Find index of function in vtbl[0..dim] that this function overrides. Prefer an exact match to a covariant one.
vtable to use
maximal vtable dimension
enable fix https://issues.dlang.org/show_bug.cgi?id=17349
-1 didn't find one -2 can't determine because of forward references
See Implementation
Find index of function in vtbl[0..dim] that this function overrides. Prefer an exact match to a covariant one.