The safe keyword appears to be allowed in all function contexts. However, the RFC explicitly says it should only be allowed in extern blocks:

The safe keyword is contextual and is currently allowed only within extern blocks.

#![feature(unsafe_extern_blocks)]

safe fn foo() {}

I expected to see this happen: Compile error

Instead, this happened: Compile success

cc @spastorino FYI

macro fragment

Additionally, it looks like safe fn foo(); is accepted in $item macro fragment specifier. I think there are different decisions to make here:

• Should $item allow safe functions at all? (I think "yes", since it already accepts extern-block items.)
• Should that be split out into a separate fragment, such as $item_2021 does not allow safe, and $item does in 2024? See Tracking Issue for updating expr macro fragment specifier for Rust 2024 #123742.

EDIT: Concluded below this should not be an issue.

Meta

rustc 1.81.0-nightly (59e2c01c2 2024-06-17)
binary: rustc
commit-hash: 59e2c01c2217a01546222e4d9ff4e6695ee8a1db
commit-date: 2024-06-17
host: aarch64-apple-darwin
release: 1.81.0-nightly
LLVM version: 18.1.7

Tracking:

• Tracking Issue for RFC 3484: Unsafe Extern Blocks #123743