https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101095
Bug ID: 101095 Summary: Bogus "error: conflicting global module declaration" for abbreviate function template using placeholder type in noexcept Product: gcc Version: 11.1.1 Status: UNCONFIRMED Keywords: rejects-valid Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: redi at gcc dot gnu.org Target Milestone: --- cat > mod.h <<EOT #ifndef MOD_H #define MOD_H template<typename T> concept rhubarb = true; template<typename T> constexpr bool nothrow = true; void donkey(rhubarb auto i) noexcept(nothrow<decltype(i)>) { } #endif EOT cat > mod.H <<EOT #include "mod.h" EOT cat > mod.C <<EOT #include "mod.h" import "mod.H"; int main() { donkey(1); } EOT g++ -std=c++20 -fmodule-header mod.H -c g++ -std=c++20 -fmodules-ts mod.C This gives a bogus error: In file included from mod.H:1, of module ./mod.H, imported at mod.C:2: mod.h: In function ‘int main()’: mod.h:5:6: error: conflicting global module declaration ‘template<class auto:1> void donkey(auto:1)’ 5 | void donkey(rhubarb auto i) noexcept(nothrow<decltype(i)>) { } | ^~~~~~ In file included from mod.C:1: mod.h:5:6: note: existing declaration ‘template<class auto:1> requires rhubarb<auto:1> void donkey(auto:1)’ 5 | void donkey(rhubarb auto i) noexcept(nothrow<decltype(i)>) { } | ^~~~~~ mod.C:6:3: note: during load of binding ‘::donkey’ 6 | donkey(1); | ^~~~~~ The code compiles OK if the noexcept-specifier doesn't refer to the auto:1 type.