[Bug c++/126878] New: [contracts] parameter pack of reference type used in a contract assertion is rejected

waffl3x at protonmail dot com via Gcc-bugs <[email protected]> Fri, 14 Aug 2026 21:35:46 +0000

Newsgroups	gmane.comp.gcc.bugs
Message-ID	<[email protected]/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126878

            Bug ID: 126878
           Summary: [contracts] parameter pack of reference type used in a
                    contract assertion is rejected
           Product: gcc
           Version: 17.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: waffl3x at protonmail dot com
  Target Milestone: ---

https://godbolt.org/z/8W857531h
```
template<typename... Args>
void f(Args&... args)
  pre((... && args)) {}

template void f<int>(int&);
```
Emits "'const' qualifiers cannot be applied to 'Args&'"

This occurs in all 3 contract assertion types, with pack expansion,
fold expression and pack index. I suspect there are more bugs around
here. I will try to add exhaustive test cases covering most the trivial
cases once I've fixed this one.