pkg/analyzer/lib/src/dart/resolver/invocation_inference_helper.dart

// Copyright (c) 2020, 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/element/element.dart';
import 'package:analyzer/dart/element/nullability_suffix.dart';
import 'package:analyzer/dart/element/type.dart';
import 'package:analyzer/error/listener.dart';
import 'package:analyzer/src/dart/ast/ast.dart';
import 'package:analyzer/src/dart/element/element.dart';
import 'package:analyzer/src/dart/element/member.dart';
import 'package:analyzer/src/dart/element/type.dart';
import 'package:analyzer/src/dart/element/type_constraint_gatherer.dart';
import 'package:analyzer/src/dart/element/type_system.dart';
import 'package:analyzer/src/dart/resolver/invocation_inferrer.dart';
import 'package:analyzer/src/generated/resolver.dart';

/// Information about a constructor element to instantiate.
///
/// If the target is a [ClassElement], the [element] is a raw
/// [ConstructorElement] from the class, and [typeParameters] are the
/// type parameters of the class.
///
/// If the target is a [TypeAliasElement] with an [InterfaceType] as the
/// aliased type, the [element] is a [SubstitutedConstructorElementImpl] created from the
/// [ConstructorElement] of the corresponding class, and substituting
/// the class type parameters with the type arguments specified in the alias,
/// explicit types or the type parameters of the alias. The [typeParameters]
/// are the type parameters of the alias.
class ConstructorElementToInfer {
  /// The type parameters used in [element].
  final List<TypeParameterElementImpl> typeParameters;

  /// The element, might be [SubstitutedConstructorElementImpl].
  final InternalConstructorElement element;

  ConstructorElementToInfer(this.typeParameters, this.element);

  /// Return the equivalent generic function type that we could use to
  /// forward to the constructor, or for a non-generic type simply returns
  /// the constructor type.
  ///
  /// For example given the type `class C<T> { C(T arg); }`, the generic
  /// function type is `<T>(T) -> C<T>`.
  FunctionType get asType {
    return typeParameters.isEmpty
        ? element.type
        : FunctionTypeImpl.v2(
          typeParameters: typeParameters,
          formalParameters: element.formalParameters,
          returnType: element.returnType,
          nullabilitySuffix: NullabilitySuffix.none,
        );
  }
}

class InvocationInferenceHelper {
  final ResolverVisitor _resolver;
  final DiagnosticReporter _diagnosticReporter;
  final TypeSystemImpl _typeSystem;
  final bool _genericMetadataIsEnabled;
  final TypeConstraintGenerationDataForTesting? dataForTesting;

  InvocationInferenceHelper({
    required ResolverVisitor resolver,
    required DiagnosticReporter diagnosticReporter,
    required TypeSystemImpl typeSystem,
    required this.dataForTesting,
  }) : _resolver = resolver,
       _diagnosticReporter = diagnosticReporter,
       _typeSystem = typeSystem,
       _genericMetadataIsEnabled = resolver.definingLibrary.featureSet
           .isEnabled(Feature.generic_metadata);

  /// If the constructor referenced by the [constructorName] is generic,
  /// and the [constructorName] does not have explicit type arguments,
  /// return the element and type parameters to infer. Otherwise return `null`.
  ConstructorElementToInfer? constructorElementToInfer({
    required Element? typeElement,
    required SimpleIdentifierImpl? constructorName,
    required LibraryElementImpl definingLibrary,
  }) {
    List<TypeParameterElementImpl> typeParameters;
    InternalConstructorElement? rawElement;

    if (typeElement is InterfaceElementImpl) {
      typeParameters = typeElement.typeParameters;
      var constructorIdentifier = constructorName;
      if (constructorIdentifier == null) {
        rawElement = typeElement.unnamedConstructor;
      } else {
        var name = constructorIdentifier.name;
        rawElement = typeElement.getNamedConstructor(name);
        if (rawElement != null && !rawElement.isAccessibleIn(definingLibrary)) {
          rawElement = null;
        }
      }
    } else if (typeElement is TypeAliasElementImpl) {
      typeParameters = typeElement.typeParameters;
      var aliasedType = typeElement.aliasedType;
      if (aliasedType is InterfaceTypeImpl) {
        var constructorIdentifier = constructorName;
        rawElement = aliasedType.lookUpConstructor(
          constructorIdentifier?.name,
          definingLibrary,
        );
      }
    } else {
      return null;
    }

    if (rawElement == null) {
      return null;
    }
    return ConstructorElementToInfer(typeParameters, rawElement);
  }

  /// Given an uninstantiated generic function type, referenced by the
  /// [identifier] in the tear-off [expression], try to infer the instantiated
  /// generic function type from the surrounding context.
  DartType inferTearOff(
    ExpressionImpl expression,
    SimpleIdentifierImpl identifier,
    DartType tearOffType, {
    required DartType contextType,
  }) {
    if (contextType is FunctionTypeImpl && tearOffType is FunctionTypeImpl) {
      var typeArguments = _typeSystem.inferFunctionTypeInstantiation(
        contextType,
        tearOffType,
        diagnosticReporter: _diagnosticReporter,
        errorNode: expression,
        genericMetadataIsEnabled: _genericMetadataIsEnabled,
        inferenceUsingBoundsIsEnabled: _resolver.inferenceUsingBoundsIsEnabled,
        strictInference: _resolver.analysisOptions.strictInference,
        strictCasts: _resolver.analysisOptions.strictCasts,
        typeSystemOperations: _resolver.flowAnalysis.typeOperations,
        dataForTesting: dataForTesting,
        nodeForTesting: expression,
      );
      identifier.tearOffTypeArgumentTypes = typeArguments;
      if (typeArguments.isNotEmpty) {
        return tearOffType.instantiate(typeArguments);
      }
    }
    return tearOffType;
  }

  /// Finish resolution of the [DotShorthandInvocation].
  ///
  /// We have already found the invoked [ExecutableElement], and the [rawType]
  /// is its not yet instantiated type. Here we perform downwards inference,
  /// resolution of arguments, and upwards inference.
  void resolveDotShorthandInvocation({
    required DotShorthandInvocationImpl node,
    required FunctionTypeImpl rawType,
    required List<WhyNotPromotedGetter> whyNotPromotedArguments,
    required TypeImpl contextType,
  }) {
    var returnType = DotShorthandInvocationInferrer(
      resolver: _resolver,
      node: node,
      argumentList: node.argumentList,
      contextType: contextType,
      whyNotPromotedArguments: whyNotPromotedArguments,
    ).resolveInvocation(rawType: rawType);
    node.recordStaticType(returnType, resolver: _resolver);
  }

  /// Finish resolution of the [MethodInvocation].
  ///
  /// We have already found the invoked [ExecutableElement], and the [rawType]
  /// is its not yet instantiated type. Here we perform downwards inference,
  /// resolution of arguments, and upwards inference.
  void resolveMethodInvocation({
    required MethodInvocationImpl node,
    required FunctionTypeImpl rawType,
    required List<WhyNotPromotedGetter> whyNotPromotedArguments,
    required TypeImpl contextType,
  }) {
    var returnType = MethodInvocationInferrer(
      resolver: _resolver,
      node: node,
      argumentList: node.argumentList,
      contextType: contextType,
      whyNotPromotedArguments: whyNotPromotedArguments,
    ).resolveInvocation(rawType: rawType);
    node.recordStaticType(returnType, resolver: _resolver);
  }
}