ICE: non-lifetime passed to :lifetime

[durka]

This code crashes the compiler. However, the location of the error is pointed out, which is nice.

#![feature(macro_lifetime_matcher)]

macro_rules! m { ($x:lifetime) => { } }

m!(a);

error: internal compiler error: not a lifetime
 --> src/main.rs:5:8
  |
5 |     m!(a);
  |        ^

thread 'main' panicked at 'Box<Any>', librustc_errors/lib.rs:491:9
note: Run with `RUST_BACKTRACE=1` for a backtrace.
error: aborting due to previous error

cc #50380 @ricochet1k

[kennytm]

cc #34303.

[estebank]

The error occurs during parsing a lifetime unconditionally, which is used during macro parsing:

rust/src/libsyntax/ext/tt/macro_parser.rs

Line 838 in d40a0b3

"lifetime" => token::NtLifetime(p.expect_lifetime().ident),

I would modify the code above to preemptively use check_lifetime(), and if false, emit an appropriate diagnostic error.

---

Also, if this is your first contribution to rustc, https://forge.rust-lang.org/ contains quite a bit of information on how to set up your environment. If you need extra help, feel free to reach out to anyone in the team, here or in gitter.

[rleungx]

I'm interested in taking this issue.