pkg/analyzer/test/generated/strong_mode_test.dart

// Copyright (c) 2016, 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/dart/ast/ast.dart';
import 'package:analyzer/dart/element/element.dart';
import 'package:analyzer/dart/element/nullability_suffix.dart';
import 'package:analyzer/dart/element/type.dart';
import 'package:analyzer/src/dart/ast/extensions.dart';
import 'package:analyzer/src/dart/element/element.dart';
import 'package:analyzer/src/error/codes.dart';
import 'package:test/test.dart';
import 'package:test_reflective_loader/test_reflective_loader.dart';

import '../src/dart/resolution/context_collection_resolution.dart';
import '../utils.dart';
import 'resolver_test_case.dart';
import 'test_support.dart';

main() {
  defineReflectiveSuite(() {
    defineReflectiveTests(StrongModeLocalInferenceTest);
    defineReflectiveTests(StrongModeStaticTypeAnalyzer2Test);
    defineReflectiveTests(StrongModeTypePropagationTest);
  });
}

/// Strong mode static analyzer local type inference tests
@reflectiveTest
class StrongModeLocalInferenceTest extends PubPackageResolutionTest
    with WithoutNullSafetyMixin {
  // TODO(https://github.com/dart-lang/sdk/issues/44666): Use null safety in
  //  test cases.
  TypeAssertions? _assertions;

  late final Asserter<DartType> _isDynamic;
  late final Asserter<InterfaceType> _isFutureOfDynamic;
  late final Asserter<InterfaceType> _isFutureOfInt;
  late final Asserter<InterfaceType> _isFutureOfNull;
  late final Asserter<InterfaceType> _isFutureOrOfInt;
  late final Asserter<DartType> _isInt;
  late final Asserter<DartType> _isNull;
  late final Asserter<DartType> _isNum;
  late final Asserter<DartType> _isObject;
  late final Asserter<DartType> _isString;

  late final AsserterBuilder2<Asserter<DartType>, Asserter<DartType>, DartType>
      _isFunction2Of;
  late final AsserterBuilder<List<Asserter<DartType>>, InterfaceType>
      _isFutureOf;
  late final AsserterBuilder<List<Asserter<DartType>>, InterfaceType>
      _isFutureOrOf;
  late final AsserterBuilderBuilder<Asserter<DartType>,
      List<Asserter<DartType>>, DartType> _isInstantiationOf;
  late final AsserterBuilder<Asserter<DartType>, InterfaceType> _isListOf;
  late final AsserterBuilder2<Asserter<DartType>, Asserter<DartType>,
      InterfaceType> _isMapOf;
  late final AsserterBuilder<DartType, DartType> _isType;

  late final AsserterBuilder<Element, DartType> _hasElement;

  CompilationUnit get unit => result.unit;

  @override
  Future<void> resolveTestFile() async {
    var result = await super.resolveTestFile();

    var assertions = _assertions;
    if (assertions == null) {
      assertions = _assertions = TypeAssertions(typeProvider);
      _isType = assertions.isType;
      _hasElement = assertions.hasElement;
      _isInstantiationOf = assertions.isInstantiationOf;
      _isInt = assertions.isInt;
      _isNull = assertions.isNull;
      _isNum = assertions.isNum;
      _isObject = assertions.isObject;
      _isString = assertions.isString;
      _isDynamic = assertions.isDynamic;
      _isListOf = assertions.isListOf;
      _isMapOf = assertions.isMapOf;
      _isFunction2Of = assertions.isFunction2Of;
      _isFutureOf = _isInstantiationOf(_hasElement(typeProvider.futureElement));
      _isFutureOrOf =
          _isInstantiationOf(_hasElement(typeProvider.futureOrElement));
      _isFutureOfDynamic = _isFutureOf([_isDynamic]);
      _isFutureOfInt = _isFutureOf([_isInt]);
      _isFutureOfNull = _isFutureOf([_isNull]);
      _isFutureOrOfInt = _isFutureOrOf([_isInt]);
    }

    return result;
  }

  test_async_method_propagation() async {
    String code = r'''
      class A {
        Future f0() => new Future.value(3);
        Future f1() async => new Future.value(3);
        Future f2() async => await new Future.value(3);

        Future<int> f3() => new Future.value(3);
        Future<int> f4() async => new Future.value(3);
        Future<int> f5() async => await new Future.value(3);

        Future g0() { return new Future.value(3); }
        Future g1() async { return new Future.value(3); }
        Future g2() async { return await new Future.value(3); }

        Future<int> g3() { return new Future.value(3); }
        Future<int> g4() async { return new Future.value(3); }
        Future<int> g5() async { return await new Future.value(3); }
      }
   ''';
    await resolveTestCode(code);

    void check(String name, Asserter<InterfaceType> typeTest) {
      MethodDeclaration test = AstFinder.getMethodInClass(unit, "A", name);
      FunctionBody body = test.body;
      Expression returnExp;
      if (body is ExpressionFunctionBody) {
        returnExp = body.expression;
      } else {
        var stmt =
            (body as BlockFunctionBody).block.statements[0] as ReturnStatement;
        returnExp = stmt.expression!;
      }
      DartType type = returnExp.typeOrThrow;
      if (returnExp is AwaitExpression) {
        type = returnExp.expression.typeOrThrow;
      }
      typeTest(type as InterfaceType);
    }

    check("f0", _isFutureOfDynamic);
    check("f1", _isFutureOfDynamic);
    check("f2", _isFutureOfDynamic);

    check("f3", _isFutureOfInt);
    check("f4", _isFutureOfInt);
    check("f5", _isFutureOfInt);

    check("g0", _isFutureOfDynamic);
    check("g1", _isFutureOfDynamic);
    check("g2", _isFutureOfDynamic);

    check("g3", _isFutureOfInt);
    check("g4", _isFutureOfInt);
    check("g5", _isFutureOfInt);
  }

  test_async_propagation() async {
    String code = r'''
      Future f0() => new Future.value(3);
      Future f1() async => new Future.value(3);
      Future f2() async => await new Future.value(3);

      Future<int> f3() => new Future.value(3);
      Future<int> f4() async => new Future.value(3);
      Future<int> f5() async => await new Future.value(3);

      Future g0() { return new Future.value(3); }
      Future g1() async { return new Future.value(3); }
      Future g2() async { return await new Future.value(3); }

      Future<int> g3() { return new Future.value(3); }
      Future<int> g4() async { return new Future.value(3); }
      Future<int> g5() async { return await new Future.value(3); }
   ''';
    await resolveTestCode(code);

    void check(String name, Asserter<InterfaceType> typeTest) {
      FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, name);
      var body = test.functionExpression.body;
      Expression returnExp;
      if (body is ExpressionFunctionBody) {
        returnExp = body.expression;
      } else {
        var stmt =
            (body as BlockFunctionBody).block.statements[0] as ReturnStatement;
        returnExp = stmt.expression!;
      }
      DartType type = returnExp.typeOrThrow;
      if (returnExp is AwaitExpression) {
        type = returnExp.expression.typeOrThrow;
      }
      typeTest(type as InterfaceType);
    }

    check("f0", _isFutureOfDynamic);
    check("f1", _isFutureOfDynamic);
    check("f2", _isFutureOfDynamic);

    check("f3", _isFutureOfInt);
    check("f4", _isFutureOfInt);
    check("f5", _isFutureOfInt);

    check("g0", _isFutureOfDynamic);
    check("g1", _isFutureOfDynamic);
    check("g2", _isFutureOfDynamic);

    check("g3", _isFutureOfInt);
    check("g4", _isFutureOfInt);
    check("g5", _isFutureOfInt);
  }

  test_cascadeExpression() async {
    String code = r'''
      class A<T> {
        List<T> map(T a, List<T> mapper(T x)) => mapper(a);
      }

      void main () {
        A<int> a = new A()..map(0, (x) => [x]);
     }
   ''';
    await resolveTestCode(code);
    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    CascadeExpression fetch(int i) {
      var stmt = statements[i] as VariableDeclarationStatement;
      VariableDeclaration decl = stmt.variables.variables[0];
      var exp = decl.initializer as CascadeExpression;
      return exp;
    }

    Element elementA = AstFinder.getClass(unit, "A").declaredElement!;

    CascadeExpression cascade = fetch(0);
    _isInstantiationOf(_hasElement(elementA))([_isInt])(cascade.typeOrThrow);
    var invoke = cascade.cascadeSections[0] as MethodInvocation;
    var function = invoke.argumentList.arguments[1] as FunctionExpression;
    ExecutableElement f0 = function.declaredElement!;
    _isListOf(_isInt)(f0.type.returnType as InterfaceType);
    expect(f0.type.normalParameterTypes[0], typeProvider.intType);
  }

  test_constrainedByBounds1() async {
    // Test that upwards inference with two type variables correctly
    // propogates from the constrained variable to the unconstrained
    // variable if they are ordered left to right.
    String code = r'''
    T f<S, T extends S>(S x) => null;
    void test() { var x = f(3); }
   ''';
    await assertErrorsInCode(code, [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 60, 1),
    ]);

    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "test");
    var stmt = statements[0] as VariableDeclarationStatement;
    VariableDeclaration decl = stmt.variables.variables[0];
    Expression call = decl.initializer!;
    _isInt(call.typeOrThrow);
  }

  test_constrainedByBounds2() async {
    // Test that upwards inference with two type variables does
    // propogate from the constrained variable to the unconstrained
    // variable if they are ordered right to left.
    String code = r'''
    T f<T extends S, S>(S x) => null;
    void test() { var x = f(3); }
   ''';
    await assertErrorsInCode(code, [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 60, 1),
    ]);

    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "test");
    var stmt = statements[0] as VariableDeclarationStatement;
    VariableDeclaration decl = stmt.variables.variables[0];
    Expression call = decl.initializer!;
    _isInt(call.typeOrThrow);
  }

  test_constrainedByBounds3() async {
    var code = r'''
      T f<T extends S, S extends int>(S x) => null;
      void test() { var x = f(3); }
   ''';
    await assertErrorsInCode(code, [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 76, 1),
    ]);

    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "test");
    var stmt = statements[0] as VariableDeclarationStatement;
    VariableDeclaration decl = stmt.variables.variables[0];
    Expression call = decl.initializer!;
    _isInt(call.typeOrThrow);
  }

  test_constrainedByBounds4() async {
    // Test that upwards inference with two type variables correctly
    // propogates from the constrained variable to the unconstrained
    // variable if they are ordered left to right, when the variable
    // appears co and contra variantly
    String code = r'''
    typedef To Func1<From, To>(From x);
    T f<S, T extends Func1<S, S>>(S x) => null;
    void test() { var x = f(3)(4); }
   ''';
    await assertErrorsInCode(code, [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 110, 1),
    ]);

    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "test");
    var stmt = statements[0] as VariableDeclarationStatement;
    VariableDeclaration decl = stmt.variables.variables[0];
    Expression call = decl.initializer!;
    _isInt(call.typeOrThrow);
  }

  test_constrainedByBounds5() async {
    // Test that upwards inference with two type variables does not
    // propagate from the constrained variable to the unconstrained
    // variable if they are ordered right to left, when the variable
    // appears co- and contra-variantly, and that an error is issued
    // for the non-matching bound.
    String code = r'''
    typedef To Func1<From, To>(From x);
    T f<T extends Func1<S, S>, S>(S x) => null;
    void test() { var x = f(3)(null); }
   ''';
    await assertErrorsInCode(code, [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 110, 1),
      error(CompileTimeErrorCode.COULD_NOT_INFER, 114, 1),
    ]);

    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "test");
    var stmt = statements[0] as VariableDeclarationStatement;
    VariableDeclaration decl = stmt.variables.variables[0];
    Expression call = decl.initializer!;
    _isDynamic(call.typeOrThrow);
  }

  test_constructorInitializer_propagation() async {
    String code = r'''
      class A {
        List<String> x;
        A() : this.x = [];
      }
   ''';
    await assertNoErrorsInCode(code);
    ConstructorDeclaration constructor =
        AstFinder.getConstructorInClass(unit, "A", null);
    var assignment = constructor.initializers[0] as ConstructorFieldInitializer;
    Expression exp = assignment.expression;
    _isListOf(_isString)(exp.staticType as InterfaceType);
  }

  test_factoryConstructor_propagation() async {
    String code = r'''
      class A<T> {
        factory A() { return new B(); }
      }
      class B<S> extends A<S> {}
   ''';
    await assertErrorsInCode(code, [
      error(
          CompileTimeErrorCode.NO_GENERATIVE_CONSTRUCTORS_IN_SUPERCLASS, 92, 4),
    ]);

    ConstructorDeclaration constructor =
        AstFinder.getConstructorInClass(unit, "A", null);
    var body = constructor.body as BlockFunctionBody;
    var stmt = body.block.statements[0] as ReturnStatement;
    var exp = stmt.expression as InstanceCreationExpression;
    ClassElement elementB = AstFinder.getClass(unit, "B").declaredElement!;
    ClassElement elementA = AstFinder.getClass(unit, "A").declaredElement!;
    expect(exp.constructorName.type.typeOrThrow.element, elementB);
    _isInstantiationOf(_hasElement(elementB))([
      _isType(elementA.typeParameters[0]
          .instantiate(nullabilitySuffix: NullabilitySuffix.star))
    ])(exp.typeOrThrow);
  }

  test_fieldDeclaration_propagation() async {
    String code = r'''
      class A {
        List<String> f0 = ["hello"];
      }
   ''';
    await assertNoErrorsInCode(code);

    VariableDeclaration field = AstFinder.getFieldInClass(unit, "A", "f0");

    _isListOf(_isString)(field.initializer!.staticType as InterfaceType);
  }

  test_functionDeclaration_body_propagation() async {
    String code = r'''
      typedef T Function2<S, T>(S x);

      List<int> test1() => [];

      Function2<int, int> test2 (int x) {
        Function2<String, int> inner() {
          return (x) => x.length;
        }
        return (x) => x;
     }
   ''';
    await assertErrorsInCode(code, [
      error(HintCode.UNUSED_ELEMENT, 144, 5),
    ]);

    Asserter<InterfaceType> assertListOfInt = _isListOf(_isInt);

    FunctionDeclaration test1 = AstFinder.getTopLevelFunction(unit, "test1");
    var body = test1.functionExpression.body as ExpressionFunctionBody;
    assertListOfInt(body.expression.staticType as InterfaceType);

    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "test2");

    FunctionDeclaration inner =
        (statements[0] as FunctionDeclarationStatement).functionDeclaration;
    var body0 = inner.functionExpression.body as BlockFunctionBody;
    var return0 = body0.block.statements[0] as ReturnStatement;
    Expression anon0 = return0.expression!;
    var type0 = anon0.staticType as FunctionType;
    expect(type0.returnType, typeProvider.intType);
    expect(type0.normalParameterTypes[0], typeProvider.stringType);

    var anon1 =
        (statements[1] as ReturnStatement).expression as FunctionExpression;
    FunctionType type1 = anon1.declaredElement!.type;
    expect(type1.returnType, typeProvider.intType);
    expect(type1.normalParameterTypes[0], typeProvider.intType);
  }

  test_functionLiteral_assignment_typedArguments() async {
    String code = r'''
      typedef T Function2<S, T>(S x);

      void main () {
        Function2<int, String> l0 = (int x) => null;
        Function2<int, String> l1 = (int x) => "hello";
        Function2<int, String> l2 = (String x) => "hello";
        Function2<int, String> l3 = (int x) => 3;
        Function2<int, String> l4 = (int x) {return 3;};
     }
   ''';
    await assertErrorsInCode(code, [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 91, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 144, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 200, 2),
      error(CompileTimeErrorCode.INVALID_ASSIGNMENT, 205, 21),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 259, 2),
      error(CompileTimeErrorCode.RETURN_OF_INVALID_TYPE_FROM_CLOSURE, 275, 1),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 309, 2),
      error(CompileTimeErrorCode.RETURN_OF_INVALID_TYPE_FROM_CLOSURE, 330, 1),
    ]);

    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    DartType literal(int i) {
      var stmt = statements[i] as VariableDeclarationStatement;
      VariableDeclaration decl = stmt.variables.variables[0];
      var exp = decl.initializer as FunctionExpression;
      return exp.declaredElement!.type;
    }

    _isFunction2Of(_isInt, _isNull)(literal(0));
    _isFunction2Of(_isInt, _isString)(literal(1));
    _isFunction2Of(_isString, _isString)(literal(2));
    _isFunction2Of(_isInt, _isString)(literal(3));
    _isFunction2Of(_isInt, _isString)(literal(4));
  }

  test_functionLiteral_assignment_unTypedArguments() async {
    String code = r'''
      typedef T Function2<S, T>(S x);

      void main () {
        Function2<int, String> l0 = (x) => null;
        Function2<int, String> l1 = (x) => "hello";
        Function2<int, String> l2 = (x) => "hello";
        Function2<int, String> l3 = (x) => 3;
        Function2<int, String> l4 = (x) {return 3;};
     }
   ''';
    await assertErrorsInCode(code, [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 91, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 140, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 192, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 244, 2),
      error(CompileTimeErrorCode.RETURN_OF_INVALID_TYPE_FROM_CLOSURE, 256, 1),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 290, 2),
      error(CompileTimeErrorCode.RETURN_OF_INVALID_TYPE_FROM_CLOSURE, 307, 1),
    ]);

    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    DartType literal(int i) {
      var stmt = statements[i] as VariableDeclarationStatement;
      VariableDeclaration decl = stmt.variables.variables[0];
      var exp = decl.initializer as FunctionExpression;
      return exp.declaredElement!.type;
    }

    _isFunction2Of(_isInt, _isNull)(literal(0));
    _isFunction2Of(_isInt, _isString)(literal(1));
    _isFunction2Of(_isInt, _isString)(literal(2));
    _isFunction2Of(_isInt, _isString)(literal(3));
    _isFunction2Of(_isInt, _isString)(literal(4));
  }

  test_functionLiteral_body_propagation() async {
    String code = r'''
      typedef T Function2<S, T>(S x);

      void main () {
        Function2<int, List<String>> l0 = (int x) => ["hello"];
        Function2<int, List<String>> l1 = (String x) => ["hello"];
        Function2<int, List<String>> l2 = (int x) => [3];
        Function2<int, List<String>> l3 = (int x) {return [3];};
     }
   ''';
    await assertErrorsInCode(code, [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 97, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 161, 2),
      error(CompileTimeErrorCode.INVALID_ASSIGNMENT, 166, 23),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 228, 2),
      error(CompileTimeErrorCode.LIST_ELEMENT_TYPE_NOT_ASSIGNABLE, 245, 1),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 286, 2),
      error(CompileTimeErrorCode.LIST_ELEMENT_TYPE_NOT_ASSIGNABLE, 308, 1),
    ]);

    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    Expression functionReturnValue(int i) {
      var stmt = statements[i] as VariableDeclarationStatement;
      VariableDeclaration decl = stmt.variables.variables[0];
      var exp = decl.initializer as FunctionExpression;
      FunctionBody body = exp.body;
      if (body is ExpressionFunctionBody) {
        return body.expression;
      } else {
        Statement stmt = (body as BlockFunctionBody).block.statements[0];
        return (stmt as ReturnStatement).expression!;
      }
    }

    Asserter<InterfaceType> assertListOfString = _isListOf(_isString);
    assertListOfString(functionReturnValue(0).staticType as InterfaceType);
    assertListOfString(functionReturnValue(1).staticType as InterfaceType);
    assertListOfString(functionReturnValue(2).staticType as InterfaceType);
    assertListOfString(functionReturnValue(3).staticType as InterfaceType);
  }

  test_functionLiteral_functionExpressionInvocation_typedArguments() async {
    String code = r'''
      class Mapper<F, T> {
        T map(T mapper(F x)) => mapper(null);
      }

      void main () {
        (new Mapper<int, String>().map)((int x) => null);
        (new Mapper<int, String>().map)((int x) => "hello");
        (new Mapper<int, String>().map)((String x) => "hello");
        (new Mapper<int, String>().map)((int x) => 3);
        (new Mapper<int, String>().map)((int x) {return 3;});
     }
   ''';
    await assertErrorsInCode(code, [
      error(CompileTimeErrorCode.ARGUMENT_TYPE_NOT_ASSIGNABLE, 262, 21),
      error(CompileTimeErrorCode.RETURN_OF_INVALID_TYPE_FROM_CLOSURE, 337, 1),
      error(CompileTimeErrorCode.RETURN_OF_INVALID_TYPE_FROM_CLOSURE, 397, 1),
    ]);

    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    DartType literal(int i) {
      var stmt = statements[i] as ExpressionStatement;
      var invk = stmt.expression as FunctionExpressionInvocation;
      var exp = invk.argumentList.arguments[0] as FunctionExpression;
      return exp.declaredElement!.type;
    }

    _isFunction2Of(_isInt, _isNull)(literal(0));
    _isFunction2Of(_isInt, _isString)(literal(1));
    _isFunction2Of(_isString, _isString)(literal(2));
    _isFunction2Of(_isInt, _isString)(literal(3));
    _isFunction2Of(_isInt, _isString)(literal(4));
  }

  test_functionLiteral_functionExpressionInvocation_unTypedArguments() async {
    String code = r'''
      class Mapper<F, T> {
        T map(T mapper(F x)) => mapper(null);
      }

      void main () {
        (new Mapper<int, String>().map)((x) => null);
        (new Mapper<int, String>().map)((x) => "hello");
        (new Mapper<int, String>().map)((x) => "hello");
        (new Mapper<int, String>().map)((x) => 3);
        (new Mapper<int, String>().map)((x) {return 3;});
     }
   ''';
    await assertErrorsInCode(code, [
      error(CompileTimeErrorCode.RETURN_OF_INVALID_TYPE_FROM_CLOSURE, 318, 1),
      error(CompileTimeErrorCode.RETURN_OF_INVALID_TYPE_FROM_CLOSURE, 374, 1),
    ]);

    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    DartType literal(int i) {
      var stmt = statements[i] as ExpressionStatement;
      var invk = stmt.expression as FunctionExpressionInvocation;
      var exp = invk.argumentList.arguments[0] as FunctionExpression;
      return exp.declaredElement!.type;
    }

    _isFunction2Of(_isInt, _isNull)(literal(0));
    _isFunction2Of(_isInt, _isString)(literal(1));
    _isFunction2Of(_isInt, _isString)(literal(2));
    _isFunction2Of(_isInt, _isString)(literal(3));
    _isFunction2Of(_isInt, _isString)(literal(4));
  }

  test_functionLiteral_functionInvocation_typedArguments() async {
    String code = r'''
      String map(String mapper(int x)) => mapper(null);

      void main () {
        map((int x) => null);
        map((int x) => "hello");
        map((String x) => "hello");
        map((int x) => 3);
        map((int x) {return 3;});
     }
   ''';
    await assertErrorsInCode(code, [
      error(CompileTimeErrorCode.ARGUMENT_TYPE_NOT_ASSIGNABLE, 153, 21),
      error(CompileTimeErrorCode.RETURN_OF_INVALID_TYPE_FROM_CLOSURE, 200, 1),
      error(CompileTimeErrorCode.RETURN_OF_INVALID_TYPE_FROM_CLOSURE, 232, 1),
    ]);

    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    DartType literal(int i) {
      var stmt = statements[i] as ExpressionStatement;
      var invk = stmt.expression as MethodInvocation;
      var exp = invk.argumentList.arguments[0] as FunctionExpression;
      return exp.declaredElement!.type;
    }

    _isFunction2Of(_isInt, _isNull)(literal(0));
    _isFunction2Of(_isInt, _isString)(literal(1));
    _isFunction2Of(_isString, _isString)(literal(2));
    _isFunction2Of(_isInt, _isString)(literal(3));
    _isFunction2Of(_isInt, _isString)(literal(4));
  }

  test_functionLiteral_functionInvocation_unTypedArguments() async {
    String code = r'''
      String map(String mapper(int x)) => mapper(null);

      void main () {
        map((x) => null);
        map((x) => "hello");
        map((x) => "hello");
        map((x) => 3);
        map((x) {return 3;});
     }
   ''';
    await assertErrorsInCode(code, [
      error(CompileTimeErrorCode.RETURN_OF_INVALID_TYPE_FROM_CLOSURE, 181, 1),
      error(CompileTimeErrorCode.RETURN_OF_INVALID_TYPE_FROM_CLOSURE, 209, 1),
    ]);

    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    DartType literal(int i) {
      var stmt = statements[i] as ExpressionStatement;
      var invk = stmt.expression as MethodInvocation;
      var exp = invk.argumentList.arguments[0] as FunctionExpression;
      return exp.declaredElement!.type;
    }

    _isFunction2Of(_isInt, _isNull)(literal(0));
    _isFunction2Of(_isInt, _isString)(literal(1));
    _isFunction2Of(_isInt, _isString)(literal(2));
    _isFunction2Of(_isInt, _isString)(literal(3));
    _isFunction2Of(_isInt, _isString)(literal(4));
  }

  test_functionLiteral_methodInvocation_typedArguments() async {
    String code = r'''
      class Mapper<F, T> {
        T map(T mapper(F x)) => mapper(null);
      }

      void main () {
        new Mapper<int, String>().map((int x) => null);
        new Mapper<int, String>().map((int x) => "hello");
        new Mapper<int, String>().map((String x) => "hello");
        new Mapper<int, String>().map((int x) => 3);
        new Mapper<int, String>().map((int x) {return 3;});
     }
   ''';
    await assertErrorsInCode(code, [
      error(CompileTimeErrorCode.ARGUMENT_TYPE_NOT_ASSIGNABLE, 256, 21),
      error(CompileTimeErrorCode.RETURN_OF_INVALID_TYPE_FROM_CLOSURE, 329, 1),
      error(CompileTimeErrorCode.RETURN_OF_INVALID_TYPE_FROM_CLOSURE, 387, 1),
    ]);

    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    DartType literal(int i) {
      var stmt = statements[i] as ExpressionStatement;
      var invk = stmt.expression as MethodInvocation;
      var exp = invk.argumentList.arguments[0] as FunctionExpression;
      return exp.declaredElement!.type;
    }

    _isFunction2Of(_isInt, _isNull)(literal(0));
    _isFunction2Of(_isInt, _isString)(literal(1));
    _isFunction2Of(_isString, _isString)(literal(2));
    _isFunction2Of(_isInt, _isString)(literal(3));
    _isFunction2Of(_isInt, _isString)(literal(4));
  }

  test_functionLiteral_methodInvocation_unTypedArguments() async {
    String code = r'''
      class Mapper<F, T> {
        T map(T mapper(F x)) => mapper(null);
      }

      void main () {
        new Mapper<int, String>().map((x) => null);
        new Mapper<int, String>().map((x) => "hello");
        new Mapper<int, String>().map((x) => "hello");
        new Mapper<int, String>().map((x) => 3);
        new Mapper<int, String>().map((x) {return 3;});
     }
   ''';
    await assertErrorsInCode(code, [
      error(CompileTimeErrorCode.RETURN_OF_INVALID_TYPE_FROM_CLOSURE, 310, 1),
      error(CompileTimeErrorCode.RETURN_OF_INVALID_TYPE_FROM_CLOSURE, 364, 1),
    ]);

    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    DartType literal(int i) {
      var stmt = statements[i] as ExpressionStatement;
      var invk = stmt.expression as MethodInvocation;
      var exp = invk.argumentList.arguments[0] as FunctionExpression;
      return exp.declaredElement!.type;
    }

    _isFunction2Of(_isInt, _isNull)(literal(0));
    _isFunction2Of(_isInt, _isString)(literal(1));
    _isFunction2Of(_isInt, _isString)(literal(2));
    _isFunction2Of(_isInt, _isString)(literal(3));
    _isFunction2Of(_isInt, _isString)(literal(4));
  }

  test_functionLiteral_unTypedArgument_propagation() async {
    String code = r'''
      typedef T Function2<S, T>(S x);

      void main () {
        Function2<int, int> l0 = (x) => x;
        Function2<int, int> l1 = (x) => x+1;
        Function2<int, String> l2 = (x) => x;
        Function2<int, String> l3 = (x) => x.toLowerCase();
        Function2<String, String> l4 = (x) => x.toLowerCase();
     }
   ''';
    await assertErrorsInCode(code, [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 88, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 131, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 179, 2),
      error(CompileTimeErrorCode.RETURN_OF_INVALID_TYPE_FROM_CLOSURE, 191, 1),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 225, 2),
      error(CompileTimeErrorCode.UNDEFINED_METHOD, 239, 11),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 288, 2),
    ]);

    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    Expression functionReturnValue(int i) {
      var stmt = statements[i] as VariableDeclarationStatement;
      VariableDeclaration decl = stmt.variables.variables[0];
      var exp = decl.initializer as FunctionExpression;
      FunctionBody body = exp.body;
      if (body is ExpressionFunctionBody) {
        return body.expression;
      } else {
        Statement stmt = (body as BlockFunctionBody).block.statements[0];
        return (stmt as ReturnStatement).expression!;
      }
    }

    expect(functionReturnValue(0).staticType, typeProvider.intType);
    expect(functionReturnValue(1).staticType, typeProvider.intType);
    expect(functionReturnValue(2).staticType, typeProvider.intType);
    expect(functionReturnValue(3).staticType, typeProvider.dynamicType);
    expect(functionReturnValue(4).staticType, typeProvider.stringType);
  }

  test_futureOr_assignFromFuture() async {
    // Test a Future<T> can be assigned to FutureOr<T>.
    MethodInvocation invoke = await _testFutureOr(r'''
    FutureOr<T> mk<T>(Future<T> x) => x;
    test() => mk(new Future<int>.value(42));
    ''');
    _isFutureOrOfInt(invoke.staticType as InterfaceType);
  }

  test_futureOr_assignFromValue() async {
    // Test a T can be assigned to FutureOr<T>.
    MethodInvocation invoke = await _testFutureOr(r'''
    FutureOr<T> mk<T>(T x) => x;
    test() => mk(42);
    ''');
    _isFutureOrOfInt(invoke.staticType as InterfaceType);
  }

  test_futureOr_asyncExpressionBody() async {
    // A FutureOr<T> can be used as the expression body for an async function
    MethodInvocation invoke = await _testFutureOr(r'''
    Future<T> mk<T>(FutureOr<T> x) async => x;
    test() => mk(42);
    ''');
    _isFutureOfInt(invoke.staticType as InterfaceType);
  }

  test_futureOr_asyncReturn() async {
    // A FutureOr<T> can be used as the return value for an async function
    MethodInvocation invoke = await _testFutureOr(r'''
    Future<T> mk<T>(FutureOr<T> x) async { return x; }
    test() => mk(42);
    ''');
    _isFutureOfInt(invoke.staticType as InterfaceType);
  }

  test_futureOr_await() async {
    // Test a FutureOr<T> can be awaited.
    MethodInvocation invoke = await _testFutureOr(r'''
    Future<T> mk<T>(FutureOr<T> x) async => await x;
    test() => mk(42);
    ''');
    _isFutureOfInt(invoke.staticType as InterfaceType);
  }

  test_futureOr_downwards1() async {
    // Test that downwards inference interacts correctly with FutureOr
    // parameters.
    MethodInvocation invoke = await _testFutureOr(r'''
    Future<T> mk<T>(FutureOr<T> x) => null;
    Future<int> test() => mk(new Future<int>.value(42));
    ''');
    _isFutureOfInt(invoke.staticType as InterfaceType);
  }

  test_futureOr_downwards2() async {
    // Test that downwards inference interacts correctly with FutureOr
    // parameters when the downwards context is FutureOr
    MethodInvocation invoke = await _testFutureOr(r'''
    Future<T> mk<T>(FutureOr<T> x) => null;
    FutureOr<int> test() => mk(new Future<int>.value(42));
    ''');
    _isFutureOfInt(invoke.staticType as InterfaceType);
  }

  test_futureOr_downwards3() async {
    // Test that downwards inference correctly propogates into
    // arguments.
    MethodInvocation invoke = await _testFutureOr(r'''
    Future<T> mk<T>(FutureOr<T> x) => null;
    Future<int> test() => mk(new Future.value(42));
    ''');
    _isFutureOfInt(invoke.staticType as InterfaceType);
    _isFutureOfInt(
        invoke.argumentList.arguments[0].staticType as InterfaceType);
  }

  test_futureOr_downwards4() async {
    // Test that downwards inference interacts correctly with FutureOr
    // parameters when the downwards context is FutureOr
    MethodInvocation invoke = await _testFutureOr(r'''
    Future<T> mk<T>(FutureOr<T> x) => null;
    FutureOr<int> test() => mk(new Future.value(42));
    ''');
    _isFutureOfInt(invoke.staticType as InterfaceType);
    _isFutureOfInt(
        invoke.argumentList.arguments[0].staticType as InterfaceType);
  }

  test_futureOr_downwards5() async {
    // Test that downwards inference correctly pins the type when it
    // comes from a FutureOr
    MethodInvocation invoke = await _testFutureOr(r'''
    Future<T> mk<T>(FutureOr<T> x) => null;
    FutureOr<num> test() => mk(new Future.value(42));
    ''');
    _isFutureOf([_isNum])(invoke.staticType as InterfaceType);
    _isFutureOf([_isNum])(
        invoke.argumentList.arguments[0].staticType as InterfaceType);
  }

  test_futureOr_downwards6() async {
    // Test that downwards inference doesn't decompose FutureOr
    // when instantiating type variables.
    MethodInvocation invoke = await _testFutureOr(r'''
    T mk<T>(T x) => null;
    FutureOr<int> test() => mk(new Future.value(42));
    ''');
    _isFutureOrOfInt(invoke.staticType as InterfaceType);
    _isFutureOfInt(
        invoke.argumentList.arguments[0].staticType as InterfaceType);
  }

  test_futureOr_downwards7() async {
    // Test that downwards inference incorporates bounds correctly
    // when instantiating type variables.
    MethodInvocation invoke = await _testFutureOr(r'''
      T mk<T extends Future<int>>(T x) => null;
      FutureOr<int> test() => mk(new Future.value(42));
    ''');
    _isFutureOfInt(invoke.staticType as InterfaceType);
    _isFutureOfInt(
        invoke.argumentList.arguments[0].staticType as InterfaceType);
  }

  test_futureOr_downwards8() async {
    // Test that downwards inference incorporates bounds correctly
    // when instantiating type variables.
    // TODO(leafp): I think this should pass once the inference changes
    // that jmesserly is adding are landed.
    MethodInvocation invoke = await _testFutureOr(r'''
    T mk<T extends Future<Object>>(T x) => null;
    FutureOr<int> test() => mk(new Future.value(42));
    ''');
    _isFutureOfInt(invoke.staticType as InterfaceType);
    _isFutureOfInt(
        invoke.argumentList.arguments[0].staticType as InterfaceType);
  }

  test_futureOr_downwards9() async {
    // Test that downwards inference decomposes correctly with
    // other composite types
    MethodInvocation invoke = await _testFutureOr(r'''
    List<T> mk<T>(T x) => null;
    FutureOr<List<int>> test() => mk(3);
    ''');
    _isListOf(_isInt)(invoke.staticType as InterfaceType);
    _isInt(invoke.argumentList.arguments[0].typeOrThrow);
  }

  test_futureOr_methods1() async {
    // Test that FutureOr has the Object methods
    MethodInvocation invoke = await _testFutureOr(r'''
    dynamic test(FutureOr<int> x) => x.toString();
    ''');
    _isString(invoke.typeOrThrow);
  }

  test_futureOr_methods2() async {
    // Test that FutureOr does not have the constituent type methods
    MethodInvocation invoke = await _testFutureOr(r'''
    dynamic test(FutureOr<int> x) => x.abs();
    ''', expectedErrors: [
      error(CompileTimeErrorCode.UNDEFINED_METHOD, 61, 3),
    ]);
    _isDynamic(invoke.typeOrThrow);
  }

  test_futureOr_methods3() async {
    // Test that FutureOr does not have the Future type methods
    MethodInvocation invoke = await _testFutureOr(r'''
    dynamic test(FutureOr<int> x) => x.then((x) => x);
    ''', expectedErrors: [
      error(CompileTimeErrorCode.UNDEFINED_METHOD, 61, 4),
    ]);
    _isDynamic(invoke.typeOrThrow);
  }

  test_futureOr_methods4() async {
    // Test that FutureOr<dynamic> does not have all methods
    MethodInvocation invoke = await _testFutureOr(r'''
    dynamic test(FutureOr<dynamic> x) => x.abs();
    ''', expectedErrors: [
      error(CompileTimeErrorCode.UNDEFINED_METHOD, 65, 3),
    ]);
    _isDynamic(invoke.typeOrThrow);
  }

  test_futureOr_no_return() async {
    MethodInvocation invoke = await _testFutureOr(r'''
    FutureOr<T> mk<T>(Future<T> x) => x;
    Future<int> f;
    test() => f.then((int x) {});
    ''');
    _isFunction2Of(_isInt, _isNull)(
        invoke.argumentList.arguments[0].typeOrThrow);
    _isFutureOfNull(invoke.staticType as InterfaceType);
  }

  test_futureOr_no_return_value() async {
    MethodInvocation invoke = await _testFutureOr(r'''
    FutureOr<T> mk<T>(Future<T> x) => x;
    Future<int> f;
    test() => f.then((int x) {return;});
    ''');
    _isFunction2Of(_isInt, _isNull)(
        invoke.argumentList.arguments[0].typeOrThrow);
    _isFutureOfNull(invoke.staticType as InterfaceType);
  }

  test_futureOr_return_null() async {
    MethodInvocation invoke = await _testFutureOr(r'''
    FutureOr<T> mk<T>(Future<T> x) => x;
    Future<int> f;
    test() => f.then((int x) {return null;});
    ''');
    _isFunction2Of(_isInt, _isNull)(
        invoke.argumentList.arguments[0].typeOrThrow);
    _isFutureOfNull(invoke.staticType as InterfaceType);
  }

  test_futureOr_upwards1() async {
    // Test that upwards inference correctly prefers to instantiate type
    // variables with the "smaller" solution when both are possible.
    MethodInvocation invoke = await _testFutureOr(r'''
    Future<T> mk<T>(FutureOr<T> x) => null;
    dynamic test() => mk(new Future<int>.value(42));
    ''');
    _isFutureOfInt(invoke.staticType as InterfaceType);
  }

  test_futureOr_upwards2() async {
    // Test that upwards inference fails when the solution doesn't
    // match the bound.
    MethodInvocation invoke = await _testFutureOr(r'''
    Future<T> mk<T extends Future<Object>>(FutureOr<T> x) => null;
    dynamic test() => mk(new Future<int>.value(42));
    ''', expectedErrors: [
      error(CompileTimeErrorCode.COULD_NOT_INFER, 111, 2),
    ]);
    _isFutureOfInt(invoke.staticType as InterfaceType);
  }

  test_futureOrNull_no_return() async {
    MethodInvocation invoke = await _testFutureOr(r'''
    FutureOr<T> mk<T>(Future<T> x) => x;
    Future<int> f;
    test() => f.then<Null>((int x) {});
    ''');
    _isFunction2Of(_isInt, _isNull)(
        invoke.argumentList.arguments[0].typeOrThrow);
    _isFutureOfNull(invoke.staticType as InterfaceType);
  }

  test_futureOrNull_no_return_value() async {
    MethodInvocation invoke = await _testFutureOr(r'''
    FutureOr<T> mk<T>(Future<T> x) => x;
    Future<int> f;
    test() => f.then<Null>((int x) {return;});
    ''');
    _isFunction2Of(_isInt, _isNull)(
        invoke.argumentList.arguments[0].typeOrThrow);
    _isFutureOfNull(invoke.staticType as InterfaceType);
  }

  test_futureOrNull_return_null() async {
    MethodInvocation invoke = await _testFutureOr(r'''
    FutureOr<T> mk<T>(Future<T> x) => x;
    Future<int> f;
    test() => f.then<Null>((int x) { return null;});
    ''');
    _isFunction2Of(_isInt, _isNull)(
        invoke.argumentList.arguments[0].typeOrThrow);
    _isFutureOfNull(invoke.staticType as InterfaceType);
  }

  test_generic_partial() async {
    // Test that upward and downward type inference handles partial
    // type schemas correctly.  Downwards inference in a partial context
    // (e.g. Map<String, ?>) should still allow upwards inference to fill
    // in the missing information.
    String code = r'''
class A<T> {
  A(T x);
  A.fromA(A<T> a) {}
  A.fromMap(Map<String, T> m) {}
  A.fromList(List<T> m) {}
  A.fromT(T t) {}
  A.fromB(B<T, String> a) {}
}

class B<S, T> {
  B(S s);
}

void test() {
    var a0 = new A.fromA(new A(3));
    var a1 = new A.fromMap({'hello' : 3});
    var a2 = new A.fromList([3]);
    var a3 = new A.fromT(3);
    var a4 = new A.fromB(new B(3));
}
   ''';
    await assertErrorsInCode(code, [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 205, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 241, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 284, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 318, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 347, 2),
    ]);

    Element elementA = AstFinder.getClass(unit, "A").declaredElement!;
    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "test");
    void check(int i) {
      var stmt = statements[i] as VariableDeclarationStatement;
      VariableDeclaration decl = stmt.variables.variables[0];
      Expression init = decl.initializer!;
      _isInstantiationOf(_hasElement(elementA))([_isInt])(init.typeOrThrow);
    }

    for (var i = 0; i < 5; i++) {
      check(i);
    }
  }

  test_inferConstructor_unknownTypeLowerBound() async {
    var code = r'''
        class C<T> {
          C(void callback(List<T> a));
        }
        test() {
          // downwards inference pushes List<?> and in parameter position this
          // becomes inferred as List<Null>.
          var c = new C((items) {});
        }
        ''';
    await assertErrorsInCode(code, [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 225, 1),
    ]);

    DartType cType = findElement.localVar('c').type;
    Element elementC = AstFinder.getClass(unit, "C").declaredElement!;

    _isInstantiationOf(_hasElement(elementC))([_isDynamic])(cType);
  }

  test_inference_error_arguments() async {
    var code = r'''
typedef R F<T, R>(T t);

F<T, T> g<T>(F<T, T> f) => (x) => f(f(x));

test() {
  var h = g((int x) => 42.0);
}
 ''';
    await assertErrorsInCode(code, [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 84, 1),
      error(CompileTimeErrorCode.COULD_NOT_INFER, 88, 1),
      error(CompileTimeErrorCode.ARGUMENT_TYPE_NOT_ASSIGNABLE, 90, 15),
    ]);
    _expectInferenceError(r'''
Couldn't infer type parameter 'T'.

Tried to infer 'double' for 'T' which doesn't work:
  Parameter 'f' declared as     'T Function(T)'
                but argument is 'double Function(int)'.

Consider passing explicit type argument(s) to the generic.

''');
  }

  test_inference_error_arguments2() async {
    var code = r'''
typedef R F<T, R>(T t);

F<T, T> g<T>(F<T, T> a, F<T, T> b) => (x) => a(b(x));

test() {
  var h = g((int x) => 42.0, (double x) => 42);
}
 ''';
    await assertErrorsInCode(code, [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 95, 1),
      error(CompileTimeErrorCode.COULD_NOT_INFER, 99, 1),
      error(CompileTimeErrorCode.ARGUMENT_TYPE_NOT_ASSIGNABLE, 101, 15),
      error(CompileTimeErrorCode.ARGUMENT_TYPE_NOT_ASSIGNABLE, 118, 16),
    ]);
    _expectInferenceError(r'''
Couldn't infer type parameter 'T'.

Tried to infer 'num' for 'T' which doesn't work:
  Parameter 'a' declared as     'T Function(T)'
                but argument is 'double Function(int)'.
  Parameter 'b' declared as     'T Function(T)'
                but argument is 'int Function(double)'.

Consider passing explicit type argument(s) to the generic.

''');
  }

  test_inference_error_extendsFromReturn() async {
    // This is not an inference error because we successfully infer Null.
    var code = r'''
T max<T extends num>(T x, T y) => x;

test() {
  String hello = max(1, 2);
}
 ''';
    await assertErrorsInCode(code, [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 56, 5),
      error(CompileTimeErrorCode.INVALID_CAST_LITERAL, 68, 1),
      error(CompileTimeErrorCode.INVALID_CAST_LITERAL, 71, 1),
    ]);

    var h = (AstFinder.getStatementsInTopLevelFunction(unit, "test")[0]
            as VariableDeclarationStatement)
        .variables
        .variables[0];
    var call = h.initializer as MethodInvocation;
    assertInvokeType(call, 'Null Function(Null, Null)');
  }

  test_inference_error_extendsFromReturn2() async {
    var code = r'''
typedef R F<T, R>(T t);
F<T, T> g<T extends num>() => (y) => y;

test() {
  F<String, String> hello = g();
}
 ''';
    await assertErrorsInCode(code, [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 94, 5),
      error(CompileTimeErrorCode.COULD_NOT_INFER, 102, 1),
    ]);

    _expectInferenceError(r'''
Couldn't infer type parameter 'T'.

Tried to infer 'String' for 'T' which doesn't work:
  Type parameter 'T' is declared to extend 'num' producing 'num'.
The type 'String' was inferred from:
  Return type declared as 'T Function(T)'
              used where  'String Function(String)' is required.

Consider passing explicit type argument(s) to the generic.

''');
  }

  test_inference_error_genericFunction() async {
    var code = r'''
T max<T extends num>(T x, T y) => x < y ? y : x;
abstract class Iterable<T> {
  T get first;
  S fold<S>(S s, S f(S s, T t));
}
test(Iterable values) {
  num n = values.fold(values.first as num, max);
}
 ''';
    await assertErrorsInCode(code, [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 158, 1),
      error(CompileTimeErrorCode.ARGUMENT_TYPE_NOT_ASSIGNABLE, 195, 3),
      error(CompileTimeErrorCode.COULD_NOT_INFER, 195, 3),
    ]);
    _expectInferenceError(r'''
Couldn't infer type parameter 'T'.

Tried to infer 'dynamic' for 'T' which doesn't work:
  Function type declared as 'T Function<T extends num>(T, T)'
                used where  'num Function(num, dynamic)' is required.

Consider passing explicit type argument(s) to the generic.

''');
  }

  test_inference_error_returnContext() async {
    var code = r'''
typedef R F<T, R>(T t);

F<T, T> g<T>(T t) => (x) => t;

test() {
  F<num, int> h = g(42);
}
 ''';
    await assertErrorsInCode(code, [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 80, 1),
      error(CompileTimeErrorCode.COULD_NOT_INFER, 84, 1),
    ]);
    _expectInferenceError(r'''
Couldn't infer type parameter 'T'.

Tried to infer 'num' for 'T' which doesn't work:
  Return type declared as 'T Function(T)'
              used where  'int Function(num)' is required.

Consider passing explicit type argument(s) to the generic.

''');
  }

  test_inference_hints() async {
    var code = r'''
      void main () {
        var x = 3;
        List<int> l0 = [];
     }
   ''';
    await assertErrorsInCode(code, [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 33, 1),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 58, 2),
    ]);
  }

  test_inference_simplePolymorphicRecursion_function() async {
    // Regression test for https://github.com/dart-lang/sdk/issues/30980
    // Check that inference works properly when inferring the type argument
    // for a self-recursive call with a function type
    var code = r'''
void _mergeSort<T>(T Function(T) list, int compare(T a, T b), T Function(T) target) {
  _mergeSort(list, compare, target);
  _mergeSort(list, compare, list);
  _mergeSort(target, compare, target);
  _mergeSort(target, compare, list);
}
    ''';
    await assertErrorsInCode(code, [
      error(HintCode.UNUSED_ELEMENT, 5, 10),
    ]);

    var body = AstFinder.getTopLevelFunction(unit, '_mergeSort')
        .functionExpression
        .body as BlockFunctionBody;
    var stmts = body.block.statements.cast<ExpressionStatement>();
    for (ExpressionStatement stmt in stmts) {
      var invoke = stmt.expression as MethodInvocation;
      assertInvokeType(invoke,
          'void Function(T Function(T), int Function(T, T), T Function(T))');
    }
  }

  test_inference_simplePolymorphicRecursion_interface() async {
    // Regression test for https://github.com/dart-lang/sdk/issues/30980
    // Check that inference works properly when inferring the type argument
    // for a self-recursive call with an interface type
    var code = r'''
void _mergeSort<T>(List<T> list, int compare(T a, T b), List<T> target) {
  _mergeSort(list, compare, target);
  _mergeSort(list, compare, list);
  _mergeSort(target, compare, target);
  _mergeSort(target, compare, list);
}
    ''';
    await assertErrorsInCode(code, [
      error(HintCode.UNUSED_ELEMENT, 5, 10),
    ]);

    var body = AstFinder.getTopLevelFunction(unit, '_mergeSort')
        .functionExpression
        .body as BlockFunctionBody;
    var stmts = body.block.statements.cast<ExpressionStatement>();
    for (ExpressionStatement stmt in stmts) {
      var invoke = stmt.expression as MethodInvocation;
      assertInvokeType(
          invoke, 'void Function(List<T>, int Function(T, T), List<T>)');
    }
  }

  test_inference_simplePolymorphicRecursion_simple() async {
    // Regression test for https://github.com/dart-lang/sdk/issues/30980
    // Check that inference works properly when inferring the type argument
    // for a self-recursive call with a simple type parameter
    var code = r'''
void _mergeSort<T>(T list, int compare(T a, T b), T target) {
  _mergeSort(list, compare, target);
  _mergeSort(list, compare, list);
  _mergeSort(target, compare, target);
  _mergeSort(target, compare, list);
}
    ''';
    await assertErrorsInCode(code, [
      error(HintCode.UNUSED_ELEMENT, 5, 10),
    ]);

    var body = AstFinder.getTopLevelFunction(unit, '_mergeSort')
        .functionExpression
        .body as BlockFunctionBody;
    var stmts = body.block.statements.cast<ExpressionStatement>();
    for (ExpressionStatement stmt in stmts) {
      var invoke = stmt.expression as MethodInvocation;
      assertInvokeType(invoke, 'void Function(T, int Function(T, T), T)');
    }
  }

  test_inferGenericInstantiation() async {
    // Verify that we don't infer '?` when we instantiate a generic function.
    var code = r'''
T f<T>(T x(T t)) => x(null);
S g<S>(S s) => s;
test() {
 var h = f(g);
}
    ''';
    await assertErrorsInCode(code, [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 61, 1),
    ]);

    var h = (AstFinder.getStatementsInTopLevelFunction(unit, "test")[0]
            as VariableDeclarationStatement)
        .variables
        .variables[0];
    _isDynamic(h.declaredElement!.type);
    var fCall = h.initializer as MethodInvocation;
    assertInvokeType(fCall, 'dynamic Function(dynamic Function(dynamic))');
    var g = fCall.argumentList.arguments[0];
    assertType(g.staticType, 'dynamic Function(dynamic)');
  }

  test_inferGenericInstantiation2() async {
    // Verify the behavior when we cannot infer an instantiation due to invalid
    // constraints from an outer generic method.
    var code = r'''
T max<T extends num>(T x, T y) => x < y ? y : x;
abstract class Iterable<T> {
  T get first;
  S fold<S>(S s, S f(S s, T t));
}
num test(Iterable values) => values.fold(values.first as num, max);
    ''';
    await assertErrorsInCode(code, [
      error(CompileTimeErrorCode.COULD_NOT_INFER, 190, 3),
      error(CompileTimeErrorCode.ARGUMENT_TYPE_NOT_ASSIGNABLE, 190, 3),
    ]);

    var fold = (AstFinder.getTopLevelFunction(unit, 'test')
            .functionExpression
            .body as ExpressionFunctionBody)
        .expression as MethodInvocation;
    assertInvokeType(fold, 'num Function(num, num Function(num, dynamic))');
    var max = fold.argumentList.arguments[1];
    // TODO(jmesserly): arguably num Function(num, num) is better here.
    assertType(max.staticType, 'dynamic Function(dynamic, dynamic)');
  }

  test_inferredFieldDeclaration_propagation() async {
    // Regression test for https://github.com/dart-lang/sdk/issues/25546
    String code = r'''
      abstract class A {
        Map<int, List<int>> get map;
      }
      class B extends A {
        var map = { 42: [] };
      }
      class C extends A {
        get map => { 43: [] };
      }
   ''';
    await assertNoErrorsInCode(code);

    Asserter<InterfaceType> assertListOfInt = _isListOf(_isInt);
    Asserter<InterfaceType> assertMapOfIntToListOfInt = _isMapOf(
        _isInt, (DartType type) => assertListOfInt(type as InterfaceType));

    VariableDeclaration mapB = AstFinder.getFieldInClass(unit, "B", "map");
    MethodDeclaration mapC = AstFinder.getMethodInClass(unit, "C", "map");
    assertMapOfIntToListOfInt(mapB.declaredElement!.type as InterfaceType);
    assertMapOfIntToListOfInt(
        mapC.declaredElement!.returnType as InterfaceType);

    var mapLiteralB = mapB.initializer as SetOrMapLiteral;
    var mapLiteralC =
        (mapC.body as ExpressionFunctionBody).expression as SetOrMapLiteral;
    assertMapOfIntToListOfInt(mapLiteralB.staticType as InterfaceType);
    assertMapOfIntToListOfInt(mapLiteralC.staticType as InterfaceType);

    var listLiteralB =
        (mapLiteralB.elements[0] as MapLiteralEntry).value as ListLiteral;
    var listLiteralC =
        (mapLiteralC.elements[0] as MapLiteralEntry).value as ListLiteral;
    assertListOfInt(listLiteralB.staticType as InterfaceType);
    assertListOfInt(listLiteralC.staticType as InterfaceType);
  }

  test_instanceCreation() async {
    String code = r'''
      class A<S, T> {
        S x;
        T y;
        A(this.x, this.y);
        A.named(this.x, this.y);
      }

      class B<S, T> extends A<T, S> {
        B(S y, T x) : super(x, y);
        B.named(S y, T x) : super.named(x, y);
      }

      class C<S> extends B<S, S> {
        C(S a) : super(a, a);
        C.named(S a) : super.named(a, a);
      }

      class D<S, T> extends B<T, int> {
        D(T a) : super(a, 3);
        D.named(T a) : super.named(a, 3);
      }

      class E<S, T> extends A<C<S>, T> {
        E(T a) : super(null, a);
      }

      class F<S, T> extends A<S, T> {
        F(S x, T y, {List<S> a, List<T> b}) : super(x, y);
        F.named(S x, T y, [S a, T b]) : super(a, b);
      }

      void test0() {
        A<int, String> a0 = new A(3, "hello");
        A<int, String> a1 = new A.named(3, "hello");
        A<int, String> a2 = new A<int, String>(3, "hello");
        A<int, String> a3 = new A<int, String>.named(3, "hello");
        A<int, String> a4 = new A<int, dynamic>(3, "hello");
        A<int, String> a5 = new A<dynamic, dynamic>.named(3, "hello");
      }
      void test1()  {
        A<int, String> a0 = new A("hello", 3);
        A<int, String> a1 = new A.named("hello", 3);
      }
      void test2() {
        A<int, String> a0 = new B("hello", 3);
        A<int, String> a1 = new B.named("hello", 3);
        A<int, String> a2 = new B<String, int>("hello", 3);
        A<int, String> a3 = new B<String, int>.named("hello", 3);
        A<int, String> a4 = new B<String, dynamic>("hello", 3);
        A<int, String> a5 = new B<dynamic, dynamic>.named("hello", 3);
      }
      void test3() {
        A<int, String> a0 = new B(3, "hello");
        A<int, String> a1 = new B.named(3, "hello");
      }
      void test4() {
        A<int, int> a0 = new C(3);
        A<int, int> a1 = new C.named(3);
        A<int, int> a2 = new C<int>(3);
        A<int, int> a3 = new C<int>.named(3);
        A<int, int> a4 = new C<dynamic>(3);
        A<int, int> a5 = new C<dynamic>.named(3);
      }
      void test5() {
        A<int, int> a0 = new C("hello");
        A<int, int> a1 = new C.named("hello");
      }
      void test6()  {
        A<int, String> a0 = new D("hello");
        A<int, String> a1 = new D.named("hello");
        A<int, String> a2 = new D<int, String>("hello");
        A<int, String> a3 = new D<String, String>.named("hello");
        A<int, String> a4 = new D<num, dynamic>("hello");
        A<int, String> a5 = new D<dynamic, dynamic>.named("hello");
      }
      void test7() {
        A<int, String> a0 = new D(3);
        A<int, String> a1 = new D.named(3);
      }
      void test8() {
        A<C<int>, String> a0 = new E("hello");
      }
      void test9() { // Check named and optional arguments
        A<int, String> a0 = new F(3, "hello", a: [3], b: ["hello"]);
        A<int, String> a1 = new F(3, "hello", a: ["hello"], b:[3]);
        A<int, String> a2 = new F.named(3, "hello", 3, "hello");
        A<int, String> a3 = new F.named(3, "hello");
        A<int, String> a4 = new F.named(3, "hello", "hello", 3);
        A<int, String> a5 = new F.named(3, "hello", "hello");
      }''';
    await assertErrorsInCode(code, [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 769, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 816, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 869, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 929, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 995, 2),
      error(CompileTimeErrorCode.INVALID_CAST_NEW_EXPR, 1000, 31),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 1056, 2),
      error(CompileTimeErrorCode.INVALID_CAST_NEW_EXPR, 1061, 41),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 1157, 2),
      error(CompileTimeErrorCode.ARGUMENT_TYPE_NOT_ASSIGNABLE, 1168, 7),
      error(CompileTimeErrorCode.ARGUMENT_TYPE_NOT_ASSIGNABLE, 1177, 1),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 1204, 2),
      error(CompileTimeErrorCode.ARGUMENT_TYPE_NOT_ASSIGNABLE, 1221, 7),
      error(CompileTimeErrorCode.ARGUMENT_TYPE_NOT_ASSIGNABLE, 1230, 1),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 1286, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 1333, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 1386, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 1446, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 1512, 2),
      error(CompileTimeErrorCode.INVALID_ASSIGNMENT, 1517, 34),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 1576, 2),
      error(CompileTimeErrorCode.INVALID_ASSIGNMENT, 1581, 41),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 1676, 2),
      error(CompileTimeErrorCode.ARGUMENT_TYPE_NOT_ASSIGNABLE, 1687, 1),
      error(CompileTimeErrorCode.ARGUMENT_TYPE_NOT_ASSIGNABLE, 1690, 7),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 1723, 2),
      error(CompileTimeErrorCode.ARGUMENT_TYPE_NOT_ASSIGNABLE, 1740, 1),
      error(CompileTimeErrorCode.ARGUMENT_TYPE_NOT_ASSIGNABLE, 1743, 7),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 1802, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 1837, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 1878, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 1918, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 1964, 2),
      error(CompileTimeErrorCode.INVALID_ASSIGNMENT, 1969, 17),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 2008, 2),
      error(CompileTimeErrorCode.INVALID_ASSIGNMENT, 2013, 23),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 2087, 2),
      error(CompileTimeErrorCode.ARGUMENT_TYPE_NOT_ASSIGNABLE, 2098, 7),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 2128, 2),
      error(CompileTimeErrorCode.ARGUMENT_TYPE_NOT_ASSIGNABLE, 2145, 7),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 2208, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 2252, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 2302, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 2359, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 2425, 2),
      error(CompileTimeErrorCode.INVALID_ASSIGNMENT, 2430, 28),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 2483, 2),
      error(CompileTimeErrorCode.INVALID_ASSIGNMENT, 2488, 38),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 2580, 2),
      error(CompileTimeErrorCode.ARGUMENT_TYPE_NOT_ASSIGNABLE, 2591, 1),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 2618, 2),
      error(CompileTimeErrorCode.ARGUMENT_TYPE_NOT_ASSIGNABLE, 2635, 1),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 2694, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 2805, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 2874, 2),
      error(CompileTimeErrorCode.LIST_ELEMENT_TYPE_NOT_ASSIGNABLE, 2901, 7),
      error(CompileTimeErrorCode.LIST_ELEMENT_TYPE_NOT_ASSIGNABLE, 2914, 1),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 2942, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 3007, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 3060, 2),
      error(CompileTimeErrorCode.ARGUMENT_TYPE_NOT_ASSIGNABLE, 3089, 7),
      error(CompileTimeErrorCode.ARGUMENT_TYPE_NOT_ASSIGNABLE, 3098, 1),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 3125, 2),
      error(CompileTimeErrorCode.ARGUMENT_TYPE_NOT_ASSIGNABLE, 3154, 7),
    ]);

    Expression rhs(AstNode stmt) {
      stmt as VariableDeclarationStatement;
      VariableDeclaration decl = stmt.variables.variables[0];
      Expression exp = decl.initializer!;
      return exp;
    }

    void hasType(Asserter<DartType> assertion, Expression exp) =>
        assertion(exp.typeOrThrow);

    Element elementA = AstFinder.getClass(unit, "A").declaredElement!;
    Element elementB = AstFinder.getClass(unit, "B").declaredElement!;
    Element elementC = AstFinder.getClass(unit, "C").declaredElement!;
    Element elementD = AstFinder.getClass(unit, "D").declaredElement!;
    Element elementE = AstFinder.getClass(unit, "E").declaredElement!;
    Element elementF = AstFinder.getClass(unit, "F").declaredElement!;

    AsserterBuilder<List<Asserter<DartType>>, DartType> assertAOf =
        _isInstantiationOf(_hasElement(elementA));
    AsserterBuilder<List<Asserter<DartType>>, DartType> assertBOf =
        _isInstantiationOf(_hasElement(elementB));
    AsserterBuilder<List<Asserter<DartType>>, DartType> assertCOf =
        _isInstantiationOf(_hasElement(elementC));
    AsserterBuilder<List<Asserter<DartType>>, DartType> assertDOf =
        _isInstantiationOf(_hasElement(elementD));
    AsserterBuilder<List<Asserter<DartType>>, DartType> assertEOf =
        _isInstantiationOf(_hasElement(elementE));
    AsserterBuilder<List<Asserter<DartType>>, DartType> assertFOf =
        _isInstantiationOf(_hasElement(elementF));

    {
      List<Statement> statements =
          AstFinder.getStatementsInTopLevelFunction(unit, "test0")
              .cast<VariableDeclarationStatement>();

      hasType(assertAOf([_isInt, _isString]), rhs(statements[0]));
      hasType(assertAOf([_isInt, _isString]), rhs(statements[0]));
      hasType(assertAOf([_isInt, _isString]), rhs(statements[1]));
      hasType(assertAOf([_isInt, _isString]), rhs(statements[2]));
      hasType(assertAOf([_isInt, _isString]), rhs(statements[3]));
      hasType(assertAOf([_isInt, _isDynamic]), rhs(statements[4]));
      hasType(assertAOf([_isDynamic, _isDynamic]), rhs(statements[5]));
    }

    {
      List<Statement> statements =
          AstFinder.getStatementsInTopLevelFunction(unit, "test1")
              .cast<VariableDeclarationStatement>();
      hasType(assertAOf([_isInt, _isString]), rhs(statements[0]));
      hasType(assertAOf([_isInt, _isString]), rhs(statements[1]));
    }

    {
      List<Statement> statements =
          AstFinder.getStatementsInTopLevelFunction(unit, "test2")
              .cast<VariableDeclarationStatement>();
      hasType(assertBOf([_isString, _isInt]), rhs(statements[0]));
      hasType(assertBOf([_isString, _isInt]), rhs(statements[1]));
      hasType(assertBOf([_isString, _isInt]), rhs(statements[2]));
      hasType(assertBOf([_isString, _isInt]), rhs(statements[3]));
      hasType(assertBOf([_isString, _isDynamic]), rhs(statements[4]));
      hasType(assertBOf([_isDynamic, _isDynamic]), rhs(statements[5]));
    }

    {
      List<Statement> statements =
          AstFinder.getStatementsInTopLevelFunction(unit, "test3")
              .cast<VariableDeclarationStatement>();
      hasType(assertBOf([_isString, _isInt]), rhs(statements[0]));
      hasType(assertBOf([_isString, _isInt]), rhs(statements[1]));
    }

    {
      List<Statement> statements =
          AstFinder.getStatementsInTopLevelFunction(unit, "test4")
              .cast<VariableDeclarationStatement>();
      hasType(assertCOf([_isInt]), rhs(statements[0]));
      hasType(assertCOf([_isInt]), rhs(statements[1]));
      hasType(assertCOf([_isInt]), rhs(statements[2]));
      hasType(assertCOf([_isInt]), rhs(statements[3]));
      hasType(assertCOf([_isDynamic]), rhs(statements[4]));
      hasType(assertCOf([_isDynamic]), rhs(statements[5]));
    }

    {
      List<Statement> statements =
          AstFinder.getStatementsInTopLevelFunction(unit, "test5")
              .cast<VariableDeclarationStatement>();
      hasType(assertCOf([_isInt]), rhs(statements[0]));
      hasType(assertCOf([_isInt]), rhs(statements[1]));
    }

    {
      // The first type parameter is not constrained by the
      // context.  We could choose a tighter type, but currently
      // we just use dynamic.
      List<Statement> statements =
          AstFinder.getStatementsInTopLevelFunction(unit, "test6")
              .cast<VariableDeclarationStatement>();
      hasType(assertDOf([_isDynamic, _isString]), rhs(statements[0]));
      hasType(assertDOf([_isDynamic, _isString]), rhs(statements[1]));
      hasType(assertDOf([_isInt, _isString]), rhs(statements[2]));
      hasType(assertDOf([_isString, _isString]), rhs(statements[3]));
      hasType(assertDOf([_isNum, _isDynamic]), rhs(statements[4]));
      hasType(assertDOf([_isDynamic, _isDynamic]), rhs(statements[5]));
    }

    {
      List<Statement> statements =
          AstFinder.getStatementsInTopLevelFunction(unit, "test7")
              .cast<VariableDeclarationStatement>();
      hasType(assertDOf([_isDynamic, _isString]), rhs(statements[0]));
      hasType(assertDOf([_isDynamic, _isString]), rhs(statements[1]));
    }

    {
      List<Statement> statements =
          AstFinder.getStatementsInTopLevelFunction(unit, "test8")
              .cast<VariableDeclarationStatement>();
      hasType(assertEOf([_isInt, _isString]), rhs(statements[0]));
    }

    {
      List<Statement> statements =
          AstFinder.getStatementsInTopLevelFunction(unit, "test9")
              .cast<VariableDeclarationStatement>();
      hasType(assertFOf([_isInt, _isString]), rhs(statements[0]));
      hasType(assertFOf([_isInt, _isString]), rhs(statements[1]));
      hasType(assertFOf([_isInt, _isString]), rhs(statements[2]));
      hasType(assertFOf([_isInt, _isString]), rhs(statements[3]));
      hasType(assertFOf([_isInt, _isString]), rhs(statements[4]));
      hasType(assertFOf([_isInt, _isString]), rhs(statements[5]));
    }
  }

  test_listLiteral_nested() async {
    String code = r'''
      void main () {
        List<List<int>> l0 = [[]];
        Iterable<List<int>> l1 = [[3]];
        Iterable<List<int>> l2 = [[3], [4]];
        List<List<int>> l3 = [["hello", 3], []];
     }
   ''';
    await assertErrorsInCode(code, [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 45, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 84, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 124, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 165, 2),
      error(CompileTimeErrorCode.LIST_ELEMENT_TYPE_NOT_ASSIGNABLE, 172, 7),
    ]);

    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    ListLiteral literal(int i) {
      var stmt = statements[i] as VariableDeclarationStatement;
      VariableDeclaration decl = stmt.variables.variables[0];
      var exp = decl.initializer as ListLiteral;
      return exp;
    }

    Asserter<InterfaceType> assertListOfInt = _isListOf(_isInt);
    Asserter<InterfaceType> assertListOfListOfInt =
        _isListOf((DartType type) => assertListOfInt(type as InterfaceType));

    assertListOfListOfInt(literal(0).staticType as InterfaceType);
    assertListOfListOfInt(literal(1).staticType as InterfaceType);
    assertListOfListOfInt(literal(2).staticType as InterfaceType);
    assertListOfListOfInt(literal(3).staticType as InterfaceType);

    assertListOfInt(
        (literal(1).elements[0] as Expression).staticType as InterfaceType);
    assertListOfInt(
        (literal(2).elements[0] as Expression).staticType as InterfaceType);
    assertListOfInt(
        (literal(3).elements[0] as Expression).staticType as InterfaceType);
  }

  test_listLiteral_simple() async {
    String code = r'''
      void main () {
        List<int> l0 = [];
        List<int> l1 = [3];
        List<int> l2 = ["hello"];
        List<int> l3 = ["hello", 3];
     }
   ''';
    await assertErrorsInCode(code, [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 39, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 66, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 94, 2),
      error(CompileTimeErrorCode.LIST_ELEMENT_TYPE_NOT_ASSIGNABLE, 100, 7),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 128, 2),
      error(CompileTimeErrorCode.LIST_ELEMENT_TYPE_NOT_ASSIGNABLE, 134, 7),
    ]);

    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    DartType literal(int i) {
      var stmt = statements[i] as VariableDeclarationStatement;
      VariableDeclaration decl = stmt.variables.variables[0];
      var exp = decl.initializer as ListLiteral;
      return exp.typeOrThrow;
    }

    Asserter<InterfaceType> assertListOfInt = _isListOf(_isInt);

    assertListOfInt(literal(0) as InterfaceType);
    assertListOfInt(literal(1) as InterfaceType);
    assertListOfInt(literal(2) as InterfaceType);
    assertListOfInt(literal(3) as InterfaceType);
  }

  test_listLiteral_simple_const() async {
    String code = r'''
      void main () {
        const List<int> c0 = const [];
        const List<int> c1 = const [3];
        const List<int> c2 = const ["hello"];
        const List<int> c3 = const ["hello", 3];
     }
   ''';
    await assertErrorsInCode(code, [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 45, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 84, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 124, 2),
      error(CompileTimeErrorCode.LIST_ELEMENT_TYPE_NOT_ASSIGNABLE, 136, 7),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 170, 2),
      error(CompileTimeErrorCode.LIST_ELEMENT_TYPE_NOT_ASSIGNABLE, 182, 7),
    ]);

    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    DartType literal(int i) {
      var stmt = statements[i] as VariableDeclarationStatement;
      VariableDeclaration decl = stmt.variables.variables[0];
      var exp = decl.initializer as ListLiteral;
      return exp.typeOrThrow;
    }

    Asserter<InterfaceType> assertListOfInt = _isListOf(_isInt);

    assertListOfInt(literal(0) as InterfaceType);
    assertListOfInt(literal(1) as InterfaceType);
    assertListOfInt(literal(2) as InterfaceType);
    assertListOfInt(literal(3) as InterfaceType);
  }

  test_listLiteral_simple_disabled() async {
    String code = r'''
      void main () {
        List<int> l0 = <num>[];
        List<int> l1 = <num>[3];
        List<int> l2 = <String>["hello"];
        List<int> l3 = <dynamic>["hello", 3];
     }
   ''';
    await assertErrorsInCode(code, [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 39, 2),
      error(CompileTimeErrorCode.INVALID_CAST_LITERAL_LIST, 44, 7),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 71, 2),
      error(CompileTimeErrorCode.INVALID_CAST_LITERAL_LIST, 76, 8),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 104, 2),
      error(CompileTimeErrorCode.INVALID_ASSIGNMENT, 109, 17),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 146, 2),
      error(CompileTimeErrorCode.INVALID_CAST_LITERAL_LIST, 151, 21),
    ]);

    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    DartType literal(int i) {
      var stmt = statements[i] as VariableDeclarationStatement;
      VariableDeclaration decl = stmt.variables.variables[0];
      var exp = decl.initializer as ListLiteral;
      return exp.typeOrThrow;
    }

    _isListOf(_isNum)(literal(0) as InterfaceType);
    _isListOf(_isNum)(literal(1) as InterfaceType);
    _isListOf(_isString)(literal(2) as InterfaceType);
    _isListOf(_isDynamic)(literal(3) as InterfaceType);
  }

  test_listLiteral_simple_subtype() async {
    String code = r'''
      void main () {
        Iterable<int> l0 = [];
        Iterable<int> l1 = [3];
        Iterable<int> l2 = ["hello"];
        Iterable<int> l3 = ["hello", 3];
     }
   ''';
    await assertErrorsInCode(code, [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 43, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 74, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 106, 2),
      error(CompileTimeErrorCode.LIST_ELEMENT_TYPE_NOT_ASSIGNABLE, 112, 7),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 144, 2),
      error(CompileTimeErrorCode.LIST_ELEMENT_TYPE_NOT_ASSIGNABLE, 150, 7),
    ]);

    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    InterfaceType literal(int i) {
      var stmt = statements[i] as VariableDeclarationStatement;
      VariableDeclaration decl = stmt.variables.variables[0];
      var exp = decl.initializer as ListLiteral;
      return exp.staticType as InterfaceType;
    }

    Asserter<InterfaceType> assertListOfInt = _isListOf(_isInt);

    assertListOfInt(literal(0));
    assertListOfInt(literal(1));
    assertListOfInt(literal(2));
    assertListOfInt(literal(3));
  }

  test_mapLiteral_nested() async {
    String code = r'''
      void main () {
        Map<int, List<String>> l0 = {};
        Map<int, List<String>> l1 = {3: ["hello"]};
        Map<int, List<String>> l2 = {"hello": ["hello"]};
        Map<int, List<String>> l3 = {3: [3]};
        Map<int, List<String>> l4 = {3:["hello"], "hello": [3]};
     }
   ''';
    await assertErrorsInCode(code, [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 52, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 92, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 144, 2),
      error(CompileTimeErrorCode.MAP_KEY_TYPE_NOT_ASSIGNABLE, 150, 7),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 202, 2),
      error(CompileTimeErrorCode.LIST_ELEMENT_TYPE_NOT_ASSIGNABLE, 212, 1),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 248, 2),
      error(CompileTimeErrorCode.MAP_KEY_TYPE_NOT_ASSIGNABLE, 267, 7),
      error(CompileTimeErrorCode.LIST_ELEMENT_TYPE_NOT_ASSIGNABLE, 277, 1),
    ]);

    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    SetOrMapLiteral literal(int i) {
      var stmt = statements[i] as VariableDeclarationStatement;
      VariableDeclaration decl = stmt.variables.variables[0];
      var exp = decl.initializer as SetOrMapLiteral;
      return exp;
    }

    Asserter<InterfaceType> assertListOfString = _isListOf(_isString);
    Asserter<InterfaceType> assertMapOfIntToListOfString = _isMapOf(
        _isInt, (DartType type) => assertListOfString(type as InterfaceType));

    assertMapOfIntToListOfString(literal(0).staticType as InterfaceType);
    assertMapOfIntToListOfString(literal(1).staticType as InterfaceType);
    assertMapOfIntToListOfString(literal(2).staticType as InterfaceType);
    assertMapOfIntToListOfString(literal(3).staticType as InterfaceType);
    assertMapOfIntToListOfString(literal(4).staticType as InterfaceType);

    assertListOfString((literal(1).elements[0] as MapLiteralEntry)
        .value
        .staticType as InterfaceType);
    assertListOfString((literal(2).elements[0] as MapLiteralEntry)
        .value
        .staticType as InterfaceType);
    assertListOfString((literal(3).elements[0] as MapLiteralEntry)
        .value
        .staticType as InterfaceType);
    assertListOfString((literal(4).elements[0] as MapLiteralEntry)
        .value
        .staticType as InterfaceType);
  }

  test_mapLiteral_simple() async {
    String code = r'''
      void main () {
        Map<int, String> l0 = {};
        Map<int, String> l1 = {3: "hello"};
        Map<int, String> l2 = {"hello": "hello"};
        Map<int, String> l3 = {3: 3};
        Map<int, String> l4 = {3:"hello", "hello": 3};
     }
   ''';
    await assertErrorsInCode(code, [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 46, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 80, 2),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 124, 2),
      error(CompileTimeErrorCode.MAP_KEY_TYPE_NOT_ASSIGNABLE, 130, 7),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 174, 2),
      error(CompileTimeErrorCode.MAP_VALUE_TYPE_NOT_ASSIGNABLE, 183, 1),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 212, 2),
      error(CompileTimeErrorCode.MAP_KEY_TYPE_NOT_ASSIGNABLE, 229, 7),
      error(CompileTimeErrorCode.MAP_VALUE_TYPE_NOT_ASSIGNABLE, 238, 1),
    ]);

    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    InterfaceType literal(int i) {
      var stmt = statements[i] as VariableDeclarationStatement;
      VariableDeclaration decl = stmt.variables.variables[0];
      var exp = decl.initializer as SetOrMapLiteral;
      return exp.staticType as InterfaceType;
    }

    Asserter<InterfaceType> assertMapOfIntToString =
        _isMapOf(_isInt, _isString);

    assertMapOfIntToString(literal(0));
    assertMapOfIntToString(literal(1));
    assertMapOfIntToString(literal(2));
    assertMapOfIntToString(literal(3));
  }

  test_mapLiteral_simple_disabled() async {
    String code = r'''
      void main () {
        Map<int, String> l0 = <int, dynamic>{};
        Map<int, String> l1 = <int, dynamic>{3: "hello"};
        Map<int, String> l2 = <int, dynamic>{"hello": "hello"};
        Map<int, String> l3 = <int, dynamic>{3: 3};
     }
   ''';
    await assertErrorsInCode(code, [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 46, 2),
      error(CompileTimeErrorCode.INVALID_CAST_LITERAL_MAP, 51, 16),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 94, 2),
      error(CompileTimeErrorCode.INVALID_CAST_LITERAL_MAP, 99, 26),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 152, 2),
      error(CompileTimeErrorCode.INVALID_CAST_LITERAL_MAP, 157, 32),
      error(CompileTimeErrorCode.MAP_KEY_TYPE_NOT_ASSIGNABLE, 172, 7),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 216, 2),
      error(CompileTimeErrorCode.INVALID_CAST_LITERAL_MAP, 221, 20),
    ]);

    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    InterfaceType literal(int i) {
      var stmt = statements[i] as VariableDeclarationStatement;
      VariableDeclaration decl = stmt.variables.variables[0];
      var exp = decl.initializer as SetOrMapLiteral;
      return exp.staticType as InterfaceType;
    }

    Asserter<InterfaceType> assertMapOfIntToDynamic =
        _isMapOf(_isInt, _isDynamic);

    assertMapOfIntToDynamic(literal(0));
    assertMapOfIntToDynamic(literal(1));
    assertMapOfIntToDynamic(literal(2));
    assertMapOfIntToDynamic(literal(3));
  }

  test_methodDeclaration_body_propagation() async {
    String code = r'''
      class A {
        List<String> m0(int x) => ["hello"];
        List<String> m1(int x) {return [3];}
      }
   ''';
    await assertErrorsInCode(code, [
      error(CompileTimeErrorCode.LIST_ELEMENT_TYPE_NOT_ASSIGNABLE, 101, 1),
    ]);

    Expression methodReturnValue(String methodName) {
      MethodDeclaration method =
          AstFinder.getMethodInClass(unit, "A", methodName);
      FunctionBody body = method.body;
      if (body is ExpressionFunctionBody) {
        return body.expression;
      } else {
        Statement stmt = (body as BlockFunctionBody).block.statements[0];
        return (stmt as ReturnStatement).expression!;
      }
    }

    Asserter<InterfaceType> assertListOfString = _isListOf(_isString);
    assertListOfString(methodReturnValue("m0").staticType as InterfaceType);
    assertListOfString(methodReturnValue("m1").staticType as InterfaceType);
  }

  test_partialTypes1() async {
    // Test that downwards inference with a partial type
    // correctly uses the partial information to fill in subterm
    // types
    String code = r'''
    typedef To Func1<From, To>(From x);
    S f<S, T>(Func1<S, T> g) => null;
    String test() => f((l) => l.length);
   ''';
    await assertNoErrorsInCode(code);

    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
    var body = test.functionExpression.body as ExpressionFunctionBody;
    _isString(body.expression.typeOrThrow);
    var invoke = body.expression as MethodInvocation;
    var function = invoke.argumentList.arguments[0] as FunctionExpression;
    ExecutableElement f0 = function.declaredElement!;
    FunctionType type = f0.type;
    _isFunction2Of(_isString, _isInt)(type);
  }

  test_pinning_multipleConstraints1() async {
    // Test that downwards inference with two different downwards covariant
    // constraints on the same parameter correctly fails to infer when
    // the types do not share a common subtype
    String code = r'''
    class A<S, T> {
      S s;
      T t;
    }
    class B<S> extends A<S, S> { B(S s); }
    A<int, String> test() => new B(3);
   ''';
    await assertErrorsInCode(code, [
      error(CompileTimeErrorCode.INVALID_CAST_LITERAL, 126, 1),
    ]);

    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
    var body = test.functionExpression.body as ExpressionFunctionBody;
    DartType type = body.expression.typeOrThrow;

    Element elementB = AstFinder.getClass(unit, "B").declaredElement!;

    _isInstantiationOf(_hasElement(elementB))([_isNull])(type);
  }

  test_pinning_multipleConstraints2() async {
    // Test that downwards inference with two identical downwards covariant
    // constraints on the same parameter correctly infers and pins the type
    String code = r'''
    class A<S, T> {
      S s;
      T t;
    }
    class B<S> extends A<S, S> { B(S s); }
    A<num, num> test() => new B(3);
   ''';
    await assertNoErrorsInCode(code);

    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
    var body = test.functionExpression.body as ExpressionFunctionBody;
    DartType type = body.expression.typeOrThrow;

    Element elementB = AstFinder.getClass(unit, "B").declaredElement!;

    _isInstantiationOf(_hasElement(elementB))([_isNum])(type);
  }

  test_pinning_multipleConstraints3() async {
    // Test that downwards inference with two different downwards covariant
    // constraints on the same parameter correctly fails to infer when
    // the types do not share a common subtype, but do share a common supertype
    String code = r'''
    class A<S, T> {
      S s;
      T t;
    }
    class B<S> extends A<S, S> { B(S s); }
    A<int, double> test() => new B(3);
   ''';
    await assertErrorsInCode(code, [
      error(CompileTimeErrorCode.INVALID_CAST_LITERAL, 126, 1),
    ]);

    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
    var body = test.functionExpression.body as ExpressionFunctionBody;
    DartType type = body.expression.typeOrThrow;

    Element elementB = AstFinder.getClass(unit, "B").declaredElement!;

    _isInstantiationOf(_hasElement(elementB))([_isNull])(type);
  }

  test_pinning_multipleConstraints4() async {
    // Test that downwards inference with two subtype related downwards
    // covariant constraints on the same parameter correctly infers and pins
    // the type
    String code = r'''
    class A<S, T> {
      S s;
      T t;
    }
    class B<S> extends A<S, S> {}
    A<int, num> test() => new B();
   ''';
    await assertNoErrorsInCode(code);

    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
    var body = test.functionExpression.body as ExpressionFunctionBody;
    DartType type = body.expression.typeOrThrow;

    Element elementB = AstFinder.getClass(unit, "B").declaredElement!;

    _isInstantiationOf(_hasElement(elementB))([_isInt])(type);
  }

  test_pinning_multipleConstraints_contravariant1() async {
    // Test that downwards inference with two different downwards contravariant
    // constraints on the same parameter chooses the upper bound
    // when the only supertype is Object
    String code = r'''
    class A<S, T> {
      S s;
      T t;
    }
    class B<S> extends A<S, S> {}
    typedef void Contra1<T>(T x);
    Contra1<A<S, S>> mkA<S>() => (A<S, S> x) {};
    Contra1<A<int, String>> test() => mkA();
   ''';
    await assertNoErrorsInCode(code);

    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
    var body = test.functionExpression.body as ExpressionFunctionBody;
    var functionType = body.expression.staticType as FunctionType;
    DartType type = functionType.normalParameterTypes[0];

    Element elementA = AstFinder.getClass(unit, "A").declaredElement!;

    _isInstantiationOf(_hasElement(elementA))([_isObject, _isObject])(type);
  }

  test_pinning_multipleConstraints_contravariant2() async {
    // Test that downwards inference with two identical downwards contravariant
    // constraints on the same parameter correctly pins the type
    String code = r'''
    class A<S, T> {
      S s;
      T t;
    }
    class B<S> extends A<S, S> {}
    typedef void Contra1<T>(T x);
    Contra1<A<S, S>> mkA<S>() => (A<S, S> x) {};
    Contra1<A<num, num>> test() => mkA();
   ''';
    await assertNoErrorsInCode(code);

    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
    var body = test.functionExpression.body as ExpressionFunctionBody;
    var functionType = body.expression.staticType as FunctionType;
    DartType type = functionType.normalParameterTypes[0];

    Element elementA = AstFinder.getClass(unit, "A").declaredElement!;

    _isInstantiationOf(_hasElement(elementA))([_isNum, _isNum])(type);
  }

  test_pinning_multipleConstraints_contravariant3() async {
    // Test that downwards inference with two different downwards contravariant
    // constraints on the same parameter correctly choose the least upper bound
    // when they share a common supertype
    String code = r'''
    class A<S, T> {
      S s;
      T t;
    }
    class B<S> extends A<S, S> {}
    typedef void Contra1<T>(T x);
    Contra1<A<S, S>> mkA<S>() => (A<S, S> x) {};
    Contra1<A<int, double>> test() => mkA();
   ''';
    await assertNoErrorsInCode(code);

    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
    var body = test.functionExpression.body as ExpressionFunctionBody;
    var functionType = body.expression.staticType as FunctionType;
    DartType type = functionType.normalParameterTypes[0];

    Element elementA = AstFinder.getClass(unit, "A").declaredElement!;

    _isInstantiationOf(_hasElement(elementA))([_isNum, _isNum])(type);
  }

  test_pinning_multipleConstraints_contravariant4() async {
    // Test that downwards inference with two different downwards contravariant
    // constraints on the same parameter correctly choose the least upper bound
    // when one is a subtype of the other
    String code = r'''
    class A<S, T> {
      S s;
      T t;
    }
    class B<S> extends A<S, S> {}
    typedef void Contra1<T>(T x);
    Contra1<A<S, S>> mkA<S>() => (A<S, S> x) {};
    Contra1<A<int, num>> test() => mkA();
   ''';
    await assertNoErrorsInCode(code);

    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
    var body = test.functionExpression.body as ExpressionFunctionBody;
    var functionType = body.expression.staticType as FunctionType;
    DartType type = functionType.normalParameterTypes[0];

    Element elementA = AstFinder.getClass(unit, "A").declaredElement!;

    _isInstantiationOf(_hasElement(elementA))([_isNum, _isNum])(type);
  }

  test_redirectedConstructor_named() async {
    var code = r'''
class A<T, U> implements B<T, U> {
  A.named();
}

class B<T2, U2> {
  factory B() = A.named;
}
   ''';
    await assertNoErrorsInCode(code);

    var b = unit.declarations[1] as ClassDeclaration;
    var bConstructor = b.members[0] as ConstructorDeclaration;
    var redirected = bConstructor.redirectedConstructor as ConstructorName;

    var typeName = redirected.type;
    assertType(typeName.type, 'A<T2, U2>');
    assertType(typeName.type, 'A<T2, U2>');

    var constructorMember = redirected.staticElement!;
    expect(
      constructorMember.getDisplayString(withNullability: false),
      'A<T2, U2> A.named()',
    );
    expect(redirected.name!.staticElement, constructorMember);
  }

  test_redirectedConstructor_self() async {
    await assertNoErrorsInCode(r'''
class A<T> {
  A();
  factory A.redirected() = A;
}
''');
  }

  test_redirectedConstructor_unnamed() async {
    await assertNoErrorsInCode(r'''
class A<T, U> implements B<T, U> {
  A();
}

class B<T2, U2> {
  factory B() = A;
}
''');

    var b = result.unit.declarations[1] as ClassDeclaration;
    var bConstructor = b.members[0] as ConstructorDeclaration;
    var redirected = bConstructor.redirectedConstructor as ConstructorName;

    var typeName = redirected.type;
    assertType(typeName.type, 'A<T2, U2>');
    assertType(typeName.type, 'A<T2, U2>');

    expect(redirected.name, isNull);
    expect(
      redirected.staticElement!.getDisplayString(withNullability: false),
      'A<T2, U2> A()',
    );
  }

  test_redirectingConstructor_propagation() async {
    String code = r'''
      class A {
        A() : this.named([]);
        A.named(List<String> x);
      }
   ''';
    await assertNoErrorsInCode(code);

    ConstructorDeclaration constructor =
        AstFinder.getConstructorInClass(unit, "A", null);
    var invocation =
        constructor.initializers[0] as RedirectingConstructorInvocation;
    Expression exp = invocation.argumentList.arguments[0];
    _isListOf(_isString)(exp.staticType as InterfaceType);
  }

  test_returnType_variance1() async {
    // Check that downwards inference correctly pins a type parameter
    // when the parameter is constrained in a contravariant position
    String code = r'''
    typedef To Func1<From, To>(From x);
    Func1<T, String> f<T>(T x) => null;
    Func1<num, String> test() => f(42);
   ''';
    await assertNoErrorsInCode(code);

    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
    var body = test.functionExpression.body as ExpressionFunctionBody;
    var invoke = body.expression as MethodInvocation;
    _isFunction2Of(_isNum, _isFunction2Of(_isNum, _isString))(
        invoke.staticInvokeType!);
  }

  test_returnType_variance2() async {
    // Check that downwards inference correctly pins a type parameter
    // when the parameter is constrained in a covariant position
    String code = r'''
    typedef To Func1<From, To>(From x);
    Func1<String, T> f<T>(T x) => null;
    Func1<String, num> test() => f(42);
   ''';
    await assertNoErrorsInCode(code);

    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
    var body = test.functionExpression.body as ExpressionFunctionBody;
    var invoke = body.expression as MethodInvocation;
    _isFunction2Of(_isNum, _isFunction2Of(_isString, _isNum))(
        invoke.staticInvokeType!);
  }

  test_returnType_variance3() async {
    // Check that the variance heuristic chooses the most precise type
    // when the return type uses the variable in a contravariant position
    // and there is no downwards constraint.
    String code = r'''
    typedef To Func1<From, To>(From x);
    Func1<T, String> f<T>(T x, g(T x)) => null;
    dynamic test() => f(42, (num x) => x);
   ''';
    await assertNoErrorsInCode(code);

    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
    var body = test.functionExpression.body as ExpressionFunctionBody;
    var functionType = body.expression.staticType as FunctionType;
    DartType type = functionType.normalParameterTypes[0];
    _isInt(type);
  }

  test_returnType_variance4() async {
    // Check that the variance heuristic chooses the more precise type
    // when the return type uses the variable in a covariant position
    // and there is no downwards constraint
    String code = r'''
    typedef To Func1<From, To>(From x);
    Func1<String, T> f<T>(T x, g(T x)) => null;
    dynamic test() => f(42, (num x) => x);
   ''';
    await assertNoErrorsInCode(code);

    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
    var body = test.functionExpression.body as ExpressionFunctionBody;
    var functionType = body.expression.staticType as FunctionType;
    DartType type = functionType.returnType;
    _isInt(type);
  }

  test_returnType_variance5() async {
    // Check that pinning works correctly with a partial type
    // when the return type uses the variable in a contravariant position
    String code = r'''
    typedef To Func1<From, To>(From x);
    Func1<T, String> f<T>(T x) => null;
    T g<T, S>(Func1<T, S> f) => null;
    num test() => g(f(3));
   ''';
    await assertNoErrorsInCode(code);

    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
    var body = test.functionExpression.body as ExpressionFunctionBody;
    var call = body.expression as MethodInvocation;
    _isNum(call.typeOrThrow);
    _isFunction2Of(_isFunction2Of(_isNum, _isString), _isNum)(
        call.staticInvokeType!);
  }

  test_returnType_variance6() async {
    // Check that pinning works correctly with a partial type
    // when the return type uses the variable in a covariant position
    String code = r'''
    typedef To Func1<From, To>(From x);
    Func1<String, T> f<T>(T x) => null;
    T g<T, S>(Func1<S, T> f) => null;
    num test() => g(f(3));
   ''';
    await assertNoErrorsInCode(code);

    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
    var body = test.functionExpression.body as ExpressionFunctionBody;
    var call = body.expression as MethodInvocation;
    _isNum(call.typeOrThrow);
    _isFunction2Of(_isFunction2Of(_isString, _isNum), _isNum)(
        call.staticInvokeType!);
  }

  test_superConstructorInvocation_propagation() async {
    String code = r'''
      class B {
        B(List<String> p);
      }
      class A extends B {
        A() : super([]);
      }
   ''';
    await assertNoErrorsInCode(code);

    ConstructorDeclaration constructor =
        AstFinder.getConstructorInClass(unit, "A", null);
    var invocation = constructor.initializers[0] as SuperConstructorInvocation;
    Expression exp = invocation.argumentList.arguments[0];
    _isListOf(_isString)(exp.staticType as InterfaceType);
  }

  /// Verifies the result has [CompileTimeErrorCode.COULD_NOT_INFER] with
  /// the expected [errorMessage].
  void _expectInferenceError(String errorMessage) {
    var errors = result.errors
        .where((e) => e.errorCode == CompileTimeErrorCode.COULD_NOT_INFER)
        .map((e) => e.message)
        .toList();
    expect(errors.length, 1);
    var actual = errors[0];
    expect(actual,
        errorMessage, // Print the literal error message for easy copy+paste:
        reason: 'Actual error did not match expected error:\n$actual');
  }

  /// Helper method for testing `FutureOr<T>`.
  ///
  /// Validates that [code] produces [errors]. It should define a function
  /// "test", whose body is an expression that invokes a method. Returns that
  /// invocation.
  Future<MethodInvocation> _testFutureOr(String code,
      {List<ExpectedError> expectedErrors = const []}) async {
    var fullCode = """
import "dart:async";

$code
""";
    await assertErrorsInCode(fullCode, expectedErrors);

    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
    var body = test.functionExpression.body as ExpressionFunctionBody;
    return body.expression as MethodInvocation;
  }
}

@reflectiveTest
class StrongModeStaticTypeAnalyzer2Test extends StaticTypeAnalyzer2TestShared {
  void expectStaticInvokeType(String search, String expected) {
    var invocation = findNode.simple(search).parent as MethodInvocation;
    assertInvokeType(invocation, expected);
  }

  test_dynamicObjectGetter_hashCode() async {
    await assertErrorsInCode(r'''
main() {
  dynamic a = null;
  var foo = a.hashCode;
}
''', [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 35, 3),
    ]);
    expectInitializerType('foo', 'int');
  }

  test_futureOr_promotion1() async {
    // Test that promotion from FutureOr<T> to T works for concrete types
    String code = r'''
    import "dart:async";
    dynamic test(FutureOr<int> x) => (x is int) && (x.abs() == 0);
   ''';
    await assertNoErrorsInCode(code);
  }

  test_futureOr_promotion2() async {
    // Test that promotion from FutureOr<T> to Future<T> works for concrete
    // types
    String code = r'''
    import "dart:async";
    dynamic test(FutureOr<int> x) => (x is Future<int>) &&
                                     (x.then((x) => x) == null);
   ''';
    await assertNoErrorsInCode(code);
  }

  test_futureOr_promotion3() async {
    // Test that promotion from FutureOr<T> to T works for type
    // parameters T
    String code = r'''
    import "dart:async";
    dynamic test<T extends num>(FutureOr<T> x) => (x is T) &&
                                                  (x.abs() == 0);
   ''';
    await assertNoErrorsInCode(code);
  }

  test_futureOr_promotion4() async {
    // Test that promotion from FutureOr<T> to Future<T> works for type
    // parameters T
    String code = r'''
    import "dart:async";
    dynamic test<T extends num>(FutureOr<T> x) => (x is Future<T>) &&
                                                  (x.then((x) => x) == null);
   ''';
    await assertNoErrorsInCode(code);
  }

  test_generalizedVoid_assignToVoidOk() async {
    await assertErrorsInCode(r'''
void main() {
  void x;
  x = 42;
}
''', [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 21, 1),
    ]);
  }

  test_genericFunction() async {
    await assertNoErrorsInCode(r'T f<T>(T x) => null;');
    expectFunctionType('f', 'T Function<T>(T)', typeFormals: '[T]');
    SimpleIdentifier f = findNode.simple('f');
    var e = f.staticElement as FunctionElementImpl;
    FunctionType ft = e.type.instantiate([typeProvider.stringType]);
    assertType(ft, 'String Function(String)');
  }

  test_genericFunction_bounds() async {
    await assertNoErrorsInCode(r'T f<T extends num>(T x) => null;');
    expectFunctionType('f', 'T Function<T extends num>(T)',
        typeFormals: '[T extends num]');
  }

  test_genericFunction_parameter() async {
    await assertNoErrorsInCode(r'''
void g(T f<T>(T x)) {}
''');
    var type = expectFunctionType2('f', 'T Function<T>(T)');
    FunctionType ft = type.instantiate([typeProvider.stringType]);
    assertType(ft, 'String Function(String)');
  }

  test_genericFunction_static() async {
    await assertNoErrorsInCode(r'''
class C<E> {
  static T f<T>(T x) => null;
}
''');
    expectFunctionType('f', 'T Function<T>(T)', typeFormals: '[T]');
    SimpleIdentifier f = findNode.simple('f');
    var e = f.staticElement as MethodElementImpl;
    FunctionType ft = e.type.instantiate([typeProvider.stringType]);
    assertType(ft, 'String Function(String)');
  }

  test_genericFunction_typedef() async {
    String code = r'''
typedef T F<T>(T x);
F f0;

class C {
  static F f1;
  F f2;
  void g(F f3) { // C
    F f4;
    f0(3);
    f1(3);
    f2(3);
    f3(3);
    f4(3);
  }
}

class D<S> {
  static F f1;
  F f2;
  void g(F f3) { // D
    F f4;
    f0(3);
    f1(3);
    f2(3);
    f3(3);
    f4(3);
  }
}
''';
    await assertNoErrorsInCode(code);

    checkBody(String className) {
      var statements = findNode.block('{ // $className').statements;

      for (int i = 1; i <= 5; i++) {
        Expression exp = (statements[i] as ExpressionStatement).expression;
        expect(exp.staticType, typeProvider.dynamicType);
      }
    }

    checkBody("C");
    checkBody("D");
  }

  test_genericFunction_upwardsAndDownwards() async {
    // Regression tests for https://github.com/dart-lang/sdk/issues/27586.
    await assertNoErrorsInCode(r'List<num> x = [1, 2];');
    expectInitializerType('x', 'List<num>');
  }

  test_genericFunction_upwardsAndDownwards_Object() async {
    // Regression tests for https://github.com/dart-lang/sdk/issues/27625.
    await assertNoErrorsInCode(r'''
List<Object> aaa = [];
List<Object> bbb = [1, 2, 3];
List<Object> ccc = [null];
List<Object> ddd = [1 as dynamic];
List<Object> eee = [new Object()];
    ''');
    expectInitializerType('aaa', 'List<Object>');
    expectInitializerType('bbb', 'List<Object>');
    expectInitializerType('ccc', 'List<Object>');
    expectInitializerType('ddd', 'List<Object>');
    expectInitializerType('eee', 'List<Object>');
  }

  test_genericMethod() async {
    await assertErrorsInCode(r'''
class C<E> {
  List<T> f<T>(E e) => null;
}
main() {
  C<String> cOfString;
}
''', [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 65, 9),
    ]);
    assertType(findElement.method('f').type, 'List<T> Function<T>(E)');

    var cOfString = findElement.localVar('cOfString');
    var ft = (cOfString.type as InterfaceType).getMethod('f')!.type;
    assertType(ft, 'List<T> Function<T>(String)');
    assertType(
        ft.instantiate([typeProvider.intType]), 'List<int> Function(String)');
  }

  test_genericMethod_explicitTypeParams() async {
    await assertErrorsInCode(r'''
class C<E> {
  List<T> f<T>(E e) => null;
}
main() {
  C<String> cOfString;
  var x = cOfString.f<int>('hi');
}
''', [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 82, 1),
    ]);
    var f = findNode.simple('f<int>').parent as MethodInvocation;
    var ft = f.staticInvokeType as FunctionType;
    assertType(ft, 'List<int> Function(String)');

    var x = findElement.localVar('x');
    expect(x.type, typeProvider.listType(typeProvider.intType));
  }

  test_genericMethod_functionExpressionInvocation_explicit() async {
    await assertErrorsInCode(r'''
class C<E> {
  T f<T>(T e) => null;
  static T g<T>(T e) => null;
  static T Function<T>(T) h = null;
}

T topF<T>(T e) => null;
var topG = topF;
void test<S>(T Function<T>(T) pf) {
  var c = new C<int>();
  T lf<T>(T e) => null;

  var lambdaCall = (<E>(E e) => e)<int>(3);
  var methodCall = (c.f)<int>(3);
  var staticCall = (C.g)<int>(3);
  var staticFieldCall = (C.h)<int>(3);
  var topFunCall = (topF)<int>(3);
  var topFieldCall = (topG)<int>(3);
  var localCall = (lf)<int>(3);
  var paramCall = (pf)<int>(3);
}
''', [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 237, 10),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 281, 10),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 315, 10),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 349, 15),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 388, 10),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 423, 12),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 460, 9),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 492, 9),
    ]);
    _assertLocalVarType('lambdaCall', "int");
    _assertLocalVarType('methodCall', "int");
    _assertLocalVarType('staticCall', "int");
    _assertLocalVarType('staticFieldCall', "int");
    _assertLocalVarType('topFunCall', "int");
    _assertLocalVarType('topFieldCall', "int");
    _assertLocalVarType('localCall', "int");
    _assertLocalVarType('paramCall', "int");
  }

  test_genericMethod_functionExpressionInvocation_functionTypedParameter_explicit() async {
    await assertErrorsInCode(r'''
void test<S>(T pf<T>(T e)) {
  var paramCall = (pf)<int>(3);
}
''', [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 35, 9),
    ]);
    _assertLocalVarType('paramCall', "int");
  }

  test_genericMethod_functionExpressionInvocation_functionTypedParameter_inferred() async {
    await assertErrorsInCode(r'''
void test<S>(T pf<T>(T e)) {
  var paramCall = (pf)(3);
}
''', [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 35, 9),
    ]);
    _assertLocalVarType('paramCall', "int");
  }

  test_genericMethod_functionExpressionInvocation_inferred() async {
    await assertErrorsInCode(r'''
class C<E> {
  T f<T>(T e) => null;
  static T g<T>(T e) => null;
  static T Function<T>(T) h = null;
}

T topF<T>(T e) => null;
var topG = topF;
void test<S>(T Function<T>(T) pf) {
  var c = new C<int>();
  T lf<T>(T e) => null;

  var lambdaCall = (<E>(E e) => e)(3);
  var methodCall = (c.f)(3);
  var staticCall = (C.g)(3);
  var staticFieldCall = (C.h)(3);
  var topFunCall = (topF)(3);
  var topFieldCall = (topG)(3);
  var localCall = (lf)(3);
  var paramCall = (pf)(3);
}
''', [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 237, 10),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 276, 10),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 305, 10),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 334, 15),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 368, 10),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 398, 12),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 430, 9),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 457, 9),
    ]);
    _assertLocalVarType('lambdaCall', "int");
    _assertLocalVarType('methodCall', "int");
    _assertLocalVarType('staticCall', "int");
    _assertLocalVarType('staticFieldCall', "int");
    _assertLocalVarType('topFunCall', "int");
    _assertLocalVarType('topFieldCall', "int");
    _assertLocalVarType('localCall', "int");
    _assertLocalVarType('paramCall', "int");
  }

  test_genericMethod_functionInvocation_explicit() async {
    await assertErrorsInCode(r'''
class C<E> {
  T f<T>(T e) => null;
  static T g<T>(T e) => null;
  static T Function<T>(T) h = null;
}

T topF<T>(T e) => null;
var topG = topF;
void test<S>(T Function<T>(T) pf) {
  var c = new C<int>();
  T lf<T>(T e) => null;
  var methodCall = c.f<int>(3);
  var staticCall = C.g<int>(3);
  var staticFieldCall = C.h<int>(3);
  var topFunCall = topF<int>(3);
  var topFieldCall = topG<int>(3);
  var localCall = lf<int>(3);
  var paramCall = pf<int>(3);
}
''', [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 236, 10),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 268, 10),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 300, 15),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 337, 10),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 370, 12),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 405, 9),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 435, 9),
    ]);
    _assertLocalVarType('methodCall', "int");
    _assertLocalVarType('staticCall', "int");
    _assertLocalVarType('staticFieldCall', "int");
    _assertLocalVarType('topFunCall', "int");
    _assertLocalVarType('topFieldCall', "int");
    _assertLocalVarType('localCall', "int");
    _assertLocalVarType('paramCall', "int");
  }

  test_genericMethod_functionInvocation_functionTypedParameter_explicit() async {
    await assertErrorsInCode(r'''
void test<S>(T pf<T>(T e)) {
  var paramCall = pf<int>(3);
}
''', [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 35, 9),
    ]);
    _assertLocalVarType('paramCall', "int");
  }

  test_genericMethod_functionInvocation_functionTypedParameter_inferred() async {
    await assertErrorsInCode(r'''
void test<S>(T pf<T>(T e)) {
  var paramCall = pf(3);
}
''', [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 35, 9),
    ]);
    _assertLocalVarType('paramCall', "int");
  }

  test_genericMethod_functionInvocation_inferred() async {
    await assertErrorsInCode(r'''
class C<E> {
  T f<T>(T e) => null;
  static T g<T>(T e) => null;
  static T Function<T>(T) h = null;
}

T topF<T>(T e) => null;
var topG = topF;
void test<S>(T Function<T>(T) pf) {
  var c = new C<int>();
  T lf<T>(T e) => null;
  var methodCall = c.f(3);
  var staticCall = C.g(3);
  var staticFieldCall = C.h(3);
  var topFunCall = topF(3);
  var topFieldCall = topG(3);
  var localCall = lf(3);
  var paramCall = pf(3);
}
''', [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 236, 10),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 263, 10),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 290, 15),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 322, 10),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 350, 12),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 380, 9),
      error(HintCode.UNUSED_LOCAL_VARIABLE, 405, 9),
    ]);
    _assertLocalVarType('methodCall', "int");
    _assertLocalVarType('staticCall', "int");
    _assertLocalVarType('staticFieldCall', "int");
    _assertLocalVarType('topFunCall', "int");
    _assertLocalVarType('topFieldCall', "int");
    _assertLocalVarType('localCall', "int");
    _assertLocalVarType('paramCall', "int");
  }

  test_genericMethod_functionTypedParameter() async {
    await assertErrorsInCode(r'''
class C<E> {
  List<T> f<T>(T f(E e)) => null;
}
main() {
  C<String> cOfString;
}
''', [
      error(HintCode.UNUSED_LOCAL_VARIABLE, 70, 9),
    ]);
    assertType(
        findElement.method('f').type, 'List<T> Function<T>(T Function(E))');

    var cOfString = findElement.localVar('cOfString');
    var ft = (cOfString.type as InterfaceType).getMethod('f')!.type;
    assertType(ft, 'List<T> Function<T>(T Function(String))');
    assertType(ft.instantiate([typeProvider.int