Implement "items do not inherit unsafety" for THIR unsafeck

compiler/rustc_mir_build/messages.ftl

@@ -312,6 +312,8 @@ mir_build_unreachable_pattern = unreachable pattern
     .label = unreachable pattern
     .catchall_label = matches any value
 
+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 =
     borrow of layout constrained field with interior mutability is unsafe and requires unsafe block (error E0133)
     .note = references to fields of layout constrained fields lose the constraints. Coupled with interior mutability, the field can be changed to invalid values

compiler/rustc_mir_build/src/check_unsafety.rs

@@ -91,7 +91,12 @@ impl<'tcx> UnsafetyVisitor<'_, 'tcx> {
                 kind.emit_unsafe_op_in_unsafe_fn_lint(self.tcx, self.hir_context, span);
             }
             SafetyContext::Safe => {
-                kind.emit_requires_unsafe_err(self.tcx, span, unsafe_op_in_unsafe_fn_allowed);
+                kind.emit_requires_unsafe_err(
+                    self.tcx,
+                    span,
+                    self.hir_context,
+                    unsafe_op_in_unsafe_fn_allowed,
+                );
             }
         }
     }
@@ -602,98 +607,164 @@ impl UnsafeOpKind {
         &self,
         tcx: TyCtxt<'_>,
         span: Span,
+        hir_context: hir::HirId,
         unsafe_op_in_unsafe_fn_allowed: bool,
     ) {
+        let note_non_inherited = tcx.hir().parent_iter(hir_context).find(|(id, node)| {
+            if let hir::Node::Expr(block) = node
+                && let hir::ExprKind::Block(block, _) = block.kind
+                && let hir::BlockCheckMode::UnsafeBlock(_) = block.rules
+            {
+                true
+            }
+            else if let Some(sig) = tcx.hir().fn_sig_by_hir_id(*id)
+                && sig.header.is_unsafe()
+            {
+                true
+            } else {
+                false
+            }
+        });
+        let unsafe_not_inherited_note = if let Some((id, _)) = note_non_inherited {
+            let span = tcx.hir().span(id);
+            let span = tcx.sess.source_map().guess_head_span(span);
+            Some(UnsafeNotInheritedNote { span })
+        } else {
+            None
+        };
+
         match self {
             CallToUnsafeFunction(Some(did)) if unsafe_op_in_unsafe_fn_allowed => {
                 tcx.sess.emit_err(CallToUnsafeFunctionRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
                     span,
+                    unsafe_not_inherited_note,
                     function: &tcx.def_path_str(*did),
                 });
             }
             CallToUnsafeFunction(Some(did)) => {
                 tcx.sess.emit_err(CallToUnsafeFunctionRequiresUnsafe {
                     span,
+                    unsafe_not_inherited_note,
                     function: &tcx.def_path_str(*did),
                 });
             }
             CallToUnsafeFunction(None) if unsafe_op_in_unsafe_fn_allowed => {
                 tcx.sess.emit_err(
-                    CallToUnsafeFunctionRequiresUnsafeNamelessUnsafeOpInUnsafeFnAllowed { span },
+                    CallToUnsafeFunctionRequiresUnsafeNamelessUnsafeOpInUnsafeFnAllowed {
+                        span,
+                        unsafe_not_inherited_note,
+                    },
                 );
             }
             CallToUnsafeFunction(None) => {
-                tcx.sess.emit_err(CallToUnsafeFunctionRequiresUnsafeNameless { span });
+                tcx.sess.emit_err(CallToUnsafeFunctionRequiresUnsafeNameless {
+                    span,
+                    unsafe_not_inherited_note,
+                });
             }
             UseOfInlineAssembly if unsafe_op_in_unsafe_fn_allowed => {
-                tcx.sess
+                tcx.sess.emit_err(UseOfInlineAssemblyRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
-                    .emit_err(UseOfInlineAssemblyRequiresUnsafeUnsafeOpInUnsafeFnAllowed { span });
+                    span,
+                    unsafe_not_inherited_note,
+                });
             }
             UseOfInlineAssembly => {
-                tcx.sess.emit_err(UseOfInlineAssemblyRequiresUnsafe { span });
+                tcx.sess.emit_err(UseOfInlineAssemblyRequiresUnsafe {
+                    span,
+                    unsafe_not_inherited_note,
+                });
             }
             InitializingTypeWith if unsafe_op_in_unsafe_fn_allowed => {
-                tcx.sess
+                tcx.sess.emit_err(InitializingTypeWithRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
-                    .emit_err(InitializingTypeWithRequiresUnsafeUnsafeOpInUnsafeFnAllowed { span });
+                    span,
+                    unsafe_not_inherited_note,
+                });
             }
             InitializingTypeWith => {
-                tcx.sess.emit_err(InitializingTypeWithRequiresUnsafe { span });
+                tcx.sess.emit_err(InitializingTypeWithRequiresUnsafe {
+                    span,
+                    unsafe_not_inherited_note,
+                });
             }
             UseOfMutableStatic if unsafe_op_in_unsafe_fn_allowed => {
-                tcx.sess
+                tcx.sess.emit_err(UseOfMutableStaticRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
-                    .emit_err(UseOfMutableStaticRequiresUnsafeUnsafeOpInUnsafeFnAllowed { span });
+                    span,
+                    unsafe_not_inherited_note,
+                });
             }
             UseOfMutableStatic => {
-                tcx.sess.emit_err(UseOfMutableStaticRequiresUnsafe { span });
+                tcx.sess
+                    .emit_err(UseOfMutableStaticRequiresUnsafe { span, unsafe_not_inherited_note });
             }
             UseOfExternStatic if unsafe_op_in_unsafe_fn_allowed => {
-                tcx.sess
+                tcx.sess.emit_err(UseOfExternStaticRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
-                    .emit_err(UseOfExternStaticRequiresUnsafeUnsafeOpInUnsafeFnAllowed { span });
+                    span,
+                    unsafe_not_inherited_note,
+                });
             }
             UseOfExternStatic => {
-                tcx.sess.emit_err(UseOfExternStaticRequiresUnsafe { span });
+                tcx.sess
+                    .emit_err(UseOfExternStaticRequiresUnsafe { span, unsafe_not_inherited_note });
             }
             DerefOfRawPointer if unsafe_op_in_unsafe_fn_allowed => {
-                tcx.sess
+                tcx.sess.emit_err(DerefOfRawPointerRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
-                    .emit_err(DerefOfRawPointerRequiresUnsafeUnsafeOpInUnsafeFnAllowed { span });
+                    span,
+                    unsafe_not_inherited_note,
+                });
             }
             DerefOfRawPointer => {
-                tcx.sess.emit_err(DerefOfRawPointerRequiresUnsafe { span });
+                tcx.sess
+                    .emit_err(DerefOfRawPointerRequiresUnsafe { span, unsafe_not_inherited_note });
             }
             AccessToUnionField if unsafe_op_in_unsafe_fn_allowed => {
-                tcx.sess
+                tcx.sess.emit_err(AccessToUnionFieldRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
-                    .emit_err(AccessToUnionFieldRequiresUnsafeUnsafeOpInUnsafeFnAllowed { span });
+                    span,
+                    unsafe_not_inherited_note,
+                });
             }
             AccessToUnionField => {
-                tcx.sess.emit_err(AccessToUnionFieldRequiresUnsafe { span });
+                tcx.sess
+                    .emit_err(AccessToUnionFieldRequiresUnsafe { span, unsafe_not_inherited_note });
             }
             MutationOfLayoutConstrainedField if unsafe_op_in_unsafe_fn_allowed => {
                 tcx.sess.emit_err(
                     MutationOfLayoutConstrainedFieldRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
                         span,
+                        unsafe_not_inherited_note,
                     },
                 );
             }
             MutationOfLayoutConstrainedField => {
-                tcx.sess.emit_err(MutationOfLayoutConstrainedFieldRequiresUnsafe { span });
+                tcx.sess.emit_err(MutationOfLayoutConstrainedFieldRequiresUnsafe {
+                    span,
+                    unsafe_not_inherited_note,
+                });
             }
             BorrowOfLayoutConstrainedField if unsafe_op_in_unsafe_fn_allowed => {
                 tcx.sess.emit_err(
-                    BorrowOfLayoutConstrainedFieldRequiresUnsafeUnsafeOpInUnsafeFnAllowed { span },
+                    BorrowOfLayoutConstrainedFieldRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
+                        span,
+                        unsafe_not_inherited_note,
+                    },
                 );
             }
             BorrowOfLayoutConstrainedField => {
-                tcx.sess.emit_err(BorrowOfLayoutConstrainedFieldRequiresUnsafe { span });
+                tcx.sess.emit_err(BorrowOfLayoutConstrainedFieldRequiresUnsafe {
+                    span,
+                    unsafe_not_inherited_note,
+                });
             }
             CallToFunctionWith(did) if unsafe_op_in_unsafe_fn_allowed => {
                 tcx.sess.emit_err(CallToFunctionWithRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
                     span,
+                    unsafe_not_inherited_note,
                     function: &tcx.def_path_str(*did),
                 });
             }
             CallToFunctionWith(did) => {
                 tcx.sess.emit_err(CallToFunctionWithRequiresUnsafe {
                     span,
+                    unsafe_not_inherited_note,
                     function: &tcx.def_path_str(*did),
                 });
             }

compiler/rustc_mir_build/src/errors.rs

@@ -119,6 +119,8 @@ pub struct CallToUnsafeFunctionRequiresUnsafe<'a> {
     #[label]
     pub span: Span,
     pub function: &'a str,
+    #[subdiagnostic]
+    pub unsafe_not_inherited_note: Option<UnsafeNotInheritedNote>,
 }
 
 #[derive(Diagnostic)]
@@ -128,6 +130,8 @@ pub struct CallToUnsafeFunctionRequiresUnsafeNameless {
     #[primary_span]
     #[label]
     pub span: Span,
+    #[subdiagnostic]
+    pub unsafe_not_inherited_note: Option<UnsafeNotInheritedNote>,
 }
 
 #[derive(Diagnostic)]
@@ -138,6 +142,8 @@ pub struct CallToUnsafeFunctionRequiresUnsafeUnsafeOpInUnsafeFnAllowed<'a> {
     #[label]
     pub span: Span,
     pub function: &'a str,
+    #[subdiagnostic]
+    pub unsafe_not_inherited_note: Option<UnsafeNotInheritedNote>,
 }
 
 #[derive(Diagnostic)]
@@ -150,6 +156,8 @@ pub struct CallToUnsafeFunctionRequiresUnsafeNamelessUnsafeOpInUnsafeFnAllowed {
     #[primary_span]
     #[label]
     pub span: Span,
+    #[subdiagnostic]
+    pub unsafe_not_inherited_note: Option<UnsafeNotInheritedNote>,
 }
 
 #[derive(Diagnostic)]
@@ -159,6 +167,8 @@ pub struct UseOfInlineAssemblyRequiresUnsafe {
     #[primary_span]
     #[label]
     pub span: Span,
+    #[subdiagnostic]
+    pub unsafe_not_inherited_note: Option<UnsafeNotInheritedNote>,
 }
 
 #[derive(Diagnostic)]
@@ -168,6 +178,8 @@ pub struct UseOfInlineAssemblyRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
     #[primary_span]
     #[label]
     pub span: Span,
+    #[subdiagnostic]
+    pub unsafe_not_inherited_note: Option<UnsafeNotInheritedNote>,
 }
 
 #[derive(Diagnostic)]
@@ -177,6 +189,8 @@ pub struct InitializingTypeWithRequiresUnsafe {
     #[primary_span]
     #[label]
     pub span: Span,
+    #[subdiagnostic]
+    pub unsafe_not_inherited_note: Option<UnsafeNotInheritedNote>,
 }
 
 #[derive(Diagnostic)]
@@ -189,6 +203,8 @@ pub struct InitializingTypeWithRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
     #[primary_span]
     #[label]
     pub span: Span,
+    #[subdiagnostic]
+    pub unsafe_not_inherited_note: Option<UnsafeNotInheritedNote>,
 }
 
 #[derive(Diagnostic)]
@@ -198,6 +214,8 @@ pub struct UseOfMutableStaticRequiresUnsafe {
     #[primary_span]
     #[label]
     pub span: Span,
+    #[subdiagnostic]
+    pub unsafe_not_inherited_note: Option<UnsafeNotInheritedNote>,
 }
 
 #[derive(Diagnostic)]
@@ -207,6 +225,8 @@ pub struct UseOfMutableStaticRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
     #[primary_span]
     #[label]
     pub span: Span,
+    #[subdiagnostic]
+    pub unsafe_not_inherited_note: Option<UnsafeNotInheritedNote>,
 }
 
 #[derive(Diagnostic)]
@@ -216,6 +236,8 @@ pub struct UseOfExternStaticRequiresUnsafe {
     #[primary_span]
     #[label]
     pub span: Span,
+    #[subdiagnostic]
+    pub unsafe_not_inherited_note: Option<UnsafeNotInheritedNote>,
 }
 
 #[derive(Diagnostic)]
@@ -225,6 +247,8 @@ pub struct UseOfExternStaticRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
     #[primary_span]
     #[label]
     pub span: Span,
+    #[subdiagnostic]
+    pub unsafe_not_inherited_note: Option<UnsafeNotInheritedNote>,
 }
 
 #[derive(Diagnostic)]
@@ -234,6 +258,8 @@ pub struct DerefOfRawPointerRequiresUnsafe {
     #[primary_span]
     #[label]
     pub span: Span,
+    #[subdiagnostic]
+    pub unsafe_not_inherited_note: Option<UnsafeNotInheritedNote>,
 }
 
 #[derive(Diagnostic)]
@@ -243,6 +269,8 @@ pub struct DerefOfRawPointerRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
     #[primary_span]
     #[label]
     pub span: Span,
+    #[subdiagnostic]
+    pub unsafe_not_inherited_note: Option<UnsafeNotInheritedNote>,
 }
 
 #[derive(Diagnostic)]
@@ -252,6 +280,8 @@ pub struct AccessToUnionFieldRequiresUnsafe {
     #[primary_span]
     #[label]
     pub span: Span,
+    #[subdiagnostic]
+    pub unsafe_not_inherited_note: Option<UnsafeNotInheritedNote>,
 }
 
 #[derive(Diagnostic)]
@@ -261,6 +291,8 @@ pub struct AccessToUnionFieldRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
     #[primary_span]
     #[label]
     pub span: Span,
+    #[subdiagnostic]
+    pub unsafe_not_inherited_note: Option<UnsafeNotInheritedNote>,
 }
 
 #[derive(Diagnostic)]
@@ -270,6 +302,8 @@ pub struct MutationOfLayoutConstrainedFieldRequiresUnsafe {
     #[primary_span]
     #[label]
     pub span: Span,
+    #[subdiagnostic]
+    pub unsafe_not_inherited_note: Option<UnsafeNotInheritedNote>,
 }
 
 #[derive(Diagnostic)]
@@ -282,6 +316,8 @@ pub struct MutationOfLayoutConstrainedFieldRequiresUnsafeUnsafeOpInUnsafeFnAllow
     #[primary_span]
     #[label]
     pub span: Span,
+    #[subdiagnostic]
+    pub unsafe_not_inherited_note: Option<UnsafeNotInheritedNote>,
 }
 
 #[derive(Diagnostic)]
@@ -291,6 +327,8 @@ pub struct BorrowOfLayoutConstrainedFieldRequiresUnsafe {
     #[primary_span]
     #[label]
     pub span: Span,
+    #[subdiagnostic]
+    pub unsafe_not_inherited_note: Option<UnsafeNotInheritedNote>,
 }
 
 #[derive(Diagnostic)]
@@ -303,6 +341,8 @@ pub struct BorrowOfLayoutConstrainedFieldRequiresUnsafeUnsafeOpInUnsafeFnAllowed
     #[primary_span]
     #[label]
     pub span: Span,
+    #[subdiagnostic]
+    pub unsafe_not_inherited_note: Option<UnsafeNotInheritedNote>,
 }
 
 #[derive(Diagnostic)]
@@ -313,6 +353,8 @@ pub struct CallToFunctionWithRequiresUnsafe<'a> {
     #[label]
     pub span: Span,
     pub function: &'a str,
+    #[subdiagnostic]
+    pub unsafe_not_inherited_note: Option<UnsafeNotInheritedNote>,
 }
 
 #[derive(Diagnostic)]
@@ -323,6 +365,15 @@ pub struct CallToFunctionWithRequiresUnsafeUnsafeOpInUnsafeFnAllowed<'a> {
     #[label]
     pub span: Span,
     pub function: &'a str,
+    #[subdiagnostic]
+    pub unsafe_not_inherited_note: Option<UnsafeNotInheritedNote>,
+}
+
+#[derive(Subdiagnostic)]
+#[label(mir_build_unsafe_not_inherited)]
+pub struct UnsafeNotInheritedNote {
+    #[primary_span]
+    pub span: Span,
 }
 
 #[derive(LintDiagnostic)]

tests/ui/unsafe/unsafe-not-inherited.mirunsafeck.stderr

@@ -1,5 +1,5 @@
 error[E0133]: use of mutable static is unsafe and requires unsafe function or block
-  --> $DIR/unsafe-not-inherited.rs:6:31
+  --> $DIR/unsafe-not-inherited.rs:8:31
    |
 LL |     unsafe {static BAR: u64 = FOO;}
    |     ------                    ^^^ use of mutable static
@@ -9,7 +9,7 @@ LL |     unsafe {static BAR: u64 = FOO;}
    = note: mutable statics can be mutated by multiple threads: aliasing violations or data races will cause undefined behavior
 
 error[E0133]: call to unsafe function is unsafe and requires unsafe function or block
-  --> $DIR/unsafe-not-inherited.rs:18:13
+  --> $DIR/unsafe-not-inherited.rs:20:13
    |
 LL |     unsafe {
    |     ------ items do not inherit unsafety from separate enclosing items

tests/ui/unsafe/unsafe-not-inherited.rs

@@ -1,3 +1,5 @@
+// revisions: mirunsafeck thirunsafeck
+// [thirunsafeck]compile-flags: -Z thir-unsafeck
 #![allow(unused, dead_code)]
 
 static mut FOO: u64 = 0;

tests/ui/unsafe/unsafe-not-inherited.thirunsafeck.stderr

@@ -0,0 +1,24 @@
+error[E0133]: use of mutable static is unsafe and requires unsafe function or block
+  --> $DIR/unsafe-not-inherited.rs:8:31
+   |
+LL |     unsafe {static BAR: u64 = FOO;}
+   |     ------                    ^^^ use of mutable static
+   |     |
+   |     items do not inherit unsafety from separate enclosing items
+   |
+   = note: mutable statics can be mutated by multiple threads: aliasing violations or data races will cause undefined behavior
+
+error[E0133]: call to unsafe function `unsafe_call` is unsafe and requires unsafe function or block
+  --> $DIR/unsafe-not-inherited.rs:20:13
+   |
+LL |     unsafe {
+   |     ------ items do not inherit unsafety from separate enclosing items
+...
+LL |             unsafe_call();
+   |             ^^^^^^^^^^^^^ call to unsafe function
+   |
+   = note: consult the function's documentation for information on how to avoid undefined behavior
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0133`.