1 files changed, 26 insertions, 14 deletions
diff --git a/compiler/rustc_expand/src/base.rs b/compiler/rustc_expand/src/base.rs
index 3956125bace..810a5a21a05 100644
--- a/compiler/rustc_expand/src/base.rs
+++ b/compiler/rustc_expand/src/base.rs
@@ -10,7 +10,7 @@ use rustc_ast::attr::{AttributeExt, MarkedAttrs};
 use rustc_ast::token::MetaVarKind;
 use rustc_ast::tokenstream::TokenStream;
 use rustc_ast::visit::{AssocCtxt, Visitor};
-use rustc_ast::{self as ast, AttrVec, Attribute, HasAttrs, Item, NodeId, PatKind};
+use rustc_ast::{self as ast, AttrVec, Attribute, HasAttrs, Item, NodeId, PatKind, Safety};
 use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
 use rustc_data_structures::sync;
 use rustc_errors::{BufferedEarlyLint, DiagCtxtHandle, ErrorGuaranteed, PResult};
@@ -324,16 +324,16 @@ pub trait BangProcMacro {
 
 impl<F> BangProcMacro for F
 where
-    F: Fn(TokenStream) -> TokenStream,
+    F: Fn(&mut ExtCtxt<'_>, Span, TokenStream) -> Result<TokenStream, ErrorGuaranteed>,
 {
     fn expand<'cx>(
         &self,
-        _ecx: &'cx mut ExtCtxt<'_>,
-        _span: Span,
+        ecx: &'cx mut ExtCtxt<'_>,
+        span: Span,
         ts: TokenStream,
     ) -> Result<TokenStream, ErrorGuaranteed> {
         // FIXME setup implicit context in TLS before calling self.
-        Ok(self(ts))
+        self(ecx, span, ts)
     }
 }
 
@@ -345,6 +345,21 @@ pub trait AttrProcMacro {
         annotation: TokenStream,
         annotated: TokenStream,
     ) -> Result<TokenStream, ErrorGuaranteed>;
+
+    // Default implementation for safe attributes; override if the attribute can be unsafe.
+    fn expand_with_safety<'cx>(
+        &self,
+        ecx: &'cx mut ExtCtxt<'_>,
+        safety: Safety,
+        span: Span,
+        annotation: TokenStream,
+        annotated: TokenStream,
+    ) -> Result<TokenStream, ErrorGuaranteed> {
+        if let Safety::Unsafe(span) = safety {
+            ecx.dcx().span_err(span, "unnecessary `unsafe` on safe attribute");
+        }
+        self.expand(ecx, span, annotation, annotated)
+    }
 }
 
 impl<F> AttrProcMacro for F
@@ -999,17 +1014,14 @@ impl SyntaxExtension {
 
     /// A dummy bang macro `foo!()`.
     pub fn dummy_bang(edition: Edition) -> SyntaxExtension {
-        fn expander<'cx>(
-            cx: &'cx mut ExtCtxt<'_>,
+        fn expand(
+            ecx: &mut ExtCtxt<'_>,
             span: Span,
-            _: TokenStream,
-        ) -> MacroExpanderResult<'cx> {
-            ExpandResult::Ready(DummyResult::any(
-                span,
-                cx.dcx().span_delayed_bug(span, "expanded a dummy bang macro"),
-            ))
+            _ts: TokenStream,
+        ) -> Result<TokenStream, ErrorGuaranteed> {
+            Err(ecx.dcx().span_delayed_bug(span, "expanded a dummy bang macro"))
         }
-        SyntaxExtension::default(SyntaxExtensionKind::LegacyBang(Arc::new(expander)), edition)
+        SyntaxExtension::default(SyntaxExtensionKind::Bang(Arc::new(expand)), edition)
     }
 
     /// A dummy derive macro `#[derive(Foo)]`.