https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92777
Bug ID: 92777 Summary: ICE on concept containing lambda with auto variable declaration Product: gcc Version: 10.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: jason.e.cobb at gmail dot com Target Milestone: --- With GCC trunk in std=c++2a mode and the following code: [begin code] template<typename> concept auto_in_lambda = requires() { [](){ auto x = 4; }(); }; static_assert(auto_in_lambda<int>); [end code] GCC ICEs with the following message: <source>: In lambda function: <source>:4:14: internal compiler error: in tsubst_decl, at cp/pt.c:14375 4 | auto x = 4; | ^ GCC does not ICE if the concept is never instantiated, nor does it ICE if the "auto" variable is changed to have a defined type. On Compiler Explorer: https://godbolt.org/z/myujUX