VM: [Kernel] Fix checked mode issues with await/async transformer

pkg/kernel/lib/transformations/continuation.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 kernel.transformations.continuation;
 
 import 'dart:math' as math;
 
 import '../ast.dart';
+import '../core_types.dart';
 import '../visitor.dart';
 
 import 'async.dart';
 
 Program transformProgram(Program program) {
   var helper = new HelperNodes.fromProgram(program);
   var rewriter = new RecursiveContinuationRewriter(helper);
   return rewriter.rewriteProgram(program);
 }
 
@@ skipping 85 matching lines @@
             new VariableDeclaration(":stack_trace${depth}"),
           ]);
 
   List<VariableDeclaration> variableDeclarations() =>
       [asyncJumpVariable, asyncContextVariable]
         ..addAll(createCapturedTryVariables())
         ..addAll(createCapturedCatchVariables());
 }
 
 class SyncStarFunctionRewriter extends ContinuationRewriterBase {
-  final VariableDeclaration iteratorVariable =
-      new VariableDeclaration(":iterator");
+  final VariableDeclaration iteratorVariable;
 
   SyncStarFunctionRewriter(helper, enclosingFunction)
-      : super(helper, enclosingFunction);
+      : iteratorVariable = new VariableDeclaration(':iterator')
+            ..type = helper.iteratorClass.rawType,
+        super(helper, enclosingFunction);
 
   FunctionNode rewrite() {
     // :sync_body(:iterator) {
     //     modified <node.body>;
     // }
     final nestedClosureVariable = new VariableDeclaration(":sync_op");
     final function = new FunctionNode(buildClosureBody(),
         positionalParameters: [iteratorVariable],
         requiredParameterCount: 1,
         asyncMarker: AsyncMarker.SyncYielding)
       ..fileOffset = enclosingFunction.fileOffset
-      ..fileEndOffset = enclosingFunction.fileEndOffset;
+      ..fileEndOffset = enclosingFunction.fileEndOffset
+      ..returnType = helper.coreTypes.boolClass.rawType;
+
     final closureFunction =
         new FunctionDeclaration(nestedClosureVariable, function)
           ..fileOffset = enclosingFunction.parent.fileOffset;
 
     // return new _SyncIterable(:sync_body);
     final arguments = new Arguments([new VariableGet(nestedClosureVariable)]);
     final returnStatement = new ReturnStatement(
         new ConstructorInvocation(helper.syncIterableConstructor, arguments));
 
     enclosingFunction.body = new Block([]
       ..addAll(variableDeclarations())
       ..addAll([closureFunction, returnStatement]));
     enclosingFunction.body.parent = enclosingFunction;
     enclosingFunction.asyncMarker = AsyncMarker.Sync;
     return enclosingFunction;
   }
 
   Statement buildClosureBody() {
     // The body will insert calls to
     //    :iterator.current_=
     //    :iterator.isYieldEach=
     // and return `true` as long as it did something and `false` when it's done.
-    return enclosingFunction.body.accept(this);
+    return new Block([
+        enclosingFunction.body.accept(this),
+        new ReturnStatement(new BoolLiteral(false))
+    ]);
   }
 
   visitYieldStatement(YieldStatement node) {
     var transformedExpression = node.expression.accept(this);
 
     var statements = <Statement>[];
     if (node.isYieldStar) {
       var markYieldEach = new ExpressionStatement(new PropertySet(
           new VariableGet(iteratorVariable),
           new Name("isYieldEach", helper.coreLibrary),
           new BoolLiteral(true)));
       statements.add(markYieldEach);
     }
 
     var setCurrentIteratorValue = new ExpressionStatement(new PropertySet(
         new VariableGet(iteratorVariable),
         new Name("_current", helper.coreLibrary),
         transformedExpression));
 
     statements.add(setCurrentIteratorValue);
     statements.add(createContinuationPoint(new BoolLiteral(true)));
     return new Block(statements);
   }
+
+  TreeNode visitReturnStatement(ReturnStatement node) {
+    // sync* functions cannot return a value.
+    assert(node.expression == null || node.expression is NullLiteral);
+    node.expression = new BoolLiteral(false)..parent = node;
+    return node;
+  }
 }
 
 abstract class AsyncRewriterBase extends ContinuationRewriterBase {
   final VariableDeclaration nestedClosureVariable =
       new VariableDeclaration(":async_op");
   final VariableDeclaration thenContinuationVariable =
       new VariableDeclaration(":async_op_then");
   final VariableDeclaration catchErrorContinuationVariable =
       new VariableDeclaration(":async_op_error");
 
@@ skipping 560 matching lines @@
 class AsyncFunctionRewriter extends AsyncRewriterBase {
   VariableDeclaration completerVariable;
   VariableDeclaration returnVariable;
 
   AsyncFunctionRewriter(helper, enclosingFunction)
       : super(helper, enclosingFunction);
 
   FunctionNode rewrite() {
     var statements = <Statement>[];
 
-    // var :completer = new Completer.sync();
+    // The original function return type should be Future<T> because the
+    // function is async. If it was, we make a Completer<T>.  Otherwise
+    // We will make a malformed type.
+    var future_type = enclosingFunction.returnType;
+    DartType returnType = const DynamicType();
+    if (future_type is InterfaceType) {
+      if (future_type.classNode == helper.futureClass) {
+        if (future_type.typeArguments.length == 0) {
+          returnType = const DynamicType();
+        } else if (future_type.typeArguments.length == 1) {
+          returnType = future_type.typeArguments[0];
+        } else {
+          returnType = const InvalidType();
+        }
+      }
+    }
+    var completerTypeArguments = <DartType>[returnType];
+    var completerType = new InterfaceType(
+        helper.completerClass, completerTypeArguments);
+
+    // final Completer<T> :completer = new Completer<T>.sync();
     completerVariable = new VariableDeclaration(":completer",
         initializer: new StaticInvocation(helper.completerConstructor,
-            new Arguments([], types: [const DynamicType()]))
+            new Arguments([], types: completerTypeArguments))
           ..fileOffset = enclosingFunction.body.fileOffset,
-        isFinal: true);
+        isFinal: true,
+        type: completerType);
     statements.add(completerVariable);
 
-    returnVariable = new VariableDeclaration(":return_value");
+    returnVariable = new VariableDeclaration(
+        ":return_value", type: returnType);
     statements.add(returnVariable);
 
     setupAsyncContinuations(statements);
 
     // new Future.microtask(:async_op);
     var newMicrotaskStatement = new ExpressionStatement(new StaticInvocation(
         helper.futureMicrotaskConstructor,
         new Arguments([new VariableGet(nestedClosureVariable)],
             types: [const DynamicType()]))
       ..fileOffset = enclosingFunction.fileOffset);
@@ skipping 43 matching lines @@
         .add(new ExpressionStatement(new VariableSet(returnVariable, expr)));
     statements
         .add(new BreakStatement(labeledBody)..fileOffset = node.fileOffset);
     return null;
   }
 }
 
 class HelperNodes {
   final Library asyncLibrary;
   final Library coreLibrary;
+  final Class iteratorClass;
+  final Class futureClass;
+  final Class completerClass;
   final Procedure printProcedure;
   final Procedure completerConstructor;
   final Procedure futureMicrotaskConstructor;
   final Constructor streamControllerConstructor;
   final Constructor syncIterableConstructor;
   final Constructor streamIteratorConstructor;
   final Procedure asyncThenWrapper;
   final Procedure asyncErrorWrapper;
   final Procedure awaitHelper;
+  final CoreTypes coreTypes;
 
   HelperNodes(
       this.asyncLibrary,
       this.coreLibrary,
+      this.iteratorClass,
+      this.futureClass,
+      this.completerClass,
       this.printProcedure,
       this.completerConstructor,
       this.syncIterableConstructor,
       this.streamIteratorConstructor,
       this.futureMicrotaskConstructor,
       this.streamControllerConstructor,
       this.asyncThenWrapper,
       this.asyncErrorWrapper,
-      this.awaitHelper);
+      this.awaitHelper,
+      this.coreTypes);
 
   factory HelperNodes.fromProgram(Program program) {
     Library findLibrary(String name) {
       Uri uri = Uri.parse(name);
       for (var library in program.libraries) {
         if (library.importUri == uri) return library;
       }
       throw 'Library "$name" not found';
     }
 
@@ skipping 26 matching lines @@
         }
       }
       throw 'Procedure "$name" not found';
     }
 
     var asyncLibrary = findLibrary('dart:async');
     var coreLibrary = findLibrary('dart:core');
 
     var completerClass = findClass(asyncLibrary, 'Completer');
     var futureClass = findClass(asyncLibrary, 'Future');
+    var iteratorClass = findClass(coreLibrary, 'Iterator');
 
     // The VM's dart:async implementation has renamed _StreamIteratorImpl to
     // _StreamIterator.  To support both old and new library implementations we
     // look for the old name first and then the new name.
     var streamIteratorClass;
     try {
       streamIteratorClass = findClass(asyncLibrary, '_StreamIteratorImpl');
     } catch (e) {
       if (e == 'Class "_StreamIteratorImpl" not found') {
         streamIteratorClass = findClass(asyncLibrary, '_StreamIterator');
       } else {
         rethrow;
       }
     }
 
     var syncIterableClass = findClass(coreLibrary, '_SyncIterable');
     var streamControllerClass =
         findClass(asyncLibrary, '_AsyncStarStreamController');
 
     return new HelperNodes(
         asyncLibrary,
         coreLibrary,
+        iteratorClass,
+        futureClass,
+        completerClass,
         findProcedure(coreLibrary, 'print'),
         findFactoryConstructor(completerClass, 'sync'),
         findConstructor(syncIterableClass, ''),
         findConstructor(streamIteratorClass, ''),
         findFactoryConstructor(futureClass, 'microtask'),
         findConstructor(streamControllerClass, ''),
         findProcedure(asyncLibrary, '_asyncThenWrapperHelper'),
         findProcedure(asyncLibrary, '_asyncErrorWrapperHelper'),
-        findProcedure(asyncLibrary, '_awaitHelper'));
+        findProcedure(asyncLibrary, '_awaitHelper'),
+        new CoreTypes(program));
   }
 }