diff --git a/pkg/analysis_server/lib/src/services/completion/dart/utilities.dart b/pkg/analysis_server/lib/src/services/completion/dart/utilities.dart
index 409b979..a40613c 100644
--- a/pkg/analysis_server/lib/src/services/completion/dart/utilities.dart
+++ b/pkg/analysis_server/lib/src/services/completion/dart/utilities.dart
@@ -213,7 +213,7 @@
   }
 
   // If the type is unresolved, use the declared type.
-  if (type != null && type.isUndefined) {
+  if (type != null && type.isDynamic) {
     if (declaredType is TypeName) {
       Identifier id = declaredType.name;
       if (id != null) {
diff --git a/pkg/analyzer/CHANGELOG.md b/pkg/analyzer/CHANGELOG.md
index e30b6cf..86763bf 100644
--- a/pkg/analyzer/CHANGELOG.md
+++ b/pkg/analyzer/CHANGELOG.md
@@ -1,3 +1,6 @@
+## 0.36.1
+* Deprecated `DartType.isUndefined`, and now it always returns `false`.
+
 ## 0.36.0
 * Changed the return type of `Expression.precendence` to `Precedence`.  Clients
   that prepared for this change by switching to `Expression.precedence2` should
diff --git a/pkg/analyzer/lib/dart/element/type.dart b/pkg/analyzer/lib/dart/element/type.dart
index 7c752c2..ce67ab7 100644
--- a/pkg/analyzer/lib/dart/element/type.dart
+++ b/pkg/analyzer/lib/dart/element/type.dart
@@ -80,6 +80,7 @@
 
   /// Return `true` if this type represents a typename that couldn't be
   /// resolved.
+  @deprecated
   bool get isUndefined;
 
   /// Return `true` if this type represents the type 'void'.
diff --git a/pkg/analyzer/lib/src/dart/constant/evaluation.dart b/pkg/analyzer/lib/src/dart/constant/evaluation.dart
index 112dce6..6633be9 100644
--- a/pkg/analyzer/lib/src/dart/constant/evaluation.dart
+++ b/pkg/analyzer/lib/src/dart/constant/evaluation.dart
@@ -902,9 +902,6 @@
     if (obj.isNull) {
       return true;
     }
-    if (type.isUndefined) {
-      return false;
-    }
     var objType = obj.type;
     if (objType.isDartCoreInt && type.isDartCoreDouble) {
       // Work around dartbug.com/35993 by allowing `int` to be used in a place
diff --git a/pkg/analyzer/lib/src/dart/element/type.dart b/pkg/analyzer/lib/src/dart/element/type.dart
index 267f338..3f36fcf 100644
--- a/pkg/analyzer/lib/src/dart/element/type.dart
+++ b/pkg/analyzer/lib/src/dart/element/type.dart
@@ -3265,87 +3265,6 @@
 }
 
 /**
- * The unique instance of the class `UndefinedTypeImpl` implements the type of
- * type names that couldn't be resolved.
- *
- * This class behaves like DynamicTypeImpl in almost every respect, to reduce
- * cascading errors.
- */
-class UndefinedTypeImpl extends TypeImpl {
-  /**
-   * The unique instance of this class.
-   */
-  static final UndefinedTypeImpl instance = new UndefinedTypeImpl._();
-
-  /**
-   * Prevent the creation of instances of this class.
-   */
-  UndefinedTypeImpl._()
-      : super(DynamicElementImpl.instance, Keyword.DYNAMIC.lexeme);
-
-  @override
-  int get hashCode => 1;
-
-  @override
-  bool get isDynamic => true;
-
-  @override
-  bool get isUndefined => true;
-
-  @override
-  NullabilitySuffix get nullabilitySuffix => NullabilitySuffix.star;
-
-  @override
-  bool operator ==(Object object) => identical(object, this);
-
-  @override
-  bool isMoreSpecificThan(DartType type,
-      [bool withDynamic = false, Set<Element> visitedElements]) {
-    // T is S
-    if (identical(this, type)) {
-      return true;
-    }
-    // else
-    return withDynamic;
-  }
-
-  @override
-  bool isSubtypeOf(DartType type) => true;
-
-  @override
-  bool isSupertypeOf(DartType type) => true;
-
-  @override
-  TypeImpl pruned(List<FunctionTypeAliasElement> prune) => this;
-
-  @override
-  DartType replaceTopAndBottom(TypeProvider typeProvider,
-      {bool isCovariant = true}) {
-    if (isCovariant) {
-      return typeProvider.nullType;
-    } else {
-      return this;
-    }
-  }
-
-  @override
-  DartType substitute2(
-      List<DartType> argumentTypes, List<DartType> parameterTypes,
-      [List<FunctionTypeAliasElement> prune]) {
-    int length = parameterTypes.length;
-    for (int i = 0; i < length; i++) {
-      if (parameterTypes[i] == this) {
-        return argumentTypes[i];
-      }
-    }
-    return this;
-  }
-
-  @override
-  TypeImpl withNullability(NullabilitySuffix nullabilitySuffix) => this;
-}
-
-/**
  * The type `void`.
  */
 abstract class VoidType implements DartType {
diff --git a/pkg/analyzer/lib/src/generated/declaration_resolver.dart b/pkg/analyzer/lib/src/generated/declaration_resolver.dart
index b956a8a..582ab2d 100644
--- a/pkg/analyzer/lib/src/generated/declaration_resolver.dart
+++ b/pkg/analyzer/lib/src/generated/declaration_resolver.dart
@@ -735,7 +735,7 @@
   /// corresponding type arguments of the [typeArguments].
   static void _applyTypeArgumentsToList(LibraryElement enclosingLibraryElement,
       DartType type, List<TypeAnnotation> typeArguments) {
-    if (type != null && type.isUndefined) {
+    if (type != null && type.isDynamic) {
       for (TypeAnnotation argument in typeArguments) {
         applyToTypeAnnotation(enclosingLibraryElement, type, argument);
       }
diff --git a/pkg/analyzer/lib/src/generated/resolver.dart b/pkg/analyzer/lib/src/generated/resolver.dart
index 49ba32d..1ff7522 100644
--- a/pkg/analyzer/lib/src/generated/resolver.dart
+++ b/pkg/analyzer/lib/src/generated/resolver.dart
@@ -6255,7 +6255,6 @@
 class TypeNameResolver {
   final TypeSystem typeSystem;
   final DartType dynamicType;
-  final DartType undefinedType;
   final bool isNonNullableUnit;
   final AnalysisOptionsImpl analysisOptions;
   final LibraryElement definingLibrary;
@@ -6280,7 +6279,6 @@
       this.errorListener,
       {this.shouldUseWithClauseInferredTypes: true})
       : dynamicType = typeProvider.dynamicType,
-        undefinedType = typeProvider.undefinedType,
         analysisOptions = definingLibrary.context.analysisOptions;
 
   /// Report an error with the given error code and arguments.
@@ -6322,8 +6320,8 @@
         return;
       }
       if (nameScope.shouldIgnoreUndefined(typeName)) {
-        typeName.staticType = undefinedType;
-        node.type = undefinedType;
+        typeName.staticType = dynamicType;
+        node.type = dynamicType;
         return;
       }
       //
@@ -6343,8 +6341,8 @@
           element = nameScope.lookup(prefix, definingLibrary);
           if (element is PrefixElement) {
             if (nameScope.shouldIgnoreUndefined(typeName)) {
-              typeName.staticType = undefinedType;
-              node.type = undefinedType;
+              typeName.staticType = dynamicType;
+              node.type = dynamicType;
               return;
             }
             AstNode grandParent = parent.parent;
@@ -6382,8 +6380,8 @@
         }
       }
       if (nameScope.shouldIgnoreUndefined(typeName)) {
-        typeName.staticType = undefinedType;
-        node.type = undefinedType;
+        typeName.staticType = dynamicType;
+        node.type = dynamicType;
         return;
       }
     }
@@ -6500,8 +6498,8 @@
       if (element is MultiplyDefinedElement) {
         _setElement(typeName, element);
       }
-      typeName.staticType = undefinedType;
-      node.type = undefinedType;
+      typeName.staticType = dynamicType;
+      node.type = dynamicType;
       return;
     }
 
@@ -6674,7 +6672,7 @@
   DartType _getType(TypeAnnotation annotation) {
     DartType type = annotation.type;
     if (type == null) {
-      return undefinedType;
+      return dynamicType;
     }
     return type;
   }
@@ -7231,9 +7229,6 @@
   /// Return the type representing the built-in type 'Type'.
   InterfaceType get typeType;
 
-  /// Return the type representing typenames that can't be resolved.
-  DartType get undefinedType;
-
   /// Return 'true' if [id] is the name of a getter on
   /// the Object type.
   bool isObjectGetter(String id);
@@ -7372,9 +7367,6 @@
   /// The type representing the built-in type 'Type'.
   InterfaceType _typeType;
 
-  /// The type representing typenames that can't be resolved.
-  DartType _undefinedType;
-
   /// Initialize a newly created type provider to provide the types defined in
   /// the given [coreLibrary] and [asyncLibrary].
   TypeProviderImpl(LibraryElement coreLibrary, LibraryElement asyncLibrary) {
@@ -7476,9 +7468,6 @@
   @override
   InterfaceType get typeType => _typeType;
 
-  @override
-  DartType get undefinedType => _undefinedType;
-
   InterfaceType _createNever(Namespace namespace) {
     // TODO(brianwilkerson) Remove this method when the class is defined in the
     //  SDK.
@@ -7533,7 +7522,6 @@
     _stringType = _getType(coreNamespace, 'String');
     _symbolType = _getType(coreNamespace, 'Symbol');
     _typeType = _getType(coreNamespace, 'Type');
-    _undefinedType = UndefinedTypeImpl.instance;
     _futureDynamicType = _futureType.instantiate(<DartType>[_dynamicType]);
     _futureNullType = _futureType.instantiate(<DartType>[_nullType]);
     _iterableDynamicType = _iterableType.instantiate(<DartType>[_dynamicType]);
@@ -7587,9 +7575,6 @@
   /// The type representing the type 'dynamic'.
   DartType _dynamicType;
 
-  /// The type representing typenames that can't be resolved.
-  DartType _undefinedType;
-
   /// The flag specifying if currently visited class references 'super'
   /// expression.
   bool _hasReferenceToSuper = false;
@@ -7645,7 +7630,6 @@
       : super(definingLibrary, source, typeProvider, errorListener,
             nameScope: nameScope) {
     _dynamicType = typeProvider.dynamicType;
-    _undefinedType = typeProvider.undefinedType;
     _typeSystem = TypeSystem.create(definingLibrary.context);
     _typeNameResolver = new TypeNameResolver(_typeSystem, typeProvider,
         isNonNullableUnit, definingLibrary, source, errorListener,
diff --git a/pkg/analyzer/lib/src/generated/testing/test_type_provider.dart b/pkg/analyzer/lib/src/generated/testing/test_type_provider.dart
index bb052ad..da58fd1 100644
--- a/pkg/analyzer/lib/src/generated/testing/test_type_provider.dart
+++ b/pkg/analyzer/lib/src/generated/testing/test_type_provider.dart
@@ -179,11 +179,6 @@
   InterfaceType _typeType;
 
   /**
-   * The type representing type names that can't be resolved.
-   */
-  DartType _undefinedType;
-
-  /**
    * The analysis context, if any. Used to create an appropriate 'dart:async'
    * library to back `Future<T>`.
    */
@@ -612,14 +607,6 @@
     return _typeType;
   }
 
-  @override
-  DartType get undefinedType {
-    if (_undefinedType == null) {
-      _undefinedType = UndefinedTypeImpl.instance;
-    }
-    return _undefinedType;
-  }
-
   void _initDartAsync() {
     Source asyncSource;
     if (_driver != null) {
diff --git a/pkg/analyzer/lib/src/summary/link.dart b/pkg/analyzer/lib/src/summary/link.dart
index 012a2ac..76eaf73 100644
--- a/pkg/analyzer/lib/src/summary/link.dart
+++ b/pkg/analyzer/lib/src/summary/link.dart
@@ -5481,9 +5481,6 @@
   InterfaceType get typeType =>
       _typeType ??= _buildInterfaceType(_linker.coreLibrary, 'Type');
 
-  @override
-  DartType get undefinedType => UndefinedTypeImpl.instance;
-
   InterfaceType _buildInterfaceType(
       LibraryElementForLink library, String name) {
     return library.getContainedName(name).buildType((int i) {
diff --git a/pkg/analyzer/lib/src/summary/resynthesize.dart b/pkg/analyzer/lib/src/summary/resynthesize.dart
index 3c6b194..6f8720e 100644
--- a/pkg/analyzer/lib/src/summary/resynthesize.dart
+++ b/pkg/analyzer/lib/src/summary/resynthesize.dart
@@ -1491,7 +1491,7 @@
       bool isDeclarableType = false;
       int numTypeParameters = linkedReference.numTypeParameters;
       if (linkedReference.kind == ReferenceKind.unresolved) {
-        type = UndefinedTypeImpl.instance;
+        type = DynamicTypeImpl.instance;
         element = null;
         isDeclarableType = true;
       } else if (name == 'dynamic') {
diff --git a/pkg/analyzer/lib/src/summary/summary_sdk.dart b/pkg/analyzer/lib/src/summary/summary_sdk.dart
index f31b076..28dc74a 100644
--- a/pkg/analyzer/lib/src/summary/summary_sdk.dart
+++ b/pkg/analyzer/lib/src/summary/summary_sdk.dart
@@ -349,9 +349,6 @@
     return _typeType;
   }
 
-  @override
-  DartType get undefinedType => UndefinedTypeImpl.instance;
-
   /**
    * Initialize the `dart:async` types provided by this type provider.
    */
diff --git a/pkg/analyzer/test/generated/checked_mode_compile_time_error_code_test.dart b/pkg/analyzer/test/generated/checked_mode_compile_time_error_code_test.dart
index 46f7960..4a01b55 100644
--- a/pkg/analyzer/test/generated/checked_mode_compile_time_error_code_test.dart
+++ b/pkg/analyzer/test/generated/checked_mode_compile_time_error_code_test.dart
@@ -227,10 +227,7 @@
   const A(String this.x);
 }
 var v = const A('foo');
-''', [
-      CheckedModeCompileTimeErrorCode.CONST_CONSTRUCTOR_PARAM_TYPE_MISMATCH,
-      StaticWarningCode.UNDEFINED_CLASS
-    ]);
+''', [StaticWarningCode.UNDEFINED_CLASS]);
   }
 
   test_fieldFormalParameterNotAssignableToField_implements() async {
@@ -362,10 +359,7 @@
   final Unresolved y;
 }
 var v = const A('foo');
-''', [
-      CheckedModeCompileTimeErrorCode.CONST_CONSTRUCTOR_FIELD_TYPE_MISMATCH,
-      StaticWarningCode.UNDEFINED_CLASS
-    ]);
+''', [StaticWarningCode.UNDEFINED_CLASS]);
   }
 
   test_fieldTypeOk_generic() async {
@@ -489,10 +483,7 @@
   const A(Unresolved x);
 }
 var v = const A('foo');
-''', [
-      CheckedModeCompileTimeErrorCode.CONST_CONSTRUCTOR_PARAM_TYPE_MISMATCH,
-      StaticWarningCode.UNDEFINED_CLASS
-    ]);
+''', [StaticWarningCode.UNDEFINED_CLASS]);
   }
 
   test_redirectingConstructor_paramTypeMismatch() async {
@@ -544,9 +535,6 @@
   test_topLevelVarNotAssignable_undefined() async {
     await assertErrorCodesInCode('''
 const Unresolved x = 'foo';
-''', [
-      CheckedModeCompileTimeErrorCode.VARIABLE_TYPE_MISMATCH,
-      StaticWarningCode.UNDEFINED_CLASS
-    ]);
+''', [StaticWarningCode.UNDEFINED_CLASS]);
   }
 }
diff --git a/pkg/analyzer/test/generated/resolver_test.dart b/pkg/analyzer/test/generated/resolver_test.dart
index 9c5be7a..b7c7c60 100644
--- a/pkg/analyzer/test/generated/resolver_test.dart
+++ b/pkg/analyzer/test/generated/resolver_test.dart
@@ -1953,7 +1953,7 @@
       ..staticElement = new _StaleElement();
     TypeName typeName = astFactory.typeName(id, null);
     _resolveNode(typeName, []);
-    expect(typeName.type, UndefinedTypeImpl.instance);
+    expect(typeName.type, DynamicTypeImpl.instance);
     expect(typeName.name.staticElement, null);
     _listener.assertErrorsWithCodes([StaticWarningCode.UNDEFINED_CLASS]);
   }
@@ -1994,7 +1994,7 @@
     TypeName typeName =
         astFactory.typeName(AstTestFactory.identifier(prefix, suffix), null);
     _resolveNode(typeName, []);
-    expect(typeName.type, UndefinedTypeImpl.instance);
+    expect(typeName.type, DynamicTypeImpl.instance);
     expect(prefix.staticElement, null);
     expect(suffix.staticElement, null);
     _listener.assertErrorsWithCodes([StaticWarningCode.UNDEFINED_CLASS]);
diff --git a/pkg/analyzer/test/src/dart/analysis/driver_resolution_test.dart b/pkg/analyzer/test/src/dart/analysis/driver_resolution_test.dart
index b116529..48504cb 100644
--- a/pkg/analyzer/test/src/dart/analysis/driver_resolution_test.dart
+++ b/pkg/analyzer/test/src/dart/analysis/driver_resolution_test.dart
@@ -35,8 +35,6 @@
 
 final isDynamicType = new TypeMatcher<DynamicTypeImpl>();
 
-final isUndefinedType = new TypeMatcher<UndefinedTypeImpl>();
-
 final isVoidType = new TypeMatcher<VoidTypeImpl>();
 
 /**
@@ -1837,12 +1835,12 @@
     VariableDeclarationStatement statement = statements[0];
 
     TypeName typeName = statement.variables.type;
-    expect(typeName.type, isUndefinedType);
+    expect(typeName.type, isDynamicType);
     expect(typeName.typeArguments.arguments[0].type, typeProvider.intType);
 
     VariableDeclaration vNode = statement.variables.variables[0];
-    expect(vNode.name.staticType, isUndefinedType);
-    expect(vNode.declaredElement.type, isUndefinedType);
+    expect(vNode.name.staticType, isDynamicType);
+    expect(vNode.declaredElement.type, isDynamicType);
   }
 
   test_field_context() async {
@@ -8095,7 +8093,6 @@
     assertType(identifier, 'Type');
   }
 
-  @failingTest
   test_unresolved_instanceCreation_name_11() async {
     addTestFile(r'''
 int arg1, arg2;
@@ -8226,12 +8223,12 @@
     ExpressionStatement statement = statements[0];
 
     InstanceCreationExpression creation = statement.expression;
-    expect(creation.staticType, isUndefinedType);
+    expect(creation.staticType, isDynamicType);
 
     ConstructorName constructorName = creation.constructorName;
 
     TypeName typeName = constructorName.type;
-    expect(typeName.type, isUndefinedType);
+    expect(typeName.type, isDynamicType);
 
     PrefixedIdentifier typePrefixed = typeName.name;
     assertElementNull(typePrefixed);
@@ -8273,12 +8270,12 @@
     ExpressionStatement statement = statements[0];
 
     InstanceCreationExpression creation = statement.expression;
-    expect(creation.staticType, isUndefinedType);
+    expect(creation.staticType, isDynamicType);
 
     ConstructorName constructorName = creation.constructorName;
 
     TypeName typeName = constructorName.type;
-    expect(typeName.type, isUndefinedType);
+    expect(typeName.type, isDynamicType);
 
     PrefixedIdentifier typePrefixed = typeName.name;
     assertElementNull(typePrefixed);
diff --git a/pkg/analyzer/test/src/dart/resolution/resolution.dart b/pkg/analyzer/test/src/dart/resolution/resolution.dart
index b713264..b7fb02f 100644
--- a/pkg/analyzer/test/src/dart/resolution/resolution.dart
+++ b/pkg/analyzer/test/src/dart/resolution/resolution.dart
@@ -26,8 +26,6 @@
 
 final isDynamicType = new TypeMatcher<DynamicTypeImpl>();
 
-final isUndefinedType = new TypeMatcher<UndefinedTypeImpl>();
-
 final isVoidType = new TypeMatcher<VoidTypeImpl>();
 
 /// Base for resolution tests.