[wildcards] support for avoid_shadowing_type_parameters

Fixes: https://github.com/dart-lang/linter/issues/5046

Change-Id: I689634f1f3597eeb2145a7a5f01b990d56d2c6ee
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/379001
Reviewed-by: Brian Wilkerson <[email protected]>
Commit-Queue: Phil Quitslund <[email protected]>

Author: pq

pkg/linter/lib/src/rules/avoid_shadowing_type_parameters.dart

@@ -2,8 +2,10 @@
 // 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/ast/ast.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
+import 'package:analyzer/dart/element/element.dart';
 
 import '../analyzer.dart';
 
@@ -47,17 +49,22 @@ class AvoidShadowingTypeParameters extends LintRule {
   @override
   void registerNodeProcessors(
       NodeLintRegistry registry, LinterContext context) {
-    var visitor = _Visitor(this);
+    var visitor = _Visitor(this, context.libraryElement);
     registry.addFunctionDeclarationStatement(this, visitor);
     registry.addGenericTypeAlias(this, visitor);
     registry.addMethodDeclaration(this, visitor);
   }
 }
 
 class _Visitor extends SimpleAstVisitor<void> {
+  /// Whether the `wildcard_variables` feature is enabled.
+  final bool _wildCardVariablesEnabled;
+
   final LintRule rule;
 
-  _Visitor(this.rule);
+  _Visitor(this.rule, LibraryElement? library)
+      : _wildCardVariablesEnabled =
+            library?.featureSet.isEnabled(Feature.wildcard_variables) ?? false;
 
   @override
   void visitFunctionDeclarationStatement(FunctionDeclarationStatement node) {
@@ -126,7 +133,9 @@ class _Visitor extends SimpleAstVisitor<void> {
         .toSet();
 
     for (var parameter in typeParameters.typeParameters) {
-      if (ancestorTypeParameterNames.contains(parameter.name.lexeme)) {
+      var lexeme = parameter.name.lexeme;
+      if (_wildCardVariablesEnabled && lexeme == '_') continue;
+      if (ancestorTypeParameterNames.contains(lexeme)) {
         rule.reportLint(parameter,
             arguments: [parameter.name.lexeme, ancestorKind]);
       }

pkg/linter/test/rules/avoid_shadowing_type_parameters_test.dart

@@ -38,6 +38,14 @@ extension type E<T>(int i) {
     ]);
   }
 
+  test_wildcards() async {
+    await assertNoDiagnostics(r'''
+class A<_> {
+  void f<_>() {}
+}
+''');
+  }
+
   test_wrongNumberOfTypeArguments() async {
     await assertDiagnostics(r'''
 typedef Predicate = bool <E>(E element);