https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96593
Bug ID: 96593
Summary: No "declaration changes meaning" diagnostic for alias
templates
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Keywords: diagnostic
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: language.lawyer at gmail dot com
Target Milestone: ---
"A name N used in a class S shall refer to the same declaration in its context
and when re-evaluated in the completed scope of S. No diagnostic is required
for a violation of this rule."
The diagnostic for the rule is not required, but since GCC diagnoses some of
the cases, there is a bugreport about missing diagnostic cases (bug 46983), and
the check might become mandatory (will it?), I'd like file this bug.
GCC accepts the code with alias templates:
struct S {};
template <typename>
struct T {};
struct U
{
template<typename>
using S = S;
template<typename>
using T = T<void>;
};
but produces the "declaration changes meaning" error for type aliases.
GCC also diagnoses the case if the "outer" declaration is used before the
corresponding alias template:
struct S {};
struct U
{
S s;
template<typename>
using S = S; // error: declaration of ... changes meaning of 'S'
};
(From https://stackoverflow.com/q/63369264/)
