Fixes #246

Type checks await

[email protected]

Review URL: https://codereview.chromium.org/1209413002.

Author: vsmenon

pkg/dev_compiler/lib/src/checker/checker.dart

@@ -670,6 +670,12 @@ class CodeChecker extends RecursiveAstVisitor {
     node.visitChildren(this);
   }
 
+  @override
+  void visitAwaitExpression(AwaitExpression node) {
+    checkAssignment(node.expression, _rules.provider.futureDynamicType);
+    node.visitChildren(this);
+  }
+
   @override
   void visitPropertyAccess(PropertyAccess node) {
     var target = node.realTarget;

pkg/dev_compiler/test/checker/checker_test.dart

@@ -2686,6 +2686,16 @@ void main() {
         Future bar2() async { return x; }
         Future<int> bar3() async { return (/*info:DynamicCast*/x); }
         Future<int> bar4() async { return (/*severe:StaticTypeError*/new Future<int>(x)); }
+
+        int y;
+        Future<int> z;
+
+        void baz() async {
+          int a = /*info:DynamicCast*/await /*info:DynamicCast*/x;
+          int b = await /*severe:StaticTypeError*/y;
+          int c = await z;
+          String d = /*severe:StaticTypeError*/await z;
+        }
     '''
     }));