https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102909
--- Comment #3 from Iru Cai <mytbk920423 at gmail dot com> ---
Looks like this kind of things are detected in the front-end. The GNAT
front-end can warn on the similar things:
procedure Main is
A : Integer;
B : constant Integer := 1;
begin
A := 0;
A := A + B;
end Main;
$ gcc -O2 -gnatwa -gnatwe -c main.adb
main.adb:6:09: warning: possibly useless assignment to "A", value might not be
referenced
