests/language_2/final/attempt_reinitialization_test.dart
+++ b/tests/language_2/final/attempt_reinitialization_test.dart
@@ -6,7 +6,7 @@
   Foo(this.x);
   //       ^
   // [analyzer] COMPILE_TIME_ERROR.FINAL_INITIALIZED_IN_DECLARATION_AND_CONSTRUCTOR
-  // [cfe] 'x' is a final instance variable that has already been initialized.
+  // [cfe] 'x' is a final instance variable that was initialized at the declaration.
   final int x = 42;
 }
 
@@ -17,7 +17,7 @@
       //     ^^^^^^^^
       // [analyzer] COMPILE_TIME_ERROR.FIELD_INITIALIZED_IN_INITIALIZER_AND_DECLARATION
       //              ^
-      // [cfe] 'shopName' is a final instance variable that has already been initialized.
+      // [cfe] 'shopName' is a final instance variable that was initialized at the declaration.
 }
 
 void main() {
diff --git a/tests/language_2/variable/initializer_super_last_test.dart b/tests/language_2/variable/initializer_super_last_test.dart
index 8a4ab9d..5a96d03 100644
--- a/tests/language_2/variable/initializer_super_last_test.dart
+++ b/tests/language_2/variable/initializer_super_last_test.dart
@@ -41,63 +41,71 @@
         super(),
 //      ^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.INVALID_SUPER_INVOCATION
-// [cfe] Can't have initializers after 'super'.
         x = x;
+        //^
+        // [cfe] Can't have initializers after 'super'.
   C.cc10(int x)
       : //
         super.named(),
 //      ^^^^^^^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.INVALID_SUPER_INVOCATION
-//            ^
-// [cfe] Can't have initializers after 'super'.
         x = x;
+        //^
+        // [cfe] Can't have initializers after 'super'.
   C.cc11(this.x)
       : //
         super(),
 //      ^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.INVALID_SUPER_INVOCATION
-// [cfe] Can't have initializers after 'super'.
         assert(x == x);
+//      ^
+// [cfe] Can't have initializers after 'super'.
   C.cc12(this.x)
       : //
         super.named(),
 //      ^^^^^^^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.INVALID_SUPER_INVOCATION
-//            ^
-// [cfe] Can't have initializers after 'super'.
         assert(x == x);
+//      ^
+// [cfe] Can't have initializers after 'super'.
   C.cc13(int x)
       : //
         super(),
 //      ^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.INVALID_SUPER_INVOCATION
-// [cfe] Can't have initializers after 'super'.
         x = x,
+        //^
+        // [cfe] Can't have initializers after 'super'.
         assert(x == x);
+//      ^
+// [cfe] Can't have initializers after 'super'.
   C.cc14(int x)
       : //
         super.named(),
 //      ^^^^^^^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.INVALID_SUPER_INVOCATION
-//            ^
-// [cfe] Can't have initializers after 'super'.
         x = x,
+        //^
+        // [cfe] Can't have initializers after 'super'.
         assert(x == x);
+//      ^
+// [cfe] Can't have initializers after 'super'.
   C.cc15(int x)
       : x = x,
         super(),
 //      ^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.INVALID_SUPER_INVOCATION
-// [cfe] Can't have initializers after 'super'.
         assert(x == x);
+//      ^
+// [cfe] Can't have initializers after 'super'.
   C.cc16(int x)
       : x = x,
         super.named(),
 //      ^^^^^^^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.INVALID_SUPER_INVOCATION
-//            ^
-// [cfe] Can't have initializers after 'super'.
         assert(x == x);
+//      ^
+// [cfe] Can't have initializers after 'super'.
 
   const C.cc17(int x)
       : x = x,
@@ -126,63 +134,71 @@
         super(),
 //      ^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.INVALID_SUPER_INVOCATION
-// [cfe] Can't have initializers after 'super'.
         x = x;
+        //^
+        // [cfe] Can't have initializers after 'super'.
   const C.cc26(int x)
       : //
         super.named(),
 //      ^^^^^^^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.INVALID_SUPER_INVOCATION
-//            ^
-// [cfe] Can't have initializers after 'super'.
         x = x;
+        //^
+        // [cfe] Can't have initializers after 'super'.
   const C.cc27(this.x)
       : //
         super(),
 //      ^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.INVALID_SUPER_INVOCATION
-// [cfe] Can't have initializers after 'super'.
         assert(x == x);
+//      ^
+// [cfe] Can't have initializers after 'super'.
   const C.cc28(this.x)
       : //
         super.named(),
 //      ^^^^^^^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.INVALID_SUPER_INVOCATION
-//            ^
-// [cfe] Can't have initializers after 'super'.
         assert(x == x);
+//      ^
+// [cfe] Can't have initializers after 'super'.
   const C.cc29(int x)
       : //
         super(),
 //      ^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.INVALID_SUPER_INVOCATION
-// [cfe] Can't have initializers after 'super'.
         x = x,
+        //^
+        // [cfe] Can't have initializers after 'super'.
         assert(x == x);
+//      ^
+// [cfe] Can't have initializers after 'super'.
   const C.cc30(int x)
       : //
         super.named(),
 //      ^^^^^^^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.INVALID_SUPER_INVOCATION
-//            ^
-// [cfe] Can't have initializers after 'super'.
         x = x,
+        //^
+        // [cfe] Can't have initializers after 'super'.
         assert(x == x);
+//      ^
+// [cfe] Can't have initializers after 'super'.
   const C.cc31(int x)
       : x = x,
         super(),
 //      ^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.INVALID_SUPER_INVOCATION
-// [cfe] Can't have initializers after 'super'.
         assert(x == x);
+//      ^
+// [cfe] Can't have initializers after 'super'.
   const C.cc32(int x)
       : x = x,
         super.named(),
 //      ^^^^^^^^^^^^^
 // [analyzer] COMPILE_TIME_ERROR.INVALID_SUPER_INVOCATION
-//            ^
-// [cfe] Can't have initializers after 'super'.
         assert(x == x);
+//      ^
+// [cfe] Can't have initializers after 'super'.
 }
 
 main() {
diff --git a/tools/VERSION b/tools/VERSION
index 7ec9e7a..54f30f2 100644
--- a/tools/VERSION
+++ b/tools/VERSION
@@ -27,5 +27,5 @@
 MAJOR 2
 MINOR 10
 PATCH 0
-PRERELEASE 107
+PRERELEASE 108
 PRERELEASE_PATCH 0
\ No newline at end of file