make type modifiers usable for macro substitution

[rust-highfive]

Issue by metajack
Friday Apr 05, 2013 at 21:04 GMT

For earlier discussion, see rust-lang/rust#5748

This issue was labelled with: A-syntaxext, B-RFC in the Rust repository

---

Currently you can not pass @ or ~ or @mut to a macro by itself, but this would be useful in a few cases. I tried doing this to add Clone trait implementations without copying the code:

macro_rules! ptr_clone_impl(
    ($p:something) => {
        impl<T:Clone> Clone for $p T {
            #[inline(always)]
            fn clone(&self) -> $p T { $p (**self).clone() }
        }
    }
)

ptr_clone_impl!(~)
ptr_clone_impl!(@)
ptr_clone_impl!(@mut)

But as far as I can tell there is no fragment specifier that will work for those tokens.

[alexcrichton]

We don't really have sigils now, so I think this is no longer relevant