Set the right context to resolve types of fields, closures and parameters.

lib/compiler/implementation/elements/elements.dart

Index: lib/compiler/implementation/elements/elements.dart
diff --git a/lib/compiler/implementation/elements/elements.dart b/lib/compiler/implementation/elements/elements.dart
index e18f1888a16f531db3e7006d9a7af637d43eaa05..e55f63db301516703c223ce23d72ef5da0bc3c7f 100644
--- a/lib/compiler/implementation/elements/elements.dart
+++ b/lib/compiler/implementation/elements/elements.dart
@@ -179,6 +179,13 @@ class Element implements Hashable {
     return null;
   }
 
+  Element getEnclosingMember() {
+    for (Element e = this; e !== null; e = e.enclosingElement) {
+      if (e.isMember()) return e;
+    }
+    return null;
+  }
+
   toString() => '$kind(${name.slowToString()})';
 
   bool _isNative = false;