fix #29585, implement equality for tearoffs

pkg/dev_compiler/lib/src/compiler/code_generator.dart

 // Copyright (c) 2015, 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.
 
 import 'dart:collection' show HashMap, HashSet;
 import 'dart:math' show min, max;
 
 import 'package:analyzer/analyzer.dart' hide ConstantEvaluator;
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 3764 matching lines @@
             return (element as InterpolationString).value;
           }
         }).join();
       } else {
         templateArgs = args.skip(2).toList();
         source = (code as StringLiteral).stringValue;
       }
 
       // TODO(vsm): Constructors in dart:html and friends are trying to
       // allocate a type defined on window/self, but this often conflicts a
-      // with the generated extenstion class in scope.  We really should
+      // with the generated extension class in scope.  We really should
       // qualify explicitly in dart:html itself.
       var constructorPattern = new RegExp("new [A-Z][A-Za-z]+\\(");
       if (constructorPattern.matchAsPrefix(source) != null) {
         var containingClass = node.parent;
         while (
             containingClass != null && containingClass is! ClassDeclaration) {
           containingClass = containingClass.parent;
         }
         if (containingClass is ClassDeclaration &&
             _extensionTypes.isNativeClass(containingClass.element)) {
@@ skipping 2332 matching lines @@
   if (targetIdentifier.staticElement is! PrefixElement) return false;
   var prefix = targetIdentifier.staticElement as PrefixElement;
 
   // The library the prefix is referring to must come from a deferred import.
   var containingLibrary = resolutionMap
       .elementDeclaredByCompilationUnit(target.root as CompilationUnit)
       .library;
   var imports = containingLibrary.getImportsWithPrefix(prefix);
   return imports.length == 1 && imports[0].isDeferred;
 }