Comment by cipherjim

With ! the implicit conversion happens at compile time, never at runtime.

It cannot by definition happen at runtime because the never type has no values and thus cannot be constructed under any circumstances.

Any compile time coercions that occur would convert types (or generics args of types) to !

I find it difficult to imagine any situation where that would result in a working program - only if the coerced types or references to coerced generics were not even used would it compile.