https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96878
Bug ID: 96878
Summary: Failed class template argument deduction in
unevaluated, parenthesized context
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: sbergman at redhat dot com
Target Milestone: ---
At least with recent GCC 11 trunk and with gcc-c++-10.2.1-1.fc32.x86_64:
> $ cat test.cc
> template<int N> struct S { S(char const (& s)[N]); };
> auto n = sizeof (S(""));
> $ g++ -std=c++17 -fsyntax-only test.cc
> test.cc:2:18: error: missing template arguments after ‘S<...auto...>’
> 2 | auto n = sizeof (S(""));
> | ^
> test.cc:1:24: note: ‘template<int N> struct S’ declared here
> 1 | template<int N> struct S { S(char const (& s)[N]); };
> | ^
If you change `sizeof (S(""))` to `sizeof S("")`, compilation succeeds.
