[morio]

What kind of false positives are you seeing with gcc?

Personally I have never seen gcc spitting out a false positive. IMO it's always a good idea to explicitly downcast even if you know that it's 'safe'. That way someone else will see instantly what's going on. The fact that Rust requires it should tell us something.

[xeeeeeeeeeeenu]

For example, I've just reported this: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101537

You can find more cases in the bugtracker. To be fair, it seems many of them were fixed in recent releases.

[Cloudef]

The 1 and 0 are ints. It most likely complaints because the sign isn't same.