Add UNDEFINED_HIDDEN_NAME, UNDEFINED_SHOWN_NAME

pkg/analyzer/lib/src/generated/element_resolver.dart

 // Copyright (c) 2014, 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.
 
 library analyzer.src.generated.element_resolver;
 
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
@@ skipping 2070 matching lines @@
         names = combinator.hiddenNames;
       } else {
         names = (combinator as ShowCombinator).shownNames;
       }
       for (SimpleIdentifier name in names) {
         String nameStr = name.name;
         Element element = namespace.get(nameStr);
         if (element == null) {
           element = namespace.get("$nameStr=");
         }
-        if (element != null) {
+        if (element == null) {
+          ErrorCode hintCode;

[Brian Wilkerson, 2016/04/19 14:07:32]

I would prefer to have the hint generation moved to the code that generates the
majority of the hints (can't remember the class name at the moment, but I can
look it up if you'd like). (I'd actually like to remove all hint and error
generation from this class for performance reasons.)

[Brian Wilkerson, 2016/04/20 18:09:57]

To follow up: turns out I couldn't remember because it doesn't exist. Hints are
generated by several classes, but the most appropriate would be
DeadCodeVerifier.

[srawlins, 2016/04/20 20:34:01]

Done.

+          if (combinator is HideCombinator) {
+            hintCode = HintCode.UNDEFINED_HIDDEN_NAME;
+          } else {
+            hintCode = HintCode.UNDEFINED_SHOWN_NAME;
+          }
+          _recordUndefinedNode(null /*declaringElement*/, hintCode, name, [nameStr]);
+        } else {
           // Ensure that the name always resolves to a top-level variable
           // rather than a getter or setter
           if (element is PropertyAccessorElement) {
             element = (element as PropertyAccessorElement).variable;
           }
           name.staticElement = element;
         }
       }
     }
   }
@@ skipping 483 matching lines @@
 
   @override
   Element get staticElement => null;
 
   @override
   dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) => null;
 
   @override
   void visitChildren(AstVisitor visitor) {}
 }