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;
9 use rustc_errors::{error_code, struct_span_err, Applicability, DiagnosticBuilder};
11 use rustc_hir::def::*;
12 use rustc_hir::def_id::DefId;
13 use rustc_hir::intravisit::{self, Visitor};
14 use rustc_hir::{HirId, Pat};
15 use rustc_middle::ty::{self, AdtDef, Ty, TyCtxt};
16 use rustc_session::lint::builtin::{
17 BINDINGS_WITH_VARIANT_NAME, IRREFUTABLE_LET_PATTERNS, UNREACHABLE_PATTERNS,
19 use rustc_session::Session;
20 use rustc_span::source_map::Spanned;
21 use rustc_span::{DesugaringKind, ExpnKind, Span};
23 crate fn check_match(tcx: TyCtxt<'_>, def_id: DefId) {
24 let body_id = match def_id.as_local() {
26 Some(id) => tcx.hir().body_owned_by(tcx.hir().local_def_id_to_hir_id(id)),
29 let pattern_arena = TypedArena::default();
30 let mut visitor = MatchVisitor {
32 typeck_results: tcx.typeck_body(body_id),
33 param_env: tcx.param_env(def_id),
34 pattern_arena: &pattern_arena,
36 visitor.visit_body(tcx.hir().body(body_id));
39 fn create_e0004(sess: &Session, sp: Span, error_message: String) -> DiagnosticBuilder<'_> {
40 struct_span_err!(sess, sp, E0004, "{}", &error_message)
50 struct MatchVisitor<'a, 'p, 'tcx> {
52 typeck_results: &'a ty::TypeckResults<'tcx>,
53 param_env: ty::ParamEnv<'tcx>,
54 pattern_arena: &'p TypedArena<DeconstructedPat<'p, 'tcx>>,
57 impl<'tcx> Visitor<'tcx> for MatchVisitor<'_, '_, 'tcx> {
58 fn visit_expr(&mut self, ex: &'tcx hir::Expr<'tcx>) {
59 intravisit::walk_expr(self, ex);
61 hir::ExprKind::Match(scrut, arms, source) => self.check_match(scrut, arms, *source),
62 hir::ExprKind::Let(hir::Let { pat, init, span, .. }) => {
63 self.check_let(pat, init, *span)
69 fn visit_local(&mut self, loc: &'tcx hir::Local<'tcx>) {
70 intravisit::walk_local(self, loc);
72 let (msg, sp) = match loc.source {
73 hir::LocalSource::Normal => ("local binding", Some(loc.span)),
74 hir::LocalSource::AsyncFn => ("async fn binding", None),
75 hir::LocalSource::AwaitDesugar => ("`await` future binding", None),
76 hir::LocalSource::AssignDesugar(_) => ("destructuring assignment binding", None),
78 self.check_irrefutable(&loc.pat, msg, sp);
81 fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) {
82 intravisit::walk_param(self, param);
83 self.check_irrefutable(¶m.pat, "function argument", None);
87 impl PatCtxt<'_, '_> {
88 fn report_inlining_errors(&self) {
89 for error in &self.errors {
91 PatternError::StaticInPattern(span) => {
92 self.span_e0158(span, "statics cannot be referenced in patterns")
94 PatternError::AssocConstInPattern(span) => {
95 self.span_e0158(span, "associated consts cannot be referenced in patterns")
97 PatternError::ConstParamInPattern(span) => {
98 self.span_e0158(span, "const parameters cannot be referenced in patterns")
100 PatternError::NonConstPath(span) => {
101 rustc_middle::mir::interpret::struct_error(
103 "runtime values cannot be referenced in patterns",
111 fn span_e0158(&self, span: Span, text: &str) {
112 struct_span_err!(self.tcx.sess, span, E0158, "{}", text).emit();
116 impl<'p, 'tcx> MatchVisitor<'_, 'p, 'tcx> {
117 fn check_patterns(&self, pat: &Pat<'_>, rf: RefutableFlag) {
118 pat.walk_always(|pat| check_borrow_conflicts_in_at_patterns(self, pat));
119 check_for_bindings_named_same_as_variants(self, pat, rf);
124 cx: &mut MatchCheckCtxt<'p, 'tcx>,
125 pat: &'tcx hir::Pat<'tcx>,
126 have_errors: &mut bool,
127 ) -> &'p DeconstructedPat<'p, 'tcx> {
128 let mut patcx = PatCtxt::new(self.tcx, self.param_env, self.typeck_results);
129 patcx.include_lint_checks();
130 let pattern = patcx.lower_pattern(pat);
131 let pattern: &_ = cx.pattern_arena.alloc(DeconstructedPat::from_pat(cx, &pattern));
132 if !patcx.errors.is_empty() {
134 patcx.report_inlining_errors();
139 fn new_cx(&self, hir_id: HirId) -> MatchCheckCtxt<'p, 'tcx> {
142 param_env: self.param_env,
143 module: self.tcx.parent_module(hir_id).to_def_id(),
144 pattern_arena: &self.pattern_arena,
148 fn check_let(&mut self, pat: &'tcx hir::Pat<'tcx>, scrutinee: &hir::Expr<'_>, span: Span) {
149 self.check_patterns(pat, Refutable);
150 let mut cx = self.new_cx(scrutinee.hir_id);
151 let tpat = self.lower_pattern(&mut cx, pat, &mut false);
152 check_let_reachability(&mut cx, pat.hir_id, tpat, span);
157 scrut: &hir::Expr<'_>,
158 hir_arms: &'tcx [hir::Arm<'tcx>],
159 source: hir::MatchSource,
161 let mut cx = self.new_cx(scrut.hir_id);
163 for arm in hir_arms {
164 // Check the arm for some things unrelated to exhaustiveness.
165 self.check_patterns(&arm.pat, Refutable);
166 if let Some(hir::Guard::IfLet(ref pat, _)) = arm.guard {
167 self.check_patterns(pat, Refutable);
168 let tpat = self.lower_pattern(&mut cx, pat, &mut false);
169 check_let_reachability(&mut cx, pat.hir_id, tpat, tpat.span());
173 let mut have_errors = false;
175 let arms: Vec<_> = hir_arms
177 .map(|hir::Arm { pat, guard, .. }| MatchArm {
178 pat: self.lower_pattern(&mut cx, pat, &mut have_errors),
180 has_guard: guard.is_some(),
184 // Bail out early if lowering failed.
189 let scrut_ty = self.typeck_results.expr_ty_adjusted(scrut);
190 let report = compute_match_usefulness(&cx, &arms, scrut.hir_id, scrut_ty);
193 // Don't report arm reachability of desugared `match $iter.into_iter() { iter => .. }`
194 // when the iterator is an uninhabited type. unreachable_code will trigger instead.
195 hir::MatchSource::ForLoopDesugar if arms.len() == 1 => {}
196 hir::MatchSource::ForLoopDesugar | hir::MatchSource::Normal => {
197 report_arm_reachability(&cx, &report)
199 // Unreachable patterns in try and await expressions occur when one of
200 // the arms are an uninhabited type. Which is OK.
201 hir::MatchSource::AwaitDesugar | hir::MatchSource::TryDesugar => {}
204 // Check if the match is exhaustive.
205 let is_empty_match = arms.is_empty();
206 let witnesses = report.non_exhaustiveness_witnesses;
207 if !witnesses.is_empty() {
208 if source == hir::MatchSource::ForLoopDesugar && hir_arms.len() == 2 {
209 // the for loop pattern is not irrefutable
210 let pat = hir_arms[1].pat.for_loop_some().unwrap();
211 self.check_irrefutable(pat, "`for` loop binding", None);
213 non_exhaustive_match(&cx, scrut_ty, scrut.span, witnesses, is_empty_match);
218 fn check_irrefutable(&self, pat: &'tcx Pat<'tcx>, origin: &str, sp: Option<Span>) {
219 let mut cx = self.new_cx(pat.hir_id);
221 let pattern = self.lower_pattern(&mut cx, pat, &mut false);
222 let pattern_ty = pattern.ty();
223 let arms = vec![MatchArm { pat: pattern, hir_id: pat.hir_id, has_guard: false }];
224 let report = compute_match_usefulness(&cx, &arms, pat.hir_id, pattern_ty);
226 // Note: we ignore whether the pattern is unreachable (i.e. whether the type is empty). We
227 // only care about exhaustiveness here.
228 let witnesses = report.non_exhaustiveness_witnesses;
229 if witnesses.is_empty() {
230 // The pattern is irrefutable.
231 self.check_patterns(pat, Irrefutable);
235 let joined_patterns = joined_uncovered_patterns(&cx, &witnesses);
236 let mut err = struct_span_err!(
240 "refutable pattern in {}: {} not covered",
244 let suggest_if_let = match &pat.kind {
245 hir::PatKind::Path(hir::QPath::Resolved(None, path))
246 if path.segments.len() == 1 && path.segments[0].args.is_none() =>
248 const_not_var(&mut err, cx.tcx, pat, path);
252 err.span_label(pat.span, pattern_not_covered_label(&witnesses, &joined_patterns));
257 if let (Some(span), true) = (sp, suggest_if_let) {
259 "`let` bindings require an \"irrefutable pattern\", like a `struct` or \
260 an `enum` with only one variant",
262 if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) {
265 "you might want to use `if let` to ignore the variant that isn't matched",
266 format!("if {} {{ /* */ }}", &snippet[..snippet.len() - 1]),
267 Applicability::HasPlaceholders,
271 "for more information, visit \
272 https://doc.rust-lang.org/book/ch18-02-refutability.html",
276 adt_defined_here(&cx, &mut err, pattern_ty, &witnesses);
277 err.note(&format!("the matched value is of type `{}`", pattern_ty));
282 /// A path pattern was interpreted as a constant, not a new variable.
283 /// This caused an irrefutable match failure in e.g. `let`.
285 err: &mut DiagnosticBuilder<'_>,
288 path: &hir::Path<'_>,
290 let descr = path.res.descr();
293 format!("interpreted as {} {} pattern, not a new variable", path.res.article(), descr,),
298 "introduce a variable instead",
299 format!("{}_var", path.segments[0].ident).to_lowercase(),
300 // Cannot use `MachineApplicable` as it's not really *always* correct
301 // because there may be such an identifier in scope or the user maybe
302 // really wanted to match against the constant. This is quite unlikely however.
303 Applicability::MaybeIncorrect,
306 if let Some(span) = tcx.hir().res_span(path.res) {
307 err.span_label(span, format!("{} defined here", descr));
311 fn check_for_bindings_named_same_as_variants(
312 cx: &MatchVisitor<'_, '_, '_>,
316 pat.walk_always(|p| {
317 if let hir::PatKind::Binding(_, _, ident, None) = p.kind {
318 if let Some(ty::BindByValue(hir::Mutability::Not)) =
319 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 if 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,
362 /// Checks for common cases of "catchall" patterns that may not be intended as such.
363 fn pat_is_catchall(pat: &DeconstructedPat<'_, '_>) -> bool {
367 Single => pat.iter_fields().all(|pat| pat_is_catchall(pat)),
372 fn unreachable_pattern(tcx: TyCtxt<'_>, span: Span, id: HirId, catchall: Option<Span>) {
373 tcx.struct_span_lint_hir(UNREACHABLE_PATTERNS, id, span, |lint| {
374 let mut err = lint.build("unreachable pattern");
375 if let Some(catchall) = catchall {
376 // We had a catchall pattern, hint at that.
377 err.span_label(span, "unreachable pattern");
378 err.span_label(catchall, "matches any value");
384 fn irrefutable_let_pattern(tcx: TyCtxt<'_>, id: HirId, span: Span) {
385 macro_rules! emit_diag {
392 let mut diag = $lint.build(concat!("irrefutable ", $source_name, " pattern"));
393 diag.note(concat!("this pattern will always match, so the ", $note_sufix));
394 diag.help(concat!("consider ", $help_sufix));
399 let source = let_source(tcx, id);
400 let span = match source {
401 LetSource::LetElse(span) => span,
404 tcx.struct_span_lint_hir(IRREFUTABLE_LET_PATTERNS, id, span, |lint| match source {
405 LetSource::GenericLet => {
406 emit_diag!(lint, "`let`", "`let` is useless", "removing `let`");
408 LetSource::IfLet => {
412 "`if let` is useless",
413 "replacing the `if let` with a `let`"
416 LetSource::IfLetGuard => {
421 "removing the guard and adding a `let` inside the match arm"
424 LetSource::LetElse(..) => {
428 "`else` clause is useless",
429 "removing the `else` clause"
432 LetSource::WhileLet => {
436 "loop will never exit",
437 "instead using a `loop { ... }` with a `let` inside it"
443 fn check_let_reachability<'p, 'tcx>(
444 cx: &mut MatchCheckCtxt<'p, 'tcx>,
446 pat: &'p DeconstructedPat<'p, 'tcx>,
449 if is_let_chain(cx.tcx, pat_id) {
453 let arms = [MatchArm { pat, hir_id: pat_id, has_guard: false }];
454 let report = compute_match_usefulness(&cx, &arms, pat_id, pat.ty());
456 // Report if the pattern is unreachable, which can only occur when the type is uninhabited.
457 // This also reports unreachable sub-patterns though, so we can't just replace it with an
458 // `is_uninhabited` check.
459 report_arm_reachability(&cx, &report);
461 if report.non_exhaustiveness_witnesses.is_empty() {
462 // The match is exhaustive, i.e. the `if let` pattern is irrefutable.
463 irrefutable_let_pattern(cx.tcx, pat_id, span);
467 /// Report unreachable arms, if any.
468 fn report_arm_reachability<'p, 'tcx>(
469 cx: &MatchCheckCtxt<'p, 'tcx>,
470 report: &UsefulnessReport<'p, 'tcx>,
473 let mut catchall = None;
474 for (arm, is_useful) in report.arm_usefulness.iter() {
476 Unreachable => unreachable_pattern(cx.tcx, arm.pat.span(), arm.hir_id, catchall),
477 Reachable(unreachables) if unreachables.is_empty() => {}
478 // The arm is reachable, but contains unreachable subpatterns (from or-patterns).
479 Reachable(unreachables) => {
480 let mut unreachables = unreachables.clone();
481 // Emit lints in the order in which they occur in the file.
482 unreachables.sort_unstable();
483 for span in unreachables {
484 unreachable_pattern(cx.tcx, span, arm.hir_id, None);
488 if !arm.has_guard && catchall.is_none() && pat_is_catchall(arm.pat) {
489 catchall = Some(arm.pat.span());
494 /// Report that a match is not exhaustive.
495 fn non_exhaustive_match<'p, 'tcx>(
496 cx: &MatchCheckCtxt<'p, 'tcx>,
499 witnesses: Vec<DeconstructedPat<'p, 'tcx>>,
500 is_empty_match: bool,
502 let non_empty_enum = match scrut_ty.kind() {
503 ty::Adt(def, _) => def.is_enum() && !def.variants.is_empty(),
506 // In the case of an empty match, replace the '`_` not covered' diagnostic with something more
509 if is_empty_match && !non_empty_enum {
513 format!("non-exhaustive patterns: type `{}` is non-empty", scrut_ty),
516 let joined_patterns = joined_uncovered_patterns(cx, &witnesses);
520 format!("non-exhaustive patterns: {} not covered", joined_patterns),
522 err.span_label(sp, pattern_not_covered_label(&witnesses, &joined_patterns));
525 let is_variant_list_non_exhaustive = match scrut_ty.kind() {
526 ty::Adt(def, _) if def.is_variant_list_non_exhaustive() && !def.did.is_local() => true,
530 adt_defined_here(cx, &mut err, scrut_ty, &witnesses);
532 "ensure that all possible cases are being handled, \
533 possibly by adding wildcards or more match arms",
536 "the matched value is of type `{}`{}",
538 if is_variant_list_non_exhaustive { ", which is marked as non-exhaustive" } else { "" }
540 if (scrut_ty == cx.tcx.types.usize || scrut_ty == cx.tcx.types.isize)
542 && witnesses.len() == 1
543 && matches!(witnesses[0].ctor(), Constructor::NonExhaustive)
546 "`{}` does not have a fixed maximum value, \
547 so a wildcard `_` is necessary to match exhaustively",
550 if cx.tcx.sess.is_nightly_build() {
552 "add `#![feature(precise_pointer_size_matching)]` \
553 to the crate attributes to enable precise `{}` matching",
558 if let ty::Ref(_, sub_ty, _) = scrut_ty.kind() {
559 if cx.tcx.is_ty_uninhabited_from(cx.module, sub_ty, cx.param_env) {
560 err.note("references are always considered inhabited");
566 crate fn joined_uncovered_patterns<'p, 'tcx>(
567 cx: &MatchCheckCtxt<'p, 'tcx>,
568 witnesses: &[DeconstructedPat<'p, 'tcx>],
570 const LIMIT: usize = 3;
571 let pat_to_str = |pat: &DeconstructedPat<'p, 'tcx>| pat.to_pat(cx).to_string();
574 [witness] => format!("`{}`", witness.to_pat(cx)),
575 [head @ .., tail] if head.len() < LIMIT => {
576 let head: Vec<_> = head.iter().map(pat_to_str).collect();
577 format!("`{}` and `{}`", head.join("`, `"), tail.to_pat(cx))
580 let (head, tail) = witnesses.split_at(LIMIT);
581 let head: Vec<_> = head.iter().map(pat_to_str).collect();
582 format!("`{}` and {} more", head.join("`, `"), tail.len())
587 crate fn pattern_not_covered_label(
588 witnesses: &[DeconstructedPat<'_, '_>],
589 joined_patterns: &str,
591 format!("pattern{} {} not covered", rustc_errors::pluralize!(witnesses.len()), joined_patterns)
594 /// Point at the definition of non-covered `enum` variants.
595 fn adt_defined_here<'p, 'tcx>(
596 cx: &MatchCheckCtxt<'p, 'tcx>,
597 err: &mut DiagnosticBuilder<'_>,
599 witnesses: &[DeconstructedPat<'p, 'tcx>],
601 let ty = ty.peel_refs();
602 if let ty::Adt(def, _) = ty.kind() {
603 if let Some(sp) = cx.tcx.hir().span_if_local(def.did) {
604 err.span_label(sp, format!("`{}` defined here", ty));
607 if witnesses.len() < 4 {
608 for sp in maybe_point_at_variant(cx, def, witnesses.iter()) {
609 err.span_label(sp, "not covered");
615 fn maybe_point_at_variant<'a, 'p: 'a, 'tcx: 'a>(
616 cx: &MatchCheckCtxt<'p, 'tcx>,
618 patterns: impl Iterator<Item = &'a DeconstructedPat<'p, 'tcx>>,
621 let mut covered = vec![];
622 for pattern in patterns {
623 if let Variant(variant_index) = pattern.ctor() {
624 if let ty::Adt(this_def, _) = pattern.ty().kind() {
625 if this_def.did != def.did {
629 let sp = def.variants[*variant_index].ident(cx.tcx).span;
630 if covered.contains(&sp) {
631 // Don't point at variants that have already been covered due to other patterns to avoid
637 covered.extend(maybe_point_at_variant(cx, def, pattern.iter_fields()));
642 /// Check if a by-value binding is by-value. That is, check if the binding's type is not `Copy`.
643 fn is_binding_by_move(cx: &MatchVisitor<'_, '_, '_>, hir_id: HirId, span: Span) -> bool {
644 !cx.typeck_results.node_type(hir_id).is_copy_modulo_regions(cx.tcx.at(span), cx.param_env)
647 /// Check that there are no borrow or move conflicts in `binding @ subpat` patterns.
649 /// For example, this would reject:
650 /// - `ref x @ Some(ref mut y)`,
651 /// - `ref mut x @ Some(ref y)`,
652 /// - `ref mut x @ Some(ref mut y)`,
653 /// - `ref mut? x @ Some(y)`, and
654 /// - `x @ Some(ref mut? y)`.
656 /// This analysis is *not* subsumed by NLL.
657 fn check_borrow_conflicts_in_at_patterns(cx: &MatchVisitor<'_, '_, '_>, pat: &Pat<'_>) {
658 // Extract `sub` in `binding @ sub`.
659 let (name, sub) = match &pat.kind {
660 hir::PatKind::Binding(.., name, Some(sub)) => (*name, sub),
663 let binding_span = pat.span.with_hi(name.span.hi());
665 let typeck_results = cx.typeck_results;
666 let sess = cx.tcx.sess;
668 // Get the binding move, extract the mutability if by-ref.
669 let mut_outer = match typeck_results.extract_binding_mode(sess, pat.hir_id, pat.span) {
670 Some(ty::BindByValue(_)) if is_binding_by_move(cx, pat.hir_id, pat.span) => {
671 // We have `x @ pat` where `x` is by-move. Reject all borrows in `pat`.
672 let mut conflicts_ref = Vec::new();
673 sub.each_binding(|_, hir_id, span, _| {
674 match typeck_results.extract_binding_mode(sess, hir_id, span) {
675 Some(ty::BindByValue(_)) | None => {}
676 Some(ty::BindByReference(_)) => conflicts_ref.push(span),
679 if !conflicts_ref.is_empty() {
680 let occurs_because = format!(
681 "move occurs because `{}` has type `{}` which does not implement the `Copy` trait",
683 typeck_results.node_type(pat.hir_id),
685 sess.struct_span_err(pat.span, "borrow of moved value")
686 .span_label(binding_span, format!("value moved into `{}` here", name))
687 .span_label(binding_span, occurs_because)
688 .span_labels(conflicts_ref, "value borrowed here after move")
693 Some(ty::BindByValue(_)) | None => return,
694 Some(ty::BindByReference(m)) => m,
697 // We now have `ref $mut_outer binding @ sub` (semantically).
698 // Recurse into each binding in `sub` and find mutability or move conflicts.
699 let mut conflicts_move = Vec::new();
700 let mut conflicts_mut_mut = Vec::new();
701 let mut conflicts_mut_ref = Vec::new();
702 sub.each_binding(|_, hir_id, span, name| {
703 match typeck_results.extract_binding_mode(sess, hir_id, span) {
704 Some(ty::BindByReference(mut_inner)) => match (mut_outer, mut_inner) {
705 (Mutability::Not, Mutability::Not) => {} // Both sides are `ref`.
706 (Mutability::Mut, Mutability::Mut) => conflicts_mut_mut.push((span, name)), // 2x `ref mut`.
707 _ => conflicts_mut_ref.push((span, name)), // `ref` + `ref mut` in either direction.
709 Some(ty::BindByValue(_)) if is_binding_by_move(cx, hir_id, span) => {
710 conflicts_move.push((span, name)) // `ref mut?` + by-move conflict.
712 Some(ty::BindByValue(_)) | None => {} // `ref mut?` + by-copy is fine.
716 // Report errors if any.
717 if !conflicts_mut_mut.is_empty() {
718 // Report mutability conflicts for e.g. `ref mut x @ Some(ref mut y)`.
720 .struct_span_err(pat.span, "cannot borrow value as mutable more than once at a time");
721 err.span_label(binding_span, format!("first mutable borrow, by `{}`, occurs here", name));
722 for (span, name) in conflicts_mut_mut {
723 err.span_label(span, format!("another mutable borrow, by `{}`, occurs here", name));
725 for (span, name) in conflicts_mut_ref {
726 err.span_label(span, format!("also borrowed as immutable, by `{}`, here", name));
728 for (span, name) in conflicts_move {
729 err.span_label(span, format!("also moved into `{}` here", name));
732 } else if !conflicts_mut_ref.is_empty() {
733 // Report mutability conflicts for e.g. `ref x @ Some(ref mut y)` or the converse.
734 let (primary, also) = match mut_outer {
735 Mutability::Mut => ("mutable", "immutable"),
736 Mutability::Not => ("immutable", "mutable"),
739 format!("cannot borrow value as {} because it is also borrowed as {}", also, primary);
740 let mut err = sess.struct_span_err(pat.span, &msg);
741 err.span_label(binding_span, format!("{} borrow, by `{}`, occurs here", primary, name));
742 for (span, name) in conflicts_mut_ref {
743 err.span_label(span, format!("{} borrow, by `{}`, occurs here", also, name));
745 for (span, name) in conflicts_move {
746 err.span_label(span, format!("also moved into `{}` here", name));
749 } else if !conflicts_move.is_empty() {
750 // Report by-ref and by-move conflicts, e.g. `ref x @ y`.
752 sess.struct_span_err(pat.span, "cannot move out of value because it is borrowed");
753 err.span_label(binding_span, format!("value borrowed, by `{}`, here", name));
754 for (span, name) in conflicts_move {
755 err.span_label(span, format!("value moved into `{}` here", name));
761 #[derive(Clone, Copy, Debug)]
770 fn let_source(tcx: TyCtxt<'_>, pat_id: HirId) -> LetSource {
773 let parent = hir.get_parent_node(pat_id);
774 let parent_node = hir.get(parent);
777 hir::Node::Arm(hir::Arm {
778 guard: Some(hir::Guard::IfLet(&hir::Pat { hir_id, .. }, _)),
780 }) if hir_id == pat_id => {
781 return LetSource::IfLetGuard;
783 hir::Node::Expr(hir::Expr { kind: hir::ExprKind::Let(..), span, .. }) => {
784 let expn_data = span.ctxt().outer_expn_data();
785 if let ExpnKind::Desugaring(DesugaringKind::LetElse) = expn_data.kind {
786 return LetSource::LetElse(expn_data.call_site);
792 let parent_parent = hir.get_parent_node(parent);
793 let parent_parent_node = hir.get(parent_parent);
795 let parent_parent_parent = hir.get_parent_node(parent_parent);
796 let parent_parent_parent_parent = hir.get_parent_node(parent_parent_parent);
797 let parent_parent_parent_parent_node = hir.get(parent_parent_parent_parent);
799 if let hir::Node::Expr(hir::Expr {
800 kind: hir::ExprKind::Loop(_, _, hir::LoopSource::While, _),
802 }) = parent_parent_parent_parent_node
804 return LetSource::WhileLet;
807 if let hir::Node::Expr(hir::Expr { kind: hir::ExprKind::If(..), .. }) = parent_parent_node {
808 return LetSource::IfLet;
811 LetSource::GenericLet
814 // Since this function is called within a let context, it is reasonable to assume that any parent
815 // `&&` infers a let chain
816 fn is_let_chain(tcx: TyCtxt<'_>, pat_id: HirId) -> bool {
818 let parent = hir.get_parent_node(pat_id);
819 let parent_parent = hir.get_parent_node(parent);
821 hir.get(parent_parent),
824 kind: hir::ExprKind::Binary(Spanned { node: hir::BinOpKind::And, .. }, ..),