On Wednesday, 1 September 2021 at 12:32:36 UTC, Steven Schveighoffer wrote: > To further explain for readers, the issue is: > > ```d > void foo(T)(Vector!(const(T)) arg); > ``` This compiles: ```d struct Vector(T){} void f(T:const(U),U)(Vector!T arg); void f1() { Vector!(const int) a; f(a); } ```