[wildcards] DUPLICATE_DEFINITION support

Fixes: #56089

I'll follow-up with more tests for `DUPLICATE_FIELD_FORMAL_PARAMETER`s in another CL (see: #56092).

Change-Id: I23b13e697df6d16f856fef54b0fcf2a5db47bb22
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/373404
Commit-Queue: Phil Quitslund <pquitslund@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>

pkg/analyzer/lib/src/dart/element/extensions.dart

@@ -2,6 +2,7 @@
 // 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 'package:analyzer/dart/analysis/features.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/nullability_suffix.dart';
 import 'package:analyzer/dart/element/type.dart';
@@ -116,6 +117,16 @@ extension ElementExtension on Element {
     }
     return false;
   }
+
+  /// Return true if this element is a wildcard variable.
+  bool get isWildcardVariable =>
+      name == '_' &&
+      (this is LocalVariableElement ||
+          this is TypeParameterElement ||
+          (this is ParameterElement &&
+              this is! FieldFormalParameterElement &&
+              this is! SuperFormalParameterElement)) &&
+      (library?.featureSet.isEnabled(Feature.wildcard_variables) ?? false);
 }
 
 extension ExecutableElementExtension on ExecutableElement {

pkg/analyzer/lib/src/dart/element/scope.dart

@@ -7,6 +7,7 @@ import 'package:analyzer/dart/analysis/features.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/scope.dart';
 import 'package:analyzer/src/dart/element/element.dart';
+import 'package:analyzer/src/dart/element/extensions.dart';
 import 'package:analyzer/src/summary2/combinator.dart';
 import 'package:analyzer/src/utilities/extensions/collection.dart';
 
@@ -440,10 +441,3 @@ class _LibraryOrAugmentationImportScope implements Scope {
     return _nullPrefixScope.lookup(id);
   }
 }
-
-extension on Element {
-  bool get isWildcardVariable =>
-      name == '_' &&
-      (this is LocalVariableElement || this is ParameterElement) &&
-      (library?.featureSet.isEnabled(Feature.wildcard_variables) ?? false);
-}

pkg/analyzer/lib/src/error/duplicate_definition_verifier.dart

@@ -9,6 +9,7 @@ import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/error/error.dart';
 import 'package:analyzer/error/listener.dart';
 import 'package:analyzer/src/dart/ast/ast.dart';
+import 'package:analyzer/src/dart/element/extensions.dart';
 import 'package:analyzer/src/dart/element/inheritance_manager3.dart';
 import 'package:analyzer/src/diagnostic/diagnostic_factory.dart';
 import 'package:analyzer/src/error/codes.dart';
@@ -33,6 +34,8 @@ class DuplicateDefinitionVerifier {
     var exceptionParameter = node.exceptionParameter;
     var stackTraceParameter = node.stackTraceParameter;
     if (exceptionParameter != null && stackTraceParameter != null) {
+      var element = exceptionParameter.declaredElement;
+      if (element != null && element.isWildcardVariable) return;
       String exceptionName = exceptionParameter.name.lexeme;
       if (exceptionName == stackTraceParameter.name.lexeme) {
         _errorReporter.reportError(_diagnosticFactory
@@ -533,7 +536,7 @@ class DuplicateDefinitionVerifier {
   void _checkDuplicateIdentifier(
       Map<String, Element> getterScope, Token identifier,
       {required Element element, Map<String, Element>? setterScope}) {
-    if (identifier.isSynthetic) {
+    if (identifier.isSynthetic || element.isWildcardVariable) {
       return;
     }