[Issue 20389] __traits(isDisabled) with invalid template function

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=20389

--- Comment #1 from John Hall <john.michael.hall at gmail.com> ---
It seems that this is related to not having a module defined...

When I add something like
module A;
to the top and then 
static assert(__traits(isDisabled, A.foo));
compiles without error when U is there and if U is removed then it gives the
error that T is not defined.

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