Stabilize unsafe extern blocks (RFC 3484)

Author: spastorino

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -452,11 +452,6 @@ impl<'a> AstValidator<'a> {
                             item_span: span,
                             block: Some(self.current_extern_span().shrink_to_lo()),
                         });
-                    } else if !self.features.unsafe_extern_blocks {
-                        self.dcx().emit_err(errors::InvalidSafetyOnExtern {
-                            item_span: span,
-                            block: None,
-                        });
                     }
                 }
             }
@@ -1053,32 +1048,19 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                         errors::VisibilityNotPermittedNote::IndividualForeignItems,
                     );
 
-                    if this.features.unsafe_extern_blocks {
-                        if &Safety::Default == safety {
-                            if item.span.at_least_rust_2024() {
-                                this.dcx()
-                                    .emit_err(errors::MissingUnsafeOnExtern { span: item.span });
-                            } else {
-                                this.lint_buffer.buffer_lint(
-                                    MISSING_UNSAFE_ON_EXTERN,
-                                    item.id,
-                                    item.span,
-                                    BuiltinLintDiag::MissingUnsafeOnExtern {
-                                        suggestion: item.span.shrink_to_lo(),
-                                    },
-                                );
-                            }
+                    if &Safety::Default == safety {
+                        if item.span.at_least_rust_2024() {
+                            this.dcx().emit_err(errors::MissingUnsafeOnExtern { span: item.span });
+                        } else {
+                            this.lint_buffer.buffer_lint(
+                                MISSING_UNSAFE_ON_EXTERN,
+                                item.id,
+                                item.span,
+                                BuiltinLintDiag::MissingUnsafeOnExtern {
+                                    suggestion: item.span.shrink_to_lo(),
+                                },
+                            );
                         }
-                    } else if let &Safety::Unsafe(span) = safety {
-                        let mut diag = this
-                            .dcx()
-                            .create_err(errors::UnsafeItem { span, kind: "extern block" });
-                        rustc_session::parse::add_feature_diagnostics(
-                            &mut diag,
-                            self.session,
-                            sym::unsafe_extern_blocks,
-                        );
-                        diag.emit();
                     }
 
                     if abi.is_none() {

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -561,10 +561,6 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session, features: &Features) {
     gate_all!(precise_capturing, "precise captures on `impl Trait` are experimental");
     gate_all!(global_registration, "global registration is experimental");
     gate_all!(unsafe_attributes, "`#[unsafe()]` markers for attributes are experimental");
-    gate_all!(
-        unsafe_extern_blocks,
-        "`unsafe extern {}` blocks and `safe` keyword are experimental"
-    );
     gate_all!(return_type_notation, "return type notation is experimental");
 
     if !visitor.features.never_patterns {

compiler/rustc_feature/src/accepted.rs

@@ -387,6 +387,8 @@ declare_features! (
     (accepted, unrestricted_attribute_tokens, "1.34.0", Some(55208)),
     /// The `unsafe_op_in_unsafe_fn` lint (allowed by default): no longer treat an unsafe function as an unsafe block.
     (accepted, unsafe_block_in_unsafe_fn, "1.52.0", Some(71668)),
+    /// Allows unsafe on extern declarations and safety qualifiers over internal items.
+    (accepted, unsafe_extern_blocks, "CURRENT_RUSTC_VERSION", Some(123743)),
     /// Allows importing and reexporting macros with `use`,
     /// enables macro modularization in general.
     (accepted, use_extern_macros, "1.30.0", Some(35896)),

compiler/rustc_feature/src/unstable.rs

@@ -628,8 +628,6 @@ declare_features! (
     (incomplete, unnamed_fields, "1.74.0", Some(49804)),
     /// Allows unsafe attributes.
     (unstable, unsafe_attributes, "1.80.0", Some(123757)),
-    /// Allows unsafe on extern declarations and safety qualifiers over internal items.
-    (unstable, unsafe_extern_blocks, "1.80.0", Some(123743)),
     /// Allows const generic parameters to be defined with types that
     /// are not `Sized`, e.g. `fn foo<const N: [u8]>() {`.
     (incomplete, unsized_const_params, "CURRENT_RUSTC_VERSION", Some(95174)),

compiler/rustc_lint_defs/src/builtin.rs

@@ -4865,7 +4865,6 @@ declare_lint! {
     /// ### Example
     ///
     /// ```rust
-    /// #![feature(unsafe_extern_blocks)]
     /// #![warn(missing_unsafe_on_extern)]
     /// #![allow(dead_code)]
     ///

compiler/rustc_parse/src/parser/mod.rs

@@ -1205,9 +1205,6 @@ impl<'a> Parser<'a> {
         if self.eat_keyword_case(kw::Unsafe, case) {
             Safety::Unsafe(self.prev_token.uninterpolated_span())
         } else if self.eat_keyword_case(kw::Safe, case) {
-            self.psess
-                .gated_spans
-                .gate(sym::unsafe_extern_blocks, self.prev_token.uninterpolated_span());
             Safety::Safe(self.prev_token.uninterpolated_span())
         } else {
             Safety::Default

tests/rustdoc/unsafe-extern-blocks.rs

@@ -1,6 +1,5 @@
 // Test to ensure the feature is working as expected.
 
-#![feature(unsafe_extern_blocks)]
 #![crate_name = "foo"]
 
 // @has 'foo/index.html'
@@ -13,7 +12,7 @@
 // @count - '//ul[@class="item-table"]//sup[@title="unsafe function"]' 1
 // @has - '//ul[@class="item-table"]//sup[@title="unsafe function"]' '⚠'
 
-unsafe extern {
+unsafe extern "C" {
     // @has 'foo/static.FOO.html'
     // @has - '//pre[@class="rust item-decl"]' 'pub static FOO: i32'
     pub safe static FOO: i32;

tests/ui/feature-gates/feature-gate-unsafe-extern-blocks.rs

@@ -1,4 +1,3 @@
-#![feature(unsafe_extern_blocks)]
 #![deny(unsafe_code)]
 
 #[allow(unsafe_code)]