[cfe-dev] Diagnosing initialization of deprecated data member?

[Stephan Bergmann via cfe-dev]

For

> $ cat test.cc
> struct S {
>     int x;
>     [[deprecated]] int y;
> };
> int main() {
>     S s{0, 0};
> }

Clang emits a diagnostic

> $ clang++ test.cc
> test.cc:6:12: warning: 'y' is deprecated [-Wdeprecated-declarations]
>     S s{0, 0};
>            ^
> test.cc:3:7: note: 'y' has been explicitly marked deprecated here
>     [[deprecated]] int y;
>       ^
> 1 warning generated.

while e.g. GCC and MSVC do not (as checked with godbolt.org).

Is this deliberate behavior on Clang's part, or just a consequence of 
how the code happens to work?  Are there opinions on whether or not the 
behavior is useful?

(I came across this issue when seeing a commit in LibreOffice where some

> #pragma GCC diagnostic ignored "-Wdeprecated-declarations"

were added apparently to silence exactly the above situation in code 
initializing a PyTypeObject struct from 
/usr/include/python3.8/cpython/object.h, not even realizing that that 
pragma would only be needed by Clang and not by GCC.

FWIW, the standard's recommended practice is "to produce a diagnostic 
message in case the program refers to a name or entity other than to 
declare it", [dcl.attr.deprecated]/4.)