undeclared raw lifetime; "consider introducing non-raw lifetime" #143150
Description
Code
fn a(_: dyn Trait + 'r#fn) { } trait Trait {}Current output
error[E0261]: use of undeclared lifetime name `'fn` --> src/lib.rs:1:21 | 1 | fn a(_: dyn Trait + 'r#fn) { | ^^^^^ undeclared lifetime | help: consider introducing lifetime `'fn` here | 1 | fn a<'fn>(_: dyn Trait + 'r#fn) { | +++++Desired output
error[E0261]: use of undeclared lifetime name `'r#fn` --> src/lib.rs:1:21 | 1 | fn a(_: dyn Trait + 'r#fn) { | ^^^^^ undeclared lifetime | help: consider introducing lifetime `'r#fn` here | 1 | fn a<'r#fn>(_: dyn Trait + 'r#fn) { | +++++++Rationale and extra context
'fn, as the diagnostic currently suggests, is not a valid lifetime.
it is my understanding that for non-reserved lifetimes, something like 'r#a is supposed to be equivalent to 'a, and that the diagnostic would be correct, were it not for the fact that in this case the r# is mandatory or else it's a syntax error.
Rust Version
rustc 1.90.0-nightly (bdaba05a9 2025-06-27) binary: rustc commit-hash: bdaba05a953eb5abeba0011cdda2560d157aed2e commit-date: 2025-06-27 host: x86_64-unknown-linux-gnu release: 1.90.0-nightly LLVM version: 20.1.7