update unnecessary_const for case patterns (#4050)

Author: pq

lib/src/rules/unnecessary_const.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/ast/ast.dart';
 import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
@@ -51,7 +52,8 @@ class UnnecessaryConst extends LintRule {
   @override
   void registerNodeProcessors(
       NodeLintRegistry registry, LinterContext context) {
-    var visitor = _Visitor(this);
+    var visitor =
+        _Visitor(this, patternsEnabled: context.isEnabled(Feature.patterns));
     registry.addInstanceCreationExpression(this, visitor);
     registry.addListLiteral(this, visitor);
     registry.addRecordLiteral(this, visitor);
@@ -61,7 +63,8 @@ class UnnecessaryConst extends LintRule {
 
 class _Visitor extends SimpleAstVisitor {
   final LintRule rule;
-  _Visitor(this.rule);
+  final bool patternsEnabled;
+  _Visitor(this.rule, {required this.patternsEnabled});
 
   @override
   void visitInstanceCreationExpression(InstanceCreationExpression node) {
@@ -73,7 +76,10 @@ class _Visitor extends SimpleAstVisitor {
   }
 
   @override
-  void visitListLiteral(ListLiteral node) => _visitTypedLiteral(node);
+  void visitListLiteral(ListLiteral node) {
+    if (patternsEnabled) return;
+    _visitTypedLiteral(node);
+  }
 
   @override
   void visitRecordLiteral(RecordLiteral node) {
@@ -86,6 +92,7 @@ class _Visitor extends SimpleAstVisitor {
 
   @override
   void visitSetOrMapLiteral(SetOrMapLiteral node) {
+    if (patternsEnabled) return;
     _visitTypedLiteral(node);
   }
 

test/rules/unnecessary_const_test.dart

@@ -8,12 +8,65 @@ import '../rule_test_support.dart';
 
 main() {
   defineReflectiveSuite(() {
-    defineReflectiveTests(UnnecessaryConstTest);
+    defineReflectiveTests(UnnecessaryConstPatternsTest);
+    defineReflectiveTests(UnnecessaryConstRecordsTest);
   });
 }
 
 @reflectiveTest
-class UnnecessaryConstTest extends LintRuleTest {
+class UnnecessaryConstPatternsTest extends LintRuleTest {
+  @override
+  List<String> get experiments => ['patterns', 'records'];
+
+  @override
+  String get lintRule => 'unnecessary_const';
+
+  test_case_constConstructor_ok() async {
+    await assertNoDiagnostics(r'''
+class C {
+  const C();
+}
+f(C c) {
+  switch (c) {
+    case const C():
+  }
+}
+''');
+  }
+
+  test_case_listLiteral_ok() async {
+    await assertNoDiagnostics(r'''
+void f(Object o) {
+  switch (o) {
+    case const [1, 2]:
+  }
+}
+''');
+  }
+
+  test_case_mapLiteral_ok() async {
+    await assertNoDiagnostics(r'''
+void f(Object o) {
+  switch (o) {
+   case const {'k': 'v'}:
+  }
+}
+''');
+  }
+
+  test_case_setLiteral_ok() async {
+    await assertNoDiagnostics(r'''
+void f(Object o) {
+  switch (o) {
+    case const {1}:
+  }
+}
+''');
+  }
+}
+
+@reflectiveTest
+class UnnecessaryConstRecordsTest extends LintRuleTest {
   @override
   List<String> get experiments => ['records'];