pattern support for no_leading_underscores_for_local_identifiers (#4133)

* init

* ++

* sort

* fmt

* operand fixes

* re-add

* => visitDeclaredVariablePattern

Author: pq

lib/src/rules/no_leading_underscores_for_local_identifiers.dart

@@ -75,6 +75,7 @@ class NoLeadingUnderscoresForLocalIdentifiers extends LintRule {
     registry.addFormalParameterList(this, visitor);
     registry.addForPartsWithDeclarations(this, visitor);
     registry.addFunctionDeclarationStatement(this, visitor);
+    registry.addDeclaredVariablePattern(this, visitor);
     registry.addVariableDeclarationStatement(this, visitor);
   }
 }
@@ -103,6 +104,11 @@ class _Visitor extends SimpleAstVisitor<void> {
     checkIdentifier(node.name);
   }
 
+  @override
+  void visitDeclaredVariablePattern(DeclaredVariablePattern node) {
+    checkIdentifier(node.name);
+  }
+
   @override
   void visitFormalParameterList(FormalParameterList node) {
     for (var parameter in node.parameters) {

test/rules/all.dart

@@ -55,6 +55,8 @@ import 'literal_only_boolean_expressions_test.dart'
 import 'missing_whitespace_between_adjacent_strings_test.dart'
     as missing_whitespace_between_adjacent_strings;
 import 'no_duplicate_case_values_test.dart' as no_duplicate_case_values;
+import 'no_leading_underscores_for_local_identifiers_test.dart'
+    as no_leading_underscores_for_local_identifiers;
 import 'non_adjacent_strings_in_list_test.dart' as no_adjacent_strings_in_list;
 import 'non_constant_identifier_names_test.dart'
     as non_constant_identifier_names;
@@ -158,6 +160,7 @@ void main() {
   missing_whitespace_between_adjacent_strings.main();
   no_adjacent_strings_in_list.main();
   no_duplicate_case_values.main();
+  no_leading_underscores_for_local_identifiers.main();
   non_constant_identifier_names.main();
   null_check_on_nullable_type_parameter.main();
   null_closures.main();

test/rules/no_leading_underscores_for_local_identifiers_test.dart

@@ -0,0 +1,123 @@
+// Copyright (c) 2023, the Dart project authors. Please see the AUTHORS file
+// 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:test_reflective_loader/test_reflective_loader.dart';
+
+import '../rule_test_support.dart';
+
+main() {
+  defineReflectiveSuite(() {
+    defineReflectiveTests(NoLeadingUnderscoresForLocalIdentifiersTest);
+  });
+}
+
+@reflectiveTest
+class NoLeadingUnderscoresForLocalIdentifiersTest extends LintRuleTest {
+  @override
+  List<String> get experiments => ['patterns', 'records'];
+
+  @override
+  String get lintRule => 'no_leading_underscores_for_local_identifiers';
+
+  test_listPattern_switch() async {
+    await assertDiagnostics(r'''
+f() {
+  switch ([1,2]) {
+    case [1 && var _a, 2 && var b]: print('$_a$b');
+  }
+}
+''', [
+      lint(44, 2),
+    ]);
+  }
+
+  test_listPattern_switch_leftOperand() async {
+    await assertDiagnostics(r'''
+f() {
+  switch ([1,2]) {
+    case [var _a && 1, 2 && var b]: print('$_a$b');
+  }
+}
+''', [
+      lint(39, 2),
+    ]);
+  }
+
+  test_mapPattern_destructured() async {
+    await assertDiagnostics(r'''
+f() {
+  final {'first': _a, 'second': b} = {'first': 1, 'second': 2};
+  print('$_a$b');
+}
+''', [
+      lint(24, 2),
+    ]);
+  }
+
+  test_mapPattern_switch() async {
+    await assertDiagnostics(r'''
+f() {
+  switch ({1: 2}) {
+    case {'a': var _a, 'b': var b} : print('$_a$b');
+  }
+}
+''', [
+      lint(45, 2),
+    ]);
+  }
+
+  test_objectPattern_destructured() async {
+    await assertDiagnostics(r'''
+class A {
+  int a;
+  A(this.a);
+}
+f() {
+  final A(a: _b) = A(1);
+  print('$_b');
+}
+''', [
+      lint(53, 2),
+    ]);
+  }
+
+  test_objectPattern_switch() async {
+    await assertDiagnostics(r'''
+class A {
+  int a;
+  A(this.a);
+}
+f() {
+  switch (A(1)) {
+    case A(a: >0 && var _b): print('$_b');
+  }
+}
+''', [
+      lint(82, 2),
+    ]);
+  }
+
+  test_recordPattern_destructured() async {
+    await assertDiagnostics(r'''
+f() {
+  var (_a, b) = ('a', 'b');
+  print('$_a$b');
+}
+''', [
+      lint(13, 2),
+    ]);
+  }
+
+  test_recordPattern_switch() async {
+    await assertDiagnostics(r'''
+f() {
+  switch ((1, 2)) {
+    case (var _a, var b): print('$_a$b');
+  }
+}
+''', [
+      lint(40, 2),
+    ]);
+  }
+}