pkg/analyzer/test/src/diagnostics/unused_element_test.dart

// Copyright (c) 2019, 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:analyzer/src/dart/error/hint_codes.dart';
import 'package:test/expect.dart';
import 'package:test_reflective_loader/test_reflective_loader.dart';

import '../dart/resolution/context_collection_resolution.dart';

main() {
  defineReflectiveSuite(() {
    defineReflectiveTests(UnusedElementTest);
    defineReflectiveTests(UnusedElementWithoutNullSafetyTest);
  });
}

@reflectiveTest
class UnusedElementTest extends PubPackageResolutionTest {
  test_class_isUsed_isExpression_expression() async {
    await assertNoErrorsInCode('''
class _A {}
void f(Object p) {
  if (_A() is int) {
  }
}
''');
  }

  test_class_notUsed_isExpression_typeArgument() async {
    await assertErrorsInCode(r'''
class _A {}
void f(Object p) {
  if (p is List<_A>) {
  }
}
''', [
      error(HintCode.UNUSED_ELEMENT, 6, 2),
    ]);
  }

  test_class_notUsed_isExpression_typeInFunctionType() async {
    await assertErrorsInCode(r'''
class _A {}
void f(Object p) {
  if (p is void Function(_A)) {
  }
}
''', [
      error(HintCode.UNUSED_ELEMENT, 6, 2),
    ]);
  }

  test_class_notUsed_isExpression_typeInTypeParameter() async {
    await assertErrorsInCode(r'''
class _A {}
void f(Object p) {
  if (p is void Function<T extends _A>()) {
  }
}
''', [
      error(HintCode.UNUSED_ELEMENT, 6, 2),
    ]);
  }

  test_class_notUsed_variableDeclaration() async {
    await assertErrorsInCode('''
class _A {}
void f() {
  _A? v;
  print(v);
}
print(x) {}
''', [
      error(HintCode.UNUSED_ELEMENT, 6, 2),
    ]);
  }

  test_class_notUsed_variableDeclaration_typeArgument() async {
    await assertErrorsInCode('''
class _A {}
main() {
  List<_A>? v;
  print(v);
}
print(x) {}
''', [
      error(HintCode.UNUSED_ELEMENT, 6, 2),
    ]);
  }

  test_optionalParameter_isUsed_genericConstructor() async {
    await assertNoErrorsInCode('''
class C<T> {
  C._([int? x]);
}
void foo() {
  C._(7);
}
''');
  }

  test_optionalParameter_isUsed_genericFunction() async {
    await assertNoErrorsInCode('''
void _f<T>([int? x]) {}
void foo() {
  _f(7);
}
''');
  }

  test_optionalParameter_isUsed_genericMethod() async {
    await assertNoErrorsInCode('''
class C {
  void _m<T>([int? x]) {}
}
void foo() {
  C()._m(7);
}
''');
  }

  test_optionalParameter_isUsed_overrideRequiredNamed() async {
    await assertNoErrorsInCode(r'''
class A {
  void _m({required int a}) {}
}
class B implements A {
  void _m({int a = 0}) {}
}
f() => A()._m(a: 0);
''');
  }

  @FailingTest(issue: 'https://github.com/dart-lang/sdk/issues/47839')
  test_optionalParameter_notUsed_genericConstructor() async {
    // TODO(srawlins): Change to assertErrorsInCode when this is fixed.
    addTestFile('''
class C<T> {
  C._([int? x]);
}
void foo() {
  C._();
}
''');
    await resolveTestFile();
    expect(result.errors, isNotEmpty);
  }

  @FailingTest(issue: 'https://github.com/dart-lang/sdk/issues/47839')
  test_optionalParameter_notUsed_genericFunction() async {
    // TODO(srawlins): Change to assertErrorsInCode when this is fixed.
    addTestFile('''
void _f<T>([int? x]) {}
void foo() {
  _f();
}
''');
    await resolveTestFile();
    expect(result.errors, isNotEmpty);
  }

  @FailingTest(issue: 'https://github.com/dart-lang/sdk/issues/47839')
  test_optionalParameter_notUsed_genericMethod() async {
    // TODO(srawlins): Change to assertErrorsInCode when this is fixed.
    addTestFile('''
class C {
  void _m<T>([int? x]) {}
}
void foo() {
  C()._m();
}
''');
    await resolveTestFile();
    expect(result.errors, isNotEmpty);
  }

  test_parameter_optionalNamed_fieldFormal_isUsed_constructorInvocation() async {
    await assertNoErrorsInCode(r'''
class _A {
  final int? f;
  _A({this.f});
}
f() => _A(f: 0);
''');
  }

  test_parameter_optionalNamed_fieldFormal_isUsed_factoryRedirect() async {
    await assertNoErrorsInCode(r'''
class _A {
  final int? f;
  _A({this.f});
  factory _A.named({int? f}) = _A;
}
f() => _A.named(f: 0);
''');
  }

  test_parameter_optionalNamed_fieldFormal_notUsed() async {
    await assertErrorsInCode(r'''
class _A {
  final int? f;
  _A({this.f});
}
f() => _A();
''', [
      error(HintCode.UNUSED_ELEMENT_PARAMETER, 38, 1),
    ]);
  }

  test_parameter_optionalNamed_fieldFormal_notUsed_factoryRedirect() async {
    await assertErrorsInCode(r'''
class _A {
  final int? f;
  _A({this.f});
  factory _A.named() = _A;
}
f() => _A.named();
''', [
      error(HintCode.UNUSED_ELEMENT_PARAMETER, 38, 1),
    ]);
  }

  test_parameter_optionalPositional_fieldFormal_isUsed_constructorInvocation() async {
    await assertNoErrorsInCode(r'''
class _A {
  final int? f;
  _A([this.f]);
}
f() => _A(0);
''');
  }

  test_parameter_optionalPositional_fieldFormal_isUsed_factoryRedirect() async {
    await assertNoErrorsInCode(r'''
class _A {
  final int? f;
  _A([this.f]);
  factory _A.named([int a]) = _A;
}
f() => _A.named(0);
''');
  }

  test_parameter_optionalPositional_fieldFormal_notUsed() async {
    await assertErrorsInCode(r'''
class _A {
  final int? f;
  _A([this.f]);
}
f() => _A();
''', [
      error(HintCode.UNUSED_ELEMENT_PARAMETER, 38, 1),
    ]);
  }

  test_parameter_optionalPositional_fieldFormal_notUsed_factoryRedirect() async {
    await assertErrorsInCode(r'''
class _A {
  final int? f;
  _A([this.f]);
  factory _A.named() = _A;
}
f() => _A.named();
''', [
      error(HintCode.UNUSED_ELEMENT_PARAMETER, 38, 1),
    ]);
  }

  test_typeAlias_interfaceType_isUsed_typeName_isExpression() async {
    await assertNoErrorsInCode(r'''
typedef _A = List<int>;

void f(a) {
  a is _A;
}
''');
  }

  test_typeAlias_interfaceType_isUsed_typeName_parameter() async {
    await assertNoErrorsInCode(r'''
typedef _A = List<int>;

void f(_A a) {}
''');
  }

  test_typeAlias_interfaceType_isUsed_typeName_typeArgument() async {
    await assertNoErrorsInCode(r'''
typedef _A = List<int>;

void f() {
  Map<_A, int>();
}
''');
  }

  test_typeAlias_interfaceType_notUsed() async {
    await assertErrorsInCode(r'''
typedef _A = List<int>;
''', [
      error(HintCode.UNUSED_ELEMENT, 8, 2),
    ]);
  }
}

@reflectiveTest
class UnusedElementWithoutNullSafetyTest extends PubPackageResolutionTest
    with WithoutNullSafetyMixin {
  test_class_isUsed_extends() async {
    await assertNoErrorsInCode(r'''
class _A {}
class B extends _A {}
''');
  }

  test_class_isUsed_fieldDeclaration() async {
    await assertNoErrorsInCode(r'''
class Foo {
  _Bar x;
}

class _Bar {
}
''');
  }

  test_class_isUsed_implements() async {
    await assertNoErrorsInCode(r'''
class _A {}
class B implements _A {}
''');
  }

  test_class_isUsed_instanceCreation() async {
    await assertNoErrorsInCode(r'''
class _A {}
main() {
  new _A();
}
''');
  }

  test_class_isUsed_staticFieldAccess() async {
    await assertNoErrorsInCode(r'''
class _A {
  static const F = 42;
}
main() {
  _A.F;
}
''');
  }

  test_class_isUsed_staticMethodInvocation() async {
    await assertNoErrorsInCode(r'''
class _A {
  static m() {}
}
main() {
  _A.m();
}
''');
  }

  test_class_isUsed_typeArgument() async {
    await assertNoErrorsInCode(r'''
class _A {}
main() {
  var v = new List<_A>();
  print(v);
}
''');
  }

  test_class_isUsed_with() async {
    await assertNoErrorsInCode(r'''
class _A {}
class B with _A {}
''');
  }

  test_class_notUsed_inClassMember() async {
    await assertErrorsInCode(r'''
class _A {
  static staticMethod() {
    new _A();
  }
  instanceMethod() {
    new _A();
  }
}
''', [
      error(HintCode.UNUSED_ELEMENT, 6, 2),
      error(HintCode.UNUSED_ELEMENT, 20, 12),
    ]);
  }

  test_class_notUsed_inConstructorName() async {
    await assertErrorsInCode(r'''
class _A {
  _A() {}
  _A.named() {}
}
''', [
      error(HintCode.UNUSED_ELEMENT, 6, 2),
      error(HintCode.UNUSED_ELEMENT, 26, 5),
    ]);
  }

  test_class_notUsed_isExpression() async {
    await assertErrorsInCode(r'''
class _A {}
main(p) {
  if (p is _A) {
  }
}
''', [
      error(HintCode.UNUSED_ELEMENT, 6, 2),
    ]);
  }

  test_class_notUsed_noReference() async {
    await assertErrorsInCode(r'''
class _A {}
main() {
}
''', [
      error(HintCode.UNUSED_ELEMENT, 6, 2),
    ]);
  }

  test_class_notUsed_variableDeclaration() async {
    await assertErrorsInCode(r'''
class _A {}
main() {
  _A v;
  print(v);
}
print(x) {}
''', [
      error(HintCode.UNUSED_ELEMENT, 6, 2),
    ]);
  }

  test_classGetterSetter_isUsed_assignmentExpression_compound() async {
    await assertNoErrorsInCode(r'''
class A {
  int get _foo => 0;
  set _foo(int _) {}

  void f() {
    _foo += 2;
  }
}
''');
  }

  test_classSetter_isUsed_assignmentExpression_simple() async {
    await assertNoErrorsInCode(r'''
class A {
  set _foo(int _) {}

  void f() {
    _foo = 0;
  }
}
''');
  }

  test_constructor_isUsed_asRedirectee() async {
    await assertNoErrorsInCode(r'''
class A {
  A._constructor();
  factory A.b() = A._constructor;
}
''');
  }

  test_constructor_isUsed_asRedirectee_viaInitializer() async {
    await assertNoErrorsInCode(r'''
class A {
  A._constructor();
  A() : this._constructor();
}
''');
  }

  test_constructor_isUsed_asRedirectee_viaSuper() async {
    await assertNoErrorsInCode(r'''
class A {
  A._constructor();
}

class B extends A {
  B() : super._constructor();
}
''');
  }

  test_constructor_isUsed_explicit() async {
    await assertNoErrorsInCode(r'''
class A {
  A._constructor();
}
A f() => A._constructor();
''');
  }

  test_constructor_notUsed_multiple() async {
    await assertErrorsInCode(r'''
class A {
  A._constructor();
  A();
}
''', [
      error(HintCode.UNUSED_ELEMENT, 14, 12),
    ]);
  }

  test_constructor_notUsed_single() async {
    await assertNoErrorsInCode(r'''
class A {
  A._constructor();
}
''');
  }

  test_enum_isUsed_fieldReference() async {
    await assertNoErrorsInCode(r'''
enum _MyEnum {A}
main() {
  _MyEnum.A;
}
''');
  }

  test_enum_notUsed_noReference() async {
    await assertErrorsInCode(r'''
enum _MyEnum {A, B}
void f(d) {
  d.A;
  d.B;
}
''', [
      error(HintCode.UNUSED_ELEMENT, 5, 7),
    ]);
  }

  test_factoryConstructor_notUsed_multiple() async {
    await assertErrorsInCode(r'''
class A {
  factory A._factory() => A();
  A();
}
''', [
      error(HintCode.UNUSED_ELEMENT, 22, 8),
    ]);
  }

  test_factoryConstructor_notUsed_single() async {
    await assertNoErrorsInCode(r'''
class A {
  factory A._factory() => throw 0;
}
''');
  }

  test_fieldImplicitGetter_isUsed() async {
    await assertNoErrorsInCode(r'''
class A {
  int _g;
  int get g => this._g;
}
''');
  }

  test_functionLocal_isUsed_closure() async {
    await assertNoErrorsInCode(r'''
main() {
  print(() {});
}
print(x) {}
''');
  }

  test_functionLocal_isUsed_invocation() async {
    await assertNoErrorsInCode(r'''
main() {
  f() {}
  f();
}
''');
  }

  test_functionLocal_isUsed_reference() async {
    await assertNoErrorsInCode(r'''
main() {
  f() {}
  print(f);
}
print(x) {}
''');
  }

  test_functionLocal_notUsed_noReference() async {
    await assertErrorsInCode(r'''
main() {
  f() {}
}
''', [
      error(HintCode.UNUSED_ELEMENT, 11, 1),
    ]);
  }

  test_functionLocal_notUsed_referenceFromItself() async {
    await assertErrorsInCode(r'''
main() {
  _f(int p) {
    _f(p - 1);
  }
}
''', [
      error(HintCode.UNUSED_ELEMENT, 11, 2),
    ]);
  }

  test_functionTypeAlias_isUsed_isExpression() async {
    await assertNoErrorsInCode(r'''
typedef _F(a, b);
main(f) {
  if (f is _F) {
    print('F');
  }
}
''');
  }

  test_functionTypeAlias_isUsed_reference() async {
    await assertNoErrorsInCode(r'''
typedef _F(a, b);
main(_F f) {
}
''');
  }

  test_functionTypeAlias_isUsed_typeArgument() async {
    await assertNoErrorsInCode(r'''
typedef _F(a, b);
main() {
  var v = new List<_F>();
  print(v);
}
''');
  }

  test_functionTypeAlias_isUsed_variableDeclaration() async {
    await assertNoErrorsInCode(r'''
typedef _F(a, b);
class A {
  _F f;
}
''');
  }

  test_functionTypeAlias_notUsed_noReference() async {
    await assertErrorsInCode(r'''
typedef _F(a, b);
main() {
}
''', [
      error(HintCode.UNUSED_ELEMENT, 8, 2),
    ]);
  }

  test_getter_isUsed_invocation_deepSubclass() async {
    await assertNoErrorsInCode(r'''
abstract class A {
  String get _debugName;

  String toString() {
    return _debugName;
  }
}

class B extends A {
  @override
  String get _debugName => "B";
}

class C extends B {
  String get _debugName => "C";
}
''');
  }

  test_getter_isUsed_invocation_implicitThis() async {
    await assertErrorsInCode(r'''
class A {
  get _g => null;
  useGetter() {
    var v = _g;
  }
}
''', [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 52, 1),
    ]);
  }

  test_getter_isUsed_invocation_parameterized() async {
    await assertNoErrorsInCode(r'''
class A<T> {
  List<int> _list = List(1);
  int get _item => _list.first;
  set _item(int item) => _list[0] = item;
}
class B<T> {
  A<T> a;
}
void main() {
  B<int> b = B();
  b.a._item = 3;
  print(b.a._item == 7);
}
''');
  }

  test_getter_isUsed_invocation_parameterized_subclass() async {
    await assertNoErrorsInCode(r'''
abstract class A<T> {
  T get _defaultThing;
  T _thing;

  void main() {
    _thing ??= _defaultThing;
    print(_thing);
  }
}
class B extends A<int> {
  @override
  int get _defaultThing => 7;
}
''');
  }

  test_getter_isUsed_invocation_prefixedIdentifier() async {
    await assertErrorsInCode(r'''
class A {
  get _g => null;
}
main(A a) {
  var v = a._g;
}
''', [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 48, 1),
    ]);
  }

  test_getter_isUsed_invocation_propertyAccess() async {
    await assertErrorsInCode(r'''
class A {
  get _g => null;
}
main() {
  var v = new A()._g;
}
''', [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 45, 1),
    ]);
  }

  test_getter_isUsed_invocation_subclass_plusPlus() async {
    await assertNoErrorsInCode(r'''
class A {
  int __a = 0;
  int get _a => __a;
  void set _a(int val) {
    __a = val;
  }
  int b() => _a++;
}
class B extends A {
  @override
  int get _a => 3;
}
''');
  }

  test_getter_notUsed_invocation_subclass() async {
    await assertErrorsInCode(r'''
class A {
  int __a = 0;
  int get _a => __a;
  void set _a(int val) {
    __a = val;
  }
  int b() => _a = 7;
}
class B extends A {
  @override
  int get _a => 3;
}
''', [
      error(HintCode.UNUSED_ELEMENT, 35, 2),
      error(HintCode.UNUSED_ELEMENT, 155, 2),
    ]);
  }

  test_getter_notUsed_noReference() async {
    await assertErrorsInCode(r'''
class A {
  get _g => null;
}
''', [
      error(HintCode.UNUSED_ELEMENT, 16, 2),
    ]);
  }

  test_getter_notUsed_referenceFromItself() async {
    await assertErrorsInCode(r'''
class A {
  get _g {
    return _g;
  }
}
''', [
      error(HintCode.UNUSED_ELEMENT, 16, 2),
    ]);
  }

  test_method_isUsed_hasPragma_vmEntryPoint() async {
    pragma;
    await assertNoErrorsInCode(r'''
class A {
  @pragma('vm:entry-point')
  void _foo() {}
}
''');
  }

  test_method_isUsed_hasReference_implicitThis() async {
    await assertNoErrorsInCode(r'''
class A {
  _m() {}
  useMethod() {
    print(_m);
  }
}
print(x) {}
''');
  }

  test_method_isUsed_hasReference_implicitThis_subclass() async {
    await assertNoErrorsInCode(r'''
class A {
  _m() {}
  useMethod() {
    print(_m);
  }
}
class B extends A {
  _m() {}
}
print(x) {}
''');
  }

  test_method_isUsed_hasReference_prefixedIdentifier() async {
    await assertNoErrorsInCode(r'''
class A {
  _m() {}
}
main(A a) {
  a._m;
}
''');
  }

  test_method_isUsed_hasReference_propertyAccess() async {
    await assertNoErrorsInCode(r'''
class A {
  _m() {}
}
main() {
  new A()._m;
}
''');
  }

  test_method_isUsed_invocation_fromMixinApplication() async {
    await assertNoErrorsInCode(r'''
mixin A {
  _m() {}
}
class C with A {
  useMethod() {
    _m();
  }
}
''');
  }

  test_method_isUsed_invocation_fromMixinWithConstraint() async {
    await assertNoErrorsInCode(r'''
class A {
  _m() {}
}
mixin M on A {
  useMethod() {
    _m();
  }
}
''');
  }

  test_method_isUsed_invocation_implicitThis() async {
    await assertNoErrorsInCode(r'''
class A {
  _m() {}
  useMethod() {
    _m();
  }
}
''');
  }

  test_method_isUsed_invocation_implicitThis_subclass() async {
    await assertNoErrorsInCode(r'''
class A {
  _m() {}
  useMethod() {
    _m();
  }
}
class B extends A {
  _m() {}
}
''');
  }

  test_method_isUsed_invocation_memberElement() async {
    await assertNoErrorsInCode(r'''
class A<T> {
  _m(T t) {}
}
main(A<int> a) {
  a._m(0);
}
''');
  }

  test_method_isUsed_invocation_propagated() async {
    await assertNoErrorsInCode(r'''
class A {
  _m() {}
}
main() {
  var a = new A();
  a._m();
}
''');
  }

  test_method_isUsed_invocation_static() async {
    await assertNoErrorsInCode(r'''
class A {
  _m() {}
}
main() {
  A a = new A();
  a._m();
}
''');
  }

  test_method_isUsed_invocation_subclass() async {
    await assertNoErrorsInCode(r'''
class A {
  _m() {}
}
class B extends A {
  _m() {}
}
main(A a) {
  a._m();
}
''');
  }

  test_method_isUsed_privateExtension() async {
    await assertNoErrorsInCode(r'''
extension _A on String {
  void m() {}
}
void main() {
  "hello".m();
}
''');
  }

  test_method_isUsed_privateExtension_binaryOperator() async {
    await assertNoErrorsInCode(r'''
extension _A on String {
  int operator -(int other) => other;
}
void main() {
  "hello" - 3;
}
''');
  }

  test_method_isUsed_privateExtension_generic_binaryOperator() async {
    await assertNoErrorsInCode(r'''
class A<T> {}
extension _A<T> on A<T> {
  int operator -(int other) => other;
}
void f(A<int> a) {
  a - 3;
}
''');
  }

  test_method_isUsed_privateExtension_generic_indexEqOperator() async {
    await assertNoErrorsInCode(r'''
class A<T> {}
extension _A<T> on A<T> {
  void operator []=(int index, T value) {
}}
void f(A<int> a) {
  a[0] = 1;
}
''');
  }

  test_method_isUsed_privateExtension_generic_indexOperator() async {
    await assertNoErrorsInCode(r'''
class A<T> {}
extension _A<T> on A<T> {
  A<T> operator [](int index) => throw 0;
}
void f(A<int> a) {
  a[0];
}
''');
  }

  test_method_isUsed_privateExtension_generic_method() async {
    await assertNoErrorsInCode(r'''
class A<T> {}
extension _A<T> on A<T> {
  A<T> foo() => throw 0;
}
void f(A<int> a) {
  a.foo();
}
''');
  }

  test_method_isUsed_privateExtension_generic_postfixOperator() async {
    await assertNoErrorsInCode(r'''
class A<T> {}
extension _A<T> on A<T> {
  A<T> operator -(int i) => throw 0;
}
void f(A<int> a) {
  a--;
}
''');
  }

  test_method_isUsed_privateExtension_generic_prefixOperator() async {
    await assertNoErrorsInCode(r'''
class A<T> {}
extension _A<T> on A<T> {
  T operator ~() => throw 0;
}
void f(A<int> a) {
  ~a;
}
''');
  }

  test_method_isUsed_privateExtension_indexEqOperator() async {
    await assertNoErrorsInCode(r'''
extension _A on bool {
  operator []=(int index, int value) {}
}
void main() {
  false[0] = 1;
}
''');
  }

  test_method_isUsed_privateExtension_indexOperator() async {
    await assertNoErrorsInCode(r'''
extension _A on bool {
  int operator [](int index) => 7;
}
void main() {
  false[3];
}
''');
  }

  test_method_isUsed_privateExtension_methodCall() async {
    await assertNoErrorsInCode(r'''
extension _E on int {
  void call() {}
}

void f() {
  0();
}
''');
  }

  test_method_isUsed_privateExtension_operator_assignment() async {
    await assertNoErrorsInCode(r'''
extension _A on String {
  String operator -(int other) => this;
}
void f(String s) {
  s -= 3;
}
''');
  }

  test_method_isUsed_privateExtension_postfixOperator() async {
    await assertNoErrorsInCode(r'''
extension _A on String {
  String operator -(int i) => this;
}
void f(String a) {
  a--;
}
''');
  }

  test_method_isUsed_privateExtension_prefixOperator() async {
    await assertNoErrorsInCode(r'''
extension _A on String {
  int operator ~() => 7;
}
void main() {
  ~"hello";
}
''');
  }

  test_method_isUsed_public() async {
    await assertNoErrorsInCode(r'''
class A {
  m() {}
}
main() {
}
''');
  }

  test_method_isUsed_staticInvocation() async {
    await assertNoErrorsInCode(r'''
class A {
  static _m() {}
}
main() {
  A._m();
}
''');
  }

  test_method_isUsed_unnamedExtension() async {
    await assertNoErrorsInCode(r'''
extension on String {
  void m() {}
}
void main() {
  "hello".m();
}
''');
  }

  test_method_isUsed_unnamedExtension_methodCall() async {
    await assertNoErrorsInCode(r'''
extension on int {
  void call() {}
}

void f() {
  0();
}
''');
  }

  test_method_isUsed_unnamedExtension_operator() async {
    await assertNoErrorsInCode(r'''
extension on String {
  int operator -(int other) => other;
}
void main() {
  "hello" - 3;
}
''');
  }

  test_method_notUsed_hasSameNameAsUsed() async {
    await assertErrorsInCode(r'''
class A {
  void _m1() {}
}
class B {
  void public() => _m1();
  void _m1() {}
}
''', [
      error(HintCode.UNUSED_ELEMENT, 17, 3),
    ]);
  }

  test_method_notUsed_noReference() async {
    await assertErrorsInCode(r'''
class A {
  static _m() {}
}
''', [
      error(HintCode.UNUSED_ELEMENT, 19, 2),
    ]);
  }

  test_method_notUsed_privateExtension() async {
    await assertErrorsInCode(r'''
extension _A on String {
  void m() {}
}
''', [
      error(HintCode.UNUSED_ELEMENT, 32, 1),
    ]);
  }

  /// Postfix operators can only be called, not defined. The "notUsed" sibling to
  /// this test is the test on a binary operator.
  test_method_notUsed_privateExtension_indexEqOperator() async {
    await assertErrorsInCode(r'''
extension _A on bool {
  operator []=(int index, int value) {}
}
''', [
      error(HintCode.UNUSED_ELEMENT, 34, 3),
    ]);
  }

  test_method_notUsed_privateExtension_indexOperator() async {
    await assertErrorsInCode(r'''
extension _A on bool {
  int operator [](int index) => 7;
}
''', [
      error(HintCode.UNUSED_ELEMENT, 38, 2),
    ]);
  }

  test_method_notUsed_privateExtension_methodCall() async {
    await assertErrorsInCode(r'''
extension _E on int {
  void call() {}
}
''', [
      error(HintCode.UNUSED_ELEMENT, 29, 4),
    ]);
  }

  /// Assignment operators can only be called, not defined. The "notUsed" sibling
  /// to this test is the test on a binary operator.
  test_method_notUsed_privateExtension_operator() async {
    await assertErrorsInCode(r'''
extension _A on String {
  int operator -(int other) => other;
}
''', [
      error(HintCode.UNUSED_ELEMENT, 40, 1),
    ]);
  }

  test_method_notUsed_privateExtension_prefixOperator() async {
    await assertErrorsInCode(r'''
extension _A on String {
  int operator ~() => 7;
}
''', [
      error(HintCode.UNUSED_ELEMENT, 40, 1),
    ]);
  }

  test_method_notUsed_referenceFromItself() async {
    await assertErrorsInCode(r'''
class A {
  static _m(int p) {
    _m(p - 1);
  }
}
''', [
      error(HintCode.UNUSED_ELEMENT, 19, 2),
    ]);
  }

  test_method_notUsed_referenceInComment() async {
    await assertErrorsInCode(r'''
/// [A] has a method, [_f].
class A {
  int _f(int p) => 7;
}
''', [
      error(HintCode.UNUSED_ELEMENT, 44, 2),
    ]);
  }

  test_method_notUsed_referenceInComment_outsideEnclosingClass() async {
    await assertErrorsInCode(r'''
class A {
  int _f(int p) => 7;
}
/// This is similar to [A._f].
int g() => 7;
''', [
      error(HintCode.UNUSED_ELEMENT, 16, 2),
    ]);
  }

  test_method_notUsed_unnamedExtension() async {
    await assertErrorsInCode(r'''
extension on String {
  void m() {}
}
''', [
      error(HintCode.UNUSED_ELEMENT, 29, 1),
    ]);
  }

  test_method_notUsed_unnamedExtension_operator() async {
    await assertErrorsInCode(r'''
extension on String {
  int operator -(int other) => other;
}
''', [
      error(HintCode.UNUSED_ELEMENT, 37, 1),
    ]);
  }

  test_mixin_isUsed_with() async {
    await assertNoErrorsInCode(r'''
mixin _M {}
class C with _M {}
''');
  }

  test_mixin_notUsed() async {
    await assertErrorsInCode(r'''
mixin _M {}
''', [
      error(HintCode.UNUSED_ELEMENT, 6, 2),
    ]);
  }

  test_optionalParameter_isUsed_constructor() async {
    await assertNoErrorsInCode(r'''
class _A {
  _A([int a = 0]);
}
f() => _A(0);
''');
  }

  test_optionalParameter_isUsed_functionTearoff() async {
    await assertNoErrorsInCode(r'''
f() {
  void _m([int a]) {}
  _m;
}
''');
  }

  test_optionalParameter_isUsed_local() async {
    await assertNoErrorsInCode(r'''
f() {
  void _m([int a]) {}
  _m(1);
}
''');
  }

  test_optionalParameter_isUsed_methodTearoff() async {
    await assertNoErrorsInCode(r'''
class A {
  void _m([int a]) {}
}
f() => A()._m;
''');
  }

  test_optionalParameter_isUsed_named() async {
    await assertNoErrorsInCode(r'''
class A {
  void _m({int a = 0}) {}
}
f() => A()._m(a: 0);
''');
  }

  test_optionalParameter_isUsed_overridden() async {
    await assertErrorsInCode(r'''
class A {
  void _m([int a]) {}
}
class B implements A {
  void _m([int a]) {}
}
f() {
  A()._m();
  B()._m(0);
}
''', [
      error(HintCode.UNUSED_ELEMENT_PARAMETER, 25, 1),
    ]);
  }

  test_optionalParameter_isUsed_override() async {
    await assertNoErrorsInCode(r'''
class A {
  void _m([int a]) {}
}
class B implements A {
  void _m([int a]) {}
}
f() => A()._m(0);
''');
  }

  test_optionalParameter_isUsed_override_renamed() async {
    await assertNoErrorsInCode(r'''
class A {
  void _m([int a]) {}
}
class B implements A {
  void _m([int b]) {}
}
f() => A()._m(0);
''');
  }

  test_optionalParameter_isUsed_overrideRequired() async {
    await assertNoErrorsInCode(r'''
class A {
  void _m(int a) {}
}
class B implements A {
  void _m([int a]) {}
}
f() => A()._m(0);
''');
  }

  test_optionalParameter_isUsed_positional() async {
    await assertNoErrorsInCode(r'''
class A {
  void _m([int a]) {}
}
f() => A()._m(0);
''');
  }

  test_optionalParameter_isUsed_publicMethod() async {
    await assertNoErrorsInCode(r'''
class A {
  void m([int a]) {}
}
f() => A().m();
''');
  }

  test_optionalParameter_isUsed_publicMethod_extension() async {
    await assertNoErrorsInCode(r'''
extension E on String {
  void m([int a]) {}
}
f() => "hello".m();
''');
  }

  test_optionalParameter_isUsed_requiredPositional() async {
    await assertNoErrorsInCode(r'''
class A {
  void _m(int a) {}
}
f() => A()._m(0);
''');
  }

  test_optionalParameter_notUsed_constructor_named() async {
    await assertErrorsInCode(r'''
class A {
  A._([int a]);
}
f() => A._();
''', [
      error(HintCode.UNUSED_ELEMENT_PARAMETER, 21, 1),
    ]);
  }

  test_optionalParameter_notUsed_constructor_unnamed() async {
    await assertErrorsInCode(r'''
class _A {
  _A([int a]);
}
f() => _A();
''', [
      error(HintCode.UNUSED_ELEMENT_PARAMETER, 21, 1),
    ]);
  }

  test_optionalParameter_notUsed_extension() async {
    await assertErrorsInCode(r'''
extension E on String {
  void _m([int a]) {}
}
f() => "hello"._m();
''', [
      error(HintCode.UNUSED_ELEMENT_PARAMETER, 39, 1),
    ]);
  }

  test_optionalParameter_notUsed_named() async {
    await assertErrorsInCode(r'''
class A {
  void _m({int a}) {}
}
f() => A()._m();
''', [
      error(HintCode.UNUSED_ELEMENT_PARAMETER, 25, 1),
    ]);
  }

  test_optionalParameter_notUsed_override_added() async {
    await assertErrorsInCode(r'''
class A {
  void _m() {}
}
class B implements A {
  void _m([int a]) {}
}
f() => A()._m();
''', [
      error(HintCode.UNUSED_ELEMENT_PARAMETER, 65, 1),
    ]);
  }

  test_optionalParameter_notUsed_positional() async {
    await assertErrorsInCode(r'''
class A {
  void _m([int a]) {}
}
f() => A()._m();
''', [
      error(HintCode.UNUSED_ELEMENT_PARAMETER, 25, 1),
    ]);
  }

  test_optionalParameter_notUsed_publicMethod_privateExtension() async {
    await assertErrorsInCode(r'''
extension _E on String {
  void m([int a]) {}
}
f() => "hello".m();
''', [
      error(HintCode.UNUSED_ELEMENT_PARAMETER, 39, 1),
    ]);
  }

  test_optionalParameter_notUsed_publicMethod_unnamedExtension() async {
    await assertErrorsInCode(r'''
extension on String {
  void m([int a]) {}
}
f() => "hello".m();
''', [
      error(HintCode.UNUSED_ELEMENT_PARAMETER, 36, 1),
    ]);
  }

  test_optionalParameter_static_notUsed() async {
    await assertErrorsInCode(r'''
class A {
  static void _m([int a]) {}
}
f() => A._m();
''', [
      error(HintCode.UNUSED_ELEMENT_PARAMETER, 32, 1),
    ]);
  }

  test_optionalParameter_staticPublic_notUsed_privateClass() async {
    await assertErrorsInCode(r'''
class _A {
  static void m([int a]) {}
}
f() => _A.m();
''', [
      error(HintCode.UNUSED_ELEMENT_PARAMETER, 32, 1),
    ]);
  }

  test_optionalParameter_topLevel_isUsed() async {
    await assertNoErrorsInCode(r'''
void _m([int a]) {}
f() => _m(1);
''');
  }

  test_optionalParameter_topLevel_notUsed() async {
    await assertErrorsInCode(r'''
void _m([int a]) {}
f() => _m();
''', [
      error(HintCode.UNUSED_ELEMENT_PARAMETER, 13, 1),
    ]);
  }

  test_optionalParameter_topLevelPublic_isUsed() async {
    await assertNoErrorsInCode(r'''
void m([int a]) {}
f() => m();
''');
  }

  test_publicStaticMethod_privateClass_isUsed() async {
    await assertNoErrorsInCode(r'''
class _A {
  static void m() {}
}
void main() {
  _A.m();
}
''');
  }

  test_publicStaticMethod_privateClass_notUsed() async {
    await assertErrorsInCode(r'''
class _A {
  static void m() {}
}
void f(_A a) {}
''', [
      error(HintCode.UNUSED_ELEMENT, 25, 1),
    ]);
  }

  test_publicStaticMethod_privateExtension_isUsed() async {
    await assertNoErrorsInCode(r'''
extension _A on String {
  static void m() {}
}
void main() {
  _A.m();
}
''');
  }

  test_publicStaticMethod_privateExtension_notUsed() async {
    await assertErrorsInCode(r'''
extension _A on String {
  static void m() {}
}
''', [
      error(HintCode.UNUSED_ELEMENT, 39, 1),
    ]);
  }

  test_publicStaticMethod_privateMixin_isUsed() async {
    await assertNoErrorsInCode(r'''
mixin _A {
  static void m() {}
}
void main() {
  _A.m();
}
''');
  }

  test_publicStaticMethod_privateMixin_notUsed() async {
    await assertErrorsInCode(r'''
mixin _A {
  static void m() {}
}
void main() {
  _A;
}
''', [
      error(HintCode.UNUSED_ELEMENT, 25, 1),
    ]);
  }

  test_publicTopLevelFunction_notUsed() async {
    await assertNoErrorsInCode(r'''
int get a => 1;
''');
  }

  test_setter_isUsed_invocation_implicitThis() async {
    await assertNoErrorsInCode(r'''
class A {
  set _s(x) {}
  useSetter() {
    _s = 42;
  }
}
''');
  }

  test_setter_isUsed_invocation_PrefixedIdentifier() async {
    await assertNoErrorsInCode(r'''
class A {
  set _s(x) {}
}
main(A a) {
  a._s = 42;
}
''');
  }

  test_setter_isUsed_invocation_PropertyAccess() async {
    await assertNoErrorsInCode(r'''
class A {
  set _s(x) {}
}
main() {
  new A()._s = 42;
}
''');
  }

  test_setter_notUsed_noReference() async {
    await assertErrorsInCode(r'''
class A {
  set _s(x) {}
}
''', [
      error(HintCode.UNUSED_ELEMENT, 16, 2),
    ]);
  }

  test_setter_notUsed_referenceFromItself() async {
    await assertErrorsInCode(r'''
class A {
  set _s(int x) {
    if (x > 5) {
      _s = x - 1;
    }
  }
}
''', [
      error(HintCode.UNUSED_ELEMENT, 16, 2),
    ]);
  }

  test_topLevelAccessors_isUsed_questionQuestionEqual() async {
    await assertNoErrorsInCode(r'''
int get _c => 1;
void set _c(int x) {}
int f() {
  return _c ??= 7;
}
''');
  }

  test_topLevelFunction_isUsed_hasPragma_vmEntryPoint() async {
    await assertNoErrorsInCode(r'''
@pragma('vm:entry-point')
void _f() {}
''');
  }

  test_topLevelFunction_isUsed_invocation() async {
    await assertNoErrorsInCode(r'''
_f() {}
main() {
  _f();
}
''');
  }

  test_topLevelFunction_isUsed_reference() async {
    await assertNoErrorsInCode(r'''
_f() {}
main() {
  print(_f);
}
print(x) {}
''');
  }

  test_topLevelFunction_notUsed_noReference() async {
    await assertErrorsInCode(r'''
_f() {}
main() {
}
''', [
      error(HintCode.UNUSED_ELEMENT, 0, 2),
    ]);
  }

  test_topLevelFunction_notUsed_referenceFromItself() async {
    await assertErrorsInCode(r'''
_f(int p) {
  _f(p - 1);
}
main() {
}
''', [
      error(HintCode.UNUSED_ELEMENT, 0, 2),
    ]);
  }

  test_topLevelFunction_notUsed_referenceInComment() async {
    await assertErrorsInCode(r'''
/// [_f] is a great function.
_f(int p) => 7;
''', [
      error(HintCode.UNUSED_ELEMENT, 30, 2),
    ]);
  }

  test_topLevelGetterSetter_isUsed_assignmentExpression_compound() async {
    await assertNoErrorsInCode(r'''
int get _foo => 0;
set _foo(int _) {}

void f() {
  _foo += 2;
}
''');
  }

  test_topLevelGetterSetter_isUsed_postfixExpression_increment() async {
    await assertNoErrorsInCode(r'''
int get _foo => 0;
set _foo(int _) {}

void f() {
  _foo++;
}
''');
  }

  test_topLevelGetterSetter_isUsed_prefixExpression_increment() async {
    await assertNoErrorsInCode(r'''
int get _foo => 0;
set _foo(int _) {}

void f() {
  ++_foo;
}
''');
  }

  test_topLevelSetter_isUsed_assignmentExpression_simple() async {
    await assertNoErrorsInCode(r'''
set _foo(int _) {}

void f() {
  _foo = 0;
}
''');
  }

  test_topLevelSetter_notUsed() async {
    await assertErrorsInCode(r'''
set _foo(int _) {}
''', [
      error(HintCode.UNUSED_ELEMENT, 4, 4),
    ]);
  }

  test_topLevelVariable_isUsed() async {
    await assertNoErrorsInCode(r'''
int _a = 1;
main() {
  _a;
}
''');
  }

  test_topLevelVariable_isUsed_plusPlus() async {
    await assertNoErrorsInCode(r'''
int _a = 0;
main() {
  var b = _a++;
  b;
}
''');
  }

  test_topLevelVariable_isUsed_questionQuestionEqual() async {
    await assertNoErrorsInCode(r'''
int _a;
f() {
  _a ??= 1;
}
''');
  }

  test_topLevelVariable_notUsed() async {
    await assertErrorsInCode(r'''
int _a = 1;
main() {
  _a = 2;
}
''', [
      error(HintCode.UNUSED_ELEMENT, 4, 2),
    ]);
  }

  test_topLevelVariable_notUsed_compoundAssign() async {
    await assertErrorsInCode(r'''
int _a = 1;
f() {
  _a += 1;
}
''', [
      error(HintCode.UNUSED_ELEMENT, 4, 2),
    ]);
  }

  test_topLevelVariable_notUsed_referenceInComment() async {
    await assertErrorsInCode(r'''
/// [_a] is a great variable.
int _a = 7;
''', [
      error(HintCode.UNUSED_ELEMENT, 34, 2),
    ]);
  }

  test_typeAlias_functionType_isUsed_isExpression() async {
    await assertNoErrorsInCode(r'''
typedef _F = void Function();
main(f) {
  if (f is _F) {
    print('F');
  }
}
''');
  }

  test_typeAlias_functionType_isUsed_reference() async {
    await assertNoErrorsInCode(r'''
typedef _F = void Function();
main(_F f) {
}
''');
  }

  test_typeAlias_functionType_isUsed_typeArgument() async {
    await assertNoErrorsInCode(r'''
typedef _F = void Function();
main() {
  var v = new List<_F>();
  print(v);
}
''');
  }

  test_typeAlias_functionType_isUsed_variableDeclaration() async {
    await assertNoErrorsInCode(r'''
typedef _F = void Function();
class A {
  _F f;
}
''');
  }

  test_typeAlias_functionType_notUsed_noReference() async {
    await assertErrorsInCode(r'''
typedef _F = void Function();
main() {
}
''', [
      error(HintCode.UNUSED_ELEMENT, 8, 2),
    ]);
  }
}