Bug 9324 – Can't assign a type with a Tuple subtype to a Tuple

import std.string; import std.typecons; struct MyTuple(T...) { this(T args) { tup = Tuple!T(args); } void opAssign(Tuple!T args) { this.tup = args; } Tuple!T tup; alias tup this; } void main() { MyTuple!(string, int) x; x = tuple("foo", 1); // ok Tuple!(string, int) y; y = x; // fail } test.d(28): Error: template std.typecons.Tuple!(string, int).Tuple.opAssign does not match any function template declaration. isTuple check fails on MyTuple even though it has a Tuple subtype. But why? isTuple implementation: template isTuple(T) { static if (is(Unqual!T Unused : Tuple!Specs, Specs...)) { enum isTuple = true; } else { enum isTuple = false; } } It seems to me like we need some way of determining if type 'A' has subtype 'B'. I don't think we have a trait or Phobos function to do it, perhaps we should introduce something like this?

Works with latest DMD.