Better hints for await in non-async functions

pkg/compiler/lib/src/resolution/members.dart

 // Copyright (c) 2012, 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.
 
 part of resolution;
 
 abstract class TreeElements {
   AnalyzableElement get analyzedElement;
   Iterable<Node> get superUses;
 
@@ skipping 2300 matching lines @@
         if (!inInstanceContext) {
           // We report an error within initializers because `this` is implicitly
           // accessed when unqualified identifiers are not resolved.  For
           // details, see section 16.14.3 of the spec (2nd edition):
           //   An unqualified invocation `i` of the form `id(a1, ...)`
           //   ...
           //   If `i` does not occur inside a top level or static function, `i`
           //   is equivalent to `this.id(a1 , ...)`.
           bool inInitializer = enclosingElement.isGenerativeConstructor ||
               (enclosingElement.isInstanceMember && enclosingElement.isField);
-          MessageKind kind = inInitializer
-              ? MessageKind.CANNOT_RESOLVE_IN_INITIALIZER
-              : MessageKind.CANNOT_RESOLVE;
-          element = reportAndCreateErroneousElement(node, node.source, kind,
-              {'name': node.source}, isError: inInitializer);
+          MessageKind kind;
+          Map arguments = {'name': name};
+          if (inInitializer) {
+            kind = MessageKind.CANNOT_RESOLVE_IN_INITIALIZER;
+          } else if (name == 'await') {
+            var functionName = enclosingElement.name;
+            if (functionName == '') {
+              kind = MessageKind.CANNOT_RESOLVE_AWAIT_IN_CLOSURE;
+            } else {
+              kind = MessageKind.CANNOT_RESOLVE_AWAIT;
+              arguments['functionName'] = functionName;
+            }
+          } else {
+            kind = MessageKind.CANNOT_RESOLVE;
+          }
+          element = reportAndCreateErroneousElement(node, name, kind,
+              arguments, isError: inInitializer);
           registry.registerThrowNoSuchMethod();
         }
       } else if (element.isErroneous) {
         // Use the erroneous element.
       } else {
         if ((element.kind.category & allowedCategory) == 0) {
           element = reportAndCreateErroneousElement(
               node, name, MessageKind.GENERIC,
               // TODO(ahe): Improve error message. Need UX input.
               {'text': "is not an expression $element"});
@@ skipping 2798 matching lines @@
 }
 
 /// The result for the resolution of the `assert` method.
 class AssertResult implements ResolutionResult {
   const AssertResult();
 
   Element get element => null;
 
   String toString() => 'AssertResult()';
 }