sebastienros.jint/Jint/Runtime/Interpreter/Expressions/JintUpdateExpression.cs

using Esprima.Ast;
using Jint.Native;
using Jint.Runtime.Environments;
using Jint.Runtime.References;

namespace Jint.Runtime.Interpreter.Expressions
{
    internal sealed class JintUpdateExpression : JintExpression
    {
        private JintExpression _argument;
        private int _change;
        private bool _prefix;

        private JintIdentifierExpression _leftIdentifier;
        private bool _evalOrArguments;

        public JintUpdateExpression(UpdateExpression expression) : base(expression)
        {
            _initialized = false;
        }

        protected override void Initialize(EvaluationContext context)
        {
            var expression = (UpdateExpression) _expression;
            _prefix = expression.Prefix;
            _argument = Build(context.Engine, expression.Argument);
            if (expression.Operator == UnaryOperator.Increment)
            {
                _change = 1;
            }
            else if (expression.Operator == UnaryOperator.Decrement)
            {
                _change = -1;
            }
            else
            {
                ExceptionHelper.ThrowArgumentException();
            }

            _leftIdentifier = _argument as JintIdentifierExpression;
            _evalOrArguments = _leftIdentifier?.HasEvalOrArguments == true;
        }

        protected override ExpressionResult EvaluateInternal(EvaluationContext context)
        {
            var fastResult = _leftIdentifier != null
                ? UpdateIdentifier(context)
                : null;

            return NormalCompletion(fastResult ?? UpdateNonIdentifier(context));
        }

        private JsValue UpdateNonIdentifier(EvaluationContext context)
        {
            var engine = context.Engine;
            var reference = _argument.Evaluate(context).Value as Reference;
            if (reference is null)
            {
                ExceptionHelper.ThrowTypeError(engine.Realm, "Invalid left-hand side expression");
            }

            reference.AssertValid(engine.Realm);

            var value = engine.GetValue(reference, false);
            var isInteger = value._type == InternalTypes.Integer;

            JsValue newValue = null;

            var operatorOverloaded = false;
            if (context.OperatorOverloadingAllowed)
            {
                if (JintUnaryExpression.TryOperatorOverloading(context, _argument.GetValue(context).Value, _change > 0 ? "op_Increment" : "op_Decrement", out var result))
                {
                    operatorOverloaded = true;
                    newValue = result;
                }
            }

            if (!operatorOverloaded)
            {
                newValue = isInteger
                    ? JsNumber.Create(value.AsInteger() + _change)
                    : JsNumber.Create(TypeConverter.ToNumber(value) + _change);
            }

            engine.PutValue(reference, newValue);
            engine._referencePool.Return(reference);

            return _prefix
                ? newValue
                : (isInteger || operatorOverloaded ? value : JsNumber.Create(TypeConverter.ToNumber(value)));
        }

        private JsValue UpdateIdentifier(EvaluationContext context)
        {
            var strict = StrictModeScope.IsStrictModeCode;
            var name = _leftIdentifier._expressionName;
            var engine = context.Engine;
            var env = engine.ExecutionContext.LexicalEnvironment;
            if (JintEnvironment.TryGetIdentifierEnvironmentWithBindingValue(
                engine,
                env,
                name,
                strict,
                out var environmentRecord,
                out var value))
            {
                if (strict && _evalOrArguments)
                {
                    ExceptionHelper.ThrowSyntaxError(engine.Realm);
                }

                var isInteger = value._type == InternalTypes.Integer;

                JsValue newValue = null;

                var operatorOverloaded = false;
                if (context.OperatorOverloadingAllowed)
                {
                    if (JintUnaryExpression.TryOperatorOverloading(context, _argument.GetValue(context).Value, _change > 0 ? "op_Increment" : "op_Decrement", out var result))
                    {
                        operatorOverloaded = true;
                        newValue = result;
                    }
                }

                if (!operatorOverloaded)
                {
                    newValue = isInteger
                    ? JsNumber.Create(value.AsInteger() + _change)
                    : JsNumber.Create(TypeConverter.ToNumber(value) + _change);
                }

                environmentRecord.SetMutableBinding(name.Key.Name, newValue, strict);
                return _prefix
                    ? newValue
                    : (isInteger || operatorOverloaded ? value : JsNumber.Create(TypeConverter.ToNumber(value)));
            }

            return null;
        }
    }
}