Nightly 2021-03-24 claims that the feature `unsafe_block_in_unsafe_fn` was stabilized in 1.51, but stable 1.51 claims that the lint `unsafe_op_in_unsafe_fn` is still unstable

[PatchMixolydic]

I tried this code on nightly Rust:

#![feature(unsafe_block_in_unsafe_fn)]
#![deny(unsafe_op_in_unsafe_fn)]

fn main() {}

This produced a warning claiming that unsafe_block_in_unsafe_fn was stabilized in 1.51:

patchmixolydic@blue-pearl /tmp/rust-issue → cargo +nightly run
   Compiling rust-issue v0.1.0 (/tmp/rust-issue)
warning: the feature `unsafe_block_in_unsafe_fn` has been stable since 1.51.0 and no longer requires an attribute to enable
 --> src/main.rs:1:12
  |
1 | #![feature(unsafe_block_in_unsafe_fn)]
  |            ^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: `#[warn(stable_features)]` on by default

warning: 1 warning emitted

I removed the feature gate and tried compiling the code on Rust 1.51.0:

#![deny(unsafe_op_in_unsafe_fn)]

fn main() {}

However, this led to an error claiming that unsafe_op_in_unsafe_fn is unstable:

patchmixolydic@blue-pearl /tmp/rust-issue → cargo run
   Compiling rust-issue v0.1.0 (/tmp/rust-issue)
error[E0658]: the `unsafe_op_in_unsafe_fn` lint is unstable
 --> src/main.rs:1:1
  |
1 | #![deny(unsafe_op_in_unsafe_fn)]
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: see issue #71668 <https://github.com/rust-lang/rust/issues/71668> for more information

error: aborting due to previous error

Meta

rustc --version --verbose:

rustc 1.51.0 (2fd73fabe 2021-03-23)
binary: rustc
commit-hash: 2fd73fabe469357a12c2c974c140f67e7cdd76d0
commit-date: 2021-03-23
host: x86_64-unknown-linux-gnu
release: 1.51.0
LLVM version: 11.0.1

rustc +nightly --version --verbose:

rustc 1.53.0-nightly (07e0e2ec2 2021-03-24)
binary: rustc
commit-hash: 07e0e2ec268c140e607e1ac7f49f145612d0f597
commit-date: 2021-03-24
host: x86_64-unknown-linux-gnu
release: 1.53.0-nightly
LLVM version: 12.0.0

@rustbot modify labels: +A-diagnostics +D-incorrect +F-unsafe-block-in-unsafe-fn

[PatchMixolydic]

According to the milestone on the stabilization PR (#79208), this feature will be stabilized in 1.52, but the PR wasn't updated to account for this.

[JohnTitor]

Thanks for the report, yeah, the stabilized version should be wrong. Submitted #83736 as a fix.