https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119072
Bug ID: 119072
Summary: GCC rejects type declaration inside decltype specifier
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: tymi at tymi dot org
Target Milestone: ---
Declaring a type inside decltype causes GCC to error out
https://redirect.compiler.gg/cBNsuyog
It doesn't even work for forward declarations. GCC accepts type aliases though.
Sample code:
```cpp
// Compile with -std=c++23 -pedantic-errors
std::vector<decltype(([]{ enum struct X : unsigned char {}; return X{}; })())>
v1{}; // rejects
std::vector<decltype(([]{ using X = int; return X{}; })())> v2{}; // accepts
```
