fixes #221, initial sync*, async, async* implementation

lib/src/info.dart

Index: lib/src/info.dart
diff --git a/lib/src/info.dart b/lib/src/info.dart
index 5da0f644c3a0694d3faef695fa4326df58da74e4..a154cf9219ef3518292d939ca17b9a5b8d39e0c8 100644
--- a/lib/src/info.dart
+++ b/lib/src/info.dart
@@ -91,6 +91,16 @@ class _AstCloner extends AstCloner {
     }
     return clone;
   }
+
+  // TODO(jmesserly): as a workaround for analyzer <0.26.0-alpha.1.
+  // ResolutionCopier won't copy the type, so we do it here.
+  @override
+  AwaitExpression visitAwaitExpression(AwaitExpression node) {
+    var clone = super.visitAwaitExpression(node);
+    clone.staticType = node.staticType;
+    clone.propagatedType = node.propagatedType;
+    return clone;
+  }
 }
 
 // The abstract type of coercions mapping one type to another.