| // Copyright 2012-2014 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. |
| |
| pub use self::Constructor::*; |
| use self::Usefulness::*; |
| use self::WitnessPreference::*; |
| |
| use dep_graph::DepNode; |
| use middle::const_eval::{compare_const_vals, ConstVal}; |
| use middle::const_eval::{eval_const_expr, eval_const_expr_partial}; |
| use middle::const_eval::{const_expr_to_pat, lookup_const_by_id}; |
| use middle::const_eval::EvalHint::ExprTypeChecked; |
| use middle::def::*; |
| use middle::def_id::{DefId}; |
| use middle::expr_use_visitor::{ConsumeMode, Delegate, ExprUseVisitor}; |
| use middle::expr_use_visitor::{LoanCause, MutateMode}; |
| use middle::expr_use_visitor as euv; |
| use middle::infer; |
| use middle::mem_categorization::{cmt}; |
| use middle::pat_util::*; |
| use middle::ty::*; |
| use middle::ty; |
| use std::cmp::Ordering; |
| use std::fmt; |
| use std::iter::{FromIterator, IntoIterator, repeat}; |
| |
| use rustc_front::hir; |
| use rustc_front::hir::Pat; |
| use rustc_front::intravisit::{self, Visitor, FnKind}; |
| use rustc_front::util as front_util; |
| use rustc_back::slice; |
| |
| use syntax::ast::{self, DUMMY_NODE_ID, NodeId}; |
| use syntax::ast_util; |
| use syntax::codemap::{Span, Spanned, DUMMY_SP}; |
| use rustc_front::fold::{Folder, noop_fold_pat}; |
| use rustc_front::print::pprust::pat_to_string; |
| use syntax::ptr::P; |
| use util::nodemap::FnvHashMap; |
| |
| pub const DUMMY_WILD_PAT: &'static Pat = &Pat { |
| id: DUMMY_NODE_ID, |
| node: hir::PatWild, |
| span: DUMMY_SP |
| }; |
| |
| struct Matrix<'a>(Vec<Vec<&'a Pat>>); |
| |
| /// Pretty-printer for matrices of patterns, example: |
| /// ++++++++++++++++++++++++++ |
| /// + _ + [] + |
| /// ++++++++++++++++++++++++++ |
| /// + true + [First] + |
| /// ++++++++++++++++++++++++++ |
| /// + true + [Second(true)] + |
| /// ++++++++++++++++++++++++++ |
| /// + false + [_] + |
| /// ++++++++++++++++++++++++++ |
| /// + _ + [_, _, ..tail] + |
| /// ++++++++++++++++++++++++++ |
| impl<'a> fmt::Debug for Matrix<'a> { |
| fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { |
| try!(write!(f, "\n")); |
| |
| let &Matrix(ref m) = self; |
| let pretty_printed_matrix: Vec<Vec<String>> = m.iter().map(|row| { |
| row.iter() |
| .map(|&pat| pat_to_string(&*pat)) |
| .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>(); |
| try!(write!(f, "{}\n", br)); |
| for row in pretty_printed_matrix { |
| try!(write!(f, "+")); |
| for (column, pat_str) in row.into_iter().enumerate() { |
| try!(write!(f, " ")); |
| try!(write!(f, "{:1$}", pat_str, column_widths[column])); |
| try!(write!(f, " +")); |
| } |
| try!(write!(f, "\n")); |
| try!(write!(f, "{}\n", br)); |
| } |
| Ok(()) |
| } |
| } |
| |
| impl<'a> FromIterator<Vec<&'a Pat>> for Matrix<'a> { |
| fn from_iter<T: IntoIterator<Item=Vec<&'a Pat>>>(iter: T) -> Matrix<'a> { |
| 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: &'a ty::ctxt<'tcx>, |
| pub param_env: ParameterEnvironment<'a, 'tcx>, |
| } |
| |
| #[derive(Clone, 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(tcx: &ty::ctxt) { |
| 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. |
| match arm.guard { |
| Some(ref guard) => check_for_mutation_in_guard(cx, &**guard), |
| None => {} |
| } |
| } |
| |
| 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![&**pat]) |
| .collect(); |
| check_exhaustive(cx, ex.span, &matrix, source); |
| }, |
| _ => () |
| } |
| } |
| |
| fn check_for_bindings_named_the_same_as_variants(cx: &MatchCheckCtxt, pat: &Pat) { |
| front_util::walk_pat(pat, |p| { |
| match p.node { |
| hir::PatIdent(hir::BindByValue(hir::MutImmutable), ident, None) => { |
| let pat_ty = cx.tcx.pat_ty(p); |
| if let ty::TyEnum(edef, _) = pat_ty.sty { |
| let def = cx.tcx.def_map.borrow().get(&p.id).map(|d| d.full_def()); |
| if let Some(DefLocal(..)) = def { |
| if edef.variants.iter().any(|variant| |
| variant.name == ident.node.unhygienic_name |
| && 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 `{}`", |
| ident.node, ty_path); |
| fileline_help!(err, p.span, |
| "if you meant to match on a variant, \ |
| consider making the path in the pattern qualified: `{}::{}`", |
| ty_path, ident.node); |
| err.emit(); |
| } |
| } |
| } |
| } |
| _ => () |
| } |
| true |
| }); |
| } |
| |
| // Check that we do not match against a static NaN (#6804) |
| fn check_for_static_nan(cx: &MatchCheckCtxt, pat: &Pat) { |
| front_util::walk_pat(pat, |p| { |
| if let hir::PatLit(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) => { |
| let mut diag = struct_span_err!(cx.tcx.sess, err.span, E0471, |
| "constant evaluation error: {}", |
| err.description()); |
| if !p.span.contains(err.span) { |
| diag.span_note(p.span, "in pattern here"); |
| } |
| diag.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![&**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) |
| cx.tcx.sess.span_bug(pat.span, "unreachable for-loop pattern") |
| }, |
| |
| hir::MatchSource::Normal => { |
| span_err!(cx.tcx.sess, pat.span, E0001, "unreachable pattern") |
| }, |
| } |
| } |
| Useful => (), |
| UsefulWithWitness(_) => unreachable!() |
| } |
| if guard.is_none() { |
| let Matrix(mut rows) = seen; |
| rows.push(v); |
| seen = Matrix(rows); |
| } |
| } |
| } |
| } |
| |
| fn raw_pat<'a>(p: &'a Pat) -> &'a Pat { |
| match p.node { |
| hir::PatIdent(_, _, Some(ref s)) => raw_pat(&**s), |
| _ => p |
| } |
| } |
| |
| fn check_exhaustive(cx: &MatchCheckCtxt, sp: Span, matrix: &Matrix, source: hir::MatchSource) { |
| match is_useful(cx, matrix, &[DUMMY_WILD_PAT], ConstructWitness) { |
| UsefulWithWitness(pats) => { |
| let witness = match &pats[..] { |
| [ref witness] => &**witness, |
| [] => DUMMY_WILD_PAT, |
| _ => unreachable!() |
| }; |
| match source { |
| hir::MatchSource::ForLoopDesugar => { |
| // `witness` has the form `Some(<head>)`, peel off the `Some` |
| let witness = match witness.node { |
| hir::PatEnum(_, Some(ref pats)) => match &pats[..] { |
| [ref pat] => &**pat, |
| _ => unreachable!(), |
| }, |
| _ => unreachable!(), |
| }; |
| |
| span_err!(cx.tcx.sess, sp, E0297, |
| "refutable pattern in `for` loop binding: \ |
| `{}` not covered", |
| pat_to_string(witness)); |
| }, |
| _ => { |
| span_err!(cx.tcx.sess, sp, E0004, |
| "non-exhaustive patterns: `{}` not covered", |
| pat_to_string(witness) |
| ); |
| }, |
| } |
| } |
| NotUseful => { |
| // This is good, wildcard pattern isn't reachable |
| }, |
| _ => unreachable!() |
| } |
| } |
| |
| fn const_val_to_expr(value: &ConstVal) -> P<hir::Expr> { |
| let node = match value { |
| &ConstVal::Bool(b) => ast::LitBool(b), |
| _ => unreachable!() |
| }; |
| P(hir::Expr { |
| id: 0, |
| node: hir::ExprLit(P(Spanned { node: node, span: DUMMY_SP })), |
| span: DUMMY_SP, |
| attrs: None, |
| }) |
| } |
| |
| pub struct StaticInliner<'a, 'tcx: 'a> { |
| pub tcx: &'a ty::ctxt<'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: &'b ty::ctxt<'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<'map> ast_util::IdVisitingOperation 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 { |
| hir::PatIdent(..) | hir::PatEnum(..) | hir::PatQPath(..) => { |
| let def = self.tcx.def_map.borrow().get(&pat.id).map(|d| d.full_def()); |
| match def { |
| Some(DefAssociatedConst(did)) | |
| Some(DefConst(did)) => match lookup_const_by_id(self.tcx, did, |
| Some(pat.id), None) { |
| Some(const_expr) => { |
| const_expr_to_pat(self.tcx, const_expr, pat.span).map(|new_pat| { |
| |
| if let Some(ref mut renaming_map) = self.renaming_map { |
| // Record any renamings we do here |
| record_renamings(const_expr, &pat, renaming_map); |
| } |
| |
| new_pat |
| }) |
| } |
| None => { |
| 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, |
| }; |
| |
| let mut id_visitor = front_util::IdVisitor::new(&mut renaming_recorder); |
| |
| id_visitor.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(_) => hir::PatTup(pats.collect()), |
| |
| ty::TyEnum(adt, _) | ty::TyStruct(adt, _) => { |
| let v = adt.variant_of_ctor(ctor); |
| if let VariantKind::Struct = v.kind() { |
| let field_pats: hir::HirVec<_> = v.fields.iter() |
| .zip(pats) |
| .filter(|&(_, ref pat)| pat.node != hir::PatWild) |
| .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; |
| hir::PatStruct(def_to_path(cx.tcx, v.did), field_pats, has_more_fields) |
| } else { |
| hir::PatEnum(def_to_path(cx.tcx, v.did), Some(pats.collect())) |
| } |
| } |
| |
| ty::TyRef(_, ty::TypeAndMut { ty, mutbl }) => { |
| match ty.sty { |
| ty::TyArray(_, n) => match ctor { |
| &Single => { |
| assert_eq!(pats_len, n); |
| hir::PatVec(pats.collect(), None, hir::HirVec::new()) |
| }, |
| _ => unreachable!() |
| }, |
| ty::TySlice(_) => match ctor { |
| &Slice(n) => { |
| assert_eq!(pats_len, n); |
| hir::PatVec(pats.collect(), None, hir::HirVec::new()) |
| }, |
| _ => unreachable!() |
| }, |
| ty::TyStr => hir::PatWild, |
| |
| _ => { |
| assert_eq!(pats_len, 1); |
| hir::PatRegion(pats.nth(0).unwrap(), mutbl) |
| } |
| } |
| } |
| |
| ty::TyArray(_, len) => { |
| assert_eq!(pats_len, len); |
| hir::PatVec(pats.collect(), None, hir::HirVec::new()) |
| } |
| |
| _ => { |
| match *ctor { |
| ConstantValue(ref v) => hir::PatLit(const_val_to_expr(v)), |
| _ => hir::PatWild, |
| } |
| } |
| }; |
| |
| P(hir::Pat { |
| id: 0, |
| node: pat, |
| span: DUMMY_SP |
| }) |
| } |
| |
| impl<'tcx, 'container> ty::AdtDefData<'tcx, 'container> { |
| fn variant_of_ctor(&self, |
| ctor: &Constructor) |
| -> &VariantDefData<'tcx, 'container> { |
| match ctor { |
| &Variant(vid) => self.variant_with_id(vid), |
| _ => self.struct_variant() |
| } |
| } |
| } |
| |
| fn missing_constructor(cx: &MatchCheckCtxt, &Matrix(ref rows): &Matrix, |
| left_ty: Ty, max_slice_length: usize) -> Option<Constructor> { |
| let used_constructors: Vec<Constructor> = rows.iter() |
| .flat_map(|row| pat_constructors(cx, row[0], left_ty, max_slice_length)) |
| .collect(); |
| all_constructors(cx, left_ty, max_slice_length) |
| .into_iter() |
| .find(|c| !used_constructors.contains(c)) |
| } |
| |
| /// 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::TyRef(_, ty::TypeAndMut { ty, .. }) => match ty.sty { |
| ty::TySlice(_) => |
| (0..max_slice_length+1).map(|length| Slice(length)).collect(), |
| _ => vec![Single] |
| }, |
| |
| 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(cx: &MatchCheckCtxt, |
| matrix: &Matrix, |
| v: &[&Pat], |
| witness: WitnessPreference) |
| -> Usefulness { |
| let &Matrix(ref rows) = matrix; |
| debug!("{:?}", matrix); |
| 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 real_pat = match rows.iter().find(|r| (*r)[0].id != DUMMY_NODE_ID) { |
| Some(r) => raw_pat(r[0]), |
| None if v.is_empty() => return NotUseful, |
| None => v[0] |
| }; |
| let left_ty = if real_pat.id == DUMMY_NODE_ID { |
| cx.tcx.mk_nil() |
| } else { |
| let left_ty = cx.tcx.pat_ty(&*real_pat); |
| |
| match real_pat.node { |
| hir::PatIdent(hir::BindByRef(..), _, _) => { |
| left_ty.builtin_deref(false, NoPreference).unwrap().ty |
| } |
| _ => left_ty, |
| } |
| }; |
| |
| let max_slice_length = rows.iter().filter_map(|row| match row[0].node { |
| hir::PatVec(ref before, _, ref after) => Some(before.len() + after.len()), |
| _ => None |
| }).max().map_or(0, |v| v + 1); |
| |
| let constructors = pat_constructors(cx, v[0], left_ty, max_slice_length); |
| if constructors.is_empty() { |
| match missing_constructor(cx, matrix, left_ty, max_slice_length) { |
| None => { |
| 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) |
| }, |
| |
| Some(constructor) => { |
| let matrix = rows.iter().filter_map(|r| { |
| if pat_is_binding_or_wild(&cx.tcx.def_map.borrow(), raw_pat(r[0])) { |
| Some(r[1..].to_vec()) |
| } else { |
| None |
| } |
| }).collect(); |
| match is_useful(cx, &matrix, &v[1..], witness) { |
| UsefulWithWitness(pats) => { |
| let arity = constructor_arity(cx, &constructor, left_ty); |
| let wild_pats = vec![DUMMY_WILD_PAT; arity]; |
| let enum_pat = construct_witness(cx, &constructor, wild_pats, left_ty); |
| let mut new_pats = vec![enum_pat]; |
| 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(cx: &MatchCheckCtxt, &Matrix(ref m): &Matrix, |
| v: &[&Pat], ctor: Constructor, lty: Ty, |
| 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 { |
| hir::PatIdent(..) => |
| match cx.tcx.def_map.borrow().get(&pat.id).map(|d| d.full_def()) { |
| Some(DefConst(..)) | Some(DefAssociatedConst(..)) => |
| cx.tcx.sess.span_bug(pat.span, "const pattern should've \ |
| been rewritten"), |
| Some(DefStruct(_)) => vec!(Single), |
| Some(DefVariant(_, id, _)) => vec!(Variant(id)), |
| _ => vec!() |
| }, |
| hir::PatEnum(..) => |
| match cx.tcx.def_map.borrow().get(&pat.id).map(|d| d.full_def()) { |
| Some(DefConst(..)) | Some(DefAssociatedConst(..)) => |
| cx.tcx.sess.span_bug(pat.span, "const pattern should've \ |
| been rewritten"), |
| Some(DefVariant(_, id, _)) => vec!(Variant(id)), |
| _ => vec!(Single) |
| }, |
| hir::PatQPath(..) => |
| cx.tcx.sess.span_bug(pat.span, "const pattern should've \ |
| been rewritten"), |
| hir::PatStruct(..) => |
| match cx.tcx.def_map.borrow().get(&pat.id).map(|d| d.full_def()) { |
| Some(DefConst(..)) | Some(DefAssociatedConst(..)) => |
| cx.tcx.sess.span_bug(pat.span, "const pattern should've \ |
| been rewritten"), |
| Some(DefVariant(_, id, _)) => vec!(Variant(id)), |
| _ => vec!(Single) |
| }, |
| hir::PatLit(ref expr) => |
| vec!(ConstantValue(eval_const_expr(cx.tcx, &**expr))), |
| hir::PatRange(ref lo, ref hi) => |
| vec!(ConstantRange(eval_const_expr(cx.tcx, &**lo), eval_const_expr(cx.tcx, &**hi))), |
| hir::PatVec(ref before, ref slice, ref after) => |
| match left_ty.sty { |
| ty::TyArray(_, _) => vec!(Single), |
| _ => if slice.is_some() { |
| (before.len() + after.len()..max_slice_length+1) |
| .map(|length| Slice(length)) |
| .collect() |
| } else { |
| vec!(Slice(before.len() + after.len())) |
| } |
| }, |
| hir::PatBox(_) | hir::PatTup(_) | hir::PatRegion(..) => |
| vec!(Single), |
| hir::PatWild => |
| 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 { |
| match ty.sty { |
| ty::TyTuple(ref fs) => fs.len(), |
| ty::TyBox(_) => 1, |
| ty::TyRef(_, ty::TypeAndMut { ty, .. }) => match ty.sty { |
| ty::TySlice(_) => match *ctor { |
| Slice(length) => length, |
| ConstantValue(_) => 0, |
| _ => unreachable!() |
| }, |
| ty::TyStr => 0, |
| _ => 1 |
| }, |
| ty::TyEnum(adt, _) | ty::TyStruct(adt, _) => { |
| adt.variant_of_ctor(ctor).fields.len() |
| } |
| ty::TyArray(_, n) => n, |
| _ => 0 |
| } |
| } |
| |
| fn range_covered_by_constructor(ctor: &Constructor, |
| from: &ConstVal, to: &ConstVal) -> Option<bool> { |
| let (c_from, c_to) = match *ctor { |
| ConstantValue(ref value) => (value, value), |
| ConstantRange(ref from, ref to) => (from, to), |
| Single => return Some(true), |
| _ => unreachable!() |
| }; |
| let cmp_from = compare_const_vals(c_from, from); |
| let cmp_to = compare_const_vals(c_to, to); |
| match (cmp_from, cmp_to) { |
| (Some(cmp_from), Some(cmp_to)) => { |
| Some(cmp_from != Ordering::Less && cmp_to != Ordering::Greater) |
| } |
| _ => None |
| } |
| } |
| |
| /// 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>(cx: &MatchCheckCtxt, r: &[&'a Pat], |
| constructor: &Constructor, col: usize, arity: usize) -> Option<Vec<&'a Pat>> { |
| let &Pat { |
| id: pat_id, ref node, span: pat_span |
| } = raw_pat(r[col]); |
| let head: Option<Vec<&Pat>> = match *node { |
| hir::PatWild => |
| Some(vec![DUMMY_WILD_PAT; arity]), |
| |
| hir::PatIdent(_, _, _) => { |
| let opt_def = cx.tcx.def_map.borrow().get(&pat_id).map(|d| d.full_def()); |
| match opt_def { |
| Some(DefConst(..)) | Some(DefAssociatedConst(..)) => |
| cx.tcx.sess.span_bug(pat_span, "const pattern should've \ |
| been rewritten"), |
| Some(DefVariant(_, id, _)) => if *constructor == Variant(id) { |
| Some(vec!()) |
| } else { |
| None |
| }, |
| _ => Some(vec![DUMMY_WILD_PAT; arity]) |
| } |
| } |
| |
| hir::PatEnum(_, ref args) => { |
| let def = cx.tcx.def_map.borrow().get(&pat_id).unwrap().full_def(); |
| match def { |
| DefConst(..) | DefAssociatedConst(..) => |
| cx.tcx.sess.span_bug(pat_span, "const pattern should've \ |
| been rewritten"), |
| DefVariant(_, id, _) if *constructor != Variant(id) => None, |
| DefVariant(..) | DefStruct(..) => { |
| Some(match args { |
| &Some(ref args) => args.iter().map(|p| &**p).collect(), |
| &None => vec![DUMMY_WILD_PAT; arity], |
| }) |
| } |
| _ => None |
| } |
| } |
| |
| hir::PatQPath(_, _) => { |
| cx.tcx.sess.span_bug(pat_span, "const pattern should've \ |
| been rewritten") |
| } |
| |
| hir::PatStruct(_, ref pattern_fields, _) => { |
| let def = cx.tcx.def_map.borrow().get(&pat_id).unwrap().full_def(); |
| let adt = cx.tcx.node_id_to_type(pat_id).ty_adt_def().unwrap(); |
| let variant = adt.variant_of_ctor(constructor); |
| let def_variant = adt.variant_of_def(def); |
| 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) => &*f.node.pat, |
| _ => DUMMY_WILD_PAT |
| } |
| }).collect()) |
| } else { |
| None |
| } |
| } |
| |
| hir::PatTup(ref args) => |
| Some(args.iter().map(|p| &**p).collect()), |
| |
| hir::PatBox(ref inner) | hir::PatRegion(ref inner, _) => |
| Some(vec![&**inner]), |
| |
| hir::PatLit(ref expr) => { |
| let expr_value = eval_const_expr(cx.tcx, &**expr); |
| match range_covered_by_constructor(constructor, &expr_value, &expr_value) { |
| Some(true) => Some(vec![]), |
| Some(false) => None, |
| None => { |
| span_err!(cx.tcx.sess, pat_span, E0298, "mismatched types between arms"); |
| None |
| } |
| } |
| } |
| |
| hir::PatRange(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(constructor, &from_value, &to_value) { |
| Some(true) => Some(vec![]), |
| Some(false) => None, |
| None => { |
| span_err!(cx.tcx.sess, pat_span, E0299, "mismatched types between arms"); |
| None |
| } |
| } |
| } |
| |
| hir::PatVec(ref before, ref slice, ref after) => { |
| match *constructor { |
| // Fixed-length vectors. |
| Single => { |
| let mut pats: Vec<&Pat> = before.iter().map(|p| &**p).collect(); |
| pats.extend(repeat(DUMMY_WILD_PAT).take(arity - before.len() - after.len())); |
| pats.extend(after.iter().map(|p| &**p)); |
| Some(pats) |
| }, |
| Slice(length) if before.len() + after.len() <= length && slice.is_some() => { |
| let mut pats: Vec<&Pat> = before.iter().map(|p| &**p).collect(); |
| pats.extend(repeat(DUMMY_WILD_PAT).take(arity - before.len() - after.len())); |
| pats.extend(after.iter().map(|p| &**p)); |
| Some(pats) |
| }, |
| Slice(length) if before.len() + after.len() == length => { |
| let mut pats: Vec<&Pat> = before.iter().map(|p| &**p).collect(); |
| pats.extend(after.iter().map(|p| &**p)); |
| Some(pats) |
| }, |
| SliceWithSubslice(prefix, suffix) |
| if before.len() == prefix |
| && after.len() == suffix |
| && slice.is_some() => { |
| let mut pats: Vec<&Pat> = before.iter().map(|p| &**p).collect(); |
| pats.extend(after.iter().map(|p| &**p)); |
| Some(pats) |
| } |
| _ => None |
| } |
| } |
| }; |
| 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); |
| |
| 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!(pat))); |
| match is_useful(cx, &pats, &[DUMMY_WILD_PAT], ConstructWitness) { |
| UsefulWithWitness(pats) => { |
| assert_eq!(pats.len(), 1); |
| Some(refutable(&*pats[0])) |
| }, |
| NotUseful => None, |
| Useful => unreachable!() |
| } |
| } |
| |
| // Legality of move bindings checking |
| fn check_legality_of_move_bindings(cx: &MatchCheckCtxt, |
| has_guard: bool, |
| pats: &[P<Pat>]) { |
| let tcx = cx.tcx; |
| let def_map = &tcx.def_map; |
| let mut by_ref_span = None; |
| for pat in pats { |
| pat_bindings(def_map, &**pat, |bm, _, span, _path| { |
| match bm { |
| hir::BindByRef(_) => { |
| by_ref_span = Some(span); |
| } |
| hir::BindByValue(_) => { |
| } |
| } |
| }) |
| } |
| |
| 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(&def_map.borrow(), &*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 { |
| front_util::walk_pat(&**pat, |p| { |
| if pat_is_binding(&def_map.borrow(), &*p) { |
| match p.node { |
| hir::PatIdent(hir::BindByValue(_), _, ref sub) => { |
| let pat_ty = tcx.node_id_to_type(p.id); |
| //FIXME: (@jroesch) this code should be floated up as well |
| let infcx = infer::new_infer_ctxt(cx.tcx, |
| &cx.tcx.tables, |
| Some(cx.param_env.clone()), |
| false); |
| if infcx.type_moves_by_default(pat_ty, pat.span) { |
| check_move(p, sub.as_ref().map(|p| &**p)); |
| } |
| } |
| hir::PatIdent(hir::BindByRef(_), _, _) => { |
| } |
| _ => { |
| cx.tcx.sess.span_bug( |
| p.span, |
| &format!("binding pattern {} is not an \ |
| identifier: {:?}", |
| p.id, |
| p.node)); |
| } |
| } |
| } |
| 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) { |
| let mut checker = MutationChecker { |
| cx: cx, |
| }; |
| |
| let infcx = infer::new_infer_ctxt(cx.tcx, |
| &cx.tcx.tables, |
| Some(checker.cx.param_env.clone()), |
| false); |
| |
| let mut visitor = ExprUseVisitor::new(&mut checker, &infcx); |
| visitor.walk_expr(guard); |
| } |
| |
| struct MutationChecker<'a, 'tcx: 'a> { |
| cx: &'a MatchCheckCtxt<'a, 'tcx>, |
| } |
| |
| impl<'a, 'tcx> Delegate<'tcx> for MutationChecker<'a, 'tcx> { |
| 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) { |
| if !self.bindings_allowed && pat_is_binding(&self.cx.tcx.def_map.borrow(), pat) { |
| span_err!(self.cx.tcx.sess, pat.span, E0303, |
| "pattern bindings are not allowed \ |
| after an `@`"); |
| } |
| |
| match pat.node { |
| hir::PatIdent(_, _, 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), |
| } |
| } |
| } |