CheckMakeAnUnboxOperation.cs

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using AST;
using ErrorManagement;
using System;

namespace AST.Operations {
    internal class CheckMakeAnUnboxOperation : AstOperation {

        private TypeSystem.MethodType methodType;

        public CheckMakeAnUnboxOperation() {
            this.methodType = null;
        }

        public override object Exec(BaseCallExpression b, object arg) {
            this.CheckActualMethodCalled(b);
            return this.ReturnValue(b);
        }
        public override object Exec(Expression node, object arg) {
            return this.ReturnValue(node);
        }

        private bool ReturnValue(Expression expression) {
            if (this.methodType != null)
                return !(this.methodType.Return.IsValueType());

            TypeSystem.FieldType field = expression.ExpressionType as TypeSystem.FieldType;

            if (field != null)
                return (field.FieldTypeExpression is TypeSystem.TypeVariable);

            return false;

        }

        protected void CheckActualMethodCalled(BaseCallExpression bc) {
            this.methodType = bc.ActualMethodCalled as TypeSystem.MethodType;
            if (this.methodType == null) {  // ActualMethodCalled is a TypeVariable or UnionType
                TypeSystem.TypeVariable typeVariable = bc.ActualMethodCalled as TypeSystem.TypeVariable;
                if (typeVariable != null)
                    this.methodType = typeVariable.Substitution as TypeSystem.MethodType;
            }
        }

    }
}