https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70141
Sori Lee <s.lee at dpmms dot cam.ac.uk> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |s.lee at dpmms dot cam.ac.uk --- Comment #21 from Sori Lee <s.lee at dpmms dot cam.ac.uk> --- Gcc 9.2.0 refuses to compile the following partial specialisation. template <class U> struct a { using type = int; }; template <class T> struct b; template <class U> struct b<typename a<U>::type> {}; The error it gives reads: test.cpp:10:8: error: template parameters not deducible in partial specialization: 10 | struct b<typename a<U>::type> {}; | ^~~~~~~~~~~~~~~~~~~~~~ test.cpp:10:8: note: āUā This looks similar to the problem previously discussed on this list, whence I report it here.