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Let qpath contain NtTy: `<$:ty as $:ty>::…` by dtolnay · Pull Request #911...

 2 years ago
source link: https://github.com/rust-lang/rust/pull/91150
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dtolnay commented on Nov 23, 2021

Example:

macro_rules! m {
    (<$type:ty as $trait:ty>::$name:ident) => {
        <$type as $trait>::$name
    };
}

fn main() {
    let _: m!(<str as ToOwned>::Owned);
}

Previous behavior:

error: expected identifier, found `ToOwned`
 --> src/main.rs:3:19
  |
3 |         <$type as $trait>::$name
  |                   ^^^^^^ expected identifier
...
8 |     let _: m!(<str as ToOwned>::Owned);
  |            ---------------------------
  |            |
  |            this macro call doesn't expand to a type
  |            in this macro invocation

The expected identifier, found `ToOwned` error is particularly silly. I think it should be fine to accept this code as long as $trait is of the form TyKind::Path(None, path); if it is any other kind of NtTy, we'll keep the same behavior as before.


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