Don't suggest wrapping attr in unsafe if it may come from proc macro

compiler/rustc_attr_parsing/src/safety.rs

@@ -62,16 +62,28 @@ impl<'sess, S: Stage> AttributeParser<'sess, S> {
                     Some(unsafe_since) => path_span.edition() >= unsafe_since,
                 };
 
+                let mut not_from_proc_macro = true;
+                if diag_span.from_expansion()
+                    && let Ok(mut snippet) = self.sess.source_map().span_to_snippet(diag_span)
+                {
+                    snippet.retain(|c| !c.is_whitespace());
+                    if snippet.contains("!(") || snippet.starts_with("#[") && snippet.ends_with("]")
+                    {
+                        not_from_proc_macro = false;
+                    }
+                }
+
                 if emit_error {
                     self.stage.emit_err(
                         self.sess,
                         crate::session_diagnostics::UnsafeAttrOutsideUnsafe {
                             span: path_span,
-                            suggestion:
+                            suggestion: not_from_proc_macro.then(|| {
                                 crate::session_diagnostics::UnsafeAttrOutsideUnsafeSuggestion {
                                     left: diag_span.shrink_to_lo(),
                                     right: diag_span.shrink_to_hi(),
-                                },
+                                }
+                            }),
                         },
                     );
                 } else {
@@ -81,7 +93,8 @@ impl<'sess, S: Stage> AttributeParser<'sess, S> {
                         span: path_span,
                         kind: AttributeLintKind::UnsafeAttrOutsideUnsafe {
                             attribute_name_span: path_span,
-                            sugg_spans: (diag_span.shrink_to_lo(), diag_span.shrink_to_hi()),
+                            sugg_spans: not_from_proc_macro
+                                .then(|| (diag_span.shrink_to_lo(), diag_span.shrink_to_hi())),
                         },
                     })
                 }

compiler/rustc_attr_parsing/src/session_diagnostics.rs

@@ -758,7 +758,7 @@ pub(crate) struct UnsafeAttrOutsideUnsafe {
     #[label]
     pub span: Span,
     #[subdiagnostic]
-    pub suggestion: UnsafeAttrOutsideUnsafeSuggestion,
+    pub suggestion: Option<UnsafeAttrOutsideUnsafeSuggestion>,
 }
 
 #[derive(Subdiagnostic)]

compiler/rustc_lint/src/early/diagnostics.rs

@@ -353,14 +353,14 @@ pub fn decorate_attribute_lint(
             }
             .decorate_lint(diag)
         }
-        &AttributeLintKind::UnsafeAttrOutsideUnsafe {
-            attribute_name_span,
-            sugg_spans: (left, right),
-        } => lints::UnsafeAttrOutsideUnsafeLint {
-            span: attribute_name_span,
-            suggestion: lints::UnsafeAttrOutsideUnsafeSuggestion { left, right },
+        &AttributeLintKind::UnsafeAttrOutsideUnsafe { attribute_name_span, sugg_spans } => {
+            lints::UnsafeAttrOutsideUnsafeLint {
+                span: attribute_name_span,
+                suggestion: sugg_spans
+                    .map(|(left, right)| lints::UnsafeAttrOutsideUnsafeSuggestion { left, right }),
+            }
+            .decorate_lint(diag)
         }
-        .decorate_lint(diag),
         &AttributeLintKind::UnexpectedCfgName(name, value) => {
             check_cfg::unexpected_cfg_name(sess, tcx, name, value).decorate_lint(diag)
         }

compiler/rustc_lint/src/lints.rs

@@ -3177,7 +3177,7 @@ pub(crate) struct UnsafeAttrOutsideUnsafeLint {
     #[label]
     pub span: Span,
     #[subdiagnostic]
-    pub suggestion: UnsafeAttrOutsideUnsafeSuggestion,
+    pub suggestion: Option<UnsafeAttrOutsideUnsafeSuggestion>,
 }
 
 #[derive(Subdiagnostic)]

compiler/rustc_lint_defs/src/lib.rs

@@ -729,7 +729,7 @@ pub enum AttributeLintKind {
     },
     UnsafeAttrOutsideUnsafe {
         attribute_name_span: Span,
-        sugg_spans: (Span, Span),
+        sugg_spans: Option<(Span, Span)>,
     },
     UnexpectedCfgName((Symbol, Span), Option<(Symbol, Span)>),
     UnexpectedCfgValue((Symbol, Span), Option<(Symbol, Span)>),

tests/ui/rust-2024/unsafe-attributes/auxiliary/unsafe-attributes-pm-in-2024.rs

@@ -0,0 +1,29 @@
+//@ edition: 2024
+
+extern crate proc_macro;
+
+use proc_macro::TokenStream;
+
+#[proc_macro]
+pub fn missing_unsafe(_input: TokenStream) -> TokenStream {
+    "#[no_mangle] pub fn abc() {}".parse().unwrap()
+}
+
+#[proc_macro_attribute]
+pub fn attr_missing_unsafe(_attr: TokenStream, _input: TokenStream) -> TokenStream {
+    "#[no_mangle] pub fn bar() {}".parse().unwrap()
+}
+
+#[proc_macro_derive(AttrMissingUnsafe)]
+pub fn derive_attr_missing_unsafe(_input: TokenStream) -> TokenStream {
+    "#[no_mangle] pub fn baz() {}".parse().unwrap()
+}
+
+#[proc_macro]
+pub fn macro_rules_missing_unsafe(_input: TokenStream) -> TokenStream {
+    "macro_rules! make_fn {
+        () => { #[no_mangle] pub fn foo() { } };
+    }"
+    .parse()
+    .unwrap()
+}

tests/ui/rust-2024/unsafe-attributes/unsafe-attributes-from-pm-in-2024.rs

@@ -0,0 +1,18 @@
+// Test for unsafe attributes generated by a proc-macro.
+
+//@ proc-macro: unsafe-attributes-pm-in-2024.rs
+//@ ignore-backends: gcc
+
+unsafe_attributes_pm_in_2024::missing_unsafe!(); //~ ERROR unsafe attribute used without unsafe
+
+#[unsafe_attributes_pm_in_2024::attr_missing_unsafe] //~ ERROR unsafe attribute used without unsafe
+pub fn bar() {}
+
+#[derive(unsafe_attributes_pm_in_2024::AttrMissingUnsafe)] //~ ERROR unsafe attribute used without unsafe
+struct Baz;
+
+unsafe_attributes_pm_in_2024::macro_rules_missing_unsafe!(); //~ ERROR unsafe attribute used without unsafe
+
+make_fn!();
+
+fn main() {}

tests/ui/rust-2024/unsafe-attributes/unsafe-attributes-from-pm-in-2024.stderr

@@ -0,0 +1,37 @@
+error: unsafe attribute used without unsafe
+  --> $DIR/unsafe-attributes-from-pm-in-2024.rs:6:1
+   |
+LL | unsafe_attributes_pm_in_2024::missing_unsafe!();
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ usage of unsafe attribute
+   |
+   = note: this error originates in the macro `unsafe_attributes_pm_in_2024::missing_unsafe` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: unsafe attribute used without unsafe
+  --> $DIR/unsafe-attributes-from-pm-in-2024.rs:8:1
+   |
+LL | #[unsafe_attributes_pm_in_2024::attr_missing_unsafe]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ usage of unsafe attribute
+   |
+   = note: this error originates in the attribute macro `unsafe_attributes_pm_in_2024::attr_missing_unsafe` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: unsafe attribute used without unsafe
+  --> $DIR/unsafe-attributes-from-pm-in-2024.rs:11:10
+   |
+LL | #[derive(unsafe_attributes_pm_in_2024::AttrMissingUnsafe)]
+   |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ usage of unsafe attribute
+   |
+   = note: this error originates in the derive macro `unsafe_attributes_pm_in_2024::AttrMissingUnsafe` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: unsafe attribute used without unsafe
+  --> $DIR/unsafe-attributes-from-pm-in-2024.rs:14:1
+   |
+LL | unsafe_attributes_pm_in_2024::macro_rules_missing_unsafe!();
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ usage of unsafe attribute
+LL |
+LL | make_fn!();
+   | ---------- in this macro invocation
+   |
+   = note: this error originates in the macro `make_fn` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 4 previous errors
+