Fix await parsing.

pkg/compiler/lib/src/typechecker.dart

Index: pkg/compiler/lib/src/typechecker.dart
diff --git a/pkg/compiler/lib/src/typechecker.dart b/pkg/compiler/lib/src/typechecker.dart
index 26272a918483b0cec84ffd100ce6a4a1c5d6befb..68139d08a3673743716b3f5b2701725a645bd996 100644
--- a/pkg/compiler/lib/src/typechecker.dart
+++ b/pkg/compiler/lib/src/typechecker.dart
@@ -1601,17 +1601,19 @@ class TypeCheckerVisitor extends Visitor<DartType> {
     return const DynamicType();
   }
 
-  DartType visitAwait(Await node) {
-    DartType expressionType = analyze(node.expression);
-    DartType resultType = expressionType;
-    if (expressionType is InterfaceType) {
-      InterfaceType futureType =
-          expressionType.asInstanceOf(compiler.futureClass);
+  DartType flatten(DartType type) {

[floitsch, 2015/02/03 13:34:21]

add comment.

[floitsch, 2015/02/03 13:34:21]

If I understand correctly this reduces the type of Future<Future<Future<int>>>
to int. I'm not sure how much this makes sense. A Future<Future<int>> will have
a dynamic error, since its T will never match the correct runtime type (which
would be 'int').

[floitsch, 2015/02/03 13:34:21]

This seems to be very await specific (talking about 'future'). rename function?

[Johnni Winther, 2015/02/03 14:12:56]

It term 'flatten' is from the spec is used to describe the static typing of
await and type checking of return (no implemented yet).

[Johnni Winther, 2015/02/03 14:12:56]

Done.

+    if (type is InterfaceType) {
+      InterfaceType futureType = type.asInstanceOf(compiler.futureClass);
       if (futureType != null) {
-        resultType = futureType.typeArguments.first;
+        return flatten(futureType.typeArguments.first);
       }
     }
-    return resultType;
+    return type;
+  }
+
+  DartType visitAwait(Await node) {
+    DartType expressionType = analyze(node.expression);
+    return flatten(expressionType);
   }
 
   DartType visitYield(Yield node) {