rustc_mir_build/
check_unsafety.rs

1use std::borrow::Cow;
2use std::mem;
3use std::ops::Bound;
4
5use rustc_ast::AsmMacro;
6use rustc_data_structures::stack::ensure_sufficient_stack;
7use rustc_errors::DiagArgValue;
8use rustc_hir::attrs::AttributeKind;
9use rustc_hir::def::DefKind;
10use rustc_hir::{self as hir, BindingMode, ByRef, HirId, Mutability, find_attr};
11use rustc_middle::middle::codegen_fn_attrs::{TargetFeature, TargetFeatureKind};
12use rustc_middle::mir::BorrowKind;
13use rustc_middle::span_bug;
14use rustc_middle::thir::visit::Visitor;
15use rustc_middle::thir::*;
16use rustc_middle::ty::print::with_no_trimmed_paths;
17use rustc_middle::ty::{self, Ty, TyCtxt};
18use rustc_session::lint::Level;
19use rustc_session::lint::builtin::{DEPRECATED_SAFE_2024, UNSAFE_OP_IN_UNSAFE_FN, UNUSED_UNSAFE};
20use rustc_span::def_id::{DefId, LocalDefId};
21use rustc_span::{Span, Symbol, sym};
22
23use crate::builder::ExprCategory;
24use crate::errors::*;
25
26struct UnsafetyVisitor<'a, 'tcx> {
27    tcx: TyCtxt<'tcx>,
28    thir: &'a Thir<'tcx>,
29    /// The `HirId` of the current scope, which would be the `HirId`
30    /// of the current HIR node, modulo adjustments. Used for lint levels.
31    hir_context: HirId,
32    /// The current "safety context". This notably tracks whether we are in an
33    /// `unsafe` block, and whether it has been used.
34    safety_context: SafetyContext,
35    /// The `#[target_feature]` attributes of the body. Used for checking
36    /// calls to functions with `#[target_feature]` (RFC 2396).
37    body_target_features: &'tcx [TargetFeature],
38    /// When inside the LHS of an assignment to a field, this is the type
39    /// of the LHS and the span of the assignment expression.
40    assignment_info: Option<Ty<'tcx>>,
41    in_union_destructure: bool,
42    typing_env: ty::TypingEnv<'tcx>,
43    inside_adt: bool,
44    warnings: &'a mut Vec<UnusedUnsafeWarning>,
45
46    /// Flag to ensure that we only suggest wrapping the entire function body in
47    /// an unsafe block once.
48    suggest_unsafe_block: bool,
49}
50
51impl<'tcx> UnsafetyVisitor<'_, 'tcx> {
52    fn in_safety_context(&mut self, safety_context: SafetyContext, f: impl FnOnce(&mut Self)) {
53        let prev_context = mem::replace(&mut self.safety_context, safety_context);
54
55        f(self);
56
57        let safety_context = mem::replace(&mut self.safety_context, prev_context);
58        if let SafetyContext::UnsafeBlock { used, span, hir_id, nested_used_blocks } =
59            safety_context
60        {
61            if !used {
62                self.warn_unused_unsafe(hir_id, span, None);
63
64                if let SafetyContext::UnsafeBlock {
65                    nested_used_blocks: ref mut prev_nested_used_blocks,
66                    ..
67                } = self.safety_context
68                {
69                    prev_nested_used_blocks.extend(nested_used_blocks);
70                }
71            } else {
72                for block in nested_used_blocks {
73                    self.warn_unused_unsafe(
74                        block.hir_id,
75                        block.span,
76                        Some(UnusedUnsafeEnclosing::Block {
77                            span: self.tcx.sess.source_map().guess_head_span(span),
78                        }),
79                    );
80                }
81
82                match self.safety_context {
83                    SafetyContext::UnsafeBlock {
84                        nested_used_blocks: ref mut prev_nested_used_blocks,
85                        ..
86                    } => {
87                        prev_nested_used_blocks.push(NestedUsedBlock { hir_id, span });
88                    }
89                    _ => (),
90                }
91            }
92        }
93    }
94
95    fn emit_deprecated_safe_fn_call(&self, span: Span, kind: &UnsafeOpKind) -> bool {
96        match kind {
97            // Allow calls to deprecated-safe unsafe functions if the caller is
98            // from an edition before 2024.
99            &UnsafeOpKind::CallToUnsafeFunction(Some(id))
100                if !span.at_least_rust_2024()
101                    && let Some(attr) = self.tcx.get_attr(id, sym::rustc_deprecated_safe_2024) =>
102            {
103                let suggestion = attr
104                    .meta_item_list()
105                    .unwrap_or_default()
106                    .into_iter()
107                    .find(|item| item.has_name(sym::audit_that))
108                    .map(|item| {
109                        item.value_str().expect(
110                            "`#[rustc_deprecated_safe_2024(audit_that)]` must have a string value",
111                        )
112                    });
113
114                let sm = self.tcx.sess.source_map();
115                let guarantee = suggestion
116                    .as_ref()
117                    .map(|suggestion| format!("that {}", suggestion))
118                    .unwrap_or_else(|| String::from("its unsafe preconditions"));
119                let suggestion = suggestion
120                    .and_then(|suggestion| {
121                        sm.indentation_before(span).map(|indent| {
122                            format!("{}// TODO: Audit that {}.\n", indent, suggestion) // ignore-tidy-todo
123                        })
124                    })
125                    .unwrap_or_default();
126
127                self.tcx.emit_node_span_lint(
128                    DEPRECATED_SAFE_2024,
129                    self.hir_context,
130                    span,
131                    CallToDeprecatedSafeFnRequiresUnsafe {
132                        span,
133                        function: with_no_trimmed_paths!(self.tcx.def_path_str(id)),
134                        guarantee,
135                        sub: CallToDeprecatedSafeFnRequiresUnsafeSub {
136                            start_of_line_suggestion: suggestion,
137                            start_of_line: sm.span_extend_to_line(span).shrink_to_lo(),
138                            left: span.shrink_to_lo(),
139                            right: span.shrink_to_hi(),
140                        },
141                    },
142                );
143                true
144            }
145            _ => false,
146        }
147    }
148
149    fn requires_unsafe(&mut self, span: Span, kind: UnsafeOpKind) {
150        let unsafe_op_in_unsafe_fn_allowed = self.unsafe_op_in_unsafe_fn_allowed();
151        match self.safety_context {
152            SafetyContext::BuiltinUnsafeBlock => {}
153            SafetyContext::UnsafeBlock { ref mut used, .. } => {
154                // Mark this block as useful (even inside `unsafe fn`, where it is technically
155                // redundant -- but we want to eventually enable `unsafe_op_in_unsafe_fn` by
156                // default which will require those blocks:
157                // https://github.com/rust-lang/rust/issues/71668#issuecomment-1203075594).
158                *used = true;
159            }
160            SafetyContext::UnsafeFn if unsafe_op_in_unsafe_fn_allowed => {}
161            SafetyContext::UnsafeFn => {
162                let deprecated_safe_fn = self.emit_deprecated_safe_fn_call(span, &kind);
163                if !deprecated_safe_fn {
164                    // unsafe_op_in_unsafe_fn is disallowed
165                    kind.emit_unsafe_op_in_unsafe_fn_lint(
166                        self.tcx,
167                        self.hir_context,
168                        span,
169                        self.suggest_unsafe_block,
170                    );
171                    self.suggest_unsafe_block = false;
172                }
173            }
174            SafetyContext::Safe => {
175                let deprecated_safe_fn = self.emit_deprecated_safe_fn_call(span, &kind);
176                if !deprecated_safe_fn {
177                    kind.emit_requires_unsafe_err(
178                        self.tcx,
179                        span,
180                        self.hir_context,
181                        unsafe_op_in_unsafe_fn_allowed,
182                    );
183                }
184            }
185        }
186    }
187
188    fn warn_unused_unsafe(
189        &mut self,
190        hir_id: HirId,
191        block_span: Span,
192        enclosing_unsafe: Option<UnusedUnsafeEnclosing>,
193    ) {
194        self.warnings.push(UnusedUnsafeWarning { hir_id, block_span, enclosing_unsafe });
195    }
196
197    /// Whether the `unsafe_op_in_unsafe_fn` lint is `allow`ed at the current HIR node.
198    fn unsafe_op_in_unsafe_fn_allowed(&self) -> bool {
199        self.tcx.lint_level_at_node(UNSAFE_OP_IN_UNSAFE_FN, self.hir_context).level == Level::Allow
200    }
201
202    /// Handle closures/coroutines/inline-consts, which is unsafecked with their parent body.
203    fn visit_inner_body(&mut self, def: LocalDefId) {
204        if let Ok((inner_thir, expr)) = self.tcx.thir_body(def) {
205            // Run all other queries that depend on THIR.
206            self.tcx.ensure_done().mir_built(def);
207            let inner_thir = if self.tcx.sess.opts.unstable_opts.no_steal_thir {
208                &inner_thir.borrow()
209            } else {
210                // We don't have other use for the THIR. Steal it to reduce memory usage.
211                &inner_thir.steal()
212            };
213            let hir_context = self.tcx.local_def_id_to_hir_id(def);
214            let safety_context = mem::replace(&mut self.safety_context, SafetyContext::Safe);
215            let mut inner_visitor = UnsafetyVisitor {
216                tcx: self.tcx,
217                thir: inner_thir,
218                hir_context,
219                safety_context,
220                body_target_features: self.body_target_features,
221                assignment_info: self.assignment_info,
222                in_union_destructure: false,
223                typing_env: self.typing_env,
224                inside_adt: false,
225                warnings: self.warnings,
226                suggest_unsafe_block: self.suggest_unsafe_block,
227            };
228            // params in THIR may be unsafe, e.g. a union pattern.
229            for param in &inner_thir.params {
230                if let Some(param_pat) = param.pat.as_deref() {
231                    inner_visitor.visit_pat(param_pat);
232                }
233            }
234            // Visit the body.
235            inner_visitor.visit_expr(&inner_thir[expr]);
236            // Unsafe blocks can be used in the inner body, make sure to take it into account
237            self.safety_context = inner_visitor.safety_context;
238        }
239    }
240}
241
242// Searches for accesses to layout constrained fields.
243struct LayoutConstrainedPlaceVisitor<'a, 'tcx> {
244    found: bool,
245    thir: &'a Thir<'tcx>,
246    tcx: TyCtxt<'tcx>,
247}
248
249impl<'a, 'tcx> LayoutConstrainedPlaceVisitor<'a, 'tcx> {
250    fn new(thir: &'a Thir<'tcx>, tcx: TyCtxt<'tcx>) -> Self {
251        Self { found: false, thir, tcx }
252    }
253}
254
255impl<'a, 'tcx> Visitor<'a, 'tcx> for LayoutConstrainedPlaceVisitor<'a, 'tcx> {
256    fn thir(&self) -> &'a Thir<'tcx> {
257        self.thir
258    }
259
260    fn visit_expr(&mut self, expr: &'a Expr<'tcx>) {
261        match expr.kind {
262            ExprKind::Field { lhs, .. } => {
263                if let ty::Adt(adt_def, _) = self.thir[lhs].ty.kind() {
264                    if (Bound::Unbounded, Bound::Unbounded)
265                        != self.tcx.layout_scalar_valid_range(adt_def.did())
266                    {
267                        self.found = true;
268                    }
269                }
270                visit::walk_expr(self, expr);
271            }
272
273            // Keep walking through the expression as long as we stay in the same
274            // place, i.e. the expression is a place expression and not a dereference
275            // (since dereferencing something leads us to a different place).
276            ExprKind::Deref { .. } => {}
277            ref kind if ExprCategory::of(kind).is_none_or(|cat| cat == ExprCategory::Place) => {
278                visit::walk_expr(self, expr);
279            }
280
281            _ => {}
282        }
283    }
284}
285
286impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> {
287    fn thir(&self) -> &'a Thir<'tcx> {
288        self.thir
289    }
290
291    fn visit_block(&mut self, block: &'a Block) {
292        match block.safety_mode {
293            // compiler-generated unsafe code should not count towards the usefulness of
294            // an outer unsafe block
295            BlockSafety::BuiltinUnsafe => {
296                self.in_safety_context(SafetyContext::BuiltinUnsafeBlock, |this| {
297                    visit::walk_block(this, block)
298                });
299            }
300            BlockSafety::ExplicitUnsafe(hir_id) => {
301                let used = matches!(
302                    self.tcx.lint_level_at_node(UNUSED_UNSAFE, hir_id).level,
303                    Level::Allow
304                );
305                self.in_safety_context(
306                    SafetyContext::UnsafeBlock {
307                        span: block.span,
308                        hir_id,
309                        used,
310                        nested_used_blocks: Vec::new(),
311                    },
312                    |this| visit::walk_block(this, block),
313                );
314            }
315            BlockSafety::Safe => {
316                visit::walk_block(self, block);
317            }
318        }
319    }
320
321    fn visit_pat(&mut self, pat: &'a Pat<'tcx>) {
322        if self.in_union_destructure {
323            match pat.kind {
324                PatKind::Missing => unreachable!(),
325                // binding to a variable allows getting stuff out of variable
326                PatKind::Binding { .. }
327                // match is conditional on having this value
328                | PatKind::Constant { .. }
329                | PatKind::Variant { .. }
330                | PatKind::Leaf { .. }
331                | PatKind::Deref { .. }
332                | PatKind::DerefPattern { .. }
333                | PatKind::Range { .. }
334                | PatKind::Slice { .. }
335                | PatKind::Array { .. }
336                // Never constitutes a witness of uninhabitedness.
337                | PatKind::Never => {
338                    self.requires_unsafe(pat.span, AccessToUnionField);
339                    return; // we can return here since this already requires unsafe
340                }
341                // wildcard doesn't read anything.
342                PatKind::Wild |
343                // these just wrap other patterns, which we recurse on below.
344                PatKind::Or { .. } |
345                PatKind::ExpandedConstant { .. } |
346                PatKind::AscribeUserType { .. } |
347                PatKind::Error(_) => {}
348            }
349        };
350
351        match &pat.kind {
352            PatKind::Leaf { subpatterns, .. } => {
353                if let ty::Adt(adt_def, ..) = pat.ty.kind() {
354                    for pat in subpatterns {
355                        if adt_def.non_enum_variant().fields[pat.field].safety.is_unsafe() {
356                            self.requires_unsafe(pat.pattern.span, UseOfUnsafeField);
357                        }
358                    }
359                    if adt_def.is_union() {
360                        let old_in_union_destructure =
361                            std::mem::replace(&mut self.in_union_destructure, true);
362                        visit::walk_pat(self, pat);
363                        self.in_union_destructure = old_in_union_destructure;
364                    } else if (Bound::Unbounded, Bound::Unbounded)
365                        != self.tcx.layout_scalar_valid_range(adt_def.did())
366                    {
367                        let old_inside_adt = std::mem::replace(&mut self.inside_adt, true);
368                        visit::walk_pat(self, pat);
369                        self.inside_adt = old_inside_adt;
370                    } else {
371                        visit::walk_pat(self, pat);
372                    }
373                } else {
374                    visit::walk_pat(self, pat);
375                }
376            }
377            PatKind::Variant { adt_def, args: _, variant_index, subpatterns } => {
378                for pat in subpatterns {
379                    let field = &pat.field;
380                    if adt_def.variant(*variant_index).fields[*field].safety.is_unsafe() {
381                        self.requires_unsafe(pat.pattern.span, UseOfUnsafeField);
382                    }
383                }
384                visit::walk_pat(self, pat);
385            }
386            PatKind::Binding { mode: BindingMode(ByRef::Yes(_, rm), _), ty, .. } => {
387                if self.inside_adt {
388                    let ty::Ref(_, ty, _) = ty.kind() else {
389                        span_bug!(
390                            pat.span,
391                            "ByRef::Yes in pattern, but found non-reference type {}",
392                            ty
393                        );
394                    };
395                    match rm {
396                        Mutability::Not => {
397                            if !ty.is_freeze(self.tcx, self.typing_env) {
398                                self.requires_unsafe(pat.span, BorrowOfLayoutConstrainedField);
399                            }
400                        }
401                        Mutability::Mut { .. } => {
402                            self.requires_unsafe(pat.span, MutationOfLayoutConstrainedField);
403                        }
404                    }
405                }
406                visit::walk_pat(self, pat);
407            }
408            PatKind::Deref { .. } | PatKind::DerefPattern { .. } => {
409                let old_inside_adt = std::mem::replace(&mut self.inside_adt, false);
410                visit::walk_pat(self, pat);
411                self.inside_adt = old_inside_adt;
412            }
413            _ => {
414                visit::walk_pat(self, pat);
415            }
416        }
417    }
418
419    fn visit_expr(&mut self, expr: &'a Expr<'tcx>) {
420        // could we be in the LHS of an assignment to a field?
421        match expr.kind {
422            ExprKind::Field { .. }
423            | ExprKind::VarRef { .. }
424            | ExprKind::UpvarRef { .. }
425            | ExprKind::Scope { .. }
426            | ExprKind::Cast { .. } => {}
427
428            ExprKind::RawBorrow { .. }
429            | ExprKind::Adt { .. }
430            | ExprKind::Array { .. }
431            | ExprKind::Binary { .. }
432            | ExprKind::Block { .. }
433            | ExprKind::Borrow { .. }
434            | ExprKind::Literal { .. }
435            | ExprKind::NamedConst { .. }
436            | ExprKind::NonHirLiteral { .. }
437            | ExprKind::ZstLiteral { .. }
438            | ExprKind::ConstParam { .. }
439            | ExprKind::ConstBlock { .. }
440            | ExprKind::Deref { .. }
441            | ExprKind::Index { .. }
442            | ExprKind::NeverToAny { .. }
443            | ExprKind::PlaceTypeAscription { .. }
444            | ExprKind::ValueTypeAscription { .. }
445            | ExprKind::PlaceUnwrapUnsafeBinder { .. }
446            | ExprKind::ValueUnwrapUnsafeBinder { .. }
447            | ExprKind::WrapUnsafeBinder { .. }
448            | ExprKind::PointerCoercion { .. }
449            | ExprKind::Repeat { .. }
450            | ExprKind::StaticRef { .. }
451            | ExprKind::ThreadLocalRef { .. }
452            | ExprKind::Tuple { .. }
453            | ExprKind::Unary { .. }
454            | ExprKind::Call { .. }
455            | ExprKind::ByUse { .. }
456            | ExprKind::Assign { .. }
457            | ExprKind::AssignOp { .. }
458            | ExprKind::Break { .. }
459            | ExprKind::Closure { .. }
460            | ExprKind::Continue { .. }
461            | ExprKind::ConstContinue { .. }
462            | ExprKind::Return { .. }
463            | ExprKind::Become { .. }
464            | ExprKind::Yield { .. }
465            | ExprKind::Loop { .. }
466            | ExprKind::LoopMatch { .. }
467            | ExprKind::Let { .. }
468            | ExprKind::Match { .. }
469            | ExprKind::Box { .. }
470            | ExprKind::If { .. }
471            | ExprKind::InlineAsm { .. }
472            | ExprKind::LogicalOp { .. }
473            | ExprKind::Use { .. } => {
474                // We don't need to save the old value and restore it
475                // because all the place expressions can't have more
476                // than one child.
477                self.assignment_info = None;
478            }
479        };
480        match expr.kind {
481            ExprKind::Scope { value, lint_level: LintLevel::Explicit(hir_id), region_scope: _ } => {
482                let prev_id = self.hir_context;
483                self.hir_context = hir_id;
484                ensure_sufficient_stack(|| {
485                    self.visit_expr(&self.thir[value]);
486                });
487                self.hir_context = prev_id;
488                return; // don't visit the whole expression
489            }
490            ExprKind::Call { fun, ty: _, args: _, from_hir_call: _, fn_span: _ } => {
491                let fn_ty = self.thir[fun].ty;
492                let sig = fn_ty.fn_sig(self.tcx);
493                let (callee_features, safe_target_features): (&[_], _) = match fn_ty.kind() {
494                    ty::FnDef(func_id, ..) => {
495                        let cg_attrs = self.tcx.codegen_fn_attrs(func_id);
496                        (&cg_attrs.target_features, cg_attrs.safe_target_features)
497                    }
498                    _ => (&[], false),
499                };
500                if sig.safety().is_unsafe() && !safe_target_features {
501                    let func_id = if let ty::FnDef(func_id, _) = fn_ty.kind() {
502                        Some(*func_id)
503                    } else {
504                        None
505                    };
506                    self.requires_unsafe(expr.span, CallToUnsafeFunction(func_id));
507                } else if let &ty::FnDef(func_did, _) = fn_ty.kind() {
508                    if !self
509                        .tcx
510                        .is_target_feature_call_safe(callee_features, self.body_target_features)
511                    {
512                        let missing: Vec<_> = callee_features
513                            .iter()
514                            .copied()
515                            .filter(|feature| {
516                                feature.kind == TargetFeatureKind::Enabled
517                                    && !self
518                                        .body_target_features
519                                        .iter()
520                                        .any(|body_feature| body_feature.name == feature.name)
521                            })
522                            .map(|feature| feature.name)
523                            .collect();
524                        let build_enabled = self
525                            .tcx
526                            .sess
527                            .target_features
528                            .iter()
529                            .copied()
530                            .filter(|feature| missing.contains(feature))
531                            .collect();
532                        self.requires_unsafe(
533                            expr.span,
534                            CallToFunctionWith { function: func_did, missing, build_enabled },
535                        );
536                    }
537                }
538            }
539            ExprKind::RawBorrow { arg, .. } => {
540                if let ExprKind::Scope { value: arg, .. } = self.thir[arg].kind
541                    && let ExprKind::Deref { arg } = self.thir[arg].kind
542                {
543                    // Taking a raw ref to a deref place expr is always safe.
544                    // Make sure the expression we're deref'ing is safe, though.
545                    visit::walk_expr(self, &self.thir[arg]);
546                    return;
547                }
548
549                // Secondly, we allow raw borrows of union field accesses. Peel
550                // any of those off, and recurse normally on the LHS, which should
551                // reject any unsafe operations within.
552                let mut peeled = arg;
553                while let ExprKind::Scope { value: arg, .. } = self.thir[peeled].kind
554                    && let ExprKind::Field { lhs, name: _, variant_index: _ } = self.thir[arg].kind
555                    && let ty::Adt(def, _) = &self.thir[lhs].ty.kind()
556                    && def.is_union()
557                {
558                    peeled = lhs;
559                }
560                visit::walk_expr(self, &self.thir[peeled]);
561                // And return so we don't recurse directly onto the union field access(es).
562                return;
563            }
564            ExprKind::Deref { arg } => {
565                if let ExprKind::StaticRef { def_id, .. } | ExprKind::ThreadLocalRef(def_id) =
566                    self.thir[arg].kind
567                {
568                    if self.tcx.is_mutable_static(def_id) {
569                        self.requires_unsafe(expr.span, UseOfMutableStatic);
570                    } else if self.tcx.is_foreign_item(def_id) {
571                        match self.tcx.def_kind(def_id) {
572                            DefKind::Static { safety: hir::Safety::Safe, .. } => {}
573                            _ => self.requires_unsafe(expr.span, UseOfExternStatic),
574                        }
575                    }
576                } else if self.thir[arg].ty.is_raw_ptr() {
577                    self.requires_unsafe(expr.span, DerefOfRawPointer);
578                }
579            }
580            ExprKind::InlineAsm(box InlineAsmExpr {
581                asm_macro: asm_macro @ (AsmMacro::Asm | AsmMacro::NakedAsm),
582                ref operands,
583                template: _,
584                options: _,
585                line_spans: _,
586            }) => {
587                // The `naked` attribute and the `naked_asm!` block form one atomic unit of
588                // unsafety, and `naked_asm!` does not itself need to be wrapped in an unsafe block.
589                if let AsmMacro::Asm = asm_macro {
590                    self.requires_unsafe(expr.span, UseOfInlineAssembly);
591                }
592
593                // For inline asm, do not use `walk_expr`, since we want to handle the label block
594                // specially.
595                for op in &**operands {
596                    use rustc_middle::thir::InlineAsmOperand::*;
597                    match op {
598                        In { expr, reg: _ }
599                        | Out { expr: Some(expr), reg: _, late: _ }
600                        | InOut { expr, reg: _, late: _ } => self.visit_expr(&self.thir()[*expr]),
601                        SplitInOut { in_expr, out_expr, reg: _, late: _ } => {
602                            self.visit_expr(&self.thir()[*in_expr]);
603                            if let Some(out_expr) = out_expr {
604                                self.visit_expr(&self.thir()[*out_expr]);
605                            }
606                        }
607                        Out { expr: None, reg: _, late: _ }
608                        | Const { value: _, span: _ }
609                        | SymFn { value: _ }
610                        | SymStatic { def_id: _ } => {}
611                        Label { block } => {
612                            // Label blocks are safe context.
613                            // `asm!()` is forced to be wrapped inside unsafe. If there's no special
614                            // treatment, the label blocks would also always be unsafe with no way
615                            // of opting out.
616                            self.in_safety_context(SafetyContext::Safe, |this| {
617                                visit::walk_block(this, &this.thir()[*block])
618                            });
619                        }
620                    }
621                }
622                return;
623            }
624            ExprKind::Adt(box AdtExpr {
625                adt_def,
626                variant_index,
627                args: _,
628                user_ty: _,
629                fields: _,
630                base: _,
631            }) => {
632                if adt_def.variant(variant_index).has_unsafe_fields() {
633                    self.requires_unsafe(expr.span, InitializingTypeWithUnsafeField)
634                }
635                match self.tcx.layout_scalar_valid_range(adt_def.did()) {
636                    (Bound::Unbounded, Bound::Unbounded) => {}
637                    _ => self.requires_unsafe(expr.span, InitializingTypeWith),
638                }
639            }
640            ExprKind::Closure(box ClosureExpr {
641                closure_id,
642                args: _,
643                upvars: _,
644                movability: _,
645                fake_reads: _,
646            }) => {
647                self.visit_inner_body(closure_id);
648            }
649            ExprKind::ConstBlock { did, args: _ } => {
650                let def_id = did.expect_local();
651                self.visit_inner_body(def_id);
652            }
653            ExprKind::Field { lhs, variant_index, name } => {
654                let lhs = &self.thir[lhs];
655                if let ty::Adt(adt_def, _) = lhs.ty.kind() {
656                    if adt_def.variant(variant_index).fields[name].safety.is_unsafe() {
657                        self.requires_unsafe(expr.span, UseOfUnsafeField);
658                    } else if adt_def.is_union() {
659                        if let Some(assigned_ty) = self.assignment_info {
660                            if assigned_ty.needs_drop(self.tcx, self.typing_env) {
661                                // This would be unsafe, but should be outright impossible since we
662                                // reject such unions.
663                                assert!(
664                                    self.tcx.dcx().has_errors().is_some(),
665                                    "union fields that need dropping should be impossible: {assigned_ty}"
666                                );
667                            }
668                        } else {
669                            self.requires_unsafe(expr.span, AccessToUnionField);
670                        }
671                    }
672                }
673            }
674            ExprKind::Assign { lhs, rhs } | ExprKind::AssignOp { lhs, rhs, .. } => {
675                let lhs = &self.thir[lhs];
676                // First, check whether we are mutating a layout constrained field
677                let mut visitor = LayoutConstrainedPlaceVisitor::new(self.thir, self.tcx);
678                visit::walk_expr(&mut visitor, lhs);
679                if visitor.found {
680                    self.requires_unsafe(expr.span, MutationOfLayoutConstrainedField);
681                }
682
683                // Second, check for accesses to union fields. Don't have any
684                // special handling for AssignOp since it causes a read *and*
685                // write to lhs.
686                if matches!(expr.kind, ExprKind::Assign { .. }) {
687                    self.assignment_info = Some(lhs.ty);
688                    visit::walk_expr(self, lhs);
689                    self.assignment_info = None;
690                    visit::walk_expr(self, &self.thir()[rhs]);
691                    return; // We have already visited everything by now.
692                }
693            }
694            ExprKind::Borrow { borrow_kind, arg } => {
695                let mut visitor = LayoutConstrainedPlaceVisitor::new(self.thir, self.tcx);
696                visit::walk_expr(&mut visitor, expr);
697                if visitor.found {
698                    match borrow_kind {
699                        BorrowKind::Fake(_) | BorrowKind::Shared
700                            if !self.thir[arg].ty.is_freeze(self.tcx, self.typing_env) =>
701                        {
702                            self.requires_unsafe(expr.span, BorrowOfLayoutConstrainedField)
703                        }
704                        BorrowKind::Mut { .. } => {
705                            self.requires_unsafe(expr.span, MutationOfLayoutConstrainedField)
706                        }
707                        BorrowKind::Fake(_) | BorrowKind::Shared => {}
708                    }
709                }
710            }
711            ExprKind::PlaceUnwrapUnsafeBinder { .. }
712            | ExprKind::ValueUnwrapUnsafeBinder { .. }
713            | ExprKind::WrapUnsafeBinder { .. } => {
714                self.requires_unsafe(expr.span, UnsafeBinderCast);
715            }
716            _ => {}
717        }
718        visit::walk_expr(self, expr);
719    }
720}
721
722#[derive(Clone)]
723enum SafetyContext {
724    Safe,
725    BuiltinUnsafeBlock,
726    UnsafeFn,
727    UnsafeBlock { span: Span, hir_id: HirId, used: bool, nested_used_blocks: Vec<NestedUsedBlock> },
728}
729
730#[derive(Clone, Copy)]
731struct NestedUsedBlock {
732    hir_id: HirId,
733    span: Span,
734}
735
736struct UnusedUnsafeWarning {
737    hir_id: HirId,
738    block_span: Span,
739    enclosing_unsafe: Option<UnusedUnsafeEnclosing>,
740}
741
742#[derive(Clone, PartialEq)]
743enum UnsafeOpKind {
744    CallToUnsafeFunction(Option<DefId>),
745    UseOfInlineAssembly,
746    InitializingTypeWith,
747    InitializingTypeWithUnsafeField,
748    UseOfMutableStatic,
749    UseOfExternStatic,
750    UseOfUnsafeField,
751    DerefOfRawPointer,
752    AccessToUnionField,
753    MutationOfLayoutConstrainedField,
754    BorrowOfLayoutConstrainedField,
755    CallToFunctionWith {
756        function: DefId,
757        /// Target features enabled in callee's `#[target_feature]` but missing in
758        /// caller's `#[target_feature]`.
759        missing: Vec<Symbol>,
760        /// Target features in `missing` that are enabled at compile time
761        /// (e.g., with `-C target-feature`).
762        build_enabled: Vec<Symbol>,
763    },
764    UnsafeBinderCast,
765}
766
767use UnsafeOpKind::*;
768
769impl UnsafeOpKind {
770    fn emit_unsafe_op_in_unsafe_fn_lint(
771        &self,
772        tcx: TyCtxt<'_>,
773        hir_id: HirId,
774        span: Span,
775        suggest_unsafe_block: bool,
776    ) {
777        if tcx.hir_opt_delegation_sig_id(hir_id.owner.def_id).is_some() {
778            // The body of the delegation item is synthesized, so it makes no sense
779            // to emit this lint.
780            return;
781        }
782        let parent_id = tcx.hir_get_parent_item(hir_id);
783        let parent_owner = tcx.hir_owner_node(parent_id);
784        let should_suggest = parent_owner.fn_sig().is_some_and(|sig| {
785            // Do not suggest for safe target_feature functions
786            matches!(sig.header.safety, hir::HeaderSafety::Normal(hir::Safety::Unsafe))
787        });
788        let unsafe_not_inherited_note = if should_suggest {
789            suggest_unsafe_block.then(|| {
790                let body_span = tcx.hir_body(parent_owner.body_id().unwrap()).value.span;
791                UnsafeNotInheritedLintNote {
792                    signature_span: tcx.def_span(parent_id.def_id),
793                    body_span,
794                }
795            })
796        } else {
797            None
798        };
799        // FIXME: ideally we would want to trim the def paths, but this is not
800        // feasible with the current lint emission API (see issue #106126).
801        match self {
802            CallToUnsafeFunction(Some(did)) => tcx.emit_node_span_lint(
803                UNSAFE_OP_IN_UNSAFE_FN,
804                hir_id,
805                span,
806                UnsafeOpInUnsafeFnCallToUnsafeFunctionRequiresUnsafe {
807                    span,
808                    function: with_no_trimmed_paths!(tcx.def_path_str(*did)),
809                    unsafe_not_inherited_note,
810                },
811            ),
812            CallToUnsafeFunction(None) => tcx.emit_node_span_lint(
813                UNSAFE_OP_IN_UNSAFE_FN,
814                hir_id,
815                span,
816                UnsafeOpInUnsafeFnCallToUnsafeFunctionRequiresUnsafeNameless {
817                    span,
818                    unsafe_not_inherited_note,
819                },
820            ),
821            UseOfInlineAssembly => tcx.emit_node_span_lint(
822                UNSAFE_OP_IN_UNSAFE_FN,
823                hir_id,
824                span,
825                UnsafeOpInUnsafeFnUseOfInlineAssemblyRequiresUnsafe {
826                    span,
827                    unsafe_not_inherited_note,
828                },
829            ),
830            InitializingTypeWith => tcx.emit_node_span_lint(
831                UNSAFE_OP_IN_UNSAFE_FN,
832                hir_id,
833                span,
834                UnsafeOpInUnsafeFnInitializingTypeWithRequiresUnsafe {
835                    span,
836                    unsafe_not_inherited_note,
837                },
838            ),
839            InitializingTypeWithUnsafeField => tcx.emit_node_span_lint(
840                UNSAFE_OP_IN_UNSAFE_FN,
841                hir_id,
842                span,
843                UnsafeOpInUnsafeFnInitializingTypeWithUnsafeFieldRequiresUnsafe {
844                    span,
845                    unsafe_not_inherited_note,
846                },
847            ),
848            UseOfMutableStatic => tcx.emit_node_span_lint(
849                UNSAFE_OP_IN_UNSAFE_FN,
850                hir_id,
851                span,
852                UnsafeOpInUnsafeFnUseOfMutableStaticRequiresUnsafe {
853                    span,
854                    unsafe_not_inherited_note,
855                },
856            ),
857            UseOfExternStatic => tcx.emit_node_span_lint(
858                UNSAFE_OP_IN_UNSAFE_FN,
859                hir_id,
860                span,
861                UnsafeOpInUnsafeFnUseOfExternStaticRequiresUnsafe {
862                    span,
863                    unsafe_not_inherited_note,
864                },
865            ),
866            UseOfUnsafeField => tcx.emit_node_span_lint(
867                UNSAFE_OP_IN_UNSAFE_FN,
868                hir_id,
869                span,
870                UnsafeOpInUnsafeFnUseOfUnsafeFieldRequiresUnsafe {
871                    span,
872                    unsafe_not_inherited_note,
873                },
874            ),
875            DerefOfRawPointer => tcx.emit_node_span_lint(
876                UNSAFE_OP_IN_UNSAFE_FN,
877                hir_id,
878                span,
879                UnsafeOpInUnsafeFnDerefOfRawPointerRequiresUnsafe {
880                    span,
881                    unsafe_not_inherited_note,
882                },
883            ),
884            AccessToUnionField => tcx.emit_node_span_lint(
885                UNSAFE_OP_IN_UNSAFE_FN,
886                hir_id,
887                span,
888                UnsafeOpInUnsafeFnAccessToUnionFieldRequiresUnsafe {
889                    span,
890                    unsafe_not_inherited_note,
891                },
892            ),
893            MutationOfLayoutConstrainedField => tcx.emit_node_span_lint(
894                UNSAFE_OP_IN_UNSAFE_FN,
895                hir_id,
896                span,
897                UnsafeOpInUnsafeFnMutationOfLayoutConstrainedFieldRequiresUnsafe {
898                    span,
899                    unsafe_not_inherited_note,
900                },
901            ),
902            BorrowOfLayoutConstrainedField => tcx.emit_node_span_lint(
903                UNSAFE_OP_IN_UNSAFE_FN,
904                hir_id,
905                span,
906                UnsafeOpInUnsafeFnBorrowOfLayoutConstrainedFieldRequiresUnsafe {
907                    span,
908                    unsafe_not_inherited_note,
909                },
910            ),
911            CallToFunctionWith { function, missing, build_enabled } => tcx.emit_node_span_lint(
912                UNSAFE_OP_IN_UNSAFE_FN,
913                hir_id,
914                span,
915                UnsafeOpInUnsafeFnCallToFunctionWithRequiresUnsafe {
916                    span,
917                    function: with_no_trimmed_paths!(tcx.def_path_str(*function)),
918                    missing_target_features: DiagArgValue::StrListSepByAnd(
919                        missing.iter().map(|feature| Cow::from(feature.to_string())).collect(),
920                    ),
921                    missing_target_features_count: missing.len(),
922                    note: !build_enabled.is_empty(),
923                    build_target_features: DiagArgValue::StrListSepByAnd(
924                        build_enabled
925                            .iter()
926                            .map(|feature| Cow::from(feature.to_string()))
927                            .collect(),
928                    ),
929                    build_target_features_count: build_enabled.len(),
930                    unsafe_not_inherited_note,
931                },
932            ),
933            UnsafeBinderCast => tcx.emit_node_span_lint(
934                UNSAFE_OP_IN_UNSAFE_FN,
935                hir_id,
936                span,
937                UnsafeOpInUnsafeFnUnsafeBinderCastRequiresUnsafe {
938                    span,
939                    unsafe_not_inherited_note,
940                },
941            ),
942        }
943    }
944
945    fn emit_requires_unsafe_err(
946        &self,
947        tcx: TyCtxt<'_>,
948        span: Span,
949        hir_context: HirId,
950        unsafe_op_in_unsafe_fn_allowed: bool,
951    ) {
952        let note_non_inherited = tcx.hir_parent_iter(hir_context).find(|(id, node)| {
953            if let hir::Node::Expr(block) = node
954                && let hir::ExprKind::Block(block, _) = block.kind
955                && let hir::BlockCheckMode::UnsafeBlock(_) = block.rules
956            {
957                true
958            } else if let Some(sig) = tcx.hir_fn_sig_by_hir_id(*id)
959                && matches!(sig.header.safety, hir::HeaderSafety::Normal(hir::Safety::Unsafe))
960            {
961                true
962            } else {
963                false
964            }
965        });
966        let unsafe_not_inherited_note = if let Some((id, _)) = note_non_inherited {
967            let span = tcx.hir_span(id);
968            let span = tcx.sess.source_map().guess_head_span(span);
969            Some(UnsafeNotInheritedNote { span })
970        } else {
971            None
972        };
973
974        let dcx = tcx.dcx();
975        match self {
976            CallToUnsafeFunction(Some(did)) if unsafe_op_in_unsafe_fn_allowed => {
977                dcx.emit_err(CallToUnsafeFunctionRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
978                    span,
979                    unsafe_not_inherited_note,
980                    function: tcx.def_path_str(*did),
981                });
982            }
983            CallToUnsafeFunction(Some(did)) => {
984                dcx.emit_err(CallToUnsafeFunctionRequiresUnsafe {
985                    span,
986                    unsafe_not_inherited_note,
987                    function: tcx.def_path_str(*did),
988                });
989            }
990            CallToUnsafeFunction(None) if unsafe_op_in_unsafe_fn_allowed => {
991                dcx.emit_err(CallToUnsafeFunctionRequiresUnsafeNamelessUnsafeOpInUnsafeFnAllowed {
992                    span,
993                    unsafe_not_inherited_note,
994                });
995            }
996            CallToUnsafeFunction(None) => {
997                dcx.emit_err(CallToUnsafeFunctionRequiresUnsafeNameless {
998                    span,
999                    unsafe_not_inherited_note,
1000                });
1001            }
1002            UseOfInlineAssembly if unsafe_op_in_unsafe_fn_allowed => {
1003                dcx.emit_err(UseOfInlineAssemblyRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
1004                    span,
1005                    unsafe_not_inherited_note,
1006                });
1007            }
1008            UseOfInlineAssembly => {
1009                dcx.emit_err(UseOfInlineAssemblyRequiresUnsafe { span, unsafe_not_inherited_note });
1010            }
1011            InitializingTypeWith if unsafe_op_in_unsafe_fn_allowed => {
1012                dcx.emit_err(InitializingTypeWithRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
1013                    span,
1014                    unsafe_not_inherited_note,
1015                });
1016            }
1017            InitializingTypeWith => {
1018                dcx.emit_err(InitializingTypeWithRequiresUnsafe {
1019                    span,
1020                    unsafe_not_inherited_note,
1021                });
1022            }
1023            InitializingTypeWithUnsafeField if unsafe_op_in_unsafe_fn_allowed => {
1024                dcx.emit_err(
1025                    InitializingTypeWithUnsafeFieldRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
1026                        span,
1027                        unsafe_not_inherited_note,
1028                    },
1029                );
1030            }
1031            InitializingTypeWithUnsafeField => {
1032                dcx.emit_err(InitializingTypeWithUnsafeFieldRequiresUnsafe {
1033                    span,
1034                    unsafe_not_inherited_note,
1035                });
1036            }
1037            UseOfMutableStatic if unsafe_op_in_unsafe_fn_allowed => {
1038                dcx.emit_err(UseOfMutableStaticRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
1039                    span,
1040                    unsafe_not_inherited_note,
1041                });
1042            }
1043            UseOfMutableStatic => {
1044                dcx.emit_err(UseOfMutableStaticRequiresUnsafe { span, unsafe_not_inherited_note });
1045            }
1046            UseOfExternStatic if unsafe_op_in_unsafe_fn_allowed => {
1047                dcx.emit_err(UseOfExternStaticRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
1048                    span,
1049                    unsafe_not_inherited_note,
1050                });
1051            }
1052            UseOfExternStatic => {
1053                dcx.emit_err(UseOfExternStaticRequiresUnsafe { span, unsafe_not_inherited_note });
1054            }
1055            UseOfUnsafeField if unsafe_op_in_unsafe_fn_allowed => {
1056                dcx.emit_err(UseOfUnsafeFieldRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
1057                    span,
1058                    unsafe_not_inherited_note,
1059                });
1060            }
1061            UseOfUnsafeField => {
1062                dcx.emit_err(UseOfUnsafeFieldRequiresUnsafe { span, unsafe_not_inherited_note });
1063            }
1064            DerefOfRawPointer if unsafe_op_in_unsafe_fn_allowed => {
1065                dcx.emit_err(DerefOfRawPointerRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
1066                    span,
1067                    unsafe_not_inherited_note,
1068                });
1069            }
1070            DerefOfRawPointer => {
1071                dcx.emit_err(DerefOfRawPointerRequiresUnsafe { span, unsafe_not_inherited_note });
1072            }
1073            AccessToUnionField if unsafe_op_in_unsafe_fn_allowed => {
1074                dcx.emit_err(AccessToUnionFieldRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
1075                    span,
1076                    unsafe_not_inherited_note,
1077                });
1078            }
1079            AccessToUnionField => {
1080                dcx.emit_err(AccessToUnionFieldRequiresUnsafe { span, unsafe_not_inherited_note });
1081            }
1082            MutationOfLayoutConstrainedField if unsafe_op_in_unsafe_fn_allowed => {
1083                dcx.emit_err(
1084                    MutationOfLayoutConstrainedFieldRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
1085                        span,
1086                        unsafe_not_inherited_note,
1087                    },
1088                );
1089            }
1090            MutationOfLayoutConstrainedField => {
1091                dcx.emit_err(MutationOfLayoutConstrainedFieldRequiresUnsafe {
1092                    span,
1093                    unsafe_not_inherited_note,
1094                });
1095            }
1096            BorrowOfLayoutConstrainedField if unsafe_op_in_unsafe_fn_allowed => {
1097                dcx.emit_err(
1098                    BorrowOfLayoutConstrainedFieldRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
1099                        span,
1100                        unsafe_not_inherited_note,
1101                    },
1102                );
1103            }
1104            BorrowOfLayoutConstrainedField => {
1105                dcx.emit_err(BorrowOfLayoutConstrainedFieldRequiresUnsafe {
1106                    span,
1107                    unsafe_not_inherited_note,
1108                });
1109            }
1110            CallToFunctionWith { function, missing, build_enabled }
1111                if unsafe_op_in_unsafe_fn_allowed =>
1112            {
1113                dcx.emit_err(CallToFunctionWithRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
1114                    span,
1115                    missing_target_features: DiagArgValue::StrListSepByAnd(
1116                        missing.iter().map(|feature| Cow::from(feature.to_string())).collect(),
1117                    ),
1118                    missing_target_features_count: missing.len(),
1119                    note: !build_enabled.is_empty(),
1120                    build_target_features: DiagArgValue::StrListSepByAnd(
1121                        build_enabled
1122                            .iter()
1123                            .map(|feature| Cow::from(feature.to_string()))
1124                            .collect(),
1125                    ),
1126                    build_target_features_count: build_enabled.len(),
1127                    unsafe_not_inherited_note,
1128                    function: tcx.def_path_str(*function),
1129                });
1130            }
1131            CallToFunctionWith { function, missing, build_enabled } => {
1132                dcx.emit_err(CallToFunctionWithRequiresUnsafe {
1133                    span,
1134                    missing_target_features: DiagArgValue::StrListSepByAnd(
1135                        missing.iter().map(|feature| Cow::from(feature.to_string())).collect(),
1136                    ),
1137                    missing_target_features_count: missing.len(),
1138                    note: !build_enabled.is_empty(),
1139                    build_target_features: DiagArgValue::StrListSepByAnd(
1140                        build_enabled
1141                            .iter()
1142                            .map(|feature| Cow::from(feature.to_string()))
1143                            .collect(),
1144                    ),
1145                    build_target_features_count: build_enabled.len(),
1146                    unsafe_not_inherited_note,
1147                    function: tcx.def_path_str(*function),
1148                });
1149            }
1150            UnsafeBinderCast if unsafe_op_in_unsafe_fn_allowed => {
1151                dcx.emit_err(UnsafeBinderCastRequiresUnsafeUnsafeOpInUnsafeFnAllowed {
1152                    span,
1153                    unsafe_not_inherited_note,
1154                });
1155            }
1156            UnsafeBinderCast => {
1157                dcx.emit_err(UnsafeBinderCastRequiresUnsafe { span, unsafe_not_inherited_note });
1158            }
1159        }
1160    }
1161}
1162
1163pub(crate) fn check_unsafety(tcx: TyCtxt<'_>, def: LocalDefId) {
1164    // Closures and inline consts are handled by their owner, if it has a body
1165    assert!(!tcx.is_typeck_child(def.to_def_id()));
1166    // Also, don't safety check custom MIR
1167    if find_attr!(tcx.get_all_attrs(def), AttributeKind::CustomMir(..) => ()).is_some() {
1168        return;
1169    }
1170
1171    let Ok((thir, expr)) = tcx.thir_body(def) else { return };
1172    // Runs all other queries that depend on THIR.
1173    tcx.ensure_done().mir_built(def);
1174    let thir = if tcx.sess.opts.unstable_opts.no_steal_thir {
1175        &thir.borrow()
1176    } else {
1177        // We don't have other use for the THIR. Steal it to reduce memory usage.
1178        &thir.steal()
1179    };
1180
1181    let hir_id = tcx.local_def_id_to_hir_id(def);
1182    let safety_context = tcx.hir_fn_sig_by_hir_id(hir_id).map_or(SafetyContext::Safe, |fn_sig| {
1183        match fn_sig.header.safety {
1184            // We typeck the body as safe, but otherwise treat it as unsafe everywhere else.
1185            // Call sites to other SafeTargetFeatures functions are checked explicitly and don't need
1186            // to care about safety of the body.
1187            hir::HeaderSafety::SafeTargetFeatures => SafetyContext::Safe,
1188            hir::HeaderSafety::Normal(safety) => match safety {
1189                hir::Safety::Unsafe => SafetyContext::UnsafeFn,
1190                hir::Safety::Safe => SafetyContext::Safe,
1191            },
1192        }
1193    });
1194    let body_target_features = &tcx.body_codegen_attrs(def.to_def_id()).target_features;
1195    let mut warnings = Vec::new();
1196    let mut visitor = UnsafetyVisitor {
1197        tcx,
1198        thir,
1199        safety_context,
1200        hir_context: hir_id,
1201        body_target_features,
1202        assignment_info: None,
1203        in_union_destructure: false,
1204        // FIXME(#132279): we're clearly in a body here.
1205        typing_env: ty::TypingEnv::non_body_analysis(tcx, def),
1206        inside_adt: false,
1207        warnings: &mut warnings,
1208        suggest_unsafe_block: true,
1209    };
1210    // params in THIR may be unsafe, e.g. a union pattern.
1211    for param in &thir.params {
1212        if let Some(param_pat) = param.pat.as_deref() {
1213            visitor.visit_pat(param_pat);
1214        }
1215    }
1216    // Visit the body.
1217    visitor.visit_expr(&thir[expr]);
1218
1219    warnings.sort_by_key(|w| w.block_span);
1220    for UnusedUnsafeWarning { hir_id, block_span, enclosing_unsafe } in warnings {
1221        let block_span = tcx.sess.source_map().guess_head_span(block_span);
1222        tcx.emit_node_span_lint(
1223            UNUSED_UNSAFE,
1224            hir_id,
1225            block_span,
1226            UnusedUnsafe { span: block_span, enclosing: enclosing_unsafe },
1227        );
1228    }
1229}
rustc_mir_build/check_unsafety.rs

rustc_mir_build/
check_unsafety.rs
