pkg/nnbd_migration/test/edge_builder_test.dart

// Copyright (c) 2019, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

import 'package:analyzer/dart/analysis/features.dart';
import 'package:analyzer/dart/ast/ast.dart';
import 'package:analyzer/dart/element/element.dart';
import 'package:analyzer/dart/element/nullability_suffix.dart';
import 'package:analyzer/dart/element/type.dart';
import 'package:analyzer/dart/element/type_provider.dart';
import 'package:analyzer/dart/element/type_system.dart';
import 'package:analyzer/src/dart/analysis/experiments.dart';
import 'package:analyzer/src/dart/element/element.dart';
import 'package:analyzer/src/dart/element/type.dart';
import 'package:analyzer/src/dart/element/type_provider.dart';
import 'package:analyzer/src/dart/element/type_system.dart' show TypeSystemImpl;
import 'package:analyzer/src/dart/error/hint_codes.dart';
import 'package:analyzer/src/generated/source.dart';
import 'package:analyzer/src/generated/testing/test_type_provider.dart';
import 'package:nnbd_migration/fix_reason_target.dart';
import 'package:nnbd_migration/instrumentation.dart';
import 'package:nnbd_migration/src/decorated_class_hierarchy.dart';
import 'package:nnbd_migration/src/decorated_type.dart';
import 'package:nnbd_migration/src/edge_builder.dart';
import 'package:nnbd_migration/src/edge_origin.dart';
import 'package:nnbd_migration/src/expression_checks.dart';
import 'package:nnbd_migration/src/nullability_node.dart';
import 'package:pub_semver/pub_semver.dart';
import 'package:test/test.dart';
import 'package:test_reflective_loader/test_reflective_loader.dart';

import 'migration_visitor_test_base.dart';

main() {
  defineReflectiveSuite(() {
    defineReflectiveTests(AssignmentCheckerTest);
    defineReflectiveTests(EdgeBuilderTest);
  });
}

@reflectiveTest
class AssignmentCheckerTest extends Object
    with EdgeTester, DecoratedTypeTester {
  static const EdgeOrigin origin = _TestEdgeOrigin();

  LibraryElementImpl? _myLibrary;

  ClassElement? _myListOfListClass;

  late DecoratedType _myListOfListSupertype;

  @override
  final TypeProvider typeProvider;

  @override
  final NullabilityGraphForTesting graph;

  @override
  final decoratedTypeParameterBounds = DecoratedTypeParameterBounds();

  final AssignmentCheckerForTesting checker;

  factory AssignmentCheckerTest() {
    var typeProvider = TestTypeProvider().asLegacy;
    _setCoreLibrariesTypeSystem(typeProvider);

    var graph = NullabilityGraphForTesting();
    var decoratedClassHierarchy = _DecoratedClassHierarchyForTesting();
    var checker = AssignmentCheckerForTesting(
        TypeSystemImpl(
          implicitCasts: true,
          isNonNullableByDefault: false,
          strictCasts: false,
          strictInference: false,
          typeProvider: typeProvider,
        ),
        typeProvider,
        graph,
        decoratedClassHierarchy);
    var assignmentCheckerTest =
        AssignmentCheckerTest._(typeProvider, graph, checker);
    decoratedClassHierarchy.assignmentCheckerTest = assignmentCheckerTest;
    return assignmentCheckerTest;
  }

  AssignmentCheckerTest._(this.typeProvider, this.graph, this.checker);

  void assign(DecoratedType source, DecoratedType destination,
      {bool hard = false}) {
    checker.checkAssignment(origin,
        source: source, destination: destination, hard: hard);
  }

  DecoratedType myListOfList(DecoratedType elementType) {
    _initMyLibrary();
    if (_myListOfListClass == null) {
      var t = typeParameter('T', object());
      _myListOfListSupertype = list(list(typeParameterType(t)));
      _myListOfListClass = ClassElementImpl('MyListOfList', 0)
        ..enclosingElement = _myLibrary!.definingCompilationUnit
        ..typeParameters = [t]
        ..supertype = _myListOfListSupertype.type as InterfaceType?;
    }
    return DecoratedType(
      InterfaceTypeImpl(
        element: _myListOfListClass!,
        typeArguments: [elementType.type!],
        nullabilitySuffix: NullabilitySuffix.star,
      ),
      newNode(),
      typeArguments: [elementType],
    );
  }

  void test_bottom_to_generic() {
    var t = list(object());
    assign(bottom, t);
    assertEdge(never, t.node, hard: false);
    assertNoEdge(anyNode, t.typeArguments[0]!.node);
  }

  void test_bottom_to_simple() {
    var t = object();
    assign(bottom, t);
    assertEdge(never, t.node, hard: false);
  }

  void test_complex_to_typeParam() {
    var bound = list(object());
    var t1 = list(object());
    var t2 = typeParameterType(typeParameter('T', bound));
    assign(t1, t2, hard: true);
    assertEdge(t1.node, t2.node, hard: true);
    assertEdge(t1.node, bound.node, hard: false);
    // TODO(40622): Should this be a checkable edge?
    assertEdge(t1.typeArguments[0]!.node, bound.typeArguments[0]!.node,
        hard: false, checkable: false);
  }

  void test_dynamic_to_dynamic() {
    assign(dynamic_, dynamic_);
    // Note: no assertions to do; just need to make sure there wasn't a crash.
  }

  void test_dynamic_to_void() {
    assign(dynamic_, void_);
    // Note: no assertions to do; just need to make sure there wasn't a crash.
  }

  void test_function_type_named_parameter() {
    var t1 = function(dynamic_, named: {'x': object()});
    var t2 = function(dynamic_, named: {'x': object()});
    assign(t1, t2, hard: true);
    // Note: t1 and t2 are swapped due to contravariance.
    assertEdge(t2.namedParameters!['x']!.node, t1.namedParameters!['x']!.node,
        hard: false, checkable: false);
  }

  void test_function_type_named_to_no_parameter() {
    var t1 = function(dynamic_, named: {'x': object()});
    var t2 = function(dynamic_);
    assign(t1, t2);
    // Note: no assertions to do; just need to make sure there wasn't a crash.
  }

  void test_function_type_positional_parameter() {
    var t1 = function(dynamic_, positional: [object()]);
    var t2 = function(dynamic_, positional: [object()]);
    assign(t1, t2, hard: true);
    // Note: t1 and t2 are swapped due to contravariance.
    assertEdge(
        t2.positionalParameters![0]!.node, t1.positionalParameters![0]!.node,
        hard: false, checkable: false);
  }

  void test_function_type_positional_to_no_parameter() {
    var t1 = function(dynamic_, positional: [object()]);
    var t2 = function(dynamic_);
    assign(t1, t2);
    // Note: no assertions to do; just need to make sure there wasn't a crash.
  }

  void test_function_type_positional_to_required_parameter() {
    var t1 = function(dynamic_, positional: [object()]);
    var t2 = function(dynamic_, required: [object()]);
    assign(t1, t2, hard: true);
    // Note: t1 and t2 are swapped due to contravariance.
    assertEdge(
        t2.positionalParameters![0]!.node, t1.positionalParameters![0]!.node,
        hard: false, checkable: false);
  }

  void test_function_type_required_parameter() {
    var t1 = function(dynamic_, required: [object()]);
    var t2 = function(dynamic_, required: [object()]);
    assign(t1, t2);
    // Note: t1 and t2 are swapped due to contravariance.
    assertEdge(
        t2.positionalParameters![0]!.node, t1.positionalParameters![0]!.node,
        hard: false, checkable: false);
  }

  void test_function_type_return_type() {
    var t1 = function(object());
    var t2 = function(object());
    assign(t1, t2, hard: true);
    assertEdge(t1.returnType!.node, t2.returnType!.node,
        hard: false, checkable: false);
  }

  void test_function_void_to_function_object() {
    // This is not an ideal pattern, but void is assignable to Object in certain
    // cases such as those with compound types here. We must support it.
    var t1 = function(void_);
    var t2 = function(object());
    assign(t1, t2, hard: true);
    assertEdge(t1.returnType!.node, t2.returnType!.node,
        hard: false, checkable: false);
  }

  void test_future_int_to_future_or_int() {
    var t1 = future(int_());
    var t2 = futureOr(int_());
    assign(t1, t2, hard: true);
    assertEdge(t1.node, t2.node, hard: true);
    assertEdge(t1.typeArguments[0]!.node, t2.typeArguments[0]!.node,
        hard: true, checkable: false);
  }

  void test_future_or_int_to_future_int() {
    var t1 = futureOr(int_());
    var t2 = future(int_());
    assign(t1, t2, hard: true);
    // FutureOr<int>? is nullable, so Future<int>? should be.
    assertEdge(t1.node, t2.node, hard: true);
    // FutureOr<int?> is nullable, so Future<int>? should be.
    assertEdge(t1.typeArguments[0]!.node, t2.node, hard: true);
    // FutureOr<int?> may hold a Future<int?>, so carry that forward.
    assertEdge(t1.typeArguments[0]!.node, t2.typeArguments[0]!.node,
        hard: false);
    // FutureOr<int>? does not accept a Future<int?>, so don't draw this.
    assertNoEdge(t1.node, t2.typeArguments[0]!.node);
  }

  void test_future_or_int_to_int() {
    var t1 = futureOr(int_());
    var t2 = int_();
    assign(t1, t2, hard: true);
    assertEdge(t1.node, t2.node, hard: true);
    assertEdge(t1.typeArguments[0]!.node, t2.node, hard: false);
  }

  void test_future_or_list_object_to_list_int() {
    var t1 = futureOr(list(object()));
    var t2 = list(int_());
    assign(t1, t2, hard: true);
    assertEdge(t1.node, t2.node, hard: true);
    assertEdge(t1.typeArguments[0]!.node, t2.node, hard: false);
    assertEdge(
        t1.typeArguments[0]!.typeArguments[0]!.node, t2.typeArguments[0]!.node,
        hard: false);
  }

  void test_future_or_object_to_future_or_int() {
    var t1 = futureOr(object());
    var t2 = futureOr(int_());
    assign(t1, t2, hard: true);
    assertEdge(t1.node, t2.node, hard: true);
    assertEdge(t1.typeArguments[0]!.node, t2.typeArguments[0]!.node,
        hard: false);
  }

  void test_future_or_to_future_or() {
    var t1 = futureOr(int_());
    var t2 = futureOr(int_());
    assign(t1, t2, hard: true);
    assertEdge(t1.node, t2.node, hard: true);
    assertEdge(t1.typeArguments[0]!.node, t2.typeArguments[0]!.node,
        hard: false);
  }

  void test_generic_to_dynamic() {
    var t = list(object());
    assign(t, dynamic_);
    assertEdge(t.node, always, hard: false);
    assertNoEdge(t.typeArguments[0]!.node, anyNode);
  }

  void test_generic_to_generic_downcast() {
    var t1 = list(list(object()));
    var t2 = myListOfList(object());
    assign(t1, t2, hard: true);
    assertEdge(t1.node, t2.node, hard: true);
    // Let A, B, and C be nullability nodes such that:
    // - t2 is MyListOfList<Object?A>
    var a = t2.typeArguments[0]!.node;
    // - t1 is List<List<Object?B>>
    var b = t1.typeArguments[0]!.typeArguments[0]!.node;
    // - the supertype of MyListOfList<T> is List<List<T?C>>
    var c = _myListOfListSupertype.typeArguments[0]!.typeArguments[0]!.node;
    // Then there should be an edge from b to substitute(a, c)
    assertEdge(b, substitutionNode(a, c), hard: false);
  }

  void test_generic_to_generic_downcast_of_type_parameter() {
    var t = typeParameterType(typeParameter('T', object()));
    var t1 = iterable(t);
    var t2 = list(t);
    assign(t1, t2, hard: true);
    assertEdge(t1.node, t2.node, hard: true);
    var a = t1.typeArguments[0]!.node;
    var b = t2.typeArguments[0]!.node;
    assertEdge(a, b, hard: false);
  }

  void test_generic_to_generic_downcast_same_element() {
    var t1 = list(object());
    var t2 = list(int_());
    assign(t1, t2, hard: true);
    assertEdge(t1.node, t2.node, hard: true);
    assertEdge(t1.typeArguments[0]!.node, t2.typeArguments[0]!.node,
        hard: false);
  }

  void test_generic_to_generic_same_element() {
    var t1 = list(object());
    var t2 = list(object());
    assign(t1, t2, hard: true);
    assertEdge(t1.node, t2.node, hard: true);
    assertEdge(t1.typeArguments[0]!.node, t2.typeArguments[0]!.node,
        hard: true, checkable: false);
  }

  void test_generic_to_generic_upcast() {
    var t1 = myListOfList(object());
    var t2 = list(list(object()));
    assign(t1, t2);
    assertEdge(t1.node, t2.node, hard: false);
    // Let A, B, and C be nullability nodes such that:
    // - t1 is MyListOfList<Object?A>
    var a = t1.typeArguments[0]!.node;
    // - t2 is List<List<Object?B>>
    var b = t2.typeArguments[0]!.typeArguments[0]!.node;
    // - the supertype of MyListOfList<T> is List<List<T?C>>
    var c = _myListOfListSupertype.typeArguments[0]!.typeArguments[0]!.node;
    // Then there should be an edge from substitute(a, c) to b.
    assertEdge(substitutionNode(a, c), b, hard: false, checkable: false);
  }

  void test_generic_to_object() {
    var t1 = list(object());
    var t2 = object();
    assign(t1, t2);
    assertEdge(t1.node, t2.node, hard: false);
    assertNoEdge(t1.typeArguments[0]!.node, anyNode);
  }

  void test_generic_to_void() {
    var t = list(object());
    assign(t, void_);
    assertEdge(t.node, always, hard: false);
    assertNoEdge(t.typeArguments[0]!.node, anyNode);
  }

  void test_int_to_future_or_int() {
    var t1 = int_();
    var t2 = futureOr(int_());
    assign(t1, t2, hard: true);
    // Note: given code like:
    //   int x = null;
    //   FutureOr<int> y = x;
    // There are two possible migrations for `FutureOr<int>`: we could change it
    // to either `FutureOr<int?>` or `FutureOr<int>?`.  We choose to do
    // `FutureOr<int>?` because it is a narrower type, so it is less likely to
    // cause a proliferation of nullable types in the user's program.
    assertEdge(t1.node, t2.node, hard: true);
    assertNoEdge(t1.node, t2.typeArguments[0]!.node);
  }

  void test_iterable_object_to_list_void() {
    assign(iterable(object()), list(void_));
    // Note: no assertions to do; just need to make sure there wasn't a crash.
  }

  void test_null_to_generic() {
    var t = list(object());
    assign(null_, t);
    assertEdge(always, t.node, hard: false);
    assertNoEdge(anyNode, t.typeArguments[0]!.node);
  }

  void test_null_to_simple() {
    var t = object();
    assign(null_, t);
    assertEdge(always, t.node, hard: false);
  }

  void test_object_to_void() {
    assign(object(), void_);
    // Note: no assertions to do; just need to make sure there wasn't a crash.
  }

  void test_simple_to_dynamic() {
    var t = object();
    assign(t, dynamic_);
    assertEdge(t.node, always, hard: false);
  }

  void test_simple_to_simple() {
    var t1 = object();
    var t2 = object();
    assign(t1, t2);
    assertEdge(t1.node, t2.node, hard: false);
  }

  void test_simple_to_simple_hard() {
    var t1 = object();
    var t2 = object();
    assign(t1, t2, hard: true);
    assertEdge(t1.node, t2.node, hard: true);
  }

  void test_simple_to_void() {
    var t = object();
    assign(t, void_);
    assertEdge(t.node, always, hard: false);
  }

  void test_typeParam_to_complex() {
    var bound = list(object());
    var t1 = typeParameterType(typeParameter('T', bound));
    var t2 = list(object());
    assign(t1, t2, hard: true);
    assertEdge(t1.node, t2.node, hard: true);
    assertEdge(bound.node, t2.node, hard: false);
    // TODO(40622): Should this be a checkable edge?
    assertEdge(bound.typeArguments[0]!.node, t2.typeArguments[0]!.node,
        hard: false, checkable: false);
  }

  void test_typeParam_to_object() {
    var t1 = typeParameterType(typeParameter('T', object()));
    var t2 = object();
    assign(t1, t2);
    assertEdge(t1.node, t2.node, hard: false);
  }

  void test_typeParam_to_typeParam() {
    var t = typeParameter('T', object());
    var t1 = typeParameterType(t);
    var t2 = typeParameterType(t);
    assign(t1, t2);
    assertEdge(t1.node, t2.node, hard: false);
  }

  @override
  TypeParameterElement typeParameter(String name, DecoratedType bound) {
    var t = super.typeParameter(name, bound);
    checker.bounds[t] = bound;
    return t;
  }

  void _initMyLibrary() {
    if (_myLibrary != null) {
      return;
    }

    var coreLibrary = typeProvider.boolElement.library as LibraryElementImpl;
    var analysisContext = coreLibrary.context;
    var analysisSession = coreLibrary.session;
    var typeSystem = coreLibrary.typeSystem;

    var uriStr = 'package:test/test.dart';

    _myLibrary = LibraryElementImpl(
      analysisContext,
      analysisSession,
      uriStr,
      -1,
      0,
      FeatureSet.fromEnableFlags2(
        sdkLanguageVersion: Version.parse('2.10.0'),
        flags: [EnableString.non_nullable],
      ),
    );
    _myLibrary!.typeSystem = typeSystem;
    _myLibrary!.typeProvider = coreLibrary.typeProvider;

    var uri = Uri.parse(uriStr);
    var source = _MockSource(uri);

    var definingUnit = CompilationUnitElementImpl();
    definingUnit.source = source;
    definingUnit.librarySource = source;

    definingUnit.enclosingElement = _myLibrary;
    _myLibrary!.definingCompilationUnit = definingUnit;
  }

  static void _setCoreLibrariesTypeSystem(TypeProviderImpl typeProvider) {
    var typeSystem = TypeSystemImpl(
      isNonNullableByDefault: false,
      implicitCasts: true,
      strictCasts: false,
      strictInference: false,
      typeProvider: typeProvider,
    );
    _setLibraryTypeSystem(
      typeProvider.objectElement.library,
      typeProvider,
      typeSystem,
    );
    _setLibraryTypeSystem(
      typeProvider.futureElement.library,
      typeProvider,
      typeSystem,
    );
  }

  static void _setLibraryTypeSystem(
    LibraryElement libraryElement,
    TypeProvider typeProvider,
    TypeSystem typeSystem,
  ) {
    var libraryElementImpl = libraryElement as LibraryElementImpl;
    libraryElementImpl.typeProvider = typeProvider as TypeProviderImpl;
    libraryElementImpl.typeSystem = typeSystem as TypeSystemImpl;
  }
}

@reflectiveTest
class EdgeBuilderTest extends EdgeBuilderTestBase {
  void assertGLB(
      NullabilityNode? node, NullabilityNode? left, NullabilityNode? right) {
    expect(node, isNot(TypeMatcher<NullabilityNodeForLUB>()));
    assertEdge(left, node, hard: false, guards: [right]);
    assertEdge(node, left, hard: false);
    assertEdge(node, right, hard: false);
  }

  void assertLUB(NullabilityNode node, Object? left, Object? right) {
    var conditionalNode = node as NullabilityNodeForLUB;
    var leftMatcher = NodeMatcher(left);
    var rightMatcher = NodeMatcher(right);
    expect(leftMatcher.matches(conditionalNode.left), true);
    expect(rightMatcher.matches(conditionalNode.right), true);
  }

  /// Checks that there are no nullability nodes upstream from [node] that could
  /// cause it to become nullable.
  void assertNoUpstreamNullability(NullabilityNode? node) {
    // Store `neverClosure` in a local variable so that we avoid the
    // computational expense of recomputing it each time through the loop below.
    var neverClosure = this.neverClosure;

    // Any node with a hard edge to never (or never itself) won't become
    // nullable, even if it has nodes upstream from it.
    if (neverClosure.contains(node)) return;

    // Otherwise, make sure that every node directly upstream from this node
    // has a hard edge to never.
    for (var edge in getEdges(anyNode, node)) {
      expect(neverClosure, contains(edge.sourceNode));
    }
  }

  /// Verifies that a null check will occur when the given edge is unsatisfied.
  ///
  /// [expressionChecks] is the object tracking whether or not a null check is
  /// needed.
  void assertNullCheck(
      ExpressionChecksOrigin expressionChecks, NullabilityEdge expectedEdge) {
    expect(expressionChecks.checks.edges.values, contains(expectedEdge));
  }

  /// Gets the [ExpressionChecks] associated with the expression whose text
  /// representation is [text], or `null` if the expression has no
  /// [ExpressionChecks] associated with it.
  ExpressionChecksOrigin? checkExpression(String text) {
    return variables!.checkExpression(findNode.expression(text));
  }

  /// Gets the [DecoratedType] associated with the expression whose text
  /// representation is [text], or `null` if the expression has no
  /// [DecoratedType] associated with it.
  DecoratedType? decoratedExpressionType(String text) {
    return variables!.decoratedExpressionType(findNode.expression(text));
  }

  bool hasNullCheckHint(Expression expression) =>
      variables!.getNullCheckHint(testSource, expression) != null;

  Future<void> test_already_migrated_field() async {
    await analyze('''
double f() => double.nan;
''');
    var nanElement = typeProvider.doubleType.element.getField('nan')!;
    assertEdge(variables!.decoratedElementType(nanElement).node,
        decoratedTypeAnnotation('double f').node,
        hard: false);
  }

  Future<void> test_ArgumentError_checkNotNull_not_postDominating() async {
    await analyze('''
void f(bool b, int i, int j) {
  ArgumentError.checkNotNull(j);
  if (b) return;
  ArgumentError.checkNotNull(i);
}
''');

    // Asserts after ifs don't demonstrate non-null intent.
    assertNoEdge(decoratedTypeAnnotation('int i').node, never);
    // But asserts before ifs do
    assertEdge(decoratedTypeAnnotation('int j').node, never, hard: true);
  }

  Future<void> test_ArgumentError_checkNotNull_postDominating() async {
    await analyze('''
void f(int i) {
  ArgumentError.checkNotNull(i);
}
''');

    assertEdge(decoratedTypeAnnotation('int i').node, never, hard: true);
  }

  Future<void> test_ArgumentError_checkNotNull_prefixed() async {
    await analyze('''
import 'dart:core' as core;
void f(core.int i) {
  core.ArgumentError.checkNotNull(i);
}
''');

    assertEdge(decoratedTypeAnnotation('int i').node, never, hard: true);
  }

  Future<void> test_as_dynamic() async {
    await analyze('''
void f(Object o) {
  (o as dynamic).gcd(1);
}
''');
    assertEdge(decoratedTypeAnnotation('Object o').node,
        decoratedTypeAnnotation('dynamic').node,
        hard: true);
    assertEdge(decoratedTypeAnnotation('dynamic').node, never, hard: true);
  }

  Future<void> test_as_int() async {
    await analyze('''
void f(Object o) {
  (o as int).gcd(1);
}
''');
    assertEdge(decoratedTypeAnnotation('Object o').node,
        decoratedTypeAnnotation('int').node,
        hard: true);
    assertEdge(decoratedTypeAnnotation('int').node, never, hard: true);
    expect(
        variables!.wasUnnecessaryCast(testSource, findNode.as_('o as')), false);
  }

  Future<void> test_as_int_null_ok() async {
    await analyze('''
void f(Object o) {
  (o as int)?.gcd(1);
}
''');
    assertEdge(decoratedTypeAnnotation('Object o').node,
        decoratedTypeAnnotation('int').node,
        hard: true);
    assertNoEdge(decoratedTypeAnnotation('int').node, never);
  }

  Future<void> test_as_int_unnecessary() async {
    verifyNoTestUnitErrors = false;
    await analyze('''
void f(int i) {
  (i as int).gcd(1);
}
''');
    expect(
        testAnalysisResult.errors.single.errorCode, HintCode.UNNECESSARY_CAST);
    assertEdge(decoratedTypeAnnotation('int i').node,
        decoratedTypeAnnotation('int)').node,
        hard: true);
    assertEdge(decoratedTypeAnnotation('int)').node, never, hard: true);
    expect(
        variables!.wasUnnecessaryCast(testSource, findNode.as_('i as')), true);
  }

  Future<void> test_as_side_cast() async {
    await analyze('''
class A {}
class B {}
class C implements A, B {}
B f(A a) {
  // possible via f(C());
  return a as B;
}
''');
    assertEdge(
        decoratedTypeAnnotation('A a').node, decoratedTypeAnnotation('B;').node,
        hard: true);
  }

  Future<void> test_as_side_cast_generics() async {
    await analyze('''
class A<T> {}
class B<T> {}
class C implements A<int>, B<bool> {}
B<bool> f(A<int> a) {
  // possible via f(C());
  return a as B<bool>;
}
''');
    assertEdge(decoratedTypeAnnotation('A<int> a').node,
        decoratedTypeAnnotation('B<bool>;').node,
        hard: true);
    assertEdge(decoratedTypeAnnotation('bool>;').node,
        decoratedTypeAnnotation('bool> f').node,
        hard: true, checkable: false);
    assertNoEdge(anyNode, decoratedTypeAnnotation('bool>;').node);
    assertNoEdge(anyNode, decoratedTypeAnnotation('int> a').node);
    // int> a should be connected to the bound of T in A<T>, but nothing else.
    expect(
        decoratedTypeAnnotation('int> a').node!.downstreamEdges, hasLength(1));
  }

  Future<void> test_assert_demonstrates_non_null_intent() async {
    await analyze('''
void f(int i) {
  assert(i != null);
}
''');

    assertEdge(decoratedTypeAnnotation('int i').node, never, hard: true);
  }

  Future<void> test_assert_initializer_demonstrates_non_null_intent() async {
    await analyze('''
class C {
  C(int i)
    : assert(i != null);
}
''');

    assertEdge(decoratedTypeAnnotation('int i').node, never, hard: true);
  }

  Future<void> test_assert_is_demonstrates_non_null_intent() async {
    // Note, this could also be handled via improved flow analysis rather than a
    // hard edge.
    await analyze('''
void f(dynamic i) {
  assert(i is int);
}
''');

    assertEdge(decoratedTypeAnnotation('dynamic i').node, never, hard: true);
  }

  Future<void> test_assign_bound_to_type_parameter() async {
    await analyze('''
class C<T extends List<int>> {
  T f(List<int> x) => x;
}
''');
    var boundType = decoratedTypeAnnotation('List<int>>');
    var parameterType = decoratedTypeAnnotation('List<int> x');
    var tType = decoratedTypeAnnotation('T f');
    assertEdge(parameterType.node, tType.node, hard: true);
    assertEdge(parameterType.node, boundType.node, hard: false);
    // TODO(mfairhurst): Confirm we want this edge.
    // TODO(40622): Should this be a checkable edge?
    assertEdge(
        parameterType.typeArguments[0]!.node, boundType.typeArguments[0]!.node,
        hard: false, checkable: false);
  }

  Future<void> test_assign_dynamic_to_other_type() async {
    await analyze('''
int f(dynamic d) => d;
''');
    // There is no explicit null check necessary, since `dynamic` is
    // downcastable to any type, nullable or not.
    expect(checkExpression('d;'), isNull);
    // But we still create an edge, to make sure that the possibility of `null`
    // propagates to callees.
    assertEdge(decoratedTypeAnnotation('dynamic').node,
        decoratedTypeAnnotation('int').node,
        hard: true);
  }

  Future<void> test_assign_function_type_to_function_interface_type() async {
    await analyze('''
Function f(void Function() x) => x;
''');
    assertEdge(decoratedGenericFunctionTypeAnnotation('void Function()').node,
        decoratedTypeAnnotation('Function f').node,
        hard: true);
  }

  Future<void> test_assign_future_to_futureOr_complex() async {
    await analyze('''
import 'dart:async';
FutureOr<List<int>> f(Future<List<int>> x) => x;
''');
    // If `x` is `Future<List<int?>>`, then the only way to migrate is to make
    // the return type `FutureOr<List<int?>>`.
    assertEdge(decoratedTypeAnnotation('int>> x').node,
        decoratedTypeAnnotation('int>> f').node,
        hard: true, checkable: false);
    assertNoEdge(decoratedTypeAnnotation('int>> x').node,
        decoratedTypeAnnotation('List<int>> f').node);
    assertNoEdge(decoratedTypeAnnotation('int>> x').node,
        decoratedTypeAnnotation('FutureOr<List<int>> f').node);
  }

  Future<void> test_assign_future_to_futureOr_simple() async {
    await analyze('''
import 'dart:async';
FutureOr<int> f(Future<int> x) => x;
''');
    // If `x` is nullable, then there are two migrations possible: we could make
    // the return type `FutureOr<int?>` or we could make it `FutureOr<int>?`.
    // We choose `FutureOr<int>?` because it's strictly more conservative (it's
    // a subtype of `FutureOr<int?>`).
    assertEdge(decoratedTypeAnnotation('Future<int> x').node,
        decoratedTypeAnnotation('FutureOr<int>').node,
        hard: true);
    assertNoEdge(decoratedTypeAnnotation('Future<int> x').node,
        decoratedTypeAnnotation('int> f').node);
    // If `x` is `Future<int?>`, then the only way to migrate is to make the
    // return type `FutureOr<int?>`.

    assertEdge(
        substitutionNode(
            decoratedTypeAnnotation('int> x').node, inSet(pointsToNever)),
        decoratedTypeAnnotation('int> f').node,
        hard: true,
        checkable: false);
    assertNoEdge(decoratedTypeAnnotation('int> x').node,
        decoratedTypeAnnotation('FutureOr<int>').node);
  }

  Future<void> test_assign_non_future_to_futureOr_complex() async {
    await analyze('''
import 'dart:async';
FutureOr<List<int>> f(List<int> x) => x;
''');
    // If `x` is `List<int?>`, then the only way to migrate is to make the
    // return type `FutureOr<List<int?>>`.
    assertEdge(decoratedTypeAnnotation('int> x').node,
        decoratedTypeAnnotation('int>> f').node,
        hard: false, checkable: false);
    assertNoEdge(decoratedTypeAnnotation('int> x').node,
        decoratedTypeAnnotation('List<int>> f').node);
    assertNoEdge(decoratedTypeAnnotation('int> x').node,
        decoratedTypeAnnotation('FutureOr<List<int>> f').node);
  }

  Future<void> test_assign_non_future_to_futureOr_simple() async {
    await analyze('''
import 'dart:async';
FutureOr<int> f(int x) => x;
''');
    // If `x` is nullable, then there are two migrations possible: we could make
    // the return type `FutureOr<int?>` or we could make it `FutureOr<int>?`.
    // We choose `FutureOr<int>?` because it's strictly more conservative (it's
    // a subtype of `FutureOr<int?>`).
    assertEdge(decoratedTypeAnnotation('int x').node,
        decoratedTypeAnnotation('FutureOr<int>').node,
        hard: true);
    assertNoEdge(decoratedTypeAnnotation('int x').node,
        decoratedTypeAnnotation('int>').node);
  }

  Future<void> test_assign_null_to_generic_type() async {
    await analyze('''
main() {
  List<int> x = null;
}
''');
    // TODO(paulberry): edge should be hard.
    assertEdge(inSet(alwaysPlus), decoratedTypeAnnotation('List').node,
        hard: false);
  }

  Future<void> test_assign_to_bound_as() async {
    // TODO(mfairhurst): support downcast to type params with bounds
    await analyze('''
class C<T> {}
void f(Object o) {
  o as C<int>;
}
''');
    // For now, edge to `anyNode`, because the true bound is inferred.
    assertEdge(decoratedTypeAnnotation('int').node, anyNode, hard: true);
  }

  Future<void> test_assign_to_bound_class_alias() async {
    await analyze('''
class C<T extends Object/*1*/> {}
class D<T extends Object/*2*/> {}
mixin M<T extends Object/*3*/> {}
class F = C<int> with M<String> implements D<num>;
''');
    assertEdge(decoratedTypeAnnotation('int').node,
        decoratedTypeAnnotation('Object/*1*/').node,
        hard: true);
    assertEdge(decoratedTypeAnnotation('num').node,
        decoratedTypeAnnotation('Object/*2*/').node,
        hard: true);
    assertEdge(decoratedTypeAnnotation('String').node,
        decoratedTypeAnnotation('Object/*3*/').node,
        hard: true);
  }

  Future<void> test_assign_to_bound_class_extends() async {
    await analyze('''
class A<T extends Object> {}
class C extends A<int> {}
''');
    assertEdge(decoratedTypeAnnotation('int').node,
        decoratedTypeAnnotation('Object').node,
        hard: true);
  }

  Future<void> test_assign_to_bound_class_implements() async {
    await analyze('''
class A<T extends Object> {}
class C implements A<int> {}
''');
    assertEdge(decoratedTypeAnnotation('int').node,
        decoratedTypeAnnotation('Object').node,
        hard: true);
  }

  Future<void> test_assign_to_bound_class_with() async {
    await analyze('''
class A<T extends Object> {}
class C extends Object with A<int> {}
''');
    assertEdge(decoratedTypeAnnotation('int').node,
        decoratedTypeAnnotation('Object>').node,
        hard: true);
  }

  Future<void> test_assign_to_bound_extension_extended_type() async {
    await analyze('''
class C<T extends Object> {}
extension E on C<int> {}
''');
    assertEdge(decoratedTypeAnnotation('int').node,
        decoratedTypeAnnotation('Object>').node,
        hard: true);
  }

  Future<void> test_assign_to_bound_field_formal_typed() async {
    await analyze('''
class C<T extends Object> {}
class D {
  dynamic i;
  D(C<int> this.i);
}
''');
    assertEdge(decoratedTypeAnnotation('int').node,
        decoratedTypeAnnotation('Object').node,
        hard: true);
  }

  Future<void> test_assign_to_bound_field_formal_typed_function() async {
    await analyze('''
class C<T extends Object> {}
class D {
  dynamic i;
  D(this.i(C<int> name));
}
''');
    assertEdge(decoratedTypeAnnotation('int').node,
        decoratedTypeAnnotation('Object').node,
        hard: true);
  }

  Future<void> test_assign_to_bound_for() async {
    await analyze('''
class C<T extends Object> {}
void main() {
  for (C<int> c = null ;;) {}
}
''');
    assertEdge(decoratedTypeAnnotation('int').node,
        decoratedTypeAnnotation('Object>').node,
        hard: true);
  }

  Future<void> test_assign_to_bound_for_element() async {
    await analyze('''
class C<T extends Object> {}
void main() {
  [for (C<int> c = null ;;) c];
}
''');
    assertEdge(decoratedTypeAnnotation('int').node,
        decoratedTypeAnnotation('Object>').node,
        hard: true);
  }

  Future<void> test_assign_to_bound_for_in() async {
    await analyze('''
class C<T extends Object> {}
void main() {
  for (C<int> c in []) {}
}
''');
    assertEdge(decoratedTypeAnnotation('int').node,
        decoratedTypeAnnotation('Object>').node,
        hard: true);
  }

  Future<void> test_assign_to_bound_for_in_element() async {
    await analyze('''
class C<T extends Object> {}
void main() {
  [for (C<int> c in []) c];
}
''');
    assertEdge(decoratedTypeAnnotation('int').node,
        decoratedTypeAnnotation('Object>').node,
        hard: true);
  }

  Future<void> test_assign_to_bound_function_invocation_type_argument() async {
    await analyze('''
void f<T extends Object>() {}
void main() {
  (f)<int>();
}
''');
    assertEdge(decoratedTypeAnnotation('int').node,
        decoratedTypeAnnotation('Object').node,
        hard: true);
  }

  Future<void> test_assign_to_bound_in_return_type() async {
    await analyze('''
class C<T extends Object> {}
C<int> f() => null;
''');
    assertEdge(decoratedTypeAnnotation('int').node,
        decoratedTypeAnnotation('Object').node,
        hard: true);
  }

  Future<void> test_assign_to_bound_in_type_argument() async {
    await analyze('''
class C<T extends Object> {}
C<C<int>> f() => null;
''');
    assertEdge(decoratedTypeAnnotation('C<int>').node,
        decoratedTypeAnnotation('Object').node,
        hard: true);
    assertEdge(decoratedTypeAnnotation('int').node,
        decoratedTypeAnnotation('Object').node,
        hard: true);
  }

  Future<void> test_assign_to_bound_instance_creation() async {
    await analyze('''
class C<T extends Object> {}
void main() {
  C<int>();
}
''');
    assertEdge(decoratedTypeAnnotation('int').node,
        decoratedTypeAnnotation('Object').node,
        hard: true);
  }

  Future<void> test_assign_to_bound_list_literal() async {
    await analyze('''
class C<T extends Object> {}
void main() {
  <C<int>>[];
}
''');
    assertEdge(decoratedTypeAnnotation('int').node,
        decoratedTypeAnnotation('Object').node,
        hard: true);
  }

  Future<void> test_assign_to_bound_local_variable() async {
    await analyze('''
class C<T extends Object> {}
main() {
  C<int> c = null;
}
''');
    assertEdge(decoratedTypeAnnotation('int').node,
        decoratedTypeAnnotation('Object').node,
        hard: true);
  }

  Future<void> test_assign_to_bound_map_literal() async {
    await analyze('''
class C<T extends Object> {}
void main() {
  <C<int>, C<String>>{};
}
''');
    assertEdge(decoratedTypeAnnotation('int').node,
        decoratedTypeAnnotation('Object').node,
        hard: true);
    assertEdge(decoratedTypeAnnotation('String').node,
        decoratedTypeAnnotation('Object').node,
        hard: true);
  }

  Future<void> test_assign_to_bound_method_bound() async {
    await analyze('''
class C<T extends Object> {}
class D {
  f<U extends C<int>>() {}
}
''');
  }

  Future<void> test_assign_to_bound_method_call_type_argument() async {
    await analyze('''
void f<T extends Object>() {}
void main() {
  f<int>();
}
''');
    assertEdge(decoratedTypeAnnotation('int').node,
        decoratedTypeAnnotation('Object').node,
        hard: true);
  }

  Future<void> test_assign_to_bound_mixin_implements() async {
    await analyze('''
class A<T extends Object> {}
mixin C implements A<int> {}
''');
    assertEdge(decoratedTypeAnnotation('int').node,
        decoratedTypeAnnotation('Object').node,
        hard: true);
  }

  Future<void> test_assign_to_bound_mixin_on() async {
    await analyze('''
class A<T extends Object> {}
mixin C on A<int> {}
''');
    assertEdge(decoratedTypeAnnotation('int').node,
        decoratedTypeAnnotation('Object').node,
        hard: true);
  }

  Future<void> test_assign_to_bound_mixin_type_parameter_bound() async {
    await analyze('''
class C<T extends Object> {}
mixin M<T extends C<int>> {}
''');
    assertEdge(decoratedTypeAnnotation('int').node,
        decoratedTypeAnnotation('Object').node,
        hard: true);
  }

  Future<void> test_assign_to_bound_redirecting_constructor_argument() async {
    await analyze('''
class A<T extends Object> {}
class C {
  factory C() = D<A<int>>;
}
class D<U> implements C {}
''');
    assertEdge(decoratedTypeAnnotation('int').node,
        decoratedTypeAnnotation('Object').node,
        hard: true);
  }

  Future<void> test_assign_to_bound_set_literal() async {
    await analyze('''
class C<T extends Object> {}
void main() {
  <C<int>>{};
}
''');
    assertEdge(decoratedTypeAnnotation('int').node,
        decoratedTypeAnnotation('Object').node,
        hard: true);
  }

  Future<void> test_assign_to_bound_within_bound() async {
    await analyze('''
class A<T extends Object> {}
class B<T extends A<int>> {}
  ''');
    var aBound = decoratedTypeAnnotation('Object').node;
    var aBoundInt = decoratedTypeAnnotation('int').node;
    assertEdge(aBoundInt, aBound, hard: true);
  }

  Future<void> test_assign_to_bound_within_bound_method() async {
    await analyze('''
class C<T extends Object> {}
void f<T extends C<int>>() {}
''');
    var cBound = decoratedTypeAnnotation('Object').node;
    var fcInt = decoratedTypeAnnotation('int').node;
    assertEdge(fcInt, cBound, hard: true);
  }

  Future<void> test_assign_type_parameter_to_bound() async {
    await analyze('''
class C<T extends List<int>> {
  List<int> f(T x) => x;
}
''');
    var boundType = decoratedTypeAnnotation('List<int>>');
    var returnType = decoratedTypeAnnotation('List<int> f');
    var tType = decoratedTypeAnnotation('T x');
    assertEdge(tType.node, returnType.node, hard: true);
    assertEdge(boundType.node, returnType.node, hard: false);
    // TODO(40622): Should this be a checkable edge?
    assertEdge(
        boundType.typeArguments[0]!.node, returnType.typeArguments[0]!.node,
        hard: false, checkable: false);
  }

  Future<void> test_assign_upcast_generic() async {
    await analyze('''
void f(Iterable<int> x) {}
void g(List<int> x) {
  f(x);
}
''');

    var iterableInt = decoratedTypeAnnotation('Iterable<int>');
    var listInt = decoratedTypeAnnotation('List<int>');
    assertEdge(listInt.node, iterableInt.node, hard: true);
    assertEdge(
        substitutionNode(listInt.typeArguments[0]!.node, inSet(pointsToNever)),
        iterableInt.typeArguments[0]!.node,
        hard: true,
        checkable: false);
  }

  Future<void> test_assignment_code_reference() async {
    await analyze('''
void f(int i) {
  int j = i;
}
''');
    var edge = assertEdge(decoratedTypeAnnotation('int i').node,
        decoratedTypeAnnotation('int j').node,
        hard: true);
    var codeReference = edge.codeReference!;
    expect(codeReference, isNotNull);
    expect(codeReference.path, contains('test.dart'));
    expect(codeReference.line, 2);
    expect(codeReference.column, 11);
  }

  Future<void> test_assignmentExpression_compound_dynamic() async {
    await analyze('''
void f(dynamic x, int y) {
  x += y;
}
''');
    // No assertions; just making sure this doesn't crash.
  }

  Future<void> test_assignmentExpression_compound_simple() async {
    var code = '''
abstract class C {
  C operator+(C x);
}
C f(C y, C z) => (y += z);
''';
    await analyze(code);
    var targetEdge = assertEdge(
        decoratedTypeAnnotation('C y').node, inSet(pointsToNever),
        hard: true);
    expect(
        (graph.getEdgeOrigin(targetEdge) as CompoundAssignmentOrigin)
            .node!
            .operator
            .offset,
        code.indexOf('+='));
    assertNullCheck(
        checkExpression('z);')!,
        assertEdge(decoratedTypeAnnotation('C z').node,
            decoratedTypeAnnotation('C x').node,
            hard: true));
    var operatorReturnEdge = assertEdge(
        decoratedTypeAnnotation('C operator').node,
        decoratedTypeAnnotation('C y').node,
        hard: false);
    expect(
        (graph.getEdgeOrigin(operatorReturnEdge) as CompoundAssignmentOrigin)
            .node!
            .operator
            .offset,
        code.indexOf('+='));
    var fReturnEdge = assertEdge(decoratedTypeAnnotation('C operator').node,
        decoratedTypeAnnotation('C f').node,
        hard: false);
    assertNullCheck(checkExpression('(y += z)')!, fReturnEdge);
  }

  Future<void> test_assignmentExpression_compound_withSubstitution() async {
    // Failing due to a side-cast from incorrectly instantiating the operator.
    var code = '''
abstract class C<T> {
  C<T> operator+(C<T> x);
}
C<int> f(C<int> y, C<int> z) => (y += z);
''';
    await analyze(code);
    var targetEdge = assertEdge(
        decoratedTypeAnnotation('C<int> y').node, inSet(pointsToNever),
        hard: true);
    expect(
        (graph.getEdgeOrigin(targetEdge) as CompoundAssignmentOrigin)
            .node!
            .operator
            .offset,
        code.indexOf('+='));
    assertNullCheck(
        checkExpression('z);')!,
        assertEdge(decoratedTypeAnnotation('C<int> z').node,
            decoratedTypeAnnotation('C<T> x').node,
            hard: true));
    var operatorReturnEdge = assertEdge(
        decoratedTypeAnnotation('C<T> operator').node,
        decoratedTypeAnnotation('C<int> y').node,
        hard: false);
    expect(
        (graph.getEdgeOrigin(operatorReturnEdge) as CompoundAssignmentOrigin)
            .node!
            .operator
            .offset,
        code.indexOf('+='));
    var fReturnEdge = assertEdge(decoratedTypeAnnotation('C<T> operator').node,
        decoratedTypeAnnotation('C<int> f').node,
        hard: false);
    assertNullCheck(checkExpression('(y += z)')!, fReturnEdge);
  }

  Future<void> test_assignmentExpression_field() async {
    await analyze('''
class C {
  int x = 0;
}
void f(C c, int i) {
  c.x = i;
}
''');
    assertEdge(decoratedTypeAnnotation('int i').node,
        decoratedTypeAnnotation('int x').node,
        hard: true);
  }

  Future<void> test_assignmentExpression_field_cascaded() async {
    await analyze('''
class C {
  int x = 0;
}
void f(C c, int i) {
  c..x = i;
}
''');
    assertEdge(decoratedTypeAnnotation('int i').node,
        decoratedTypeAnnotation('int x').node,
        hard: true);
  }

  Future<void> test_assignmentExpression_field_target_check() async {
    await analyze('''
class C {
  int x = 0;
}
void f(C c, int i) {
  c.x = i;
}
''');
    assertNullCheck(checkExpression('c.x')!,
        assertEdge(decoratedTypeAnnotation('C c').node, never, hard: true));
  }

  Future<void> test_assignmentExpression_field_target_check_cascaded() async {
    await analyze('''
class C {
  int x = 0;
}
void f(C c, int i) {
  c..x = i;
}
''');
    assertNullCheck(checkExpression('c..x')!,
        assertEdge(decoratedTypeAnnotation('C c').node, never, hard: true));
  }

  Future<void> test_assignmentExpression_indexExpression_index() async {
    await analyze('''
class C {
  void operator[]=(int a, int b) {}
}
void f(C c, int i, int j) {
  c[i] = j;
}
''');
    assertEdge(decoratedTypeAnnotation('int i').node,
        decoratedTypeAnnotation('int a').node,
        hard: true);
  }

  Future<void> test_assignmentExpression_indexExpression_return_value() async {
    await analyze('''
class C {
  void operator[]=(int a, int b) {}
}
int f(C c, int i, int j) => c[i] = j;
''');
    assertEdge(decoratedTypeAnnotation('int j').node,
        decoratedTypeAnnotation('int f').node,
        hard: false);
  }

  Future<void> test_assignmentExpression_indexExpression_target_check() async {
    await analyze('''
class C {
  void operator[]=(int a, int b) {}
}
void f(C c, int i, int j) {
  c[i] = j;
}
''');
    assertNullCheck(checkExpression('c[')!,
        assertEdge(decoratedTypeAnnotation('C c').node, never, hard: true));
  }

  Future<void> test_assignmentExpression_indexExpression_value() async {
    await analyze('''
class C {
  void operator[]=(int a, int b) {}
}
void f(C c, int i, int j) {
  c[i] = j;
}
''');
    assertEdge(decoratedTypeAnnotation('int j').node,
        decoratedTypeAnnotation('int b').node,
        hard: true);
  }

  Future<void>
      test_assignmentExpression_nullAware_complex_contravariant() async {
    await analyze('''
void Function(int) f(void Function(int) x, void Function(int) y) => x ??= y;
''');
    var xNullable =
        decoratedGenericFunctionTypeAnnotation('void Function(int) x').node;
    var xParamNullable = decoratedTypeAnnotation('int) x').node;
    var yParamNullable = decoratedTypeAnnotation('int) y').node;
    var returnParamNullable = decoratedTypeAnnotation('int) f').node;
    assertEdge(xParamNullable, yParamNullable,
        hard: false, checkable: false, guards: [xNullable]);
    assertEdge(returnParamNullable, xParamNullable,
        hard: false, checkable: false);
  }

  Future<void> test_assignmentExpression_nullAware_complex_covariant() async {
    await analyze('''
List<int> f(List<int> x, List<int> y) => x ??= y;
''');
    var xNullable = decoratedTypeAnnotation('List<int> x').node;
    var yNullable = decoratedTypeAnnotation('List<int> y').node;
    var xElementNullable = decoratedTypeAnnotation('int> x').node;
    var yElementNullable = decoratedTypeAnnotation('int> y').node;
    var returnElementNullable = decoratedTypeAnnotation('int> f').node;
    assertEdge(yNullable, xNullable, hard: false, guards: [xNullable]);
    assertEdge(yElementNullable, xElementNullable,
        hard: false, checkable: false, guards: [xNullable]);
    assertEdge(xElementNullable, returnElementNullable,
        hard: false, checkable: false);
  }

  Future<void> test_assignmentExpression_nullAware_simple() async {
    await analyze('''
int f(int x, int y) => (x ??= y);
''');
    var yNullable = decoratedTypeAnnotation('int y').node;
    var xNullable = decoratedTypeAnnotation('int x').node;
    var returnNullable = decoratedTypeAnnotation('int f').node;
    var glbNode = decoratedExpressionType('(x ??= y)')!.node;
    assertEdge(yNullable, xNullable, hard: false, guards: [xNullable]);
    assertEdge(yNullable, glbNode, hard: false, guards: [xNullable]);
    assertEdge(glbNode, xNullable, hard: false);
    assertEdge(glbNode, yNullable, hard: false);
    assertEdge(glbNode, returnNullable, hard: false);
  }

  Future<void> test_assignmentExpression_operands() async {
    await analyze('''
void f(int i, int j) {
  i = j;
}
''');
    assertEdge(decoratedTypeAnnotation('int j').node,
        decoratedTypeAnnotation('int i').node,
        hard: true);
  }

  Future<void> test_assignmentExpression_return_value() async {
    await analyze('''
void f(int i, int j) {
  g(i = j);
}
void g(int k) {}
''');
    assertEdge(decoratedTypeAnnotation('int j').node,
        decoratedTypeAnnotation('int k').node,
        hard: false);
  }

  Future<void> test_assignmentExpression_setter() async {
    await analyze('''
class C {
  void set s(int value) {}
}
void f(C c, int i) {
  c.s = i;
}
''');
    assertEdge(decoratedTypeAnnotation('int i').node,
        decoratedTypeAnnotation('int value').node,
        hard: true);
  }

  Future<void> test_assignmentExpression_setter_null_aware() async {
    await analyze('''
class C {
  void set s(int value) {}
}
int f(C c, int i) => (c?.s = i);
''');
    var lubNode =
        decoratedExpressionType('(c?.s = i)')!.node as NullabilityNodeForLUB;
    expect(lubNode.left, same(decoratedTypeAnnotation('C c').node));
    expect(lubNode.right, same(decoratedTypeAnnotation('int i').node));
    assertEdge(lubNode, decoratedTypeAnnotation('int f').node, hard: false);
  }

  Future<void> test_assignmentExpression_setter_target_check() async {
    await analyze('''
class C {
  void set s(int value) {}
}
void f(C c, int i) {
  c.s = i;
}
''');
    assertNullCheck(checkExpression('c.s')!,
        assertEdge(decoratedTypeAnnotation('C c').node, never, hard: true));
  }

  @failingTest
  Future<void> test_awaitExpression_future_nonNullable() async {
    await analyze('''
Future<void> f() async {
  int x = await g();
}
Future<int> g() async => 3;
''');

    assertNoUpstreamNullability(decoratedTypeAnnotation('int').node);
  }

  @failingTest
  Future<void> test_awaitExpression_future_nullable() async {
    await analyze('''
Future<void> f() async {
  int x = await g();
}
Future<int> g() async => null;
''');

    assertNoUpstreamNullability(decoratedTypeAnnotation('int').node);
  }

  Future<void> test_awaitExpression_nonFuture() async {
    await analyze('''
Future<void> f() async {
  int x = await 3;
}
''');

    assertNoUpstreamNullability(decoratedTypeAnnotation('int').node);
  }

  Future<void> test_binaryExpression_ampersand_result_not_null() async {
    await analyze('''
int f(int i, int j) => i & j;
''');

    assertNoUpstreamNullability(decoratedTypeAnnotation('int f').node);
  }

  Future<void> test_binaryExpression_ampersandAmpersand() async {
    await analyze('''
bool f(bool i, bool j) => i && j;
''');

    assertNoUpstreamNullability(decoratedTypeAnnotation('bool i').node);
  }

  Future<void> test_binaryExpression_bar_result_not_null() async {
    await analyze('''
int f(int i, int j) => i | j;
''');

    assertNoUpstreamNullability(decoratedTypeAnnotation('int f').node);
  }

  Future<void> test_binaryExpression_barBar() async {
    await analyze('''
bool f(bool i, bool j) => i || j;
''');

    assertNoUpstreamNullability(decoratedTypeAnnotation('bool i').node);
  }

  Future<void> test_binaryExpression_caret_result_not_null() async {
    await analyze('''
int f(int i, int j) => i ^ j;
''');

    assertNoUpstreamNullability(decoratedTypeAnnotation('int f').node);
  }

  Future<void> test_binaryExpression_equal() async {
    await analyze('''
bool f(int i, int j) => i == j;
''');

    assertNoUpstreamNullability(decoratedTypeAnnotation('bool f').node);
  }

  Future<void> test_binaryExpression_equal_null() async {
    await analyze('''
void f(int i) {
  if (i == null) {
    g(i);
  } else {
    h(i);
  }
}
void g(int j) {}
void h(int k) {}
''');
    var iNode = decoratedTypeAnnotation('int i').node;
    var jNode = decoratedTypeAnnotation('int j').node;
    var kNode = decoratedTypeAnnotation('int k').node;
    // No edge from i to k because i is known to be non-nullable at the site of
    // the call to h()
    assertNoEdge(iNode, kNode);
    // But there is an edge from i to j
    assertEdge(iNode, jNode, hard: false, guards: [iNode]);
  }

  Future<void> test_binaryExpression_equal_null_null() async {
    await analyze('''
void f(int i) {
  if (null == null) {
    g(i);
  }
}
void g(int j) {}
''');
    var iNode = decoratedTypeAnnotation('int i').node;
    var jNode = decoratedTypeAnnotation('int j').node;
    assertEdge(iNode, jNode,
        hard: false,
        guards: TypeMatcher<Iterable<NullabilityNode?>>()
            .having((g) => g.single, 'single value', isIn(alwaysPlus)));
  }

  Future<void> test_binaryExpression_equal_null_yoda_condition() async {
    await analyze('''
void f(int i) {
  if (null == i) {
    g(i);
  } else {
    h(i);
  }
}
void g(int j) {}
void h(int k) {}
''');
    var iNode = decoratedTypeAnnotation('int i').node;
    var jNode = decoratedTypeAnnotation('int j').node;
    var kNode = decoratedTypeAnnotation('int k').node;
    // No edge from i to k because i is known to be non-nullable at the site of
    // the call to h()
    assertNoEdge(iNode, kNode);
    // But there is an edge from i to j
    assertEdge(iNode, jNode, hard: false, guards: [iNode]);
  }

  Future<void> test_binaryExpression_gt_result_not_null() async {
    await analyze('''
bool f(int i, int j) => i > j;
''');

    assertNoUpstreamNullability(decoratedTypeAnnotation('bool f').node);
  }

  Future<void> test_binaryExpression_gtEq_result_not_null() async {
    await analyze('''
bool f(int i, int j) => i >= j;
''');

    assertNoUpstreamNullability(decoratedTypeAnnotation('bool f').node);
  }

  Future<void> test_binaryExpression_gtGt_result_not_null() async {
    await analyze('''
int f(int i, int j) => i >> j;
''');

    assertNoUpstreamNullability(decoratedTypeAnnotation('int f').node);
  }

  Future<void> test_binaryExpression_left_dynamic() async {
    await analyze('''
Object f(dynamic x, int y) => x + g(y);
int g(int z) => z;
''');
    assertEdge(decoratedTypeAnnotation('int y').node,
        decoratedTypeAnnotation('int z').node,
        hard: true);
    assertNoEdge(decoratedTypeAnnotation('int g').node, anyNode);
    assertEdge(inSet(alwaysPlus), decoratedTypeAnnotation('Object f').node,
        hard: false);
  }

  Future<void> test_binaryExpression_lt_result_not_null() async {
    await analyze('''
bool f(int i, int j) => i < j;
''');

    assertNoUpstreamNullability(decoratedTypeAnnotation('bool f').node);
  }

  Future<void> test_binaryExpression_ltEq_result_not_null() async {
    await analyze('''
bool f(int i, int j) => i <= j;
''');

    assertNoUpstreamNullability(decoratedTypeAnnotation('bool f').node);
  }

  Future<void> test_binaryExpression_ltLt_result_not_null() async {
    await analyze('''
int f(int i, int j) => i << j;
''');

    assertNoUpstreamNullability(decoratedTypeAnnotation('int f').node);
  }

  Future<void> test_binaryExpression_minus_result_not_null() async {
    await analyze('''
int f(int i, int j) => i - j;
''');

    assertNoUpstreamNullability(decoratedTypeAnnotation('int f').node);
  }

  Future<void> test_binaryExpression_notEqual() async {
    await analyze('''
bool f(int i, int j) => i != j;
''');

    assertNoUpstreamNullability(decoratedTypeAnnotation('bool f').node);
  }

  Future<void> test_binaryExpression_notEqual_null() async {
    await analyze('''
void f(int i) {
  if (i != null) {
    h(i);
  } else {
    g(i);
  }
}
void g(int j) {}
void h(int k) {}
''');
    var iNode = decoratedTypeAnnotation('int i').node;
    var jNode = decoratedTypeAnnotation('int j').node;
    var kNode = decoratedTypeAnnotation('int k').node;
    // No edge from i to k because i is known to be non-nullable at the site of
    // the call to h()
    assertNoEdge(iNode, kNode);
    // But there is an edge from i to j
    assertEdge(iNode, jNode, hard: false, guards: [iNode]);
  }

  Future<void> test_binaryExpression_percent_result_not_null() async {
    await analyze('''
int f(int i, int j) => i % j;
''');

    assertNoUpstreamNullability(decoratedTypeAnnotation('int f').node);
  }

  Future<void> test_binaryExpression_plus_left_check() async {
    await analyze('''
int f(int i, int j) => i + j;
''');

    assertNullCheck(checkExpression('i +')!,
        assertEdge(decoratedTypeAnnotation('int i').node, never, hard: true));
  }

  Future<void> test_binaryExpression_plus_left_check_custom() async {
    await analyze('''
class Int {
  Int operator+(Int other) => this;
}
Int f(Int i, Int j) => i + j;
''');

    assertNullCheck(checkExpression('i +')!,
        assertEdge(decoratedTypeAnnotation('Int i').node, never, hard: true));
  }

  Future<void> test_binaryExpression_plus_result_custom() async {
    await analyze('''
class Int {
  Int operator+(Int other) => this;
}
Int f(Int i, Int j) => (i + j);
''');

    assertNullCheck(
        checkExpression('(i + j)')!,
        assertEdge(decoratedTypeAnnotation('Int operator+').node,
            decoratedTypeAnnotation('Int f').node,
            hard: false));
  }

  Future<void> test_binaryExpression_plus_result_not_null() async {
    await analyze('''
int f(int i, int j) => i + j;
''');

    assertNoUpstreamNullability(decoratedTypeAnnotation('int f').node);
  }

  Future<void> test_binaryExpression_plus_right_check() async {
    await analyze('''
int f(int i, int j) => i + j;
''');

    assertNullCheck(
        checkExpression('j;')!,
        assertEdge(decoratedTypeAnnotation('int j').node, inSet(pointsToNever),
            hard: true));
  }

  Future<void> test_binaryExpression_plus_right_check_custom() async {
    await analyze('''
class Int {
  Int operator+(Int other) => this;
}
Int f(Int i, Int j) => i + j/*check*/;
''');

    assertNullCheck(
        checkExpression('j/*check*/')!,
        assertEdge(decoratedTypeAnnotation('Int j').node,
            decoratedTypeAnnotation('Int other').node,
            hard: true));
  }

  Future<void> test_binaryExpression_plus_substituted() async {
    await analyze('''
class _C<T, U> {
  T operator+(U u) => throw 'foo';
}
Object _f(_C<int, String> c, String s) => c + s;
''');
    assertEdge(
        decoratedTypeAnnotation('String s').node,
        substitutionNode(decoratedTypeAnnotation('String>').node,
            decoratedTypeAnnotation('U u').node),
        hard: true);
    assertEdge(
        substitutionNode(decoratedTypeAnnotation('int,').node,
            decoratedTypeAnnotation('T operator').node),
        decoratedTypeAnnotation('Object _f').node,
        hard: false);
  }

  Future<void> test_binaryExpression_questionQuestion() async {
    await analyze('''
int f(int i, int j) => i ?? j;
''');

    var left = decoratedTypeAnnotation('int i').node;
    var right = decoratedTypeAnnotation('int j').node;
    var expression = decoratedExpressionType('??')!.node!;
    assertEdge(right, expression, guards: [left], hard: false);
    expect(expression.displayName, '?? operator (test.dart:1:24)');
  }

  Future<void>
      test_binaryExpression_questionQuestion_genericReturnType() async {
    await analyze('''
class C<E> {
  C<E> operator +(C<E> c) => this;
}
C<int> f(C<int> i, C<int> j) => i ?? j;
''');
  }

  Future<void> test_binaryExpression_right_dynamic() async {
    await analyze('''
class C {
  C operator+(C other) => other;
}
C f(C x, dynamic y) => x + y;
''');
    assertNullCheck(checkExpression('x +')!,
        assertEdge(decoratedTypeAnnotation('C x').node, never, hard: true));
    assertEdge(decoratedTypeAnnotation('C operator').node,
        decoratedTypeAnnotation('C f').node,
        hard: false);
  }

  Future<void> test_binaryExpression_slash_result_not_null() async {
    await analyze('''
double f(int i, int j) => i / j;
''');

    assertNoUpstreamNullability(decoratedTypeAnnotation('double f').node);
  }

  Future<void> test_binaryExpression_star_result_not_null() async {
    await analyze('''
int f(int i, int j) => i * j;
''');

    assertNoUpstreamNullability(decoratedTypeAnnotation('int f').node);
  }

  Future<void> test_binaryExpression_tildeSlash_result_not_null() async {
    await analyze('''
int f(int i, int j) => i ~/ j;
''');

    assertNoUpstreamNullability(decoratedTypeAnnotation('int f').node);
  }

  Future<void> test_boolLiteral() async {
    await analyze('''
bool f() {
  return true;
}
''');
    assertNoUpstreamNullability(decoratedTypeAnnotation('bool').node);
  }

  Future<void> test_cascadeExpression() async {
    await analyze('''
class C {
  int x = 0;
}
C f(C c, int i) => c..x = i;
''');
    assertEdge(decoratedTypeAnnotation('C c').node,
        decoratedTypeAnnotation('C f').node,
        hard: false);
  }

  Future<void> test_cast_type_used_as_non_nullable() async {
    await analyze('''
void f(int/*!*/ i) {}
void g(num/*?*/ j) {
  f(j as int);
}
''');
    assertEdge(decoratedTypeAnnotation('int)').node,
        decoratedTypeAnnotation('int/*!*/').node,
        hard: true);
  }

  Future<void> test_catch_clause() async {
    await analyze('''
foo() => 1;
main() {
  try { foo(); } on Exception catch (e) { print(e); }
}
''');
    // No assertions; just checking that it doesn't crash.
  }

  Future<void> test_catch_clause_no_type() async {
    await analyze('''
foo() => 1;
main() {
  try { foo(); } catch (e) { print(e); }
}
''');
    // No assertions; just checking that it doesn't crash.
  }

  Future<void>
      test_class_alias_synthetic_constructor_with_parameters_complex() async {
    await analyze('''
class MyList<T> {}
class C {
  C(MyList<int>/*1*/ x);
}
mixin M {}
class D = C with M;
D f(MyList<int>/*2*/ x) => D(x);
''');
    var syntheticConstructor = findElement.unnamedConstructor('D');
    var constructorType = variables!.decoratedElementType(syntheticConstructor);
    var constructorParameterType = constructorType.positionalParameters![0]!;
    assertEdge(decoratedTypeAnnotation('MyList<int>/*2*/').node,
        constructorParameterType.node,
        hard: true);
    assertEdge(decoratedTypeAnnotation('int>/*2*/').node,
        constructorParameterType.typeArguments[0]!.node,
        hard: true, checkable: false);
    assertUnion(constructorParameterType.node,
        decoratedTypeAnnotation('MyList<int>/*1*/').node);
    assertUnion(constructorParameterType.typeArguments[0]!.node,
        decoratedTypeAnnotation('int>/*1*/').node);
  }

  Future<void>
      test_class_alias_synthetic_constructor_with_parameters_generic() async {
    await analyze('''
class C<T> {
  C(T t);
}
mixin M {}
class D<U> = C<U> with M;
''');
    var syntheticConstructor = findElement.unnamedConstructor('D');
    var constructorType = variables!.decoratedElementType(syntheticConstructor);
    var constructorParameterType = constructorType.positionalParameters![0]!;
    assertUnion(
        constructorParameterType.node, decoratedTypeAnnotation('T t').node);
  }

  Future<void>
      test_class_alias_synthetic_constructor_with_parameters_named() async {
    await analyze('''
class C {
  C({int/*1*/ i});
}
mixin M {}
class D = C with M;
D f(int/*2*/ i) => D(i: i);
''');
    var syntheticConstructor = findElement.unnamedConstructor('D');
    var constructorType = variables!.decoratedElementType(syntheticConstructor);
    var constructorParameterType = constructorType.namedParameters!['i']!;
    assertEdge(
        decoratedTypeAnnotation('int/*2*/').node, constructorParameterType.node,
        hard: true);
    assertUnion(constructorParameterType.node,
        decoratedTypeAnnotation('int/*1*/').node);
  }

  Future<void>
      test_class_alias_synthetic_constructor_with_parameters_optional() async {
    await analyze('''
class C {
  C([int/*1*/ i]);
}
mixin M {}
class D = C with M;
D f(int/*2*/ i) => D(i);
''');
    var syntheticConstructor = findElement.unnamedConstructor('D');
    var constructorType = variables!.decoratedElementType(syntheticConstructor);
    var constructorParameterType = constructorType.positionalParameters![0]!;
    assertEdge(
        decoratedTypeAnnotation('int/*2*/').node, constructorParameterType.node,
        hard: true);
    assertUnion(constructorParameterType.node,
        decoratedTypeAnnotation('int/*1*/').node);
  }

  Future<void>
      test_class_alias_synthetic_constructor_with_parameters_required() async {
    await analyze('''
class C {
  C(int/*1*/ i);
}
mixin M {}
class D = C with M;
D f(int/*2*/ i) => D(i);
''');
    var syntheticConstructor = findElement.unnamedConstructor('D');
    var constructorType = variables!.decoratedElementType(syntheticConstructor);
    var constructorParameterType = constructorType.positionalParameters![0]!;
    assertEdge(
        decoratedTypeAnnotation('int/*2*/').node, constructorParameterType.node,
        hard: true);
    assertUnion(constructorParameterType.node,
        decoratedTypeAnnotation('int/*1*/').node);
  }

  Future<void> test_class_metadata() async {
    await analyze('''
@deprecated
class C {}
''');
    // No assertions needed; the AnnotationTracker mixin verifies that the
    // metadata was visited.
  }

  Future<void> test_conditionalExpression_condition_check() async {
    await analyze('''
int f(bool b, int i, int j) {
  return (b ? i : j);
}
''');

    var nullable_b = decoratedTypeAnnotation('bool b').node;
    var check_b = checkExpression('b ?')!;
    assertNullCheck(check_b, assertEdge(nullable_b, never, hard: true));
  }

  Future<void> test_conditionalExpression_false_guard() async {
    await analyze('int f(int x, int y, int z) => x != null ? null : y = z;');
    var guard = decoratedTypeAnnotation('int x').node;
    assertEdge(decoratedTypeAnnotation('int z').node,
        decoratedTypeAnnotation('int y').node,
        hard: false, guards: [guard]);
    var conditionalDiscard =
        variables!.conditionalDiscard(findNode.conditionalExpression('!='))!;
    expect(conditionalDiscard, isNotNull);
    expect(conditionalDiscard.trueGuard, isNull);
    expect(conditionalDiscard.falseGuard, same(guard));
  }

  Future<void> test_conditionalExpression_functionTyped_namedParameter() async {
    await analyze('''
void f(bool b, void Function({int p}) x, void Function({int p}) y) {
  (b ? x : y);
}
''');
    var xType =
        decoratedGenericFunctionTypeAnnotation('void Function({int p}) x');
    var yType =
        decoratedGenericFunctionTypeAnnotation('void Function({int p}) y');
    var resultType = decoratedExpressionType('(b ?')!;
    assertLUB(resultType.node!, xType.node, yType.node);
    assertGLB(resultType.namedParameters!['p']!.node,
        xType.namedParameters!['p']!.node, yType.namedParameters!['p']!.node);
  }

  Future<void>
      test_conditionalExpression_functionTyped_normalParameter() async {
    await analyze('''
void f(bool b, void Function(int) x, void Function(int) y) {
  (b ? x : y);
}
''');
    var xType = decoratedGenericFunctionTypeAnnotation('void Function(int) x');
    var yType = decoratedGenericFunctionTypeAnnotation('void Function(int) y');
    var resultType = decoratedExpressionType('(b ?')!;
    assertLUB(resultType.node!, xType.node, yType.node);
    assertGLB(
        resultType.positionalParameters![0]!.node,
        xType.positionalParameters![0]!.node,
        yType.positionalParameters![0]!.node);
  }

  Future<void>
      test_conditionalExpression_functionTyped_normalParameters() async {
    await analyze('''
void f(bool b, void Function(int, int) x, void Function(int, int) y) {
  (b ? x : y);
}
''');
    var xType =
        decoratedGenericFunctionTypeAnnotation('void Function(int, int) x');
    var yType =
        decoratedGenericFunctionTypeAnnotation('void Function(int, int) y');
    var resultType = decoratedExpressionType('(b ?')!;
    assertLUB(resultType.node!, xType.node, yType.node);
    assertGLB(
        resultType.positionalParameters![0]!.node,
        xType.positionalParameters![0]!.node,
        yType.positionalParameters![0]!.node);
    assertGLB(
        resultType.positionalParameters![1]!.node,
        xType.positionalParameters![1]!.node,
        yType.positionalParameters![1]!.node);
  }

  Future<void>
      test_conditionalExpression_functionTyped_optionalParameter() async {
    await analyze('''
void f(bool b, void Function([int]) x, void Function([int]) y) {
  (b ? x : y);
}
''');
    var xType =
        decoratedGenericFunctionTypeAnnotation('void Function([int]) x');
    var yType =
        decoratedGenericFunctionTypeAnnotation('void Function([int]) y');
    var resultType = decoratedExpressionType('(b ?')!;
    assertLUB(resultType.node!, xType.node, yType.node);
    assertGLB(
        resultType.positionalParameters![0]!.node,
        xType.positionalParameters![0]!.node,
        yType.positionalParameters![0]!.node);
  }

  Future<void> test_conditionalExpression_functionTyped_returnType() async {
    await analyze('''
void f(bool b, int Function() x, int Function() y) {
  (b ? x : y);
}
''');
    var xType = decoratedGenericFunctionTypeAnnotation('int Function() x');
    var yType = decoratedGenericFunctionTypeAnnotation('int Function() y');
    var resultType = decoratedExpressionType('(b ?')!;
    assertLUB(resultType.node!, xType.node, yType.node);
    assertLUB(resultType.returnType!.node!, xType.returnType!.node,
        yType.returnType!.node);
  }

  Future<void>
      test_conditionalExpression_functionTyped_returnType_void() async {
    await analyze('''
void f(bool b, void Function() x, void Function() y) {
  (b ? x : y);
}
''');
    var xType = decoratedGenericFunctionTypeAnnotation('void Function() x');
    var yType = decoratedGenericFunctionTypeAnnotation('void Function() y');
    var resultType = decoratedExpressionType('(b ?')!;
    assertLUB(resultType.node!, xType.node, yType.node);
    expect(resultType.returnType!.node!.isImmutable, false);
  }

  Future<void> test_conditionalExpression_general() async {
    await analyze('''
int f(bool b, int i, int j) {
  return (b ? i : j);
}
''');

    var nullable_i = decoratedTypeAnnotation('int i').node;
    var nullable_j = decoratedTypeAnnotation('int j').node;
    var nullable_conditional = decoratedExpressionType('(b ?')!.node!;
    assertLUB(nullable_conditional, nullable_i, nullable_j);
    var nullable_return = decoratedTypeAnnotation('int f').node;
    assertNullCheck(checkExpression('(b ? i : j)')!,
        assertEdge(nullable_conditional, nullable_return, hard: false));
  }

  Future<void> test_conditionalExpression_generic() async {
    await analyze('''
void f(bool b, Map<int, String> x, Map<int, String> y) {
  (b ? x : y);
}
''');
    var xType = decoratedTypeAnnotation('Map<int, String> x');
    var yType = decoratedTypeAnnotation('Map<int, String> y');
    var resultType = decoratedExpressionType('(b ?')!;
    assertLUB(resultType.node!, xType.node, yType.node);
    assertLUB(resultType.typeArguments[0]!.node!, xType.typeArguments[0]!.node,
        yType.typeArguments[0]!.node);
    assertLUB(resultType.typeArguments[1]!.node!, xType.typeArguments[1]!.node,
        yType.typeArguments[1]!.node);
  }

  Future<void> test_conditionalExpression_generic_lub() async {
    await analyze('''
class A<T> {}
class B<T> extends A<T/*b*/> {}
class C<T> extends A<T/*c*/> {}
A<num> f(bool b, B<num> x, C<num> y) {
  return (b ? x : y);
}
''');
    var bType = decoratedTypeAnnotation('B<num> x');
    var cType = decoratedTypeAnnotation('C<num> y');
    var bInA = decoratedTypeAnnotation('T/*b*/');
    var cInA = decoratedTypeAnnotation('T/*c*/');
    var resultType = decoratedExpressionType('(b ?')!;
    assertLUB(resultType.node!, bType.node, cType.node);
    assertLUB(
        resultType.typeArguments[0]!.node!,
        substitutionNode(bType.typeArguments[0]!.node, bInA.node),
        substitutionNode(cType.typeArguments[0]!.node, cInA.node));
  }

  Future<void> test_conditionalExpression_generic_lub_leftSubtype() async {
    await analyze('''
class A<T> {}
class B<T> extends A<T/*b*/> {}
A<num> f(bool b, B<num> x, A<num> y) {
  return (b ? x : y);
}
''');
    var aType = decoratedTypeAnnotation('A<num> y');
    var bType = decoratedTypeAnnotation('B<num> x');
    var bInA = decoratedTypeAnnotation('T/*b*/');
    var resultType = decoratedExpressionType('(b ?')!;
    assertLUB(resultType.node!, bType.node, aType.node);
    assertLUB(
        resultType.typeArguments[0]!.node!,
        substitutionNode(bType.typeArguments[0]!.node, bInA.node),
        aType.typeArguments[0]!.node);
  }

  Future<void> test_conditionalExpression_generic_lub_rightSubtype() async {
    await analyze('''
class A<T> {}
class B<T> extends A<T/*b*/> {}
A<num> f(bool b, A<num> x, B<num> y) {
  return (b ? x : y);
}
''');
    var aType = decoratedTypeAnnotation('A<num> x');
    var bType = decoratedTypeAnnotation('B<num> y');
    var bInA = decoratedTypeAnnotation('T/*b*/');
    var resultType = decoratedExpressionType('(b ?')!;
    assertLUB(resultType.node!, aType.node, bType.node);
    assertLUB(resultType.typeArguments[0]!.node!, aType.typeArguments[0]!.node,
        substitutionNode(bType.typeArguments[0]!.node, bInA.node));
  }

  Future<void> test_conditionalExpression_generic_typeParameter_bound() async {
    await analyze('''
List<num> f<T extends List<num>>(bool b, List<num> x, T y) {
  return (b ? x : y);
}
''');
    var aType = decoratedTypeAnnotation('List<num> x');
    var bType = decoratedTypeAnnotation('T y');
    var bBound = decoratedTypeAnnotation('List<num>>');
    var resultType = decoratedExpressionType('(b ?')!;
    assertLUB(resultType.node!, aType.node,
        substitutionNode(bBound.node, bType.node));
    assertLUB(resultType.typeArguments[0]!.node!, aType.typeArguments[0]!.node,
        bBound.typeArguments[0]!.node);
  }

  Future<void> test_conditionalExpression_left_never() async {
    await analyze('''
List<int> f(bool b, List<int> i) {
  return (b ? (throw i) : i);
}
''');

    var nullable_i = decoratedTypeAnnotation('List<int> i').node;
    var nullable_conditional =
        decoratedExpressionType('(b ?')!.node as NullabilityNodeForLUB;
    var nullable_throw = nullable_conditional.left;
    assertNoUpstreamNullability(nullable_throw);
    assertLUB(nullable_conditional, nullable_throw, nullable_i);
  }

  Future<void> test_conditionalExpression_left_non_null() async {
    await analyze('''
int f(bool b, int i) {
  return (b ? (throw i) : i);
}
''');

    var nullable_i = decoratedTypeAnnotation('int i').node;
    var nullable_conditional =
        decoratedExpressionType('(b ?')!.node as NullabilityNodeForLUB;
    var nullable_throw = nullable_conditional.left;
    assertNoUpstreamNullability(nullable_throw);
    assertLUB(nullable_conditional, nullable_throw, nullable_i);
  }

  Future<void> test_conditionalExpression_left_null() async {
    await analyze('''
int f(bool b, int i) {
  return (b ? null : i);
}
''');

    var nullable_i = decoratedTypeAnnotation('int i').node;
    var nullable_conditional = decoratedExpressionType('(b ?')!.node!;
    assertLUB(nullable_conditional, inSet(alwaysPlus), nullable_i);
  }

  Future<void> test_conditionalExpression_left_null_right_function() async {
    await analyze('''
bool Function<T>(int) g(bool b, bool Function<T>(int) f) {
  return (b ? null : f);
}
''');

    var nullable_i =
        decoratedGenericFunctionTypeAnnotation('bool Function<T>(int) f').node;
    var nullable_conditional = decoratedExpressionType('(b ?')!.node!;
    assertLUB(nullable_conditional, inSet(alwaysPlus), nullable_i);
  }

  Future<void>
      test_conditionalExpression_left_null_right_parameterType() async {
    await analyze('''
T g<T>(bool b, T t) {
  return (b ? null : t);
}
''');

    var nullable_t = decoratedTypeAnnotation('T t').node;
    var nullable_conditional = decoratedExpressionType('(b ?')!.node!;
    assertLUB(nullable_conditional, inSet(alwaysPlus), nullable_t);
  }

  Future<void> test_conditionalExpression_left_null_right_typeArgs() async {
    await analyze('''
List<int> f(bool b, List<int> l) {
  return (b ? null : l);
}
''');

    var nullable_i = decoratedTypeAnnotation('List<int> l').node;
    var nullable_conditional = decoratedExpressionType('(b ?')!.node!;
    assertLUB(nullable_conditional, inSet(alwaysPlus), nullable_i);
  }

  Future<void> test_conditionalExpression_nullTyped_nullParameter() async {
    await analyze('''
void f(bool b, void Function(Null p) x, void Function(List<int> p) y) {
  (b ? x : y);
}
''');
    var xType =
        decoratedGenericFunctionTypeAnnotation('void Function(Null p) x');
    var yType =
        decoratedGenericFunctionTypeAnnotation('void Function(List<int> p) y');
    var resultType = decoratedExpressionType('(b ?')!;
    assertLUB(resultType.node!, xType.node, yType.node);
    assertGLB(
        resultType.positionalParameters![0]!.node,
        xType.positionalParameters![0]!.node,
        yType.positionalParameters![0]!.node);
  }

  Future<void> test_conditionalExpression_parameterType() async {
    await analyze('''
T g<T>(bool b, T x, T y) {
  return (b ? x : y);
}
''');

    var nullable_x = decoratedTypeAnnotation('T x').node;
    var nullable_y = decoratedTypeAnnotation('T y').node;
    var nullable_conditional = decoratedExpressionType('(b ?')!.node!;
    assertLUB(nullable_conditional, nullable_x, nullable_y);
  }

  Future<void> test_conditionalExpression_right_never() async {
    await analyze('''
List<int> f(bool b, List<int> i) {
  return (b ? i : (throw i));
}
''');

    var nullable_i = decoratedTypeAnnotation('List<int> i').node;
    var nullable_conditional =
        decoratedExpressionType('(b ?')!.node as NullabilityNodeForLUB;
    var nullable_throw = nullable_conditional.right;
    assertNoUpstreamNullability(nullable_throw);
    assertLUB(nullable_conditional, nullable_i, nullable_throw);
  }

  Future<void> test_conditionalExpression_right_non_null() async {
    await analyze('''
int f(bool b, int i) {
  return (b ? i : (throw i));
}
''');

    var nullable_i = decoratedTypeAnnotation('int i').node;
    var nullable_conditional =
        decoratedExpressionType('(b ?')!.node as NullabilityNodeForLUB;
    var nullable_throw = nullable_conditional.right;
    assertNoUpstreamNullability(nullable_throw);
    assertLUB(nullable_conditional, nullable_i, nullable_throw);
  }

  Future<void> test_conditionalExpression_right_null() async {
    await analyze('''
int f(bool b, int i) {
  return (b ? i : null);
}
''');

    var nullable_i = decoratedTypeAnnotation('int i').node;
    var nullable_conditional = decoratedExpressionType('(b ?')!.node!;
    assertLUB(nullable_conditional, nullable_i, inSet(alwaysPlus));
  }

  Future<void> test_conditionalExpression_right_null_left_function() async {
    await analyze('''
bool Function<T>(int) g(bool b, bool Function<T>(int) f) {
  return (b ? f : null);
}
''');

    var nullable_i =
        decoratedGenericFunctionTypeAnnotation('bool Function<T>(int) f').node;
    var nullable_conditional = decoratedExpressionType('(b ?')!.node!;
    assertLUB(nullable_conditional, nullable_i, inSet(alwaysPlus));
  }

  Future<void> test_conditionalExpression_right_null_left_typeArgs() async {
    await analyze('''
List<int> f(bool b, List<int> l) {
  return (b ? l : null);
}
''');

    var nullable_i = decoratedTypeAnnotation('List<int> l').node;
    var nullable_conditional = decoratedExpressionType('(b ?')!.node!;
    assertLUB(nullable_conditional, nullable_i, inSet(alwaysPlus));
  }

  Future<void>
      test_conditionalExpression_right_null_left_typeParameter() async {
    await analyze('''
T f<T>(bool b, T t) {
  return (b ? t : null);
}
''');

    var nullable_t = decoratedTypeAnnotation('T t').node;
    var nullable_conditional = decoratedExpressionType('(b ?')!.node!;
    assertLUB(nullable_conditional, nullable_t, inSet(alwaysPlus));
  }

  Future<void> test_conditionalExpression_true_guard() async {
    await analyze('int f(int x, int y, int z) => x == null ? y = z : null;');
    var guard = decoratedTypeAnnotation('int x').node;
    assertEdge(decoratedTypeAnnotation('int z').node,
        decoratedTypeAnnotation('int y').node,
        hard: false, guards: [guard]);
    var conditionalDiscard =
        variables!.conditionalDiscard(findNode.conditionalExpression('=='))!;
    expect(conditionalDiscard, isNotNull);
    expect(conditionalDiscard.trueGuard, same(guard));
    expect(conditionalDiscard.falseGuard, isNull);
  }

  Future<void> test_conditionalExpression_typeParameter_bound() async {
    await analyze('''
num f<T extends num>(bool b, num x, T y) {
  return (b ? x : y);
}
''');
    var aType = decoratedTypeAnnotation('num x');
    var bType = decoratedTypeAnnotation('T y');
    var bBound = decoratedTypeAnnotation('num>');
    var resultType = decoratedExpressionType('(b ?')!;
    assertLUB(resultType.node!, aType.node,
        substitutionNode(bBound.node, bType.node));
  }

  Future<void> test_conditionalExpression_typeParameter_bound_bound() async {
    await analyze('''
num f<T extends R, R extends num>(bool b, num x, T y) {
  return (b ? x : y);
}
''');
    var aType = decoratedTypeAnnotation('num x');
    var bType = decoratedTypeAnnotation('T y');
    var bBound = decoratedTypeAnnotation('R,');
    var bBoundBound = decoratedTypeAnnotation('num>');
    var resultType = decoratedExpressionType('(b ?')!;
    assertLUB(
        resultType.node!,
        aType.node,
        substitutionNode(
            bBoundBound.node, substitutionNode(bBound.node, bType.node)));
  }

  Future<void> test_conditionalExpression_typeParameter_dynamic() async {
    // "dynamic" can short circuit LUB, incorrectly we may lose nullabilities.
    await analyze('''
dynamic f<T extends num>(bool b, dynamic x, T y) {
  return (b ? x : y);
}
''');
    var aType = decoratedTypeAnnotation('dynamic x');
    var bType = decoratedTypeAnnotation('T y');
    var bBound = decoratedTypeAnnotation('num>');
    var resultType = decoratedExpressionType('(b ?')!;
    assertLUB(resultType.node!, aType.node,
        substitutionNode(bBound.node, bType.node));
  }

  Future<void> test_conditionalExpression_typeParameters_bound() async {
    await analyze('''
num f<T extends num, R extends num>(bool b, R x, T y) {
  return (b ? x : y);
}
''');
    var aType = decoratedTypeAnnotation('R x');
    var bType = decoratedTypeAnnotation('T y');
    var aBound = decoratedTypeAnnotation('num>');
    var bBound = decoratedTypeAnnotation('num,');
    var resultType = decoratedExpressionType('(b ?')!;
    assertLUB(resultType.node!, substitutionNode(aBound.node, aType.node),
        substitutionNode(bBound.node, bType.node));
  }

  Future<void>
      test_conditionalExpression_typeParameters_bound_left_to_right() async {
    await analyze('''
R f<T extends R, R>(bool b, R x, T y) {
  return (b ? x : y);
}
''');
    var aType = decoratedTypeAnnotation('R x');
    var bType = decoratedTypeAnnotation('T y');
    var bBound = decoratedTypeAnnotation('R,');
    var resultType = decoratedExpressionType('(b ?')!;
    assertLUB(resultType.node!, aType.node,
        substitutionNode(bBound.node, bType.node));
  }

  Future<void> test_constructor_default_parameter_value_bool() async {
    await analyze('''
class C {
  C([bool b = true]);
}
''');
    assertNoUpstreamNullability(decoratedTypeAnnotation('bool b').node);
  }

  Future<void> test_constructor_named() async {
    await analyze('''
class C {
  C.named();
}
''');
    // No assertions; just need to make sure that the test doesn't cause an
    // exception to be thrown.
  }

  Future<void> test_constructor_superInitializer() async {
    await analyze('''
class C {
  C.named(int i);
}
class D extends C {
  D(int j) : super.named(j);
}
''');

    var namedConstructor = findElement.constructor('named', of: 'C');
    var constructorType = variables!.decoratedElementType(namedConstructor);
    var constructorParameterType = constructorType.positionalParameters![0]!;
    assertEdge(
        decoratedTypeAnnotation('int j').node, constructorParameterType.node,
        hard: true);
  }

  Future<void> test_constructor_superInitializer_withTypeArgument() async {
    await analyze('''
class C<T> {
  C.named(T/*1*/ i);
}
class D extends C<int/*2*/> {
  D(int/*3*/ j) : super.named(j);
}
''');

    var nullable_t1 = decoratedTypeAnnotation('T/*1*/').node;
    var nullable_int2 = decoratedTypeAnnotation('int/*2*/').node;
    var nullable_int3 = decoratedTypeAnnotation('int/*3*/').node;
    assertEdge(nullable_int3, substitutionNode(nullable_int2, nullable_t1),
        hard: true);
  }

  Future<void> test_constructor_superInitializer_withTypeVariable() async {
    await analyze('''
class C<T> {
  C.named(T/*1*/ i);
}
class D<U> extends C<U/*2*/> {
  D(U/*3*/ j) : super.named(j);
}
''');

    var nullable_t1 = decoratedTypeAnnotation('T/*1*/').node;
    var nullable_u2 = decoratedTypeAnnotation('U/*2*/').node;
    var nullable_u3 = decoratedTypeAnnotation('U/*3*/').node;
    assertEdge(nullable_u3, substitutionNode(nullable_u2, nullable_t1),
        hard: true);
  }

  Future<void> test_constructorDeclaration_returnType_generic() async {
    await analyze('''
class C<T, U> {
  C();
}
''');
    var constructor = findElement.unnamedConstructor('C');
    var constructorDecoratedType = variables!.decoratedElementType(constructor);
    _assertType(constructorDecoratedType.type!, 'C<T, U> Function()');
    expect(constructorDecoratedType.node, same(never));
    expect(constructorDecoratedType.typeFormals, isEmpty);
    expect(constructorDecoratedType.returnType!.node, same(never));
    _assertType(constructorDecoratedType.returnType!.type!, 'C<T, U>');
    var typeArguments = constructorDecoratedType.returnType!.typeArguments;
    expect(typeArguments, hasLength(2));
    _assertType(typeArguments[0]!.type!, 'T');
    expect(typeArguments[0]!.node, same(never));
    _assertType(typeArguments[1]!.type!, 'U');
    expect(typeArguments[1]!.node, same(never));
  }

  Future<void> test_constructorDeclaration_returnType_generic_implicit() async {
    await analyze('''
class C<T, U> {}
''');
    var constructor = findElement.unnamedConstructor('C');
    var constructorDecoratedType = variables!.decoratedElementType(constructor);
    _assertType(constructorDecoratedType.type!, 'C<T, U> Function()');
    expect(constructorDecoratedType.node, same(never));
    expect(constructorDecoratedType.typeFormals, isEmpty);
    expect(constructorDecoratedType.returnType!.node, same(never));
    _assertType(constructorDecoratedType.returnType!.type!, 'C<T, U>');
    var typeArguments = constructorDecoratedType.returnType!.typeArguments;
    expect(typeArguments, hasLength(2));
    _assertType(typeArguments[0]!.type!, 'T');
    expect(typeArguments[0]!.node, same(never));
    _assertType(typeArguments[1]!.type!, 'U');
    expect(typeArguments[1]!.node, same(never));
  }

  Future<void> test_constructorDeclaration_returnType_simple() async {
    await analyze('''
class C {
  C();
}
''');
    var constructorDecoratedType =
        variables!.decoratedElementType(findElement.unnamedConstructor('C'));
    _assertType(constructorDecoratedType.type!, 'C Function()');
    expect(constructorDecoratedType.node, same(never));
    expect(constructorDecoratedType.typeFormals, isEmpty);
    expect(constructorDecoratedType.returnType!.node, same(never));
    expect(constructorDecoratedType.returnType!.typeArguments, isEmpty);
  }

  Future<void> test_constructorDeclaration_returnType_simple_implicit() async {
    await analyze('''
class C {}
''');
    var constructorDecoratedType =
        variables!.decoratedElementType(findElement.unnamedConstructor('C'));
    _assertType(constructorDecoratedType.type!, 'C Function()');
    expect(constructorDecoratedType.node, same(never));
    expect(constructorDecoratedType.typeFormals, isEmpty);
    expect(constructorDecoratedType.returnType!.node, same(never));
    expect(constructorDecoratedType.returnType!.typeArguments, isEmpty);
  }

  Future<void> test_constructorFieldInitializer_generic() async {
    await analyze('''
class C<T> {
  C(T/*1*/ x) : f = x;
  T/*2*/ f;
}
''');
    assertEdge(decoratedTypeAnnotation('T/*1*/').node,
        decoratedTypeAnnotation('T/*2*/').node,
        hard: true);
  }

  Future<void> test_constructorFieldInitializer_simple() async {
    await analyze('''
class C {
  C(int/*1*/ i) : f = i;
  int/*2*/ f;
}
''');
    assertEdge(decoratedTypeAnnotation('int/*1*/').node,
        decoratedTypeAnnotation('int/*2*/').node,
        hard: true);
  }

  Future<void> test_constructorFieldInitializer_via_this() async {
    await analyze('''
class C {
  C(int/*1*/ i) : this.f = i;
  int/*2*/ f;
}
''');
    assertEdge(decoratedTypeAnnotation('int/*1*/').node,
        decoratedTypeAnnotation('int/*2*/').node,
        hard: true);
  }

  Future<void> test_do_while_condition() async {
    await analyze('''
void f(bool b) {
  do {} while (b);
}
''');

    assertNullCheck(checkExpression('b);')!,
        assertEdge(decoratedTypeAnnotation('bool b').node, never, hard: true));
  }

  Future<void> test_doubleLiteral() async {
    await analyze('''
double f() {
  return 1.0;
}
''');
    assertNoUpstreamNullability(decoratedTypeAnnotation('double').node);
  }

  Future<void> test_dummyNode_fromEqualityComparison_left() async {
    await analyze('''
f() {
  int i;
  if (i == 7) {}
}
''');
    var nullable_i = decoratedTypeAnnotation('int i').node;
    assertDummyEdge(nullable_i);
  }

  Future<void> test_dummyNode_fromEqualityComparison_right() async {
    await analyze('''
f() {
  int i;
  if (7 == i) {}
}
''');
    var nullable_i = decoratedTypeAnnotation('int i').node;
    assertDummyEdge(nullable_i);
  }

  Future<void> test_dummyNode_fromExpressionStatement() async {
    await analyze('''
f() {
  int i;
  i;
}
''');
    var nullable_i = decoratedTypeAnnotation('int i').node;
    assertDummyEdge(nullable_i);
  }

  Future<void> test_dummyNode_fromForLoopUpdaters() async {
    await analyze('''
f() {
  int i;
  int j;
  for (;; i, j) {}
}
''');
    var nullable_i = decoratedTypeAnnotation('int i').node;
    var nullable_j = decoratedTypeAnnotation('int j').node;
    assertDummyEdge(nullable_i);
    assertDummyEdge(nullable_j);
  }

  Future<void> test_dummyNode_fromForLoopVariables() async {
    await analyze('''
f() {
  int i;
  for (i;;) {}
}
''');
    var nullable_i = decoratedTypeAnnotation('int i').node;
    assertDummyEdge(nullable_i);
  }

  Future<void> test_edgeOrigin_call_from_function() async {
    await analyze('''
void f(int i) {}
void g(int j) {
  f(j);
}
''');
    assertEdge(decoratedTypeAnnotation('int j').node,
        decoratedTypeAnnotation('int i').node,
        hard: true,
        codeReference:
            matchCodeRef(offset: findNode.simple('j);').offset, function: 'g'));
  }

  Future<void> test_edgeOrigin_call_from_method() async {
    await analyze('''
class C {
  void f(int i) {}
  void g(int j) {
    f(j);
  }
}
''');
    assertEdge(decoratedTypeAnnotation('int j').node,
        decoratedTypeAnnotation('int i').node,
        hard: true,
        codeReference: matchCodeRef(
            offset: findNode.simple('j);').offset, function: 'C.g'));
  }

  Future<void> test_export_metadata() async {
    await analyze('''
@deprecated
export 'dart:async';
''');
    // No assertions needed; the AnnotationTracker mixin verifies that the
    // metadata was visited.
  }

  Future<void> test_extension_metadata() async {
    await analyze('''
@deprecated
extension E on String {}
''');
    // No assertions needed; the AnnotationTracker mixin verifies that the
    // metadata was visited.
  }

  Future<void> test_extension_on_class_with_generic_type_arguments() async {
    await analyze('''
class C<T> {}
void f(C<List> x) {}
extension E on C<List> {
  g() => f(this);
}
''');
    // No assertions yet. This test crashes. When it stops crashing, consider
    // adding assertion(s).
  }

  Future<void> test_extension_on_function_type() async {
    await analyze('''
extension CurryFunction<R, S, T> on R Function(S, T) {
  /// Curry a binary function with its first argument.
  R Function(T) curry(S first) => (T second) => this(first, second);
}
''');
    // No assertions yet. This test crashes. When it stops crashing, consider
    // adding assertion(s).
  }

  Future<void> test_extension_this_non_null_intent_explicit_direct() async {
    await analyze('''
extension on int {
  f() => g(this);
}
void g(int i) {}
''');
    assertEdge(decoratedTypeAnnotation('int {').node,
        decoratedTypeAnnotation('int i').node,
        hard: true);
  }

  Future<void> test_extension_this_non_null_intent_explicit_method() async {
    await analyze('''
extension on int {
  f() => this.abs();
}
''');
    assertEdge(decoratedTypeAnnotation('int').node, never, hard: true);
  }

  Future<void>
      test_extension_this_non_null_intent_explicit_property_get() async {
    await analyze('''
extension on int {
  f() => this.isEven;
}
''');
    assertEdge(decoratedTypeAnnotation('int').node, never, hard: true);
  }

  Future<void>
      test_extension_this_non_null_intent_explicit_property_set() async {
    await analyze('''
class C {
  int x;
}
extension on C /*reference*/ {
  f() {
    this.x = 0;
  }
}
''');
    assertEdge(decoratedTypeAnnotation('C /*reference*/').node, never,
        hard: true);
  }

  Future<void> test_extension_this_non_null_intent_implicit_method() async {
    await analyze('''
extension on int {
  f() => abs();
}
''');
    assertEdge(decoratedTypeAnnotation('int').node, never, hard: true);
  }

  Future<void> test_extension_this_non_null_intent_implicit_property() async {
    await analyze('''
extension on int {
  f() => isEven;
}
''');
    assertEdge(decoratedTypeAnnotation('int').node, never, hard: true);
  }

  Future<void>
      test_extension_this_non_null_intent_implicit_property_set() async {
    await analyze('''
class C {
  int x;
}
extension on C /*reference*/ {
  f() {
    x = 0;
  }
}
''');
    assertEdge(decoratedTypeAnnotation('C /*reference*/').node, never,
        hard: true);
  }

  Future<void> test_field_final_does_not_override_setter() async {
    await analyze('''
abstract class A {
  void set i(int value);
}
abstract class C implements A {
  final int i;
  C(this.i);
}
''');
    var baseNode = decoratedTypeAnnotation('int value').node;
    var derivedNode = decoratedTypeAnnotation('int i').node;
    assertNoEdge(derivedNode, baseNode);
    assertNoEdge(baseNode, derivedNode);
  }

  Future<void> test_field_initialized_in_constructor() async {
    await analyze('''
class C {
  int i;
  C() : i = 0;
}
''');
    // There is no edge from always to the type of i, because it is initialized
    // in the constructor.
    assertNoEdge(always, decoratedTypeAnnotation('int').node);
  }

  Future<void> test_field_metadata() async {
    await analyze('''
class A {
  const A();
}
class C {
  @A()
  int f;
}
''');
    // No assertions needed; the AnnotationTracker mixin verifies that the
    // metadata was visited.
  }

  Future<void> test_field_overrides_field() async {
    await analyze('''
abstract class A {
  int i; // A
}
class C implements A {
  int i; // C
}
''');
    var baseNode = decoratedTypeAnnotation('int i; // A').node;
    var derivedNode = decoratedTypeAnnotation('int i; // C').node;
    assertEdge(baseNode, derivedNode, hard: true);
    assertEdge(derivedNode, baseNode, hard: true);
  }

  Future<void> test_field_overrides_field_final() async {
    await analyze('''
abstract class A {
  final int i; // A
  A(this.i);
}
class C implements A {
  int i; // C
}
''');
    var baseNode = decoratedTypeAnnotation('int i; // A').node;
    var derivedNode = decoratedTypeAnnotation('int i; // C').node;
    assertEdge(derivedNode, baseNode, hard: true);
    assertNoEdge(baseNode, derivedNode);
  }

  Future<void> test_field_overrides_getter() async {
    await analyze('''
abstract class A {
  int get i;
}
class C implements A {
  int i;
}
''');
    var baseNode = decoratedTypeAnnotation('int get i').node;
    var derivedNode = decoratedTypeAnnotation('int i').node;
    assertEdge(derivedNode, baseNode, hard: true);
    assertNoEdge(baseNode, derivedNode);
  }

  Future<void> test_field_overrides_setter() async {
    await analyze('''
abstract class A {
  void set i(int value);
}
class C implements A {
  int i;
}
''');
    var baseNode = decoratedTypeAnnotation('int value').node;
    var derivedNode = decoratedTypeAnnotation('int i').node;
    assertEdge(baseNode, derivedNode, hard: true);
    assertNoEdge(derivedNode, baseNode);
  }

  Future<void> test_field_static_implicitInitializer() async {
    await analyze('''
class C {
  static int i;
}
''');
    assertEdge(always, decoratedTypeAnnotation('int').node, hard: false);
  }

  Future<void> test_field_type_inferred() async {
    await analyze('''
int f() => 1;
class C {
  var x = f();