delegation: Implement glob delegation #124135
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Some changes occurred in src/tools/rustfmt cc @rust-lang/rustfmt |
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I guess it makes the most sense if I review this one, too. r? fmease |
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delegation: Implement list delegation
```rust
reuse prefix::{a, b, c};
```
Using design described in rust-lang/rfcs#3530 (comment) (the lists are desugared at macro expansion time).
List delegations are expanded eagerly when encountered, similarly to `#[cfg]`s, and not enqueued for later resolution/expansion like regular macros or glob delegation (rust-lang#124135).
Part of rust-lang#118212.
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@rustbot ready |
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Support delegating to all trait methods in one go.
Overriding globs with explicit definitions is also supported.
The implementation is generally based on the design from rust-lang/rfcs#3530 (comment), but unlike with list delegation in #123413 we cannot expand glob delegation eagerly.
We have to enqueue it into the queue of unexpanded macros (most other macros are processed this way too), and then a glob delegation waits in that queue until its trait path is resolved, and enough code expands to generate the identifier list produced from the glob.
Glob delegation is only allowed in impls, and can only point to traits.
Supporting it in other places gives very little practical benefit, but significantly raises the implementation complexity.
Part of #118212.