internal compiler error: unexpected lifetime bound

I'm seeing an internal compiler error on the following input (found by fuzz-rustc):

$ echo "enum e{A((?'a a+?+l))}" > main.rs
$ rustc main.rs
error: `?` may only modify trait bounds, not lifetime bounds
 --> main.rs:1:11
  |
1 | enum e{A((?'a a+?+l))}
  |           ^

error: expected one of `)`, `+`, or `,`, found `a`
 --> main.rs:1:15
  |
1 | enum e{A((?'a a+?+l))}
  |               ^ expected one of `)`, `+`, or `,`

error: internal compiler error: unexpected lifetime bound
 --> main.rs:1:11
  |
1 | enum e{A((?'a a+?+l))}
  |           ^^^

thread 'rustc' panicked at 'Box<Any>', <::std::macros::panic macros>:2:4
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

note: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#bug-reports

note: rustc 1.43.0-nightly (58b834344 2020-02-05) running on x86_64-unknown-linux-gnu

error: aborting due to 3 previous errors

The error happens on nightly and beta but not on stable.

triage : P-medium, removing nomination, adding needs-bisect.

(the bisection here would be entirely automatable if rust-lang/cargo-bisect-rustc#34 were addressed.)

Bisected roughly: ICE occurred from #67505 but not panicked, panicked from #68034

@Centril

#67148 in particular looks suspicious.
cc @Centril

Pre-#67148, we return early with an error here:

rust/src/librustc_parse/parser/ty.rs

Line 82 in c64eecf

ts.push(self.parse_ty()?);

Post-#67148, in the corresponding code happens in a call to parse_paren_comma_sep:

rust/src/librustc_parse/parser/ty.rs

Lines 197 to 201 in 1ad6b5e

    
           let (ts, trailing) = self.parse_paren_comma_seq(|p| { 
        
               let ty = p.parse_ty()?; 
        
               trailing_plus = p.prev_token_kind == PrevTokenKind::Plus; 
        
               Ok(ty) 
        
           })?;

and the parser "recovers" from the error encountered in p.parse_ty()?, allowing this line to be reached:

rust/src/librustc_parse/parser/ty.rs

Line 217 in 1ad6b5e

self.span_bug(ty.span, "unexpected lifetime bound")

.

I opened #69014, which takes the stance that span_bug() is no longer appropriate here.

It's possible that there's a better fix that changes the way parse_paren_comma_seq() works, but that would require a deeper expertise of how these things are supposed to work than I currently have.

Rollup merge of rust-lang#69014 - dwrensha:fix-68890, r=Centril

Navigation Menu

Repository navigation

internal compiler error: unexpected lifetime bound #68890

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

	let (ts, trailing) = self.parse_paren_comma_seq(\|p\| {
	let ty = p.parse_ty()?;
	trailing_plus = p.prev_token_kind == PrevTokenKind::Plus;
	Ok(ty)
	})?;

internal compiler error: unexpected lifetime bound #68890

Description

Activity

pnkfelix commented on Feb 6, 2020

pnkfelix commented on Feb 6, 2020

JohnTitor commented on Feb 6, 2020

dwrensha commented on Feb 8, 2020

dwrensha commented on Feb 9, 2020

dwrensha commented on Feb 10, 2020

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions