compiler/rustc_mir/src/transform/check_unsafety.rs

   1 use rustc_data_structures::fx::FxHashSet;
   2 use rustc_errors::struct_span_err;
   3 use rustc_hir as hir;
   4 use rustc_hir::def_id::{DefId, LocalDefId};
   5 use rustc_hir::hir_id::HirId;
   6 use rustc_hir::intravisit;
   7 use rustc_hir::Node;
   8 use rustc_middle::mir::visit::{MutatingUseContext, PlaceContext, Visitor};
   9 use rustc_middle::mir::*;
  10 use rustc_middle::ty::cast::CastTy;
  11 use rustc_middle::ty::query::Providers;
  12 use rustc_middle::ty::{self, TyCtxt};
  13 use rustc_session::lint::builtin::{UNSAFE_OP_IN_UNSAFE_FN, UNUSED_UNSAFE};
  14 use rustc_session::lint::Level;
  15
  16 use std::ops::Bound;
  17
  18 pub struct UnsafetyChecker<'a, 'tcx> {
  19     body: &'a Body<'tcx>,
  20     body_did: LocalDefId,
  21     const_context: bool,
  22     violations: Vec<UnsafetyViolation>,
  23     source_info: SourceInfo,
  24     tcx: TyCtxt<'tcx>,
  25     param_env: ty::ParamEnv<'tcx>,
  26     /// Mark an `unsafe` block as used, so we don't lint it.
  27     used_unsafe: FxHashSet<hir::HirId>,
  28     inherited_blocks: Vec<(hir::HirId, bool)>,
  29 }
  30
  31 impl<'a, 'tcx> UnsafetyChecker<'a, 'tcx> {
  32     fn new(
  33         const_context: bool,
  34         body: &'a Body<'tcx>,
  35         body_did: LocalDefId,
  36         tcx: TyCtxt<'tcx>,
  37         param_env: ty::ParamEnv<'tcx>,
  38     ) -> Self {
  39         Self {
  40             body,
  41             body_did,
  42             const_context,
  43             violations: vec![],
  44             source_info: SourceInfo::outermost(body.span),
  45             tcx,
  46             param_env,
  47             used_unsafe: Default::default(),
  48             inherited_blocks: vec![],
  49         }
  50     }
  51 }
  52
  53 impl<'a, 'tcx> Visitor<'tcx> for UnsafetyChecker<'a, 'tcx> {
  54     fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location) {
  55         self.source_info = terminator.source_info;
  56         match terminator.kind {
  57             TerminatorKind::Goto { .. }
  58             | TerminatorKind::SwitchInt { .. }
  59             | TerminatorKind::Drop { .. }
  60             | TerminatorKind::Yield { .. }
  61             | TerminatorKind::Assert { .. }
  62             | TerminatorKind::DropAndReplace { .. }
  63             | TerminatorKind::GeneratorDrop
  64             | TerminatorKind::Resume
  65             | TerminatorKind::Abort
  66             | TerminatorKind::Return
  67             | TerminatorKind::Unreachable
  68             | TerminatorKind::FalseEdge { .. }
  69             | TerminatorKind::FalseUnwind { .. } => {
  70                 // safe (at least as emitted during MIR construction)
  71             }
  72
  73             TerminatorKind::Call { ref func, .. } => {
  74                 let func_ty = func.ty(self.body, self.tcx);
  75                 let sig = func_ty.fn_sig(self.tcx);
  76                 if let hir::Unsafety::Unsafe = sig.unsafety() {
  77                     self.require_unsafe(
  78                         UnsafetyViolationKind::General,
  79                         UnsafetyViolationDetails::CallToUnsafeFunction,
  80                     )
  81                 }
  82
  83                 if let ty::FnDef(func_id, _) = func_ty.kind() {
  84                     self.check_target_features(*func_id);
  85                 }
  86             }
  87
  88             TerminatorKind::InlineAsm { .. } => self.require_unsafe(
  89                 UnsafetyViolationKind::General,
  90                 UnsafetyViolationDetails::UseOfInlineAssembly,
  91             ),
  92         }
  93         self.super_terminator(terminator, location);
  94     }
  95
  96     fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) {
  97         self.source_info = statement.source_info;
  98         match statement.kind {
  99             StatementKind::Assign(..)
 100             | StatementKind::FakeRead(..)
 101             | StatementKind::SetDiscriminant { .. }
 102             | StatementKind::StorageLive(..)
 103             | StatementKind::StorageDead(..)
 104             | StatementKind::Retag { .. }
 105             | StatementKind::AscribeUserType(..)
 106             | StatementKind::Coverage(..)
 107             | StatementKind::Nop => {
 108                 // safe (at least as emitted during MIR construction)
 109             }
 110
 111             StatementKind::LlvmInlineAsm { .. } => self.require_unsafe(
 112                 UnsafetyViolationKind::General,
 113                 UnsafetyViolationDetails::UseOfInlineAssembly,
 114             ),
 115             StatementKind::CopyNonOverlapping(..) => unreachable!(),
 116         }
 117         self.super_statement(statement, location);
 118     }
 119
 120     fn visit_rvalue(&mut self, rvalue: &Rvalue<'tcx>, location: Location) {
 121         match rvalue {
 122             Rvalue::Aggregate(box ref aggregate, _) => match aggregate {
 123                 &AggregateKind::Array(..) | &AggregateKind::Tuple => {}
 124                 &AggregateKind::Adt(ref def, ..) => {
 125                     match self.tcx.layout_scalar_valid_range(def.did) {
 126                         (Bound::Unbounded, Bound::Unbounded) => {}
 127                         _ => self.require_unsafe(
 128                             UnsafetyViolationKind::General,
 129                             UnsafetyViolationDetails::InitializingTypeWith,
 130                         ),
 131                     }
 132                 }
 133                 &AggregateKind::Closure(def_id, _) | &AggregateKind::Generator(def_id, _, _) => {
 134                     let UnsafetyCheckResult { violations, unsafe_blocks } =
 135                         self.tcx.unsafety_check_result(def_id.expect_local());
 136                     self.register_violations(&violations, &unsafe_blocks);
 137                 }
 138             },
 139             // casting pointers to ints is unsafe in const fn because the const evaluator cannot
 140             // possibly know what the result of various operations like `address / 2` would be
 141             // pointers during const evaluation have no integral address, only an abstract one
 142             Rvalue::Cast(CastKind::Misc, ref operand, cast_ty)
 143                 if self.const_context && self.tcx.features().const_raw_ptr_to_usize_cast =>
 144             {
 145                 let operand_ty = operand.ty(self.body, self.tcx);
 146                 let cast_in = CastTy::from_ty(operand_ty).expect("bad input type for cast");
 147                 let cast_out = CastTy::from_ty(cast_ty).expect("bad output type for cast");
 148                 match (cast_in, cast_out) {
 149                     (CastTy::Ptr(_) | CastTy::FnPtr, CastTy::Int(_)) => {
 150                         self.require_unsafe(
 151                             UnsafetyViolationKind::General,
 152                             UnsafetyViolationDetails::CastOfPointerToInt,
 153                         );
 154                     }
 155                     _ => {}
 156                 }
 157             }
 158             _ => {}
 159         }
 160         self.super_rvalue(rvalue, location);
 161     }
 162
 163     fn visit_place(&mut self, place: &Place<'tcx>, context: PlaceContext, _location: Location) {
 164         // On types with `scalar_valid_range`, prevent
 165         // * `&mut x.field`
 166         // * `x.field = y;`
 167         // * `&x.field` if `field`'s type has interior mutability
 168         // because either of these would allow modifying the layout constrained field and
 169         // insert values that violate the layout constraints.
 170         if context.is_mutating_use() || context.is_borrow() {
 171             self.check_mut_borrowing_layout_constrained_field(*place, context.is_mutating_use());
 172         }
 173
 174         // Some checks below need the extra metainfo of the local declaration.
 175         let decl = &self.body.local_decls[place.local];
 176
 177         // Check the base local: it might be an unsafe-to-access static. We only check derefs of the
 178         // temporary holding the static pointer to avoid duplicate errors
 179         // <https://github.com/rust-lang/rust/pull/78068#issuecomment-731753506>.
 180         if decl.internal && place.projection.first() == Some(&ProjectionElem::Deref) {
 181             // If the projection root is an artifical local that we introduced when
 182             // desugaring `static`, give a more specific error message
 183             // (avoid the general "raw pointer" clause below, that would only be confusing).
 184             if let Some(box LocalInfo::StaticRef { def_id, .. }) = decl.local_info {
 185                 if self.tcx.is_mutable_static(def_id) {
 186                     self.require_unsafe(
 187                         UnsafetyViolationKind::General,
 188                         UnsafetyViolationDetails::UseOfMutableStatic,
 189                     );
 190                     return;
 191                 } else if self.tcx.is_foreign_item(def_id) {
 192                     self.require_unsafe(
 193                         UnsafetyViolationKind::General,
 194                         UnsafetyViolationDetails::UseOfExternStatic,
 195                     );
 196                     return;
 197                 }
 198             }
 199         }
 200
 201         // Check for raw pointer `Deref`.
 202         for (base, proj) in place.iter_projections() {
 203             if proj == ProjectionElem::Deref {
 204                 let base_ty = base.ty(self.body, self.tcx).ty;
 205                 if base_ty.is_unsafe_ptr() {
 206                     self.require_unsafe(
 207                         UnsafetyViolationKind::General,
 208                         UnsafetyViolationDetails::DerefOfRawPointer,
 209                     )
 210                 }
 211             }
 212         }
 213
 214         // Check for union fields. For this we traverse right-to-left, as the last `Deref` changes
 215         // whether we *read* the union field or potentially *write* to it (if this place is being assigned to).
 216         let mut saw_deref = false;
 217         for (base, proj) in place.iter_projections().rev() {
 218             if proj == ProjectionElem::Deref {
 219                 saw_deref = true;
 220                 continue;
 221             }
 222
 223             let base_ty = base.ty(self.body, self.tcx).ty;
 224             if base_ty.is_union() {
 225                 // If we did not hit a `Deref` yet and the overall place use is an assignment, the
 226                 // rules are different.
 227                 let assign_to_field = !saw_deref
 228                     && matches!(
 229                         context,
 230                         PlaceContext::MutatingUse(
 231                             MutatingUseContext::Store
 232                                 | MutatingUseContext::Drop
 233                                 | MutatingUseContext::AsmOutput
 234                         )
 235                     );
 236                 // If this is just an assignment, determine if the assigned type needs dropping.
 237                 if assign_to_field {
 238                     // We have to check the actual type of the assignment, as that determines if the
 239                     // old value is being dropped.
 240                     let assigned_ty = place.ty(&self.body.local_decls, self.tcx).ty;
 241                     // To avoid semver hazard, we only consider `Copy` and `ManuallyDrop` non-dropping.
 242                     let manually_drop = assigned_ty
 243                         .ty_adt_def()
 244                         .map_or(false, |adt_def| adt_def.is_manually_drop());
 245                     let nodrop = manually_drop
 246                         || assigned_ty.is_copy_modulo_regions(
 247                             self.tcx.at(self.source_info.span),
 248                             self.param_env,
 249                         );
 250                     if !nodrop {
 251                         self.require_unsafe(
 252                             UnsafetyViolationKind::General,
 253                             UnsafetyViolationDetails::AssignToDroppingUnionField,
 254                         );
 255                     } else {
 256                         // write to non-drop union field, safe
 257                     }
 258                 } else {
 259                     self.require_unsafe(
 260                         UnsafetyViolationKind::General,
 261                         UnsafetyViolationDetails::AccessToUnionField,
 262                     )
 263                 }
 264             }
 265         }
 266     }
 267 }
 268
 269 impl<'a, 'tcx> UnsafetyChecker<'a, 'tcx> {
 270     fn require_unsafe(&mut self, kind: UnsafetyViolationKind, details: UnsafetyViolationDetails) {
 271         // Violations can turn out to be `UnsafeFn` during analysis, but they should not start out as such.
 272         assert_ne!(kind, UnsafetyViolationKind::UnsafeFn);
 273
 274         let source_info = self.source_info;
 275         let lint_root = self.body.source_scopes[self.source_info.scope]
 276             .local_data
 277             .as_ref()
 278             .assert_crate_local()
 279             .lint_root;
 280         self.register_violations(
 281             &[UnsafetyViolation { source_info, lint_root, kind, details }],
 282             &[],
 283         );
 284     }
 285
 286     fn register_violations(
 287         &mut self,
 288         violations: &[UnsafetyViolation],
 289         unsafe_blocks: &[(hir::HirId, bool)],
 290     ) {
 291         let safety = self.body.source_scopes[self.source_info.scope]
 292             .local_data
 293             .as_ref()
 294             .assert_crate_local()
 295             .safety;
 296         let within_unsafe = match safety {
 297             // `unsafe` blocks are required in safe code
 298             Safety::Safe => {
 299                 for violation in violations {
 300                     match violation.kind {
 301                         UnsafetyViolationKind::General => {}
 302                         UnsafetyViolationKind::UnsafeFn => {
 303                             bug!("`UnsafetyViolationKind::UnsafeFn` in an `Safe` context")
 304                         }
 305                     }
 306                     if !self.violations.contains(violation) {
 307                         self.violations.push(*violation)
 308                     }
 309                 }
 310                 false
 311             }
 312             // With the RFC 2585, no longer allow `unsafe` operations in `unsafe fn`s
 313             Safety::FnUnsafe => {
 314                 for violation in violations {
 315                     let mut violation = *violation;
 316
 317                     violation.kind = UnsafetyViolationKind::UnsafeFn;
 318                     if !self.violations.contains(&violation) {
 319                         self.violations.push(violation)
 320                     }
 321                 }
 322                 false
 323             }
 324             Safety::ExplicitUnsafe(hir_id) => {
 325                 // mark unsafe block as used if there are any unsafe operations inside
 326                 if !violations.is_empty() {
 327                     self.used_unsafe.insert(hir_id);
 328                 }
 329                 true
 330             }
 331         };
 332         self.inherited_blocks.extend(
 333             unsafe_blocks.iter().map(|&(hir_id, is_used)| (hir_id, is_used && !within_unsafe)),
 334         );
 335     }
 336     fn check_mut_borrowing_layout_constrained_field(
 337         &mut self,
 338         place: Place<'tcx>,
 339         is_mut_use: bool,
 340     ) {
 341         for (place_base, elem) in place.iter_projections().rev() {
 342             match elem {
 343                 // Modifications behind a dereference don't affect the value of
 344                 // the pointer.
 345                 ProjectionElem::Deref => return,
 346                 ProjectionElem::Field(..) => {
 347                     let ty = place_base.ty(&self.body.local_decls, self.tcx).ty;
 348                     if let ty::Adt(def, _) = ty.kind() {
 349                         if self.tcx.layout_scalar_valid_range(def.did)
 350                             != (Bound::Unbounded, Bound::Unbounded)
 351                         {
 352                             let details = if is_mut_use {
 353                                 UnsafetyViolationDetails::MutationOfLayoutConstrainedField
 354
 355                             // Check `is_freeze` as late as possible to avoid cycle errors
 356                             // with opaque types.
 357                             } else if !place
 358                                 .ty(self.body, self.tcx)
 359                                 .ty
 360                                 .is_freeze(self.tcx.at(self.source_info.span), self.param_env)
 361                             {
 362                                 UnsafetyViolationDetails::BorrowOfLayoutConstrainedField
 363                             } else {
 364                                 continue;
 365                             };
 366                             self.require_unsafe(UnsafetyViolationKind::General, details);
 367                         }
 368                     }
 369                 }
 370                 _ => {}
 371             }
 372         }
 373     }
 374
 375     /// Checks whether calling `func_did` needs an `unsafe` context or not, i.e. whether
 376     /// the called function has target features the calling function hasn't.
 377     fn check_target_features(&mut self, func_did: DefId) {
 378         // Unsafety isn't required on wasm targets. For more information see
 379         // the corresponding check in typeck/src/collect.rs
 380         if self.tcx.sess.target.options.is_like_wasm {
 381             return;
 382         }
 383
 384         let callee_features = &self.tcx.codegen_fn_attrs(func_did).target_features;
 385         let self_features = &self.tcx.codegen_fn_attrs(self.body_did).target_features;
 386
 387         // Is `callee_features` a subset of `calling_features`?
 388         if !callee_features.iter().all(|feature| self_features.contains(feature)) {
 389             self.require_unsafe(
 390                 UnsafetyViolationKind::General,
 391                 UnsafetyViolationDetails::CallToFunctionWith,
 392             )
 393         }
 394     }
 395 }
 396
 397 pub(crate) fn provide(providers: &mut Providers) {
 398     *providers = Providers {
 399         unsafety_check_result: |tcx, def_id| {
 400             if let Some(def) = ty::WithOptConstParam::try_lookup(def_id, tcx) {
 401                 tcx.unsafety_check_result_for_const_arg(def)
 402             } else {
 403                 unsafety_check_result(tcx, ty::WithOptConstParam::unknown(def_id))
 404             }
 405         },
 406         unsafety_check_result_for_const_arg: |tcx, (did, param_did)| {
 407             unsafety_check_result(
 408                 tcx,
 409                 ty::WithOptConstParam { did, const_param_did: Some(param_did) },
 410             )
 411         },
 412         ..*providers
 413     };
 414 }
 415
 416 struct UnusedUnsafeVisitor<'a> {
 417     used_unsafe: &'a FxHashSet<hir::HirId>,
 418     unsafe_blocks: &'a mut Vec<(hir::HirId, bool)>,
 419 }
 420
 421 impl<'a, 'tcx> intravisit::Visitor<'tcx> for UnusedUnsafeVisitor<'a> {
 422     type Map = intravisit::ErasedMap<'tcx>;
 423
 424     fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
 425         intravisit::NestedVisitorMap::None
 426     }
 427
 428     fn visit_block(&mut self, block: &'tcx hir::Block<'tcx>) {
 429         intravisit::walk_block(self, block);
 430
 431         if let hir::BlockCheckMode::UnsafeBlock(hir::UnsafeSource::UserProvided) = block.rules {
 432             self.unsafe_blocks.push((block.hir_id, self.used_unsafe.contains(&block.hir_id)));
 433         }
 434     }
 435 }
 436
 437 fn check_unused_unsafe(
 438     tcx: TyCtxt<'_>,
 439     def_id: LocalDefId,
 440     used_unsafe: &FxHashSet<hir::HirId>,
 441     unsafe_blocks: &mut Vec<(hir::HirId, bool)>,
 442 ) {
 443     let body_id = tcx.hir().maybe_body_owned_by(tcx.hir().local_def_id_to_hir_id(def_id));
 444
 445     let body_id = match body_id {
 446         Some(body) => body,
 447         None => {
 448             debug!("check_unused_unsafe({:?}) - no body found", def_id);
 449             return;
 450         }
 451     };
 452     let body = tcx.hir().body(body_id);
 453     debug!("check_unused_unsafe({:?}, body={:?}, used_unsafe={:?})", def_id, body, used_unsafe);
 454
 455     let mut visitor = UnusedUnsafeVisitor { used_unsafe, unsafe_blocks };
 456     intravisit::Visitor::visit_body(&mut visitor, body);
 457 }
 458
 459 fn unsafety_check_result<'tcx>(
 460     tcx: TyCtxt<'tcx>,
 461     def: ty::WithOptConstParam<LocalDefId>,
 462 ) -> &'tcx UnsafetyCheckResult {
 463     debug!("unsafety_violations({:?})", def);
 464
 465     // N.B., this borrow is valid because all the consumers of
 466     // `mir_built` force this.
 467     let body = &tcx.mir_built(def).borrow();
 468
 469     let param_env = tcx.param_env(def.did);
 470
 471     let id = tcx.hir().local_def_id_to_hir_id(def.did);
 472     let const_context = match tcx.hir().body_owner_kind(id) {
 473         hir::BodyOwnerKind::Closure => false,
 474         hir::BodyOwnerKind::Fn => tcx.is_const_fn_raw(def.did.to_def_id()),
 475         hir::BodyOwnerKind::Const | hir::BodyOwnerKind::Static(_) => true,
 476     };
 477     let mut checker = UnsafetyChecker::new(const_context, body, def.did, tcx, param_env);
 478     checker.visit_body(&body);
 479
 480     check_unused_unsafe(tcx, def.did, &checker.used_unsafe, &mut checker.inherited_blocks);
 481
 482     tcx.arena.alloc(UnsafetyCheckResult {
 483         violations: checker.violations.into(),
 484         unsafe_blocks: checker.inherited_blocks.into(),
 485     })
 486 }
 487
 488 /// Returns the `HirId` for an enclosing scope that is also `unsafe`.
 489 fn is_enclosed(
 490     tcx: TyCtxt<'_>,
 491     used_unsafe: &FxHashSet<hir::HirId>,
 492     id: hir::HirId,
 493     unsafe_op_in_unsafe_fn_allowed: bool,
 494 ) -> Option<(&'static str, hir::HirId)> {
 495     let parent_id = tcx.hir().get_parent_node(id);
 496     if parent_id != id {
 497         if used_unsafe.contains(&parent_id) {
 498             Some(("block", parent_id))
 499         } else if let Some(Node::Item(&hir::Item {
 500             kind: hir::ItemKind::Fn(ref sig, _, _), ..
 501         })) = tcx.hir().find(parent_id)
 502         {
 503             if sig.header.unsafety == hir::Unsafety::Unsafe && unsafe_op_in_unsafe_fn_allowed {
 504                 Some(("fn", parent_id))
 505             } else {
 506                 None
 507             }
 508         } else {
 509             is_enclosed(tcx, used_unsafe, parent_id, unsafe_op_in_unsafe_fn_allowed)
 510         }
 511     } else {
 512         None
 513     }
 514 }
 515
 516 fn report_unused_unsafe(tcx: TyCtxt<'_>, used_unsafe: &FxHashSet<hir::HirId>, id: hir::HirId) {
 517     let span = tcx.sess.source_map().guess_head_span(tcx.hir().span(id));
 518     tcx.struct_span_lint_hir(UNUSED_UNSAFE, id, span, |lint| {
 519         let msg = "unnecessary `unsafe` block";
 520         let mut db = lint.build(msg);
 521         db.span_label(span, msg);
 522         if let Some((kind, id)) =
 523             is_enclosed(tcx, used_unsafe, id, unsafe_op_in_unsafe_fn_allowed(tcx, id))
 524         {
 525             db.span_label(
 526                 tcx.sess.source_map().guess_head_span(tcx.hir().span(id)),
 527                 format!("because it's nested under this `unsafe` {}", kind),
 528             );
 529         }
 530         db.emit();
 531     });
 532 }
 533
 534 pub fn check_unsafety(tcx: TyCtxt<'_>, def_id: LocalDefId) {
 535     debug!("check_unsafety({:?})", def_id);
 536
 537     // closures are handled by their parent fn.
 538     if tcx.is_closure(def_id.to_def_id()) {
 539         return;
 540     }
 541
 542     let UnsafetyCheckResult { violations, unsafe_blocks } = tcx.unsafety_check_result(def_id);
 543
 544     for &UnsafetyViolation { source_info, lint_root, kind, details } in violations.iter() {
 545         let (description, note) = details.description_and_note();
 546
 547         // Report an error.
 548         let unsafe_fn_msg =
 549             if unsafe_op_in_unsafe_fn_allowed(tcx, lint_root) { " function or" } else { "" };
 550
 551         match kind {
 552             UnsafetyViolationKind::General => {
 553                 // once
 554                 struct_span_err!(
 555                     tcx.sess,
 556                     source_info.span,
 557                     E0133,
 558                     "{} is unsafe and requires unsafe{} block",
 559                     description,
 560                     unsafe_fn_msg,
 561                 )
 562                 .span_label(source_info.span, description)
 563                 .note(note)
 564                 .emit();
 565             }
 566             UnsafetyViolationKind::UnsafeFn => tcx.struct_span_lint_hir(
 567                 UNSAFE_OP_IN_UNSAFE_FN,
 568                 lint_root,
 569                 source_info.span,
 570                 |lint| {
 571                     lint.build(&format!(
 572                         "{} is unsafe and requires unsafe block (error E0133)",
 573                         description,
 574                     ))
 575                     .span_label(source_info.span, description)
 576                     .note(note)
 577                     .emit();
 578                 },
 579             ),
 580         }
 581     }
 582
 583     let (mut unsafe_used, mut unsafe_unused): (FxHashSet<_>, Vec<_>) = Default::default();
 584     for &(block_id, is_used) in unsafe_blocks.iter() {
 585         if is_used {
 586             unsafe_used.insert(block_id);
 587         } else {
 588             unsafe_unused.push(block_id);
 589         }
 590     }
 591     // The unused unsafe blocks might not be in source order; sort them so that the unused unsafe
 592     // error messages are properly aligned and the issue-45107 and lint-unused-unsafe tests pass.
 593     unsafe_unused.sort_by_cached_key(|hir_id| tcx.hir().span(*hir_id));
 594
 595     for &block_id in &unsafe_unused {
 596         report_unused_unsafe(tcx, &unsafe_used, block_id);
 597     }
 598 }
 599
 600 fn unsafe_op_in_unsafe_fn_allowed(tcx: TyCtxt<'_>, id: HirId) -> bool {
 601     tcx.lint_level_at_node(UNSAFE_OP_IN_UNSAFE_FN, id).0 == Level::Allow
 602 }