[dart2wasm] Report warning on sync*

Change-Id: If5b0492438830b8813d86a031193fa8d64ed1b1c
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/279017
Commit-Queue: Aske Simon Christensen <askesc@google.com>
Reviewed-by: Johnni Winther <johnniwinther@google.com>

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

@@ -12365,6 +12365,14 @@ const MessageCode messageVoidWithTypeArguments = const MessageCode(
     problemMessage: r"""Type 'void' can't have type arguments.""",
     correctionMessage: r"""Try removing the type arguments.""");
 
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const Code<Null> codeWasmSyncStar = messageWasmSyncStar;
+
+// DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
+const MessageCode messageWasmSyncStar = const MessageCode("WasmSyncStar",
+    severity: Severity.warning,
+    problemMessage: r"""Compilation to Wasm does not support 'sync*'.""");
+
 // DO NOT EDIT. THIS FILE IS GENERATED. SEE TOP OF FILE.
 const Code<Null> codeWeakWithStrongDillLibrary =
     messageWeakWithStrongDillLibrary;

pkg/dart2wasm/lib/target.dart

@@ -174,7 +174,8 @@ class WasmTarget extends Target {
       logger?.call("Transformed ffi annotations");
     }
 
-    wasmTrans.transformLibraries(libraries, coreTypes, hierarchy);
+    wasmTrans.transformLibraries(
+        libraries, coreTypes, hierarchy, diagnosticReporter);
   }
 
   @override

pkg/dart2wasm/lib/transformers.dart

@@ -5,23 +5,28 @@
 import 'package:kernel/ast.dart';
 import 'package:kernel/class_hierarchy.dart';
 import 'package:kernel/core_types.dart';
+import 'package:kernel/target/targets.dart';
 import 'package:kernel/type_environment.dart';
 import 'package:kernel/type_algebra.dart';
+import 'package:_fe_analyzer_shared/src/messages/codes.dart'
+    show messageWasmSyncStar;
 
-void transformLibraries(
-    List<Library> libraries, CoreTypes coreTypes, ClassHierarchy hierarchy) {
-  final transformer = _WasmTransformer(coreTypes, hierarchy);
+void transformLibraries(List<Library> libraries, CoreTypes coreTypes,
+    ClassHierarchy hierarchy, DiagnosticReporter diagnosticReporter) {
+  final transformer =
+      _WasmTransformer(coreTypes, hierarchy, diagnosticReporter);
   libraries.forEach(transformer.visitLibrary);
 }
 
 void transformProcedure(
     Procedure procedure, CoreTypes coreTypes, ClassHierarchy hierarchy) {
-  final transformer = _WasmTransformer(coreTypes, hierarchy);
+  final transformer = _WasmTransformer(coreTypes, hierarchy, null);
   procedure.accept(transformer);
 }
 
 class _WasmTransformer extends Transformer {
   final TypeEnvironment env;
+  final DiagnosticReporter? diagnosticReporter;
 
   Member? _currentMember;
   StaticTypeContext? _cachedTypeContext;
@@ -43,7 +48,8 @@ class _WasmTransformer extends Transformer {
 
   CoreTypes get coreTypes => env.coreTypes;
 
-  _WasmTransformer(CoreTypes coreTypes, ClassHierarchy hierarchy)
+  _WasmTransformer(
+      CoreTypes coreTypes, ClassHierarchy hierarchy, this.diagnosticReporter)
       : env = TypeEnvironment(coreTypes, hierarchy),
         _nonNullableTypeType = coreTypes.index
             .getClass('dart:core', '_Type')
@@ -640,6 +646,10 @@ class _WasmTransformer extends Transformer {
       _enclosingIsAsyncStar = false;
       return super.visitFunctionNode(functionNode);
     } else {
+      if (functionNode.dartAsyncMarker == AsyncMarker.SyncStar) {
+        diagnosticReporter?.report(messageWasmSyncStar, functionNode.fileOffset,
+            1, functionNode.location?.file);
+      }
       bool previousEnclosing = _enclosingIsAsyncStar;
       TreeNode result = super.visitFunctionNode(functionNode);
       _enclosingIsAsyncStar = previousEnclosing;

pkg/front_end/messages.status

@@ -984,6 +984,8 @@ VariableCouldBeNullDueToWrite/example: Fail
 VariablePatternTypeMismatchInSwitchHeads/analyzerCode: Fail
 VariablePatternTypeMismatchInSwitchHeads/part_wrapped_script: Crash
 VariablePatternTypeMismatchInSwitchHeads/script: Crash
+WasmSyncStar/analyzerCode: Fail
+WasmSyncStar/example: Fail
 WeakWithStrongDillLibrary/analyzerCode: Fail
 WeakWithStrongDillLibrary/example: Fail
 WebLiteralCannotBeRepresentedExactly/analyzerCode: Fail

pkg/front_end/messages.yaml

@@ -1675,6 +1675,10 @@ YieldNotGenerator:
   problemMessage: "'yield' can only be used in 'sync*' or 'async*' methods."
   analyzerCode: YIELD_IN_NON_GENERATOR
 
+WasmSyncStar:
+  problemMessage: "Compilation to Wasm does not support 'sync*'."
+  severity: WARNING
+
 OnlyTry:
   index: 20
   problemMessage: "A try block must be followed by an 'on', 'catch', or 'finally' clause."

pkg/front_end/testcases/dart2wasm/yield.dart.strong.transformed.expect

@@ -1,3 +1,8 @@
+//
+// Problems outside component:
+//
+// pkg/front_end/testcases/dart2wasm/yield.dart: Warning: Compilation to Wasm does not support 'sync*'.
+//
 library /*isNonNullableByDefault*/;
 import self as self;
 import "dart:core" as core;