Bug 16581 – Template shape misdetected in is() expression

Consider: struct Test(T) {} template PropagateQualifier(Q) { static if (is(Q == immutable(Test!X), X)) alias PropagateQualifier = immutable X; else static if (is(Q == const Test!X, X)) alias PropagateQualifier = const X; else static if (is(Q == Test!X, X)) alias PropagateQualifier = X; else static assert(0); } static assert(is(PropagateQualifier!(Test!char) == char)); This fails because PropagateQualifier!(Test!char) yields immutable(cha r). Shuffling the three cases around reveals that the first is() test always passes. Inglorious workaround: struct Test(T) {} template PropagateQualifier(Q) { static if (is(Q == immutable)) { static if (is(Q == immutable(Test!X), X)) alias PropagateQualifier = immutable X; } else static if (is(Q == const)) { static if (is(Q == const(Test!X), X)) alias PropagateQualifier = const X; } else static if (is(Q == Test!X, X)) alias PropagateQualifier = X; else static assert(0); } static assert(is(PropagateQualifier!(Test!char) == char)); static assert(is(PropagateQualifier!(const(Test!char)) == const char)); static assert(is(PropagateQualifier!(Test!(immutable char)) == immutable char));

THIS ISSUE HAS BEEN MOVED TO GITHUB https://github.com/dlang/dmd/issues/17777 DO NOT COMMENT HERE ANYMORE, NOBODY WILL SEE IT, THIS ISSUE HAS BEEN MOVED TO GITHUB