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, MultiSpan, 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) => {
68 self.check_match(scrut, arms, *source, ex.span)
70 hir::ExprKind::Let(hir::Let { pat, init, span, .. }) => {
71 self.check_let(pat, init, *span)
77 fn visit_local(&mut self, loc: &'tcx hir::Local<'tcx>) {
78 intravisit::walk_local(self, loc);
80 let (msg, sp) = match loc.source {
81 hir::LocalSource::Normal => ("local binding", Some(loc.span)),
82 hir::LocalSource::AsyncFn => ("async fn binding", None),
83 hir::LocalSource::AwaitDesugar => ("`await` future binding", None),
84 hir::LocalSource::AssignDesugar(_) => ("destructuring assignment binding", None),
86 self.check_irrefutable(&loc.pat, msg, sp);
89 fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) {
90 intravisit::walk_param(self, param);
91 self.check_irrefutable(¶m.pat, "function argument", None);
95 impl PatCtxt<'_, '_> {
96 fn report_inlining_errors(&self) {
97 for error in &self.errors {
99 PatternError::StaticInPattern(span) => {
100 self.span_e0158(span, "statics cannot be referenced in patterns")
102 PatternError::AssocConstInPattern(span) => {
103 self.span_e0158(span, "associated consts cannot be referenced in patterns")
105 PatternError::ConstParamInPattern(span) => {
106 self.span_e0158(span, "const parameters cannot be referenced in patterns")
108 PatternError::NonConstPath(span) => {
109 rustc_middle::mir::interpret::struct_error(
111 "runtime values cannot be referenced in patterns",
119 fn span_e0158(&self, span: Span, text: &str) {
120 struct_span_err!(self.tcx.sess, span, E0158, "{}", text).emit();
124 impl<'p, 'tcx> MatchVisitor<'_, 'p, 'tcx> {
125 fn check_patterns(&self, pat: &Pat<'_>, rf: RefutableFlag) {
126 pat.walk_always(|pat| check_borrow_conflicts_in_at_patterns(self, pat));
127 check_for_bindings_named_same_as_variants(self, pat, rf);
132 cx: &mut MatchCheckCtxt<'p, 'tcx>,
133 pat: &'tcx hir::Pat<'tcx>,
134 have_errors: &mut bool,
135 ) -> &'p DeconstructedPat<'p, 'tcx> {
136 let mut patcx = PatCtxt::new(self.tcx, self.param_env, self.typeck_results);
137 patcx.include_lint_checks();
138 let pattern = patcx.lower_pattern(pat);
139 let pattern: &_ = cx.pattern_arena.alloc(DeconstructedPat::from_pat(cx, &pattern));
140 if !patcx.errors.is_empty() {
142 patcx.report_inlining_errors();
147 fn new_cx(&self, hir_id: HirId) -> MatchCheckCtxt<'p, 'tcx> {
150 param_env: self.param_env,
151 module: self.tcx.parent_module(hir_id).to_def_id(),
152 pattern_arena: &self.pattern_arena,
156 fn check_let(&mut self, pat: &'tcx hir::Pat<'tcx>, scrutinee: &hir::Expr<'_>, span: Span) {
157 self.check_patterns(pat, Refutable);
158 let mut cx = self.new_cx(scrutinee.hir_id);
159 let tpat = self.lower_pattern(&mut cx, pat, &mut false);
160 check_let_reachability(&mut cx, pat.hir_id, tpat, span);
165 scrut: &hir::Expr<'_>,
166 hir_arms: &'tcx [hir::Arm<'tcx>],
167 source: hir::MatchSource,
170 let mut cx = self.new_cx(scrut.hir_id);
172 for arm in hir_arms {
173 // Check the arm for some things unrelated to exhaustiveness.
174 self.check_patterns(&arm.pat, Refutable);
175 if let Some(hir::Guard::IfLet(ref pat, _)) = arm.guard {
176 self.check_patterns(pat, Refutable);
177 let tpat = self.lower_pattern(&mut cx, pat, &mut false);
178 check_let_reachability(&mut cx, pat.hir_id, tpat, tpat.span());
182 let mut have_errors = false;
184 let arms: Vec<_> = hir_arms
186 .map(|hir::Arm { pat, guard, .. }| MatchArm {
187 pat: self.lower_pattern(&mut cx, pat, &mut have_errors),
189 has_guard: guard.is_some(),
193 // Bail out early if lowering failed.
198 let scrut_ty = self.typeck_results.expr_ty_adjusted(scrut);
199 let report = compute_match_usefulness(&cx, &arms, scrut.hir_id, scrut_ty);
202 // Don't report arm reachability of desugared `match $iter.into_iter() { iter => .. }`
203 // when the iterator is an uninhabited type. unreachable_code will trigger instead.
204 hir::MatchSource::ForLoopDesugar if arms.len() == 1 => {}
205 hir::MatchSource::ForLoopDesugar | hir::MatchSource::Normal => {
206 report_arm_reachability(&cx, &report)
208 // Unreachable patterns in try and await expressions occur when one of
209 // the arms are an uninhabited type. Which is OK.
210 hir::MatchSource::AwaitDesugar | hir::MatchSource::TryDesugar => {}
213 // Check if the match is exhaustive.
214 let witnesses = report.non_exhaustiveness_witnesses;
215 if !witnesses.is_empty() {
216 if source == hir::MatchSource::ForLoopDesugar && hir_arms.len() == 2 {
217 // the for loop pattern is not irrefutable
218 let pat = hir_arms[1].pat.for_loop_some().unwrap();
219 self.check_irrefutable(pat, "`for` loop binding", None);
221 non_exhaustive_match(&cx, scrut_ty, scrut.span, witnesses, hir_arms, expr_span);
226 fn check_irrefutable(&self, pat: &'tcx Pat<'tcx>, origin: &str, sp: Option<Span>) {
227 let mut cx = self.new_cx(pat.hir_id);
229 let pattern = self.lower_pattern(&mut cx, pat, &mut false);
230 let pattern_ty = pattern.ty();
231 let arms = vec![MatchArm { pat: pattern, hir_id: pat.hir_id, has_guard: false }];
232 let report = compute_match_usefulness(&cx, &arms, pat.hir_id, pattern_ty);
234 // Note: we ignore whether the pattern is unreachable (i.e. whether the type is empty). We
235 // only care about exhaustiveness here.
236 let witnesses = report.non_exhaustiveness_witnesses;
237 if witnesses.is_empty() {
238 // The pattern is irrefutable.
239 self.check_patterns(pat, Irrefutable);
243 let joined_patterns = joined_uncovered_patterns(&cx, &witnesses);
244 let mut err = struct_span_err!(
248 "refutable pattern in {}: {} not covered",
252 let suggest_if_let = match &pat.kind {
253 hir::PatKind::Path(hir::QPath::Resolved(None, path))
254 if path.segments.len() == 1 && path.segments[0].args.is_none() =>
256 const_not_var(&mut err, cx.tcx, pat, path);
260 err.span_label(pat.span, pattern_not_covered_label(&witnesses, &joined_patterns));
265 if let (Some(span), true) = (sp, suggest_if_let) {
267 "`let` bindings require an \"irrefutable pattern\", like a `struct` or \
268 an `enum` with only one variant",
270 if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) {
273 "you might want to use `if let` to ignore the variant that isn't matched",
274 format!("if {} {{ /* */ }}", &snippet[..snippet.len() - 1]),
275 Applicability::HasPlaceholders,
279 "for more information, visit \
280 https://doc.rust-lang.org/book/ch18-02-refutability.html",
284 adt_defined_here(&cx, &mut err, pattern_ty, &witnesses);
285 err.note(&format!("the matched value is of type `{}`", pattern_ty));
290 /// A path pattern was interpreted as a constant, not a new variable.
291 /// This caused an irrefutable match failure in e.g. `let`.
292 fn const_not_var(err: &mut Diagnostic, tcx: TyCtxt<'_>, pat: &Pat<'_>, path: &hir::Path<'_>) {
293 let descr = path.res.descr();
296 format!("interpreted as {} {} pattern, not a new variable", path.res.article(), descr,),
301 "introduce a variable instead",
302 format!("{}_var", path.segments[0].ident).to_lowercase(),
303 // Cannot use `MachineApplicable` as it's not really *always* correct
304 // because there may be such an identifier in scope or the user maybe
305 // really wanted to match against the constant. This is quite unlikely however.
306 Applicability::MaybeIncorrect,
309 if let Some(span) = tcx.hir().res_span(path.res) {
310 err.span_label(span, format!("{} defined here", descr));
314 fn check_for_bindings_named_same_as_variants(
315 cx: &MatchVisitor<'_, '_, '_>,
319 pat.walk_always(|p| {
320 if let hir::PatKind::Binding(_, _, ident, None) = p.kind
321 && let Some(ty::BindByValue(hir::Mutability::Not)) =
322 cx.typeck_results.extract_binding_mode(cx.tcx.sess, p.hir_id, p.span)
323 && let pat_ty = cx.typeck_results.pat_ty(p).peel_refs()
324 && let ty::Adt(edef, _) = pat_ty.kind()
326 && edef.variants.iter().any(|variant| {
327 variant.ident(cx.tcx) == ident && variant.ctor_kind == CtorKind::Const
330 let variant_count = edef.variants.len();
331 cx.tcx.struct_span_lint_hir(
332 BINDINGS_WITH_VARIANT_NAME,
336 let ty_path = cx.tcx.def_path_str(edef.did);
337 let mut err = lint.build(&format!(
338 "pattern binding `{}` is named the same as one \
339 of the variants of the type `{}`",
342 err.code(error_code!(E0170));
343 // If this is an irrefutable pattern, and there's > 1 variant,
344 // then we can't actually match on this. Applying the below
345 // suggestion would produce code that breaks on `check_irrefutable`.
346 if rf == Refutable || variant_count == 1 {
349 "to match on the variant, qualify the path",
350 format!("{}::{}", ty_path, ident),
351 Applicability::MachineApplicable,
361 /// Checks for common cases of "catchall" patterns that may not be intended as such.
362 fn pat_is_catchall(pat: &DeconstructedPat<'_, '_>) -> bool {
366 Single => pat.iter_fields().all(|pat| pat_is_catchall(pat)),
371 fn unreachable_pattern(tcx: TyCtxt<'_>, span: Span, id: HirId, catchall: Option<Span>) {
372 tcx.struct_span_lint_hir(UNREACHABLE_PATTERNS, id, span, |lint| {
373 let mut err = lint.build("unreachable pattern");
374 if let Some(catchall) = catchall {
375 // We had a catchall pattern, hint at that.
376 err.span_label(span, "unreachable pattern");
377 err.span_label(catchall, "matches any value");
383 fn irrefutable_let_pattern(tcx: TyCtxt<'_>, id: HirId, span: Span) {
384 macro_rules! emit_diag {
391 let mut diag = $lint.build(concat!("irrefutable ", $source_name, " pattern"));
392 diag.note(concat!("this pattern will always match, so the ", $note_sufix));
393 diag.help(concat!("consider ", $help_sufix));
398 let source = let_source(tcx, id);
399 let span = match source {
400 LetSource::LetElse(span) => span,
403 tcx.struct_span_lint_hir(IRREFUTABLE_LET_PATTERNS, id, span, |lint| match source {
404 LetSource::GenericLet => {
405 emit_diag!(lint, "`let`", "`let` is useless", "removing `let`");
407 LetSource::IfLet => {
411 "`if let` is useless",
412 "replacing the `if let` with a `let`"
415 LetSource::IfLetGuard => {
420 "removing the guard and adding a `let` inside the match arm"
423 LetSource::LetElse(..) => {
427 "`else` clause is useless",
428 "removing the `else` clause"
431 LetSource::WhileLet => {
435 "loop will never exit",
436 "instead using a `loop { ... }` with a `let` inside it"
442 fn check_let_reachability<'p, 'tcx>(
443 cx: &mut MatchCheckCtxt<'p, 'tcx>,
445 pat: &'p DeconstructedPat<'p, 'tcx>,
448 if is_let_chain(cx.tcx, pat_id) {
452 let arms = [MatchArm { pat, hir_id: pat_id, has_guard: false }];
453 let report = compute_match_usefulness(&cx, &arms, pat_id, pat.ty());
455 // Report if the pattern is unreachable, which can only occur when the type is uninhabited.
456 // This also reports unreachable sub-patterns though, so we can't just replace it with an
457 // `is_uninhabited` check.
458 report_arm_reachability(&cx, &report);
460 if report.non_exhaustiveness_witnesses.is_empty() {
461 // The match is exhaustive, i.e. the `if let` pattern is irrefutable.
462 irrefutable_let_pattern(cx.tcx, pat_id, span);
466 /// Report unreachable arms, if any.
467 fn report_arm_reachability<'p, 'tcx>(
468 cx: &MatchCheckCtxt<'p, 'tcx>,
469 report: &UsefulnessReport<'p, 'tcx>,
472 let mut catchall = None;
473 for (arm, is_useful) in report.arm_usefulness.iter() {
475 Unreachable => unreachable_pattern(cx.tcx, arm.pat.span(), arm.hir_id, catchall),
476 Reachable(unreachables) if unreachables.is_empty() => {}
477 // The arm is reachable, but contains unreachable subpatterns (from or-patterns).
478 Reachable(unreachables) => {
479 let mut unreachables = unreachables.clone();
480 // Emit lints in the order in which they occur in the file.
481 unreachables.sort_unstable();
482 for span in unreachables {
483 unreachable_pattern(cx.tcx, span, arm.hir_id, None);
487 if !arm.has_guard && catchall.is_none() && pat_is_catchall(arm.pat) {
488 catchall = Some(arm.pat.span());
493 /// Report that a match is not exhaustive.
494 fn non_exhaustive_match<'p, 'tcx>(
495 cx: &MatchCheckCtxt<'p, 'tcx>,
498 witnesses: Vec<DeconstructedPat<'p, 'tcx>>,
499 arms: &[hir::Arm<'tcx>],
502 let is_empty_match = arms.is_empty();
503 let non_empty_enum = match scrut_ty.kind() {
504 ty::Adt(def, _) => def.is_enum() && !def.variants.is_empty(),
507 // In the case of an empty match, replace the '`_` not covered' diagnostic with something more
511 let mut patterns_len = 0;
512 if is_empty_match && !non_empty_enum {
516 format!("non-exhaustive patterns: type `{}` is non-empty", scrut_ty),
518 pattern = "_".to_string();
520 let joined_patterns = joined_uncovered_patterns(cx, &witnesses);
524 format!("non-exhaustive patterns: {} not covered", joined_patterns),
526 err.span_label(sp, pattern_not_covered_label(&witnesses, &joined_patterns));
527 patterns_len = witnesses.len();
528 pattern = if witnesses.len() < 4 {
531 .map(|witness| witness.to_pat(cx).to_string())
532 .collect::<Vec<String>>()
539 let is_variant_list_non_exhaustive = match scrut_ty.kind() {
540 ty::Adt(def, _) if def.is_variant_list_non_exhaustive() && !def.did.is_local() => true,
544 adt_defined_here(cx, &mut err, scrut_ty, &witnesses);
546 "the matched value is of type `{}`{}",
548 if is_variant_list_non_exhaustive { ", which is marked as non-exhaustive" } else { "" }
550 if (scrut_ty == cx.tcx.types.usize || scrut_ty == cx.tcx.types.isize)
552 && witnesses.len() == 1
553 && matches!(witnesses[0].ctor(), Constructor::NonExhaustive)
556 "`{}` does not have a fixed maximum value, so a wildcard `_` is necessary to match \
560 if cx.tcx.sess.is_nightly_build() {
562 "add `#![feature(precise_pointer_size_matching)]` to the crate attributes to \
563 enable precise `{}` matching",
568 if let ty::Ref(_, sub_ty, _) = scrut_ty.kind() {
569 if cx.tcx.is_ty_uninhabited_from(cx.module, *sub_ty, cx.param_env) {
570 err.note("references are always considered inhabited");
574 let mut suggestion = None;
575 let sm = cx.tcx.sess.source_map();
577 [] if sp.ctxt() == expr_span.ctxt() => {
578 // Get the span for the empty match body `{}`.
579 let (indentation, more) = if let Some(snippet) = sm.indentation_before(sp) {
580 (format!("\n{}", snippet), " ")
582 (" ".to_string(), "")
585 sp.shrink_to_hi().with_hi(expr_span.hi()),
587 " {{{indentation}{more}{pattern} => todo!(),{indentation}}}",
588 indentation = indentation,
595 let pre_indentation = if let (Some(snippet), true) = (
596 sm.indentation_before(only.span),
597 sm.is_multiline(sp.shrink_to_hi().with_hi(only.span.lo())),
599 format!("\n{}", snippet)
603 let comma = if matches!(only.body.kind, hir::ExprKind::Block(..)) { "" } else { "," };
605 only.span.shrink_to_hi(),
606 format!("{}{}{} => todo!()", comma, pre_indentation, pattern),
609 [.., prev, last] if prev.span.ctxt() == last.span.ctxt() => {
610 if let Ok(snippet) = sm.span_to_snippet(prev.span.between(last.span)) {
612 if matches!(last.body.kind, hir::ExprKind::Block(..)) { "" } else { "," };
614 last.span.shrink_to_hi(),
618 snippet.strip_prefix(",").unwrap_or(&snippet),
628 "ensure that all possible cases are being handled by adding a match arm with a wildcard \
630 if patterns_len > 1 && patterns_len < 4 && suggestion.is_some() {
631 ", a match arm with multiple or-patterns"
633 // we are either not suggesting anything, or suggesting `_`
637 // non-exhaustive enum case
638 0 if suggestion.is_some() => " as shown",
640 1 if suggestion.is_some() => " or an explicit pattern as shown",
641 1 => " or an explicit pattern",
642 _ if suggestion.is_some() => " as shown, or multiple match arms",
643 _ => " or multiple match arms",
646 if let Some((span, sugg)) = suggestion {
647 err.span_suggestion_verbose(span, &msg, sugg, Applicability::HasPlaceholders);
654 crate fn joined_uncovered_patterns<'p, 'tcx>(
655 cx: &MatchCheckCtxt<'p, 'tcx>,
656 witnesses: &[DeconstructedPat<'p, 'tcx>],
658 const LIMIT: usize = 3;
659 let pat_to_str = |pat: &DeconstructedPat<'p, 'tcx>| pat.to_pat(cx).to_string();
662 [witness] => format!("`{}`", witness.to_pat(cx)),
663 [head @ .., tail] if head.len() < LIMIT => {
664 let head: Vec<_> = head.iter().map(pat_to_str).collect();
665 format!("`{}` and `{}`", head.join("`, `"), tail.to_pat(cx))
668 let (head, tail) = witnesses.split_at(LIMIT);
669 let head: Vec<_> = head.iter().map(pat_to_str).collect();
670 format!("`{}` and {} more", head.join("`, `"), tail.len())
675 crate fn pattern_not_covered_label(
676 witnesses: &[DeconstructedPat<'_, '_>],
677 joined_patterns: &str,
679 format!("pattern{} {} not covered", rustc_errors::pluralize!(witnesses.len()), joined_patterns)
682 /// Point at the definition of non-covered `enum` variants.
683 fn adt_defined_here<'p, 'tcx>(
684 cx: &MatchCheckCtxt<'p, 'tcx>,
685 err: &mut Diagnostic,
687 witnesses: &[DeconstructedPat<'p, 'tcx>],
689 let ty = ty.peel_refs();
690 if let ty::Adt(def, _) = ty.kind() {
691 let mut spans = vec![];
692 if witnesses.len() < 5 {
693 for sp in maybe_point_at_variant(cx, def, witnesses.iter()) {
700 .get_if_local(def.did)
701 .and_then(|node| node.ident())
702 .map(|ident| ident.span)
703 .unwrap_or_else(|| cx.tcx.def_span(def.did));
704 let mut span: MultiSpan =
705 if spans.is_empty() { def_span.into() } else { spans.clone().into() };
707 span.push_span_label(def_span, String::new());
709 span.push_span_label(pat, "not covered".to_string());
711 err.span_note(span, &format!("`{}` defined here", ty));
715 fn maybe_point_at_variant<'a, 'p: 'a, 'tcx: 'a>(
716 cx: &MatchCheckCtxt<'p, 'tcx>,
718 patterns: impl Iterator<Item = &'a DeconstructedPat<'p, 'tcx>>,
721 let mut covered = vec![];
722 for pattern in patterns {
723 if let Variant(variant_index) = pattern.ctor() {
724 if let ty::Adt(this_def, _) = pattern.ty().kind() && this_def.did != def.did {
727 let sp = def.variants[*variant_index].ident(cx.tcx).span;
728 if covered.contains(&sp) {
729 // Don't point at variants that have already been covered due to other patterns to avoid
735 covered.extend(maybe_point_at_variant(cx, def, pattern.iter_fields()));
740 /// Check if a by-value binding is by-value. That is, check if the binding's type is not `Copy`.
741 fn is_binding_by_move(cx: &MatchVisitor<'_, '_, '_>, hir_id: HirId, span: Span) -> bool {
742 !cx.typeck_results.node_type(hir_id).is_copy_modulo_regions(cx.tcx.at(span), cx.param_env)
745 /// Check that there are no borrow or move conflicts in `binding @ subpat` patterns.
747 /// For example, this would reject:
748 /// - `ref x @ Some(ref mut y)`,
749 /// - `ref mut x @ Some(ref y)`,
750 /// - `ref mut x @ Some(ref mut y)`,
751 /// - `ref mut? x @ Some(y)`, and
752 /// - `x @ Some(ref mut? y)`.
754 /// This analysis is *not* subsumed by NLL.
755 fn check_borrow_conflicts_in_at_patterns(cx: &MatchVisitor<'_, '_, '_>, pat: &Pat<'_>) {
756 // Extract `sub` in `binding @ sub`.
757 let (name, sub) = match &pat.kind {
758 hir::PatKind::Binding(.., name, Some(sub)) => (*name, sub),
761 let binding_span = pat.span.with_hi(name.span.hi());
763 let typeck_results = cx.typeck_results;
764 let sess = cx.tcx.sess;
766 // Get the binding move, extract the mutability if by-ref.
767 let mut_outer = match typeck_results.extract_binding_mode(sess, pat.hir_id, pat.span) {
768 Some(ty::BindByValue(_)) if is_binding_by_move(cx, pat.hir_id, pat.span) => {
769 // We have `x @ pat` where `x` is by-move. Reject all borrows in `pat`.
770 let mut conflicts_ref = Vec::new();
771 sub.each_binding(|_, hir_id, span, _| {
772 match typeck_results.extract_binding_mode(sess, hir_id, span) {
773 Some(ty::BindByValue(_)) | None => {}
774 Some(ty::BindByReference(_)) => conflicts_ref.push(span),
777 if !conflicts_ref.is_empty() {
778 let occurs_because = format!(
779 "move occurs because `{}` has type `{}` which does not implement the `Copy` trait",
781 typeck_results.node_type(pat.hir_id),
783 sess.struct_span_err(pat.span, "borrow of moved value")
784 .span_label(binding_span, format!("value moved into `{}` here", name))
785 .span_label(binding_span, occurs_because)
786 .span_labels(conflicts_ref, "value borrowed here after move")
791 Some(ty::BindByValue(_)) | None => return,
792 Some(ty::BindByReference(m)) => m,
795 // We now have `ref $mut_outer binding @ sub` (semantically).
796 // Recurse into each binding in `sub` and find mutability or move conflicts.
797 let mut conflicts_move = Vec::new();
798 let mut conflicts_mut_mut = Vec::new();
799 let mut conflicts_mut_ref = Vec::new();
800 sub.each_binding(|_, hir_id, span, name| {
801 match typeck_results.extract_binding_mode(sess, hir_id, span) {
802 Some(ty::BindByReference(mut_inner)) => match (mut_outer, mut_inner) {
803 (Mutability::Not, Mutability::Not) => {} // Both sides are `ref`.
804 (Mutability::Mut, Mutability::Mut) => conflicts_mut_mut.push((span, name)), // 2x `ref mut`.
805 _ => conflicts_mut_ref.push((span, name)), // `ref` + `ref mut` in either direction.
807 Some(ty::BindByValue(_)) if is_binding_by_move(cx, hir_id, span) => {
808 conflicts_move.push((span, name)) // `ref mut?` + by-move conflict.
810 Some(ty::BindByValue(_)) | None => {} // `ref mut?` + by-copy is fine.
814 // Report errors if any.
815 if !conflicts_mut_mut.is_empty() {
816 // Report mutability conflicts for e.g. `ref mut x @ Some(ref mut y)`.
818 .struct_span_err(pat.span, "cannot borrow value as mutable more than once at a time");
819 err.span_label(binding_span, format!("first mutable borrow, by `{}`, occurs here", name));
820 for (span, name) in conflicts_mut_mut {
821 err.span_label(span, format!("another mutable borrow, by `{}`, occurs here", name));
823 for (span, name) in conflicts_mut_ref {
824 err.span_label(span, format!("also borrowed as immutable, by `{}`, here", name));
826 for (span, name) in conflicts_move {
827 err.span_label(span, format!("also moved into `{}` here", name));
830 } else if !conflicts_mut_ref.is_empty() {
831 // Report mutability conflicts for e.g. `ref x @ Some(ref mut y)` or the converse.
832 let (primary, also) = match mut_outer {
833 Mutability::Mut => ("mutable", "immutable"),
834 Mutability::Not => ("immutable", "mutable"),
837 format!("cannot borrow value as {} because it is also borrowed as {}", also, primary);
838 let mut err = sess.struct_span_err(pat.span, &msg);
839 err.span_label(binding_span, format!("{} borrow, by `{}`, occurs here", primary, name));
840 for (span, name) in conflicts_mut_ref {
841 err.span_label(span, format!("{} borrow, by `{}`, occurs here", also, name));
843 for (span, name) in conflicts_move {
844 err.span_label(span, format!("also moved into `{}` here", name));
847 } else if !conflicts_move.is_empty() {
848 // Report by-ref and by-move conflicts, e.g. `ref x @ y`.
850 sess.struct_span_err(pat.span, "cannot move out of value because it is borrowed");
851 err.span_label(binding_span, format!("value borrowed, by `{}`, here", name));
852 for (span, name) in conflicts_move {
853 err.span_label(span, format!("value moved into `{}` here", name));
859 #[derive(Clone, Copy, Debug)]
868 fn let_source(tcx: TyCtxt<'_>, pat_id: HirId) -> LetSource {
871 let parent = hir.get_parent_node(pat_id);
872 let parent_node = hir.get(parent);
875 hir::Node::Arm(hir::Arm {
876 guard: Some(hir::Guard::IfLet(&hir::Pat { hir_id, .. }, _)),
878 }) if hir_id == pat_id => {
879 return LetSource::IfLetGuard;
881 hir::Node::Expr(hir::Expr { kind: hir::ExprKind::Let(..), span, .. }) => {
882 let expn_data = span.ctxt().outer_expn_data();
883 if let ExpnKind::Desugaring(DesugaringKind::LetElse) = expn_data.kind {
884 return LetSource::LetElse(expn_data.call_site);
890 let parent_parent = hir.get_parent_node(parent);
891 let parent_parent_node = hir.get(parent_parent);
893 let parent_parent_parent = hir.get_parent_node(parent_parent);
894 let parent_parent_parent_parent = hir.get_parent_node(parent_parent_parent);
895 let parent_parent_parent_parent_node = hir.get(parent_parent_parent_parent);
897 if let hir::Node::Expr(hir::Expr {
898 kind: hir::ExprKind::Loop(_, _, hir::LoopSource::While, _),
900 }) = parent_parent_parent_parent_node
902 return LetSource::WhileLet;
905 if let hir::Node::Expr(hir::Expr { kind: hir::ExprKind::If(..), .. }) = parent_parent_node {
906 return LetSource::IfLet;
909 LetSource::GenericLet
912 // Since this function is called within a let context, it is reasonable to assume that any parent
913 // `&&` infers a let chain
914 fn is_let_chain(tcx: TyCtxt<'_>, pat_id: HirId) -> bool {
916 let parent = hir.get_parent_node(pat_id);
917 let parent_parent = hir.get_parent_node(parent);
919 hir.get(parent_parent),
922 kind: hir::ExprKind::Binary(Spanned { node: hir::BinOpKind::And, .. }, ..),