extension type support for unnecessary_getters_setters

Fixes: https://github.com/dart-lang/linter/issues/4711

Change-Id: I79d75c3f9bd17333b9e1370f9057202a0c9cce6f
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/322500
Reviewed-by: Brian Wilkerson <[email protected]>
Commit-Queue: Phil Quitslund <[email protected]>

Author: pq

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

@@ -68,6 +68,7 @@ class UnnecessaryGettersSetters extends LintRule {
       NodeLintRegistry registry, LinterContext context) {
     var visitor = _Visitor(this);
     registry.addClassDeclaration(this, visitor);
+    registry.addExtensionTypeDeclaration(this, visitor);
   }
 }
 
@@ -81,6 +82,11 @@ class _Visitor extends SimpleAstVisitor<void> {
     _check(node.members);
   }
 
+  @override
+  void visitExtensionTypeDeclaration(ExtensionTypeDeclaration node) {
+    _check(node.members);
+  }
+
   void _check(NodeList<ClassMember> members) {
     var getters = <String, MethodDeclaration>{};
     var setters = <String, MethodDeclaration>{};

pkg/linter/test/rules/unnecessary_getters_setters_test.dart

@@ -14,6 +14,9 @@ main() {
 
 @reflectiveTest
 class UnnecessaryGettersSettersTest extends LintRuleTest {
+  @override
+  List<String> get experiments => ['inline-class'];
+
   @override
   String get lintRule => 'unnecessary_getters_setters';
 
@@ -76,6 +79,20 @@ class C {
 ''');
   }
 
+  test_unnecessary_getterAndSetter_extensionType() async {
+    await assertDiagnostics(r'''
+extension type E(int i) {
+  static int? _x;
+  static int? get x => _x;
+  static set x(int? value) {
+    _x = value;
+  }
+}
+''', [
+      lint(62, 1),
+    ]);
+  }
+
   test_unnecessary_getterAndSetterHaveBlockBody() async {
     await assertDiagnostics(r'''
 class C {