Method eval

source/ast/builtins/StringMethods.cpp:89–101

        upper(upper) {}

    ConstantValue eval(EvalContext& context, const Args& args, SourceRange,
                       const CallExpression::SystemCallInfo&) const final {
        auto val = args[0]->eval(context);
        if (!val)
            return nullptr;

        std::string& str = val.str();
        if (upper)
            strToUpper(str);
        else
            strToLower(str);
        return val;
    }

private:
    bool upper;