diff --git a/pkg/analyzer/lib/src/dart/analysis/context_locator.dart b/pkg/analyzer/lib/src/dart/analysis/context_locator.dart
index daa8e97..ade3b53 100644
--- a/pkg/analyzer/lib/src/dart/analysis/context_locator.dart
+++ b/pkg/analyzer/lib/src/dart/analysis/context_locator.dart
@@ -15,6 +15,7 @@
 import 'package:analyzer/src/task/options.dart';
 import 'package:analyzer/src/util/file_paths.dart' as file_paths;
 import 'package:analyzer/src/util/yaml.dart';
+import 'package:analyzer/src/utilities/extensions/file_system.dart';
 import 'package:analyzer/src/workspace/basic.dart';
 import 'package:analyzer/src/workspace/bazel.dart';
 import 'package:analyzer/src/workspace/gn.dart';
@@ -185,7 +186,7 @@
     if (defaultOptionsFile != null) {
       optionsFile = defaultOptionsFile;
     } else {
-      optionsFile = _findOptionsFile(parent);
+      optionsFile = parent.findAnalysisOptionsYamlFile();
       optionsFolderToChooseRoot = optionsFile?.parent;
     }
 
@@ -271,7 +272,7 @@
     //
     File? localOptionsFile;
     if (optionsFile == null) {
-      localOptionsFile = _getOptionsFile(folder);
+      localOptionsFile = folder.existingAnalysisOptionsYamlFile;
     }
     File? localPackagesFile;
     if (packagesFile == null) {
@@ -406,19 +407,6 @@
     return null;
   }
 
-  /// Return the analysis options file to be used to analyze files in the given
-  /// [folder], or `null` if there is no analysis options file in the given
-  /// folder or any parent folder.
-  File? _findOptionsFile(Folder folder) {
-    for (var current in folder.withAncestors) {
-      var file = _getOptionsFile(current);
-      if (file != null) {
-        return file;
-      }
-    }
-    return null;
-  }
-
   /// Return the packages file to be used to analyze files in the given
   /// [folder], or `null` if there is no packages file in the given folder or
   /// any parent folder.
@@ -480,18 +468,6 @@
     return patterns;
   }
 
-  /// If the given [directory] contains a file with the given [name], then
-  /// return the file. Otherwise, return `null`.
-  File? _getFile(Folder directory, String name) {
-    var file = directory.getChildAssumingFile(name);
-    return file.exists ? file : null;
-  }
-
-  /// Return the analysis options file in the given [folder], or `null` if the
-  /// folder does not contain an analysis options file.
-  File? _getOptionsFile(Folder folder) =>
-      _getFile(folder, file_paths.analysisOptionsYaml);
-
   /// Return the packages file in the given [folder], or `null` if the folder
   /// does not contain a packages file.
   File? _getPackagesFile(Folder folder) {
diff --git a/pkg/analyzer/lib/src/dart/micro/cider_byte_store.dart b/pkg/analyzer/lib/src/dart/micro/cider_byte_store.dart
deleted file mode 100644
index 91e96e3..0000000
--- a/pkg/analyzer/lib/src/dart/micro/cider_byte_store.dart
+++ /dev/null
@@ -1,11 +0,0 @@
-// 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.
-
-@Deprecated('Use ByteStore directly instead')
-library cider_byte_store;
-
-import 'package:analyzer/src/dart/analysis/byte_store.dart';
-
-@Deprecated('Use ByteStore directly instead')
-typedef CiderByteStore = ByteStore;
diff --git a/pkg/analyzer/lib/src/dart/micro/resolve_file.dart b/pkg/analyzer/lib/src/dart/micro/resolve_file.dart
index cb43de1..cea7103 100644
--- a/pkg/analyzer/lib/src/dart/micro/resolve_file.dart
+++ b/pkg/analyzer/lib/src/dart/micro/resolve_file.dart
@@ -37,8 +37,8 @@
 import 'package:analyzer/src/summary2/link.dart';
 import 'package:analyzer/src/summary2/linked_element_factory.dart';
 import 'package:analyzer/src/task/options.dart';
-import 'package:analyzer/src/util/file_paths.dart' as file_paths;
 import 'package:analyzer/src/util/performance/operation_performance.dart';
+import 'package:analyzer/src/utilities/extensions/file_system.dart';
 import 'package:analyzer/src/workspace/workspace.dart';
 import 'package:collection/collection.dart';
 import 'package:meta/meta.dart';
@@ -735,16 +735,6 @@
     }
   }
 
-  File? _findOptionsFile(Folder folder) {
-    for (var current in folder.withAncestors) {
-      var file = _getFile(current, file_paths.analysisOptionsYaml);
-      if (file != null) {
-        return file;
-      }
-    }
-    return null;
-  }
-
   /// Return the analysis options.
   ///
   /// If the [path] is not `null`, read it.
@@ -766,9 +756,9 @@
 
     File? optionsFile;
     if (!isThirdParty) {
-      optionsFile = performance.run('findOptionsFile', (_) {
+      optionsFile = performance.run('findAnalysisOptionsYamlFile', (_) {
         var folder = resourceProvider.getFile(path).parent;
-        return _findOptionsFile(folder);
+        return folder.findAnalysisOptionsYamlFile();
       });
     }
 
@@ -777,9 +767,7 @@
         try {
           var optionsProvider = AnalysisOptionsProvider(sourceFactory);
           optionMap = optionsProvider.getOptionsFromFile(optionsFile!);
-        } catch (e) {
-          // ignored
-        }
+        } catch (_) {}
       });
     } else {
       var source = performance.run('defaultOptions', (_) {
@@ -802,9 +790,7 @@
           try {
             var optionsProvider = AnalysisOptionsProvider(sourceFactory);
             optionMap = optionsProvider.getOptionsFromSource(source);
-          } catch (e) {
-            // ignored
-          }
+          } catch (_) {}
         });
       }
     }
@@ -853,11 +839,6 @@
       );
     }
   }
-
-  static File? _getFile(Folder directory, String name) {
-    var file = directory.getChildAssumingFile(name);
-    return file.exists ? file : null;
-  }
 }
 
 class FileResolverTestView {
diff --git a/pkg/analyzer/lib/src/summary2/linked_element_factory.dart b/pkg/analyzer/lib/src/summary2/linked_element_factory.dart
index 497160f..27c1357 100644
--- a/pkg/analyzer/lib/src/summary2/linked_element_factory.dart
+++ b/pkg/analyzer/lib/src/summary2/linked_element_factory.dart
@@ -101,10 +101,12 @@
 
     var reader = _libraryReaders[uri];
     if (reader == null) {
-      var libraryUriList = rootReference.children.map((e) => e.name).toList();
+      final rootChildren = rootReference.children.map((e) => e.name).toList();
       throw ArgumentError(
         'Missing library: $uri\n'
-        'Available libraries: $libraryUriList',
+        'Libraries: $uriListWithLibraryElements'
+        'Root children: $rootChildren'
+        'Readers: ${_libraryReaders.keys.toList()}',
       );
     }
 
diff --git a/pkg/analyzer/lib/src/utilities/extensions/file_system.dart b/pkg/analyzer/lib/src/utilities/extensions/file_system.dart
new file mode 100644
index 0000000..6a629b5
--- /dev/null
+++ b/pkg/analyzer/lib/src/utilities/extensions/file_system.dart
@@ -0,0 +1,31 @@
+// Copyright (c) 2022, 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.
+
+import 'package:analyzer/file_system/file_system.dart';
+import 'package:analyzer/src/util/file_paths.dart' as file_paths;
+
+extension FolderExtension on Folder {
+  /// Returns the existing analysis options file in the target, or `null`.
+  File? get existingAnalysisOptionsYamlFile {
+    return getExistingFile(file_paths.analysisOptionsYaml);
+  }
+
+  /// Return the analysis options file to be used for files in the target.
+  File? findAnalysisOptionsYamlFile() {
+    for (final current in withAncestors) {
+      final file = current.existingAnalysisOptionsYamlFile;
+      if (file != null) {
+        return file;
+      }
+    }
+    return null;
+  }
+
+  /// If the target contains an existing file with the given [name], then
+  /// returns it. Otherwise, return `null`.
+  File? getExistingFile(String name) {
+    final file = getChildAssumingFile(name);
+    return file.exists ? file : null;
+  }
+}
diff --git a/pkg/compiler/lib/src/js_backend/field_analysis.dart b/pkg/compiler/lib/src/js_backend/field_analysis.dart
index b22fb53..f2ba357 100644
--- a/pkg/compiler/lib/src/js_backend/field_analysis.dart
+++ b/pkg/compiler/lib/src/js_backend/field_analysis.dart
@@ -14,7 +14,7 @@
 import '../elements/types.dart';
 import '../ir/scope_visitor.dart';
 import '../js_model/elements.dart' show JField;
-import '../js_model/js_world_builder.dart' show JsToFrontendMap;
+import '../js_model/js_to_frontend_map.dart' show JsToFrontendMap;
 import '../kernel/element_map.dart';
 import '../kernel/kernel_strategy.dart';
 import '../kernel/kelements.dart' show KClass, KField, KConstructor;
diff --git a/pkg/compiler/lib/src/js_backend/native_data.dart b/pkg/compiler/lib/src/js_backend/native_data.dart
index 4226f5a..348af11 100644
--- a/pkg/compiler/lib/src/js_backend/native_data.dart
+++ b/pkg/compiler/lib/src/js_backend/native_data.dart
@@ -12,7 +12,7 @@
 import '../common/elements.dart' show ElementEnvironment;
 import '../elements/entities.dart';
 import '../ir/annotations.dart';
-import '../js_model/js_world_builder.dart' show identity, JsToFrontendMap;
+import '../js_model/js_to_frontend_map.dart' show identity, JsToFrontendMap;
 import '../kernel/element_map.dart';
 import '../native/behavior.dart' show NativeBehavior;
 import '../serialization/serialization_interfaces.dart';
diff --git a/pkg/compiler/lib/src/js_model/js_strategy.dart b/pkg/compiler/lib/src/js_model/js_strategy.dart
index 9b2fcd42..54a43e6 100644
--- a/pkg/compiler/lib/src/js_model/js_strategy.dart
+++ b/pkg/compiler/lib/src/js_model/js_strategy.dart
@@ -61,7 +61,7 @@
 import 'element_map.dart';
 import 'element_map_impl.dart';
 import 'js_world.dart';
-import 'js_world_builder.dart';
+import 'js_world_builder.dart' show JsClosedWorldBuilder;
 import 'locals.dart';
 
 /// JS Strategy pattern that defines the element model used in type inference
diff --git a/pkg/compiler/lib/src/js_model/js_to_frontend_map.dart b/pkg/compiler/lib/src/js_model/js_to_frontend_map.dart
new file mode 100644
index 0000000..aa5cdac
--- /dev/null
+++ b/pkg/compiler/lib/src/js_model/js_to_frontend_map.dart
@@ -0,0 +1,95 @@
+// Copyright (c) 2018, 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.
+
+import '../constants/values.dart';
+import '../elements/entities.dart';
+import '../elements/types.dart';
+
+/// Map from 'frontend' to 'backend' elements.
+///
+/// Frontend elements are what we read in, these typically represents concepts
+/// in Dart. Backend elements are what we generate, these may include elements
+/// that do not correspond to a Dart concept, such as closure classes.
+///
+/// Querying for the frontend element for a backend-only element throws an
+/// exception.
+abstract class JsToFrontendMap {
+  LibraryEntity toBackendLibrary(LibraryEntity library);
+
+  ClassEntity toBackendClass(ClassEntity cls);
+
+  /// Returns the backend member corresponding to [member]. If a member isn't
+  /// live, it doesn't have a corresponding backend member and `null` is
+  /// returned instead.
+  MemberEntity? toBackendMember(MemberEntity member);
+
+  DartType toBackendType(DartType type, {bool allowFreeVariables = false});
+
+  ConstantValue toBackendConstant(ConstantValue value,
+      {bool allowNull = false});
+
+  Set<LibraryEntity> toBackendLibrarySet(Iterable<LibraryEntity> set) {
+    return set.map(toBackendLibrary).toSet();
+  }
+
+  Set<ClassEntity> toBackendClassSet(Iterable<ClassEntity> set) {
+    // TODO(johnniwinther): Filter unused classes.
+    return set.map(toBackendClass).toSet();
+  }
+
+  Set<MemberEntity> toBackendMemberSet(Iterable<MemberEntity> set) {
+    return {
+      for (final member in set.map(toBackendMember))
+        // Members that are not live don't have a corresponding backend member.
+        if (member != null) member
+    };
+  }
+
+  Set<FieldEntity> toBackendFieldSet(Iterable<FieldEntity> set) {
+    return {
+      for (final member in set.map(toBackendMember))
+        // Members that are not live don't have a corresponding backend member.
+        if (member != null) member as FieldEntity
+    };
+  }
+
+  Set<FunctionEntity> toBackendFunctionSet(Iterable<FunctionEntity> set) {
+    return {
+      for (final member in set.map(toBackendMember))
+        // Members that are not live don't have a corresponding backend member.
+        if (member != null) member as FunctionEntity
+    };
+  }
+
+  Map<LibraryEntity, V> toBackendLibraryMap<V>(
+      Map<LibraryEntity, V> map, V convert(V value)) {
+    return convertMap(map, toBackendLibrary, convert);
+  }
+
+  Map<ClassEntity, V> toBackendClassMap<V>(
+      Map<ClassEntity, V> map, V convert(V value)) {
+    return convertMap(map, toBackendClass, convert);
+  }
+
+  Map<MemberEntity, V2> toBackendMemberMap<V1, V2>(
+      Map<MemberEntity, V1> map, V2 convert(V1 value)) {
+    return convertMap(map, toBackendMember, convert);
+  }
+}
+
+E identity<E>(E element) => element;
+
+Map<K, V2> convertMap<K, V1, V2>(
+    Map<K, V1> map, K? convertKey(K key), V2 convertValue(V1 value)) {
+  Map<K, V2> newMap = {};
+  map.forEach((K key, V1 value) {
+    K? newKey = convertKey(key);
+    V2 newValue = convertValue(value);
+    if (newKey != null && newValue != null) {
+      // Entities that are not used don't have a corresponding backend entity.
+      newMap[newKey] = newValue;
+    }
+  });
+  return newMap;
+}
diff --git a/pkg/compiler/lib/src/js_model/js_world_builder.dart b/pkg/compiler/lib/src/js_model/js_world_builder.dart
index e9b5662..7957441 100644
--- a/pkg/compiler/lib/src/js_model/js_world_builder.dart
+++ b/pkg/compiler/lib/src/js_model/js_world_builder.dart
@@ -36,6 +36,7 @@
 import 'closure.dart';
 import 'elements.dart';
 import 'element_map_impl.dart';
+import 'js_to_frontend_map.dart';
 import 'js_world.dart';
 
 class JsClosedWorldBuilder {
@@ -184,7 +185,7 @@
       rtiNeed = jRtiNeed;
     }
 
-    map.registerClosureData(closureData);
+    (map as JsToFrontendMapImpl)._registerClosureData(closureData);
 
     BackendUsage backendUsage =
         _convertBackendUsage(map, closedWorld.backendUsage);
@@ -502,107 +503,7 @@
       rtiNeed.instantiationNeedsTypeArguments(functionType, typeArgumentCount);
 }
 
-/// Map from 'frontend' to 'backend' elements.
-///
-/// Frontend elements are what we read in, these typically represents concepts
-/// in Dart. Backend elements are what we generate, these may include elements
-/// that do not correspond to a Dart concept, such as closure classes.
-///
-/// Querying for the frontend element for a backend-only element throws an
-/// exception.
-abstract class JsToFrontendMap {
-  LibraryEntity toBackendLibrary(LibraryEntity library);
-
-  ClassEntity toBackendClass(ClassEntity cls);
-
-  /// Returns the backend member corresponding to [member]. If a member isn't
-  /// live, it doesn't have a corresponding backend member and `null` is
-  /// returned instead.
-  MemberEntity toBackendMember(MemberEntity member);
-
-  DartType toBackendType(DartType type, {bool allowFreeVariables = false});
-
-  ConstantValue toBackendConstant(ConstantValue value,
-      {bool allowNull = false});
-
-  /// Register [closureData] with this map.
-  ///
-  /// [ClosureData] holds the relation between local function and the backend
-  /// entities. Before this has been registered, type variables of local
-  /// functions cannot be converted into backend equivalents.
-  void registerClosureData(ClosureData closureData);
-
-  Set<LibraryEntity> toBackendLibrarySet(Iterable<LibraryEntity> set) {
-    return set.map(toBackendLibrary).toSet();
-  }
-
-  Set<ClassEntity> toBackendClassSet(Iterable<ClassEntity> set) {
-    // TODO(johnniwinther): Filter unused classes.
-    return set.map(toBackendClass).toSet();
-  }
-
-  Set<MemberEntity> toBackendMemberSet(Iterable<MemberEntity> set) {
-    return set.map(toBackendMember).where((MemberEntity member) {
-      // Members that are not live don't have a corresponding backend member.
-      return member != null;
-    }).toSet();
-  }
-
-  Set<FieldEntity> toBackendFieldSet(Iterable<FieldEntity> set) {
-    Set<FieldEntity> newSet = Set<FieldEntity>();
-    for (FieldEntity element in set) {
-      FieldEntity backendField = toBackendMember(element);
-      if (backendField != null) {
-        // Members that are not live don't have a corresponding backend member.
-        newSet.add(backendField);
-      }
-    }
-    return newSet;
-  }
-
-  Set<FunctionEntity> toBackendFunctionSet(Iterable<FunctionEntity> set) {
-    Set<FunctionEntity> newSet = Set<FunctionEntity>();
-    for (FunctionEntity element in set) {
-      FunctionEntity backendFunction = toBackendMember(element);
-      if (backendFunction != null) {
-        // Members that are not live don't have a corresponding backend member.
-        newSet.add(backendFunction);
-      }
-    }
-    return newSet;
-  }
-
-  Map<LibraryEntity, V> toBackendLibraryMap<V>(
-      Map<LibraryEntity, V> map, V convert(V value)) {
-    return convertMap(map, toBackendLibrary, convert);
-  }
-
-  Map<ClassEntity, V> toBackendClassMap<V>(
-      Map<ClassEntity, V> map, V convert(V value)) {
-    return convertMap(map, toBackendClass, convert);
-  }
-
-  Map<MemberEntity, V2> toBackendMemberMap<V1, V2>(
-      Map<MemberEntity, V1> map, V2 convert(V1 value)) {
-    return convertMap(map, toBackendMember, convert);
-  }
-}
-
-E identity<E>(E element) => element;
-
-Map<K, V2> convertMap<K, V1, V2>(
-    Map<K, V1> map, K convertKey(K key), V2 convertValue(V1 value)) {
-  Map<K, V2> newMap = {};
-  map.forEach((K key, V1 value) {
-    K newKey = convertKey(key);
-    V2 newValue = convertValue(value);
-    if (newKey != null && newValue != null) {
-      // Entities that are not used don't have a corresponding backend entity.
-      newMap[newKey] = newValue;
-    }
-  });
-  return newMap;
-}
+// TODO(48820): Possibly move contents of js_to_frontend_map.dart back here.
 
 class JsToFrontendMapImpl extends JsToFrontendMap {
   final JsKernelToElementMap _backend;
@@ -643,8 +544,7 @@
     return _backend.members.getEntity(member.memberIndex);
   }
 
-  @override
-  void registerClosureData(ClosureData closureData) {
+  void _registerClosureData(ClosureData closureData) {
     assert(_closureData == null, "Closure data has already been registered.");
     _closureData = closureData;
   }
diff --git a/pkg/compiler/lib/src/native/behavior.dart b/pkg/compiler/lib/src/native/behavior.dart
index 545440e..3c1e721 100644
--- a/pkg/compiler/lib/src/native/behavior.dart
+++ b/pkg/compiler/lib/src/native/behavior.dart
@@ -10,8 +10,8 @@
 import '../elements/entities.dart';
 import '../elements/types.dart';
 import '../js/js.dart' as js;
-import '../js_backend/native_data.dart' show NativeBasicData;
-import '../js_model/js_world_builder.dart' show JsToFrontendMap;
+import '../js_backend/native_data_interfaces.dart' show NativeBasicData;
+import '../js_model/js_to_frontend_map.dart' show JsToFrontendMap;
 import '../options.dart';
 import '../serialization/serialization_interfaces.dart';
 import '../universe/side_effects.dart' show SideEffects;
diff --git a/pkg/dart2js_info/bin/src/convert.dart b/pkg/dart2js_info/bin/src/convert.dart
index e698029..7439957 100644
--- a/pkg/dart2js_info/bin/src/convert.dart
+++ b/pkg/dart2js_info/bin/src/convert.dart
@@ -2,8 +2,6 @@
 // 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.
 
-// @dart = 2.11
-
 import 'package:args/command_runner.dart';
 
 import 'to_json.dart' show ToJsonCommand;
diff --git a/pkg/dart2js_info/bin/src/debug_info.dart b/pkg/dart2js_info/bin/src/debug_info.dart
index 24b2298..5a237e4 100644
--- a/pkg/dart2js_info/bin/src/debug_info.dart
+++ b/pkg/dart2js_info/bin/src/debug_info.dart
@@ -2,8 +2,6 @@
 // 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.
 
-// @dart = 2.11
-
 /// Tool used mainly by dart2js developers to debug the generated info and check
 /// that it is consistent and that it covers all the data we expect it to cover.
 library dart2js_info.bin.debug_info;
@@ -29,13 +27,14 @@
 
   @override
   void run() async {
-    var args = argResults.rest;
+    final argRes = argResults!;
+    final args = argRes.rest;
     if (args.isEmpty) {
       usageException('Missing argument: info.data');
     }
 
-    var info = await infoFromFile(args.first);
-    var debugLibName = argResults['show-library'];
+    final info = await infoFromFile(args.first);
+    final debugLibName = argRes['show-library'];
 
     validateSize(info, debugLibName);
     validateParents(info);
@@ -47,14 +46,14 @@
 /// Validates that codesize of elements adds up to total codesize.
 validateSize(AllInfo info, String debugLibName) {
   // Gather data from visiting all info elements.
-  var tracker = _SizeTracker(debugLibName);
+  final tracker = _SizeTracker(debugLibName);
   info.accept(tracker);
 
   // Validate that listed elements include elements of each library.
   final listed = {...info.functions, ...info.fields};
   // For our sanity we do some validation of dump-info invariants
-  var diff1 = listed.difference(tracker.discovered);
-  var diff2 = tracker.discovered.difference(listed);
+  final diff1 = listed.difference(tracker.discovered);
+  final diff2 = tracker.discovered.difference(listed);
   if (diff1.isEmpty || diff2.isEmpty) {
     _pass('all fields and functions are covered');
   } else {
@@ -69,7 +68,7 @@
   }
 
   // Validate that code-size adds up.
-  int realTotal = info.program.size;
+  final realTotal = info.program!.size;
   int totalLib = info.libraries.fold(0, (n, lib) => n + lib.size);
   int constantsSize = info.constants.fold(0, (n, c) => n + c.size);
   int accounted = totalLib + constantsSize;
@@ -114,7 +113,7 @@
 
 class _SizeTracker extends RecursiveInfoVisitor {
   /// A library name for which to print debugging information (if not null).
-  final String _debugLibName;
+  final String? _debugLibName;
 
   _SizeTracker(this._debugLibName);
 
@@ -141,7 +140,7 @@
 
   void _push() => stack.add(_State());
 
-  void _pop(info) {
+  void _pop(Info info) {
     var last = stack.removeLast();
     var size = last._totalSize;
     if (size > info.size) {
@@ -162,7 +161,7 @@
   bool _debug = false;
   @override
   visitLibrary(LibraryInfo info) {
-    if (_debugLibName != null) _debug = info.name.contains(_debugLibName);
+    if (_debugLibName != null) _debug = info.name.contains(_debugLibName!);
     _push();
     if (_debug) {
       _debugCode.write('{\n');
@@ -204,8 +203,8 @@
         _debugCode.write('},\n');
       }
     }
-    stack.last._totalSize += info.size;
-    stack.last._bodySize += info.size;
+    stack.last._totalSize += (info.size as int);
+    stack.last._bodySize += (info.size as int);
     stack.last._count++;
   }
 
@@ -282,7 +281,7 @@
     }
     g2.addNode(f);
     if (info.dependencies[f] != null) {
-      for (var g in info.dependencies[f]) {
+      for (var g in info.dependencies[f]!) {
         g2.addEdge(f, g);
       }
     }
@@ -295,7 +294,7 @@
     }
     g2.addNode(f);
     if (info.dependencies[f] != null) {
-      for (var g in info.dependencies[f]) {
+      for (var g in info.dependencies[f]!) {
         g2.addEdge(f, g);
       }
     }
@@ -327,7 +326,7 @@
 // graph.
 verifyDeps(AllInfo info) {
   var graph = graphFromInfo(info);
-  var entrypoint = info.program.entrypoint;
+  var entrypoint = info.program!.entrypoint;
   var reachables = Set.from(graph.preOrder(entrypoint));
 
   var functionsAndFields = <BasicInfo>[...info.functions, ...info.fields];
diff --git a/pkg/dart2js_info/bin/src/deferred_library_layout.dart b/pkg/dart2js_info/bin/src/deferred_library_layout.dart
index 7dc279a..0e3416b 100644
--- a/pkg/dart2js_info/bin/src/deferred_library_layout.dart
+++ b/pkg/dart2js_info/bin/src/deferred_library_layout.dart
@@ -2,8 +2,6 @@
 // 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.
 
-// @dart = 2.11
-
 /// This tool reports how code is divided among deferred chunks.
 library dart2js_info.bin.deferred_library_layout;
 
@@ -24,7 +22,7 @@
 
   @override
   void run() async {
-    var args = argResults.rest;
+    final args = argResults!.rest;
     if (args.isEmpty) {
       usageException('Missing argument: info.data');
     }
@@ -38,8 +36,8 @@
   Map<OutputUnitInfo, Map<LibraryInfo, List<BasicInfo>>> hunkMembers = {};
   Map<LibraryInfo, Set<OutputUnitInfo>> libToHunks = {};
   void register(BasicInfo info) {
-    var unit = info.outputUnit;
-    var lib = _libOf(info);
+    final unit = info.outputUnit!;
+    final lib = _libOf(info);
     if (lib == null) return;
     libToHunks.putIfAbsent(lib, () => <OutputUnitInfo>{}).add(unit);
     hunkMembers
@@ -54,10 +52,10 @@
   info.fields.forEach(register);
   info.closures.forEach(register);
 
-  var dir = Directory.current.path;
+  final dir = Directory.current.path;
   hunkMembers.forEach((unit, map) {
-    print('Output unit ${unit.name ?? "main"}:');
-    if (unit.name == null || unit.name == 'main') {
+    print('Output unit ${unit.name}:');
+    if (unit.name == 'main') {
       print('  loaded by default');
     } else {
       print('  loaded by importing: ${unit.imports}');
@@ -65,18 +63,18 @@
 
     print('  contains:');
     map.forEach((lib, elements) {
-      var uri = lib.uri;
-      var shortUri = (uri.isScheme('file') && uri.path.startsWith(dir))
+      final uri = lib.uri;
+      final shortUri = (uri.isScheme('file') && uri.path.startsWith(dir))
           ? uri.path.substring(dir.length + 1)
           : '$uri';
 
       // If the entire library is in one chunk, just report the library name
       // otherwise report which functions are on this chunk.
-      if (libToHunks[lib].length == 1) {
+      if (libToHunks[lib]!.length == 1) {
         print('     - $shortUri');
       } else {
         print('     - $shortUri:');
-        for (var e in elements) {
+        for (final e in elements) {
           print('       - ${kindToString(e.kind)} ${e.name}');
         }
       }
diff --git a/pkg/dart2js_info/bin/src/deferred_library_size.dart b/pkg/dart2js_info/bin/src/deferred_library_size.dart
index 78f94c9..6cf0ceb 100644
--- a/pkg/dart2js_info/bin/src/deferred_library_size.dart
+++ b/pkg/dart2js_info/bin/src/deferred_library_size.dart
@@ -2,8 +2,6 @@
 // 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.
 
-// @dart = 2.11
-
 /// This tool gives a breakdown of code size by deferred part in the program.
 library dart2js_info.bin.deferred_library_size;
 
@@ -25,14 +23,14 @@
 
   @override
   void run() async {
-    var args = argResults.rest;
+    final args = argResults!.rest;
     if (args.isEmpty) {
       usageException('Missing argument: info.data');
     }
     // TODO(het): Would be faster to only parse the 'outputUnits' part
-    var info = await infoFromFile(args.first);
-    var sizeByImport = getSizeByImport(info);
-    printSizes(sizeByImport, info.program.size);
+    final info = await infoFromFile(args.first);
+    final sizeByImport = getSizeByImport(info);
+    printSizes(sizeByImport, info.program!.size);
   }
 }
 
@@ -49,7 +47,7 @@
 }
 
 void printSizes(Map<String, int> sizeByImport, int programSize) {
-  var importSizes = <ImportSize>[];
+  final importSizes = <ImportSize>[];
   sizeByImport.forEach((import, size) {
     importSizes.add(ImportSize(import, size));
   });
@@ -72,9 +70,9 @@
   }
   print('-' * (longest + 16));
 
-  var mainChunkSize = sizeByImport['main'];
-  var deferredSize = programSize - mainChunkSize;
-  var percentDeferred = (deferredSize * 100 / programSize).toStringAsFixed(2);
+  final mainChunkSize = sizeByImport['main']!;
+  final deferredSize = programSize - mainChunkSize;
+  final percentDeferred = (deferredSize * 100 / programSize).toStringAsFixed(2);
   printRow('Main chunk size', mainChunkSize);
   printRow('Deferred code size', deferredSize);
   printRow('Percent of code deferred', '$percentDeferred%');
@@ -82,13 +80,13 @@
 
 Map<String, int> getSizeByImport(AllInfo info) {
   var sizeByImport = <String, int>{};
-  for (var outputUnit in info.outputUnits) {
-    if (outputUnit.name == 'main' || outputUnit.name == null) {
+  for (final outputUnit in info.outputUnits) {
+    if (outputUnit.name == 'main') {
       sizeByImport['main'] = outputUnit.size;
     } else {
-      for (var import in outputUnit.imports) {
-        sizeByImport.putIfAbsent(import, () => 0);
-        sizeByImport[import] += outputUnit.size;
+      for (final import in outputUnit.imports) {
+        sizeByImport.update(import, (value) => value + outputUnit.size,
+            ifAbsent: () => outputUnit.size);
       }
     }
   }
diff --git a/pkg/dart2js_info/bin/src/diff.dart b/pkg/dart2js_info/bin/src/diff.dart
index dfa4b34..405009f 100644
--- a/pkg/dart2js_info/bin/src/diff.dart
+++ b/pkg/dart2js_info/bin/src/diff.dart
@@ -2,8 +2,6 @@
 // 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.
 
-// @dart = 2.11
-
 import 'package:args/command_runner.dart';
 
 import 'package:dart2js_info/info.dart';
@@ -29,24 +27,25 @@
 
   @override
   void run() async {
-    var args = argResults.rest;
+    final argRes = argResults!;
+    var args = argRes.rest;
     if (args.length < 2) {
       usageException(
           'Missing arguments, expected two dump-info files to compare');
     }
 
-    var oldInfo = await infoFromFile(args[0]);
-    var newInfo = await infoFromFile(args[1]);
-    var summaryOnly = argResults['summary-only'];
+    final oldInfo = await infoFromFile(args[0]);
+    final newInfo = await infoFromFile(args[1]);
+    final summaryOnly = argRes['summary-only'];
 
-    var diffs = diff(oldInfo, newInfo);
+    final diffs = diff(oldInfo, newInfo);
 
     // Categorize the diffs
-    var adds = <AddDiff>[];
-    var removals = <RemoveDiff>[];
-    var sizeChanges = <SizeDiff>[];
-    var becameDeferred = <DeferredStatusDiff>[];
-    var becameUndeferred = <DeferredStatusDiff>[];
+    final adds = <AddDiff>[];
+    final removals = <RemoveDiff>[];
+    final sizeChanges = <SizeDiff>[];
+    final becameDeferred = <DeferredStatusDiff>[];
+    final becameUndeferred = <DeferredStatusDiff>[];
 
     for (var diff in diffs) {
       switch (diff.kind) {
@@ -125,7 +124,7 @@
     List<DeferredStatusDiff> becameDeferred,
     List<DeferredStatusDiff> becameUndeferred,
     Map<List<Diff>, int> totalSizes) {
-  var overallSizeDiff = newInfo.program.size - oldInfo.program.size;
+  var overallSizeDiff = newInfo.program!.size - oldInfo.program!.size;
   print('total_size_difference $overallSizeDiff');
 
   print('total_added ${totalSizes[adds]}');
@@ -181,7 +180,7 @@
   }
 }
 
-void _section(String title, {int size}) {
+void _section(String title, {int? size}) {
   print('$title ($size bytes)');
   print('=' * 72);
 }
diff --git a/pkg/dart2js_info/bin/src/function_size_analysis.dart b/pkg/dart2js_info/bin/src/function_size_analysis.dart
index a856f2e..04aa819 100644
--- a/pkg/dart2js_info/bin/src/function_size_analysis.dart
+++ b/pkg/dart2js_info/bin/src/function_size_analysis.dart
@@ -2,8 +2,6 @@
 // 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.
 
-// @dart = 2.11
-
 /// Tool presenting how much each function contributes to the total code.
 library compiler.tool.function_size_analysis;
 
@@ -26,18 +24,18 @@
 
   @override
   void run() async {
-    var args = argResults.rest;
+    final args = argResults!.rest;
     if (args.isEmpty) {
       usageException('Missing argument: info.data');
     }
-    var info = await infoFromFile(args.first);
+    final info = await infoFromFile(args.first);
     showCodeDistribution(info);
   }
 }
 
 showCodeDistribution(AllInfo info,
-    {bool Function(Info info) filter, bool showLibrarySizes = false}) {
-  var realTotal = info.program.size;
+    {bool Function(Info info)? filter, bool showLibrarySizes = false}) {
+  var realTotal = info.program!.size;
   filter ??= (i) => true;
   var reported = <BasicInfo>[
     ...info.functions.where(filter),
@@ -78,7 +76,7 @@
   var mainMethod = info.functions.firstWhere((f) => f.name == 'main');
   var dominatorTree = graph.dominatorTree(mainMethod);
   var dominatedSize = {};
-  helper(n) {
+  int helper(n) {
     int size = n.size;
     assert(!dominatedSize.containsKey(n));
     dominatedSize[n] = 0;
@@ -103,21 +101,21 @@
     var longest = 0;
     for (var info in reported) {
       var size = info.size;
-      while (info != null && info is! LibraryInfo) {
-        info = info.parent;
+      Info? lib = info;
+      while (lib != null && lib is! LibraryInfo) {
+        lib = lib.parent;
       }
-      if (info == null) return;
-      LibraryInfo lib = info;
-      totals.putIfAbsent(lib, () => 0);
-      totals[lib] += size;
+      if (lib == null) return;
+      totals.update(lib as LibraryInfo, (value) => value + size,
+          ifAbsent: () => size);
       longest = math.max(longest, '${lib.uri}'.length);
     }
 
     _showLibHeader(longest + 1);
     var reportedByLibrary = totals.keys.toList();
-    reportedByLibrary.sort((a, b) => totals[b] - totals[a]);
-    for (var info in reportedByLibrary) {
-      _showLib('${info.uri}', totals[info], realTotal, longest + 1);
+    reportedByLibrary.sort((a, b) => totals[b]! - totals[a]!);
+    for (final info in reportedByLibrary) {
+      _showLib('${info.uri}', totals[info]!, realTotal, longest + 1);
     }
   }
 
@@ -135,27 +133,22 @@
 /// Data associated with an SCC. Used to compute the reachable code size.
 class _SccData {
   int size = 0;
-  Set deps = {};
+  Set<_SccData> deps = {};
   _SccData();
 
-  int _maxSize;
-  int get maxSize {
-    compute();
-    return _maxSize;
-  }
+  late final int maxSize = computeMaxSize();
 
-  void compute() {
-    if (_maxSize != null) return;
+  int computeMaxSize() {
     var max = 0;
-    var seen = <dynamic>{};
-    helper(n) {
+    var seen = <_SccData>{};
+    void helper(_SccData n) {
       if (!seen.add(n)) return;
       max += n.size;
       n.deps.forEach(helper);
     }
 
     helper(this);
-    _maxSize = max;
+    return max;
   }
 }
 
diff --git a/pkg/dart2js_info/bin/src/inject_text.dart b/pkg/dart2js_info/bin/src/inject_text.dart
index ea245ad..045f7b3 100644
--- a/pkg/dart2js_info/bin/src/inject_text.dart
+++ b/pkg/dart2js_info/bin/src/inject_text.dart
@@ -2,8 +2,6 @@
 // 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.
 
-// @dart = 2.11
-
 import 'dart:io';
 
 import 'package:dart2js_info/info.dart';
@@ -18,17 +16,17 @@
   // produces code spans, but excludes the orignal text
   for (var f in info.functions) {
     for (var span in f.code) {
-      _fillSpan(span, f.outputUnit);
+      _fillSpan(span, f.outputUnit!);
     }
   }
   for (var f in info.fields) {
     for (var span in f.code) {
-      _fillSpan(span, f.outputUnit);
+      _fillSpan(span, f.outputUnit!);
     }
   }
   for (var c in info.constants) {
     for (var span in c.code) {
-      _fillSpan(span, c.outputUnit);
+      _fillSpan(span, c.outputUnit!);
     }
   }
 }
diff --git a/pkg/dart2js_info/bin/src/library_size_split.dart b/pkg/dart2js_info/bin/src/library_size_split.dart
index a4e2483..8a1e77a 100644
--- a/pkg/dart2js_info/bin/src/library_size_split.dart
+++ b/pkg/dart2js_info/bin/src/library_size_split.dart
@@ -2,8 +2,6 @@
 // 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.
 
-// @dart = 2.11
-
 /// Command-line tool to show the size distribution of generated code among
 /// libraries. Libraries can be grouped using regular expressions. You can
 /// specify what regular expressions to use by providing a `grouping.yaml` file.
@@ -86,30 +84,31 @@
 
   @override
   void run() async {
-    var args = argResults.rest;
+    final argRes = argResults!;
+    final args = argRes.rest;
     if (args.isEmpty) {
       usageException('Missing argument: info.data');
     }
 
-    var info = await infoFromFile(args.first);
+    final info = await infoFromFile(args.first);
 
-    var groupingFile = argResults['grouping'];
-    var groupingText = groupingFile != null
+    final groupingFile = argRes['grouping'];
+    final groupingText = groupingFile != null
         ? File(groupingFile).readAsStringSync()
         : defaultGrouping;
-    var groupingYaml = loadYaml(groupingText);
-    var groups = [];
+    final groupingYaml = loadYaml(groupingText);
+    final groups = [];
     for (var group in groupingYaml['groups']) {
       groups.add(_Group(
           group['name'], RegExp(group['regexp']), group['cluster'] ?? 0));
     }
 
-    var sizes = {};
+    final sizes = {};
     var allLibs = 0;
     for (LibraryInfo lib in info.libraries) {
       allLibs += lib.size;
       for (var group in groups) {
-        var match = group.matcher.firstMatch('${lib.uri}');
+        final match = group.matcher.firstMatch('${lib.uri}');
         if (match != null) {
           var name = group.name;
           if (name == null && match.groupCount > 0) name = match.group(1);
@@ -125,11 +124,11 @@
       allConstants += constant.size;
     }
 
-    var all = sizes.keys.toList();
+    final all = sizes.keys.toList();
     all.sort((a, b) => sizes[a].compareTo(sizes[b]));
-    var realTotal = info.program.size;
+    final realTotal = info.program!.size;
     var longest = 0;
-    var rows = <_Row>[];
+    final rows = <_Row>[];
     addRow(String label, int value) {
       rows.add(_Row(label, value));
       longest = max(longest, label.length);
@@ -150,12 +149,12 @@
 
     var lastCluster = 0;
     for (var name in all) {
-      var entry = sizes[name];
+      final entry = sizes[name];
       if (lastCluster < entry.cluster) {
         rows.add(const _Divider());
         lastCluster = entry.cluster;
       }
-      var size = entry.size;
+      final size = entry.size;
       addRow(name, size);
     }
     rows.add(const _Divider());
@@ -207,7 +206,7 @@
 }
 
 _pad(value, n, {bool right = false}) {
-  var s = '$value';
+  final s = '$value';
   if (s.length >= n) return s;
   var pad = ' ' * (n - s.length);
   return right ? '$s$pad' : '$pad$s';
diff --git a/pkg/dart2js_info/bin/src/live_code_size_analysis.dart b/pkg/dart2js_info/bin/src/live_code_size_analysis.dart
index 3e02b7a..2a4d135 100644
--- a/pkg/dart2js_info/bin/src/live_code_size_analysis.dart
+++ b/pkg/dart2js_info/bin/src/live_code_size_analysis.dart
@@ -2,8 +2,6 @@
 // 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.
 
-// @dart = 2.11
-
 /// Command-line tool presenting combined information from dump-info and
 /// coverage data.
 ///
@@ -62,11 +60,12 @@
 
   @override
   void run() async {
-    var args = argResults.rest;
+    final argRes = argResults!;
+    var args = argRes.rest;
     if (args.length < 2) {
       usageException('Missing arguments, expected: info.data coverage.json');
     }
-    await _liveCodeAnalysis(args[0], args[1], argResults['verbose']);
+    await _liveCodeAnalysis(args[0], args[1], argRes['verbose']);
   }
 }
 
@@ -74,7 +73,7 @@
   var info = await infoFromFile(infoFile);
   var coverage = jsonDecode(File(coverageFile).readAsStringSync());
 
-  int realTotal = info.program.size;
+  int realTotal = info.program!.size;
   int totalLib = info.libraries.fold(0, (n, lib) => n + lib.size);
 
   int totalCode = 0;
diff --git a/pkg/dart2js_info/bin/src/runtime_coverage_analysis.dart b/pkg/dart2js_info/bin/src/runtime_coverage_analysis.dart
index 6f8183f..bef9247 100644
--- a/pkg/dart2js_info/bin/src/runtime_coverage_analysis.dart
+++ b/pkg/dart2js_info/bin/src/runtime_coverage_analysis.dart
@@ -2,8 +2,6 @@
 // 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.
 
-// @dart = 2.11
-
 /// Command-line tool presenting combined information from dump-info and
 /// runtime coverage data.
 ///
@@ -55,11 +53,12 @@
 
   @override
   void run() async {
-    var args = argResults.rest;
+    final argRes = argResults!;
+    final args = argRes.rest;
     if (args.length < 2) {
       usageException('Missing arguments, expected: info.data coverage.json');
     }
-    var showPackages = argResults['show-packages'];
+    final showPackages = argRes['show-packages'];
     if (showPackages) {
       await _reportWithPackages(args[0], args[1]);
     } else {
@@ -77,7 +76,7 @@
   // The value associated with each coverage item isn't used for now.
   var coverage = coverageRaw.keys.toSet();
 
-  int totalProgramSize = info.program.size;
+  int totalProgramSize = info.program!.size;
   int totalLibSize = info.libraries.fold(0, (n, lib) => n + lib.size);
 
   int totalCode = 0;
@@ -130,13 +129,13 @@
   // The value associated with each coverage item isn't used for now.
   var coverage = coverageRaw.keys.toSet();
 
-  int totalProgramSize = info.program.size;
+  int totalProgramSize = info.program!.size;
   int totalLibSize = info.libraries.fold(0, (n, lib) => n + lib.size);
 
   int totalCode = 0;
   int usedCode = 0;
-  var packageData = <String, PackageInfo>{};
-  var unused = PriorityQueue<Info>((a, b) => b.size.compareTo(a.size));
+  final packageData = <String?, PackageInfo>{};
+  final unused = PriorityQueue<Info>((a, b) => b.size.compareTo(a.size));
 
   void tallyCode(BasicInfo i) {
     totalCode += i.size;
@@ -144,8 +143,7 @@
     var used = coverage.contains(name);
 
     var groupName = libraryGroupName(i);
-    packageData.putIfAbsent(groupName, () => PackageInfo());
-    packageData[groupName].add(i, used: used);
+    (packageData[groupName] ??= PackageInfo()).add(i, used: used);
 
     if (used) {
       usedCode += i.size;
@@ -218,7 +216,7 @@
       var name = qualifiedName(item);
       var used = coverage.contains(name);
       var usedTick = used ? '+' : '-';
-      var mainUnitTick = item.outputUnit.name == 'main' ? 'M' : 'D';
+      var mainUnitTick = item.outputUnit!.name == 'main' ? 'M' : 'D';
       _leftPadded('    [$usedTick$mainUnitTick] ${qualifiedName(item)}:',
           '${item.size} bytes ($percent% of package)');
     }
@@ -227,7 +225,7 @@
   }
 }
 
-void _section(String title, {int size}) {
+void _section(String title, {int? size}) {
   if (size == null) {
     print(title);
   } else {
@@ -268,7 +266,7 @@
     } else {
       unusedSize += i.size;
     }
-    if (i.outputUnit.name == 'main') {
+    if (i.outputUnit!.name == 'main') {
       mainUnitSize += i.size;
       if (!used) {
         unusedMainUnitSize += i.size;
diff --git a/pkg/dart2js_info/bin/src/text_print.dart b/pkg/dart2js_info/bin/src/text_print.dart
index 95ad015..ad6158b 100644
--- a/pkg/dart2js_info/bin/src/text_print.dart
+++ b/pkg/dart2js_info/bin/src/text_print.dart
@@ -2,8 +2,6 @@
 // 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.
 
-// @dart = 2.11
-
 import 'dart:io';
 
 import 'package:args/command_runner.dart';
@@ -34,17 +32,18 @@
 
   @override
   void run() async {
-    if (argResults.rest.isEmpty) {
+    final argRes = argResults!;
+    if (argRes.rest.isEmpty) {
       usageException('Missing argument: <input-info>');
     }
 
-    String filename = argResults.rest[0];
+    String filename = argRes.rest[0];
     AllInfo info = await infoFromFile(filename);
-    if (argResults['inject-text']) injectText(info);
+    if (argRes['inject-text']) injectText(info);
 
-    var buffer = StringBuffer();
-    info.accept(TextPrinter(buffer, argResults['inject-text']));
-    var outputPath = argResults['out'];
+    final buffer = StringBuffer();
+    info.accept(TextPrinter(buffer, argRes['inject-text']));
+    final outputPath = argRes['out'];
     if (outputPath == null) {
       print(buffer);
     } else {
@@ -79,7 +78,7 @@
 
   @override
   void visitAll(AllInfo info) {
-    _writeBlock("Summary data", () => visitProgram(info.program));
+    _writeBlock("Summary data", () => visitProgram(info.program!));
     buffer.writeln();
     _writeBlock("Libraries", () => info.libraries.forEach(visitLibrary));
     // Note: classes, functions, typedefs, and fields are group;ed by library.
@@ -146,7 +145,7 @@
   @override
   void visitClass(ClassInfo info) {
     _writeBlock(
-        '${info.name}: ${_size(info.size)} [${info.outputUnit.filename}]', () {
+        '${info.name}: ${_size(info.size)} [${info.outputUnit?.filename}]', () {
       if (info.functions.isNotEmpty) {
         _writeBlock('Methods:', () => info.functions.forEach(visitFunction));
       }
@@ -160,7 +159,7 @@
   @override
   void visitClassType(ClassTypeInfo info) {
     _writeBlock(
-        '${info.name}: ${_size(info.size)} [${info.outputUnit.filename}]',
+        '${info.name}: ${_size(info.size)} [${info.outputUnit?.filename}]',
         () {});
   }
 
@@ -182,7 +181,7 @@
   void visitFunction(FunctionInfo info) {
     var outputUnitFile = '';
     if (info.functionKind == FunctionInfo.TOP_LEVEL_FUNCTION_KIND) {
-      outputUnitFile = ' [${info.outputUnit.filename}]';
+      outputUnitFile = ' [${info.outputUnit?.filename}]';
     }
     String params =
         info.parameters.map((p) => "${p.declaredType} ${p.name}").join(', ');
diff --git a/pkg/dart2js_info/bin/src/to_binary.dart b/pkg/dart2js_info/bin/src/to_binary.dart
index 3061c3e..2f97835 100644
--- a/pkg/dart2js_info/bin/src/to_binary.dart
+++ b/pkg/dart2js_info/bin/src/to_binary.dart
@@ -2,8 +2,6 @@
 // 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.
 
-// @dart = 2.11
-
 import 'dart:io';
 
 import 'package:args/command_runner.dart';
@@ -24,14 +22,15 @@
 
   @override
   void run() async {
-    if (argResults.rest.isEmpty) {
+    final args = argResults!;
+    if (args.rest.isEmpty) {
       usageException('Missing argument: <input-info>');
     }
 
-    String filename = argResults.rest[0];
+    String filename = args.rest[0];
     AllInfo info = await infoFromFile(filename);
-    if (argResults['inject-text']) injectText(info);
-    String outputFilename = argResults['out'] ?? '$filename.data';
+    if (args['inject-text']) injectText(info);
+    String outputFilename = args['out'] ?? '$filename.data';
     var outstream = File(outputFilename).openWrite();
     binary.encode(info, outstream);
     await outstream.done;
diff --git a/pkg/dart2js_info/bin/src/to_json.dart b/pkg/dart2js_info/bin/src/to_json.dart
index 38a909c..2e6b117 100644
--- a/pkg/dart2js_info/bin/src/to_json.dart
+++ b/pkg/dart2js_info/bin/src/to_json.dart
@@ -2,8 +2,6 @@
 // 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.
 
-// @dart = 2.11
-
 import 'dart:io';
 import 'dart:convert';
 
@@ -38,21 +36,22 @@
 
   @override
   void run() async {
-    if (argResults.rest.isEmpty) {
+    final args = argResults!;
+    if (args.rest.isEmpty) {
       usageException('Missing argument: <input-info>');
     }
 
-    String filename = argResults.rest[0];
-    bool isBackwardCompatible = argResults['compat-mode'];
+    String filename = args.rest[0];
+    bool isBackwardCompatible = args['compat-mode'];
     AllInfo info = await infoFromFile(filename);
 
-    if (isBackwardCompatible || argResults['inject-text']) {
+    if (isBackwardCompatible || args['inject-text']) {
       injectText(info);
     }
 
     var json = AllInfoJsonCodec(isBackwardCompatible: isBackwardCompatible)
         .encode(info);
-    String outputFilename = argResults['out'] ?? '$filename.json';
+    String outputFilename = args['out'] ?? '$filename.json';
     File(outputFilename)
         .writeAsStringSync(const JsonEncoder.withIndent("  ").convert(json));
   }
diff --git a/pkg/dart2js_info/bin/src/to_proto.dart b/pkg/dart2js_info/bin/src/to_proto.dart
index 89ed41d..86112ef 100644
--- a/pkg/dart2js_info/bin/src/to_proto.dart
+++ b/pkg/dart2js_info/bin/src/to_proto.dart
@@ -2,8 +2,6 @@
 // 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.
 
-// @dart = 2.11
-
 /// Command-line tool to convert an info.json file ouputted by dart2js to the
 /// alternative protobuf format.
 
@@ -26,15 +24,16 @@
 
   @override
   void run() async {
-    if (argResults.rest.isEmpty) {
+    final args = argResults!;
+    if (args.rest.isEmpty) {
       usageException('Missing argument: <input-info>');
     }
 
-    String filename = argResults.rest[0];
+    String filename = args.rest[0];
     final info = await infoFromFile(filename);
-    if (argResults['inject-text']) injectText(info);
+    if (args['inject-text']) injectText(info);
     final proto = AllInfoProtoCodec().encode(info);
-    String outputFilename = argResults['out'] ?? '$filename.pb';
+    String outputFilename = args['out'] ?? '$filename.pb';
     final outputFile = File(outputFilename);
     await outputFile.writeAsBytes(proto.writeToBuffer(), mode: FileMode.write);
   }
diff --git a/pkg/dart2js_info/bin/tools.dart b/pkg/dart2js_info/bin/tools.dart
index 785e00c..7dc64bd 100644
--- a/pkg/dart2js_info/bin/tools.dart
+++ b/pkg/dart2js_info/bin/tools.dart
@@ -2,8 +2,6 @@
 // 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.
 
-// @dart = 2.11
-
 import 'package:args/command_runner.dart';
 
 import 'src/code_deps.dart';
diff --git a/pkg/dart2js_info/test/binary_serialization_test.dart b/pkg/dart2js_info/test/binary_serialization_test.dart
index 27ac31a..842b212 100644
--- a/pkg/dart2js_info/test/binary_serialization_test.dart
+++ b/pkg/dart2js_info/test/binary_serialization_test.dart
@@ -2,8 +2,6 @@
 // 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.
 
-// @dart = 2.11
-
 import 'dart:convert';
 import 'dart:io' show File, Platform;
 import 'dart:typed_data' show BytesBuilder;
diff --git a/pkg/dart2js_info/test/graph_test.dart b/pkg/dart2js_info/test/graph_test.dart
index 017a90e..71afc23 100644
--- a/pkg/dart2js_info/test/graph_test.dart
+++ b/pkg/dart2js_info/test/graph_test.dart
@@ -2,8 +2,6 @@
 // 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.
 
-// @dart = 2.11
-
 import 'package:dart2js_info/src/graph.dart';
 import 'package:test/test.dart';
 
diff --git a/pkg/dart2js_info/test/json_to_proto_deferred_test.dart b/pkg/dart2js_info/test/json_to_proto_deferred_test.dart
index 190b005..d88c036 100644
--- a/pkg/dart2js_info/test/json_to_proto_deferred_test.dart
+++ b/pkg/dart2js_info/test/json_to_proto_deferred_test.dart
@@ -2,8 +2,6 @@
 // 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.
 
-// @dart = 2.11
-
 import 'dart:convert';
 import 'dart:io';
 
@@ -35,14 +33,14 @@
 
       final entrypoint = infoMap[proto.program.entrypointId];
       expect(entrypoint, isNotNull);
-      expect(entrypoint.hasFunctionInfo(), isTrue);
+      expect(entrypoint!.hasFunctionInfo(), isTrue);
       expect(entrypoint.outputUnitId, isNotNull);
 
       // The output unit of the entrypoint function should be the default
       // entrypoint, which should have no imports.
       final defaultOutputUnit = infoMap[entrypoint.outputUnitId];
       expect(defaultOutputUnit, isNotNull);
-      expect(defaultOutputUnit.hasOutputUnitInfo(), isTrue);
+      expect(defaultOutputUnit!.hasOutputUnitInfo(), isTrue);
       expect(defaultOutputUnit.outputUnitInfo.imports, isEmpty);
     });
   });
diff --git a/pkg/dart2js_info/test/json_to_proto_test.dart b/pkg/dart2js_info/test/json_to_proto_test.dart
index 6579ea9..240f3c2 100644
--- a/pkg/dart2js_info/test/json_to_proto_test.dart
+++ b/pkg/dart2js_info/test/json_to_proto_test.dart
@@ -2,8 +2,6 @@
 // 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.
 
-// @dart = 2.11
-
 import 'dart:convert';
 import 'dart:io';
 
@@ -49,31 +47,31 @@
         final value = info.value;
         if (value.hasLibraryInfo()) {
           expect(value.serializedId,
-              startsWith(expectedPrefixes[InfoKind.library]));
+              startsWith(expectedPrefixes[InfoKind.library]!));
         } else if (value.hasClassInfo()) {
-          expect(
-              value.serializedId, startsWith(expectedPrefixes[InfoKind.clazz]));
+          expect(value.serializedId,
+              startsWith(expectedPrefixes[InfoKind.clazz]!));
         } else if (value.hasClassTypeInfo()) {
           expect(value.serializedId,
-              startsWith(expectedPrefixes[InfoKind.classType]));
+              startsWith(expectedPrefixes[InfoKind.classType]!));
         } else if (value.hasFunctionInfo()) {
           expect(value.serializedId,
-              startsWith(expectedPrefixes[InfoKind.function]));
+              startsWith(expectedPrefixes[InfoKind.function]!));
         } else if (value.hasFieldInfo()) {
-          expect(
-              value.serializedId, startsWith(expectedPrefixes[InfoKind.field]));
+          expect(value.serializedId,
+              startsWith(expectedPrefixes[InfoKind.field]!));
         } else if (value.hasConstantInfo()) {
           expect(value.serializedId,
-              startsWith(expectedPrefixes[InfoKind.constant]));
+              startsWith(expectedPrefixes[InfoKind.constant]!));
         } else if (value.hasOutputUnitInfo()) {
           expect(value.serializedId,
-              startsWith(expectedPrefixes[InfoKind.outputUnit]));
+              startsWith(expectedPrefixes[InfoKind.outputUnit]!));
         } else if (value.hasTypedefInfo()) {
           expect(value.serializedId,
-              startsWith(expectedPrefixes[InfoKind.typedef]));
+              startsWith(expectedPrefixes[InfoKind.typedef]!));
         } else if (value.hasClosureInfo()) {
           expect(value.serializedId,
-              startsWith(expectedPrefixes[InfoKind.closure]));
+              startsWith(expectedPrefixes[InfoKind.closure]!));
         }
       }
     });
diff --git a/pkg/dart2js_info/test/parse_test.dart b/pkg/dart2js_info/test/parse_test.dart
index bb80faf..92c34d0 100644
--- a/pkg/dart2js_info/test/parse_test.dart
+++ b/pkg/dart2js_info/test/parse_test.dart
@@ -2,8 +2,6 @@
 // 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.
 
-// @dart = 2.11
-
 import 'dart:convert';
 import 'dart:io';
 
@@ -18,10 +16,10 @@
       var json = jsonDecode(helloWorld.readAsStringSync());
       var decoded = AllInfoJsonCodec().decode(json);
 
-      var program = decoded.program;
+      final program = decoded.program;
       expect(program, isNotNull);
 
-      expect(program.entrypoint, isNotNull);
+      expect(program!.entrypoint, isNotNull);
       expect(program.size, 90362);
       expect(program.compilationMoment,
           DateTime.parse("2022-05-26 21:08:43.608041"));
diff --git a/pkg/vm/lib/target/flutter.dart b/pkg/vm/lib/target/flutter.dart
index 1eadf20..8bdde3d 100644
--- a/pkg/vm/lib/target/flutter.dart
+++ b/pkg/vm/lib/target/flutter.dart
@@ -50,6 +50,10 @@
   List<String> get extraRequiredLibrariesPlatform => const <String>[];
 
   @override
+  DartLibrarySupport get dartLibrarySupport =>
+      const CustomizedDartLibrarySupport(unsupported: {'mirrors'});
+
+  @override
   void performPreConstantEvaluationTransformations(
       Component component,
       CoreTypes coreTypes,
diff --git a/tools/VERSION b/tools/VERSION
index 6f615bc..a78b64c 100644
--- a/tools/VERSION
+++ b/tools/VERSION
@@ -27,5 +27,5 @@
 MAJOR 2
 MINOR 18
 PATCH 0
-PRERELEASE 204
+PRERELEASE 205
 PRERELEASE_PATCH 0
\ No newline at end of file