| use super::_match::Usefulness::*; |
| use super::_match::WitnessPreference::*; |
| use super::_match::{expand_pattern, is_useful, MatchCheckCtxt, Matrix, PatStack}; |
| |
| use super::{PatCtxt, PatKind, PatternError}; |
| |
| use rustc::hir::map::Map; |
| use rustc::lint; |
| use rustc::session::parse::feature_err; |
| use rustc::session::Session; |
| use rustc::ty::{self, Ty, TyCtxt}; |
| use rustc_errors::{error_code, struct_span_err, Applicability, DiagnosticBuilder}; |
| use rustc_hir as hir; |
| use rustc_hir::def::*; |
| use rustc_hir::def_id::DefId; |
| use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor}; |
| use rustc_hir::{HirId, Pat}; |
| use rustc_span::symbol::sym; |
| use rustc_span::{MultiSpan, Span}; |
| use syntax::ast::Mutability; |
| |
| use std::slice; |
| |
| crate fn check_match(tcx: TyCtxt<'_>, def_id: DefId) { |
| let body_id = match tcx.hir().as_local_hir_id(def_id) { |
| None => return, |
| Some(id) => tcx.hir().body_owned_by(id), |
| }; |
| |
| let mut visitor = |
| MatchVisitor { tcx, tables: tcx.body_tables(body_id), param_env: tcx.param_env(def_id) }; |
| visitor.visit_body(tcx.hir().body(body_id)); |
| } |
| |
| fn create_e0004(sess: &Session, sp: Span, error_message: String) -> DiagnosticBuilder<'_> { |
| struct_span_err!(sess, sp, E0004, "{}", &error_message) |
| } |
| |
| struct MatchVisitor<'a, 'tcx> { |
| tcx: TyCtxt<'tcx>, |
| tables: &'a ty::TypeckTables<'tcx>, |
| param_env: ty::ParamEnv<'tcx>, |
| } |
| |
| impl<'tcx> Visitor<'tcx> for MatchVisitor<'_, 'tcx> { |
| type Map = Map<'tcx>; |
| |
| fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> { |
| NestedVisitorMap::None |
| } |
| |
| fn visit_expr(&mut self, ex: &'tcx hir::Expr<'tcx>) { |
| intravisit::walk_expr(self, ex); |
| |
| if let hir::ExprKind::Match(ref scrut, ref arms, source) = ex.kind { |
| self.check_match(scrut, arms, source); |
| } |
| } |
| |
| fn visit_local(&mut self, loc: &'tcx hir::Local<'tcx>) { |
| intravisit::walk_local(self, loc); |
| |
| let (msg, sp) = match loc.source { |
| hir::LocalSource::Normal => ("local binding", Some(loc.span)), |
| hir::LocalSource::ForLoopDesugar => ("`for` loop binding", None), |
| hir::LocalSource::AsyncFn => ("async fn binding", None), |
| hir::LocalSource::AwaitDesugar => ("`await` future binding", None), |
| }; |
| self.check_irrefutable(&loc.pat, msg, sp); |
| self.check_patterns(false, &loc.pat); |
| } |
| |
| fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) { |
| intravisit::walk_param(self, param); |
| self.check_irrefutable(¶m.pat, "function argument", None); |
| self.check_patterns(false, ¶m.pat); |
| } |
| } |
| |
| impl PatCtxt<'_, '_> { |
| fn report_inlining_errors(&self, pat_span: Span) { |
| for error in &self.errors { |
| match *error { |
| PatternError::StaticInPattern(span) => { |
| self.span_e0158(span, "statics cannot be referenced in patterns") |
| } |
| PatternError::AssocConstInPattern(span) => { |
| self.span_e0158(span, "associated consts cannot be referenced in patterns") |
| } |
| PatternError::FloatBug => { |
| // FIXME(#31407) this is only necessary because float parsing is buggy |
| ::rustc::mir::interpret::struct_error( |
| self.tcx.at(pat_span), |
| "could not evaluate float literal (see issue #31407)", |
| ) |
| .emit(); |
| } |
| PatternError::NonConstPath(span) => { |
| ::rustc::mir::interpret::struct_error( |
| self.tcx.at(span), |
| "runtime values cannot be referenced in patterns", |
| ) |
| .emit(); |
| } |
| } |
| } |
| } |
| |
| fn span_e0158(&self, span: Span, text: &str) { |
| struct_span_err!(self.tcx.sess, span, E0158, "{}", text).emit(); |
| } |
| } |
| |
| impl<'tcx> MatchVisitor<'_, 'tcx> { |
| fn check_patterns(&mut self, has_guard: bool, pat: &Pat<'_>) { |
| check_legality_of_move_bindings(self, has_guard, pat); |
| check_borrow_conflicts_in_at_patterns(self, pat); |
| if !self.tcx.features().bindings_after_at { |
| check_legality_of_bindings_in_at_patterns(self, pat); |
| } |
| check_for_bindings_named_same_as_variants(self, pat); |
| } |
| |
| fn check_match( |
| &mut self, |
| scrut: &hir::Expr<'_>, |
| arms: &'tcx [hir::Arm<'tcx>], |
| source: hir::MatchSource, |
| ) { |
| for arm in arms { |
| // Check the arm for some things unrelated to exhaustiveness. |
| self.check_patterns(arm.guard.is_some(), &arm.pat); |
| } |
| |
| let module = self.tcx.hir().get_module_parent(scrut.hir_id); |
| MatchCheckCtxt::create_and_enter(self.tcx, self.param_env, module, |ref mut cx| { |
| let mut have_errors = false; |
| |
| let inlined_arms: Vec<_> = arms |
| .iter() |
| .map(|arm| { |
| let mut patcx = PatCtxt::new(self.tcx, self.param_env, self.tables); |
| patcx.include_lint_checks(); |
| let pattern = patcx.lower_pattern(&arm.pat); |
| let pattern: &_ = cx.pattern_arena.alloc(expand_pattern(cx, pattern)); |
| if !patcx.errors.is_empty() { |
| patcx.report_inlining_errors(arm.pat.span); |
| have_errors = true; |
| } |
| (pattern, &*arm.pat, arm.guard.is_some()) |
| }) |
| .collect(); |
| |
| // Bail out early if inlining failed. |
| if have_errors { |
| return; |
| } |
| |
| // Fourth, check for unreachable arms. |
| let matrix = check_arms(cx, &inlined_arms, source); |
| |
| // Fifth, check if the match is exhaustive. |
| let scrut_ty = self.tables.node_type(scrut.hir_id); |
| // Note: An empty match isn't the same as an empty matrix for diagnostics purposes, |
| // since an empty matrix can occur when there are arms, if those arms all have guards. |
| let is_empty_match = inlined_arms.is_empty(); |
| check_exhaustive(cx, scrut_ty, scrut.span, &matrix, scrut.hir_id, is_empty_match); |
| }) |
| } |
| |
| fn check_irrefutable(&self, pat: &'tcx Pat<'tcx>, origin: &str, sp: Option<Span>) { |
| let module = self.tcx.hir().get_module_parent(pat.hir_id); |
| MatchCheckCtxt::create_and_enter(self.tcx, self.param_env, module, |ref mut cx| { |
| let mut patcx = PatCtxt::new(self.tcx, self.param_env, self.tables); |
| patcx.include_lint_checks(); |
| let pattern = patcx.lower_pattern(pat); |
| let pattern_ty = pattern.ty; |
| let pattern = cx.pattern_arena.alloc(expand_pattern(cx, pattern)); |
| let pats: Matrix<'_, '_> = vec![PatStack::from_pattern(pattern)].into_iter().collect(); |
| |
| let witnesses = match check_not_useful(cx, pattern_ty, &pats, pat.hir_id) { |
| Ok(_) => return, |
| Err(err) => err, |
| }; |
| |
| let joined_patterns = joined_uncovered_patterns(&witnesses); |
| let mut err = struct_span_err!( |
| self.tcx.sess, |
| pat.span, |
| E0005, |
| "refutable pattern in {}: {} not covered", |
| origin, |
| joined_patterns |
| ); |
| let suggest_if_let = match &pat.kind { |
| hir::PatKind::Path(hir::QPath::Resolved(None, path)) |
| if path.segments.len() == 1 && path.segments[0].args.is_none() => |
| { |
| const_not_var(&mut err, cx.tcx, pat, path); |
| false |
| } |
| _ => { |
| err.span_label( |
| pat.span, |
| pattern_not_covered_label(&witnesses, &joined_patterns), |
| ); |
| true |
| } |
| }; |
| |
| if let (Some(span), true) = (sp, suggest_if_let) { |
| err.note( |
| "`let` bindings require an \"irrefutable pattern\", like a `struct` or \ |
| an `enum` with only one variant", |
| ); |
| if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) { |
| err.span_suggestion( |
| span, |
| "you might want to use `if let` to ignore the variant that isn't matched", |
| format!("if {} {{ /* */ }}", &snippet[..snippet.len() - 1]), |
| Applicability::HasPlaceholders, |
| ); |
| } |
| err.note( |
| "for more information, visit \ |
| https://doc.rust-lang.org/book/ch18-02-refutability.html", |
| ); |
| } |
| |
| adt_defined_here(cx, &mut err, pattern_ty, &witnesses); |
| err.emit(); |
| }); |
| } |
| } |
| |
| /// A path pattern was interpreted as a constant, not a new variable. |
| /// This caused an irrefutable match failure in e.g. `let`. |
| fn const_not_var( |
| err: &mut DiagnosticBuilder<'_>, |
| tcx: TyCtxt<'_>, |
| pat: &Pat<'_>, |
| path: &hir::Path<'_>, |
| ) { |
| let descr = path.res.descr(); |
| err.span_label( |
| pat.span, |
| format!("interpreted as {} {} pattern, not a new variable", path.res.article(), descr,), |
| ); |
| |
| err.span_suggestion( |
| pat.span, |
| "introduce a variable instead", |
| format!("{}_var", path.segments[0].ident).to_lowercase(), |
| // Cannot use `MachineApplicable` as it's not really *always* correct |
| // because there may be such an identifier in scope or the user maybe |
| // really wanted to match against the constant. This is quite unlikely however. |
| Applicability::MaybeIncorrect, |
| ); |
| |
| if let Some(span) = tcx.hir().res_span(path.res) { |
| err.span_label(span, format!("{} defined here", descr)); |
| } |
| } |
| |
| fn check_for_bindings_named_same_as_variants(cx: &MatchVisitor<'_, '_>, pat: &Pat<'_>) { |
| pat.walk_always(|p| { |
| if let hir::PatKind::Binding(_, _, ident, None) = p.kind { |
| if let Some(ty::BindByValue(hir::Mutability::Not)) = |
| cx.tables.extract_binding_mode(cx.tcx.sess, p.hir_id, p.span) |
| { |
| let pat_ty = cx.tables.pat_ty(p).peel_refs(); |
| if let ty::Adt(edef, _) = pat_ty.kind { |
| if edef.is_enum() |
| && edef.variants.iter().any(|variant| { |
| variant.ident == ident && variant.ctor_kind == CtorKind::Const |
| }) |
| { |
| let ty_path = cx.tcx.def_path_str(edef.did); |
| cx.tcx |
| .struct_span_lint_hir( |
| lint::builtin::BINDINGS_WITH_VARIANT_NAME, |
| p.hir_id, |
| p.span, |
| &format!( |
| "pattern binding `{}` is named the same as one \ |
| of the variants of the type `{}`", |
| ident, ty_path |
| ), |
| ) |
| .code(error_code!(E0170)) |
| .span_suggestion( |
| p.span, |
| "to match on the variant, qualify the path", |
| format!("{}::{}", ty_path, ident), |
| Applicability::MachineApplicable, |
| ) |
| .emit(); |
| } |
| } |
| } |
| } |
| }); |
| } |
| |
| /// Checks for common cases of "catchall" patterns that may not be intended as such. |
| fn pat_is_catchall(pat: &Pat<'_>) -> bool { |
| match pat.kind { |
| hir::PatKind::Binding(.., None) => true, |
| hir::PatKind::Binding(.., Some(ref s)) => pat_is_catchall(s), |
| hir::PatKind::Ref(ref s, _) => pat_is_catchall(s), |
| hir::PatKind::Tuple(ref v, _) => v.iter().all(|p| pat_is_catchall(&p)), |
| _ => false, |
| } |
| } |
| |
| /// Check for unreachable patterns. |
| fn check_arms<'p, 'tcx>( |
| cx: &mut MatchCheckCtxt<'p, 'tcx>, |
| arms: &[(&'p super::Pat<'tcx>, &hir::Pat<'_>, bool)], |
| source: hir::MatchSource, |
| ) -> Matrix<'p, 'tcx> { |
| let mut seen = Matrix::empty(); |
| let mut catchall = None; |
| for (arm_index, (pat, hir_pat, has_guard)) in arms.iter().enumerate() { |
| let v = PatStack::from_pattern(pat); |
| |
| match is_useful(cx, &seen, &v, LeaveOutWitness, hir_pat.hir_id, true) { |
| NotUseful => { |
| match source { |
| hir::MatchSource::IfDesugar { .. } | hir::MatchSource::WhileDesugar => bug!(), |
| |
| hir::MatchSource::IfLetDesugar { .. } | hir::MatchSource::WhileLetDesugar => { |
| // check which arm we're on. |
| match arm_index { |
| // The arm with the user-specified pattern. |
| 0 => { |
| cx.tcx.lint_hir( |
| lint::builtin::UNREACHABLE_PATTERNS, |
| hir_pat.hir_id, |
| pat.span, |
| "unreachable pattern", |
| ); |
| } |
| // The arm with the wildcard pattern. |
| 1 => { |
| let msg = match source { |
| hir::MatchSource::IfLetDesugar { .. } => { |
| "irrefutable if-let pattern" |
| } |
| hir::MatchSource::WhileLetDesugar => { |
| "irrefutable while-let pattern" |
| } |
| _ => bug!(), |
| }; |
| cx.tcx.lint_hir( |
| lint::builtin::IRREFUTABLE_LET_PATTERNS, |
| hir_pat.hir_id, |
| pat.span, |
| msg, |
| ); |
| } |
| _ => bug!(), |
| } |
| } |
| |
| hir::MatchSource::ForLoopDesugar | hir::MatchSource::Normal => { |
| let mut err = cx.tcx.struct_span_lint_hir( |
| lint::builtin::UNREACHABLE_PATTERNS, |
| hir_pat.hir_id, |
| pat.span, |
| "unreachable pattern", |
| ); |
| // if we had a catchall pattern, hint at that |
| if let Some(catchall) = catchall { |
| err.span_label(pat.span, "unreachable pattern"); |
| err.span_label(catchall, "matches any value"); |
| } |
| err.emit(); |
| } |
| |
| // Unreachable patterns in try and await expressions occur when one of |
| // the arms are an uninhabited type. Which is OK. |
| hir::MatchSource::AwaitDesugar | hir::MatchSource::TryDesugar => {} |
| } |
| } |
| Useful(unreachable_subpatterns) => { |
| for pat in unreachable_subpatterns { |
| cx.tcx.lint_hir( |
| lint::builtin::UNREACHABLE_PATTERNS, |
| hir_pat.hir_id, |
| pat.span, |
| "unreachable pattern", |
| ); |
| } |
| } |
| UsefulWithWitness(_) => bug!(), |
| } |
| if !has_guard { |
| seen.push(v); |
| if catchall.is_none() && pat_is_catchall(hir_pat) { |
| catchall = Some(pat.span); |
| } |
| } |
| } |
| seen |
| } |
| |
| fn check_not_useful<'p, 'tcx>( |
| cx: &mut MatchCheckCtxt<'p, 'tcx>, |
| ty: Ty<'tcx>, |
| matrix: &Matrix<'p, 'tcx>, |
| hir_id: HirId, |
| ) -> Result<(), Vec<super::Pat<'tcx>>> { |
| let wild_pattern = cx.pattern_arena.alloc(super::Pat::wildcard_from_ty(ty)); |
| let v = PatStack::from_pattern(wild_pattern); |
| match is_useful(cx, matrix, &v, ConstructWitness, hir_id, true) { |
| NotUseful => Ok(()), // This is good, wildcard pattern isn't reachable. |
| UsefulWithWitness(pats) => Err(if pats.is_empty() { |
| bug!("Exhaustiveness check returned no witnesses") |
| } else { |
| pats.into_iter().map(|w| w.single_pattern()).collect() |
| }), |
| Useful(_) => bug!(), |
| } |
| } |
| |
| fn check_exhaustive<'p, 'tcx>( |
| cx: &mut MatchCheckCtxt<'p, 'tcx>, |
| scrut_ty: Ty<'tcx>, |
| sp: Span, |
| matrix: &Matrix<'p, 'tcx>, |
| hir_id: HirId, |
| is_empty_match: bool, |
| ) { |
| // In the absence of the `exhaustive_patterns` feature, empty matches are not detected by |
| // `is_useful` to exhaustively match uninhabited types, so we manually check here. |
| if is_empty_match && !cx.tcx.features().exhaustive_patterns { |
| let scrutinee_is_visibly_uninhabited = match scrut_ty.kind { |
| ty::Never => true, |
| ty::Adt(def, _) => { |
| def.is_enum() |
| && def.variants.is_empty() |
| && !cx.is_foreign_non_exhaustive_enum(scrut_ty) |
| } |
| _ => false, |
| }; |
| if scrutinee_is_visibly_uninhabited { |
| // If the type *is* uninhabited, an empty match is vacuously exhaustive. |
| return; |
| } |
| } |
| |
| let witnesses = match check_not_useful(cx, scrut_ty, matrix, hir_id) { |
| Ok(_) => return, |
| Err(err) => err, |
| }; |
| |
| let non_empty_enum = match scrut_ty.kind { |
| ty::Adt(def, _) => def.is_enum() && !def.variants.is_empty(), |
| _ => false, |
| }; |
| // In the case of an empty match, replace the '`_` not covered' diagnostic with something more |
| // informative. |
| let mut err; |
| if is_empty_match && !non_empty_enum { |
| err = create_e0004( |
| cx.tcx.sess, |
| sp, |
| format!("non-exhaustive patterns: type `{}` is non-empty", scrut_ty), |
| ); |
| } else { |
| let joined_patterns = joined_uncovered_patterns(&witnesses); |
| err = create_e0004( |
| cx.tcx.sess, |
| sp, |
| format!("non-exhaustive patterns: {} not covered", joined_patterns), |
| ); |
| err.span_label(sp, pattern_not_covered_label(&witnesses, &joined_patterns)); |
| }; |
| |
| adt_defined_here(cx, &mut err, scrut_ty, &witnesses); |
| err.help( |
| "ensure that all possible cases are being handled, \ |
| possibly by adding wildcards or more match arms", |
| ); |
| err.emit(); |
| } |
| |
| fn joined_uncovered_patterns(witnesses: &[super::Pat<'_>]) -> String { |
| const LIMIT: usize = 3; |
| match witnesses { |
| [] => bug!(), |
| [witness] => format!("`{}`", witness), |
| [head @ .., tail] if head.len() < LIMIT => { |
| let head: Vec<_> = head.iter().map(<_>::to_string).collect(); |
| format!("`{}` and `{}`", head.join("`, `"), tail) |
| } |
| _ => { |
| let (head, tail) = witnesses.split_at(LIMIT); |
| let head: Vec<_> = head.iter().map(<_>::to_string).collect(); |
| format!("`{}` and {} more", head.join("`, `"), tail.len()) |
| } |
| } |
| } |
| |
| fn pattern_not_covered_label(witnesses: &[super::Pat<'_>], joined_patterns: &str) -> String { |
| format!("pattern{} {} not covered", rustc_errors::pluralize!(witnesses.len()), joined_patterns) |
| } |
| |
| /// Point at the definition of non-covered `enum` variants. |
| fn adt_defined_here( |
| cx: &MatchCheckCtxt<'_, '_>, |
| err: &mut DiagnosticBuilder<'_>, |
| ty: Ty<'_>, |
| witnesses: &[super::Pat<'_>], |
| ) { |
| let ty = ty.peel_refs(); |
| if let ty::Adt(def, _) = ty.kind { |
| if let Some(sp) = cx.tcx.hir().span_if_local(def.did) { |
| err.span_label(sp, format!("`{}` defined here", ty)); |
| } |
| |
| if witnesses.len() < 4 { |
| for sp in maybe_point_at_variant(ty, &witnesses) { |
| err.span_label(sp, "not covered"); |
| } |
| } |
| } |
| } |
| |
| fn maybe_point_at_variant(ty: Ty<'_>, patterns: &[super::Pat<'_>]) -> Vec<Span> { |
| let mut covered = vec![]; |
| if let ty::Adt(def, _) = ty.kind { |
| // Don't point at variants that have already been covered due to other patterns to avoid |
| // visual clutter. |
| for pattern in patterns { |
| use PatKind::{AscribeUserType, Deref, Leaf, Or, Variant}; |
| match &*pattern.kind { |
| AscribeUserType { subpattern, .. } | Deref { subpattern } => { |
| covered.extend(maybe_point_at_variant(ty, slice::from_ref(&subpattern))); |
| } |
| Variant { adt_def, variant_index, subpatterns, .. } if adt_def.did == def.did => { |
| let sp = def.variants[*variant_index].ident.span; |
| if covered.contains(&sp) { |
| continue; |
| } |
| covered.push(sp); |
| |
| let pats = subpatterns |
| .iter() |
| .map(|field_pattern| field_pattern.pattern.clone()) |
| .collect::<Box<[_]>>(); |
| covered.extend(maybe_point_at_variant(ty, &pats)); |
| } |
| Leaf { subpatterns } => { |
| let pats = subpatterns |
| .iter() |
| .map(|field_pattern| field_pattern.pattern.clone()) |
| .collect::<Box<[_]>>(); |
| covered.extend(maybe_point_at_variant(ty, &pats)); |
| } |
| Or { pats } => { |
| let pats = pats.iter().cloned().collect::<Box<[_]>>(); |
| covered.extend(maybe_point_at_variant(ty, &pats)); |
| } |
| _ => {} |
| } |
| } |
| } |
| covered |
| } |
| |
| /// Check the legality of legality of by-move bindings. |
| fn check_legality_of_move_bindings(cx: &mut MatchVisitor<'_, '_>, has_guard: bool, pat: &Pat<'_>) { |
| let sess = cx.tcx.sess; |
| let tables = cx.tables; |
| |
| // Find all by-ref spans. |
| let mut by_ref_spans = Vec::new(); |
| pat.each_binding(|_, hir_id, span, _| { |
| if let Some(ty::BindByReference(_)) = tables.extract_binding_mode(sess, hir_id, span) { |
| by_ref_spans.push(span); |
| } |
| }); |
| |
| // Find bad by-move spans: |
| let by_move_spans = &mut Vec::new(); |
| let mut check_move = |p: &Pat<'_>, sub: Option<&Pat<'_>>| { |
| // Check legality of moving out of the enum. |
| // |
| // `x @ Foo(..)` is legal, but `x @ Foo(y)` isn't. |
| if sub.map_or(false, |p| p.contains_bindings()) { |
| struct_span_err!(sess, p.span, E0007, "cannot bind by-move with sub-bindings") |
| .span_label(p.span, "binds an already bound by-move value by moving it") |
| .emit(); |
| } else if !has_guard && !by_ref_spans.is_empty() { |
| by_move_spans.push(p.span); |
| } |
| }; |
| pat.walk_always(|p| { |
| if let hir::PatKind::Binding(.., sub) = &p.kind { |
| if let Some(ty::BindByValue(_)) = tables.extract_binding_mode(sess, p.hir_id, p.span) { |
| let pat_ty = tables.node_type(p.hir_id); |
| if !pat_ty.is_copy_modulo_regions(cx.tcx, cx.param_env, pat.span) { |
| check_move(p, sub.as_deref()); |
| } |
| } |
| } |
| }); |
| |
| // Found some bad by-move spans, error! |
| if !by_move_spans.is_empty() { |
| let mut err = struct_span_err!( |
| sess, |
| MultiSpan::from_spans(by_move_spans.clone()), |
| E0009, |
| "cannot bind by-move and by-ref in the same pattern", |
| ); |
| for span in by_ref_spans.iter() { |
| err.span_label(*span, "by-ref pattern here"); |
| } |
| for span in by_move_spans.iter() { |
| err.span_label(*span, "by-move pattern here"); |
| } |
| err.emit(); |
| } |
| } |
| |
| /// Check that there are no borrow conflicts in `binding @ subpat` patterns. |
| /// |
| /// For example, this would reject: |
| /// - `ref x @ Some(ref mut y)`, |
| /// - `ref mut x @ Some(ref y)` |
| /// - `ref mut x @ Some(ref mut y)`. |
| /// |
| /// This analysis is *not* subsumed by NLL. |
| fn check_borrow_conflicts_in_at_patterns(cx: &MatchVisitor<'_, '_>, pat: &Pat<'_>) { |
| let tab = cx.tables; |
| let sess = cx.tcx.sess; |
| // Get the mutability of `p` if it's by-ref. |
| let extract_binding_mut = |hir_id, span| match tab.extract_binding_mode(sess, hir_id, span)? { |
| ty::BindByValue(_) => None, |
| ty::BindByReference(m) => Some(m), |
| }; |
| pat.walk_always(|pat| { |
| // Extract `sub` in `binding @ sub`. |
| let (name, sub) = match &pat.kind { |
| hir::PatKind::Binding(.., name, Some(sub)) => (*name, sub), |
| _ => return, |
| }; |
| |
| // Extract the mutability. |
| let mut_outer = match extract_binding_mut(pat.hir_id, pat.span) { |
| None => return, |
| Some(m) => m, |
| }; |
| |
| // We now have `ref $mut_outer binding @ sub` (semantically). |
| // Recurse into each binding in `sub` and find mutability conflicts. |
| let mut conflicts_mut_mut = Vec::new(); |
| let mut conflicts_mut_ref = Vec::new(); |
| sub.each_binding(|_, hir_id, span, _| { |
| if let Some(mut_inner) = extract_binding_mut(hir_id, span) { |
| match (mut_outer, mut_inner) { |
| (Mutability::Not, Mutability::Not) => {} |
| (Mutability::Mut, Mutability::Mut) => conflicts_mut_mut.push(span), |
| _ => conflicts_mut_ref.push(span), |
| } |
| } |
| }); |
| |
| // Report errors if any. |
| let binding_span = pat.span.with_hi(name.span.hi()); |
| if !conflicts_mut_mut.is_empty() { |
| // Report mutability conflicts for e.g. `ref mut x @ Some(ref mut y)`. |
| let msg = &format!("cannot borrow `{}` as mutable more than once at a time", name); |
| let mut err = sess.struct_span_err(pat.span, msg); |
| err.span_label(binding_span, "first mutable borrow occurs here"); |
| for sp in conflicts_mut_mut { |
| err.span_label(sp, "another mutable borrow occurs here"); |
| } |
| for sp in conflicts_mut_ref { |
| err.span_label(sp, "also borrowed as immutable here"); |
| } |
| err.emit(); |
| } else if !conflicts_mut_ref.is_empty() { |
| // Report mutability conflicts for e.g. `ref x @ Some(ref mut y)` or the converse. |
| let (primary, also) = match mut_outer { |
| Mutability::Mut => ("mutable", "immutable"), |
| Mutability::Not => ("immutable", "mutable"), |
| }; |
| let msg = &format!( |
| "cannot borrow `{}` as {} because it is also borrowed as {}", |
| name, also, primary, |
| ); |
| let mut err = sess.struct_span_err(pat.span, msg); |
| err.span_label(binding_span, &format!("{} borrow occurs here", primary)); |
| for sp in conflicts_mut_ref { |
| err.span_label(sp, &format!("{} borrow occurs here", also)); |
| } |
| err.emit(); |
| } |
| }); |
| } |
| |
| /// Forbids bindings in `@` patterns. This used to be is necessary for memory safety, |
| /// because of the way rvalues were handled in the borrow check. (See issue #14587.) |
| fn check_legality_of_bindings_in_at_patterns(cx: &MatchVisitor<'_, '_>, pat: &Pat<'_>) { |
| AtBindingPatternVisitor { cx, bindings_allowed: true }.visit_pat(pat); |
| |
| struct AtBindingPatternVisitor<'a, 'b, 'tcx> { |
| cx: &'a MatchVisitor<'b, 'tcx>, |
| bindings_allowed: bool, |
| } |
| |
| impl<'v> Visitor<'v> for AtBindingPatternVisitor<'_, '_, '_> { |
| type Map = Map<'v>; |
| |
| fn nested_visit_map(&mut self) -> NestedVisitorMap<'_, Self::Map> { |
| NestedVisitorMap::None |
| } |
| |
| fn visit_pat(&mut self, pat: &Pat<'_>) { |
| match pat.kind { |
| hir::PatKind::Binding(.., ref subpat) => { |
| if !self.bindings_allowed { |
| feature_err( |
| &self.cx.tcx.sess.parse_sess, |
| sym::bindings_after_at, |
| pat.span, |
| "pattern bindings after an `@` are unstable", |
| ) |
| .emit(); |
| } |
| |
| if subpat.is_some() { |
| let bindings_were_allowed = self.bindings_allowed; |
| self.bindings_allowed = false; |
| intravisit::walk_pat(self, pat); |
| self.bindings_allowed = bindings_were_allowed; |
| } |
| } |
| _ => intravisit::walk_pat(self, pat), |
| } |
| } |
| } |
| } |
