https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108736
Bug ID: 108736 Summary: pconcepts] multidimensional subscript operator reports invalid error in requires test Product: gcc Version: 13.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: ldalessandro at gmail dot com Target Milestone: --- The following code produces an error when evaluating the concept. auto foo(auto a, auto... i) -> decltype(auto) { if constexpr (requires { a[i...]; }) { return a[i...]; } else { return a; } } int x = foo(1); > <source>: In instantiation of 'decltype(auto) foo(auto:1, auto:2 ...) [with > auto:1 = int; auto:2 = {}]': > <source>:10:12: required from here > <source>:2:31: error: built-in subscript operator without expression list > 2 | if constexpr (requires { a[i...]; }) { > | ~^ > Compiler returned: 1 Workaround: specialize on sizeof...(i) to avoid this test when i... is empty. Live example: https://godbolt.org/z/K3oezd1qz