[package:js] Add @trustTypes annotation.

Adds an experimental `@trustTypes` annotation which can be used during
migration to static interop to preserve the older semantics for JS interop.

Change-Id: Ic00a6c968b15f8c8f5d0840b82db5a6670eaf0eb
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/241362
Reviewed-by: Riley Porter <rileyporter@google.com>
Reviewed-by: Srujan Gaddam <srujzs@google.com>
Reviewed-by: Johnni Winther <johnniwinther@google.com>
Commit-Queue: Joshua Litt <joshualitt@google.com>

pkg/_fe_analyzer_shared/lib/src/messages/codes_generated.dart

@@ -7022,6 +7022,67 @@ const MessageCode messageJsInteropOperatorsNotSupported = const MessageCode(
     problemMessage: r"""JS interop classes do not support operator methods.""",
     correctionMessage: r"""Try replacing this with a normal method.""");
 
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const Template<Message Function(String name)>
+    templateJsInteropStaticInteropTrustTypesUsageNotAllowed =
+    const Template<Message Function(String name)>(
+        problemMessageTemplate:
+            r"""JS interop class '#name' has an `@trustTypes` annotation, but `@trustTypes` is only supported within the sdk.""",
+        correctionMessageTemplate:
+            r"""Try removing the `@trustTypes` annotation.""",
+        withArguments:
+            _withArgumentsJsInteropStaticInteropTrustTypesUsageNotAllowed);
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const Code<Message Function(String name)>
+    codeJsInteropStaticInteropTrustTypesUsageNotAllowed =
+    const Code<Message Function(String name)>(
+  "JsInteropStaticInteropTrustTypesUsageNotAllowed",
+);
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+Message _withArgumentsJsInteropStaticInteropTrustTypesUsageNotAllowed(
+    String name) {
+  if (name.isEmpty) throw 'No name provided';
+  name = demangleMixinApplicationName(name);
+  return new Message(codeJsInteropStaticInteropTrustTypesUsageNotAllowed,
+      problemMessage:
+          """JS interop class '${name}' has an `@trustTypes` annotation, but `@trustTypes` is only supported within the sdk.""",
+      correctionMessage: """Try removing the `@trustTypes` annotation.""",
+      arguments: {'name': name});
+}
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const Template<Message Function(String name)>
+    templateJsInteropStaticInteropTrustTypesUsedWithoutStaticInterop =
+    const Template<Message Function(String name)>(
+        problemMessageTemplate:
+            r"""JS interop class '#name' has an `@trustTypes` annotation, but no `@staticInterop` annotation.""",
+        correctionMessageTemplate:
+            r"""Try marking the class using `@staticInterop`.""",
+        withArguments:
+            _withArgumentsJsInteropStaticInteropTrustTypesUsedWithoutStaticInterop);
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const Code<Message Function(String name)>
+    codeJsInteropStaticInteropTrustTypesUsedWithoutStaticInterop =
+    const Code<Message Function(String name)>(
+  "JsInteropStaticInteropTrustTypesUsedWithoutStaticInterop",
+);
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+Message _withArgumentsJsInteropStaticInteropTrustTypesUsedWithoutStaticInterop(
+    String name) {
+  if (name.isEmpty) throw 'No name provided';
+  name = demangleMixinApplicationName(name);
+  return new Message(
+      codeJsInteropStaticInteropTrustTypesUsedWithoutStaticInterop,
+      problemMessage:
+          """JS interop class '${name}' has an `@trustTypes` annotation, but no `@staticInterop` annotation.""",
+      correctionMessage: """Try marking the class using `@staticInterop`.""",
+      arguments: {'name': name});
+}
+
 // DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
 const Template<Message Function(String name)>
     templateJsInteropStaticInteropWithInstanceMembers =

pkg/_js_interop_checks/lib/js_interop_checks.dart

@@ -22,7 +22,9 @@ import 'package:_fe_analyzer_shared/src/messages/codes.dart'
         templateJsInteropStaticInteropWithInstanceMembers,
         templateJsInteropStaticInteropWithNonStaticSupertype,
         templateJsInteropJSClassExtendsDartClass,
-        templateJsInteropNativeClassInAnnotation;
+        templateJsInteropNativeClassInAnnotation,
+        templateJsInteropStaticInteropTrustTypesUsageNotAllowed,
+        templateJsInteropStaticInteropTrustTypesUsedWithoutStaticInterop;
 
 import 'src/js_interop.dart';
 
@@ -67,6 +69,11 @@ class JsInteropChecks extends RecursiveVisitor {
     'generated_tests/web_2/native/native_test',
   ];
 
+  List<Pattern> _allowedTrustTypesTestPatterns = [
+    RegExp(r'(?<!generated_)tests/lib/js'),
+    RegExp(r'(?<!generated_)tests/lib_2/js'),
+  ];
+
   bool _libraryIsGlobalNamespace = false;
 
   JsInteropChecks(
@@ -104,6 +111,25 @@ class JsInteropChecks extends RecursiveVisitor {
     _classHasJSAnnotation = hasJSInteropAnnotation(cls);
     _classHasAnonymousAnnotation = hasAnonymousAnnotation(cls);
     _classHasStaticInteropAnnotation = hasStaticInteropAnnotation(cls);
+    bool classHasTrustTypesAnnotation = hasTrustTypesAnnotation(cls);
+    if (classHasTrustTypesAnnotation) {
+      if (!_isAllowedTrustTypesUsage(cls)) {
+        _diagnosticsReporter.report(
+            templateJsInteropStaticInteropTrustTypesUsageNotAllowed
+                .withArguments(cls.name),
+            cls.fileOffset,
+            cls.name.length,
+            cls.fileUri);
+      }
+      if (!_classHasStaticInteropAnnotation) {
+        _diagnosticsReporter.report(
+            templateJsInteropStaticInteropTrustTypesUsedWithoutStaticInterop
+                .withArguments(cls.name),
+            cls.fileOffset,
+            cls.name.length,
+            cls.fileUri);
+      }
+    }
     var superclass = cls.superclass;
     if (superclass != null && superclass != _coreTypes.objectClass) {
       var superHasJSAnnotation = hasJSInteropAnnotation(superclass);
@@ -357,6 +383,14 @@ class JsInteropChecks extends RecursiveVisitor {
     }
   }
 
+  /// Verifies that use of `@trustTypes` is allowed.
+  bool _isAllowedTrustTypesUsage(Class cls) {
+    Uri uri = cls.enclosingLibrary.importUri;
+    return uri.isScheme('dart') && uri.path == 'ui' ||
+        _allowedTrustTypesTestPatterns
+            .any((pattern) => uri.path.contains(pattern));
+  }
+
   /// Verifies given member is one of the allowed usages of external:
   /// a dart low level library, a foreign helper, a native test,
   /// or a from environment constructor.

pkg/_js_interop_checks/lib/src/js_interop.dart

@@ -20,6 +20,11 @@ bool hasAnonymousAnnotation(Annotatable a) =>
 bool hasStaticInteropAnnotation(Annotatable a) =>
     a.annotations.any(_isStaticInteropAnnotation);
 
+/// Returns true iff the node has an `@trustTypes` annotation from
+/// `package:js` or from the internal `dart:_js_annotations`.
+bool hasTrustTypesAnnotation(Annotatable a) =>
+    a.annotations.any(_isTrustTypesAnnotation);
+
 /// If [a] has a `@JS('...')` annotation, returns the value inside the
 /// parentheses.
 ///
@@ -80,6 +85,9 @@ bool _isAnonymousAnnotation(Expression value) =>
 bool _isStaticInteropAnnotation(Expression value) =>
     _isInteropAnnotation(value, '_StaticInterop');
 
+bool _isTrustTypesAnnotation(Expression value) =>
+    _isInteropAnnotation(value, '_TrustTypes');
+
 /// Returns true if [value] is the `Native` annotation from `dart:_js_helper`.
 bool _isNativeAnnotation(Expression value) {
   var c = _annotationClass(value);

pkg/_js_interop_checks/lib/src/transformations/js_util_optimizer.dart

@@ -7,16 +7,19 @@ import 'package:kernel/class_hierarchy.dart';
 import 'package:kernel/core_types.dart';
 import 'package:kernel/type_environment.dart';
 
-import '../js_interop.dart' show getJSName;
+import '../js_interop.dart' show getJSName, hasTrustTypesAnnotation;
 
 /// Replaces js_util methods with inline calls to foreign_helper JS which
 /// emits the code as a JavaScript code fragment.
 class JsUtilOptimizer extends Transformer {
   final Procedure _callMethodTarget;
+  final Procedure _callMethodTrustTypeTarget;
   final List<Procedure> _callMethodUncheckedTargets;
+  final List<Procedure> _callMethodUncheckedTrustTypeTargets;
   final Procedure _callConstructorTarget;
   final List<Procedure> _callConstructorUncheckedTargets;
   final Procedure _getPropertyTarget;
+  final Procedure _getPropertyTrustTypeTarget;
   final Procedure _setPropertyTarget;
   final Procedure _setPropertyUncheckedTarget;
 
@@ -37,14 +40,21 @@ class JsUtilOptimizer extends Transformer {
   final CoreTypes _coreTypes;
   final StatefulStaticTypeContext _staticTypeContext;
   Map<Reference, ExtensionMemberDescriptor>? _extensionMemberIndex;
+  late Set<Reference> _shouldTrustType;
 
   JsUtilOptimizer(this._coreTypes, ClassHierarchy hierarchy)
       : _callMethodTarget =
             _coreTypes.index.getTopLevelProcedure('dart:js_util', 'callMethod'),
+        _callMethodTrustTypeTarget = _coreTypes.index
+            .getTopLevelProcedure('dart:js_util', '_callMethodTrustType'),
         _callMethodUncheckedTargets = List<Procedure>.generate(
             5,
             (i) => _coreTypes.index.getTopLevelProcedure(
                 'dart:js_util', '_callMethodUnchecked$i')),
+        _callMethodUncheckedTrustTypeTargets = List<Procedure>.generate(
+            5,
+            (i) => _coreTypes.index.getTopLevelProcedure(
+                'dart:js_util', '_callMethodUncheckedTrustType$i')),
         _callConstructorTarget = _coreTypes.index
             .getTopLevelProcedure('dart:js_util', 'callConstructor'),
         _callConstructorUncheckedTargets = List<Procedure>.generate(
@@ -53,6 +63,8 @@ class JsUtilOptimizer extends Transformer {
                 'dart:js_util', '_callConstructorUnchecked$i')),
         _getPropertyTarget = _coreTypes.index
             .getTopLevelProcedure('dart:js_util', 'getProperty'),
+        _getPropertyTrustTypeTarget = _coreTypes.index
+            .getTopLevelProcedure('dart:js_util', '_getPropertyTrustType'),
         _setPropertyTarget = _coreTypes.index
             .getTopLevelProcedure('dart:js_util', 'setProperty'),
         _setPropertyUncheckedTarget = _coreTypes.index
@@ -93,14 +105,16 @@ class JsUtilOptimizer extends Transformer {
     if (node.isExternal && node.isExtensionMember) {
       var index = _extensionMemberIndex ??=
           _createExtensionMembersIndex(node.enclosingLibrary);
-      var nodeDescriptor = index[node.reference]!;
+      Reference reference = node.reference;
+      var nodeDescriptor = index[reference]!;
+      bool shouldTrustType = _shouldTrustType.contains(reference);
       if (!nodeDescriptor.isStatic) {
         if (nodeDescriptor.kind == ExtensionMemberKind.Getter) {
-          transformedBody = _getExternalGetterBody(node);
+          transformedBody = _getExternalGetterBody(node, shouldTrustType);
         } else if (nodeDescriptor.kind == ExtensionMemberKind.Setter) {
           transformedBody = _getExternalSetterBody(node);
         } else if (nodeDescriptor.kind == ExtensionMemberKind.Method) {
-          transformedBody = _getExternalMethodBody(node);
+          transformedBody = _getExternalMethodBody(node, shouldTrustType);
         }
       }
     }
@@ -120,9 +134,17 @@ class JsUtilOptimizer extends Transformer {
   Map<Reference, ExtensionMemberDescriptor> _createExtensionMembersIndex(
       Library library) {
     _extensionMemberIndex = {};
-    library.extensions.forEach((extension) => extension.members.forEach(
-        (descriptor) =>
-            _extensionMemberIndex![descriptor.member] = descriptor));
+    _shouldTrustType = {};
+    library.extensions
+        .forEach((extension) => extension.members.forEach((descriptor) {
+              Reference reference = descriptor.member;
+              _extensionMemberIndex![reference] = descriptor;
+              DartType onType = extension.onType;
+              if (onType is InterfaceType &&
+                  hasTrustTypesAnnotation(onType.className.asClass)) {
+                _shouldTrustType.add(reference);
+              }
+            }));
     return _extensionMemberIndex!;
   }
 
@@ -130,11 +152,13 @@ class JsUtilOptimizer extends Transformer {
   ///
   /// The new function body will call the optimized version of
   /// `js_util.getProperty` for the given external getter.
-  ReturnStatement _getExternalGetterBody(Procedure node) {
+  ReturnStatement _getExternalGetterBody(Procedure node, bool shouldTrustType) {
     var function = node.function;
     assert(function.positionalParameters.length == 1);
+    Procedure target =
+        shouldTrustType ? _getPropertyTrustTypeTarget : _getPropertyTarget;
     var getPropertyInvocation = StaticInvocation(
-        _getPropertyTarget,
+        target,
         Arguments([
           VariableGet(function.positionalParameters.first),
           StringLiteral(_getExtensionMemberName(node))
@@ -170,10 +194,12 @@ class JsUtilOptimizer extends Transformer {
   ///
   /// The new function body will call the optimized version of
   /// `js_util.callMethod` for the given external method.
-  ReturnStatement _getExternalMethodBody(Procedure node) {
+  ReturnStatement _getExternalMethodBody(Procedure node, bool shouldTrustType) {
     var function = node.function;
+    Procedure target =
+        shouldTrustType ? _callMethodTrustTypeTarget : _callMethodTarget;
     var callMethodInvocation = StaticInvocation(
-        _callMethodTarget,
+        target,
         Arguments([
           VariableGet(function.positionalParameters.first),
           StringLiteral(_getExtensionMemberName(node)),
@@ -185,7 +211,8 @@ class JsUtilOptimizer extends Transformer {
           function.returnType
         ]))
       ..fileOffset = node.fileOffset;
-    return ReturnStatement(_lowerCallMethod(callMethodInvocation));
+    return ReturnStatement(_lowerCallMethod(callMethodInvocation,
+        shouldTrustType: shouldTrustType));
   }
 
   /// Returns the extension member name.
@@ -214,7 +241,8 @@ class JsUtilOptimizer extends Transformer {
     if (node.target == _setPropertyTarget) {
       node = _lowerSetProperty(node);
     } else if (node.target == _callMethodTarget) {
-      node = _lowerCallMethod(node);
+      // Never trust types on explicit `js_util` calls.
+      node = _lowerCallMethod(node, shouldTrustType: false);
     } else if (node.target == _callConstructorTarget) {
       node = _lowerCallConstructor(node);
     }
@@ -245,13 +273,17 @@ class JsUtilOptimizer extends Transformer {
   /// Calls will be lowered when using a List literal or constant list with 0-4
   /// elements for the `callMethod` arguments, or the `List.empty()` factory.
   /// Removing the checks allows further inlining by the compilers.
-  StaticInvocation _lowerCallMethod(StaticInvocation node) {
+  StaticInvocation _lowerCallMethod(StaticInvocation node,
+      {required bool shouldTrustType}) {
     Arguments arguments = node.arguments;
     assert(arguments.positional.length == 3);
     assert(arguments.named.isEmpty);
+    List<Procedure> targets = shouldTrustType
+        ? _callMethodUncheckedTrustTypeTargets
+        : _callMethodUncheckedTargets;
 
     return _lowerToCallUnchecked(
-        node, _callMethodUncheckedTargets, arguments.positional.sublist(0, 2));
+        node, targets, arguments.positional.sublist(0, 2));
   }
 
   /// Lowers the given js_util `callConstructor` call to `_callConstructorUncheckedN`

pkg/front_end/messages.status

@@ -577,6 +577,10 @@ JsInteropStaticInteropWithInstanceMembers/analyzerCode: Fail # Web compiler spec
 JsInteropStaticInteropWithInstanceMembers/example: Fail # Web compiler specific
 JsInteropStaticInteropWithNonStaticSupertype/analyzerCode: Fail # Web compiler specific
 JsInteropStaticInteropWithNonStaticSupertype/example: Fail # Web compiler specific
+JsInteropStaticInteropTrustTypesUsageNotAllowed/analyzerCode: Fail # Web compiler specific
+JsInteropStaticInteropTrustTypesUsageNotAllowed/example: Fail # Web compiler specific
+JsInteropStaticInteropTrustTypesUsedWithoutStaticInterop/analyzerCode: Fail # Web compiler specific
+JsInteropStaticInteropTrustTypesUsedWithoutStaticInterop/example: Fail # Web compiler specific
 LanguageVersionInvalidInDotPackages/analyzerCode: Fail
 LanguageVersionMismatchInPart/analyzerCode: Fail
 LanguageVersionMismatchInPart/part_wrapped_script: Fail # Part in (now) part.

pkg/front_end/messages.yaml

@@ -5197,6 +5197,14 @@ JsInteropStaticInteropWithNonStaticSupertype:
   problemMessage: "JS interop class '#name' has an `@staticInterop` annotation, but has supertype '#name2', which is non-static."
   correctionMessage: "Try marking the supertype as a static interop class using `@staticInterop`."
 
+JsInteropStaticInteropTrustTypesUsedWithoutStaticInterop:
+  problemMessage: "JS interop class '#name' has an `@trustTypes` annotation, but no `@staticInterop` annotation."
+  correctionMessage: "Try marking the class using `@staticInterop`."
+
+JsInteropStaticInteropTrustTypesUsageNotAllowed:
+  problemMessage: "JS interop class '#name' has an `@trustTypes` annotation, but `@trustTypes` is only supported within the sdk."
+  correctionMessage: "Try removing the `@trustTypes` annotation."
+
 DefaultListConstructorError:
   problemMessage: "Can't use the default List constructor."
   correctionMessage: "Try using List.filled instead."

pkg/front_end/test/spell_checking_list_messages.txt

@@ -87,6 +87,7 @@ t
 team
 this.namedconstructor
 this.x
+trusttypes
 type3.#name
 u
 unsound

pkg/front_end/testcases/general/constants/js_semantics/issue46123.dart.weak.expect

@@ -35,5 +35,5 @@ constants  {
 
 Constructor coverage from constants:
 org-dartlang-testcase:///issue46123.dart:
-- JS. (from org-dartlang-testcase-sdk:///pkg/js/lib/js.dart:21:9)
+- JS. (from org-dartlang-testcase-sdk:///pkg/js/lib/js.dart:23:9)
 - Object. (from org-dartlang-sdk:///lib/core/object.dart:25:9)

pkg/front_end/testcases/general/constants/js_semantics/issue46123.dart.weak.modular.expect

@@ -35,5 +35,5 @@ constants  {
 
 Constructor coverage from constants:
 org-dartlang-testcase:///issue46123.dart:
-- JS. (from org-dartlang-testcase-sdk:///pkg/js/lib/js.dart:21:9)
+- JS. (from org-dartlang-testcase-sdk:///pkg/js/lib/js.dart:23:9)
 - Object. (from org-dartlang-sdk:///lib/core/object.dart:25:9)

pkg/front_end/testcases/general/constants/js_semantics/issue46123.dart.weak.transformed.expect

@@ -35,5 +35,5 @@ constants  {
 
 Constructor coverage from constants:
 org-dartlang-testcase:///issue46123.dart:
-- JS. (from org-dartlang-testcase-sdk:///pkg/js/lib/js.dart:21:9)
+- JS. (from org-dartlang-testcase-sdk:///pkg/js/lib/js.dart:23:9)
 - Object. (from org-dartlang-sdk:///lib/core/object.dart:25:9)

pkg/front_end/testcases/general/constants/js_semantics/issue46123b.dart.weak.expect

@@ -37,5 +37,5 @@ constants  {
 
 Constructor coverage from constants:
 org-dartlang-testcase:///issue46123b.dart:
-- JS. (from org-dartlang-testcase-sdk:///pkg/js/lib/js.dart:21:9)
+- JS. (from org-dartlang-testcase-sdk:///pkg/js/lib/js.dart:23:9)
 - Object. (from org-dartlang-sdk:///lib/core/object.dart:25:9)

pkg/front_end/testcases/general/constants/js_semantics/issue46123b.dart.weak.modular.expect

@@ -37,5 +37,5 @@ constants  {
 
 Constructor coverage from constants:
 org-dartlang-testcase:///issue46123b.dart:
-- JS. (from org-dartlang-testcase-sdk:///pkg/js/lib/js.dart:21:9)
+- JS. (from org-dartlang-testcase-sdk:///pkg/js/lib/js.dart:23:9)
 - Object. (from org-dartlang-sdk:///lib/core/object.dart:25:9)

pkg/front_end/testcases/general/constants/js_semantics/issue46123b.dart.weak.transformed.expect

@@ -37,5 +37,5 @@ constants  {
 
 Constructor coverage from constants:
 org-dartlang-testcase:///issue46123b.dart:
-- JS. (from org-dartlang-testcase-sdk:///pkg/js/lib/js.dart:21:9)
+- JS. (from org-dartlang-testcase-sdk:///pkg/js/lib/js.dart:23:9)
 - Object. (from org-dartlang-sdk:///lib/core/object.dart:25:9)

pkg/js/lib/js.dart

@@ -5,6 +5,8 @@
 /// Annotations to mark interfaces to JavaScript.
 library js;
 
+import 'package:meta/meta.dart';
+
 export 'dart:js' show allowInterop, allowInteropCaptureThis;
 
 /// An annotation that indicates a library, class, or member is implemented
@@ -45,3 +47,16 @@ const _Anonymous anonymous = _Anonymous();
 /// These classes should not contain any instance members, inherited or
 /// otherwise, and should instead use static extension members.
 const _StaticInterop staticInterop = _StaticInterop();
+
+/// NOTE: [trustTypes] is an experimental annotation that may disappear at any
+/// point in time. It exists solely to help users who wish to migrate classes
+/// from the older style of JS interop to the new static interop model but wish
+/// to preserve the older semantics for type checks. This annotation must be
+/// used alongside [staticInterop] and it affects any external methods in any
+/// extension to the static interop class.
+@experimental
+class _TrustTypes {
+  const _TrustTypes();
+}
+
+const _TrustTypes trustTypes = _TrustTypes();

pkg/js/pubspec.yaml

@@ -6,5 +6,8 @@ repository: https://github.com/dart-lang/sdk/tree/main/pkg/js
 environment:
   sdk: ">=2.16.0-100.0.dev <3.0.0"
 
+dependencies:
+  meta: ^1.7.0
+
 dev_dependencies:
   lints: any

sdk/lib/js_util/js_util.dart

@@ -74,6 +74,10 @@ bool hasProperty(Object o, Object name) => JS('bool', '# in #', name, o);
 T getProperty<T>(Object o, Object name) =>
     JS<dynamic>('Object|Null', '#[#]', o, name);
 
+/// Similar to [getProperty] but introduces an unsound implicit cast to `T`.
+T _getPropertyTrustType<T>(Object o, Object name) =>
+    JS<T>('Object|Null', '#[#]', o, name);
+
 // A CFE transformation may optimize calls to `setProperty`, when [value] is
 // statically known to be a non-function.
 T setProperty<T>(Object o, Object name, T? value) {
@@ -95,18 +99,38 @@ T callMethod<T>(Object o, String method, List<Object?> args) {
   return JS<dynamic>('Object|Null', '#[#].apply(#, #)', o, method, o, args);
 }
 
+/// Similar to [callMethod] but introduces an unsound implicit cast to `T`.
+T _callMethodTrustType<T>(Object o, String method, List<Object?> args) {
+  assertInteropArgs(args);
+  return JS<T>('Object|Null', '#[#].apply(#, #)', o, method, o, args);
+}
+
 /// Unchecked version for 0 arguments, only used in a CFE transformation.
 @pragma('dart2js:tryInline')
 T _callMethodUnchecked0<T>(Object o, String method) {
   return JS<dynamic>('Object|Null', '#[#]()', o, method);
 }
 
+/// Similar to [_callMethodUnchecked] but introduces an unsound implicit cast
+/// to `T`.
+@pragma('dart2js:tryInline')
+T _callMethodUncheckedTrustType0<T>(Object o, String method) {
+  return JS<T>('Object|Null', '#[#]()', o, method);
+}
+
 /// Unchecked version for 1 argument, only used in a CFE transformation.
 @pragma('dart2js:tryInline')
 T _callMethodUnchecked1<T>(Object o, String method, Object? arg1) {
   return JS<dynamic>('Object|Null', '#[#](#)', o, method, arg1);
 }
 
+/// Similar to [_callMethodUnchecked1] but introduces an unsound implicit cast
+/// to `T`.
+@pragma('dart2js:tryInline')
+T _callMethodUncheckedTrustType1<T>(Object o, String method, Object? arg1) {
+  return JS<T>('Object|Null', '#[#](#)', o, method, arg1);
+}
+
 /// Unchecked version for 2 arguments, only used in a CFE transformation.
 @pragma('dart2js:tryInline')
 T _callMethodUnchecked2<T>(
@@ -114,6 +138,14 @@ T _callMethodUnchecked2<T>(
   return JS<dynamic>('Object|Null', '#[#](#, #)', o, method, arg1, arg2);
 }
 
+/// Similar to [_callMethodUnchecked2] but introduces an unsound implicit cast
+/// to `T`.
+@pragma('dart2js:tryInline')
+T _callMethodUncheckedTrustType2<T>(
+    Object o, String method, Object? arg1, Object? arg2) {
+  return JS<T>('Object|Null', '#[#](#, #)', o, method, arg1, arg2);
+}
+
 /// Unchecked version for 3 arguments, only used in a CFE transformation.
 @pragma('dart2js:tryInline')
 T _callMethodUnchecked3<T>(
@@ -122,6 +154,14 @@ T _callMethodUnchecked3<T>(
       'Object|Null', '#[#](#, #, #)', o, method, arg1, arg2, arg3);
 }
 
+/// Similar to [_callMethodUnchecked3] but introduces an unsound implicit cast
+/// to `T`.
+@pragma('dart2js:tryInline')
+T _callMethodUncheckedTrustType3<T>(
+    Object o, String method, Object? arg1, Object? arg2, Object? arg3) {
+  return JS<T>('Object|Null', '#[#](#, #, #)', o, method, arg1, arg2, arg3);
+}
+
 /// Unchecked version for 4 arguments, only used in a CFE transformation.
 @pragma('dart2js:tryInline')
 T _callMethodUnchecked4<T>(Object o, String method, Object? arg1, Object? arg2,
@@ -130,6 +170,15 @@ T _callMethodUnchecked4<T>(Object o, String method, Object? arg1, Object? arg2,
       'Object|Null', '#[#](#, #, #, #)', o, method, arg1, arg2, arg3, arg4);
 }
 
+/// Similar to [_callMethodUnchecked4] but introduces an unsound implicit cast
+/// to `T`.
+@pragma('dart2js:tryInline')
+T _callMethodUncheckedTrustType4<T>(Object o, String method, Object? arg1,
+    Object? arg2, Object? arg3, Object? arg4) {
+  return JS<T>(
+      'Object|Null', '#[#](#, #, #, #)', o, method, arg1, arg2, arg3, arg4);
+}
+
 /// Check whether [o] is an instance of [type].
 ///
 /// The value in [type] is expected to be a JS-interop object that

tests/lib/js/trust_types_annotation_test.dart

@@ -0,0 +1,11 @@
+// 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:js/js.dart';
+
+@JS()
+@trustTypes
+class Incorrect {}
+//    ^
+// [web] JS interop class 'Incorrect' has an `@trustTypes` annotation, but no `@staticInterop` annotation.

tests/lib/js/trust_types_test.dart

@@ -0,0 +1,77 @@
+// 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.
+
+// Test that the [trustTypes] annotation has the same semantics as the older
+// style of js interop.
+
+import 'package:js/js.dart';
+import 'package:expect/expect.dart';
+
+class NonExistent {}
+
+@JS()
+@staticInterop
+@trustTypes
+class TrustMe {
+  external factory TrustMe();
+}
+
+extension TrustMeExtension on TrustMe {
+  external List<NonExistent> get foos;
+  external List<NonExistent> callFoos();
+  external List<NonExistent> callFoos1(int ignored);
+  external List<NonExistent> callFoos2(int ignored1, int ignored2);
+  external List<NonExistent> callFoos3(
+      int ignored1, int ignored2, int ignored3);
+  external List<NonExistent> callFoos4(
+      int ignored1, int ignored2, int ignored3, int ignored4);
+  external List<NonExistent> callFoos5(
+      int ignored1, int ignored2, int ignored3, int ignored4, int ignored5);
+  external String get fooPrimitive;
+}
+
+@JS()
+external void eval(String code);
+
+void main() {
+  eval(r'''
+      TrustMe = function TrustMe() {
+        this.foos = 'not a list 1';
+        this.fooPrimitive = 5;
+        this.callFoos = function() {
+          return 'not a list 2';
+        }
+        this.callFoos1 = function(a) {
+          return 'not a list 3';
+        }
+        this.callFoos2 = function(a, b) {
+          return 'not a list 4';
+        }
+        this.callFoos3 = function(a, b, c) {
+          return 'not a list 5';
+        }
+        this.callFoos4 = function(a, b, c, d) {
+          return 'not a list 6';
+        }
+        this.callFoos5 = function(a, b, c, d, e) {
+          return 'not a list 7';
+        }
+      }
+      ''');
+  final trusted = TrustMe();
+  Expect.equals('not a list 1', trusted.foos.toString());
+  Expect.equals('not a list 2', trusted.callFoos().toString());
+  Expect.equals('not a list 3', trusted.callFoos1(1).toString());
+  Expect.equals('not a list 4', trusted.callFoos2(1, 1).toString());
+  Expect.equals('not a list 5', trusted.callFoos3(1, 1, 1).toString());
+  Expect.equals('not a list 6', trusted.callFoos4(1, 1, 1, 1).toString());
+
+  final falseList = trusted.callFoos5(1, 1, 1, 1, 1);
+  Expect.equals('not a list 7', falseList.toString());
+  Expect.throws(() => falseList.removeAt(0));
+
+  final falseString = trusted.fooPrimitive;
+  Expect.equals(5, falseString);
+  Expect.throws(() => falseString.codeUnitAt(0));
+}

tests/lib_2/js/trust_types_annotation_test.dart

@@ -0,0 +1,11 @@
+// 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:js/js.dart';
+
+@JS()
+@trustTypes
+class Incorrect {}
+//    ^
+// [web] JS interop class 'Incorrect' has an `@trustTypes` annotation, but no `@staticInterop` annotation.

tests/lib_2/js/trust_types_test.dart

@@ -0,0 +1,77 @@
+// 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.
+
+// Test that the [trustTypes] annotation has the same semantics as the older
+// style of js interop.
+
+import 'package:js/js.dart';
+import 'package:expect/expect.dart';
+
+class NonExistent {}
+
+@JS()
+@staticInterop
+@trustTypes
+class TrustMe {
+  external factory TrustMe();
+}
+
+extension TrustMeExtension on TrustMe {
+  external List<NonExistent> get foos;
+  external List<NonExistent> callFoos();
+  external List<NonExistent> callFoos1(int ignored);
+  external List<NonExistent> callFoos2(int ignored1, int ignored2);
+  external List<NonExistent> callFoos3(
+      int ignored1, int ignored2, int ignored3);
+  external List<NonExistent> callFoos4(
+      int ignored1, int ignored2, int ignored3, int ignored4);
+  external List<NonExistent> callFoos5(
+      int ignored1, int ignored2, int ignored3, int ignored4, int ignored5);
+  external String get fooPrimitive;
+}
+
+@JS()
+external void eval(String code);
+
+void main() {
+  eval(r'''
+      TrustMe = function TrustMe() {
+        this.foos = 'not a list 1';
+        this.fooPrimitive = 5;
+        this.callFoos = function() {
+          return 'not a list 2';
+        }
+        this.callFoos1 = function(a) {
+          return 'not a list 3';
+        }
+        this.callFoos2 = function(a, b) {
+          return 'not a list 4';
+        }
+        this.callFoos3 = function(a, b, c) {
+          return 'not a list 5';
+        }
+        this.callFoos4 = function(a, b, c, d) {
+          return 'not a list 6';
+        }
+        this.callFoos5 = function(a, b, c, d, e) {
+          return 'not a list 7';
+        }
+      }
+      ''');
+  final trusted = TrustMe();
+  Expect.equals('not a list 1', trusted.foos.toString());
+  Expect.equals('not a list 2', trusted.callFoos().toString());
+  Expect.equals('not a list 3', trusted.callFoos1(1).toString());
+  Expect.equals('not a list 4', trusted.callFoos2(1, 1).toString());
+  Expect.equals('not a list 5', trusted.callFoos3(1, 1, 1).toString());
+  Expect.equals('not a list 6', trusted.callFoos4(1, 1, 1, 1).toString());
+
+  final falseList = trusted.callFoos5(1, 1, 1, 1, 1);
+  Expect.equals('not a list 7', falseList.toString());
+  Expect.throws(() => falseList.removeAt(0));
+
+  final falseString = trusted.fooPrimitive;
+  Expect.equals(5, falseString);
+  Expect.throws(() => falseString.codeUnitAt(0));
+}

tests/modular/js_interop/modules.yaml

@@ -6,5 +6,6 @@
 dependencies:
   main: log
   log: js
+  js: meta
 packages:
   js: ../../../pkg/js/lib

tests/modular/static_interop_erasure/modules.yaml

@@ -7,5 +7,6 @@
 dependencies:
   main: static_interop
   static_interop: js
+  js: meta
 packages:
   js: ../../../pkg/js/lib

tests/web/js_trust_types_disallowed_test.dart

@@ -0,0 +1,12 @@
+// 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:js/js.dart';
+
+@JS()
+@staticInterop
+@trustTypes
+class Incorrect {}
+//    ^
+// [web] JS interop class 'Incorrect' has an `@trustTypes` annotation, but `@trustTypes` is only supported within the sdk.

tests/web_2/js_trust_types_disallowed_test.dart

@@ -0,0 +1,12 @@
+// 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:js/js.dart';
+
+@JS()
+@staticInterop
+@trustTypes
+class Incorrect {}
+//    ^
+// [web] JS interop class 'Incorrect' has an `@trustTypes` annotation, but `@trustTypes` is only supported within the sdk.