Anon lifetime in `impl Trait` no longer suggests adding a lifetime parameter

[estebank]

Given fn foo(_: impl Iterator<Item = &u32>) {}.

In 1.63:

error[E0106]: missing lifetime specifier
 --> src/lib.rs:1:32
  |
1 | fn foo(_: impl Iterator<Item = &u32>) {}
  |                                ^ expected named lifetime parameter
  |
help: consider introducing a named lifetime parameter
  |
1 | fn foo<'a>(_: impl Iterator<Item = &'a u32>) {}
  |       ++++                          ++

In 1.64:

error[E0658]: anonymous lifetimes in `impl Trait` are unstable
 --> src/lib.rs:1:32
  |
1 | fn foo(_: impl Iterator<Item = &u32>) {}
  |                                ^

[apiraino]

WG-prioritization assigning priority (Zulip discussion).

@rustbot label -I-prioritize +P-high

[pnkfelix]

self-assigning to ensure we record a cargo-bisect to the injecting PR

[apiraino]

I went ahead and attempted a bisection. The breadcrumbs seem to lead to rollup of #99231 with possibly #97720 being the patchset where this issue originates cc @cjgillot ?

searched nightlies: from nightly-2022-07-13 to nightly-2022-07-15
regressed nightly: nightly-2022-07-15
searched commit range: 87588a2...c2f428d
regressed commit: f1a8854

bisected with cargo-bisect-rustc v0.6.3

Host triple: x86_64-unknown-linux-gnu
Reproduce with:

cargo bisect-rustc --start 2022-07-13 --end 2022-07-15 --preserve 

[spastorino]

I'm not sure what would be wrong after @cjgillot change. I think this is exactly the support Camille has added. If you use #![feature(anonymous_lifetime_in_impl_trait)] the example compiles and if you don't the error points to the anonymous lifetime and tells you that you would need the feature flag to support such case.