Further reduce use of Element in codegen.

pkg/compiler/lib/src/compiler.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.
 
 library dart2js.compiler_base;
 
 import 'dart:async' show EventSink, Future;
 
 import '../compiler_new.dart' as api;
 import 'cache_strategy.dart' show CacheStrategy;
@@ skipping 1456 matching lines @@
     return element;
   }
 
   ConstructorElement _unnamedListConstructor;
   ConstructorElement get unnamedListConstructor =>
       _unnamedListConstructor ??= listClass.lookupDefaultConstructor();
 
   ConstructorElement _filledListConstructor;
   ConstructorElement get filledListConstructor =>
       _filledListConstructor ??= listClass.lookupConstructor("filled");
+
+  // TODO(johnniwinther): Change types to `ClassElement` when these are not
+  // called with unrelated elements.
+  bool isNumberOrStringSupertype(/*Class*/ Element element) {
+    return element == coreLibrary.find('Comparable');
+  }
+
+  bool isStringOnlySupertype(/*Class*/ Element element) {
+    return element == coreLibrary.find('Pattern');
+  }
+
+  bool isListSupertype(/*Class*/ Element element) => element == iterableClass;
 }
 
 class CompilerDiagnosticReporter extends DiagnosticReporter {
   final Compiler compiler;
   final DiagnosticOptions options;
 
   Element _currentElement;
   bool hasCrashed = false;
 
   /// `true` if the last diagnostic was filtered, in which case the
@@ skipping 725 matching lines @@
   _ElementScanner(this.scanner);
   void scanLibrary(LibraryElement library) => scanner.scanLibrary(library);
   void scanUnit(CompilationUnitElement unit) => scanner.scan(unit);
 }
 
 class _EmptyEnvironment implements Environment {
   const _EmptyEnvironment();
 
   String valueOf(String key) => null;
 }