pkg/analyzer/lib/src/error/literal_element_verifier.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/element/type.dart';
import 'package:analyzer/dart/element/type_provider.dart';
import 'package:analyzer/src/dart/ast/ast.dart';
import 'package:analyzer/src/dart/ast/extensions.dart';
import 'package:analyzer/src/dart/element/type.dart';
import 'package:analyzer/src/dart/element/type_system.dart';
import 'package:analyzer/src/diagnostic/diagnostic.dart' as diag;
import 'package:analyzer/src/error/listener.dart';
import 'package:analyzer/src/generated/error_verifier.dart';

/// Verifier for [CollectionElement]s in list, set, or map literals.
class LiteralElementVerifier {
  final TypeProvider typeProvider;
  final TypeSystemImpl typeSystem;
  final DiagnosticReporter _diagnosticReporter;
  final FeatureSet featureSet;
  final ErrorVerifier _errorVerifier;

  final bool forList;
  final bool forSet;
  final TypeImpl? elementType;

  final bool forMap;
  final TypeImpl? mapKeyType;
  final TypeImpl? mapValueType;

  LiteralElementVerifier(
    this.typeProvider,
    this.typeSystem,
    this._diagnosticReporter,
    this._errorVerifier, {
    this.forList = false,
    this.forSet = false,
    this.elementType,
    this.forMap = false,
    this.mapKeyType,
    this.mapValueType,
    required this.featureSet,
  });

  bool get _strictCasts => _errorVerifier.options.strictCasts;

  void verify(CollectionElement element) {
    _verifyElement(element as CollectionElementImpl);
  }

  /// Check that the given [type] is assignable to the [elementType], otherwise
  /// report the list or set error on the [errorNode].
  void _checkAssignableToElementType(TypeImpl type, AstNode errorNode) {
    var elementType = this.elementType;

    if (!typeSystem.isAssignableTo(
      type,
      elementType!,
      strictCasts: _strictCasts,
    )) {
      bool assignableWhenNullable = typeSystem.isAssignableTo(
        type,
        typeSystem.makeNullable(elementType),
        strictCasts: _strictCasts,
      );
      var errorCode = switch ((
        forList: forList,
        assignableWhenNullable: assignableWhenNullable,
      )) {
        (forList: false, assignableWhenNullable: false) =>
          diag.setElementTypeNotAssignable,
        (forList: false, assignableWhenNullable: true) =>
          diag.setElementTypeNotAssignableNullability,
        (forList: true, assignableWhenNullable: false) =>
          diag.listElementTypeNotAssignable,
        (forList: true, assignableWhenNullable: true) =>
          diag.listElementTypeNotAssignableNullability,
      };
      _diagnosticReporter.report(
        errorCode
            .withArguments(actualType: type, expectedType: elementType)
            .at(errorNode),
      );
    }
  }

  /// Verify that the given [element] can be assigned to the [elementType] of
  /// the enclosing list, set, of map literal.
  void _verifyElement(CollectionElementImpl? element) {
    switch (element) {
      case ExpressionImpl():
        if (forList || forSet) {
          if (elementType is! VoidType &&
              _errorVerifier.checkForUseOfVoidResult(element)) {
            return;
          }
          _checkAssignableToElementType(element.typeOrThrow, element);
        } else {
          _diagnosticReporter.report(diag.expressionInMap.at(element));
        }
      case ForElementImpl():
        _verifyElement(element.body2);
      case IfElementImpl():
        _verifyElement(element.thenElement2);
        _verifyElement(element.elseElement2);
      case MapLiteralEntryImpl():
        if (forMap) {
          _verifyMapLiteralEntry(element);
        } else {
          _diagnosticReporter.report(diag.mapEntryNotInMap.at(element));
        }
      case SpreadElementImpl():
        var isNullAware = element.isNullAware;
        Expression expression = element.expression2;
        if (forList || forSet) {
          _verifySpreadForListOrSet(isNullAware, expression);
        } else if (forMap) {
          _verifySpreadForMap(isNullAware, expression);
        }
      case NullAwareElementImpl():
        if (forList || forSet) {
          var valueType = element.value2.typeOrThrow;
          // A null-aware marker tests this expression for `null`, so a `void`
          // value is used even when the stored element type is also `void`.
          if (valueType is VoidType) {
            _errorVerifier.checkForUseOfVoidResult(element.value2);
            return;
          }
          _checkAssignableToElementType(
            typeSystem.promoteToNonNull(valueType),
            element,
          );
        } else {
          _diagnosticReporter.report(diag.expressionInMap.at(element));
        }
      case null:
        break;
    }
  }

  /// Verify that the [entry]'s key and value are assignable to [mapKeyType]
  /// and [mapValueType].
  void _verifyMapLiteralEntry(MapLiteralEntry entry) {
    var mapKeyType = this.mapKeyType!;
    var keyType = entry.key2.typeOrThrow;

    // A null-aware marker tests this expression for `null`, so a `void` value
    // is used even when the stored key type is also `void`.
    if (entry.keyQuestion != null && keyType is VoidType) {
      _errorVerifier.checkForUseOfVoidResult(entry.key2);
      return;
    }

    if (mapKeyType is! VoidType &&
        _errorVerifier.checkForUseOfVoidResult(entry.key2)) {
      return;
    }

    var mapValueType = this.mapValueType!;
    var valueType = entry.value2.typeOrThrow;

    // A null-aware marker tests this expression for `null`, so a `void` value
    // is used even when the stored value type is also `void`.
    if (entry.valueQuestion != null && valueType is VoidType) {
      _errorVerifier.checkForUseOfVoidResult(entry.value2);
      return;
    }

    if (mapValueType is! VoidType &&
        _errorVerifier.checkForUseOfVoidResult(entry.value2)) {
      return;
    }

    // If the key is null-aware, the entry is only added when the key is not
    // `null`, so the key type to check should be promoted to non-null.
    if (entry.keyQuestion != null) {
      keyType = typeSystem.promoteToNonNull(keyType);
    }
    if (!typeSystem.isAssignableTo(
      keyType,
      mapKeyType,
      strictCasts: _strictCasts,
    )) {
      if (entry.keyQuestion == null &&
          typeSystem.isAssignableTo(
            keyType,
            typeSystem.makeNullable(mapKeyType),
            strictCasts: _strictCasts,
          )) {
        _diagnosticReporter.report(
          diag.mapKeyTypeNotAssignableNullability
              .withArguments(actualType: keyType, expectedType: mapKeyType)
              .at(entry.key2),
        );
      } else {
        _diagnosticReporter.report(
          diag.mapKeyTypeNotAssignable
              .withArguments(actualType: keyType, expectedType: mapKeyType)
              .at(entry.key2),
        );
      }
    }

    // If the value is null-aware, the entry is only added when the value is not
    // `null`, so the value type to check should be promoted to non-null.
    if (entry.valueQuestion != null) {
      valueType = typeSystem.promoteToNonNull(valueType);
    }
    if (!typeSystem.isAssignableTo(
      valueType,
      mapValueType,
      strictCasts: _strictCasts,
    )) {
      if (entry.valueQuestion == null &&
          typeSystem.isAssignableTo(
            valueType,
            typeSystem.makeNullable(mapValueType),
            strictCasts: _strictCasts,
          )) {
        _diagnosticReporter.report(
          diag.mapValueTypeNotAssignableNullability
              .withArguments(actualType: valueType, expectedType: mapValueType)
              .at(entry.value2),
        );
      } else {
        _diagnosticReporter.report(
          diag.mapValueTypeNotAssignable
              .withArguments(actualType: valueType, expectedType: mapValueType)
              .at(entry.value2),
        );
      }
    }
  }

  /// Verify that the type of the elements of the given [expression] can be
  /// assigned to the [elementType] of the enclosing collection.
  void _verifySpreadForListOrSet(bool isNullAware, Expression expression) {
    var expressionType = expression.typeOrThrow;
    if (expressionType is DynamicType) {
      if (_errorVerifier.strictCasts) {
        _diagnosticReporter.report(diag.notIterableSpread.at(expression));
      }
      return;
    }

    if (typeSystem.isSubtypeOf(expressionType, NeverTypeImpl.instance)) {
      return;
    }

    if (typeSystem.isSubtypeOf(expressionType, typeSystem.nullNone)) {
      if (isNullAware) {
        return;
      }
      _diagnosticReporter.report(diag.notNullAwareNullSpread.at(expression));
      return;
    }

    var iterableType = expressionType.asInstanceOf(
      typeProvider.iterableElement,
    );

    if (iterableType == null) {
      _diagnosticReporter.report(diag.notIterableSpread.at(expression));
      return;
    }

    var iterableElementType = iterableType.typeArguments[0];
    var elementType = this.elementType;
    if (!typeSystem.isAssignableTo(
      iterableElementType,
      elementType!,
      strictCasts: _strictCasts,
    )) {
      var errorCode = forList
          ? diag.listElementTypeNotAssignable
          : diag.setElementTypeNotAssignable;
      // Also check for an "implicit tear-off conversion" which would be applied
      // after desugaring a spread element.
      var implicitCallMethod = _errorVerifier.getImplicitCallMethod(
        iterableElementType,
        elementType,
        expression,
      );
      if (implicitCallMethod == null) {
        _diagnosticReporter.report(
          errorCode
              .withArguments(
                actualType: iterableElementType,
                expectedType: elementType,
              )
              .at(expression),
        );
      } else {
        var tearoffType = implicitCallMethod.type;
        if (featureSet.isEnabled(Feature.constructor_tearoffs)) {
          var typeArguments = typeSystem.inferFunctionTypeInstantiation(
            elementType as FunctionTypeImpl,
            tearoffType,
            diagnosticReporter: _diagnosticReporter,
            errorNode: expression,
            genericMetadataIsEnabled: true,
            inferenceUsingBoundsIsEnabled: featureSet.isEnabled(
              Feature.inference_using_bounds,
            ),
            strictInference: _errorVerifier.options.strictInference,
            strictCasts: _errorVerifier.options.strictCasts,
            typeSystemOperations: _errorVerifier.typeSystemOperations,
            dataForTesting: null,
            nodeForTesting: null,
          );
          if (typeArguments.isNotEmpty) {
            tearoffType = tearoffType.instantiate(typeArguments);
          }
        }

        if (!typeSystem.isAssignableTo(
          tearoffType,
          elementType,
          strictCasts: _strictCasts,
        )) {
          _diagnosticReporter.report(
            errorCode
                .withArguments(
                  actualType: iterableElementType,
                  expectedType: elementType,
                )
                .at(expression),
          );
        }
      }
    }
  }

  /// Verify that the [expression] is a subtype of `Map<Object, Object>`, and
  /// its key and values are assignable to [mapKeyType] and [mapValueType].
  void _verifySpreadForMap(bool isNullAware, Expression expression) {
    var expressionType = expression.typeOrThrow;
    if (expressionType is DynamicType) {
      if (_errorVerifier.strictCasts) {
        _diagnosticReporter.report(diag.notMapSpread.at(expression));
      }
      return;
    }

    if (typeSystem.isSubtypeOf(expressionType, NeverTypeImpl.instance)) {
      return;
    }

    if (typeSystem.isSubtypeOf(expressionType, typeSystem.nullNone)) {
      if (isNullAware) {
        return;
      }
      _diagnosticReporter.report(diag.notNullAwareNullSpread.at(expression));
      return;
    }

    var mapType = expressionType.asInstanceOf(typeProvider.mapElement);

    if (mapType == null) {
      _diagnosticReporter.report(diag.notMapSpread.at(expression));
      return;
    }

    var keyType = mapType.typeArguments[0];
    var mapKeyType = this.mapKeyType;
    if (!typeSystem.isAssignableTo(
      keyType,
      mapKeyType!,
      strictCasts: _strictCasts,
    )) {
      _diagnosticReporter.report(
        diag.mapKeyTypeNotAssignable
            .withArguments(actualType: keyType, expectedType: mapKeyType)
            .at(expression),
      );
    }

    var valueType = mapType.typeArguments[1];
    var mapValueType = this.mapValueType;
    if (!typeSystem.isAssignableTo(
      valueType,
      mapValueType!,
      strictCasts: _strictCasts,
    )) {
      _diagnosticReporter.report(
        diag.mapValueTypeNotAssignable
            .withArguments(actualType: valueType, expectedType: mapValueType)
            .at(expression),
      );
    }
  }
}