Parse unsafe attributes

Author: dtolnay

src/attr.rs

@@ -653,6 +653,7 @@ pub(crate) mod parsing {
     use crate::parse::{Parse, ParseStream};
     use crate::path::Path;
     use crate::{mac, token};
+    use proc_macro2::Ident;
     use std::fmt::{self, Display};
 
     pub(crate) fn parse_inner(input: ParseStream, attrs: &mut Vec<Attribute>) -> Result<()> {
@@ -685,27 +686,38 @@ pub(crate) mod parsing {
     #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
     impl Parse for Meta {
         fn parse(input: ParseStream) -> Result<Self> {
-            let path = input.call(Path::parse_mod_style)?;
+            let path = parse_outermost_meta_path(input)?;
             parse_meta_after_path(path, input)
         }
     }
 
     #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
     impl Parse for MetaList {
         fn parse(input: ParseStream) -> Result<Self> {
-            let path = input.call(Path::parse_mod_style)?;
+            let path = parse_outermost_meta_path(input)?;
             parse_meta_list_after_path(path, input)
         }
     }
 
     #[cfg_attr(docsrs, doc(cfg(feature = "parsing")))]
     impl Parse for MetaNameValue {
         fn parse(input: ParseStream) -> Result<Self> {
-            let path = input.call(Path::parse_mod_style)?;
+            let path = parse_outermost_meta_path(input)?;
             parse_meta_name_value_after_path(path, input)
         }
     }
 
+    // Unlike meta::parse_meta_path which accepts arbitrary keywords in the path,
+    // only the `unsafe` keyword is accepted as an attribute's outermost path.
+    fn parse_outermost_meta_path(input: ParseStream) -> Result<Path> {
+        if input.peek(Token![unsafe]) {
+            let unsafe_token: Token![unsafe] = input.parse()?;
+            Ok(Path::from(Ident::new("unsafe", unsafe_token.span)))
+        } else {
+            Path::parse_mod_style(input)
+        }
+    }
+
     pub(crate) fn parse_meta_after_path(path: Path, input: ParseStream) -> Result<Meta> {
         if input.peek(token::Paren) || input.peek(token::Bracket) || input.peek(token::Brace) {
             parse_meta_list_after_path(path, input).map(Meta::List)

tests/repo/mod.rs

@@ -25,13 +25,6 @@ static EXCLUDE_FILES: &[&str] = &[
     "tests/rustdoc/unsafe-extern-blocks.rs",
     "tests/ui/rust-2024/unsafe-extern-blocks/safe-items.rs",
 
-    // TODO: unsafe attributes: `#[unsafe(path::to)]`
-    // https://github.com/dtolnay/syn/issues/1710
-    "src/tools/rust-analyzer/crates/parser/test_data/parser/inline/ok/0213_metas.rs",
-    "src/tools/rustfmt/tests/target/unsafe_attributes.rs",
-    "tests/ui/attributes/unsafe/unsafe-attributes.rs",
-    "tests/ui/rust-2024/unsafe-attributes/unsafe-attribute-marked.rs",
-
     // TODO: non-lifetime binders: `where for<'a, T> &'a Struct<T>: Trait`
     // https://github.com/dtolnay/syn/issues/1435
     "src/tools/rustfmt/tests/source/issue_5721.rs",