Bug 6910 – __traits(hasMember, "<name>") does not work, if template has alias param

Given this code fragment: -------------- struct Bag(S...) {     alias S Types; } template Test(alias i, B) {     void fn() {         foreach(t; B.Types)         {             switch(i) {                 case IndexOf!(t, B.Types):                 {                     pragma(msg, __traits(allMembers, t));                     pragma(msg, __traits(hasMember, t, "m"));                     break;                 }                 default: {}             }         }     } } struct A {     int m; } void main() {     int i;     alias Test!(i, Bag!(A)).fn func; } ---------------------- DMD will output: ---------------------- tuple("m") false --------------------- It seems that __traits(hasMember, ..) evaluates to false, despite the fact that the type does have a member "m". However if the template Test does not have an alias parameter, everything will work just fine.

I think this is an issue that both of D1 and D2 have. D2 patch: https://github.com/D-Programming-Language/dmd/pull/509

https://github.com/D-Programming-Language/dmd/commit/6fb5861528c7568d2546774a1c884f99594024c0 https://github.com/D-Programming-Language/dmd/commit/129c1ae7fe50cb3cb9a218e232f42f9a5a987e29