From: bors <bors@rust-lang.org>
Date: Sat, 17 Mar 2018 23:22:57 +0000 (+0000)
Subject: Auto merge of #48842 - petrochenkov:under, r=nikomatsakis
X-Git-Url: https://git.lizzy.rs/?a=commitdiff_plain;h=ca6a98426192f838cc90a18709f92d425b86029e;p=rust.git

Auto merge of #48842 - petrochenkov:under, r=nikomatsakis

syntax: Make `_` a reserved identifier

Why:
- Lexically `_` is an identifier.
- Internally it makes implementation of `use Trait as _;` (https://github.com/rust-lang/rust/issues/48216) and some other things cleaner.
- We prevent the externally observable effect of `_` being accepted by macros expecting `ident` by treating `_` specially in the `ident` matcher:
```rust
macro_rules! m {
    ($i: ident) => { let $i = 10; }
}

m!(_); // Still an error
```
---

ca6a98426192f838cc90a18709f92d425b86029e