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 'dart:async';

import 'package:analyzer/dart/ast/ast.dart';
import 'package:analyzer/dart/ast/standard_resolution_map.dart';
import 'package:analyzer/dart/element/element.dart';
import 'package:analyzer/dart/element/type.dart';
import 'package:analyzer/src/dart/element/element.dart';
import 'package:analyzer/src/error/codes.dart';
import 'package:analyzer/src/generated/engine.dart';
import 'package:analyzer/src/generated/source_io.dart';
import 'package:analyzer/src/task/strong/ast_properties.dart';
import 'package:front_end/src/base/errors.dart';
import 'package:test/test.dart';
import 'package:test_reflective_loader/test_reflective_loader.dart';

import '../utils.dart';
import 'resolver_test_case.dart';

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

/**
 * Strong mode static analyzer local type inference tests
 */
@reflectiveTest
class StrongModeLocalInferenceTest extends ResolverTestCase {
  TypeAssertions _assertions;

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

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

  AsserterBuilder<Element, DartType> _hasElement;
  AsserterBuilder<DartType, DartType> _hasElementOf;

  @override
  Future<TestAnalysisResult> computeAnalysisResult(Source source) async {
    TestAnalysisResult result = await super.computeAnalysisResult(source);
    if (_assertions == null) {
      _assertions = new 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;
      _hasElementOf = _assertions.hasElementOf;
      _isFutureOf = _isInstantiationOf(_hasElementOf(typeProvider.futureType));
      _isFutureOrOf =
          _isInstantiationOf(_hasElementOf(typeProvider.futureOrType));
      _isFutureOfDynamic = _isFutureOf([_isDynamic]);
      _isFutureOfInt = _isFutureOf([_isInt]);
      _isFutureOfNull = _isFutureOf([_isNull]);
      _isFutureOrOfInt = _isFutureOrOf([_isInt]);
      _isStreamOf = _isInstantiationOf(_hasElementOf(typeProvider.streamType));
    }
    return result;
  }

  @override
  void setUp() {
    super.setUp();
    AnalysisOptionsImpl options = new AnalysisOptionsImpl();
    options.strongMode = true;
    resetWith(options: options);
  }

  test_async_method_propagation() async {
    String code = r'''
      import "dart:async";
      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); }
      }
   ''';
    CompilationUnit unit = await resolveSource(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 {
        ReturnStatement stmt = (body as BlockFunctionBody).block.statements[0];
        returnExp = stmt.expression;
      }
      DartType type = returnExp.staticType;
      if (returnExp is AwaitExpression) {
        type = returnExp.expression.staticType;
      }
      typeTest(type);
    }

    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'''
      import "dart:async";

      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); }
   ''';
    CompilationUnit unit = await resolveSource(code);

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

    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_star_method_propagation() async {
    String code = r'''
      import "dart:async";
      class A {
        Stream g0() async* { yield []; }
        Stream g1() async* { yield* new Stream(); }

        Stream<List<int>> g2() async* { yield []; }
        Stream<List<int>> g3() async* { yield* new Stream(); }
      }
    ''';
    CompilationUnit unit = await resolveSource(code);

    void check(String name, Asserter<InterfaceType> typeTest) {
      MethodDeclaration test = AstFinder.getMethodInClass(unit, "A", name);
      BlockFunctionBody body = test.body;
      YieldStatement stmt = body.block.statements[0];
      Expression exp = stmt.expression;
      typeTest(exp.staticType);
    }

    check("g0", _isListOf(_isDynamic));
    check("g1", _isStreamOf([_isDynamic]));

    check("g2", _isListOf(_isInt));
    check("g3", _isStreamOf([(DartType type) => _isListOf(_isInt)(type)]));
  }

  test_async_star_propagation() async {
    String code = r'''
      import "dart:async";

      Stream g0() async* { yield []; }
      Stream g1() async* { yield* new Stream(); }

      Stream<List<int>> g2() async* { yield []; }
      Stream<List<int>> g3() async* { yield* new Stream(); }
   ''';
    CompilationUnit unit = await resolveSource(code);

    void check(String name, Asserter<InterfaceType> typeTest) {
      FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, name);
      BlockFunctionBody body = test.functionExpression.body;
      YieldStatement stmt = body.block.statements[0];
      Expression exp = stmt.expression;
      typeTest(exp.staticType);
    }

    check("g0", _isListOf(_isDynamic));
    check("g1", _isStreamOf([_isDynamic]));

    check("g2", _isListOf(_isInt));
    check("g3", _isStreamOf([(DartType type) => _isListOf(_isInt)(type)]));
  }

  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]);
     }
   ''';
    CompilationUnit unit = await resolveSource(code);
    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    CascadeExpression fetch(int i) {
      VariableDeclarationStatement stmt = statements[i];
      VariableDeclaration decl = stmt.variables.variables[0];
      CascadeExpression exp = decl.initializer;
      return exp;
    }

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

    CascadeExpression cascade = fetch(0);
    _isInstantiationOf(_hasElement(elementA))([_isInt])(cascade.staticType);
    MethodInvocation invoke = cascade.cascadeSections[0];
    FunctionExpression function = invoke.argumentList.arguments[1];
    ExecutableElement f0 = function.element;
    _isListOf(_isInt)(f0.type.returnType);
    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); }
   ''';
    Source source = addSource(code);
    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
    assertNoErrors(source);
    verify([source]);
    CompilationUnit unit = analysisResult.unit;
    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "test");
    VariableDeclarationStatement stmt = statements[0];
    VariableDeclaration decl = stmt.variables.variables[0];
    Expression call = decl.initializer;
    _isInt(call.staticType);
  }

  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); }
   ''';
    Source source = addSource(code);
    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
    assertNoErrors(source);
    verify([source]);
    CompilationUnit unit = analysisResult.unit;
    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "test");
    VariableDeclarationStatement stmt = statements[0];
    VariableDeclaration decl = stmt.variables.variables[0];
    Expression call = decl.initializer;
    _isInt(call.staticType);
  }

  test_constrainedByBounds3() async {
    Source source = addSource(r'''
      T f<T extends S, S extends int>(S x) => null;
      void test() { var x = f(3); }
   ''');
    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
    assertNoErrors(source);
    verify([source]);
    CompilationUnit unit = analysisResult.unit;
    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "test");
    VariableDeclarationStatement stmt = statements[0];
    VariableDeclaration decl = stmt.variables.variables[0];
    Expression call = decl.initializer;
    _isInt(call.staticType);
  }

  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); }
   ''';
    Source source = addSource(code);
    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
    assertNoErrors(source);
    verify([source]);
    CompilationUnit unit = analysisResult.unit;
    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "test");
    VariableDeclarationStatement stmt = statements[0];
    VariableDeclaration decl = stmt.variables.variables[0];
    Expression call = decl.initializer;
    _isInt(call.staticType);
  }

  test_constrainedByBounds5() async {
    // Test that upwards inference with two type variables does not
    // propogate 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); }
   ''';
    Source source = addSource(code);
    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
    assertErrors(source, [StrongModeCode.COULD_NOT_INFER]);
    verify([source]);
    CompilationUnit unit = analysisResult.unit;
    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "test");
    VariableDeclarationStatement stmt = statements[0];
    VariableDeclaration decl = stmt.variables.variables[0];
    Expression call = decl.initializer;
    _isDynamic(call.staticType);
  }

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

  test_covarianceChecks() async {
    var source = addSource(r'''
class C<T> {
  add(T t) {}
  forEach(void f(T t)) {}
}
class D extends C<int> {
  add(int t) {}
  forEach(void f(int t)) {}
}
class E extends C<int> {
  add(Object t) {}
  forEach(void f(Null t)) {}
}
''');
    var unit = (await computeAnalysisResult(source)).unit;
    assertNoErrors(source);
    var cAdd = AstFinder.getMethodInClass(unit, "C", "add");
    var covariantC = getClassCovariantParameters(AstFinder.getClass(unit, "C"));
    expect(covariantC.toList(), [cAdd.element.parameters[0]]);

    var dAdd = AstFinder.getMethodInClass(unit, "D", "add");
    var covariantD = getClassCovariantParameters(AstFinder.getClass(unit, "D"));
    expect(covariantD.toList(), [dAdd.element.parameters[0]]);

    var covariantE = getClassCovariantParameters(AstFinder.getClass(unit, "E"));
    expect(covariantE.toList(), []);
  }

  test_covarianceChecks_genericMethods() async {
    var source = addSource(r'''
class C<T> {
  add<S>(T t) {}
  forEach<S>(S f(T t)) {}
}
class D extends C<int> {
  add<S>(int t) {}
  forEach<S>(S f(int t)) {}
}
class E extends C<int> {
  add<S>(Object t) {}
  forEach<S>(S f(Null t)) {}
}
''');
    var unit = (await computeAnalysisResult(source)).unit;
    assertNoErrors(source);

    var cAdd = AstFinder.getMethodInClass(unit, "C", "add");
    var covariantC = getClassCovariantParameters(AstFinder.getClass(unit, "C"));
    expect(covariantC.toList(), [cAdd.element.parameters[0]]);

    var dAdd = AstFinder.getMethodInClass(unit, "D", "add");
    var covariantD = getClassCovariantParameters(AstFinder.getClass(unit, "D"));
    expect(covariantD.toList(), [dAdd.element.parameters[0]]);

    var covariantE = getClassCovariantParameters(AstFinder.getClass(unit, "E"));
    expect(covariantE.toList(), []);
  }

  test_covarianceChecks_returnFunction() async {
    var source = addSource(r'''
typedef F<T>(T t);
typedef T R<T>();
class C<T> {
  F<T> f;

  C();
  factory C.fact() => new C<Null>();

  F<T> get g => null;
  F<T> m1() => null;
  R<F<T>> m2() => null;

  casts(C<T> other, T t) {
    other.f;
    other.g(t);
    other.m1();
    other.m2;

    new C<T>.fact().f(t);
    new C<int>.fact().g;
    new C<int>.fact().m1;
    new C<T>.fact().m2();

    new C<Object>.fact().f(42);
    new C<Object>.fact().g;
    new C<Object>.fact().m1;
    new C<Object>.fact().m2();

    new C.fact().f(42);
    new C.fact().g;
    new C.fact().m1;
    new C.fact().m2();
  }

  noCasts(T t) {
    f;
    g;
    m1();
    m2();

    f(t);
    g(t);
    (f)(t);
    (g)(t);
    m1;
    m2;

    this.f;
    this.g;
    this.m1();
    this.m2();
    this.m1;
    this.m2;
    (this.m1)();
    (this.m2)();
    this.f(t);
    this.g(t);
    (this.f)(t);
    (this.g)(t);

    new C<int>().f;
    new C<T>().g;
    new C<int>().m1();
    new C().m2();

    new D().f;
    new D().g;
    new D().m1();
    new D().m2();
  }
}
class D extends C<num> {
  noCasts(t) {
    f;
    this.g;
    this.m1();
    m2;

    super.f;
    super.g;
    super.m1;
    super.m2();
  }
}

D d;
C<Object> c;
C cD;
C<Null> cN;
F<Object> f;
F<Null> fN;
R<F<Object>> rf;
R<F<Null>> rfN;
R<R<F<Object>>> rrf;
R<R<F<Null>>> rrfN;
Object obj;
F<int> fi;
R<F<int>> rfi;
R<R<F<int>>> rrfi;

casts() {
  c.f;
  c.g;
  c.m1;
  c.m1();
  c.m2();

  fN = c.f;
  fN = c.g;
  rfN = c.m1;
  rrfN = c.m2;
  fN = c.m1();
  rfN = c.m2();

  f = c.f;
  f = c.g;
  rf = c.m1;
  rrf = c.m2;
  f = c.m1();
  rf = c.m2();
  c.m2()();

  c.f(obj);
  c.g(obj);
  (c.f)(obj);
  (c.g)(obj);
  (c.m1)();
  c.m1()(obj);
  (c.m2)();

  cD.f;
  cD.g;
  cD.m1;
  cD.m1();
  cD.m2();
}

noCasts() {
  fi = d.f;
  fi = d.g;
  rfi = d.m1;
  fi = d.m1();
  rrfi = d.m2;
  rfi = d.m2();
  d.f(42);
  d.g(42);
  (d.f)(42);
  (d.g)(42);
  d.m1()(42);
  d.m2()()(42);

  cN.f;
  cN.g;
  cN.m1;
  cN.m1();
  cN.m2();
}
''');
    var unit = (await computeAnalysisResult(source)).unit;
    assertNoErrors(source);

    void expectCast(Statement statement, bool hasCast) {
      var value = (statement as ExpressionStatement).expression;
      if (value is AssignmentExpression) {
        value = (value as AssignmentExpression).rightHandSide;
      }
      while (value is FunctionExpressionInvocation) {
        value = (value as FunctionExpressionInvocation).function;
      }
      while (value is ParenthesizedExpression) {
        value = (value as ParenthesizedExpression).expression;
      }
      var isCallingGetter =
          value is MethodInvocation && !value.methodName.name.startsWith('m');
      var cast = isCallingGetter
          ? getImplicitOperationCast(value)
          : getImplicitCast(value);
      var castKind = isCallingGetter ? 'special cast' : 'cast';
      expect(cast, hasCast ? isNotNull : isNull,
          reason: '`$statement` should ' +
              (hasCast ? '' : 'not ') +
              'have a $castKind on `$value`.');
    }

    for (var s in AstFinder.getStatementsInMethod(unit, 'C', 'noCasts')) {
      expectCast(s, false);
    }
    for (var s in AstFinder.getStatementsInMethod(unit, 'C', 'casts')) {
      expectCast(s, true);
    }
    for (var s in AstFinder.getStatementsInMethod(unit, 'D', 'noCasts')) {
      expectCast(s, false);
    }
    for (var s in AstFinder.getStatementsInTopLevelFunction(unit, 'noCasts')) {
      expectCast(s, false);
    }
    for (var s in AstFinder.getStatementsInTopLevelFunction(unit, 'casts')) {
      expectCast(s, true);
    }
  }

  test_covarianceChecks_superclass() async {
    var source = addSource(r'''
class C<T> {
  add(T t) {}
  forEach(void f(T t)) {}
}
class D {
  add(int t) {}
  forEach(void f(int t)) {}
}
class E extends D implements C<int> {}
''');
    var unit = (await computeAnalysisResult(source)).unit;
    assertNoErrors(source);
    var cAdd = AstFinder.getMethodInClass(unit, "C", "add");
    var covariantC = getClassCovariantParameters(AstFinder.getClass(unit, "C"));
    expect(covariantC.toList(), [cAdd.element.parameters[0]]);

    var dAdd = AstFinder.getMethodInClass(unit, "D", "add");
    var covariantD = getClassCovariantParameters(AstFinder.getClass(unit, "D"));
    expect(covariantD, null);

    var classE = AstFinder.getClass(unit, "E");
    var covariantE = getClassCovariantParameters(classE);
    var superCovariantE = getSuperclassCovariantParameters(classE);
    expect(covariantE.toList(), []);
    expect(superCovariantE.toList(), [dAdd.element.parameters[0]]);
  }

  test_factoryConstructor_propagation() async {
    String code = r'''
      class A<T> {
        factory A() { return new B(); }
      }
      class B<S> extends A<S> {}
   ''';
    CompilationUnit unit = await resolveSource(code);

    ConstructorDeclaration constructor =
        AstFinder.getConstructorInClass(unit, "A", null);
    BlockFunctionBody body = constructor.body;
    ReturnStatement stmt = body.block.statements[0];
    InstanceCreationExpression exp = stmt.expression;
    ClassElement elementB = AstFinder.getClass(unit, "B").element;
    ClassElement elementA = AstFinder.getClass(unit, "A").element;
    expect(resolutionMap.typeForTypeName(exp.constructorName.type).element,
        elementB);
    _isInstantiationOf(_hasElement(elementB))(
        [_isType(elementA.typeParameters[0].type)])(exp.staticType);
  }

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

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

    _isListOf(_isString)(field.initializer.staticType);
  }

  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;
     }
   ''';
    CompilationUnit unit = await resolveSource(code);

    Asserter<InterfaceType> assertListOfInt = _isListOf(_isInt);

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

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

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

    FunctionExpression anon1 = (statements[1] as ReturnStatement).expression;
    FunctionType type1 =
        resolutionMap.elementDeclaredByFunctionExpression(anon1).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;};
     }
   ''';
    CompilationUnit unit = await resolveSource(code);
    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    DartType literal(int i) {
      VariableDeclarationStatement stmt = statements[i];
      VariableDeclaration decl = stmt.variables.variables[0];
      FunctionExpression exp = decl.initializer;
      return resolutionMap.elementDeclaredByFunctionExpression(exp).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;};
     }
   ''';
    CompilationUnit unit = await resolveSource(code);
    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    DartType literal(int i) {
      VariableDeclarationStatement stmt = statements[i];
      VariableDeclaration decl = stmt.variables.variables[0];
      FunctionExpression exp = decl.initializer;
      return resolutionMap.elementDeclaredByFunctionExpression(exp).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];};
     }
   ''';
    CompilationUnit unit = await resolveSource(code);
    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    Expression functionReturnValue(int i) {
      VariableDeclarationStatement stmt = statements[i];
      VariableDeclaration decl = stmt.variables.variables[0];
      FunctionExpression exp = decl.initializer;
      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);
    assertListOfString(functionReturnValue(1).staticType);
    assertListOfString(functionReturnValue(2).staticType);
    assertListOfString(functionReturnValue(3).staticType);
  }

  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;});
     }
   ''';
    CompilationUnit unit = await resolveSource(code);
    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    DartType literal(int i) {
      ExpressionStatement stmt = statements[i];
      FunctionExpressionInvocation invk = stmt.expression;
      FunctionExpression exp = invk.argumentList.arguments[0];
      return resolutionMap.elementDeclaredByFunctionExpression(exp).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;});
     }
   ''';
    CompilationUnit unit = await resolveSource(code);
    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    DartType literal(int i) {
      ExpressionStatement stmt = statements[i];
      FunctionExpressionInvocation invk = stmt.expression;
      FunctionExpression exp = invk.argumentList.arguments[0];
      return resolutionMap.elementDeclaredByFunctionExpression(exp).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;});
     }
   ''';
    CompilationUnit unit = await resolveSource(code);
    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    DartType literal(int i) {
      ExpressionStatement stmt = statements[i];
      MethodInvocation invk = stmt.expression;
      FunctionExpression exp = invk.argumentList.arguments[0];
      return resolutionMap.elementDeclaredByFunctionExpression(exp).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;});
     }
   ''';
    CompilationUnit unit = await resolveSource(code);
    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    DartType literal(int i) {
      ExpressionStatement stmt = statements[i];
      MethodInvocation invk = stmt.expression;
      FunctionExpression exp = invk.argumentList.arguments[0];
      return resolutionMap.elementDeclaredByFunctionExpression(exp).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;});
     }
   ''';
    CompilationUnit unit = await resolveSource(code);
    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    DartType literal(int i) {
      ExpressionStatement stmt = statements[i];
      MethodInvocation invk = stmt.expression;
      FunctionExpression exp = invk.argumentList.arguments[0];
      return resolutionMap.elementDeclaredByFunctionExpression(exp).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;});
     }
   ''';
    CompilationUnit unit = await resolveSource(code);
    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    DartType literal(int i) {
      ExpressionStatement stmt = statements[i];
      MethodInvocation invk = stmt.expression;
      FunctionExpression exp = invk.argumentList.arguments[0];
      return resolutionMap.elementDeclaredByFunctionExpression(exp).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();
     }
   ''';
    CompilationUnit unit = await resolveSource(code);
    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    Expression functionReturnValue(int i) {
      VariableDeclarationStatement stmt = statements[i];
      VariableDeclaration decl = stmt.variables.variables[0];
      FunctionExpression exp = decl.initializer;
      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);
  }

  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);
  }

  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);
  }

  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);
  }

  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);
  }

  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);
  }

  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);
  }

  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);
    _isFutureOfInt(invoke.argumentList.arguments[0].staticType);
  }

  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);
    _isFutureOfInt(invoke.argumentList.arguments[0].staticType);
  }

  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);
    _isFutureOf([_isNum])(invoke.argumentList.arguments[0].staticType);
  }

  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);
    _isFutureOfInt(invoke.argumentList.arguments[0].staticType);
  }

  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);
    _isFutureOfInt(invoke.argumentList.arguments[0].staticType);
  }

  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);
    _isFutureOfInt(invoke.argumentList.arguments[0].staticType);
  }

  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);
    _isInt(invoke.argumentList.arguments[0].staticType);
  }

  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.staticType);
  }

  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();
    ''', errors: [StaticTypeWarningCode.UNDEFINED_METHOD]);
    _isDynamic(invoke.staticType);
  }

  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);
    ''', errors: [StaticTypeWarningCode.UNDEFINED_METHOD]);
    _isDynamic(invoke.staticType);
  }

  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();
    ''', errors: [StaticTypeWarningCode.UNDEFINED_METHOD]);
    _isDynamic(invoke.staticType);
  }

  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].staticType);
    _isFutureOfNull(invoke.staticType);
  }

  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].staticType);
    _isFutureOfNull(invoke.staticType);
  }

  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].staticType);
    _isFutureOfNull(invoke.staticType);
  }

  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);
  }

  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));
    ''', errors: [StrongModeCode.COULD_NOT_INFER]);
    _isFutureOfInt(invoke.staticType);
  }

  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].staticType);
    _isFutureOfNull(invoke.staticType);
  }

  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].staticType);
    _isFutureOfNull(invoke.staticType);
  }

  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].staticType);
    _isFutureOfNull(invoke.staticType);
  }

  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));
}
   ''';
    CompilationUnit unit = await resolveSource(code);
    Element elementA = AstFinder.getClass(unit, "A").element;
    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "test");
    void check(int i) {
      VariableDeclarationStatement stmt = statements[i];
      VariableDeclaration decl = stmt.variables.variables[0];
      Expression init = decl.initializer;
      _isInstantiationOf(_hasElement(elementA))([_isInt])(init.staticType);
    }

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

  test_inferConstructor_unknownTypeLowerBound() async {
    Source source = addSource(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) {});
        }
        ''');
    CompilationUnit unit = (await computeAnalysisResult(source)).unit;
    assertNoErrors(source);
    verify([source]);
    DartType cType = findLocalVariable(unit, 'c').type;
    Element elementC = AstFinder.getClass(unit, "C").element;

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

  test_inference_error_arguments() async {
    Source source = addSource(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 computeAnalysisResult(source);
    _expectInferenceError(source, [
      StrongModeCode.COULD_NOT_INFER,
      StaticWarningCode.ARGUMENT_TYPE_NOT_ASSIGNABLE
    ], r'''
Couldn't infer type parameter 'T'.

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

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

''');
  }

  test_inference_error_arguments2() async {
    Source source = addSource(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 computeAnalysisResult(source);
    _expectInferenceError(source, [
      StrongModeCode.COULD_NOT_INFER,
      StaticWarningCode.ARGUMENT_TYPE_NOT_ASSIGNABLE,
      StaticWarningCode.ARGUMENT_TYPE_NOT_ASSIGNABLE
    ], r'''
Couldn't infer type parameter 'T'.

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

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.
    Source source = addSource(r'''
T max<T extends num>(T x, T y) => x;

test() {
  String hello = max(1, 2);
}
 ''');
    var analysisResult = await computeAnalysisResult(source);
    assertErrors(source, [
      StrongModeCode.INVALID_CAST_LITERAL,
      StrongModeCode.INVALID_CAST_LITERAL
    ]);
    var unit = analysisResult.unit;
    var h = (AstFinder.getStatementsInTopLevelFunction(unit, "test")[0]
            as VariableDeclarationStatement)
        .variables
        .variables[0];
    var call = h.initializer as MethodInvocation;
    expect(call.staticInvokeType.toString(), '(Null, Null) → Null');
  }

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

test() {
  F<String, String> hello = g();
}
 ''');
    await computeAnalysisResult(source);
    _expectInferenceError(source, [
      StrongModeCode.COULD_NOT_INFER,
    ], r'''
Couldn't infer type parameter 'T'.

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

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

''');
  }

  test_inference_error_genericFunction() async {
    Source source = addSource(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 computeAnalysisResult(source);
    _expectInferenceError(source, [
      StrongModeCode.COULD_NOT_INFER,
      StaticWarningCode.ARGUMENT_TYPE_NOT_ASSIGNABLE
    ], r'''
Couldn't infer type parameter 'T'.

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

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

''');
  }

  test_inference_error_returnContext() async {
    Source source = addSource(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 computeAnalysisResult(source);
    _expectInferenceError(source, [StrongModeCode.COULD_NOT_INFER], r'''
Couldn't infer type parameter 'T'.

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

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

''');
  }

  test_inference_hints() async {
    Source source = addSource(r'''
      void main () {
        var x = 3;
        List<int> l0 = [];
     }
   ''');
    await computeAnalysisResult(source);
    assertNoErrors(source);
    verify([source]);
  }

  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 source = addSource(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);
}
    ''');
    var analysisResult = await computeAnalysisResult(source);
    assertNoErrors(source);
    verify([source]);
    var unit = analysisResult.unit;
    var body = (AstFinder
        .getTopLevelFunction(unit, '_mergeSort')
        .functionExpression
        .body as BlockFunctionBody);
    var stmts = body.block.statements;
    for (ExpressionStatement stmt in stmts) {
      MethodInvocation invoke = stmt.expression;
      ParameterizedType fType = invoke.staticInvokeType;
      expect(fType.typeArguments[0].toString(), '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 source = addSource(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);
}
    ''');
    var analysisResult = await computeAnalysisResult(source);
    assertNoErrors(source);
    verify([source]);
    var unit = analysisResult.unit;
    var body = (AstFinder
        .getTopLevelFunction(unit, '_mergeSort')
        .functionExpression
        .body as BlockFunctionBody);
    var stmts = body.block.statements;
    for (ExpressionStatement stmt in stmts) {
      MethodInvocation invoke = stmt.expression;
      ParameterizedType fType = invoke.staticInvokeType;
      expect(fType.typeArguments[0].toString(), '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 source = addSource(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);
}
    ''');
    var analysisResult = await computeAnalysisResult(source);
    assertNoErrors(source);
    verify([source]);
    var unit = analysisResult.unit;
    var body = (AstFinder
        .getTopLevelFunction(unit, '_mergeSort')
        .functionExpression
        .body as BlockFunctionBody);
    var stmts = body.block.statements;
    for (ExpressionStatement stmt in stmts) {
      MethodInvocation invoke = stmt.expression;
      ParameterizedType fType = invoke.staticInvokeType;
      expect(fType.typeArguments[0].toString(), 'T');
    }
  }

  test_inferGenericInstantiation() async {
    // Verify that we don't infer '?` when we instantiate a generic function.
    var source = addSource(r'''
T f<T>(T x(T t)) => x(null);
S g<S>(S s) => s;
test() {
 var h = f(g);
}
    ''');
    var analysisResult = await computeAnalysisResult(source);
    assertNoErrors(source);
    verify([source]);
    var unit = analysisResult.unit;
    var h = (AstFinder.getStatementsInTopLevelFunction(unit, "test")[0]
            as VariableDeclarationStatement)
        .variables
        .variables[0];
    _isDynamic(h.element.type);
    var fCall = h.initializer as MethodInvocation;
    expect(
        fCall.staticInvokeType.toString(), '((dynamic) → dynamic) → dynamic');
    var g = fCall.argumentList.arguments[0];
    expect(g.staticType.toString(), '(dynamic) → dynamic');
  }

  test_inferGenericInstantiation2() async {
    // Verify the behavior when we cannot infer an instantiation due to invalid
    // constraints from an outer generic method.
    var source = addSource(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);
    ''');
    var analysisResult = await computeAnalysisResult(source);
    assertErrors(source, [
      StrongModeCode.COULD_NOT_INFER,
      StaticWarningCode.ARGUMENT_TYPE_NOT_ASSIGNABLE
    ]);
    verify([source]);
    var unit = analysisResult.unit;
    var fold = (AstFinder
            .getTopLevelFunction(unit, 'test')
            .functionExpression
            .body as ExpressionFunctionBody)
        .expression as MethodInvocation;
    expect(
        fold.staticInvokeType.toString(), '(num, (num, dynamic) → num) → num');
    var max = fold.argumentList.arguments[1];
    // TODO(jmesserly): arguably (num, num) → num is better here.
    expect(max.staticType.toString(), '(dynamic, 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: [] };
      }
   ''';
    CompilationUnit unit = await resolveSource(code);

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

    VariableDeclaration mapB = AstFinder.getFieldInClass(unit, "B", "map");
    MethodDeclaration mapC = AstFinder.getMethodInClass(unit, "C", "map");
    assertMapOfIntToListOfInt(
        resolutionMap.elementDeclaredByVariableDeclaration(mapB).type);
    assertMapOfIntToListOfInt(
        resolutionMap.elementDeclaredByMethodDeclaration(mapC).returnType);

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

    ListLiteral listLiteralB = mapLiteralB.entries[0].value;
    ListLiteral listLiteralC = mapLiteralC.entries[0].value;
    assertListOfInt(listLiteralB.staticType);
    assertListOfInt(listLiteralC.staticType);
  }

  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");
      }''';
    CompilationUnit unit = await resolveSource(code);

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

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

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

    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");

      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");
      hasType(assertAOf([_isInt, _isString]), rhs(statements[0]));
      hasType(assertAOf([_isInt, _isString]), rhs(statements[1]));
    }

    {
      List<Statement> statements =
          AstFinder.getStatementsInTopLevelFunction(unit, "test2");
      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");
      hasType(assertBOf([_isString, _isInt]), rhs(statements[0]));
      hasType(assertBOf([_isString, _isInt]), rhs(statements[1]));
    }

    {
      List<Statement> statements =
          AstFinder.getStatementsInTopLevelFunction(unit, "test4");
      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");
      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");
      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");
      hasType(assertDOf([_isDynamic, _isString]), rhs(statements[0]));
      hasType(assertDOf([_isDynamic, _isString]), rhs(statements[1]));
    }

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

    {
      List<Statement> statements =
          AstFinder.getStatementsInTopLevelFunction(unit, "test9");
      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], []];
     }
   ''';
    CompilationUnit unit = await resolveSource(code);
    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    ListLiteral literal(int i) {
      VariableDeclarationStatement stmt = statements[i];
      VariableDeclaration decl = stmt.variables.variables[0];
      ListLiteral exp = decl.initializer;
      return exp;
    }

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

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

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

  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];
     }
   ''';
    CompilationUnit unit = await resolveSource(code);
    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    DartType literal(int i) {
      VariableDeclarationStatement stmt = statements[i];
      VariableDeclaration decl = stmt.variables.variables[0];
      ListLiteral exp = decl.initializer;
      return exp.staticType;
    }

    Asserter<InterfaceType> assertListOfInt = _isListOf(_isInt);

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

  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];
     }
   ''';
    CompilationUnit unit = await resolveSource(code);
    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    DartType literal(int i) {
      VariableDeclarationStatement stmt = statements[i];
      VariableDeclaration decl = stmt.variables.variables[0];
      ListLiteral exp = decl.initializer;
      return exp.staticType;
    }

    Asserter<InterfaceType> assertListOfInt = _isListOf(_isInt);

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

  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];
     }
   ''';
    CompilationUnit unit = await resolveSource(code);
    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    DartType literal(int i) {
      VariableDeclarationStatement stmt = statements[i];
      VariableDeclaration decl = stmt.variables.variables[0];
      ListLiteral exp = decl.initializer;
      return exp.staticType;
    }

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

  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];
     }
   ''';
    CompilationUnit unit = await resolveSource(code);
    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    DartType literal(int i) {
      VariableDeclarationStatement stmt = statements[i];
      VariableDeclaration decl = stmt.variables.variables[0];
      ListLiteral exp = decl.initializer;
      return exp.staticType;
    }

    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]};
     }
   ''';
    CompilationUnit unit = await resolveSource(code);
    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    MapLiteral literal(int i) {
      VariableDeclarationStatement stmt = statements[i];
      VariableDeclaration decl = stmt.variables.variables[0];
      MapLiteral exp = decl.initializer;
      return exp;
    }

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

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

    assertListOfString(literal(1).entries[0].value.staticType);
    assertListOfString(literal(2).entries[0].value.staticType);
    assertListOfString(literal(3).entries[0].value.staticType);
    assertListOfString(literal(4).entries[0].value.staticType);
  }

  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};
     }
   ''';
    CompilationUnit unit = await resolveSource(code);
    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    DartType literal(int i) {
      VariableDeclarationStatement stmt = statements[i];
      VariableDeclaration decl = stmt.variables.variables[0];
      MapLiteral exp = decl.initializer;
      return exp.staticType;
    }

    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};
     }
   ''';
    CompilationUnit unit = await resolveSource(code);
    List<Statement> statements =
        AstFinder.getStatementsInTopLevelFunction(unit, "main");
    DartType literal(int i) {
      VariableDeclarationStatement stmt = statements[i];
      VariableDeclaration decl = stmt.variables.variables[0];
      MapLiteral exp = decl.initializer;
      return exp.staticType;
    }

    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];}
      }
   ''';
    CompilationUnit unit = await resolveSource(code);
    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);
    assertListOfString(methodReturnValue("m1").staticType);
  }

  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);
   ''';
    Source source = addSource(code);
    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
    assertNoErrors(source);
    verify([source]);
    CompilationUnit unit = analysisResult.unit;
    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
    ExpressionFunctionBody body = test.functionExpression.body;
    _isString(body.expression.staticType);
    MethodInvocation invoke = body.expression;
    FunctionExpression function = invoke.argumentList.arguments[0];
    ExecutableElement f0 = function.element;
    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);
   ''';
    Source source = addSource(code);
    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
    assertErrors(source, [StrongModeCode.INVALID_CAST_LITERAL]);
    verify([source]);
    CompilationUnit unit = analysisResult.unit;
    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
    ExpressionFunctionBody body = test.functionExpression.body;
    DartType type = body.expression.staticType;

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

    _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);
   ''';
    Source source = addSource(code);
    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
    assertNoErrors(source);
    verify([source]);
    CompilationUnit unit = analysisResult.unit;
    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
    ExpressionFunctionBody body = test.functionExpression.body;
    DartType type = body.expression.staticType;

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

    _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);
   ''';
    Source source = addSource(code);
    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
    assertErrors(source, [
      StrongModeCode.INVALID_CAST_LITERAL,
    ]);
    verify([source]);
    CompilationUnit unit = analysisResult.unit;
    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
    ExpressionFunctionBody body = test.functionExpression.body;
    DartType type = body.expression.staticType;

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

    _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();
   ''';
    Source source = addSource(code);
    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
    assertNoErrors(source);
    verify([source]);
    CompilationUnit unit = analysisResult.unit;
    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
    ExpressionFunctionBody body = test.functionExpression.body;
    DartType type = body.expression.staticType;

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

    _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();
   ''';
    Source source = addSource(code);
    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
    assertNoErrors(source);
    verify([source]);
    CompilationUnit unit = analysisResult.unit;
    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
    ExpressionFunctionBody body = test.functionExpression.body;
    FunctionType functionType = body.expression.staticType;
    DartType type = functionType.normalParameterTypes[0];

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

    _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();
   ''';
    Source source = addSource(code);
    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
    assertNoErrors(source);
    verify([source]);
    CompilationUnit unit = analysisResult.unit;
    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
    ExpressionFunctionBody body = test.functionExpression.body;
    FunctionType functionType = body.expression.staticType;
    DartType type = functionType.normalParameterTypes[0];

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

    _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();
   ''';
    Source source = addSource(code);
    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
    assertNoErrors(source);
    verify([source]);
    CompilationUnit unit = analysisResult.unit;
    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
    ExpressionFunctionBody body = test.functionExpression.body;
    FunctionType functionType = body.expression.staticType;
    DartType type = functionType.normalParameterTypes[0];

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

    _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();
   ''';
    Source source = addSource(code);
    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
    assertNoErrors(source);
    verify([source]);
    CompilationUnit unit = analysisResult.unit;
    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
    ExpressionFunctionBody body = test.functionExpression.body;
    FunctionType functionType = body.expression.staticType;
    DartType type = functionType.normalParameterTypes[0];

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

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

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

class B<T2, U2> {
  factory B() = A.named;
}
   ''');
    TestAnalysisResult result = await computeAnalysisResult(source);
    assertNoErrors(source);

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

    TypeName typeName = redirected.type;
    expect(typeName.type.toString(), 'A<T2, U2>');
    expect(typeName.type.toString(), 'A<T2, U2>');

    var constructorMember = redirected.staticElement;
    expect(constructorMember.toString(), 'A.named() → A<T2, U2>');
    expect(redirected.name.staticElement, constructorMember);
  }

  test_redirectedConstructor_self() async {
    Source source = addSource(r'''
class A<T> {
  A();
  factory A.redirected() = A;
}
   ''');
    await computeAnalysisResult(source);
    assertNoErrors(source);
  }

  test_redirectedConstructor_unnamed() async {
    Source source = addSource(r'''
class A<T, U> implements B<T, U> {
  A();
}

class B<T2, U2> {
  factory B() = A;
}
   ''');
    TestAnalysisResult result = await computeAnalysisResult(source);
    assertNoErrors(source);

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

    TypeName typeName = redirected.type;
    expect(typeName.type.toString(), 'A<T2, U2>');
    expect(typeName.type.toString(), 'A<T2, U2>');

    expect(redirected.name, isNull);
    expect(redirected.staticElement.toString(), 'A() → A<T2, U2>');
  }

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

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

  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);
   ''';
    Source source = addSource(code);
    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
    assertNoErrors(source);
    verify([source]);
    CompilationUnit unit = analysisResult.unit;
    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
    ExpressionFunctionBody body = test.functionExpression.body;
    MethodInvocation invoke = body.expression;
    _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);
   ''';
    Source source = addSource(code);
    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
    assertNoErrors(source);
    verify([source]);
    CompilationUnit unit = analysisResult.unit;
    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
    ExpressionFunctionBody body = test.functionExpression.body;
    MethodInvocation invoke = body.expression;
    _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);
   ''';
    Source source = addSource(code);
    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
    assertNoErrors(source);
    verify([source]);
    CompilationUnit unit = analysisResult.unit;
    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
    ExpressionFunctionBody body = test.functionExpression.body;
    FunctionType functionType = body.expression.staticType;
    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);
   ''';
    Source source = addSource(code);
    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
    assertNoErrors(source);
    verify([source]);
    CompilationUnit unit = analysisResult.unit;
    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
    ExpressionFunctionBody body = test.functionExpression.body;
    FunctionType functionType = body.expression.staticType;
    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));
   ''';
    Source source = addSource(code);
    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
    assertNoErrors(source);
    verify([source]);
    CompilationUnit unit = analysisResult.unit;
    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
    ExpressionFunctionBody body = test.functionExpression.body;
    MethodInvocation call = body.expression;
    _isNum(call.staticType);
    _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));
   ''';
    Source source = addSource(code);
    TestAnalysisResult analysisResult = await computeAnalysisResult(source);
    assertNoErrors(source);
    verify([source]);
    CompilationUnit unit = analysisResult.unit;
    FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, "test");
    ExpressionFunctionBody body = test.functionExpression.body;
    MethodInvocation call = body.expression;
    _isNum(call.staticType);
    _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([]);
      }
   ''';
    CompilationUnit unit = await resolveSource(code);

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

  test_sync_star_method_propagation() async {
    String code = r'''
      import "dart:async";
      class A {
        Iterable f0() sync* { yield []; }
        Iterable f1() sync* { yield* new List(); }

        Iterable<List<int>> f2() sync* { yield []; }
        Iterable<List<int>> f3() sync* { yield* new List(); }
      }
   ''';
    CompilationUnit unit = await resolveSource(code);

    void check(String name, Asserter<InterfaceType> typeTest) {
      MethodDeclaration test = AstFinder.getMethodInClass(unit, "A", name);
      BlockFunctionBody body = test.body;
      YieldStatement stmt = body.block.statements[0];
      Expression exp = stmt.expression;
      typeTest(exp.staticType);
    }

    check("f0", _isListOf(_isDynamic));
    check("f1", _isListOf(_isDynamic));

    check("f2", _isListOf(_isInt));
    check("f3", _isListOf((DartType type) => _isListOf(_isInt)(type)));
  }

  test_sync_star_propagation() async {
    String code = r'''
      import "dart:async";

      Iterable f0() sync* { yield []; }
      Iterable f1() sync* { yield* new List(); }

      Iterable<List<int>> f2() sync* { yield []; }
      Iterable<List<int>> f3() sync* { yield* new List(); }
   ''';
    CompilationUnit unit = await resolveSource(code);

    void check(String name, Asserter<InterfaceType> typeTest) {
      FunctionDeclaration test = AstFinder.getTopLevelFunction(unit, name);
      BlockFunctionBody body = test.functionExpression.body;
      YieldStatement stmt = body.block.statements[0];
      Expression exp = stmt.expression;
      typeTest(exp.staticType);
    }

    check("f0", _isListOf(_isDynamic));
    check("f1", _isListOf(_isDynamic));

    check("f2", _isListOf(_isInt));
    check("f3", _isListOf((DartType type) => _isListOf(_isInt)(type)));
  }

  /// Verifies the source has the expected [errorCodes] as well as the
  /// expected [errorMessage].
  void _expectInferenceError(
      Source source, List<ErrorCode> errorCodes, String errorMessage) {
    assertErrors(source, errorCodes);
    var errors = analysisResults[source]
        .errors
        .where((e) => e.errorCode == StrongModeCode.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<ErrorCode> errors}) async {
    Source source = addSource("""
    import "dart:async";
    $code""");
    TestAnalysisResult analysisResult = await computeAnalysisResult(source);

    if (errors == null) {
      assertNoErrors(source);
    } else {
      assertErrors(source, errors);
    }
    verify([source]);
    FunctionDeclaration test =
        AstFinder.getTopLevelFunction(analysisResult.unit, "test");
    ExpressionFunctionBody body = test.functionExpression.body;
    return body.expression;
  }
}

/**
 * Strong mode static analyzer end to end tests
 */
@reflectiveTest
class StrongModeStaticTypeAnalyzer2Test extends StaticTypeAnalyzer2TestShared {
  void expectStaticInvokeType(String search, String type) {
    var invocation = findIdentifier(search).parent as MethodInvocation;
    expect(invocation.staticInvokeType.toString(), type);
  }

  void setUp() {
    super.setUp();
    AnalysisOptionsImpl options = new AnalysisOptionsImpl();
    options.strongMode = true;
    resetWith(options: options);
  }

  test_dynamicObjectGetter_hashCode() async {
    String code = r'''
main() {
  dynamic a = null;
  var foo = a.hashCode;
}
''';
    await resolveTestUnit(code);
    expectInitializerType('foo', 'int', isNull);
  }

  test_dynamicObjectMethod_toString() async {
    String code = r'''
main() {
  dynamic a = null;
  var foo = a.toString();
}
''';
    await resolveTestUnit(code);
    expectInitializerType('foo', 'String', isNull);
  }

  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 resolveTestUnit(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 resolveTestUnit(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 resolveTestUnit(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 resolveTestUnit(code);
  }

  test_generalizedVoid_assignToVoidOk() async {
    Source source = addSource(r'''
void main() {
  void x;
  x = 42;
}
''');
    await computeAnalysisResult(source);
    assertNoErrors(source);
  }

  test_genericFunction() async {
    await resolveTestUnit(r'T f<T>(T x) => null;');
    expectFunctionType('f', '<T>(T) → T',
        elementTypeParams: '[T]', typeFormals: '[T]');
    SimpleIdentifier f = findIdentifier('f');
    FunctionElementImpl e = f.staticElement;
    FunctionType ft = e.type.instantiate([typeProvider.stringType]);
    expect(ft.toString(), '(String) → String');
  }

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

  test_genericFunction_parameter() async {
    await resolveTestUnit(r'''
void g(T f<T>(T x)) {}
''', noErrors: false // TODO(paulberry): remove when dartbug.com/28515 fixed.
        );
    expectFunctionType('f', '<T>(T) → T',
        elementTypeParams: '[]', typeFormals: '[T]');
    SimpleIdentifier f = findIdentifier('f');
    ParameterElementImpl e = f.staticElement;
    FunctionType type = e.type;
    FunctionType ft = type.instantiate([typeProvider.stringType]);
    expect(ft.toString(), '(String) → String');
  }

  test_genericFunction_static() async {
    await resolveTestUnit(r'''
class C<E> {
  static T f<T>(T x) => null;
}
''');
    expectFunctionType('f', '<T>(T) → T',
        elementTypeParams: '[T]', typeFormals: '[T]');
    SimpleIdentifier f = findIdentifier('f');
    MethodElementImpl e = f.staticElement;
    FunctionType ft = e.type.instantiate([typeProvider.stringType]);
    expect(ft.toString(), '(String) → 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) {
    F f4;
    f0(3);
    f1(3);
    f2(3);
    f3(3);
    f4(3);
  }
}

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

    checkBody(String className) {
      List<Statement> statements =
          AstFinder.getStatementsInMethod(testUnit, className, "g");

      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 resolveTestUnit(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 resolveTestUnit(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 resolveTestUnit(r'''
class C<E> {
  List<T> f<T>(E e) => null;
}
main() {
  C<String> cOfString;
}
''');
    expectFunctionType('f', '<T>(E) → List<T>',
        elementTypeParams: '[T]',
        typeParams: '[E]',
        typeArgs: '[E]',
        typeFormals: '[T]');
    SimpleIdentifier c = findIdentifier('cOfString');
    FunctionType ft = (c.staticType as InterfaceType).getMethod('f').type;
    expect(ft.toString(), '<T>(String) → List<T>');
    ft = ft.instantiate([typeProvider.intType]);
    expect(ft.toString(), '(String) → List<int>');
    expect('${ft.typeArguments}/${ft.typeParameters}', '[String, int]/[E, T]');
  }

  test_genericMethod_explicitTypeParams() async {
    await resolveTestUnit(r'''
class C<E> {
  List<T> f<T>(E e) => null;
}
main() {
  C<String> cOfString;
  var x = cOfString.f<int>('hi');
}
''');
    MethodInvocation f = findIdentifier('f<int>').parent;
    FunctionType ft = f.staticInvokeType;
    expect(ft.toString(), '(String) → List<int>');
    expect('${ft.typeArguments}/${ft.typeParameters}', '[String, int]/[E, T]');

    SimpleIdentifier x = findIdentifier('x');
    expect(x.staticType,
        typeProvider.listType.instantiate([typeProvider.intType]));
  }

  test_genericMethod_functionExpressionInvocation_explicit() async {
    await resolveTestUnit(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);
}
''');
    expectIdentifierType('methodCall', "int");
    expectIdentifierType('staticCall', "int");
    expectIdentifierType('staticFieldCall', "int");
    expectIdentifierType('topFunCall', "int");
    expectIdentifierType('topFieldCall', "int");
    expectIdentifierType('localCall', "int");
    expectIdentifierType('paramCall', "int");
    expectIdentifierType('lambdaCall', "int");
  }

  test_genericMethod_functionExpressionInvocation_functionTypedParameter_explicit() async {
    await resolveTestUnit(r'''
void test<S>(T pf<T>(T e)) {
  var paramCall = (pf)<int>(3);
}
''', noErrors: false // TODO(paulberry): remove when dartbug.com/28515 fixed.
        );
    expectIdentifierType('paramCall', "int");
  }

  test_genericMethod_functionExpressionInvocation_functionTypedParameter_inferred() async {
    await resolveTestUnit(r'''
void test<S>(T pf<T>(T e)) {
  var paramCall = (pf)(3);
}
''', noErrors: false // TODO(paulberry): remove when dartbug.com/28515 fixed.
        );
    expectIdentifierType('paramCall', "int");
  }

  test_genericMethod_functionExpressionInvocation_inferred() async {
    await resolveTestUnit(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);
}
''', noErrors: false // TODO(paulberry): remove when dartbug.com/28515 fixed.
        );
    expectIdentifierType('methodCall', "int");
    expectIdentifierType('staticCall', "int");
    expectIdentifierType('staticFieldCall', "int");
    expectIdentifierType('topFunCall', "int");
    expectIdentifierType('topFieldCall', "int");
    expectIdentifierType('localCall', "int");
    expectIdentifierType('paramCall', "int");
    expectIdentifierType('lambdaCall', "int");
  }

  test_genericMethod_functionInvocation_explicit() async {
    await resolveTestUnit(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);
}
''');
    expectIdentifierType('methodCall', "int");
    expectIdentifierType('staticCall', "int");
    expectIdentifierType('staticFieldCall', "int");
    expectIdentifierType('topFunCall', "int");
    expectIdentifierType('topFieldCall', "int");
    expectIdentifierType('localCall', "int");
    expectIdentifierType('paramCall', "int");
  }

  test_genericMethod_functionInvocation_functionTypedParameter_explicit() async {
    await resolveTestUnit(r'''
void test<S>(T pf<T>(T e)) {
  var paramCall = pf<int>(3);
}
''', noErrors: false // TODO(paulberry): remove when dartbug.com/28515 fixed.
        );
    expectIdentifierType('paramCall', "int");
  }

  test_genericMethod_functionInvocation_functionTypedParameter_inferred() async {
    await resolveTestUnit(r'''
void test<S>(T pf<T>(T e)) {
  var paramCall = pf(3);
}
''', noErrors: false // TODO(paulberry): remove when dartbug.com/28515 fixed.
        );
    expectIdentifierType('paramCall', "int");
  }

  test_genericMethod_functionInvocation_inferred() async {
    await resolveTestUnit(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);
}
''');
    expectIdentifierType('methodCall', "int");
    expectIdentifierType('staticCall', "int");
    expectIdentifierType('staticFieldCall', "int");
    expectIdentifierType('topFunCall', "int");
    expectIdentifierType('topFieldCall', "int");
    expectIdentifierType('localCall', "int");
    expectIdentifierType('paramCall', "int");
  }

  test_genericMethod_functionTypedParameter() async {
    await resolveTestUnit(r'''
class C<E> {
  List<T> f<T>(T f(E e)) => null;
}
main() {
  C<String> cOfString;
}
''');
    expectFunctionType('f', '<T>((E) → T) → List<T>',
        elementTypeParams: '[T]',
        typeParams: '[E]',
        typeArgs: '[E]',
        typeFormals: '[T]');

    SimpleIdentifier c = findIdentifier('cOfString');
    FunctionType ft = (c.staticType as InterfaceType).getMethod('f').type;