[wildcards] prefer_final_parameters support

Fixes: https://github.com/dart-lang/linter/issues/5044

Change-Id: Ibbf24df34133cfa75deed357733c2ae0637251f5
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/378902
Reviewed-by: Brian Wilkerson <[email protected]>
Commit-Queue: Phil Quitslund <[email protected]>

Author: pq

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

@@ -4,6 +4,7 @@
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
+import 'package:analyzer/src/dart/element/extensions.dart'; //ignore: implementation_imports
 
 import '../analyzer.dart';
 
@@ -130,6 +131,7 @@ class _Visitor extends SimpleAstVisitor<void> {
         var declaredElement = param.declaredElement;
         if (declaredElement != null &&
             !declaredElement.isInitializingFormal &&
+            !declaredElement.isWildcardVariable &&
             !body.isPotentiallyMutatedInScope(declaredElement)) {
           rule.reportLint(param, arguments: [param.name!.lexeme]);
         }

pkg/linter/test/rules/prefer_final_parameters_test.dart

@@ -62,6 +62,20 @@ void f(final List<int> x) {
     ]);
   }
 
+  test_closure_wildcard() async {
+    await assertNoDiagnostics(r'''
+var f = (Object _) { };
+''');
+  }
+
+  test_constructor_unused_wildcard() async {
+    await assertNoDiagnostics(r'''
+class C {
+  C(String _);
+}
+''');
+  }
+
   test_constructor_usedInBody() async {
     await assertDiagnostics(r'''
 class C {
@@ -158,6 +172,22 @@ class C {
 ''');
   }
 
+  test_method_wildcard() async {
+    await assertNoDiagnostics(r'''
+class C {
+  void m(String _) { }
+}
+''');
+  }
+
+  test_method_wildcard_final() async {
+    await assertNoDiagnostics(r'''
+class C {
+  void m(final String _) { }
+}
+''');
+  }
+
   test_operator() async {
     await assertDiagnostics(r'''
 class C {
@@ -180,6 +210,16 @@ class C {
 ''');
   }
 
+  test_operator_wildcard() async {
+    await assertNoDiagnostics(r'''
+class C {
+  C operator +(C _) {
+    return this;
+  }
+}
+''');
+  }
+
   test_recordPattern_destructured() async {
     await assertNoDiagnostics(r'''
 void f(int a, int b) {
@@ -208,6 +248,14 @@ class C {
 ''');
   }
 
+  test_setter_wildcard() async {
+    await assertNoDiagnostics(r'''
+class C {
+  void set f(int _) { }
+}
+''');
+  }
+
   test_superParameter() async {
     await assertNoDiagnostics('''
 class D {
@@ -274,6 +322,16 @@ void f({final String? p}) {
 ''');
   }
 
+  test_topLevelFunction_named_wildcard() async {
+    await assertDiagnostics(r'''
+void f({final String? _}) { }
+''', [
+      // No lint.
+      // https://github.com/dart-lang/language/blob/main/working/wildcards/feature-specification.md#declarations-that-are-capable-of-declaring-a-wildcard
+      error(CompileTimeErrorCode.PRIVATE_OPTIONAL_PARAMETER, 22, 1),
+    ]);
+  }
+
   test_topLevelFunction_namedRequired() async {
     await assertDiagnostics(r'''
 void f({required String p}) {
@@ -292,6 +350,16 @@ void f({required final String p}) {
 ''');
   }
 
+  test_topLevelFunction_namedRequired_wildcard() async {
+    await assertDiagnostics(r'''
+void f({required String _}) { }
+''', [
+      // No lint.
+      // https://github.com/dart-lang/language/blob/main/working/wildcards/feature-specification.md#declarations-that-are-capable-of-declaring-a-wildcard
+      error(CompileTimeErrorCode.PRIVATE_OPTIONAL_PARAMETER, 24, 1),
+    ]);
+  }
+
   test_topLevelFunction_optional() async {
     await assertDiagnostics(r'''
 void f([String? p]) {
@@ -307,6 +375,18 @@ void f([String? p]) {
 void f([final String? p]) {
   print(p);
 }
+''');
+  }
+
+  test_topLevelFunction_optional_wildcard() async {
+    await assertNoDiagnostics(r'''
+void f([String? _]) { }
+''');
+  }
+
+  test_topLevelFunction_wildcard() async {
+    await assertNoDiagnostics(r'''
+void f(int _){ }
 ''');
   }
 }