[Bug c/89888] [7/8/9 Regression] When switch controlling expression is promoted from type narrower than int, GCC does not diagnose identical cases

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89888

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 46100
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=46100&action=edit
gcc9-pr89888.patch

Untested fix.