compiler/rustc_hir/src/pat_util.rs

   1 use crate::def::{CtorOf, DefKind, Res};
   2 use crate::def_id::DefId;
   3 use crate::hir::{self, HirId, PatKind};
   4 use rustc_data_structures::stable_set::FxHashSet;
   5 use rustc_span::symbol::Ident;
   6 use rustc_span::Span;
   7
   8 use std::iter::{Enumerate, ExactSizeIterator};
   9
  10 pub struct EnumerateAndAdjust<I> {
  11     enumerate: Enumerate<I>,
  12     gap_pos: usize,
  13     gap_len: usize,
  14 }
  15
  16 impl<I> Iterator for EnumerateAndAdjust<I>
  17 where
  18     I: Iterator,
  19 {
  20     type Item = (usize, <I as Iterator>::Item);
  21
  22     fn next(&mut self) -> Option<(usize, <I as Iterator>::Item)> {
  23         self.enumerate
  24             .next()
  25             .map(|(i, elem)| (if i < self.gap_pos { i } else { i + self.gap_len }, elem))
  26     }
  27
  28     fn size_hint(&self) -> (usize, Option<usize>) {
  29         self.enumerate.size_hint()
  30     }
  31 }
  32
  33 pub trait EnumerateAndAdjustIterator {
  34     fn enumerate_and_adjust(
  35         self,
  36         expected_len: usize,
  37         gap_pos: Option<usize>,
  38     ) -> EnumerateAndAdjust<Self>
  39     where
  40         Self: Sized;
  41 }
  42
  43 impl<T: ExactSizeIterator> EnumerateAndAdjustIterator for T {
  44     fn enumerate_and_adjust(
  45         self,
  46         expected_len: usize,
  47         gap_pos: Option<usize>,
  48     ) -> EnumerateAndAdjust<Self>
  49     where
  50         Self: Sized,
  51     {
  52         let actual_len = self.len();
  53         EnumerateAndAdjust {
  54             enumerate: self.enumerate(),
  55             gap_pos: gap_pos.unwrap_or(expected_len),
  56             gap_len: expected_len - actual_len,
  57         }
  58     }
  59 }
  60
  61 impl hir::Pat<'_> {
  62     /// Call `f` on every "binding" in a pattern, e.g., on `a` in
  63     /// `match foo() { Some(a) => (), None => () }`
  64     pub fn each_binding(&self, mut f: impl FnMut(hir::BindingAnnotation, HirId, Span, Ident)) {
  65         self.walk_always(|p| {
  66             if let PatKind::Binding(binding_mode, _, ident, _) = p.kind {
  67                 f(binding_mode, p.hir_id, p.span, ident);
  68             }
  69         });
  70     }
  71
  72     /// Call `f` on every "binding" in a pattern, e.g., on `a` in
  73     /// `match foo() { Some(a) => (), None => () }`.
  74     ///
  75     /// When encountering an or-pattern `p_0 | ... | p_n` only `p_0` will be visited.
  76     pub fn each_binding_or_first(
  77         &self,
  78         f: &mut impl FnMut(hir::BindingAnnotation, HirId, Span, Ident),
  79     ) {
  80         self.walk(|p| match &p.kind {
  81             PatKind::Or(ps) => {
  82                 ps[0].each_binding_or_first(f);
  83                 false
  84             }
  85             PatKind::Binding(bm, _, ident, _) => {
  86                 f(*bm, p.hir_id, p.span, *ident);
  87                 true
  88             }
  89             _ => true,
  90         })
  91     }
  92
  93     pub fn simple_ident(&self) -> Option<Ident> {
  94         match self.kind {
  95             PatKind::Binding(
  96                 hir::BindingAnnotation::Unannotated | hir::BindingAnnotation::Mutable,
  97                 _,
  98                 ident,
  99                 None,
 100             ) => Some(ident),
 101             _ => None,
 102         }
 103     }
 104
 105     /// Returns variants that are necessary to exist for the pattern to match.
 106     pub fn necessary_variants(&self) -> Vec<DefId> {
 107         let mut variants = vec![];
 108         self.walk(|p| match &p.kind {
 109             PatKind::Or(_) => false,
 110             PatKind::Path(hir::QPath::Resolved(_, path))
 111             | PatKind::TupleStruct(hir::QPath::Resolved(_, path), ..)
 112             | PatKind::Struct(hir::QPath::Resolved(_, path), ..) => {
 113                 if let Res::Def(DefKind::Variant | DefKind::Ctor(CtorOf::Variant, ..), id) =
 114                     path.res
 115                 {
 116                     variants.push(id);
 117                 }
 118                 true
 119             }
 120             _ => true,
 121         });
 122         // We remove duplicates by inserting into a `FxHashSet` to avoid re-ordering
 123         // the bounds
 124         let mut duplicates = FxHashSet::default();
 125         variants.retain(|def_id| duplicates.insert(*def_id));
 126         variants
 127     }
 128
 129     /// Checks if the pattern contains any `ref` or `ref mut` bindings, and if
 130     /// yes whether it contains mutable or just immutables ones.
 131     //
 132     // FIXME(tschottdorf): this is problematic as the HIR is being scraped, but
 133     // ref bindings are be implicit after #42640 (default match binding modes). See issue #44848.
 134     pub fn contains_explicit_ref_binding(&self) -> Option<hir::Mutability> {
 135         let mut result = None;
 136         self.each_binding(|annotation, _, _, _| match annotation {
 137             hir::BindingAnnotation::Ref => match result {
 138                 None | Some(hir::Mutability::Not) => result = Some(hir::Mutability::Not),
 139                 _ => {}
 140             },
 141             hir::BindingAnnotation::RefMut => result = Some(hir::Mutability::Mut),
 142             _ => {}
 143         });
 144         result
 145     }
 146 }