Add suggestion to THIR unsafe_op_in_unsafe_fn lint

compiler/rustc_hir/src/hir.rs

@@ -3566,6 +3566,15 @@ impl<'hir> OwnerNode<'hir> {
         }
     }
 
+    pub fn fn_sig(self) -> Option<&'hir FnSig<'hir>> {
+        match self {
+            OwnerNode::TraitItem(TraitItem { kind: TraitItemKind::Fn(fn_sig, _), .. })
+            | OwnerNode::ImplItem(ImplItem { kind: ImplItemKind::Fn(fn_sig, _), .. })
+            | OwnerNode::Item(Item { kind: ItemKind::Fn(fn_sig, _, _), .. }) => Some(fn_sig),
+            _ => None,
+        }
+    }
+
     pub fn fn_decl(self) -> Option<&'hir FnDecl<'hir>> {
         match self {
             OwnerNode::TraitItem(TraitItem { kind: TraitItemKind::Fn(fn_sig, _), .. })

compiler/rustc_mir_build/messages.ftl

@@ -320,6 +320,7 @@ mir_build_unreachable_pattern = unreachable pattern
     .label = unreachable pattern
     .catchall_label = matches any value
 
+mir_build_unsafe_fn_safe_body = an unsafe function restricts its caller, but its body is safe by default
 mir_build_unsafe_not_inherited = items do not inherit unsafety from separate enclosing items
 
 mir_build_unsafe_op_in_unsafe_fn_borrow_of_layout_constrained_field_requires_unsafe =
@@ -386,3 +387,5 @@ mir_build_unused_unsafe = unnecessary `unsafe` block
 mir_build_unused_unsafe_enclosing_block_label = because it's nested under this `unsafe` block
 
 mir_build_variant_defined_here = not covered
+
+mir_build_wrap_suggestion = consider wrapping the function body in an unsafe block

compiler/rustc_mir_build/src/check_unsafety.rs

@@ -35,6 +35,10 @@ struct UnsafetyVisitor<'a, 'tcx> {
     param_env: ParamEnv<'tcx>,
     inside_adt: bool,
     warnings: &'a mut Vec<UnusedUnsafeWarning>,
+
+    /// Flag to ensure that we only suggest wrapping the entire function body in
+    /// an unsafe block once.
+    suggest_unsafe_block: bool,
 }
 
 impl<'tcx> UnsafetyVisitor<'_, 'tcx> {
@@ -95,7 +99,13 @@ impl<'tcx> UnsafetyVisitor<'_, 'tcx> {
             SafetyContext::UnsafeFn if unsafe_op_in_unsafe_fn_allowed => {}
             SafetyContext::UnsafeFn => {
                 // unsafe_op_in_unsafe_fn is disallowed
-                kind.emit_unsafe_op_in_unsafe_fn_lint(self.tcx, self.hir_context, span);
+                kind.emit_unsafe_op_in_unsafe_fn_lint(
+                    self.tcx,
+                    self.hir_context,
+                    span,
+                    self.suggest_unsafe_block,
+                );
+                self.suggest_unsafe_block = false;
             }
             SafetyContext::Safe => {
                 kind.emit_requires_unsafe_err(
@@ -297,6 +307,7 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> {
             }
             PatKind::InlineConstant { def, .. } => {
                 self.visit_inner_body(*def);
+                visit::walk_pat(self, pat);
             }
             _ => {
                 visit::walk_pat(self, pat);
@@ -545,7 +556,22 @@ impl UnsafeOpKind {
         tcx: TyCtxt<'_>,
         hir_id: hir::HirId,
         span: Span,
+        suggest_unsafe_block: bool,
     ) {
+        let parent_id = tcx.hir().get_parent_item(hir_id);
+        let parent_owner = tcx.hir().owner(parent_id);
+        let should_suggest = parent_owner.fn_sig().map_or(false, |sig| sig.header.is_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;
+                UnsafeNotInheritedLintNote {
+                    signature_span: tcx.def_span(parent_id.def_id),
+                    body_span,
+                }
+            })
+        } else {
+            None
+        };
         // FIXME: ideally we would want to trim the def paths, but this is not
         // feasible with the current lint emission API (see issue #106126).
         match self {
@@ -556,61 +582,89 @@ impl UnsafeOpKind {
                 UnsafeOpInUnsafeFnCallToUnsafeFunctionRequiresUnsafe {
                     span,
                     function: &with_no_trimmed_paths!(tcx.def_path_str(*did)),
+                    unsafe_not_inherited_note,
                 },
             ),
             CallToUnsafeFunction(None) => tcx.emit_spanned_lint(
                 UNSAFE_OP_IN_UNSAFE_FN,
                 hir_id,
                 span,
-                UnsafeOpInUnsafeFnCallToUnsafeFunctionRequiresUnsafeNameless { span },
+                UnsafeOpInUnsafeFnCallToUnsafeFunctionRequiresUnsafeNameless {
+                    span,
+                    unsafe_not_inherited_note,
+                },
             ),
             UseOfInlineAssembly => tcx.emit_spanned_lint(
                 UNSAFE_OP_IN_UNSAFE_FN,
                 hir_id,
                 span,
-                UnsafeOpInUnsafeFnUseOfInlineAssemblyRequiresUnsafe { span },
+                UnsafeOpInUnsafeFnUseOfInlineAssemblyRequiresUnsafe {
+                    span,
+                    unsafe_not_inherited_note,
+                },
             ),
             InitializingTypeWith => tcx.emit_spanned_lint(
                 UNSAFE_OP_IN_UNSAFE_FN,
                 hir_id,
                 span,
-                UnsafeOpInUnsafeFnInitializingTypeWithRequiresUnsafe { span },
+                UnsafeOpInUnsafeFnInitializingTypeWithRequiresUnsafe {
+                    span,
+                    unsafe_not_inherited_note,
+                },
             ),
             UseOfMutableStatic => tcx.emit_spanned_lint(
                 UNSAFE_OP_IN_UNSAFE_FN,
                 hir_id,
                 span,
-                UnsafeOpInUnsafeFnUseOfMutableStaticRequiresUnsafe { span },
+                UnsafeOpInUnsafeFnUseOfMutableStaticRequiresUnsafe {
+                    span,
+                    unsafe_not_inherited_note,
+                },
             ),
             UseOfExternStatic => tcx.emit_spanned_lint(
                 UNSAFE_OP_IN_UNSAFE_FN,
                 hir_id,
                 span,
-                UnsafeOpInUnsafeFnUseOfExternStaticRequiresUnsafe { span },
+                UnsafeOpInUnsafeFnUseOfExternStaticRequiresUnsafe {
+                    span,
+                    unsafe_not_inherited_note,
+                },
             ),
             DerefOfRawPointer => tcx.emit_spanned_lint(
                 UNSAFE_OP_IN_UNSAFE_FN,
                 hir_id,
                 span,
-                UnsafeOpInUnsafeFnDerefOfRawPointerRequiresUnsafe { span },
+                UnsafeOpInUnsafeFnDerefOfRawPointerRequiresUnsafe {
+                    span,
+                    unsafe_not_inherited_note,
+                },
             ),
             AccessToUnionField => tcx.emit_spanned_lint(
                 UNSAFE_OP_IN_UNSAFE_FN,
                 hir_id,
                 span,
-                UnsafeOpInUnsafeFnAccessToUnionFieldRequiresUnsafe { span },
+                UnsafeOpInUnsafeFnAccessToUnionFieldRequiresUnsafe {
+                    span,
+                    unsafe_not_inherited_note,
+                },
             ),
             MutationOfLayoutConstrainedField => tcx.emit_spanned_lint(
                 UNSAFE_OP_IN_UNSAFE_FN,
                 hir_id,
                 span,
-                UnsafeOpInUnsafeFnMutationOfLayoutConstrainedFieldRequiresUnsafe { span },
+                UnsafeOpInUnsafeFnMutationOfLayoutConstrainedFieldRequiresUnsafe {
+                    span,
+                    unsafe_not_inherited_note,
+                },
             ),
             BorrowOfLayoutConstrainedField => tcx.emit_spanned_lint(
                 UNSAFE_OP_IN_UNSAFE_FN,
                 hir_id,
                 span,
-                UnsafeOpInUnsafeFnBorrowOfLayoutConstrainedFieldRequiresUnsafe { span },
+                UnsafeOpInUnsafeFnBorrowOfLayoutConstrainedFieldRequiresUnsafe {
+                    span,
+                    unsafe_not_inherited_note,
+                },
             ),
             CallToFunctionWith(did) => tcx.emit_spanned_lint(
                 UNSAFE_OP_IN_UNSAFE_FN,
@@ -619,6 +673,7 @@ impl UnsafeOpKind {
                 UnsafeOpInUnsafeFnCallToFunctionWithRequiresUnsafe {
                     span,
                     function: &with_no_trimmed_paths!(tcx.def_path_str(*did)),
+                    unsafe_not_inherited_note,
                 },
             ),
         }
@@ -833,6 +888,7 @@ pub fn thir_check_unsafety(tcx: TyCtxt<'_>, def: LocalDefId) {
         param_env: tcx.param_env(def),
         inside_adt: false,
         warnings: &mut warnings,
+        suggest_unsafe_block: true,
     };
     visitor.visit_expr(&thir[expr]);
 

compiler/rustc_mir_build/src/errors.rs

@@ -29,6 +29,8 @@ pub struct UnsafeOpInUnsafeFnCallToUnsafeFunctionRequiresUnsafe<'a> {
     #[label]
     pub span: Span,
     pub function: &'a str,
+    #[subdiagnostic]
+    pub unsafe_not_inherited_note: Option<UnsafeNotInheritedLintNote>,
 }
 
 #[derive(LintDiagnostic)]
@@ -37,6 +39,8 @@ pub struct UnsafeOpInUnsafeFnCallToUnsafeFunctionRequiresUnsafe<'a> {
 pub struct UnsafeOpInUnsafeFnCallToUnsafeFunctionRequiresUnsafeNameless {
     #[label]
     pub span: Span,
+    #[subdiagnostic]
+    pub unsafe_not_inherited_note: Option<UnsafeNotInheritedLintNote>,
 }
 
 #[derive(LintDiagnostic)]
@@ -45,6 +49,8 @@ pub struct UnsafeOpInUnsafeFnCallToUnsafeFunctionRequiresUnsafeNameless {
 pub struct UnsafeOpInUnsafeFnUseOfInlineAssemblyRequiresUnsafe {
     #[label]
     pub span: Span,
+    #[subdiagnostic]
+    pub unsafe_not_inherited_note: Option<UnsafeNotInheritedLintNote>,
 }
 
 #[derive(LintDiagnostic)]
@@ -53,6 +59,8 @@ pub struct UnsafeOpInUnsafeFnUseOfInlineAssemblyRequiresUnsafe {
 pub struct UnsafeOpInUnsafeFnInitializingTypeWithRequiresUnsafe {
     #[label]
     pub span: Span,
+    #[subdiagnostic]
+    pub unsafe_not_inherited_note: Option<UnsafeNotInheritedLintNote>,
 }
 
 #[derive(LintDiagnostic)]
@@ -61,6 +69,8 @@ pub struct UnsafeOpInUnsafeFnInitializingTypeWithRequiresUnsafe {
 pub struct UnsafeOpInUnsafeFnUseOfMutableStaticRequiresUnsafe {
     #[label]
     pub span: Span,
+    #[subdiagnostic]
+    pub unsafe_not_inherited_note: Option<UnsafeNotInheritedLintNote>,
 }
 
 #[derive(LintDiagnostic)]
@@ -69,6 +79,8 @@ pub struct UnsafeOpInUnsafeFnUseOfMutableStaticRequiresUnsafe {
 pub struct UnsafeOpInUnsafeFnUseOfExternStaticRequiresUnsafe {
     #[label]
     pub span: Span,
+    #[subdiagnostic]
+    pub unsafe_not_inherited_note: Option<UnsafeNotInheritedLintNote>,
 }
 
 #[derive(LintDiagnostic)]
@@ -77,6 +89,8 @@ pub struct UnsafeOpInUnsafeFnUseOfExternStaticRequiresUnsafe {
 pub struct UnsafeOpInUnsafeFnDerefOfRawPointerRequiresUnsafe {
     #[label]
     pub span: Span,
+    #[subdiagnostic]
+    pub unsafe_not_inherited_note: Option<UnsafeNotInheritedLintNote>,
 }
 
 #[derive(LintDiagnostic)]
@@ -85,6 +99,8 @@ pub struct UnsafeOpInUnsafeFnDerefOfRawPointerRequiresUnsafe {
 pub struct UnsafeOpInUnsafeFnAccessToUnionFieldRequiresUnsafe {
     #[label]
     pub span: Span,
+    #[subdiagnostic]
+    pub unsafe_not_inherited_note: Option<UnsafeNotInheritedLintNote>,
 }
 
 #[derive(LintDiagnostic)]
@@ -93,13 +109,17 @@ pub struct UnsafeOpInUnsafeFnAccessToUnionFieldRequiresUnsafe {
 pub struct UnsafeOpInUnsafeFnMutationOfLayoutConstrainedFieldRequiresUnsafe {
     #[label]
     pub span: Span,
+    #[subdiagnostic]
+    pub unsafe_not_inherited_note: Option<UnsafeNotInheritedLintNote>,
 }
 
 #[derive(LintDiagnostic)]
 #[diag(mir_build_unsafe_op_in_unsafe_fn_borrow_of_layout_constrained_field_requires_unsafe)]
 pub struct UnsafeOpInUnsafeFnBorrowOfLayoutConstrainedFieldRequiresUnsafe {
     #[label]
     pub span: Span,
+    #[subdiagnostic]
+    pub unsafe_not_inherited_note: Option<UnsafeNotInheritedLintNote>,
 }
 
 #[derive(LintDiagnostic)]
@@ -109,6 +129,8 @@ pub struct UnsafeOpInUnsafeFnCallToFunctionWithRequiresUnsafe<'a> {
     #[label]
     pub span: Span,
     pub function: &'a str,
+    #[subdiagnostic]
+    pub unsafe_not_inherited_note: Option<UnsafeNotInheritedLintNote>,
 }
 
 #[derive(Diagnostic)]
@@ -376,6 +398,27 @@ pub struct UnsafeNotInheritedNote {
     pub span: Span,
 }
 
+pub struct UnsafeNotInheritedLintNote {
+    pub signature_span: Span,
+    pub body_span: Span,
+}
+
+impl AddToDiagnostic for UnsafeNotInheritedLintNote {
+    fn add_to_diagnostic_with<F>(self, diag: &mut Diagnostic, _: F)
+    where
+        F: Fn(&mut Diagnostic, SubdiagnosticMessage) -> SubdiagnosticMessage,
+    {
+        diag.span_note(self.signature_span, fluent::mir_build_unsafe_fn_safe_body);
+        let body_start = self.body_span.shrink_to_lo();
+        let body_end = self.body_span.shrink_to_hi();
+        diag.tool_only_multipart_suggestion(
+            fluent::mir_build_wrap_suggestion,
+            vec![(body_start, "{ unsafe ".into()), (body_end, "}".into())],
+            Applicability::MaybeIncorrect,
+        );
+    }
+}
+
 #[derive(LintDiagnostic)]
 #[diag(mir_build_unused_unsafe)]
 pub struct UnusedUnsafe {

tests/ui/unsafe/edition-2024-unsafe_op_in_unsafe_fn.stderr → tests/ui/unsafe/edition-2024-unsafe_op_in_unsafe_fn.mir.stderr

@@ -1,12 +1,12 @@
 warning: call to unsafe function is unsafe and requires unsafe block (error E0133)
-  --> $DIR/edition-2024-unsafe_op_in_unsafe_fn.rs:12:5
+  --> $DIR/edition-2024-unsafe_op_in_unsafe_fn.rs:13:5
    |
 LL |     unsf();
    |     ^^^^^^ call to unsafe function
    |
    = note: consult the function's documentation for information on how to avoid undefined behavior
 note: an unsafe function restricts its caller, but its body is safe by default
-  --> $DIR/edition-2024-unsafe_op_in_unsafe_fn.rs:11:1
+  --> $DIR/edition-2024-unsafe_op_in_unsafe_fn.rs:12:1
    |
 LL | unsafe fn foo() {
    | ^^^^^^^^^^^^^^^

tests/ui/unsafe/edition-2024-unsafe_op_in_unsafe_fn.rs

@@ -1,17 +1,21 @@
 // edition: 2024
 // compile-flags: -Zunstable-options
 // check-pass
+// revisions: mir thir
+// [thir]compile-flags: -Zthir-unsafeck
 
 #![crate_type = "lib"]
-
 #![deny(unused_unsafe)]
 
 unsafe fn unsf() {}
 
 unsafe fn foo() {
     unsf();
-    //~^ WARN call to unsafe function is unsafe and requires unsafe block
+    //[mir]~^ WARN call to unsafe function is unsafe and requires unsafe block
+    //[thir]~^^ WARN call to unsafe function `unsf` is unsafe and requires unsafe block
 
     // no unused_unsafe
-    unsafe { unsf(); }
+    unsafe {
+        unsf();
+    }
 }

tests/ui/unsafe/edition-2024-unsafe_op_in_unsafe_fn.thir.stderr

@@ -0,0 +1,16 @@
+warning: call to unsafe function `unsf` is unsafe and requires unsafe block (error E0133)
+  --> $DIR/edition-2024-unsafe_op_in_unsafe_fn.rs:13:5
+   |
+LL |     unsf();
+   |     ^^^^^^ call to unsafe function
+   |
+   = note: consult the function's documentation for information on how to avoid undefined behavior
+note: an unsafe function restricts its caller, but its body is safe by default
+  --> $DIR/edition-2024-unsafe_op_in_unsafe_fn.rs:12:1
+   |
+LL | unsafe fn foo() {
+   | ^^^^^^^^^^^^^^^
+   = note: `#[warn(unsafe_op_in_unsafe_fn)]` on by default
+
+warning: 1 warning emitted
+