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From: "netcan1996 at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c++/102229] [11/12 Regression] 'decltype(auto)' cannot be
 cv-qualified
Date: Thu, 09 Sep 2021 13:56:33 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102229

--- Comment #7 from Net Can <netcan1996 at gmail dot com> ---
here is my use case:
https://github.com/netcan/config-loader/blob/master/include/config-loader/s=
erialize/TypeSerializer.h

the key is
```c++
#define TYPE_SERIALIZER(_type, _typeName)                 \
    struct TypeSerializer<PARE _type>                     \
    { static constexpr decltype(auto) name =3D _typeName; }

template<> TYPE_SERIALIZER((int8_t), "int8_t"); // (1)

template<typename T>
TYPE_SERIALIZER((std::vector<T>),
                    concat("vector<", TypeSerializer<T>::name, ">")); // (2)
```

in case (1), the `name` type is `const char(&)[N]`, but in case(2), the `na=
me`
type is `array[N]`, so I use `decltype(auto)` rather `auto`, becase latter
loses char length info.

I tried `static decltype(auto)` not work because it is defined in class, and
requires `constexpr`.=