]>
Commit | Line | Data |
---|---|---|
c34b1796 | 1 | use super::combine::CombineFields; |
c34b1796 | 2 | use super::lattice::{self, LatticeDir}; |
dfeec247 | 3 | use super::InferCtxt; |
85aaf69f | 4 | use super::Subtype; |
1a4d82fc | 5 | |
9fa01778 | 6 | use crate::traits::ObligationCause; |
ba9703b0 XL |
7 | use rustc_middle::ty::relate::{Relate, RelateResult, TypeRelation}; |
8 | use rustc_middle::ty::{self, Ty, TyCtxt}; | |
1a4d82fc JJ |
9 | |
10 | /// "Greatest lower bound" (common subtype) | |
dc9dc135 XL |
11 | pub struct Glb<'combine, 'infcx, 'tcx> { |
12 | fields: &'combine mut CombineFields<'infcx, 'tcx>, | |
5bcae85e | 13 | a_is_expected: bool, |
1a4d82fc JJ |
14 | } |
15 | ||
dc9dc135 XL |
16 | impl<'combine, 'infcx, 'tcx> Glb<'combine, 'infcx, 'tcx> { |
17 | pub fn new( | |
18 | fields: &'combine mut CombineFields<'infcx, 'tcx>, | |
19 | a_is_expected: bool, | |
20 | ) -> Glb<'combine, 'infcx, 'tcx> { | |
74b04a01 | 21 | Glb { fields, a_is_expected } |
54a0048b | 22 | } |
c34b1796 | 23 | } |
85aaf69f | 24 | |
dc9dc135 | 25 | impl TypeRelation<'tcx> for Glb<'combine, 'infcx, 'tcx> { |
dfeec247 XL |
26 | fn tag(&self) -> &'static str { |
27 | "Glb" | |
28 | } | |
1a4d82fc | 29 | |
dfeec247 XL |
30 | fn tcx(&self) -> TyCtxt<'tcx> { |
31 | self.fields.tcx() | |
32 | } | |
1a4d82fc | 33 | |
dfeec247 XL |
34 | fn param_env(&self) -> ty::ParamEnv<'tcx> { |
35 | self.fields.param_env | |
36 | } | |
416331ca | 37 | |
dfeec247 XL |
38 | fn a_is_expected(&self) -> bool { |
39 | self.a_is_expected | |
40 | } | |
1a4d82fc | 41 | |
dfeec247 XL |
42 | fn relate_with_variance<T: Relate<'tcx>>( |
43 | &mut self, | |
44 | variance: ty::Variance, | |
45 | a: &T, | |
46 | b: &T, | |
47 | ) -> RelateResult<'tcx, T> { | |
c34b1796 | 48 | match variance { |
5bcae85e | 49 | ty::Invariant => self.fields.equate(self.a_is_expected).relate(a, b), |
c34b1796 | 50 | ty::Covariant => self.relate(a, b), |
cc61c64b XL |
51 | // FIXME(#41044) -- not correct, need test |
52 | ty::Bivariant => Ok(a.clone()), | |
5bcae85e | 53 | ty::Contravariant => self.fields.lub(self.a_is_expected).relate(a, b), |
1a4d82fc JJ |
54 | } |
55 | } | |
56 | ||
c34b1796 AL |
57 | fn tys(&mut self, a: Ty<'tcx>, b: Ty<'tcx>) -> RelateResult<'tcx, Ty<'tcx>> { |
58 | lattice::super_lattice_tys(self, a, b) | |
1a4d82fc JJ |
59 | } |
60 | ||
dfeec247 XL |
61 | fn regions( |
62 | &mut self, | |
63 | a: ty::Region<'tcx>, | |
64 | b: ty::Region<'tcx>, | |
65 | ) -> RelateResult<'tcx, ty::Region<'tcx>> { | |
66 | debug!("{}.regions({:?}, {:?})", self.tag(), a, b); | |
1a4d82fc | 67 | |
e1599b0c | 68 | let origin = Subtype(box self.fields.trace.clone()); |
74b04a01 XL |
69 | Ok(self.fields.infcx.inner.borrow_mut().unwrap_region_constraints().glb_regions( |
70 | self.tcx(), | |
71 | origin, | |
72 | a, | |
73 | b, | |
74 | )) | |
1a4d82fc JJ |
75 | } |
76 | ||
48663c56 XL |
77 | fn consts( |
78 | &mut self, | |
79 | a: &'tcx ty::Const<'tcx>, | |
80 | b: &'tcx ty::Const<'tcx>, | |
81 | ) -> RelateResult<'tcx, &'tcx ty::Const<'tcx>> { | |
48663c56 XL |
82 | self.fields.infcx.super_combine_consts(self, a, b) |
83 | } | |
84 | ||
dfeec247 XL |
85 | fn binders<T>( |
86 | &mut self, | |
87 | a: &ty::Binder<T>, | |
88 | b: &ty::Binder<T>, | |
89 | ) -> RelateResult<'tcx, ty::Binder<T>> | |
90 | where | |
91 | T: Relate<'tcx>, | |
c34b1796 | 92 | { |
abe05a73 | 93 | debug!("binders(a={:?}, b={:?})", a, b); |
abe05a73 XL |
94 | |
95 | // When higher-ranked types are involved, computing the LUB is | |
96 | // very challenging, switch to invariance. This is obviously | |
97 | // overly conservative but works ok in practice. | |
a1dfa0c6 XL |
98 | self.relate_with_variance(ty::Variance::Invariant, a, b)?; |
99 | Ok(a.clone()) | |
1a4d82fc | 100 | } |
c34b1796 | 101 | } |
1a4d82fc | 102 | |
dc9dc135 XL |
103 | impl<'combine, 'infcx, 'tcx> LatticeDir<'infcx, 'tcx> for Glb<'combine, 'infcx, 'tcx> { |
104 | fn infcx(&self) -> &'infcx InferCtxt<'infcx, 'tcx> { | |
c34b1796 AL |
105 | self.fields.infcx |
106 | } | |
107 | ||
476ff2be SL |
108 | fn cause(&self) -> &ObligationCause<'tcx> { |
109 | &self.fields.trace.cause | |
110 | } | |
111 | ||
5bcae85e SL |
112 | fn relate_bound(&mut self, v: Ty<'tcx>, a: Ty<'tcx>, b: Ty<'tcx>) -> RelateResult<'tcx, ()> { |
113 | let mut sub = self.fields.sub(self.a_is_expected); | |
54a0048b SL |
114 | sub.relate(&v, &a)?; |
115 | sub.relate(&v, &b)?; | |
c34b1796 | 116 | Ok(()) |
1a4d82fc JJ |
117 | } |
118 | } |