Collect defined elements together with used elements.

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

Index: pkg/analyzer/lib/src/generated/resolver.dart
diff --git a/pkg/analyzer/lib/src/generated/resolver.dart b/pkg/analyzer/lib/src/generated/resolver.dart
index ecfe2049c611843dc861a4ce6229e8b30173263d..cbe793ef2575dbbc6ef3b3de6d57d67f666646a4 100644
--- a/pkg/analyzer/lib/src/generated/resolver.dart
+++ b/pkg/analyzer/lib/src/generated/resolver.dart
@@ -4001,6 +4001,7 @@ class GatherUsedImportedElementsVisitor extends RecursiveAstVisitor {
  * An [AstVisitor] that fills [UsedLocalElements].
  */
 class GatherUsedLocalElementsVisitor extends RecursiveAstVisitor {
+  final List<Element> definedElements = <Element>[];
   final UsedLocalElements usedElements = new UsedLocalElements();
 
   final LibraryElement _enclosingLibrary;
@@ -4070,10 +4071,11 @@ class GatherUsedLocalElementsVisitor extends RecursiveAstVisitor {
 
   @override
   visitSimpleIdentifier(SimpleIdentifier node) {
+    Element element = node.staticElement;
     if (node.inDeclarationContext()) {
+      definedElements.add(element);
       return;
     }
-    Element element = node.staticElement;
     bool isIdentifierRead = _isReadIdentifier(node);
     if (element is LocalVariableElement) {
       if (isIdentifierRead) {
@@ -12148,7 +12150,7 @@ class TypeResolverVisitor extends ScopedVisitor {
  * structure looking for cases of [HintCode.UNUSED_ELEMENT],
  * [HintCode.UNUSED_FIELD], [HintCode.UNUSED_LOCAL_VARIABLE], etc.
  */
-class UnusedLocalElementsVerifier extends RecursiveElementVisitor {
+class UnusedLocalElementsVerifier extends SimpleElementVisitor {
   /**
    * The error listener to which errors will be reported.
    */
@@ -12173,6 +12175,24 @@ class UnusedLocalElementsVerifier extends RecursiveElementVisitor {
     super.visitClassElement(element);
   }
 
+  visitElement(Element element) {

[Paul Berry, 2016/02/09 20:34:25]

Why not simply:

    element.accept(this);

Or better yet, do it at the call site and then you don't need this method at
all.

[Brian Wilkerson, 2016/02/09 20:35:57]

I was about to make the same comment. After all, one point of a visitor pattern
is to avoid this kind of 'is' test.

+    if (element is ClassElement) {
+      visitClassElement(element);
+    } else if (element is FieldElement) {
+      visitFieldElement(element);
+    } else if (element is FunctionElement) {
+      visitFunctionElement(element);
+    } else if (element is FunctionTypeAliasElement) {
+      visitFunctionTypeAliasElement(element);
+    } else if (element is LocalVariableElement) {
+      visitLocalVariableElement(element);
+    } else if (element is MethodElement) {
+      visitMethodElement(element);
+    } else if (element is PropertyAccessorElement) {
+      visitPropertyAccessorElement(element);
+    }
+  }
+
   @override
   visitFieldElement(FieldElement element) {
     if (!_isReadMember(element)) {