compiler/rustc_mir_build/src/build/matches/util.rs

   1 use crate::build::expr::as_place::PlaceBuilder;
   2 use crate::build::matches::MatchPair;
   3 use crate::build::Builder;
   4 use crate::thir::*;
   5 use rustc_middle::mir::*;
   6 use rustc_middle::ty;
   7 use smallvec::SmallVec;
   8 use std::convert::TryInto;
   9
  10 impl<'a, 'tcx> Builder<'a, 'tcx> {
  11     crate fn field_match_pairs<'pat>(
  12         &mut self,
  13         place: PlaceBuilder<'tcx>,
  14         subpatterns: &'pat [FieldPat<'tcx>],
  15     ) -> Vec<MatchPair<'pat, 'tcx>> {
  16         subpatterns
  17             .iter()
  18             .map(|fieldpat| {
  19                 let place = place.clone().field(fieldpat.field, fieldpat.pattern.ty);
  20                 MatchPair::new(place, &fieldpat.pattern)
  21             })
  22             .collect()
  23     }
  24
  25     crate fn prefix_slice_suffix<'pat>(
  26         &mut self,
  27         match_pairs: &mut SmallVec<[MatchPair<'pat, 'tcx>; 1]>,
  28         place: &PlaceBuilder<'tcx>,
  29         prefix: &'pat [Pat<'tcx>],
  30         opt_slice: Option<&'pat Pat<'tcx>>,
  31         suffix: &'pat [Pat<'tcx>],
  32     ) {
  33         let tcx = self.tcx;
  34         let (min_length, exact_size) = match place
  35             .clone()
  36             .into_place(tcx, self.typeck_results)
  37             .ty(&self.local_decls, tcx)
  38             .ty
  39             .kind()
  40         {
  41             ty::Array(_, length) => (length.eval_usize(tcx, self.param_env), true),
  42             _ => ((prefix.len() + suffix.len()).try_into().unwrap(), false),
  43         };
  44
  45         match_pairs.extend(prefix.iter().enumerate().map(|(idx, subpattern)| {
  46             let elem =
  47                 ProjectionElem::ConstantIndex { offset: idx as u64, min_length, from_end: false };
  48             let place = place.clone().project(elem);
  49             MatchPair::new(place, subpattern)
  50         }));
  51
  52         if let Some(subslice_pat) = opt_slice {
  53             let suffix_len = suffix.len() as u64;
  54             let subslice = place.clone().project(ProjectionElem::Subslice {
  55                 from: prefix.len() as u64,
  56                 to: if exact_size { min_length - suffix_len } else { suffix_len },
  57                 from_end: !exact_size,
  58             });
  59             match_pairs.push(MatchPair::new(subslice, subslice_pat));
  60         }
  61
  62         match_pairs.extend(suffix.iter().rev().enumerate().map(|(idx, subpattern)| {
  63             let end_offset = (idx + 1) as u64;
  64             let elem = ProjectionElem::ConstantIndex {
  65                 offset: if exact_size { min_length - end_offset } else { end_offset },
  66                 min_length,
  67                 from_end: !exact_size,
  68             };
  69             let place = place.clone().project(elem);
  70             MatchPair::new(place, subpattern)
  71         }));
  72     }
  73
  74     /// Creates a false edge to `imaginary_target` and a real edge to
  75     /// real_target. If `imaginary_target` is none, or is the same as the real
  76     /// target, a Goto is generated instead to simplify the generated MIR.
  77     crate fn false_edges(
  78         &mut self,
  79         from_block: BasicBlock,
  80         real_target: BasicBlock,
  81         imaginary_target: Option<BasicBlock>,
  82         source_info: SourceInfo,
  83     ) {
  84         match imaginary_target {
  85             Some(target) if target != real_target => {
  86                 self.cfg.terminate(
  87                     from_block,
  88                     source_info,
  89                     TerminatorKind::FalseEdge { real_target, imaginary_target: target },
  90                 );
  91             }
  92             _ => self.cfg.goto(from_block, source_info, real_target),
  93         }
  94     }
  95 }
  96
  97 impl<'pat, 'tcx> MatchPair<'pat, 'tcx> {
  98     crate fn new(place: PlaceBuilder<'tcx>, pattern: &'pat Pat<'tcx>) -> MatchPair<'pat, 'tcx> {
  99         MatchPair { place, pattern }
 100     }
 101 }