Allow AstBuilder to report parse errors.

pkg/front_end/lib/src/fasta/analyzer/ast_builder.dart

 // Copyright (c) 2016, 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.
 
 library fasta.analyzer.ast_builder;
 
 import 'package:analyzer/analyzer.dart';
 import 'package:analyzer/dart/ast/ast_factory.dart' show AstFactory;
 import 'package:analyzer/dart/ast/standard_ast_factory.dart' as standard;
 import 'package:analyzer/dart/ast/token.dart' as analyzer show Token;
 import 'package:analyzer/dart/element/element.dart' show Element;
 import '../parser/parser.dart' show FormalParameterType;
 import '../scanner/token.dart' show BeginGroupToken, Token;
 
 import '../errors.dart' show internalError;
 import '../kernel/kernel_builder.dart'
     show Builder, KernelLibraryBuilder, ProcedureBuilder;
 import '../parser/identifier_context.dart' show IdentifierContext;
 import '../quote.dart';
 import '../source/scope_listener.dart'
     show JumpTargetKind, NullValue, Scope, ScopeListener;
 import 'analyzer.dart' show toKernel;
 import 'element_store.dart'
     show
         AnalyzerLocalVariableElemment,
         AnalyzerParameterElement,
         ElementStore,
         KernelClassElement;
+import 'package:analyzer/src/dart/error/syntactic_errors.dart';
+import 'package:front_end/src/fasta/parser/error_kind.dart';
 import 'token_utils.dart' show toAnalyzerToken, toAnalyzerCommentToken;
 
 class AstBuilder extends ScopeListener {
   final AstFactory ast = standard.astFactory;
 
+  final ErrorReporter errorReporter;
   final KernelLibraryBuilder library;
-
   final Builder member;
-
   final ElementStore elementStore;
 
   @override
   final Uri uri;
 
   /// The name of the class currently being parsed, or `null` if no class is
   /// being parsed.
   String className;
 
-  AstBuilder(this.library, this.member, this.elementStore, Scope scope,
+  AstBuilder(this.errorReporter, this.library, this.member, this.elementStore,
+      Scope scope,
       [Uri uri])
       : uri = uri ?? library.fileUri,
         super(scope);
 
   createJumpTarget(JumpTargetKind kind, int charOffset) {
     // TODO(ahe): Implement jump targets.
     return null;
   }
 
   void beginLiteralString(Token token) {
@@ skipping 887 matching lines @@
       push(expression);
     } else {
       push(ast.indexExpressionForTarget(
           target,
           toAnalyzerToken(openCurlyBracket),
           index,
           toAnalyzerToken(closeCurlyBracket)));
     }
   }
 
+  @override
+  void handleInvalidExpression(Token token) {
+    debugEvent("InvalidExpression");
+  }
+
+  @override
+  Token handleUnrecoverableError(Token token, ErrorKind kind, Map arguments) {
+    if (kind == ErrorKind.ExpectedExpression) {
+      String lexeme = token.lexeme;
+      if (identical('async', lexeme) || identical('yield', lexeme)) {
+        errorReporter?.reportErrorForOffset(
+            ParserErrorCode.ASYNC_KEYWORD_USED_AS_IDENTIFIER,
+            token.charOffset,
+            token.charCount);
+        push(ast.simpleIdentifier(toAnalyzerToken(token)));
+        return token;
+      }
+    }
+    return super.handleUnrecoverableError(token, kind, arguments);
+  }
+
   void handleUnaryPrefixExpression(Token token) {
     debugEvent("UnaryPrefixExpression");
     push(ast.prefixExpression(toAnalyzerToken(token), pop()));
   }
 
   void handleUnaryPrefixAssignmentExpression(Token token) {
     debugEvent("UnaryPrefixAssignmentExpression");
     push(ast.prefixExpression(toAnalyzerToken(token), pop()));
   }
 
@@ skipping 803 matching lines @@
       } else if (identical('static', s)) {
         staticKeyword = token;
       } else if (identical('var', s)) {
         finalConstOrVarKeyword = token;
       } else {
         internalError('Unhandled modifier: $s');
       }
     }
   }
 }