fix unnecessary_brace_in_string_interps for this expressions (#3694)

* fix unnecessary_brace_in_string_interps for this expressions

* shared checking

Author: pq

lib/src/rules/unnecessary_brace_in_string_interps.dart

@@ -62,13 +62,19 @@ class _Visitor extends SimpleAstVisitor<void> {
       var exp = expression.expression;
       if (exp is SimpleIdentifier) {
         var identifier = exp;
-        var bracket = expression.rightBracket;
-        if (bracket != null &&
-            !isIdentifierPart(bracket.next) &&
-            !identifier.name.contains('\$')) {
-          rule.reportLint(expression);
+        if (!identifier.name.contains('\$')) {
+          _check(expression);
         }
+      } else if (exp is ThisExpression) {
+        _check(expression);
       }
     }
   }
+
+  void _check(InterpolationExpression expression) {
+    var bracket = expression.rightBracket;
+    if (bracket != null && !isIdentifierPart(bracket.next)) {
+      rule.reportLint(expression);
+    }
+  }
 }

test/rules/all.dart

@@ -70,6 +70,8 @@ import 'tighten_type_of_initializing_formals_test.dart'
     as tighten_type_of_initializing_formals;
 import 'type_init_formals_test.dart' as type_init_formals;
 import 'unawaited_futures_test.dart' as unawaited_futures;
+import 'unnecessary_brace_in_string_interps_test.dart'
+    as unnecessary_brace_in_string_interps;
 import 'unnecessary_const_test.dart' as unnecessary_const;
 import 'unnecessary_null_checks_test.dart' as unnecessary_null_checks;
 import 'unnecessary_overrides_test.dart' as unnecessary_overrides;
@@ -129,6 +131,7 @@ void main() {
   tighten_type_of_initializing_formals.main();
   type_init_formals.main();
   unawaited_futures.main();
+  unnecessary_brace_in_string_interps.main();
   unnecessary_const.main();
   unnecessary_null_checks.main();
   unnecessary_overrides.main();

test/rules/unnecessary_brace_in_string_interps_test.dart

@@ -0,0 +1,70 @@
+// Copyright (c) 2022, 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(UnnecessaryBraceInStringInterpsTest);
+  });
+}
+
+@reflectiveTest
+class UnnecessaryBraceInStringInterpsTest extends LintRuleTest {
+  @override
+  String get lintRule => 'unnecessary_brace_in_string_interps';
+
+  test_simpleIdentifier() async {
+    await assertDiagnostics(r'''
+void hi(String name) {
+  print('hi: ${name}');
+}
+''', [
+      lint(36, 7),
+    ]);
+  }
+
+  test_simpleIdentifier_suffixed() async {
+    await assertNoDiagnostics(r'''
+void hi(String name) {
+  print('hi: ${name}s');
+}
+''');
+  }
+
+  test_this_methodInvocation() async {
+    await assertNoDiagnostics(r'''
+class A {
+  void hi() {
+    print('hi: ${this.toString()}');
+  }
+}
+''');
+  }
+
+  /// https://github.com/dart-lang/linter/issues/3691
+  test_thisExpression() async {
+    await assertDiagnostics(r'''
+class A {
+  void hi() {
+    print('hi: ${this}');
+  }
+}
+''', [
+      lint(39, 7),
+    ]);
+  }
+
+  test_thisExpression_suffixed() async {
+    await assertNoDiagnostics(r'''
+class A {
+  void hi() {
+    print('${this}s');
+  }
+}
+''');
+  }
+}