Eliminate redundant signatures.

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 1786 matching lines @@
     var tInstanceSetters = <JS.Property>[];
     var sNames = <JS.Expression>[];
     for (MethodDeclaration node in methods) {
       var name = node.name.name;
       var element = resolutionMap.elementDeclaredByMethodDeclaration(node);
       // TODO(vsm): Clean up all the nasty duplication.
       if (node.isAbstract) {
         continue;
       }
 
+      List<JS.Property> tMember;
+      Function getOverride;
       Function lookup;
-      List<JS.Property> tMember;
+      Function elementToType;
       if (node.isGetter) {
-        lookup = classElem.lookUpInheritedConcreteGetter;
+        elementToType = (ExecutableElement element) => element.type;
+        getOverride = classElem.lookUpInheritedConcreteGetter;
+        lookup = classElem.type.lookUpInheritedGetter;
         tMember = node.isStatic ? tStaticGetters : tInstanceGetters;
       } else if (node.isSetter) {
-        lookup = classElem.lookUpInheritedConcreteSetter;
+        elementToType = (ExecutableElement element) => element.type;
+        getOverride = classElem.lookUpInheritedConcreteSetter;
+        lookup = classElem.type.lookUpInheritedSetter;
         tMember = node.isStatic ? tStaticSetters : tInstanceSetters;
       } else {
         // Method
-        lookup = classElem.lookUpInheritedConcreteMethod;
+        // Swap in "Object" for parameter types that are covariant overrides.
+        var objectType = context.typeProvider.objectType;
+        elementToType =
+            (MethodElement element) => element.getReifiedType(objectType);
+        getOverride = classElem.lookUpInheritedConcreteMethod;
+        lookup = classElem.type.lookUpInheritedMethod;
         tMember = node.isStatic ? tStaticMethods : tInstanceMethods;
       }
 
-      // Swap in "Object" for parameter types that are covariant overrides.
-      var objectType = context.typeProvider.objectType;
-      var reifiedType = element is MethodElement
-          ? element.getReifiedType(objectType)
-          : element.type;
+      DartType reifiedType = elementToType(element);
       var type = _emitAnnotatedFunctionType(reifiedType, node.metadata,
           parameters: node.parameters?.parameters,
           nameType: options.hoistSignatureTypes,
           hoistType: options.hoistSignatureTypes,
           definite: true);
 
       // Don't add redundant signatures for inherited methods whose signature
-      // did not change.
-      var needsSignature = true;
-      var inheritedElement = lookup(name, currentLibrary);
-      if (inheritedElement != null) {
-        if (inheritedElement is MethodElement) {
-          needsSignature =
-              inheritedElement.getReifiedType(objectType) != reifiedType;
-        } else {
-          needsSignature = inheritedElement.type != reifiedType;
-        }
-      }
+      // did not change.  If we are not overriding, or if the thing we are
+      // overriding has a different reified type from ourselves, we must
+      // emit a signature on this class.  Otherwise we will inherit the
+      // signature from the superclass.
+      var needsSignature = getOverride(name, currentLibrary) == null ||
+          elementToType(
+                  lookup(name, library: currentLibrary, thisType: false)) !=
+              reifiedType;
 
       if (needsSignature) {
         var memberName = _declareMemberName(element);
         var property = new JS.Property(memberName, type);
         tMember.add(property);
         // TODO(vsm): Why do we need this?
         if (node.isStatic && !node.isGetter && !node.isSetter) {
           sNames.add(memberName);
         }
       }
@@ skipping 3995 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;
 }