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| 1 | +use core::panic; |
| 2 | + |
| 3 | +use rustc_type_ir::data_structures::IndexMap; |
| 4 | +use rustc_type_ir::inherent::*; |
| 5 | +use rustc_type_ir::{ |
| 6 | + self as ty, InferCtxtLike, Interner, TypeFoldable, TypeFolder, TypeSuperFoldable, |
| 7 | + TypeVisitableExt, |
| 8 | +}; |
| 9 | + |
| 10 | +pub struct BoundVarReplacer<'a, Infcx, I = <Infcx as InferCtxtLike>::Interner> |
| 11 | +where |
| 12 | + Infcx: InferCtxtLike<Interner = I>, |
| 13 | + I: Interner, |
| 14 | +{ |
| 15 | + infcx: &'a Infcx, |
| 16 | + // These three maps track the bound variable that were replaced by placeholders. It might be |
| 17 | + // nice to remove these since we already have the `kind` in the placeholder; we really just need |
| 18 | + // the `var` (but we *could* bring that into scope if we were to track them as we pass them). |
| 19 | + mapped_regions: IndexMap<I::PlaceholderRegion, I::BoundRegion>, |
| 20 | + mapped_types: IndexMap<I::PlaceholderTy, I::BoundTy>, |
| 21 | + mapped_consts: IndexMap<I::PlaceholderConst, I::BoundConst>, |
| 22 | + // The current depth relative to *this* folding, *not* the entire normalization. In other words, |
| 23 | + // the depth of binders we've passed here. |
| 24 | + current_index: ty::DebruijnIndex, |
| 25 | + // The `UniverseIndex` of the binding levels above us. These are optional, since we are lazy: |
| 26 | + // we don't actually create a universe until we see a bound var we have to replace. |
| 27 | + universe_indices: &'a mut Vec<Option<ty::UniverseIndex>>, |
| 28 | +} |
| 29 | + |
| 30 | +impl<'a, Infcx, I> BoundVarReplacer<'a, Infcx, I> |
| 31 | +where |
| 32 | + Infcx: InferCtxtLike<Interner = I>, |
| 33 | + I: Interner, |
| 34 | +{ |
| 35 | + /// Returns `Some` if we *were* able to replace bound vars. If there are any bound vars that |
| 36 | + /// use a binding level above `universe_indices.len()`, we fail. |
| 37 | + pub fn replace_bound_vars<T: TypeFoldable<I>>( |
| 38 | + infcx: &'a Infcx, |
| 39 | + universe_indices: &'a mut Vec<Option<ty::UniverseIndex>>, |
| 40 | + value: T, |
| 41 | + ) -> ( |
| 42 | + T, |
| 43 | + IndexMap<I::PlaceholderRegion, I::BoundRegion>, |
| 44 | + IndexMap<I::PlaceholderTy, I::BoundTy>, |
| 45 | + IndexMap<I::PlaceholderConst, I::BoundConst>, |
| 46 | + ) { |
| 47 | + let mut replacer = BoundVarReplacer { |
| 48 | + infcx, |
| 49 | + mapped_regions: Default::default(), |
| 50 | + mapped_types: Default::default(), |
| 51 | + mapped_consts: Default::default(), |
| 52 | + current_index: ty::INNERMOST, |
| 53 | + universe_indices, |
| 54 | + }; |
| 55 | + |
| 56 | + let value = value.fold_with(&mut replacer); |
| 57 | + |
| 58 | + (value, replacer.mapped_regions, replacer.mapped_types, replacer.mapped_consts) |
| 59 | + } |
| 60 | + |
| 61 | + fn universe_for(&mut self, debruijn: ty::DebruijnIndex) -> ty::UniverseIndex { |
| 62 | + let infcx = self.infcx; |
| 63 | + let index = |
| 64 | + self.universe_indices.len() + self.current_index.as_usize() - debruijn.as_usize() - 1; |
| 65 | + let universe = self.universe_indices[index].unwrap_or_else(|| { |
| 66 | + for i in self.universe_indices.iter_mut().take(index + 1) { |
| 67 | + *i = i.or_else(|| Some(infcx.create_next_universe())) |
| 68 | + } |
| 69 | + self.universe_indices[index].unwrap() |
| 70 | + }); |
| 71 | + universe |
| 72 | + } |
| 73 | +} |
| 74 | + |
| 75 | +impl<Infcx, I> TypeFolder<I> for BoundVarReplacer<'_, Infcx, I> |
| 76 | +where |
| 77 | + Infcx: InferCtxtLike<Interner = I>, |
| 78 | + I: Interner, |
| 79 | +{ |
| 80 | + fn cx(&self) -> I { |
| 81 | + self.infcx.cx() |
| 82 | + } |
| 83 | + |
| 84 | + fn fold_binder<T: TypeFoldable<I>>(&mut self, t: ty::Binder<I, T>) -> ty::Binder<I, T> { |
| 85 | + self.current_index.shift_in(1); |
| 86 | + let t = t.super_fold_with(self); |
| 87 | + self.current_index.shift_out(1); |
| 88 | + t |
| 89 | + } |
| 90 | + |
| 91 | + fn fold_region(&mut self, r: I::Region) -> I::Region { |
| 92 | + match r.kind() { |
| 93 | + ty::ReBound(debruijn, _) |
| 94 | + if debruijn.as_usize() |
| 95 | + >= self.current_index.as_usize() + self.universe_indices.len() => |
| 96 | + { |
| 97 | + panic!( |
| 98 | + "Bound vars {r:#?} outside of `self.universe_indices`: {:#?}", |
| 99 | + self.universe_indices |
| 100 | + ); |
| 101 | + } |
| 102 | + ty::ReBound(debruijn, br) if debruijn >= self.current_index => { |
| 103 | + let universe = self.universe_for(debruijn); |
| 104 | + let p = PlaceholderLike::new(universe, br); |
| 105 | + self.mapped_regions.insert(p, br); |
| 106 | + Region::new_placeholder(self.cx(), p) |
| 107 | + } |
| 108 | + _ => r, |
| 109 | + } |
| 110 | + } |
| 111 | + |
| 112 | + fn fold_ty(&mut self, t: I::Ty) -> I::Ty { |
| 113 | + match t.kind() { |
| 114 | + ty::Bound(debruijn, _) |
| 115 | + if debruijn.as_usize() + 1 |
| 116 | + > self.current_index.as_usize() + self.universe_indices.len() => |
| 117 | + { |
| 118 | + panic!( |
| 119 | + "Bound vars {t:#?} outside of `self.universe_indices`: {:#?}", |
| 120 | + self.universe_indices |
| 121 | + ); |
| 122 | + } |
| 123 | + ty::Bound(debruijn, bound_ty) if debruijn >= self.current_index => { |
| 124 | + let universe = self.universe_for(debruijn); |
| 125 | + let p = PlaceholderLike::new(universe, bound_ty); |
| 126 | + self.mapped_types.insert(p, bound_ty); |
| 127 | + Ty::new_placeholder(self.cx(), p) |
| 128 | + } |
| 129 | + _ if t.has_vars_bound_at_or_above(self.current_index) => t.super_fold_with(self), |
| 130 | + _ => t, |
| 131 | + } |
| 132 | + } |
| 133 | + |
| 134 | + fn fold_const(&mut self, ct: I::Const) -> I::Const { |
| 135 | + match ct.kind() { |
| 136 | + ty::ConstKind::Bound(debruijn, _) |
| 137 | + if debruijn.as_usize() + 1 |
| 138 | + > self.current_index.as_usize() + self.universe_indices.len() => |
| 139 | + { |
| 140 | + panic!( |
| 141 | + "Bound vars {ct:#?} outside of `self.universe_indices`: {:#?}", |
| 142 | + self.universe_indices |
| 143 | + ); |
| 144 | + } |
| 145 | + ty::ConstKind::Bound(debruijn, bound_const) if debruijn >= self.current_index => { |
| 146 | + let universe = self.universe_for(debruijn); |
| 147 | + let p = PlaceholderLike::new(universe, bound_const); |
| 148 | + self.mapped_consts.insert(p, bound_const); |
| 149 | + Const::new_placeholder(self.cx(), p) |
| 150 | + } |
| 151 | + _ => ct.super_fold_with(self), |
| 152 | + } |
| 153 | + } |
| 154 | + |
| 155 | + fn fold_predicate(&mut self, p: I::Predicate) -> I::Predicate { |
| 156 | + if p.has_vars_bound_at_or_above(self.current_index) { p.super_fold_with(self) } else { p } |
| 157 | + } |
| 158 | +} |
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