Implementation of async-await transformation on js ast.

pkg/compiler/lib/src/js/builder.dart

 // Copyright (c) 2013, 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.
 
 // Utilities for building JS ASTs at runtime.  Contains a builder class
 // and a parser that parses part of the language.
 
 part of js;
 
 
@@ skipping 698 matching lines @@
     String last = lastToken;
     if (acceptCategory(ALPHA)) {
       if (last == "true") {
         return new LiteralBool(true);
       } else if (last == "false") {
         return new LiteralBool(false);
       } else if (last == "null") {
         return new LiteralNull();
       } else if (last == "function") {
         return parseFunctionExpression();
+      } else if (last == "this") {
+        return new This();
       } else {
         return new VariableUse(last);
       }
     } else if (acceptCategory(LPAREN)) {
       Expression expression = parseExpression();
       expectCategory(RPAREN);
       return expression;
     } else if (acceptCategory(STRING)) {
       return new LiteralString(last);
     } else if (acceptCategory(NUMERIC)) {
@@ skipping 380 matching lines @@
       if (acceptString('while')) return parseWhile();
 
       if (acceptString('do')) return parseDo();
 
       if (acceptString('switch')) return parseSwitch();
 
       if (lastToken == 'case') error("Case outside switch.");
 
       if (lastToken == 'default') error("Default outside switch.");
 
+      if (lastToken == 'yield') return parseYield();
+
       if (lastToken == 'with') {
         error('Not implemented in mini parser');
       }
+
     }
 
     bool checkForInterpolatedStatement = lastCategory == HASH;
 
     Expression expression = parseExpression();
 
     if (expression is VariableUse && acceptCategory(COLON)) {
       return new LabeledStatement(expression.name, parseStatement());
     }
 
@@ skipping 14 matching lines @@
     return new ExpressionStatement(expression);
   }
 
   Statement parseReturn() {
     if (acceptSemicolon()) return new Return();
     Expression expression = parseExpression();
     expectSemicolon();
     return new Return(expression);
   }
 
+  Statement parseYield() {
+    bool hasStar = acceptString('*');
+    Expression expression = parseExpression();
+    expectSemicolon();
+    return new DartYield(expression, hasStar);
+  }
+
   Statement parseThrow() {
     if (skippedNewline) error('throw expression must be on same line');
     Expression expression = parseExpression();
     expectSemicolon();
     return new Throw(expression);
   }
 
   Statement parseBreakOrContinue(constructor) {
     var identifier = lastToken;
     if (!skippedNewline && acceptCategory(ALPHA)) {
@@ skipping 149 matching lines @@
   Catch parseCatch() {
     expectCategory(LPAREN);
     String identifier = lastToken;
     expectCategory(ALPHA);
     expectCategory(RPAREN);
     expectCategory(LBRACE);
     Block body = parseBlock();
     return new Catch(new VariableDeclaration(identifier), body);
   }
 }