1 use super::deconstruct_pat::{Constructor, DeconstructedPat};
2 use super::usefulness::{
3 compute_match_usefulness, MatchArm, MatchCheckCtxt, Reachability, UsefulnessReport,
5 use super::{PatCtxt, PatternError};
7 use rustc_arena::TypedArena;
8 use rustc_ast::Mutability;
10 error_code, struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed,
13 use rustc_hir::def::*;
14 use rustc_hir::def_id::DefId;
15 use rustc_hir::intravisit::{self, Visitor};
16 use rustc_hir::{HirId, Pat};
17 use rustc_middle::ty::{self, AdtDef, Ty, TyCtxt};
18 use rustc_session::lint::builtin::{
19 BINDINGS_WITH_VARIANT_NAME, IRREFUTABLE_LET_PATTERNS, UNREACHABLE_PATTERNS,
21 use rustc_session::Session;
22 use rustc_span::source_map::Spanned;
23 use rustc_span::{DesugaringKind, ExpnKind, Span};
25 crate fn check_match(tcx: TyCtxt<'_>, def_id: DefId) {
26 let body_id = match def_id.as_local() {
28 Some(id) => tcx.hir().body_owned_by(tcx.hir().local_def_id_to_hir_id(id)),
31 let pattern_arena = TypedArena::default();
32 let mut visitor = MatchVisitor {
34 typeck_results: tcx.typeck_body(body_id),
35 param_env: tcx.param_env(def_id),
36 pattern_arena: &pattern_arena,
38 visitor.visit_body(tcx.hir().body(body_id));
44 error_message: String,
45 ) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
46 struct_span_err!(sess, sp, E0004, "{}", &error_message)
56 struct MatchVisitor<'a, 'p, 'tcx> {
58 typeck_results: &'a ty::TypeckResults<'tcx>,
59 param_env: ty::ParamEnv<'tcx>,
60 pattern_arena: &'p TypedArena<DeconstructedPat<'p, 'tcx>>,
63 impl<'tcx> Visitor<'tcx> for MatchVisitor<'_, '_, 'tcx> {
64 fn visit_expr(&mut self, ex: &'tcx hir::Expr<'tcx>) {
65 intravisit::walk_expr(self, ex);
67 hir::ExprKind::Match(scrut, arms, source) => self.check_match(scrut, arms, *source),
68 hir::ExprKind::Let(hir::Let { pat, init, span, .. }) => {
69 self.check_let(pat, init, *span)
75 fn visit_local(&mut self, loc: &'tcx hir::Local<'tcx>) {
76 intravisit::walk_local(self, loc);
78 let (msg, sp) = match loc.source {
79 hir::LocalSource::Normal => ("local binding", Some(loc.span)),
80 hir::LocalSource::AsyncFn => ("async fn binding", None),
81 hir::LocalSource::AwaitDesugar => ("`await` future binding", None),
82 hir::LocalSource::AssignDesugar(_) => ("destructuring assignment binding", None),
84 self.check_irrefutable(&loc.pat, msg, sp);
87 fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) {
88 intravisit::walk_param(self, param);
89 self.check_irrefutable(¶m.pat, "function argument", None);
93 impl PatCtxt<'_, '_> {
94 fn report_inlining_errors(&self) {
95 for error in &self.errors {
97 PatternError::StaticInPattern(span) => {
98 self.span_e0158(span, "statics cannot be referenced in patterns")
100 PatternError::AssocConstInPattern(span) => {
101 self.span_e0158(span, "associated consts cannot be referenced in patterns")
103 PatternError::ConstParamInPattern(span) => {
104 self.span_e0158(span, "const parameters cannot be referenced in patterns")
106 PatternError::NonConstPath(span) => {
107 rustc_middle::mir::interpret::struct_error(
109 "runtime values cannot be referenced in patterns",
117 fn span_e0158(&self, span: Span, text: &str) {
118 struct_span_err!(self.tcx.sess, span, E0158, "{}", text).emit();
122 impl<'p, 'tcx> MatchVisitor<'_, 'p, 'tcx> {
123 fn check_patterns(&self, pat: &Pat<'_>, rf: RefutableFlag) {
124 pat.walk_always(|pat| check_borrow_conflicts_in_at_patterns(self, pat));
125 check_for_bindings_named_same_as_variants(self, pat, rf);
130 cx: &mut MatchCheckCtxt<'p, 'tcx>,
131 pat: &'tcx hir::Pat<'tcx>,
132 have_errors: &mut bool,
133 ) -> &'p DeconstructedPat<'p, 'tcx> {
134 let mut patcx = PatCtxt::new(self.tcx, self.param_env, self.typeck_results);
135 patcx.include_lint_checks();
136 let pattern = patcx.lower_pattern(pat);
137 let pattern: &_ = cx.pattern_arena.alloc(DeconstructedPat::from_pat(cx, &pattern));
138 if !patcx.errors.is_empty() {
140 patcx.report_inlining_errors();
145 fn new_cx(&self, hir_id: HirId) -> MatchCheckCtxt<'p, 'tcx> {
148 param_env: self.param_env,
149 module: self.tcx.parent_module(hir_id).to_def_id(),
150 pattern_arena: &self.pattern_arena,
154 fn check_let(&mut self, pat: &'tcx hir::Pat<'tcx>, scrutinee: &hir::Expr<'_>, span: Span) {
155 self.check_patterns(pat, Refutable);
156 let mut cx = self.new_cx(scrutinee.hir_id);
157 let tpat = self.lower_pattern(&mut cx, pat, &mut false);
158 check_let_reachability(&mut cx, pat.hir_id, tpat, span);
163 scrut: &hir::Expr<'_>,
164 hir_arms: &'tcx [hir::Arm<'tcx>],
165 source: hir::MatchSource,
167 let mut cx = self.new_cx(scrut.hir_id);
169 for arm in hir_arms {
170 // Check the arm for some things unrelated to exhaustiveness.
171 self.check_patterns(&arm.pat, Refutable);
172 if let Some(hir::Guard::IfLet(ref pat, _)) = arm.guard {
173 self.check_patterns(pat, Refutable);
174 let tpat = self.lower_pattern(&mut cx, pat, &mut false);
175 check_let_reachability(&mut cx, pat.hir_id, tpat, tpat.span());
179 let mut have_errors = false;
181 let arms: Vec<_> = hir_arms
183 .map(|hir::Arm { pat, guard, .. }| MatchArm {
184 pat: self.lower_pattern(&mut cx, pat, &mut have_errors),
186 has_guard: guard.is_some(),
190 // Bail out early if lowering failed.
195 let scrut_ty = self.typeck_results.expr_ty_adjusted(scrut);
196 let report = compute_match_usefulness(&cx, &arms, scrut.hir_id, scrut_ty);
199 // Don't report arm reachability of desugared `match $iter.into_iter() { iter => .. }`
200 // when the iterator is an uninhabited type. unreachable_code will trigger instead.
201 hir::MatchSource::ForLoopDesugar if arms.len() == 1 => {}
202 hir::MatchSource::ForLoopDesugar | hir::MatchSource::Normal => {
203 report_arm_reachability(&cx, &report)
205 // Unreachable patterns in try and await expressions occur when one of
206 // the arms are an uninhabited type. Which is OK.
207 hir::MatchSource::AwaitDesugar | hir::MatchSource::TryDesugar => {}
210 // Check if the match is exhaustive.
211 let is_empty_match = arms.is_empty();
212 let witnesses = report.non_exhaustiveness_witnesses;
213 if !witnesses.is_empty() {
214 if source == hir::MatchSource::ForLoopDesugar && hir_arms.len() == 2 {
215 // the for loop pattern is not irrefutable
216 let pat = hir_arms[1].pat.for_loop_some().unwrap();
217 self.check_irrefutable(pat, "`for` loop binding", None);
219 non_exhaustive_match(&cx, scrut_ty, scrut.span, witnesses, is_empty_match);
224 fn check_irrefutable(&self, pat: &'tcx Pat<'tcx>, origin: &str, sp: Option<Span>) {
225 let mut cx = self.new_cx(pat.hir_id);
227 let pattern = self.lower_pattern(&mut cx, pat, &mut false);
228 let pattern_ty = pattern.ty();
229 let arms = vec![MatchArm { pat: pattern, hir_id: pat.hir_id, has_guard: false }];
230 let report = compute_match_usefulness(&cx, &arms, pat.hir_id, pattern_ty);
232 // Note: we ignore whether the pattern is unreachable (i.e. whether the type is empty). We
233 // only care about exhaustiveness here.
234 let witnesses = report.non_exhaustiveness_witnesses;
235 if witnesses.is_empty() {
236 // The pattern is irrefutable.
237 self.check_patterns(pat, Irrefutable);
241 let joined_patterns = joined_uncovered_patterns(&cx, &witnesses);
242 let mut err = struct_span_err!(
246 "refutable pattern in {}: {} not covered",
250 let suggest_if_let = match &pat.kind {
251 hir::PatKind::Path(hir::QPath::Resolved(None, path))
252 if path.segments.len() == 1 && path.segments[0].args.is_none() =>
254 const_not_var(&mut err, cx.tcx, pat, path);
258 err.span_label(pat.span, pattern_not_covered_label(&witnesses, &joined_patterns));
263 if let (Some(span), true) = (sp, suggest_if_let) {
265 "`let` bindings require an \"irrefutable pattern\", like a `struct` or \
266 an `enum` with only one variant",
268 if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) {
271 "you might want to use `if let` to ignore the variant that isn't matched",
272 format!("if {} {{ /* */ }}", &snippet[..snippet.len() - 1]),
273 Applicability::HasPlaceholders,
277 "for more information, visit \
278 https://doc.rust-lang.org/book/ch18-02-refutability.html",
282 adt_defined_here(&cx, &mut err, pattern_ty, &witnesses);
283 err.note(&format!("the matched value is of type `{}`", pattern_ty));
288 /// A path pattern was interpreted as a constant, not a new variable.
289 /// This caused an irrefutable match failure in e.g. `let`.
290 fn const_not_var(err: &mut Diagnostic, tcx: TyCtxt<'_>, pat: &Pat<'_>, path: &hir::Path<'_>) {
291 let descr = path.res.descr();
294 format!("interpreted as {} {} pattern, not a new variable", path.res.article(), descr,),
299 "introduce a variable instead",
300 format!("{}_var", path.segments[0].ident).to_lowercase(),
301 // Cannot use `MachineApplicable` as it's not really *always* correct
302 // because there may be such an identifier in scope or the user maybe
303 // really wanted to match against the constant. This is quite unlikely however.
304 Applicability::MaybeIncorrect,
307 if let Some(span) = tcx.hir().res_span(path.res) {
308 err.span_label(span, format!("{} defined here", descr));
312 fn check_for_bindings_named_same_as_variants(
313 cx: &MatchVisitor<'_, '_, '_>,
317 pat.walk_always(|p| {
318 if let hir::PatKind::Binding(_, _, ident, None) = p.kind
319 && let Some(ty::BindByValue(hir::Mutability::Not)) =
320 cx.typeck_results.extract_binding_mode(cx.tcx.sess, p.hir_id, p.span)
321 && let pat_ty = cx.typeck_results.pat_ty(p).peel_refs()
322 && let ty::Adt(edef, _) = pat_ty.kind()
324 && edef.variants.iter().any(|variant| {
325 variant.ident(cx.tcx) == ident && variant.ctor_kind == CtorKind::Const
328 let variant_count = edef.variants.len();
329 cx.tcx.struct_span_lint_hir(
330 BINDINGS_WITH_VARIANT_NAME,
334 let ty_path = cx.tcx.def_path_str(edef.did);
335 let mut err = lint.build(&format!(
336 "pattern binding `{}` is named the same as one \
337 of the variants of the type `{}`",
340 err.code(error_code!(E0170));
341 // If this is an irrefutable pattern, and there's > 1 variant,
342 // then we can't actually match on this. Applying the below
343 // suggestion would produce code that breaks on `check_irrefutable`.
344 if rf == Refutable || variant_count == 1 {
347 "to match on the variant, qualify the path",
348 format!("{}::{}", ty_path, ident),
349 Applicability::MachineApplicable,
359 /// Checks for common cases of "catchall" patterns that may not be intended as such.
360 fn pat_is_catchall(pat: &DeconstructedPat<'_, '_>) -> bool {
364 Single => pat.iter_fields().all(|pat| pat_is_catchall(pat)),
369 fn unreachable_pattern(tcx: TyCtxt<'_>, span: Span, id: HirId, catchall: Option<Span>) {
370 tcx.struct_span_lint_hir(UNREACHABLE_PATTERNS, id, span, |lint| {
371 let mut err = lint.build("unreachable pattern");
372 if let Some(catchall) = catchall {
373 // We had a catchall pattern, hint at that.
374 err.span_label(span, "unreachable pattern");
375 err.span_label(catchall, "matches any value");
381 fn irrefutable_let_pattern(tcx: TyCtxt<'_>, id: HirId, span: Span) {
382 macro_rules! emit_diag {
389 let mut diag = $lint.build(concat!("irrefutable ", $source_name, " pattern"));
390 diag.note(concat!("this pattern will always match, so the ", $note_sufix));
391 diag.help(concat!("consider ", $help_sufix));
396 let source = let_source(tcx, id);
397 let span = match source {
398 LetSource::LetElse(span) => span,
401 tcx.struct_span_lint_hir(IRREFUTABLE_LET_PATTERNS, id, span, |lint| match source {
402 LetSource::GenericLet => {
403 emit_diag!(lint, "`let`", "`let` is useless", "removing `let`");
405 LetSource::IfLet => {
409 "`if let` is useless",
410 "replacing the `if let` with a `let`"
413 LetSource::IfLetGuard => {
418 "removing the guard and adding a `let` inside the match arm"
421 LetSource::LetElse(..) => {
425 "`else` clause is useless",
426 "removing the `else` clause"
429 LetSource::WhileLet => {
433 "loop will never exit",
434 "instead using a `loop { ... }` with a `let` inside it"
440 fn check_let_reachability<'p, 'tcx>(
441 cx: &mut MatchCheckCtxt<'p, 'tcx>,
443 pat: &'p DeconstructedPat<'p, 'tcx>,
446 if is_let_chain(cx.tcx, pat_id) {
450 let arms = [MatchArm { pat, hir_id: pat_id, has_guard: false }];
451 let report = compute_match_usefulness(&cx, &arms, pat_id, pat.ty());
453 // Report if the pattern is unreachable, which can only occur when the type is uninhabited.
454 // This also reports unreachable sub-patterns though, so we can't just replace it with an
455 // `is_uninhabited` check.
456 report_arm_reachability(&cx, &report);
458 if report.non_exhaustiveness_witnesses.is_empty() {
459 // The match is exhaustive, i.e. the `if let` pattern is irrefutable.
460 irrefutable_let_pattern(cx.tcx, pat_id, span);
464 /// Report unreachable arms, if any.
465 fn report_arm_reachability<'p, 'tcx>(
466 cx: &MatchCheckCtxt<'p, 'tcx>,
467 report: &UsefulnessReport<'p, 'tcx>,
470 let mut catchall = None;
471 for (arm, is_useful) in report.arm_usefulness.iter() {
473 Unreachable => unreachable_pattern(cx.tcx, arm.pat.span(), arm.hir_id, catchall),
474 Reachable(unreachables) if unreachables.is_empty() => {}
475 // The arm is reachable, but contains unreachable subpatterns (from or-patterns).
476 Reachable(unreachables) => {
477 let mut unreachables = unreachables.clone();
478 // Emit lints in the order in which they occur in the file.
479 unreachables.sort_unstable();
480 for span in unreachables {
481 unreachable_pattern(cx.tcx, span, arm.hir_id, None);
485 if !arm.has_guard && catchall.is_none() && pat_is_catchall(arm.pat) {
486 catchall = Some(arm.pat.span());
491 /// Report that a match is not exhaustive.
492 fn non_exhaustive_match<'p, 'tcx>(
493 cx: &MatchCheckCtxt<'p, 'tcx>,
496 witnesses: Vec<DeconstructedPat<'p, 'tcx>>,
497 is_empty_match: bool,
499 let non_empty_enum = match scrut_ty.kind() {
500 ty::Adt(def, _) => def.is_enum() && !def.variants.is_empty(),
503 // In the case of an empty match, replace the '`_` not covered' diagnostic with something more
506 if is_empty_match && !non_empty_enum {
510 format!("non-exhaustive patterns: type `{}` is non-empty", scrut_ty),
513 let joined_patterns = joined_uncovered_patterns(cx, &witnesses);
517 format!("non-exhaustive patterns: {} not covered", joined_patterns),
519 err.span_label(sp, pattern_not_covered_label(&witnesses, &joined_patterns));
522 let is_variant_list_non_exhaustive = match scrut_ty.kind() {
523 ty::Adt(def, _) if def.is_variant_list_non_exhaustive() && !def.did.is_local() => true,
527 adt_defined_here(cx, &mut err, scrut_ty, &witnesses);
529 "ensure that all possible cases are being handled, \
530 possibly by adding wildcards or more match arms",
533 "the matched value is of type `{}`{}",
535 if is_variant_list_non_exhaustive { ", which is marked as non-exhaustive" } else { "" }
537 if (scrut_ty == cx.tcx.types.usize || scrut_ty == cx.tcx.types.isize)
539 && witnesses.len() == 1
540 && matches!(witnesses[0].ctor(), Constructor::NonExhaustive)
543 "`{}` does not have a fixed maximum value, \
544 so a wildcard `_` is necessary to match exhaustively",
547 if cx.tcx.sess.is_nightly_build() {
549 "add `#![feature(precise_pointer_size_matching)]` \
550 to the crate attributes to enable precise `{}` matching",
555 if let ty::Ref(_, sub_ty, _) = scrut_ty.kind() {
556 if cx.tcx.is_ty_uninhabited_from(cx.module, *sub_ty, cx.param_env) {
557 err.note("references are always considered inhabited");
563 crate fn joined_uncovered_patterns<'p, 'tcx>(
564 cx: &MatchCheckCtxt<'p, 'tcx>,
565 witnesses: &[DeconstructedPat<'p, 'tcx>],
567 const LIMIT: usize = 3;
568 let pat_to_str = |pat: &DeconstructedPat<'p, 'tcx>| pat.to_pat(cx).to_string();
571 [witness] => format!("`{}`", witness.to_pat(cx)),
572 [head @ .., tail] if head.len() < LIMIT => {
573 let head: Vec<_> = head.iter().map(pat_to_str).collect();
574 format!("`{}` and `{}`", head.join("`, `"), tail.to_pat(cx))
577 let (head, tail) = witnesses.split_at(LIMIT);
578 let head: Vec<_> = head.iter().map(pat_to_str).collect();
579 format!("`{}` and {} more", head.join("`, `"), tail.len())
584 crate fn pattern_not_covered_label(
585 witnesses: &[DeconstructedPat<'_, '_>],
586 joined_patterns: &str,
588 format!("pattern{} {} not covered", rustc_errors::pluralize!(witnesses.len()), joined_patterns)
591 /// Point at the definition of non-covered `enum` variants.
592 fn adt_defined_here<'p, 'tcx>(
593 cx: &MatchCheckCtxt<'p, 'tcx>,
594 err: &mut Diagnostic,
596 witnesses: &[DeconstructedPat<'p, 'tcx>],
598 let ty = ty.peel_refs();
599 if let ty::Adt(def, _) = ty.kind() {
600 if let Some(sp) = cx.tcx.hir().span_if_local(def.did) {
601 err.span_label(sp, format!("`{}` defined here", ty));
604 if witnesses.len() < 4 {
605 for sp in maybe_point_at_variant(cx, def, witnesses.iter()) {
606 err.span_label(sp, "not covered");
612 fn maybe_point_at_variant<'a, 'p: 'a, 'tcx: 'a>(
613 cx: &MatchCheckCtxt<'p, 'tcx>,
615 patterns: impl Iterator<Item = &'a DeconstructedPat<'p, 'tcx>>,
618 let mut covered = vec![];
619 for pattern in patterns {
620 if let Variant(variant_index) = pattern.ctor() {
621 if let ty::Adt(this_def, _) = pattern.ty().kind() && this_def.did != def.did {
624 let sp = def.variants[*variant_index].ident(cx.tcx).span;
625 if covered.contains(&sp) {
626 // Don't point at variants that have already been covered due to other patterns to avoid
632 covered.extend(maybe_point_at_variant(cx, def, pattern.iter_fields()));
637 /// Check if a by-value binding is by-value. That is, check if the binding's type is not `Copy`.
638 fn is_binding_by_move(cx: &MatchVisitor<'_, '_, '_>, hir_id: HirId, span: Span) -> bool {
639 !cx.typeck_results.node_type(hir_id).is_copy_modulo_regions(cx.tcx.at(span), cx.param_env)
642 /// Check that there are no borrow or move conflicts in `binding @ subpat` patterns.
644 /// For example, this would reject:
645 /// - `ref x @ Some(ref mut y)`,
646 /// - `ref mut x @ Some(ref y)`,
647 /// - `ref mut x @ Some(ref mut y)`,
648 /// - `ref mut? x @ Some(y)`, and
649 /// - `x @ Some(ref mut? y)`.
651 /// This analysis is *not* subsumed by NLL.
652 fn check_borrow_conflicts_in_at_patterns(cx: &MatchVisitor<'_, '_, '_>, pat: &Pat<'_>) {
653 // Extract `sub` in `binding @ sub`.
654 let (name, sub) = match &pat.kind {
655 hir::PatKind::Binding(.., name, Some(sub)) => (*name, sub),
658 let binding_span = pat.span.with_hi(name.span.hi());
660 let typeck_results = cx.typeck_results;
661 let sess = cx.tcx.sess;
663 // Get the binding move, extract the mutability if by-ref.
664 let mut_outer = match typeck_results.extract_binding_mode(sess, pat.hir_id, pat.span) {
665 Some(ty::BindByValue(_)) if is_binding_by_move(cx, pat.hir_id, pat.span) => {
666 // We have `x @ pat` where `x` is by-move. Reject all borrows in `pat`.
667 let mut conflicts_ref = Vec::new();
668 sub.each_binding(|_, hir_id, span, _| {
669 match typeck_results.extract_binding_mode(sess, hir_id, span) {
670 Some(ty::BindByValue(_)) | None => {}
671 Some(ty::BindByReference(_)) => conflicts_ref.push(span),
674 if !conflicts_ref.is_empty() {
675 let occurs_because = format!(
676 "move occurs because `{}` has type `{}` which does not implement the `Copy` trait",
678 typeck_results.node_type(pat.hir_id),
680 sess.struct_span_err(pat.span, "borrow of moved value")
681 .span_label(binding_span, format!("value moved into `{}` here", name))
682 .span_label(binding_span, occurs_because)
683 .span_labels(conflicts_ref, "value borrowed here after move")
688 Some(ty::BindByValue(_)) | None => return,
689 Some(ty::BindByReference(m)) => m,
692 // We now have `ref $mut_outer binding @ sub` (semantically).
693 // Recurse into each binding in `sub` and find mutability or move conflicts.
694 let mut conflicts_move = Vec::new();
695 let mut conflicts_mut_mut = Vec::new();
696 let mut conflicts_mut_ref = Vec::new();
697 sub.each_binding(|_, hir_id, span, name| {
698 match typeck_results.extract_binding_mode(sess, hir_id, span) {
699 Some(ty::BindByReference(mut_inner)) => match (mut_outer, mut_inner) {
700 (Mutability::Not, Mutability::Not) => {} // Both sides are `ref`.
701 (Mutability::Mut, Mutability::Mut) => conflicts_mut_mut.push((span, name)), // 2x `ref mut`.
702 _ => conflicts_mut_ref.push((span, name)), // `ref` + `ref mut` in either direction.
704 Some(ty::BindByValue(_)) if is_binding_by_move(cx, hir_id, span) => {
705 conflicts_move.push((span, name)) // `ref mut?` + by-move conflict.
707 Some(ty::BindByValue(_)) | None => {} // `ref mut?` + by-copy is fine.
711 // Report errors if any.
712 if !conflicts_mut_mut.is_empty() {
713 // Report mutability conflicts for e.g. `ref mut x @ Some(ref mut y)`.
715 .struct_span_err(pat.span, "cannot borrow value as mutable more than once at a time");
716 err.span_label(binding_span, format!("first mutable borrow, by `{}`, occurs here", name));
717 for (span, name) in conflicts_mut_mut {
718 err.span_label(span, format!("another mutable borrow, by `{}`, occurs here", name));
720 for (span, name) in conflicts_mut_ref {
721 err.span_label(span, format!("also borrowed as immutable, by `{}`, here", name));
723 for (span, name) in conflicts_move {
724 err.span_label(span, format!("also moved into `{}` here", name));
727 } else if !conflicts_mut_ref.is_empty() {
728 // Report mutability conflicts for e.g. `ref x @ Some(ref mut y)` or the converse.
729 let (primary, also) = match mut_outer {
730 Mutability::Mut => ("mutable", "immutable"),
731 Mutability::Not => ("immutable", "mutable"),
734 format!("cannot borrow value as {} because it is also borrowed as {}", also, primary);
735 let mut err = sess.struct_span_err(pat.span, &msg);
736 err.span_label(binding_span, format!("{} borrow, by `{}`, occurs here", primary, name));
737 for (span, name) in conflicts_mut_ref {
738 err.span_label(span, format!("{} borrow, by `{}`, occurs here", also, name));
740 for (span, name) in conflicts_move {
741 err.span_label(span, format!("also moved into `{}` here", name));
744 } else if !conflicts_move.is_empty() {
745 // Report by-ref and by-move conflicts, e.g. `ref x @ y`.
747 sess.struct_span_err(pat.span, "cannot move out of value because it is borrowed");
748 err.span_label(binding_span, format!("value borrowed, by `{}`, here", name));
749 for (span, name) in conflicts_move {
750 err.span_label(span, format!("value moved into `{}` here", name));
756 #[derive(Clone, Copy, Debug)]
765 fn let_source(tcx: TyCtxt<'_>, pat_id: HirId) -> LetSource {
768 let parent = hir.get_parent_node(pat_id);
769 let parent_node = hir.get(parent);
772 hir::Node::Arm(hir::Arm {
773 guard: Some(hir::Guard::IfLet(&hir::Pat { hir_id, .. }, _)),
775 }) if hir_id == pat_id => {
776 return LetSource::IfLetGuard;
778 hir::Node::Expr(hir::Expr { kind: hir::ExprKind::Let(..), span, .. }) => {
779 let expn_data = span.ctxt().outer_expn_data();
780 if let ExpnKind::Desugaring(DesugaringKind::LetElse) = expn_data.kind {
781 return LetSource::LetElse(expn_data.call_site);
787 let parent_parent = hir.get_parent_node(parent);
788 let parent_parent_node = hir.get(parent_parent);
790 let parent_parent_parent = hir.get_parent_node(parent_parent);
791 let parent_parent_parent_parent = hir.get_parent_node(parent_parent_parent);
792 let parent_parent_parent_parent_node = hir.get(parent_parent_parent_parent);
794 if let hir::Node::Expr(hir::Expr {
795 kind: hir::ExprKind::Loop(_, _, hir::LoopSource::While, _),
797 }) = parent_parent_parent_parent_node
799 return LetSource::WhileLet;
802 if let hir::Node::Expr(hir::Expr { kind: hir::ExprKind::If(..), .. }) = parent_parent_node {
803 return LetSource::IfLet;
806 LetSource::GenericLet
809 // Since this function is called within a let context, it is reasonable to assume that any parent
810 // `&&` infers a let chain
811 fn is_let_chain(tcx: TyCtxt<'_>, pat_id: HirId) -> bool {
813 let parent = hir.get_parent_node(pat_id);
814 let parent_parent = hir.get_parent_node(parent);
816 hir.get(parent_parent),
819 kind: hir::ExprKind::Binary(Spanned { node: hir::BinOpKind::And, .. }, ..),