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1 | // Copyright 2014 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 | ||
54a0048b SL |
11 | use hir::def_id::DefId; |
12 | use ty::{self, Ty, TyCtxt}; | |
b039eaaf | 13 | use syntax::ast; |
1a4d82fc JJ |
14 | |
15 | use self::SimplifiedType::*; | |
16 | ||
17 | /// See `simplify_type | |
9cc50fc6 | 18 | #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)] |
1a4d82fc JJ |
19 | pub enum SimplifiedType { |
20 | BoolSimplifiedType, | |
21 | CharSimplifiedType, | |
b039eaaf SL |
22 | IntSimplifiedType(ast::IntTy), |
23 | UintSimplifiedType(ast::UintTy), | |
24 | FloatSimplifiedType(ast::FloatTy), | |
9e0c209e | 25 | AdtSimplifiedType(DefId), |
1a4d82fc | 26 | StrSimplifiedType, |
c30ab7b3 | 27 | ArraySimplifiedType, |
1a4d82fc | 28 | PtrSimplifiedType, |
5bcae85e | 29 | NeverSimplifiedType, |
c34b1796 | 30 | TupleSimplifiedType(usize), |
e9174d1e | 31 | TraitSimplifiedType(DefId), |
e9174d1e | 32 | ClosureSimplifiedType(DefId), |
5bcae85e | 33 | AnonSimplifiedType(DefId), |
c34b1796 | 34 | FunctionSimplifiedType(usize), |
1a4d82fc JJ |
35 | ParameterSimplifiedType, |
36 | } | |
37 | ||
38 | /// Tries to simplify a type by dropping type parameters, deref'ing away any reference types, etc. | |
39 | /// The idea is to get something simple that we can use to quickly decide if two types could unify | |
40 | /// during method lookup. | |
41 | /// | |
42 | /// If `can_simplify_params` is false, then we will fail to simplify type parameters entirely. This | |
43 | /// is useful when those type parameters would be instantiated with fresh type variables, since | |
44 | /// then we can't say much about whether two types would unify. Put another way, | |
45 | /// `can_simplify_params` should be true if type parameters appear free in `ty` and `false` if they | |
46 | /// are to be considered bound. | |
a7813a04 XL |
47 | pub fn simplify_type<'a, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>, |
48 | ty: Ty, | |
49 | can_simplify_params: bool) | |
50 | -> Option<SimplifiedType> | |
1a4d82fc JJ |
51 | { |
52 | match ty.sty { | |
62682a34 SL |
53 | ty::TyBool => Some(BoolSimplifiedType), |
54 | ty::TyChar => Some(CharSimplifiedType), | |
55 | ty::TyInt(int_type) => Some(IntSimplifiedType(int_type)), | |
56 | ty::TyUint(uint_type) => Some(UintSimplifiedType(uint_type)), | |
57 | ty::TyFloat(float_type) => Some(FloatSimplifiedType(float_type)), | |
9e0c209e | 58 | ty::TyAdt(def, _) => Some(AdtSimplifiedType(def.did)), |
62682a34 | 59 | ty::TyStr => Some(StrSimplifiedType), |
c30ab7b3 | 60 | ty::TyArray(..) | ty::TySlice(_) => Some(ArraySimplifiedType), |
62682a34 | 61 | ty::TyRawPtr(_) => Some(PtrSimplifiedType), |
476ff2be SL |
62 | ty::TyDynamic(ref trait_info, ..) => { |
63 | trait_info.principal().map(|p| TraitSimplifiedType(p.def_id())) | |
1a4d82fc | 64 | } |
62682a34 | 65 | ty::TyRef(_, mt) => { |
1a4d82fc JJ |
66 | // since we introduce auto-refs during method lookup, we |
67 | // just treat &T and T as equivalent from the point of | |
68 | // view of possibly unifying | |
69 | simplify_type(tcx, mt.ty, can_simplify_params) | |
70 | } | |
62682a34 | 71 | ty::TyClosure(def_id, _) => { |
85aaf69f | 72 | Some(ClosureSimplifiedType(def_id)) |
1a4d82fc | 73 | } |
5bcae85e | 74 | ty::TyNever => Some(NeverSimplifiedType), |
62682a34 | 75 | ty::TyTuple(ref tys) => { |
1a4d82fc JJ |
76 | Some(TupleSimplifiedType(tys.len())) |
77 | } | |
9e0c209e | 78 | ty::TyFnDef(.., ref f) | ty::TyFnPtr(ref f) => { |
476ff2be | 79 | Some(FunctionSimplifiedType(f.sig.skip_binder().inputs().len())) |
1a4d82fc | 80 | } |
e9174d1e | 81 | ty::TyProjection(_) | ty::TyParam(_) => { |
1a4d82fc | 82 | if can_simplify_params { |
e9174d1e SL |
83 | // In normalized types, projections don't unify with |
84 | // anything. when lazy normalization happens, this | |
85 | // will change. It would still be nice to have a way | |
86 | // to deal with known-not-to-unify-with-anything | |
87 | // projections (e.g. the likes of <__S as Encoder>::Error). | |
1a4d82fc JJ |
88 | Some(ParameterSimplifiedType) |
89 | } else { | |
90 | None | |
91 | } | |
92 | } | |
5bcae85e SL |
93 | ty::TyAnon(def_id, _) => { |
94 | Some(AnonSimplifiedType(def_id)) | |
95 | } | |
62682a34 | 96 | ty::TyInfer(_) | ty::TyError => None, |
1a4d82fc JJ |
97 | } |
98 | } |