| // 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 self::Constructor::*; |
| use self::Usefulness::*; |
| use self::WitnessPreference::*; |
| |
| use rustc::dep_graph::DepNode; |
| use rustc::middle::const_val::ConstVal; |
| use ::{eval_const_expr, eval_const_expr_partial, compare_const_vals}; |
| use ::{const_expr_to_pat, lookup_const_by_id}; |
| use ::EvalHint::ExprTypeChecked; |
| use eval::report_const_eval_err; |
| use rustc::hir::def::*; |
| use rustc::hir::def_id::{DefId}; |
| 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::hir::pat_util::*; |
| use rustc::traits::ProjectionMode; |
| use rustc::ty::*; |
| use rustc::ty; |
| use std::cmp::Ordering; |
| use std::fmt; |
| use std::iter::{FromIterator, IntoIterator, repeat}; |
| |
| use rustc::hir; |
| use rustc::hir::{Pat, PatKind}; |
| use rustc::hir::intravisit::{self, Visitor, FnKind}; |
| use rustc_back::slice; |
| |
| use syntax::ast::{self, DUMMY_NODE_ID, NodeId}; |
| use syntax::codemap::Spanned; |
| use syntax_pos::{Span, DUMMY_SP}; |
| use rustc::hir::fold::{Folder, noop_fold_pat}; |
| use rustc::hir::print::pat_to_string; |
| use syntax::ptr::P; |
| use rustc::util::common::ErrorReported; |
| use rustc::util::nodemap::FnvHashMap; |
| |
| pub const DUMMY_WILD_PAT: &'static Pat = &Pat { |
| id: DUMMY_NODE_ID, |
| node: PatKind::Wild, |
| span: DUMMY_SP |
| }; |
| |
| struct Matrix<'a, 'tcx>(Vec<Vec<(&'a Pat, Option<Ty<'tcx>>)>>); |
| |
| /// Pretty-printer for matrices of patterns, example: |
| /// ++++++++++++++++++++++++++ |
| /// + _ + [] + |
| /// ++++++++++++++++++++++++++ |
| /// + true + [First] + |
| /// ++++++++++++++++++++++++++ |
| /// + true + [Second(true)] + |
| /// ++++++++++++++++++++++++++ |
| /// + false + [_] + |
| /// ++++++++++++++++++++++++++ |
| /// + _ + [_, _, ..tail] + |
| /// ++++++++++++++++++++++++++ |
| impl<'a, 'tcx> fmt::Debug for Matrix<'a, 'tcx> { |
| fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { |
| write!(f, "\n")?; |
| |
| let &Matrix(ref m) = self; |
| let pretty_printed_matrix: Vec<Vec<String>> = m.iter().map(|row| { |
| row.iter() |
| .map(|&(pat,ty)| format!("{}: {:?}", pat_to_string(&pat), ty)) |
| .collect::<Vec<String>>() |
| }).collect(); |
| |
| let column_count = m.iter().map(|row| row.len()).max().unwrap_or(0); |
| assert!(m.iter().all(|row| row.len() == column_count)); |
| let column_widths: Vec<usize> = (0..column_count).map(|col| { |
| pretty_printed_matrix.iter().map(|row| row[col].len()).max().unwrap_or(0) |
| }).collect(); |
| |
| let total_width = column_widths.iter().cloned().sum::<usize>() + column_count * 3 + 1; |
| let br = repeat('+').take(total_width).collect::<String>(); |
| write!(f, "{}\n", br)?; |
| for row in pretty_printed_matrix { |
| write!(f, "+")?; |
| for (column, pat_str) in row.into_iter().enumerate() { |
| write!(f, " ")?; |
| write!(f, "{:1$}", pat_str, column_widths[column])?; |
| write!(f, " +")?; |
| } |
| write!(f, "\n")?; |
| write!(f, "{}\n", br)?; |
| } |
| Ok(()) |
| } |
| } |
| |
| impl<'a, 'tcx> FromIterator<Vec<(&'a Pat, Option<Ty<'tcx>>)>> for Matrix<'a, 'tcx> { |
| fn from_iter<T: IntoIterator<Item=Vec<(&'a Pat, Option<Ty<'tcx>>)>>>(iter: T) |
| -> Self |
| { |
| Matrix(iter.into_iter().collect()) |
| } |
| } |
| |
| //NOTE: appears to be the only place other then InferCtxt to contain a ParamEnv |
| pub struct MatchCheckCtxt<'a, 'tcx: 'a> { |
| pub tcx: TyCtxt<'a, 'tcx, 'tcx>, |
| pub param_env: ParameterEnvironment<'tcx>, |
| } |
| |
| #[derive(Clone, Debug, PartialEq)] |
| pub enum Constructor { |
| /// The constructor of all patterns that don't vary by constructor, |
| /// e.g. struct patterns and fixed-length arrays. |
| Single, |
| /// Enum variants. |
| Variant(DefId), |
| /// Literal values. |
| ConstantValue(ConstVal), |
| /// Ranges of literal values (2..5). |
| ConstantRange(ConstVal, ConstVal), |
| /// Array patterns of length n. |
| Slice(usize), |
| /// Array patterns with a subslice. |
| SliceWithSubslice(usize, usize) |
| } |
| |
| #[derive(Clone, PartialEq)] |
| enum Usefulness { |
| Useful, |
| UsefulWithWitness(Vec<P<Pat>>), |
| NotUseful |
| } |
| |
| #[derive(Copy, Clone)] |
| enum WitnessPreference { |
| ConstructWitness, |
| LeaveOutWitness |
| } |
| |
| impl<'a, 'tcx, 'v> Visitor<'v> for MatchCheckCtxt<'a, 'tcx> { |
| fn visit_expr(&mut self, ex: &hir::Expr) { |
| check_expr(self, ex); |
| } |
| fn visit_local(&mut self, l: &hir::Local) { |
| check_local(self, l); |
| } |
| fn visit_fn(&mut self, fk: FnKind<'v>, fd: &'v hir::FnDecl, |
| b: &'v hir::Block, s: Span, n: NodeId) { |
| check_fn(self, fk, fd, b, s, n); |
| } |
| } |
| |
| pub fn check_crate<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) { |
| tcx.visit_all_items_in_krate(DepNode::MatchCheck, &mut MatchCheckCtxt { |
| tcx: tcx, |
| param_env: tcx.empty_parameter_environment(), |
| }); |
| tcx.sess.abort_if_errors(); |
| } |
| |
| fn check_expr(cx: &mut MatchCheckCtxt, ex: &hir::Expr) { |
| intravisit::walk_expr(cx, ex); |
| match ex.node { |
| hir::ExprMatch(ref scrut, ref arms, source) => { |
| for arm in arms { |
| // First, check legality of move bindings. |
| check_legality_of_move_bindings(cx, |
| 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(cx, &guard); |
| } |
| } |
| |
| let mut static_inliner = StaticInliner::new(cx.tcx, None); |
| let inlined_arms = arms.iter().map(|arm| { |
| (arm.pats.iter().map(|pat| { |
| static_inliner.fold_pat((*pat).clone()) |
| }).collect(), arm.guard.as_ref().map(|e| &**e)) |
| }).collect::<Vec<(Vec<P<Pat>>, Option<&hir::Expr>)>>(); |
| |
| // Bail out early if inlining failed. |
| if static_inliner.failed { |
| return; |
| } |
| |
| for pat in inlined_arms |
| .iter() |
| .flat_map(|&(ref pats, _)| pats) { |
| // Third, check legality of move bindings. |
| check_legality_of_bindings_in_at_patterns(cx, &pat); |
| |
| // Fourth, check if there are any references to NaN that we should warn about. |
| check_for_static_nan(cx, &pat); |
| |
| // Fifth, check if for any of the patterns that match an enumerated type |
| // are bindings with the same name as one of the variants of said type. |
| check_for_bindings_named_the_same_as_variants(cx, &pat); |
| } |
| |
| // Fourth, check for unreachable arms. |
| check_arms(cx, &inlined_arms[..], source); |
| |
| // Finally, check if the whole match expression is exhaustive. |
| // Check for empty enum, because is_useful only works on inhabited types. |
| let pat_ty = cx.tcx.node_id_to_type(scrut.id); |
| if inlined_arms.is_empty() { |
| if !pat_ty.is_empty(cx.tcx) { |
| // We know the type is inhabited, so this must be wrong |
| let mut err = struct_span_err!(cx.tcx.sess, ex.span, E0002, |
| "non-exhaustive patterns: type {} is non-empty", |
| pat_ty); |
| span_help!(&mut err, ex.span, |
| "Please ensure that all possible cases are being handled; \ |
| possibly adding wildcards or more match arms."); |
| err.emit(); |
| } |
| // If the type *is* empty, it's vacuously exhaustive |
| return; |
| } |
| |
| let matrix: Matrix = inlined_arms |
| .iter() |
| .filter(|&&(_, guard)| guard.is_none()) |
| .flat_map(|arm| &arm.0) |
| .map(|pat| vec![wrap_pat(cx, &pat)]) |
| .collect(); |
| check_exhaustive(cx, ex.span, &matrix, source); |
| }, |
| _ => () |
| } |
| } |
| |
| fn check_for_bindings_named_the_same_as_variants(cx: &MatchCheckCtxt, pat: &Pat) { |
| pat.walk(|p| { |
| if let PatKind::Binding(hir::BindByValue(hir::MutImmutable), name, None) = p.node { |
| let pat_ty = cx.tcx.pat_ty(p); |
| if let ty::TyEnum(edef, _) = pat_ty.sty { |
| if let Def::Local(..) = cx.tcx.expect_def(p.id) { |
| if edef.variants.iter().any(|variant| { |
| variant.name == name.node && variant.kind == VariantKind::Unit |
| }) { |
| 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 |
| }); |
| } |
| |
| // Check that we do not match against a static NaN (#6804) |
| fn check_for_static_nan(cx: &MatchCheckCtxt, pat: &Pat) { |
| pat.walk(|p| { |
| if let PatKind::Lit(ref expr) = p.node { |
| match eval_const_expr_partial(cx.tcx, &expr, ExprTypeChecked, None) { |
| Ok(ConstVal::Float(f)) if f.is_nan() => { |
| span_warn!(cx.tcx.sess, p.span, E0003, |
| "unmatchable NaN in pattern, \ |
| use the is_nan method in a guard instead"); |
| } |
| Ok(_) => {} |
| |
| Err(err) => { |
| report_const_eval_err(cx.tcx, &err, p.span, "pattern").emit(); |
| } |
| } |
| } |
| true |
| }); |
| } |
| |
| // Check for unreachable patterns |
| fn check_arms(cx: &MatchCheckCtxt, |
| arms: &[(Vec<P<Pat>>, Option<&hir::Expr>)], |
| source: hir::MatchSource) { |
| let mut seen = Matrix(vec![]); |
| let mut printed_if_let_err = false; |
| for &(ref pats, guard) in arms { |
| for pat in pats { |
| let v = vec![wrap_pat(cx, &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.span; |
| span_err!(cx.tcx.sess, span, E0162, "irrefutable if-let pattern"); |
| 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.span; |
| span_err!(cx.tcx.sess, span, E0165, "irrefutable while-let pattern"); |
| }, |
| |
| hir::MatchSource::ForLoopDesugar => { |
| // this is a bug, because on `match iter.next()` we cover |
| // `Some(<head>)` and `None`. It's impossible to have an unreachable |
| // pattern |
| // (see libsyntax/ext/expand.rs for the full expansion of a for loop) |
| span_bug!(pat.span, "unreachable for-loop pattern") |
| }, |
| |
| hir::MatchSource::Normal => { |
| let mut err = struct_span_err!(cx.tcx.sess, pat.span, E0001, |
| "unreachable pattern"); |
| // if we had a catchall pattern, hint at that |
| for row in &seen.0 { |
| if pat_is_catchall(&cx.tcx.def_map.borrow(), row[0].0) { |
| span_note!(err, row[0].0.span, |
| "this pattern matches any value"); |
| } |
| } |
| err.emit(); |
| }, |
| |
| hir::MatchSource::TryDesugar => { |
| span_bug!(pat.span, "unreachable try pattern") |
| }, |
| } |
| } |
| Useful => (), |
| UsefulWithWitness(_) => bug!() |
| } |
| if guard.is_none() { |
| let Matrix(mut rows) = seen; |
| rows.push(v); |
| seen = Matrix(rows); |
| } |
| } |
| } |
| } |
| |
| /// Checks for common cases of "catchall" patterns that may not be intended as such. |
| fn pat_is_catchall(dm: &DefMap, p: &Pat) -> bool { |
| match p.node { |
| PatKind::Binding(_, _, None) => true, |
| PatKind::Binding(_, _, Some(ref s)) => pat_is_catchall(dm, &s), |
| PatKind::Ref(ref s, _) => pat_is_catchall(dm, &s), |
| PatKind::Tuple(ref v, _) => v.iter().all(|p| pat_is_catchall(dm, &p)), |
| _ => false |
| } |
| } |
| |
| fn raw_pat(p: &Pat) -> &Pat { |
| match p.node { |
| PatKind::Binding(_, _, Some(ref s)) => raw_pat(&s), |
| _ => p |
| } |
| } |
| |
| fn check_exhaustive<'a, 'tcx>(cx: &MatchCheckCtxt<'a, 'tcx>, |
| sp: Span, |
| matrix: &Matrix<'a, 'tcx>, |
| source: hir::MatchSource) { |
| match is_useful(cx, matrix, &[(DUMMY_WILD_PAT, None)], ConstructWitness) { |
| UsefulWithWitness(pats) => { |
| let witnesses = if pats.is_empty() { |
| vec![DUMMY_WILD_PAT] |
| } else { |
| pats.iter().map(|w| &**w).collect() |
| }; |
| match source { |
| hir::MatchSource::ForLoopDesugar => { |
| // `witnesses[0]` has the form `Some(<head>)`, peel off the `Some` |
| let witness = match witnesses[0].node { |
| PatKind::TupleStruct(_, ref pats, _) => match &pats[..] { |
| &[ref pat] => &**pat, |
| _ => bug!(), |
| }, |
| _ => bug!(), |
| }; |
| span_err!(cx.tcx.sess, sp, E0297, |
| "refutable pattern in `for` loop binding: \ |
| `{}` not covered", |
| pat_to_string(witness)); |
| }, |
| _ => { |
| let pattern_strings: Vec<_> = witnesses.iter().map(|w| { |
| pat_to_string(w) |
| }).collect(); |
| const LIMIT: usize = 3; |
| let joined_patterns = match pattern_strings.len() { |
| 0 => bug!(), |
| 1 => format!("`{}`", pattern_strings[0]), |
| 2...LIMIT => { |
| let (tail, head) = pattern_strings.split_last().unwrap(); |
| format!("`{}`", head.join("`, `") + "` and `" + tail) |
| }, |
| _ => { |
| let (head, tail) = pattern_strings.split_at(LIMIT); |
| format!("`{}` and {} more", head.join("`, `"), tail.len()) |
| } |
| }; |
| span_err!(cx.tcx.sess, sp, E0004, |
| "non-exhaustive patterns: {} not covered", |
| joined_patterns |
| ); |
| }, |
| } |
| } |
| NotUseful => { |
| // This is good, wildcard pattern isn't reachable |
| }, |
| _ => bug!() |
| } |
| } |
| |
| fn const_val_to_expr(value: &ConstVal) -> P<hir::Expr> { |
| let node = match value { |
| &ConstVal::Bool(b) => ast::LitKind::Bool(b), |
| _ => bug!() |
| }; |
| P(hir::Expr { |
| id: 0, |
| node: hir::ExprLit(P(Spanned { node: node, span: DUMMY_SP })), |
| span: DUMMY_SP, |
| attrs: ast::ThinVec::new(), |
| }) |
| } |
| |
| pub struct StaticInliner<'a, 'tcx: 'a> { |
| pub tcx: TyCtxt<'a, 'tcx, 'tcx>, |
| pub failed: bool, |
| pub renaming_map: Option<&'a mut FnvHashMap<(NodeId, Span), NodeId>>, |
| } |
| |
| impl<'a, 'tcx> StaticInliner<'a, 'tcx> { |
| pub fn new<'b>(tcx: TyCtxt<'b, 'tcx, 'tcx>, |
| renaming_map: Option<&'b mut FnvHashMap<(NodeId, Span), NodeId>>) |
| -> StaticInliner<'b, 'tcx> { |
| StaticInliner { |
| tcx: tcx, |
| failed: false, |
| renaming_map: renaming_map |
| } |
| } |
| } |
| |
| struct RenamingRecorder<'map> { |
| substituted_node_id: NodeId, |
| origin_span: Span, |
| renaming_map: &'map mut FnvHashMap<(NodeId, Span), NodeId> |
| } |
| |
| impl<'v, 'map> Visitor<'v> for RenamingRecorder<'map> { |
| fn visit_id(&mut self, node_id: NodeId) { |
| let key = (node_id, self.origin_span); |
| self.renaming_map.insert(key, self.substituted_node_id); |
| } |
| } |
| |
| impl<'a, 'tcx> Folder for StaticInliner<'a, 'tcx> { |
| fn fold_pat(&mut self, pat: P<Pat>) -> P<Pat> { |
| return match pat.node { |
| PatKind::Path(..) => { |
| match self.tcx.expect_def(pat.id) { |
| Def::AssociatedConst(did) | Def::Const(did) => { |
| let substs = Some(self.tcx.node_id_item_substs(pat.id).substs); |
| if let Some((const_expr, _)) = lookup_const_by_id(self.tcx, did, substs) { |
| match const_expr_to_pat(self.tcx, const_expr, pat.id, pat.span) { |
| Ok(new_pat) => { |
| if let Some(ref mut map) = self.renaming_map { |
| // Record any renamings we do here |
| record_renamings(const_expr, &pat, map); |
| } |
| new_pat |
| } |
| Err(def_id) => { |
| self.failed = true; |
| self.tcx.sess.span_err( |
| pat.span, |
| &format!("constants of the type `{}` \ |
| cannot be used in patterns", |
| self.tcx.item_path_str(def_id))); |
| pat |
| } |
| } |
| } else { |
| self.failed = true; |
| span_err!(self.tcx.sess, pat.span, E0158, |
| "statics cannot be referenced in patterns"); |
| pat |
| } |
| } |
| _ => noop_fold_pat(pat, self) |
| } |
| } |
| _ => noop_fold_pat(pat, self) |
| }; |
| |
| fn record_renamings(const_expr: &hir::Expr, |
| substituted_pat: &hir::Pat, |
| renaming_map: &mut FnvHashMap<(NodeId, Span), NodeId>) { |
| let mut renaming_recorder = RenamingRecorder { |
| substituted_node_id: substituted_pat.id, |
| origin_span: substituted_pat.span, |
| renaming_map: renaming_map, |
| }; |
| |
| renaming_recorder.visit_expr(const_expr); |
| } |
| } |
| } |
| |
| /// Constructs a partial witness for a pattern given a list of |
| /// patterns expanded by the specialization step. |
| /// |
| /// When a pattern P is discovered to be useful, this function is used bottom-up |
| /// to reconstruct a complete witness, e.g. a pattern P' that covers a subset |
| /// of values, V, where each value in that set is not covered by any previously |
| /// used patterns and is covered by the pattern P'. Examples: |
| /// |
| /// left_ty: tuple of 3 elements |
| /// pats: [10, 20, _] => (10, 20, _) |
| /// |
| /// left_ty: struct X { a: (bool, &'static str), b: usize} |
| /// pats: [(false, "foo"), 42] => X { a: (false, "foo"), b: 42 } |
| fn construct_witness<'a,'tcx>(cx: &MatchCheckCtxt<'a,'tcx>, ctor: &Constructor, |
| pats: Vec<&Pat>, left_ty: Ty<'tcx>) -> P<Pat> { |
| let pats_len = pats.len(); |
| let mut pats = pats.into_iter().map(|p| P((*p).clone())); |
| let pat = match left_ty.sty { |
| ty::TyTuple(..) => PatKind::Tuple(pats.collect(), None), |
| |
| ty::TyEnum(adt, _) | ty::TyStruct(adt, _) => { |
| let v = ctor.variant_for_adt(adt); |
| match v.kind { |
| VariantKind::Struct => { |
| let field_pats: hir::HirVec<_> = v.fields.iter() |
| .zip(pats) |
| .filter(|&(_, ref pat)| pat.node != PatKind::Wild) |
| .map(|(field, pat)| Spanned { |
| span: DUMMY_SP, |
| node: hir::FieldPat { |
| name: field.name, |
| pat: pat, |
| is_shorthand: false, |
| } |
| }).collect(); |
| let has_more_fields = field_pats.len() < pats_len; |
| PatKind::Struct(def_to_path(cx.tcx, v.did), field_pats, has_more_fields) |
| } |
| VariantKind::Tuple => { |
| PatKind::TupleStruct(def_to_path(cx.tcx, v.did), pats.collect(), None) |
| } |
| VariantKind::Unit => { |
| PatKind::Path(None, def_to_path(cx.tcx, v.did)) |
| } |
| } |
| } |
| |
| ty::TyRef(_, ty::TypeAndMut { mutbl, .. }) => { |
| assert_eq!(pats_len, 1); |
| PatKind::Ref(pats.nth(0).unwrap(), mutbl) |
| } |
| |
| ty::TySlice(_) => match ctor { |
| &Slice(n) => { |
| assert_eq!(pats_len, n); |
| PatKind::Vec(pats.collect(), None, hir::HirVec::new()) |
| }, |
| _ => unreachable!() |
| }, |
| |
| ty::TyArray(_, len) => { |
| assert_eq!(pats_len, len); |
| PatKind::Vec(pats.collect(), None, hir::HirVec::new()) |
| } |
| |
| _ => { |
| match *ctor { |
| ConstantValue(ref v) => PatKind::Lit(const_val_to_expr(v)), |
| _ => PatKind::Wild, |
| } |
| } |
| }; |
| |
| P(hir::Pat { |
| id: 0, |
| node: pat, |
| span: DUMMY_SP |
| }) |
| } |
| |
| impl Constructor { |
| fn variant_for_adt<'tcx, 'container, 'a>(&self, |
| adt: &'a ty::AdtDefData<'tcx, 'container>) |
| -> &'a VariantDefData<'tcx, 'container> { |
| match self { |
| &Variant(vid) => adt.variant_with_id(vid), |
| _ => adt.struct_variant() |
| } |
| } |
| } |
| |
| fn missing_constructors(cx: &MatchCheckCtxt, &Matrix(ref rows): &Matrix, |
| left_ty: Ty, max_slice_length: usize) -> Vec<Constructor> { |
| let used_constructors: Vec<Constructor> = rows.iter() |
| .flat_map(|row| pat_constructors(cx, row[0].0, left_ty, max_slice_length)) |
| .collect(); |
| all_constructors(cx, left_ty, max_slice_length) |
| .into_iter() |
| .filter(|c| !used_constructors.contains(c)) |
| .collect() |
| } |
| |
| /// This determines the set of all possible constructors of a pattern matching |
| /// values of type `left_ty`. For vectors, this would normally be an infinite set |
| /// but is instead bounded by the maximum fixed length of slice patterns in |
| /// the column of patterns being analyzed. |
| fn all_constructors(_cx: &MatchCheckCtxt, left_ty: Ty, |
| max_slice_length: usize) -> Vec<Constructor> { |
| match left_ty.sty { |
| ty::TyBool => |
| [true, false].iter().map(|b| ConstantValue(ConstVal::Bool(*b))).collect(), |
| ty::TySlice(_) => |
| (0..max_slice_length+1).map(|length| Slice(length)).collect(), |
| ty::TyEnum(def, _) => def.variants.iter().map(|v| Variant(v.did)).collect(), |
| _ => vec![Single] |
| } |
| } |
| |
| // Algorithm from http://moscova.inria.fr/~maranget/papers/warn/index.html |
| // |
| // Whether a vector `v` of patterns is 'useful' in relation to a set of such |
| // vectors `m` is defined as there being a set of inputs that will match `v` |
| // but not any of the sets in `m`. |
| // |
| // This is used both for reachability checking (if a pattern isn't useful in |
| // relation to preceding patterns, it is not reachable) and exhaustiveness |
| // checking (if a wildcard pattern is useful in relation to a matrix, the |
| // matrix isn't exhaustive). |
| |
| // Note: is_useful doesn't work on empty types, as the paper notes. |
| // So it assumes that v is non-empty. |
| fn is_useful<'a, 'tcx>(cx: &MatchCheckCtxt<'a, 'tcx>, |
| matrix: &Matrix<'a, 'tcx>, |
| v: &[(&Pat, Option<Ty<'tcx>>)], |
| witness: WitnessPreference) |
| -> Usefulness { |
| let &Matrix(ref rows) = matrix; |
| debug!("is_useful({:?}, {:?})", matrix, v); |
| if rows.is_empty() { |
| return match witness { |
| ConstructWitness => UsefulWithWitness(vec!()), |
| LeaveOutWitness => Useful |
| }; |
| } |
| if rows[0].is_empty() { |
| return NotUseful; |
| } |
| assert!(rows.iter().all(|r| r.len() == v.len())); |
| let left_ty = match rows.iter().filter_map(|r| r[0].1).next().or_else(|| v[0].1) { |
| Some(ty) => ty, |
| None => { |
| // all patterns are wildcards - we can pick any type we want |
| cx.tcx.types.bool |
| } |
| }; |
| |
| let max_slice_length = rows.iter().filter_map(|row| match row[0].0.node { |
| PatKind::Vec(ref before, _, ref after) => Some(before.len() + after.len()), |
| _ => None |
| }).max().map_or(0, |v| v + 1); |
| |
| let constructors = pat_constructors(cx, v[0].0, left_ty, max_slice_length); |
| debug!("is_useful - pat_constructors = {:?} left_ty = {:?}", constructors, |
| left_ty); |
| if constructors.is_empty() { |
| let constructors = missing_constructors(cx, matrix, left_ty, max_slice_length); |
| debug!("is_useful - missing_constructors = {:?}", constructors); |
| if constructors.is_empty() { |
| all_constructors(cx, left_ty, max_slice_length).into_iter().map(|c| { |
| match is_useful_specialized(cx, matrix, v, c.clone(), left_ty, witness) { |
| UsefulWithWitness(pats) => UsefulWithWitness({ |
| let arity = constructor_arity(cx, &c, left_ty); |
| let mut result = { |
| let pat_slice = &pats[..]; |
| let subpats: Vec<_> = (0..arity).map(|i| { |
| pat_slice.get(i).map_or(DUMMY_WILD_PAT, |p| &**p) |
| }).collect(); |
| vec![construct_witness(cx, &c, subpats, left_ty)] |
| }; |
| result.extend(pats.into_iter().skip(arity)); |
| result |
| }), |
| result => result |
| } |
| }).find(|result| result != &NotUseful).unwrap_or(NotUseful) |
| } else { |
| let matrix = rows.iter().filter_map(|r| { |
| match raw_pat(r[0].0).node { |
| PatKind::Binding(..) | PatKind::Wild => Some(r[1..].to_vec()), |
| _ => None, |
| } |
| }).collect(); |
| match is_useful(cx, &matrix, &v[1..], witness) { |
| UsefulWithWitness(pats) => { |
| let mut new_pats: Vec<_> = constructors.into_iter().map(|constructor| { |
| let arity = constructor_arity(cx, &constructor, left_ty); |
| let wild_pats = vec![DUMMY_WILD_PAT; arity]; |
| construct_witness(cx, &constructor, wild_pats, left_ty) |
| }).collect(); |
| new_pats.extend(pats); |
| UsefulWithWitness(new_pats) |
| }, |
| result => result |
| } |
| } |
| } else { |
| constructors.into_iter().map(|c| |
| is_useful_specialized(cx, matrix, v, c.clone(), left_ty, witness) |
| ).find(|result| result != &NotUseful).unwrap_or(NotUseful) |
| } |
| } |
| |
| fn is_useful_specialized<'a, 'tcx>( |
| cx: &MatchCheckCtxt<'a, 'tcx>, |
| &Matrix(ref m): &Matrix<'a, 'tcx>, |
| v: &[(&Pat, Option<Ty<'tcx>>)], |
| ctor: Constructor, |
| lty: Ty<'tcx>, |
| witness: WitnessPreference) -> Usefulness |
| { |
| let arity = constructor_arity(cx, &ctor, lty); |
| let matrix = Matrix(m.iter().filter_map(|r| { |
| specialize(cx, &r[..], &ctor, 0, arity) |
| }).collect()); |
| match specialize(cx, v, &ctor, 0, arity) { |
| Some(v) => is_useful(cx, &matrix, &v[..], witness), |
| None => NotUseful |
| } |
| } |
| |
| /// Determines the constructors that the given pattern can be specialized to. |
| /// |
| /// In most cases, there's only one constructor that a specific pattern |
| /// represents, such as a specific enum variant or a specific literal value. |
| /// Slice patterns, however, can match slices of different lengths. For instance, |
| /// `[a, b, ..tail]` can match a slice of length 2, 3, 4 and so on. |
| /// |
| /// On the other hand, a wild pattern and an identifier pattern cannot be |
| /// specialized in any way. |
| fn pat_constructors(cx: &MatchCheckCtxt, p: &Pat, |
| left_ty: Ty, max_slice_length: usize) -> Vec<Constructor> { |
| let pat = raw_pat(p); |
| match pat.node { |
| PatKind::Struct(..) | PatKind::TupleStruct(..) | PatKind::Path(..) => |
| match cx.tcx.expect_def(pat.id) { |
| Def::Variant(_, id) => vec![Variant(id)], |
| Def::Struct(..) | Def::TyAlias(..) | Def::AssociatedTy(..) => vec![Single], |
| Def::Const(..) | Def::AssociatedConst(..) => |
| span_bug!(pat.span, "const pattern should've been rewritten"), |
| def => span_bug!(pat.span, "pat_constructors: unexpected definition {:?}", def), |
| }, |
| PatKind::Lit(ref expr) => |
| vec![ConstantValue(eval_const_expr(cx.tcx, &expr))], |
| PatKind::Range(ref lo, ref hi) => |
| vec![ConstantRange(eval_const_expr(cx.tcx, &lo), eval_const_expr(cx.tcx, &hi))], |
| PatKind::Vec(ref before, ref slice, ref after) => |
| match left_ty.sty { |
| ty::TyArray(_, _) => vec![Single], |
| ty::TySlice(_) if slice.is_some() => { |
| (before.len() + after.len()..max_slice_length+1) |
| .map(|length| Slice(length)) |
| .collect() |
| } |
| ty::TySlice(_) => vec!(Slice(before.len() + after.len())), |
| _ => span_bug!(pat.span, "pat_constructors: unexpected \ |
| slice pattern type {:?}", left_ty) |
| }, |
| PatKind::Box(..) | PatKind::Tuple(..) | PatKind::Ref(..) => |
| vec![Single], |
| PatKind::Binding(..) | PatKind::Wild => |
| vec![], |
| } |
| } |
| |
| /// This computes the arity of a constructor. The arity of a constructor |
| /// is how many subpattern patterns of that constructor should be expanded to. |
| /// |
| /// For instance, a tuple pattern (_, 42, Some([])) has the arity of 3. |
| /// A struct pattern's arity is the number of fields it contains, etc. |
| pub fn constructor_arity(_cx: &MatchCheckCtxt, ctor: &Constructor, ty: Ty) -> usize { |
| debug!("constructor_arity({:?}, {:?})", ctor, ty); |
| match ty.sty { |
| ty::TyTuple(ref fs) => fs.len(), |
| ty::TyBox(_) => 1, |
| ty::TySlice(_) => match *ctor { |
| Slice(length) => length, |
| ConstantValue(_) => 0, |
| _ => bug!() |
| }, |
| ty::TyRef(..) => 1, |
| ty::TyEnum(adt, _) | ty::TyStruct(adt, _) => { |
| ctor.variant_for_adt(adt).fields.len() |
| } |
| ty::TyArray(_, n) => n, |
| _ => 0 |
| } |
| } |
| |
| fn range_covered_by_constructor(tcx: TyCtxt, span: Span, |
| ctor: &Constructor, |
| from: &ConstVal, to: &ConstVal) |
| -> Result<bool, ErrorReported> { |
| let (c_from, c_to) = match *ctor { |
| ConstantValue(ref value) => (value, value), |
| ConstantRange(ref from, ref to) => (from, to), |
| Single => return Ok(true), |
| _ => bug!() |
| }; |
| let cmp_from = compare_const_vals(tcx, span, c_from, from)?; |
| let cmp_to = compare_const_vals(tcx, span, c_to, to)?; |
| Ok(cmp_from != Ordering::Less && cmp_to != Ordering::Greater) |
| } |
| |
| fn wrap_pat<'a, 'b, 'tcx>(cx: &MatchCheckCtxt<'b, 'tcx>, |
| pat: &'a Pat) |
| -> (&'a Pat, Option<Ty<'tcx>>) |
| { |
| let pat_ty = cx.tcx.pat_ty(pat); |
| (pat, Some(match pat.node { |
| PatKind::Binding(hir::BindByRef(..), _, _) => { |
| pat_ty.builtin_deref(false, NoPreference).unwrap().ty |
| } |
| _ => pat_ty |
| })) |
| } |
| |
| /// This is the main specialization step. It expands the first pattern in the given row |
| /// into `arity` patterns based on the constructor. For most patterns, the step is trivial, |
| /// for instance tuple patterns are flattened and box patterns expand into their inner pattern. |
| /// |
| /// OTOH, slice patterns with a subslice pattern (..tail) can be expanded into multiple |
| /// different patterns. |
| /// Structure patterns with a partial wild pattern (Foo { a: 42, .. }) have their missing |
| /// fields filled with wild patterns. |
| pub fn specialize<'a, 'b, 'tcx>( |
| cx: &MatchCheckCtxt<'b, 'tcx>, |
| r: &[(&'a Pat, Option<Ty<'tcx>>)], |
| constructor: &Constructor, col: usize, arity: usize) |
| -> Option<Vec<(&'a Pat, Option<Ty<'tcx>>)>> |
| { |
| let pat = raw_pat(r[col].0); |
| let &Pat { |
| id: pat_id, ref node, span: pat_span |
| } = pat; |
| let wpat = |pat: &'a Pat| wrap_pat(cx, pat); |
| let dummy_pat = (DUMMY_WILD_PAT, None); |
| |
| let head: Option<Vec<(&Pat, Option<Ty>)>> = match *node { |
| PatKind::Binding(..) | PatKind::Wild => |
| Some(vec![dummy_pat; arity]), |
| |
| PatKind::Path(..) => { |
| match cx.tcx.expect_def(pat_id) { |
| Def::Const(..) | Def::AssociatedConst(..) => |
| span_bug!(pat_span, "const pattern should've \ |
| been rewritten"), |
| Def::Variant(_, id) if *constructor != Variant(id) => None, |
| Def::Variant(..) | Def::Struct(..) => Some(Vec::new()), |
| def => span_bug!(pat_span, "specialize: unexpected \ |
| definition {:?}", def), |
| } |
| } |
| |
| PatKind::TupleStruct(_, ref args, ddpos) => { |
| match cx.tcx.expect_def(pat_id) { |
| Def::Const(..) | Def::AssociatedConst(..) => |
| span_bug!(pat_span, "const pattern should've \ |
| been rewritten"), |
| Def::Variant(_, id) if *constructor != Variant(id) => None, |
| Def::Variant(..) | Def::Struct(..) => { |
| match ddpos { |
| Some(ddpos) => { |
| let mut pats: Vec<_> = args[..ddpos].iter().map(|p| { |
| wpat(p) |
| }).collect(); |
| pats.extend(repeat((DUMMY_WILD_PAT, None)).take(arity - args.len())); |
| pats.extend(args[ddpos..].iter().map(|p| wpat(p))); |
| Some(pats) |
| } |
| None => Some(args.iter().map(|p| wpat(p)).collect()) |
| } |
| } |
| _ => None |
| } |
| } |
| |
| PatKind::Struct(_, ref pattern_fields, _) => { |
| let adt = cx.tcx.node_id_to_type(pat_id).ty_adt_def().unwrap(); |
| let variant = constructor.variant_for_adt(adt); |
| let def_variant = adt.variant_of_def(cx.tcx.expect_def(pat_id)); |
| if variant.did == def_variant.did { |
| Some(variant.fields.iter().map(|sf| { |
| match pattern_fields.iter().find(|f| f.node.name == sf.name) { |
| Some(ref f) => wpat(&f.node.pat), |
| _ => dummy_pat |
| } |
| }).collect()) |
| } else { |
| None |
| } |
| } |
| |
| PatKind::Tuple(ref args, Some(ddpos)) => { |
| let mut pats: Vec<_> = args[..ddpos].iter().map(|p| wpat(p)).collect(); |
| pats.extend(repeat(dummy_pat).take(arity - args.len())); |
| pats.extend(args[ddpos..].iter().map(|p| wpat(p))); |
| Some(pats) |
| } |
| PatKind::Tuple(ref args, None) => |
| Some(args.iter().map(|p| wpat(&**p)).collect()), |
| |
| PatKind::Box(ref inner) | PatKind::Ref(ref inner, _) => |
| Some(vec![wpat(&**inner)]), |
| |
| PatKind::Lit(ref expr) => { |
| if let Some(&ty::TyS { sty: ty::TyRef(_, mt), .. }) = r[col].1 { |
| // HACK: handle string literals. A string literal pattern |
| // serves both as an unary reference pattern and as a |
| // nullary value pattern, depending on the type. |
| Some(vec![(pat, Some(mt.ty))]) |
| } else { |
| let expr_value = eval_const_expr(cx.tcx, &expr); |
| match range_covered_by_constructor( |
| cx.tcx, expr.span, constructor, &expr_value, &expr_value |
| ) { |
| Ok(true) => Some(vec![]), |
| Ok(false) => None, |
| Err(ErrorReported) => None, |
| } |
| } |
| } |
| |
| PatKind::Range(ref from, ref to) => { |
| let from_value = eval_const_expr(cx.tcx, &from); |
| let to_value = eval_const_expr(cx.tcx, &to); |
| match range_covered_by_constructor( |
| cx.tcx, pat_span, constructor, &from_value, &to_value |
| ) { |
| Ok(true) => Some(vec![]), |
| Ok(false) => None, |
| Err(ErrorReported) => None, |
| } |
| } |
| |
| PatKind::Vec(ref before, ref slice, ref after) => { |
| let pat_len = before.len() + after.len(); |
| match *constructor { |
| Single => { |
| // Fixed-length vectors. |
| Some( |
| before.iter().map(|p| wpat(p)).chain( |
| repeat(dummy_pat).take(arity - pat_len).chain( |
| after.iter().map(|p| wpat(p)) |
| )).collect()) |
| }, |
| Slice(length) if pat_len <= length && slice.is_some() => { |
| Some( |
| before.iter().map(|p| wpat(p)).chain( |
| repeat(dummy_pat).take(arity - pat_len).chain( |
| after.iter().map(|p| wpat(p)) |
| )).collect()) |
| } |
| Slice(length) if pat_len == length => { |
| Some( |
| before.iter().map(|p| wpat(p)).chain( |
| after.iter().map(|p| wpat(p)) |
| ).collect()) |
| } |
| SliceWithSubslice(prefix, suffix) |
| if before.len() == prefix |
| && after.len() == suffix |
| && slice.is_some() => { |
| // this is used by trans::_match only |
| let mut pats: Vec<_> = before.iter() |
| .map(|p| (&**p, None)).collect(); |
| pats.extend(after.iter().map(|p| (&**p, None))); |
| Some(pats) |
| } |
| _ => None |
| } |
| } |
| }; |
| debug!("specialize({:?}, {:?}) = {:?}", r[col], arity, head); |
| |
| head.map(|mut head| { |
| head.extend_from_slice(&r[..col]); |
| head.extend_from_slice(&r[col + 1..]); |
| head |
| }) |
| } |
| |
| fn check_local(cx: &mut MatchCheckCtxt, loc: &hir::Local) { |
| intravisit::walk_local(cx, loc); |
| |
| let pat = StaticInliner::new(cx.tcx, None).fold_pat(loc.pat.clone()); |
| check_irrefutable(cx, &pat, false); |
| |
| // Check legality of move bindings and `@` patterns. |
| check_legality_of_move_bindings(cx, false, slice::ref_slice(&loc.pat)); |
| check_legality_of_bindings_in_at_patterns(cx, &loc.pat); |
| } |
| |
| fn check_fn(cx: &mut MatchCheckCtxt, |
| kind: FnKind, |
| decl: &hir::FnDecl, |
| body: &hir::Block, |
| sp: Span, |
| fn_id: NodeId) { |
| match kind { |
| FnKind::Closure(_) => {} |
| _ => cx.param_env = ParameterEnvironment::for_item(cx.tcx, fn_id), |
| } |
| |
| intravisit::walk_fn(cx, kind, decl, body, sp, fn_id); |
| |
| for input in &decl.inputs { |
| check_irrefutable(cx, &input.pat, true); |
| check_legality_of_move_bindings(cx, false, slice::ref_slice(&input.pat)); |
| check_legality_of_bindings_in_at_patterns(cx, &input.pat); |
| } |
| } |
| |
| fn check_irrefutable(cx: &MatchCheckCtxt, pat: &Pat, is_fn_arg: bool) { |
| let origin = if is_fn_arg { |
| "function argument" |
| } else { |
| "local binding" |
| }; |
| |
| is_refutable(cx, pat, |uncovered_pat| { |
| span_err!(cx.tcx.sess, pat.span, E0005, |
| "refutable pattern in {}: `{}` not covered", |
| origin, |
| pat_to_string(uncovered_pat), |
| ); |
| }); |
| } |
| |
| fn is_refutable<A, F>(cx: &MatchCheckCtxt, pat: &Pat, refutable: F) -> Option<A> where |
| F: FnOnce(&Pat) -> A, |
| { |
| let pats = Matrix(vec!(vec!(wrap_pat(cx, pat)))); |
| match is_useful(cx, &pats, &[(DUMMY_WILD_PAT, None)], ConstructWitness) { |
| UsefulWithWitness(pats) => Some(refutable(&pats[0])), |
| NotUseful => None, |
| Useful => bug!() |
| } |
| } |
| |
| // Legality of move bindings checking |
| fn check_legality_of_move_bindings(cx: &MatchCheckCtxt, |
| has_guard: bool, |
| pats: &[P<Pat>]) { |
| let mut by_ref_span = None; |
| for pat in pats { |
| pat_bindings(&pat, |bm, _, span, _path| { |
| if let hir::BindByRef(..) = 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| pat_contains_bindings(&p)) { |
| span_err!(cx.tcx.sess, p.span, E0007, "cannot bind by-move with sub-bindings"); |
| } else if has_guard { |
| span_err!(cx.tcx.sess, p.span, E0008, "cannot bind by-move into a pattern guard"); |
| } else if by_ref_span.is_some() { |
| let mut err = struct_span_err!(cx.tcx.sess, p.span, E0009, |
| "cannot bind by-move and by-ref in the same pattern"); |
| span_note!(&mut err, by_ref_span.unwrap(), "by-ref binding occurs here"); |
| err.emit(); |
| } |
| }; |
| |
| for pat in pats { |
| pat.walk(|p| { |
| if let PatKind::Binding(hir::BindByValue(..), _, ref sub) = p.node { |
| let pat_ty = cx.tcx.node_id_to_type(p.id); |
| //FIXME: (@jroesch) this code should be floated up as well |
| cx.tcx.infer_ctxt(None, Some(cx.param_env.clone()), |
| ProjectionMode::AnyFinal).enter(|infcx| { |
| if infcx.type_moves_by_default(pat_ty, 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. |
| fn check_for_mutation_in_guard<'a, 'tcx>(cx: &'a MatchCheckCtxt<'a, 'tcx>, |
| guard: &hir::Expr) { |
| cx.tcx.infer_ctxt(None, Some(cx.param_env.clone()), |
| ProjectionMode::AnyFinal).enter(|infcx| { |
| let mut checker = MutationChecker { |
| cx: cx, |
| }; |
| let mut visitor = ExprUseVisitor::new(&mut checker, &infcx); |
| visitor.walk_expr(guard); |
| }); |
| } |
| |
| struct MutationChecker<'a, 'gcx: 'a> { |
| cx: &'a MatchCheckCtxt<'a, 'gcx>, |
| } |
| |
| impl<'a, 'gcx, 'tcx> Delegate<'tcx> for MutationChecker<'a, 'gcx> { |
| fn matched_pat(&mut self, _: &Pat, _: cmt, _: euv::MatchMode) {} |
| fn consume(&mut self, _: NodeId, _: Span, _: cmt, _: ConsumeMode) {} |
| fn consume_pat(&mut self, _: &Pat, _: cmt, _: ConsumeMode) {} |
| fn borrow(&mut self, |
| _: NodeId, |
| span: Span, |
| _: cmt, |
| _: Region, |
| kind: BorrowKind, |
| _: LoanCause) { |
| match kind { |
| MutBorrow => { |
| span_err!(self.cx.tcx.sess, span, E0301, |
| "cannot mutably borrow in a pattern guard") |
| } |
| ImmBorrow | UniqueImmBorrow => {} |
| } |
| } |
| fn decl_without_init(&mut self, _: NodeId, _: Span) {} |
| fn mutate(&mut self, _: NodeId, span: Span, _: cmt, mode: MutateMode) { |
| match mode { |
| MutateMode::JustWrite | MutateMode::WriteAndRead => { |
| span_err!(self.cx.tcx.sess, span, E0302, "cannot assign in a pattern guard") |
| } |
| 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: &MatchCheckCtxt, pat: &Pat) { |
| AtBindingPatternVisitor { cx: cx, bindings_allowed: true }.visit_pat(pat); |
| } |
| |
| struct AtBindingPatternVisitor<'a, 'b:'a, 'tcx:'b> { |
| cx: &'a MatchCheckCtxt<'b, 'tcx>, |
| bindings_allowed: bool |
| } |
| |
| impl<'a, 'b, 'tcx, 'v> Visitor<'v> for AtBindingPatternVisitor<'a, 'b, 'tcx> { |
| fn visit_pat(&mut self, pat: &Pat) { |
| match pat.node { |
| PatKind::Binding(_, _, ref subpat) => { |
| if !self.bindings_allowed { |
| span_err!(self.cx.tcx.sess, pat.span, E0303, |
| "pattern bindings are not allowed after an `@`"); |
| } |
| |
| 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), |
| } |
| } |
| } |
