Rollup merge of #139718 - folkertdev:unsafe-attributes-earlier-editions, r=fmease

enforce unsafe attributes in pre-2024 editions by default

New unsafe attributes should emit an error when used without the `unsafe(...)` in all editions.

The `no_mangle`, `link_section` and `export_name` attributes are exceptions, and can still be used without an unsafe in earlier editions. The only attributes for which this change is relevant right now are `#[ffi_const]` and `#[ffi_pure]`.

This change is required for making `#[unsafe(naked)]` sound in pre-2024 editions.

1 files changed, 8 insertions, 2 deletions

diff --git a/compiler/rustc_parse/src/validate_attr.rs b/compiler/rustc_parse/src/validate_attr.rs
index 6bbd650dcdf..6a1c2af48ed 100644
--- a/compiler/rustc_parse/src/validate_attr.rs
+++ b/compiler/rustc_parse/src/validate_attr.rs
@@ -157,7 +157,7 @@ fn is_attr_template_compatible(template: &AttributeTemplate, meta: &ast::MetaIte
 pub fn check_attribute_safety(psess: &ParseSess, safety: AttributeSafety, attr: &Attribute) {
     let attr_item = attr.get_normal_item();
 
-    if safety == AttributeSafety::Unsafe {
+    if let AttributeSafety::Unsafe { unsafe_since } = safety {
         if let ast::Safety::Default = attr_item.unsafety {
             let path_span = attr_item.path.span;
 
@@ -167,7 +167,13 @@ pub fn check_attribute_safety(psess: &ParseSess, safety: AttributeSafety, attr:
             // square bracket respectively.
             let diag_span = attr_item.span();
 
-            if attr.span.at_least_rust_2024() {
+            // Attributes can be safe in earlier editions, and become unsafe in later ones.
+            let emit_error = match unsafe_since {
+                None => true,
+                Some(unsafe_since) => attr.span.edition() >= unsafe_since,
+            };
+
+            if emit_error {
                 psess.dcx().emit_err(errors::UnsafeAttrOutsideUnsafe {
                     span: path_span,
                     suggestion: errors::UnsafeAttrOutsideUnsafeSuggestion {