...opCast can't be used for implicit conversions to bool.

I guess you're thinking...

...t think opCast gets called for implicit conversions; it only gets called for explicit casts...

...replacement character (U+FFFD) in implicit widening conversions?

For example:

----
char c = "ö"[0];
wchar...

...that D supports any kind of implicit conversions for user-defined types. So, if you...

...of bounds checking, but for char -> dchar conversions, or any other invalid mechanism?

Yep, it...

...specific algorithm actually needs. Removing the implicit conversions between `char`, `wchar`, and `dchar` would also...

...to wchar.

Once you disable the naive conversions, then the autodecoding in foreach isn't...

But conversions to scope const(char)[] could be made safe, right? (If scope were ever...

...of an error about implicit conversions.

https://dlang.org/spec/type.html#usual-arithmetic-conversions

...for explicit type conversions. However, you seem to want implicit type conversions.

> I Still need...