https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88557
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |c++-lambda, rejects-valid
Last reconfirmed|2021-08-07 00:00:00 |2024-4-13
--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Now we are rejecting this valid C++17 code:
```
template<int = []()constexpr{ return 0; }()>
void f() { }
```
With:
```
<source>:3:21: error: lambda-expression in template-argument only available
with '-std=c++2a' or '-std=gnu++2a'
3 | template<int = []()constexpr{ return 0; }()>
| ^
```
Because I would have assumed calling a constexpr lambda would be a valid C++17
code.
We even reject this and cause an ICE:
```
template<int = [](auto)constexpr{ return 0; }.operator()(1)>
void f() { }
```
But those examples are all valid C++17 due to constexpr'ness.
