pkg/analyzer/lib/src/dart/resolver/prefix_expression_resolver.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/ast/ast.dart';
import 'package:analyzer/dart/ast/token.dart';
import 'package:analyzer/dart/element/element.dart';
import 'package:analyzer/dart/element/type.dart';
import 'package:analyzer/dart/element/type_provider.dart';
import 'package:analyzer/error/listener.dart';
import 'package:analyzer/src/dart/ast/ast.dart';
import 'package:analyzer/src/dart/element/type.dart';
import 'package:analyzer/src/dart/resolver/assignment_expression_resolver.dart';
import 'package:analyzer/src/dart/resolver/flow_analysis_visitor.dart';
import 'package:analyzer/src/dart/resolver/invocation_inference_helper.dart';
import 'package:analyzer/src/dart/resolver/resolution_result.dart';
import 'package:analyzer/src/dart/resolver/type_property_resolver.dart';
import 'package:analyzer/src/error/codes.dart';
import 'package:analyzer/src/generated/resolver.dart';
import 'package:analyzer/src/generated/type_system.dart';
import 'package:analyzer/src/task/strong/checker.dart';
import 'package:meta/meta.dart';

/// Helper for resolving [PrefixExpression]s.
class PrefixExpressionResolver {
  final ResolverVisitor _resolver;
  final FlowAnalysisHelper _flowAnalysis;
  final TypePropertyResolver _typePropertyResolver;
  final InvocationInferenceHelper _inferenceHelper;
  final AssignmentExpressionShared _assignmentShared;

  PrefixExpressionResolver({
    @required ResolverVisitor resolver,
    @required FlowAnalysisHelper flowAnalysis,
  })  : _resolver = resolver,
        _flowAnalysis = flowAnalysis,
        _typePropertyResolver = resolver.typePropertyResolver,
        _inferenceHelper = resolver.inferenceHelper,
        _assignmentShared = AssignmentExpressionShared(
          resolver: resolver,
          flowAnalysis: flowAnalysis,
        );

  ErrorReporter get _errorReporter => _resolver.errorReporter;

  bool get _isNonNullableByDefault => _typeSystem.isNonNullableByDefault;

  TypeProvider get _typeProvider => _resolver.typeProvider;

  TypeSystemImpl get _typeSystem => _resolver.typeSystem;

  void resolve(PrefixExpressionImpl node) {
    var operator = node.operator.type;
    if (operator == TokenType.BANG) {
      _resolveNegation(node);
      return;
    }

    node.operand.accept(_resolver);

    _assignmentShared.checkLateFinalAlreadyAssigned(node.operand);

    _resolve1(node);
    _resolve2(node);
  }

  /// Check that the result [type] of a prefix or postfix `++` or `--`
  /// expression is assignable to the write type of the [operand].
  ///
  /// TODO(scheglov) this is duplicate
  void _checkForInvalidAssignmentIncDec(
      AstNode node, Expression operand, DartType type) {
    var operandWriteType = _getStaticType(operand);
    if (!_typeSystem.isAssignableTo(type, operandWriteType)) {
      _resolver.errorReporter.reportErrorForNode(
        StaticTypeWarningCode.INVALID_ASSIGNMENT,
        node,
        [type, operandWriteType],
      );
    }
  }

  /// Compute the static return type of the method or function represented by the given element.
  ///
  /// @param element the element representing the method or function invoked by the given node
  /// @return the static return type that was computed
  ///
  /// TODO(scheglov) this is duplicate
  DartType _computeStaticReturnType(Element element) {
    if (element is PropertyAccessorElement) {
      //
      // This is a function invocation expression disguised as something else.
      // We are invoking a getter and then invoking the returned function.
      //
      FunctionType propertyType = element.type;
      if (propertyType != null) {
        return _resolver.inferenceHelper.computeInvokeReturnType(
            propertyType.returnType,
            isNullAware: false);
      }
    } else if (element is ExecutableElement) {
      return _resolver.inferenceHelper
          .computeInvokeReturnType(element.type, isNullAware: false);
    }
    return DynamicTypeImpl.instance;
  }

  /// Return the name of the method invoked by the given postfix [expression].
  String _getPrefixOperator(PrefixExpression expression) {
    var operator = expression.operator;
    var operatorType = operator.type;
    if (operatorType == TokenType.PLUS_PLUS) {
      return TokenType.PLUS.lexeme;
    } else if (operatorType == TokenType.MINUS_MINUS) {
      return TokenType.MINUS.lexeme;
    } else if (operatorType == TokenType.MINUS) {
      return "unary-";
    } else {
      return operator.lexeme;
    }
  }

  /// Return the static type of the given [expression] that is to be used for
  /// type analysis.
  ///
  /// TODO(scheglov) this is duplicate
  DartType _getStaticType(Expression expression, {bool read = false}) {
    if (read) {
      var type = getReadType(
        expression,
      );
      return _resolveTypeParameter(type);
    } else {
      if (expression is SimpleIdentifier && expression.inSetterContext()) {
        var element = expression.staticElement;
        if (element is PromotableElement) {
          // We're writing to the element so ignore promotions.
          return element.type;
        } else {
          return expression.staticType;
        }
      } else {
        return expression.staticType;
      }
    }
  }

  /// Return the non-nullable variant of the [type] if NNBD is enabled, otherwise
  /// return the type itself.
  ///
  /// TODO(scheglov) this is duplicate
  DartType _nonNullable(DartType type) {
    if (_isNonNullableByDefault) {
      return _typeSystem.promoteToNonNull(type);
    }
    return type;
  }

  /// Record that the static type of the given node is the given type.
  ///
  /// @param expression the node whose type is to be recorded
  /// @param type the static type of the node
  ///
  /// TODO(scheglov) this is duplicate
  void _recordStaticType(Expression expression, DartType type) {
    _inferenceHelper.recordStaticType(expression, type);
  }

  void _resolve1(PrefixExpressionImpl node) {
    Token operator = node.operator;
    TokenType operatorType = operator.type;
    if (operatorType.isUserDefinableOperator ||
        operatorType.isIncrementOperator) {
      Expression operand = node.operand;
      String methodName = _getPrefixOperator(node);
      if (operand is ExtensionOverride) {
        ExtensionElement element = operand.extensionName.staticElement;
        MethodElement member = element.getMethod(methodName);
        if (member == null) {
          _errorReporter.reportErrorForToken(
              CompileTimeErrorCode.UNDEFINED_EXTENSION_OPERATOR,
              node.operator,
              [methodName, element.name]);
        }
        node.staticElement = member;
        return;
      }
      DartType staticType = _getStaticType(operand, read: true);

      if (identical(staticType, NeverTypeImpl.instance)) {
        _resolver.errorReporter.reportErrorForNode(
          HintCode.RECEIVER_OF_TYPE_NEVER,
          operand,
        );
        return;
      }

      var result = _typePropertyResolver.resolve(
        receiver: operand,
        receiverType: staticType,
        name: methodName,
        receiverErrorNode: operand,
        nameErrorNode: operand,
      );
      node.staticElement = result.getter;
      if (_shouldReportInvalidMember(staticType, result)) {
        if (operand is SuperExpression) {
          _errorReporter.reportErrorForToken(
            StaticTypeWarningCode.UNDEFINED_SUPER_OPERATOR,
            operator,
            [methodName, staticType],
          );
        } else {
          _errorReporter.reportErrorForToken(
            StaticTypeWarningCode.UNDEFINED_OPERATOR,
            operator,
            [methodName, staticType],
          );
        }
      }
    }
  }

  void _resolve2(PrefixExpressionImpl node) {
    TokenType operator = node.operator.type;
    if (identical(node.operand.staticType, NeverTypeImpl.instance)) {
      _recordStaticType(node, NeverTypeImpl.instance);
    } else {
      // The other cases are equivalent to invoking a method.
      ExecutableElement staticMethodElement = node.staticElement;
      DartType staticType = _computeStaticReturnType(staticMethodElement);
      Expression operand = node.operand;
      if (operand is ExtensionOverride) {
        // No special handling for incremental operators.
      } else if (operator.isIncrementOperator) {
        var operandReadType = _getStaticType(operand, read: true);
        if (operandReadType.isDartCoreInt) {
          staticType = _nonNullable(_typeProvider.intType);
        } else {
          _checkForInvalidAssignmentIncDec(node, operand, staticType);
        }
        if (operand is SimpleIdentifier) {
          var element = operand.staticElement;
          if (element is PromotableElement) {
            _flowAnalysis?.flow?.write(element, staticType);
          }
        }
      }
      _recordStaticType(node, staticType);
    }
  }

  void _resolveNegation(PrefixExpressionImpl node) {
    var operand = node.operand;
    InferenceContext.setType(operand, _typeProvider.boolType);

    operand.accept(_resolver);
    operand = node.operand;

    _resolver.boolExpressionVerifier.checkForNonBoolNegationExpression(operand);

    _recordStaticType(node, _nonNullable(_typeProvider.boolType));

    _flowAnalysis?.flow?.logicalNot_end(node, operand);
  }

  /// If the given [type] is a type parameter, resolve it to the type that should
  /// be used when looking up members. Otherwise, return the original type.
  ///
  /// TODO(scheglov) this is duplicate
  DartType _resolveTypeParameter(DartType type) =>
      type?.resolveToBound(_typeProvider.objectType);

  /// Return `true` if we should report an error for the lookup [result] on
  /// the [type].
  ///
  /// TODO(scheglov) this is duplicate
  bool _shouldReportInvalidMember(DartType type, ResolutionResult result) {
    if (result.isNone && type != null && !type.isDynamic) {
      if (_typeSystem.isNonNullableByDefault &&
          _typeSystem.isPotentiallyNullable(type)) {
        return false;
      }
      return true;
    }
    return false;
  }
}