| // Copyright 2012-2016 The Rust Project Developers. See the COPYRIGHT |
| // file at the top-level directory of this distribution and at |
| // http://rust-lang.org/COPYRIGHT. |
| // |
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or |
| // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license |
| // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your |
| // option. This file may not be copied, modified, or distributed |
| // except according to those terms. |
| |
| use _match::{MatchCheckCtxt, Matrix, expand_pattern, is_useful}; |
| use _match::Usefulness::*; |
| use _match::WitnessPreference::*; |
| |
| use pattern::{Pattern, PatternContext, PatternError, PatternKind}; |
| |
| use rustc::middle::expr_use_visitor::{ConsumeMode, Delegate, ExprUseVisitor}; |
| use rustc::middle::expr_use_visitor::{LoanCause, MutateMode}; |
| use rustc::middle::expr_use_visitor as euv; |
| use rustc::middle::mem_categorization::{cmt}; |
| use rustc::middle::region; |
| use rustc::session::Session; |
| use rustc::ty::{self, Ty, TyCtxt}; |
| use rustc::ty::subst::Substs; |
| use rustc::lint; |
| use rustc_errors::DiagnosticBuilder; |
| |
| use rustc::hir::def::*; |
| use rustc::hir::intravisit::{self, Visitor, FnKind, NestedVisitorMap}; |
| use rustc::hir::{self, Pat, PatKind}; |
| |
| use rustc_back::slice; |
| |
| use syntax::ast; |
| use syntax::ptr::P; |
| use syntax_pos::{Span, DUMMY_SP}; |
| |
| struct OuterVisitor<'a, 'tcx: 'a> { tcx: TyCtxt<'a, 'tcx, 'tcx> } |
| |
| impl<'a, 'tcx> Visitor<'tcx> for OuterVisitor<'a, 'tcx> { |
| fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> { |
| NestedVisitorMap::OnlyBodies(&self.tcx.hir) |
| } |
| |
| fn visit_fn(&mut self, fk: FnKind<'tcx>, fd: &'tcx hir::FnDecl, |
| b: hir::BodyId, s: Span, id: ast::NodeId) { |
| intravisit::walk_fn(self, fk, fd, b, s, id); |
| |
| let def_id = self.tcx.hir.local_def_id(id); |
| |
| MatchVisitor { |
| tcx: self.tcx, |
| tables: self.tcx.body_tables(b), |
| region_scope_tree: &self.tcx.region_scope_tree(def_id), |
| param_env: self.tcx.param_env(def_id), |
| identity_substs: Substs::identity_for_item(self.tcx, def_id), |
| }.visit_body(self.tcx.hir.body(b)); |
| } |
| } |
| |
| pub fn check_crate<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) { |
| tcx.hir.krate().visit_all_item_likes(&mut OuterVisitor { tcx: tcx }.as_deep_visitor()); |
| tcx.sess.abort_if_errors(); |
| } |
| |
| fn create_e0004<'a>(sess: &'a Session, sp: Span, error_message: String) -> DiagnosticBuilder<'a> { |
| struct_span_err!(sess, sp, E0004, "{}", &error_message) |
| } |
| |
| struct MatchVisitor<'a, 'tcx: 'a> { |
| tcx: TyCtxt<'a, 'tcx, 'tcx>, |
| tables: &'a ty::TypeckTables<'tcx>, |
| param_env: ty::ParamEnv<'tcx>, |
| identity_substs: &'tcx Substs<'tcx>, |
| region_scope_tree: &'a region::ScopeTree, |
| } |
| |
| impl<'a, 'tcx> Visitor<'tcx> for MatchVisitor<'a, 'tcx> { |
| fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> { |
| NestedVisitorMap::None |
| } |
| |
| fn visit_expr(&mut self, ex: &'tcx hir::Expr) { |
| intravisit::walk_expr(self, ex); |
| |
| match ex.node { |
| hir::ExprMatch(ref scrut, ref arms, source) => { |
| self.check_match(scrut, arms, source); |
| } |
| _ => {} |
| } |
| } |
| |
| fn visit_local(&mut self, loc: &'tcx hir::Local) { |
| intravisit::walk_local(self, loc); |
| |
| self.check_irrefutable(&loc.pat, match loc.source { |
| hir::LocalSource::Normal => "local binding", |
| hir::LocalSource::ForLoopDesugar => "`for` loop binding", |
| }); |
| |
| // Check legality of move bindings and `@` patterns. |
| self.check_patterns(false, slice::ref_slice(&loc.pat)); |
| } |
| |
| fn visit_body(&mut self, body: &'tcx hir::Body) { |
| intravisit::walk_body(self, body); |
| |
| for arg in &body.arguments { |
| self.check_irrefutable(&arg.pat, "function argument"); |
| self.check_patterns(false, slice::ref_slice(&arg.pat)); |
| } |
| } |
| } |
| |
| impl<'a, 'tcx> PatternContext<'a, 'tcx> { |
| fn report_inlining_errors(&self, pat_span: Span) { |
| for error in &self.errors { |
| match *error { |
| PatternError::StaticInPattern(span) => { |
| span_err!(self.tcx.sess, span, E0158, |
| "statics cannot be referenced in patterns"); |
| } |
| PatternError::ConstEval(ref err) => { |
| err.report(self.tcx, pat_span, "pattern"); |
| } |
| } |
| } |
| } |
| } |
| |
| impl<'a, 'tcx> MatchVisitor<'a, 'tcx> { |
| fn check_patterns(&self, has_guard: bool, pats: &[P<Pat>]) { |
| check_legality_of_move_bindings(self, has_guard, pats); |
| for pat in pats { |
| check_legality_of_bindings_in_at_patterns(self, pat); |
| } |
| } |
| |
| fn check_match( |
| &self, |
| scrut: &hir::Expr, |
| arms: &'tcx [hir::Arm], |
| source: hir::MatchSource) |
| { |
| for arm in arms { |
| // First, check legality of move bindings. |
| self.check_patterns(arm.guard.is_some(), &arm.pats); |
| |
| // Second, if there is a guard on each arm, make sure it isn't |
| // assigning or borrowing anything mutably. |
| if let Some(ref guard) = arm.guard { |
| check_for_mutation_in_guard(self, &guard); |
| } |
| |
| // Third, perform some lints. |
| for pat in &arm.pats { |
| check_for_bindings_named_the_same_as_variants(self, pat); |
| } |
| } |
| |
| let module = self.tcx.hir.get_module_parent(scrut.id); |
| MatchCheckCtxt::create_and_enter(self.tcx, module, |ref mut cx| { |
| let mut have_errors = false; |
| |
| let inlined_arms : Vec<(Vec<_>, _)> = arms.iter().map(|arm| ( |
| arm.pats.iter().map(|pat| { |
| let mut patcx = PatternContext::new(self.tcx, |
| self.param_env.and(self.identity_substs), |
| self.tables); |
| let pattern = expand_pattern(cx, patcx.lower_pattern(&pat)); |
| if !patcx.errors.is_empty() { |
| patcx.report_inlining_errors(pat.span); |
| have_errors = true; |
| } |
| (pattern, &**pat) |
| }).collect(), |
| arm.guard.as_ref().map(|e| &**e) |
| )).collect(); |
| |
| // Bail out early if inlining failed. |
| if have_errors { |
| return; |
| } |
| |
| // Fourth, check for unreachable arms. |
| check_arms(cx, &inlined_arms, source); |
| |
| // Then, if the match has no arms, check whether the scrutinee |
| // is uninhabited. |
| let pat_ty = self.tables.node_id_to_type(scrut.hir_id); |
| let module = self.tcx.hir.get_module_parent(scrut.id); |
| if inlined_arms.is_empty() { |
| let scrutinee_is_uninhabited = if self.tcx.sess.features.borrow().never_type { |
| pat_ty.is_uninhabited_from(module, self.tcx) |
| } else { |
| self.conservative_is_uninhabited(pat_ty) |
| }; |
| if !scrutinee_is_uninhabited { |
| // We know the type is inhabited, so this must be wrong |
| let mut err = create_e0004(self.tcx.sess, scrut.span, |
| format!("non-exhaustive patterns: type {} \ |
| is non-empty", |
| pat_ty)); |
| span_help!(&mut err, scrut.span, |
| "Please ensure that all possible cases are being handled; \ |
| possibly adding wildcards or more match arms."); |
| err.emit(); |
| } |
| // If the type *is* uninhabited, it's vacuously exhaustive |
| return; |
| } |
| |
| let matrix: Matrix = inlined_arms |
| .iter() |
| .filter(|&&(_, guard)| guard.is_none()) |
| .flat_map(|arm| &arm.0) |
| .map(|pat| vec![pat.0]) |
| .collect(); |
| let scrut_ty = self.tables.node_id_to_type(scrut.hir_id); |
| check_exhaustive(cx, scrut_ty, scrut.span, &matrix); |
| }) |
| } |
| |
| fn conservative_is_uninhabited(&self, scrutinee_ty: Ty<'tcx>) -> bool { |
| // "rustc-1.0-style" uncontentious uninhabitableness check |
| match scrutinee_ty.sty { |
| ty::TyNever => true, |
| ty::TyAdt(def, _) => def.variants.is_empty(), |
| _ => false |
| } |
| } |
| |
| fn check_irrefutable(&self, pat: &'tcx Pat, origin: &str) { |
| let module = self.tcx.hir.get_module_parent(pat.id); |
| MatchCheckCtxt::create_and_enter(self.tcx, module, |ref mut cx| { |
| let mut patcx = PatternContext::new(self.tcx, |
| self.param_env.and(self.identity_substs), |
| self.tables); |
| let pattern = patcx.lower_pattern(pat); |
| let pattern_ty = pattern.ty; |
| let pats : Matrix = vec![vec![ |
| expand_pattern(cx, pattern) |
| ]].into_iter().collect(); |
| |
| let wild_pattern = Pattern { |
| ty: pattern_ty, |
| span: DUMMY_SP, |
| kind: box PatternKind::Wild, |
| }; |
| let witness = match is_useful(cx, &pats, &[&wild_pattern], ConstructWitness) { |
| UsefulWithWitness(witness) => witness, |
| NotUseful => return, |
| Useful => bug!() |
| }; |
| |
| let pattern_string = witness[0].single_pattern().to_string(); |
| let mut diag = struct_span_err!( |
| self.tcx.sess, pat.span, E0005, |
| "refutable pattern in {}: `{}` not covered", |
| origin, pattern_string |
| ); |
| diag.span_label(pat.span, format!("pattern `{}` not covered", pattern_string)); |
| diag.emit(); |
| }); |
| } |
| } |
| |
| fn check_for_bindings_named_the_same_as_variants(cx: &MatchVisitor, pat: &Pat) { |
| pat.walk(|p| { |
| if let PatKind::Binding(_, _, name, None) = p.node { |
| let bm = *cx.tables |
| .pat_binding_modes() |
| .get(p.hir_id) |
| .expect("missing binding mode"); |
| |
| if bm != ty::BindByValue(hir::MutImmutable) { |
| // Nothing to check. |
| return true; |
| } |
| let pat_ty = cx.tables.pat_ty(p); |
| if let ty::TyAdt(edef, _) = pat_ty.sty { |
| if edef.is_enum() && edef.variants.iter().any(|variant| { |
| variant.name == name.node && variant.ctor_kind == CtorKind::Const |
| }) { |
| let ty_path = cx.tcx.item_path_str(edef.did); |
| let mut err = struct_span_warn!(cx.tcx.sess, p.span, E0170, |
| "pattern binding `{}` is named the same as one \ |
| of the variants of the type `{}`", |
| name.node, ty_path); |
| help!(err, |
| "if you meant to match on a variant, \ |
| consider making the path in the pattern qualified: `{}::{}`", |
| ty_path, name.node); |
| err.emit(); |
| } |
| } |
| } |
| true |
| }); |
| } |
| |
| /// Checks for common cases of "catchall" patterns that may not be intended as such. |
| fn pat_is_catchall(pat: &Pat) -> bool { |
| match pat.node { |
| PatKind::Binding(.., None) => true, |
| PatKind::Binding(.., Some(ref s)) => pat_is_catchall(s), |
| PatKind::Ref(ref s, _) => pat_is_catchall(s), |
| PatKind::Tuple(ref v, _) => v.iter().all(|p| { |
| pat_is_catchall(&p) |
| }), |
| _ => false |
| } |
| } |
| |
| // Check for unreachable patterns |
| fn check_arms<'a, 'tcx>(cx: &mut MatchCheckCtxt<'a, 'tcx>, |
| arms: &[(Vec<(&'a Pattern<'tcx>, &hir::Pat)>, Option<&hir::Expr>)], |
| source: hir::MatchSource) |
| { |
| let mut seen = Matrix::empty(); |
| let mut catchall = None; |
| let mut printed_if_let_err = false; |
| for (arm_index, &(ref pats, guard)) in arms.iter().enumerate() { |
| for &(pat, hir_pat) in pats { |
| let v = vec![pat]; |
| |
| match is_useful(cx, &seen, &v, LeaveOutWitness) { |
| NotUseful => { |
| match source { |
| hir::MatchSource::IfLetDesugar { .. } => { |
| if printed_if_let_err { |
| // we already printed an irrefutable if-let pattern error. |
| // We don't want two, that's just confusing. |
| } else { |
| // find the first arm pattern so we can use its span |
| let &(ref first_arm_pats, _) = &arms[0]; |
| let first_pat = &first_arm_pats[0]; |
| let span = first_pat.0.span; |
| struct_span_err!(cx.tcx.sess, span, E0162, |
| "irrefutable if-let pattern") |
| .span_label(span, "irrefutable pattern") |
| .emit(); |
| printed_if_let_err = true; |
| } |
| }, |
| |
| hir::MatchSource::WhileLetDesugar => { |
| // find the first arm pattern so we can use its span |
| let &(ref first_arm_pats, _) = &arms[0]; |
| let first_pat = &first_arm_pats[0]; |
| let span = first_pat.0.span; |
| |
| // check which arm we're on. |
| match arm_index { |
| // The arm with the user-specified pattern. |
| 0 => { |
| cx.tcx.lint_node( |
| lint::builtin::UNREACHABLE_PATTERNS, |
| hir_pat.id, pat.span, |
| "unreachable pattern"); |
| }, |
| // The arm with the wildcard pattern. |
| 1 => { |
| struct_span_err!(cx.tcx.sess, span, E0165, |
| "irrefutable while-let pattern") |
| .span_label(span, "irrefutable pattern") |
| .emit(); |
| }, |
| _ => bug!(), |
| } |
| }, |
| |
| hir::MatchSource::ForLoopDesugar | |
| hir::MatchSource::Normal => { |
| let mut err = cx.tcx.struct_span_lint_node( |
| lint::builtin::UNREACHABLE_PATTERNS, |
| hir_pat.id, |
| pat.span, |
| "unreachable pattern", |
| ); |
| // if we had a catchall pattern, hint at that |
| if let Some(catchall) = catchall { |
| err.span_label(pat.span, "this is an unreachable pattern"); |
| err.span_note(catchall, "this pattern matches any value"); |
| } |
| err.emit(); |
| }, |
| |
| // Unreachable patterns in try expressions occur when one of the arms |
| // are an uninhabited type. Which is OK. |
| hir::MatchSource::TryDesugar => {} |
| } |
| } |
| Useful => (), |
| UsefulWithWitness(_) => bug!() |
| } |
| if guard.is_none() { |
| seen.push(v); |
| if catchall.is_none() && pat_is_catchall(hir_pat) { |
| catchall = Some(pat.span); |
| } |
| } |
| } |
| } |
| } |
| |
| fn check_exhaustive<'a, 'tcx>(cx: &mut MatchCheckCtxt<'a, 'tcx>, |
| scrut_ty: Ty<'tcx>, |
| sp: Span, |
| matrix: &Matrix<'a, 'tcx>) { |
| let wild_pattern = Pattern { |
| ty: scrut_ty, |
| span: DUMMY_SP, |
| kind: box PatternKind::Wild, |
| }; |
| match is_useful(cx, matrix, &[&wild_pattern], ConstructWitness) { |
| UsefulWithWitness(pats) => { |
| let witnesses = if pats.is_empty() { |
| vec![&wild_pattern] |
| } else { |
| pats.iter().map(|w| w.single_pattern()).collect() |
| }; |
| |
| const LIMIT: usize = 3; |
| let joined_patterns = match witnesses.len() { |
| 0 => bug!(), |
| 1 => format!("`{}`", witnesses[0]), |
| 2...LIMIT => { |
| let (tail, head) = witnesses.split_last().unwrap(); |
| let head: Vec<_> = head.iter().map(|w| w.to_string()).collect(); |
| format!("`{}` and `{}`", head.join("`, `"), tail) |
| }, |
| _ => { |
| let (head, tail) = witnesses.split_at(LIMIT); |
| let head: Vec<_> = head.iter().map(|w| w.to_string()).collect(); |
| format!("`{}` and {} more", head.join("`, `"), tail.len()) |
| } |
| }; |
| |
| let label_text = match witnesses.len() { |
| 1 => format!("pattern {} not covered", joined_patterns), |
| _ => format!("patterns {} not covered", joined_patterns) |
| }; |
| create_e0004(cx.tcx.sess, sp, |
| format!("non-exhaustive patterns: {} not covered", |
| joined_patterns)) |
| .span_label(sp, label_text) |
| .emit(); |
| } |
| NotUseful => { |
| // This is good, wildcard pattern isn't reachable |
| }, |
| _ => bug!() |
| } |
| } |
| |
| // Legality of move bindings checking |
| fn check_legality_of_move_bindings(cx: &MatchVisitor, |
| has_guard: bool, |
| pats: &[P<Pat>]) { |
| let mut by_ref_span = None; |
| for pat in pats { |
| pat.each_binding(|_, id, span, _path| { |
| let hir_id = cx.tcx.hir.node_to_hir_id(id); |
| let bm = *cx.tables |
| .pat_binding_modes() |
| .get(hir_id) |
| .expect("missing binding mode"); |
| if let ty::BindByReference(..) = bm { |
| by_ref_span = Some(span); |
| } |
| }) |
| } |
| |
| let 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!(cx.tcx.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 { |
| struct_span_err!(cx.tcx.sess, p.span, E0008, |
| "cannot bind by-move into a pattern guard") |
| .span_label(p.span, "moves value into pattern guard") |
| .emit(); |
| } else if by_ref_span.is_some() { |
| struct_span_err!(cx.tcx.sess, p.span, E0009, |
| "cannot bind by-move and by-ref in the same pattern") |
| .span_label(p.span, "by-move pattern here") |
| .span_label(by_ref_span.unwrap(), "both by-ref and by-move used") |
| .emit(); |
| } |
| }; |
| |
| for pat in pats { |
| pat.walk(|p| { |
| if let PatKind::Binding(_, _, _, ref sub) = p.node { |
| let bm = *cx.tables |
| .pat_binding_modes() |
| .get(p.hir_id) |
| .expect("missing binding mode"); |
| match bm { |
| ty::BindByValue(..) => { |
| let pat_ty = cx.tables.node_id_to_type(p.hir_id); |
| if pat_ty.moves_by_default(cx.tcx, cx.param_env, pat.span) { |
| check_move(p, sub.as_ref().map(|p| &**p)); |
| } |
| } |
| _ => {} |
| } |
| } |
| true |
| }); |
| } |
| } |
| |
| /// Ensures that a pattern guard doesn't borrow by mutable reference or |
| /// assign. |
| /// |
| /// FIXME: this should be done by borrowck. |
| fn check_for_mutation_in_guard(cx: &MatchVisitor, guard: &hir::Expr) { |
| let mut checker = MutationChecker { |
| cx, |
| }; |
| ExprUseVisitor::new(&mut checker, cx.tcx, cx.param_env, cx.region_scope_tree, cx.tables) |
| .walk_expr(guard); |
| } |
| |
| struct MutationChecker<'a, 'tcx: 'a> { |
| cx: &'a MatchVisitor<'a, 'tcx>, |
| } |
| |
| impl<'a, 'tcx> Delegate<'tcx> for MutationChecker<'a, 'tcx> { |
| fn matched_pat(&mut self, _: &Pat, _: cmt, _: euv::MatchMode) {} |
| fn consume(&mut self, _: ast::NodeId, _: Span, _: cmt, _: ConsumeMode) {} |
| fn consume_pat(&mut self, _: &Pat, _: cmt, _: ConsumeMode) {} |
| fn borrow(&mut self, |
| _: ast::NodeId, |
| span: Span, |
| _: cmt, |
| _: ty::Region<'tcx>, |
| kind:ty:: BorrowKind, |
| _: LoanCause) { |
| match kind { |
| ty::MutBorrow => { |
| struct_span_err!(self.cx.tcx.sess, span, E0301, |
| "cannot mutably borrow in a pattern guard") |
| .span_label(span, "borrowed mutably in pattern guard") |
| .emit(); |
| } |
| ty::ImmBorrow | ty::UniqueImmBorrow => {} |
| } |
| } |
| fn decl_without_init(&mut self, _: ast::NodeId, _: Span) {} |
| fn mutate(&mut self, _: ast::NodeId, span: Span, _: cmt, mode: MutateMode) { |
| match mode { |
| MutateMode::JustWrite | MutateMode::WriteAndRead => { |
| struct_span_err!(self.cx.tcx.sess, span, E0302, "cannot assign in a pattern guard") |
| .span_label(span, "assignment in pattern guard") |
| .emit(); |
| } |
| MutateMode::Init => {} |
| } |
| } |
| } |
| |
| /// Forbids bindings in `@` patterns. This is necessary for memory safety, |
| /// because of the way rvalues are handled in the borrow check. (See issue |
| /// #14587.) |
| fn check_legality_of_bindings_in_at_patterns(cx: &MatchVisitor, pat: &Pat) { |
| AtBindingPatternVisitor { cx: cx, bindings_allowed: true }.visit_pat(pat); |
| } |
| |
| struct AtBindingPatternVisitor<'a, 'b:'a, 'tcx:'b> { |
| cx: &'a MatchVisitor<'b, 'tcx>, |
| bindings_allowed: bool |
| } |
| |
| impl<'a, 'b, 'tcx, 'v> Visitor<'v> for AtBindingPatternVisitor<'a, 'b, 'tcx> { |
| fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'v> { |
| NestedVisitorMap::None |
| } |
| |
| fn visit_pat(&mut self, pat: &Pat) { |
| match pat.node { |
| PatKind::Binding(.., ref subpat) => { |
| if !self.bindings_allowed { |
| struct_span_err!(self.cx.tcx.sess, pat.span, E0303, |
| "pattern bindings are not allowed after an `@`") |
| .span_label(pat.span, "not allowed after `@`") |
| .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), |
| } |
| } |
| } |