Bug 8968 – std.traits.ParameterIdentifierTuple is undocumented and doesn't work with ref params

import std.traits; void foo(ref int x) { } void main() { alias ParameterIdentifierTuple!foo x; } D:\DMD\dmd2\windows\bin\..\..\src\phobos\std\traits.d(518): Error: function literal __lambda16 (ref int x) is not callable using argument types (int) It tries to use a clever trick by defining an inner lambda with a parameter list, and then extracts the name from that. But it can't call a lambda with a ref parameter at compile-time. Honestly we should just have a simple __trait that returns the parameter identifiers, because this is a very hacky workaround that doesn't work in all cases.

its documented now https://github.com/D-Programming-Language/phobos/pull/946

and evidently does work with ref int now: https://github.com/D-Programming-Language/phobos/commit/49cbab43c2bdf5d14d51d869c62e010befa3bcab