This example:

struct S {
    int x = 42;
    /* not constexpr */ ~S() { }
};

consteval auto make() -> S { return S(); }

int main() {
    S s = make();
}

When compiled with gcc 15.2 -std=c++26 produces this diagnostic:

<source>: In function 'int main()':
<source>:10:15: error: call to consteval function 'make()' is not a constant expression
   10 |     S s = make();
      |           ~~~~^~
<source>:10:15: error: 'consteval S make()' called in a constant expression
<source>:7:16: note: 'consteval S make()' is not usable as a 'constexpr' function because:
    7 | consteval auto make() -> S { return S(); }
      |                ^~~~

It's not usable as a constexpr function because... why? Can we get a hint?