[REG2.065a] Issue 11822 - `-de` switch causees ICE with `auto` return and other stuff

https://d.puremagic.com/issues/show_bug.cgi?id=11822

This is caused by #2850.

`TypeFunction` is also used for the extra payload of function attributes. Therefore, even if function signature or its body has errors, we would be better to leave that `fd->type->ty == Tfunction`.