https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81486
Bug ID: 81486 Summary: Class template argument deduction fails with (), succeeds with {} Product: gcc Version: 7.1.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: barry.revzin at gmail dot com Target Milestone: --- Consider this example, simplified from https://stackoverflow.com/q/45195890/2069064: template <class T> struct C { C(T ); }; template <> struct C<void> { }; C() -> C<void>; int main() { auto a = C{}; // ok auto b = C(); // error } The two forms are equivalent in this context - a and b should both deduce to C<void>. Yet, gcc accepts a and errors on b with: cannot deduce template arguments for 'C' from ()