Avoid notes that only make sense for unsafe functions

Author: oli-obk

compiler/rustc_mir_build/src/check_unsafety.rs

@@ -747,7 +747,10 @@ impl UnsafeOpKind {
     ) {
         let parent_id = tcx.hir().get_parent_item(hir_id);
         let parent_owner = tcx.hir_owner_node(parent_id);
-        let should_suggest = parent_owner.fn_sig().is_some_and(|sig| sig.header.is_unsafe());
+        let should_suggest = parent_owner.fn_sig().is_some_and(|sig| {
+            // Do not suggest for safe target_feature functions
+            matches!(sig.header.safety, hir::HeaderSafety::Normal(hir::Safety::Unsafe))
+        });
         let unsafe_not_inherited_note = if should_suggest {
             suggest_unsafe_block.then(|| {
                 let body_span = tcx.hir().body(parent_owner.body_id().unwrap()).value.span;
@@ -910,7 +913,7 @@ impl UnsafeOpKind {
             {
                 true
             } else if let Some(sig) = tcx.hir().fn_sig_by_hir_id(*id)
-                && sig.header.is_unsafe()
+                && matches!(sig.header.safety, hir::HeaderSafety::Normal(hir::Safety::Unsafe))
             {
                 true
             } else {

compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs

@@ -461,9 +461,11 @@ impl<T> Trait<T> for X {
                     (ty::FnPtr(_, hdr), ty::FnDef(def_id, _))
                     | (ty::FnDef(def_id, _), ty::FnPtr(_, hdr)) => {
                         if tcx.fn_sig(def_id).skip_binder().safety() < hdr.safety {
-                            diag.note(
+                            if !tcx.codegen_fn_attrs(def_id).safe_target_features {
+                                diag.note(
                                 "unsafe functions cannot be coerced into safe function pointers",
-                            );
+                                );
+                            }
                         }
                     }
                     (ty::Adt(_, _), ty::Adt(def, args))

tests/ui/rfcs/rfc-2396-target_feature-11/fn-ptr.stderr

@@ -12,7 +12,6 @@ LL |     let foo: fn() = foo;
    = note: expected fn pointer `fn()`
                  found fn item `#[target_features] fn() {foo}`
    = note: functions with `#[target_feature]` can only be coerced to `unsafe` function pointers
-   = note: unsafe functions cannot be coerced into safe function pointers
 
 error: aborting due to 1 previous error
 

tests/ui/rfcs/rfc-2396-target_feature-11/safe-calls.stderr

@@ -26,9 +26,6 @@ LL |     Quux.avx_bmi2();
 error[E0133]: call to function `avx_bmi2` with `#[target_feature]` is unsafe and requires unsafe function or block
   --> $DIR/safe-calls.rs:38:5
    |
-LL | fn bar() {
-   | -------- items do not inherit unsafety from separate enclosing items
-LL |     sse2();
 LL |     avx_bmi2();
    |     ^^^^^^^^^^ call to function with `#[target_feature]`
    |
@@ -37,9 +34,6 @@ LL |     avx_bmi2();
 error[E0133]: call to function `Quux::avx_bmi2` with `#[target_feature]` is unsafe and requires unsafe function or block
   --> $DIR/safe-calls.rs:40:5
    |
-LL | fn bar() {
-   | -------- items do not inherit unsafety from separate enclosing items
-...
 LL |     Quux.avx_bmi2();
    |     ^^^^^^^^^^^^^^^ call to function with `#[target_feature]`
    |
@@ -48,9 +42,6 @@ LL |     Quux.avx_bmi2();
 error[E0133]: call to function `avx_bmi2` with `#[target_feature]` is unsafe and requires unsafe function or block
   --> $DIR/safe-calls.rs:47:5
    |
-LL | fn baz() {
-   | -------- items do not inherit unsafety from separate enclosing items
-LL |     sse2();
 LL |     avx_bmi2();
    |     ^^^^^^^^^^ call to function with `#[target_feature]`
    |
@@ -59,9 +50,6 @@ LL |     avx_bmi2();
 error[E0133]: call to function `Quux::avx_bmi2` with `#[target_feature]` is unsafe and requires unsafe function or block
   --> $DIR/safe-calls.rs:49:5
    |
-LL | fn baz() {
-   | -------- items do not inherit unsafety from separate enclosing items
-...
 LL |     Quux.avx_bmi2();
    |     ^^^^^^^^^^^^^^^ call to function with `#[target_feature]`
    |