Possible parse error / possible unused_parens false positive (explicit return UFCS)

[withoutboats]

This does not compile, because the open < is parsed as a comparison operator. Possibly, this is a bug, and it should be parsed as it is intended - opening a type scope. But I don't know.

pub fn stringify<T: ToString>(arg: T) -> String {
    return <T as ToString>::to_string(&arg);
}

If the current parse is correct, adding parens should not produce an unused_parens error, because these parens are necessary to make it parse as intended. However, it does:

pub fn stringify<T: ToString>(arg: T) -> String {
    return (<T as ToString>::to_string(&arg));
}

[petrochenkov]

@withoutboats

This does not compile

It does on nightly!
Fixed by #37290