src/librustc/middle/pat_util.rs

   1 // Copyright 2012 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use middle::def::*;
  12 use middle::def_id::DefId;
  13 use middle::ty;
  14 use util::nodemap::FnvHashMap;
  15
  16 use syntax::ast;
  17 use rustc_front::hir::{self, PatKind};
  18 use rustc_front::util::walk_pat;
  19 use syntax::codemap::{respan, Span, Spanned, DUMMY_SP};
  20
  21 use std::cell::RefCell;
  22
  23 pub type PatIdMap = FnvHashMap<ast::Name, ast::NodeId>;
  24
  25 // This is used because same-named variables in alternative patterns need to
  26 // use the NodeId of their namesake in the first pattern.
  27 pub fn pat_id_map(dm: &RefCell<DefMap>, pat: &hir::Pat) -> PatIdMap {
  28     let mut map = FnvHashMap();
  29     pat_bindings(dm, pat, |_bm, p_id, _s, path1| {
  30         map.insert(path1.node, p_id);
  31     });
  32     map
  33 }
  34
  35 pub fn pat_is_refutable(dm: &DefMap, pat: &hir::Pat) -> bool {
  36     match pat.node {
  37         PatKind::Lit(_) | PatKind::Range(_, _) | PatKind::QPath(..) => true,
  38         PatKind::TupleStruct(..) |
  39         PatKind::Path(..) |
  40         PatKind::Ident(_, _, None) |
  41         PatKind::Struct(..) => {
  42             match dm.get(&pat.id).map(|d| d.full_def()) {
  43                 Some(Def::Variant(..)) => true,
  44                 _ => false
  45             }
  46         }
  47         PatKind::Vec(_, _, _) => true,
  48         _ => false
  49     }
  50 }
  51
  52 pub fn pat_is_variant_or_struct(dm: &DefMap, pat: &hir::Pat) -> bool {
  53     match pat.node {
  54         PatKind::TupleStruct(..) |
  55         PatKind::Path(..) |
  56         PatKind::Ident(_, _, None) |
  57         PatKind::Struct(..) => {
  58             match dm.get(&pat.id).map(|d| d.full_def()) {
  59                 Some(Def::Variant(..)) | Some(Def::Struct(..)) | Some(Def::TyAlias(..)) => true,
  60                 _ => false
  61             }
  62         }
  63         _ => false
  64     }
  65 }
  66
  67 pub fn pat_is_const(dm: &DefMap, pat: &hir::Pat) -> bool {
  68     match pat.node {
  69         PatKind::Ident(_, _, None) | PatKind::Path(..) | PatKind::QPath(..) => {
  70             match dm.get(&pat.id).map(|d| d.full_def()) {
  71                 Some(Def::Const(..)) | Some(Def::AssociatedConst(..)) => true,
  72                 _ => false
  73             }
  74         }
  75         _ => false
  76     }
  77 }
  78
  79 // Same as above, except that partially-resolved defs cause `false` to be
  80 // returned instead of a panic.
  81 pub fn pat_is_resolved_const(dm: &DefMap, pat: &hir::Pat) -> bool {
  82     match pat.node {
  83         PatKind::Ident(_, _, None) | PatKind::Path(..) | PatKind::QPath(..) => {
  84             match dm.get(&pat.id)
  85                     .and_then(|d| if d.depth == 0 { Some(d.base_def) }
  86                                   else { None } ) {
  87                 Some(Def::Const(..)) | Some(Def::AssociatedConst(..)) => true,
  88                 _ => false
  89             }
  90         }
  91         _ => false
  92     }
  93 }
  94
  95 pub fn pat_is_binding(dm: &DefMap, pat: &hir::Pat) -> bool {
  96     match pat.node {
  97         PatKind::Ident(..) => {
  98             !pat_is_variant_or_struct(dm, pat) &&
  99             !pat_is_const(dm, pat)
 100         }
 101         _ => false
 102     }
 103 }
 104
 105 pub fn pat_is_binding_or_wild(dm: &DefMap, pat: &hir::Pat) -> bool {
 106     match pat.node {
 107         PatKind::Ident(..) => pat_is_binding(dm, pat),
 108         PatKind::Wild => true,
 109         _ => false
 110     }
 111 }
 112
 113 /// Call `it` on every "binding" in a pattern, e.g., on `a` in
 114 /// `match foo() { Some(a) => (), None => () }`
 115 pub fn pat_bindings<I>(dm: &RefCell<DefMap>, pat: &hir::Pat, mut it: I) where
 116     I: FnMut(hir::BindingMode, ast::NodeId, Span, &Spanned<ast::Name>),
 117 {
 118     walk_pat(pat, |p| {
 119         match p.node {
 120           PatKind::Ident(binding_mode, ref pth, _) if pat_is_binding(&dm.borrow(), p) => {
 121             it(binding_mode, p.id, p.span, &respan(pth.span, pth.node.name));
 122           }
 123           _ => {}
 124         }
 125         true
 126     });
 127 }
 128 pub fn pat_bindings_ident<I>(dm: &RefCell<DefMap>, pat: &hir::Pat, mut it: I) where
 129     I: FnMut(hir::BindingMode, ast::NodeId, Span, &Spanned<hir::Ident>),
 130 {
 131     walk_pat(pat, |p| {
 132         match p.node {
 133           PatKind::Ident(binding_mode, ref pth, _) if pat_is_binding(&dm.borrow(), p) => {
 134             it(binding_mode, p.id, p.span, &respan(pth.span, pth.node));
 135           }
 136           _ => {}
 137         }
 138         true
 139     });
 140 }
 141
 142 /// Checks if the pattern contains any patterns that bind something to
 143 /// an ident, e.g. `foo`, or `Foo(foo)` or `foo @ Bar(..)`.
 144 pub fn pat_contains_bindings(dm: &DefMap, pat: &hir::Pat) -> bool {
 145     let mut contains_bindings = false;
 146     walk_pat(pat, |p| {
 147         if pat_is_binding(dm, p) {
 148             contains_bindings = true;
 149             false // there's at least one binding, can short circuit now.
 150         } else {
 151             true
 152         }
 153     });
 154     contains_bindings
 155 }
 156
 157 /// Checks if the pattern contains any `ref` or `ref mut` bindings,
 158 /// and if yes whether its containing mutable ones or just immutables ones.
 159 pub fn pat_contains_ref_binding(dm: &RefCell<DefMap>, pat: &hir::Pat) -> Option<hir::Mutability> {
 160     let mut result = None;
 161     pat_bindings(dm, pat, |mode, _, _, _| {
 162         match mode {
 163             hir::BindingMode::BindByRef(m) => {
 164                 // Pick Mutable as maximum
 165                 match result {
 166                     None | Some(hir::MutImmutable) => result = Some(m),
 167                     _ => (),
 168                 }
 169             }
 170             hir::BindingMode::BindByValue(_) => { }
 171         }
 172     });
 173     result
 174 }
 175
 176 /// Checks if the patterns for this arm contain any `ref` or `ref mut`
 177 /// bindings, and if yes whether its containing mutable ones or just immutables ones.
 178 pub fn arm_contains_ref_binding(dm: &RefCell<DefMap>, arm: &hir::Arm) -> Option<hir::Mutability> {
 179     arm.pats.iter()
 180             .filter_map(|pat| pat_contains_ref_binding(dm, pat))
 181             .max_by_key(|m| match *m {
 182                 hir::MutMutable => 1,
 183                 hir::MutImmutable => 0,
 184             })
 185 }
 186
 187 /// Checks if the pattern contains any patterns that bind something to
 188 /// an ident or wildcard, e.g. `foo`, or `Foo(_)`, `foo @ Bar(..)`,
 189 pub fn pat_contains_bindings_or_wild(dm: &DefMap, pat: &hir::Pat) -> bool {
 190     let mut contains_bindings = false;
 191     walk_pat(pat, |p| {
 192         if pat_is_binding_or_wild(dm, p) {
 193             contains_bindings = true;
 194             false // there's at least one binding/wildcard, can short circuit now.
 195         } else {
 196             true
 197         }
 198     });
 199     contains_bindings
 200 }
 201
 202 pub fn simple_name<'a>(pat: &'a hir::Pat) -> Option<ast::Name> {
 203     match pat.node {
 204         PatKind::Ident(hir::BindByValue(_), ref path1, None) => {
 205             Some(path1.node.name)
 206         }
 207         _ => {
 208             None
 209         }
 210     }
 211 }
 212
 213 pub fn def_to_path(tcx: &ty::ctxt, id: DefId) -> hir::Path {
 214     tcx.with_path(id, |path| hir::Path {
 215         global: false,
 216         segments: path.last().map(|elem| hir::PathSegment {
 217             identifier: hir::Ident::from_name(elem.name()),
 218             parameters: hir::PathParameters::none(),
 219         }).into_iter().collect(),
 220         span: DUMMY_SP,
 221     })
 222 }
 223
 224 /// Return variants that are necessary to exist for the pattern to match.
 225 pub fn necessary_variants(dm: &DefMap, pat: &hir::Pat) -> Vec<DefId> {
 226     let mut variants = vec![];
 227     walk_pat(pat, |p| {
 228         match p.node {
 229             PatKind::TupleStruct(..) |
 230             PatKind::Path(..) |
 231             PatKind::Ident(_, _, None) |
 232             PatKind::Struct(..) => {
 233                 match dm.get(&p.id) {
 234                     Some(&PathResolution { base_def: Def::Variant(_, id), .. }) => {
 235                         variants.push(id);
 236                     }
 237                     _ => ()
 238                 }
 239             }
 240             _ => ()
 241         }
 242         true
 243     });
 244     variants.sort();
 245     variants.dedup();
 246     variants
 247 }