Bug 17353 – is expression type specialization matching strips const

const(T[]) matches an is-expression which it shouldn't match: --- alias const(int[]) T; static if (is(T U == U[])) static assert(is(T == U[])); // fails --- The "static if" and "static assert" conditions should be equivalent so the "static assert" should never fail. Instead the "static if" behaves as if the is-expression would contain Unqual!T instead of T.

The static if and the static assert are indeed not equivalent since type-system wise const(int[]) is a constant array of mutable ints. The pattern-matching is expression set u to the element type of const(int[]) which is const(int). If you then create the slice type of U you get const(int)[] which is different from const (int[]). So there is no discrepancy. I agree it can be annoying though.