https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122568
--- Comment #1 from Vincent X <gulackeg at gmail dot com> ---
Another test case demonstrating GCC's different handling of
elaborated-type-specifiers in alias-declarations (with `using`) versus
simple-declarations (with `typedef`):
// https://godbolt.org/z/hKjhqx4T4
// ✔ - GCC:
// - warning: elaborated-type-specifier for a scoped enum must not
// use the 'class' keyword
// - error: use of enum 'E' without previous declaration
typedef enum class E E7; // #7
// ✗ - GCC: OK
using E8 = enum class E; // #8
// ✔ - GCC: warning: elaborated-type-specifier for a scoped enum must not
// use the 'class' keyword
typedef enum class E E9;
Specifically:
- #8 does not emit the warning for the non-standard usage of
`enum class E`, unlike #7.
- #8 introduces the name `E` into the containing scope automatically,
whereas #7 requires a forward declaration.
