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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 | ||
e9174d1e | 11 | use middle::def_id::DefId; |
1a4d82fc | 12 | use middle::ty::{self, Ty}; |
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), | |
e9174d1e | 25 | EnumSimplifiedType(DefId), |
1a4d82fc JJ |
26 | StrSimplifiedType, |
27 | VecSimplifiedType, | |
28 | PtrSimplifiedType, | |
c34b1796 | 29 | TupleSimplifiedType(usize), |
e9174d1e SL |
30 | TraitSimplifiedType(DefId), |
31 | StructSimplifiedType(DefId), | |
32 | ClosureSimplifiedType(DefId), | |
c34b1796 | 33 | FunctionSimplifiedType(usize), |
1a4d82fc JJ |
34 | ParameterSimplifiedType, |
35 | } | |
36 | ||
37 | /// Tries to simplify a type by dropping type parameters, deref'ing away any reference types, etc. | |
38 | /// The idea is to get something simple that we can use to quickly decide if two types could unify | |
39 | /// during method lookup. | |
40 | /// | |
41 | /// If `can_simplify_params` is false, then we will fail to simplify type parameters entirely. This | |
42 | /// is useful when those type parameters would be instantiated with fresh type variables, since | |
43 | /// then we can't say much about whether two types would unify. Put another way, | |
44 | /// `can_simplify_params` should be true if type parameters appear free in `ty` and `false` if they | |
45 | /// are to be considered bound. | |
46 | pub fn simplify_type(tcx: &ty::ctxt, | |
47 | ty: Ty, | |
48 | can_simplify_params: bool) | |
49 | -> Option<SimplifiedType> | |
50 | { | |
51 | match ty.sty { | |
62682a34 SL |
52 | ty::TyBool => Some(BoolSimplifiedType), |
53 | ty::TyChar => Some(CharSimplifiedType), | |
54 | ty::TyInt(int_type) => Some(IntSimplifiedType(int_type)), | |
55 | ty::TyUint(uint_type) => Some(UintSimplifiedType(uint_type)), | |
56 | ty::TyFloat(float_type) => Some(FloatSimplifiedType(float_type)), | |
e9174d1e | 57 | ty::TyEnum(def, _) => Some(EnumSimplifiedType(def.did)), |
62682a34 SL |
58 | ty::TyStr => Some(StrSimplifiedType), |
59 | ty::TyArray(..) | ty::TySlice(_) => Some(VecSimplifiedType), | |
60 | ty::TyRawPtr(_) => Some(PtrSimplifiedType), | |
61 | ty::TyTrait(ref trait_info) => { | |
1a4d82fc JJ |
62 | Some(TraitSimplifiedType(trait_info.principal_def_id())) |
63 | } | |
e9174d1e SL |
64 | ty::TyStruct(def, _) => { |
65 | Some(StructSimplifiedType(def.did)) | |
1a4d82fc | 66 | } |
62682a34 | 67 | ty::TyRef(_, mt) => { |
1a4d82fc JJ |
68 | // since we introduce auto-refs during method lookup, we |
69 | // just treat &T and T as equivalent from the point of | |
70 | // view of possibly unifying | |
71 | simplify_type(tcx, mt.ty, can_simplify_params) | |
72 | } | |
62682a34 | 73 | ty::TyBox(_) => { |
1a4d82fc | 74 | // treat like we would treat `Box` |
c1a9b12d SL |
75 | match tcx.lang_items.require_owned_box() { |
76 | Ok(def_id) => Some(StructSimplifiedType(def_id)), | |
77 | Err(msg) => tcx.sess.fatal(&msg), | |
78 | } | |
1a4d82fc | 79 | } |
62682a34 | 80 | ty::TyClosure(def_id, _) => { |
85aaf69f | 81 | Some(ClosureSimplifiedType(def_id)) |
1a4d82fc | 82 | } |
62682a34 | 83 | ty::TyTuple(ref tys) => { |
1a4d82fc JJ |
84 | Some(TupleSimplifiedType(tys.len())) |
85 | } | |
62682a34 | 86 | ty::TyBareFn(_, ref f) => { |
1a4d82fc JJ |
87 | Some(FunctionSimplifiedType(f.sig.0.inputs.len())) |
88 | } | |
e9174d1e | 89 | ty::TyProjection(_) | ty::TyParam(_) => { |
1a4d82fc | 90 | if can_simplify_params { |
e9174d1e SL |
91 | // In normalized types, projections don't unify with |
92 | // anything. when lazy normalization happens, this | |
93 | // will change. It would still be nice to have a way | |
94 | // to deal with known-not-to-unify-with-anything | |
95 | // projections (e.g. the likes of <__S as Encoder>::Error). | |
1a4d82fc JJ |
96 | Some(ParameterSimplifiedType) |
97 | } else { | |
98 | None | |
99 | } | |
100 | } | |
62682a34 | 101 | ty::TyInfer(_) | ty::TyError => None, |
1a4d82fc JJ |
102 | } |
103 | } |