Store the declared element locally for unnamed extensions

We normally store the declared element for a declaration in the name of
the declaration. We still do that when there _is_ a name for an extension,
but we also store it directly on the extension so that we can handle
unnamed extensions.

Change-Id: Id8a8bc01be5d2fbfd86ea5ec4ff150165b31a9bb
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/109554
Reviewed-by: Konstantin Shcheglov <[email protected]>
Reviewed-by: Phil Quitslund <[email protected]>
Commit-Queue: Brian Wilkerson <[email protected]>

Author: bwilkerson

pkg/analyzer/lib/src/dart/ast/ast.dart

@@ -3850,6 +3850,8 @@ class ExtensionDeclarationImpl extends CompilationUnitMemberImpl
   @override
   Token rightBracket;
 
+  ExtensionElement _declaredElement;
+
   ExtensionDeclarationImpl(
       CommentImpl comment,
       List<Annotation> metadata,
@@ -3883,10 +3885,15 @@ class ExtensionDeclarationImpl extends CompilationUnitMemberImpl
     ..add(rightBracket);
 
   @override
-  Element get declaredElement => name.staticElement;
+  ExtensionElement get declaredElement => _declaredElement;
+
+  /// Set the element declared by this declaration to the given [element].
+  set declaredElement(ExtensionElement element) {
+    _declaredElement = element;
+  }
 
   @override
-  Element get element => name.staticElement;
+  ExtensionElement get element => declaredElement;
 
   @override
   Token get endToken => rightBracket;

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

@@ -186,6 +186,7 @@ class DeclarationResolver extends RecursiveAstVisitor<void> {
   @override
   void visitExtensionDeclaration(ExtensionDeclaration node) {
     ExtensionElement element = _match(node.name, _walker.getExtension());
+    (node as ExtensionDeclarationImpl).declaredElement = element;
     _walk(new ElementWalker.forExtension(element), () {
       super.visitExtensionDeclaration(node);
     });