[Bug c++/109781] [11/12/13/14 Regression] erroneous error "lambda-expression in template parameter type" for tparam lambda returning a lambda

[johelegp at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109781

--- Comment #5 from Johel Ernesto Guerrero Peña <johelegp at gmail dot com> ---
Add `+` to convert it to a pointer,
and it's still rejected (<https://compiler-explorer.com/z/PMras4rzd>):

```C++
template <auto A = +[]{ return []{}; }>
struct C {};
```

```output
<source>: In lambda function:
<source>:1:32: error: lambda-expression in template parameter type
    1 | template <auto A = +[]{ return []{}; }>
      |                                ^
Compiler returned: 1
```