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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 | ||
11 | use middle::ty::{self, Ty}; | |
12 | use syntax::ast; | |
13 | ||
14 | use self::SimplifiedType::*; | |
15 | ||
16 | /// See `simplify_type | |
17 | #[derive(Clone, Copy, PartialEq, Eq, Hash)] | |
18 | pub enum SimplifiedType { | |
19 | BoolSimplifiedType, | |
20 | CharSimplifiedType, | |
21 | IntSimplifiedType(ast::IntTy), | |
22 | UintSimplifiedType(ast::UintTy), | |
23 | FloatSimplifiedType(ast::FloatTy), | |
24 | EnumSimplifiedType(ast::DefId), | |
25 | StrSimplifiedType, | |
26 | VecSimplifiedType, | |
27 | PtrSimplifiedType, | |
c34b1796 | 28 | TupleSimplifiedType(usize), |
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29 | TraitSimplifiedType(ast::DefId), |
30 | StructSimplifiedType(ast::DefId), | |
85aaf69f | 31 | ClosureSimplifiedType(ast::DefId), |
c34b1796 | 32 | FunctionSimplifiedType(usize), |
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33 | ParameterSimplifiedType, |
34 | } | |
35 | ||
36 | /// Tries to simplify a type by dropping type parameters, deref'ing away any reference types, etc. | |
37 | /// The idea is to get something simple that we can use to quickly decide if two types could unify | |
38 | /// during method lookup. | |
39 | /// | |
40 | /// If `can_simplify_params` is false, then we will fail to simplify type parameters entirely. This | |
41 | /// is useful when those type parameters would be instantiated with fresh type variables, since | |
42 | /// then we can't say much about whether two types would unify. Put another way, | |
43 | /// `can_simplify_params` should be true if type parameters appear free in `ty` and `false` if they | |
44 | /// are to be considered bound. | |
45 | pub fn simplify_type(tcx: &ty::ctxt, | |
46 | ty: Ty, | |
47 | can_simplify_params: bool) | |
48 | -> Option<SimplifiedType> | |
49 | { | |
50 | match ty.sty { | |
62682a34 SL |
51 | ty::TyBool => Some(BoolSimplifiedType), |
52 | ty::TyChar => Some(CharSimplifiedType), | |
53 | ty::TyInt(int_type) => Some(IntSimplifiedType(int_type)), | |
54 | ty::TyUint(uint_type) => Some(UintSimplifiedType(uint_type)), | |
55 | ty::TyFloat(float_type) => Some(FloatSimplifiedType(float_type)), | |
56 | ty::TyEnum(def_id, _) => Some(EnumSimplifiedType(def_id)), | |
57 | ty::TyStr => Some(StrSimplifiedType), | |
58 | ty::TyArray(..) | ty::TySlice(_) => Some(VecSimplifiedType), | |
59 | ty::TyRawPtr(_) => Some(PtrSimplifiedType), | |
60 | ty::TyTrait(ref trait_info) => { | |
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61 | Some(TraitSimplifiedType(trait_info.principal_def_id())) |
62 | } | |
62682a34 | 63 | ty::TyStruct(def_id, _) => { |
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64 | Some(StructSimplifiedType(def_id)) |
65 | } | |
62682a34 | 66 | ty::TyRef(_, mt) => { |
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67 | // since we introduce auto-refs during method lookup, we |
68 | // just treat &T and T as equivalent from the point of | |
69 | // view of possibly unifying | |
70 | simplify_type(tcx, mt.ty, can_simplify_params) | |
71 | } | |
62682a34 | 72 | ty::TyBox(_) => { |
1a4d82fc | 73 | // treat like we would treat `Box` |
c1a9b12d SL |
74 | match tcx.lang_items.require_owned_box() { |
75 | Ok(def_id) => Some(StructSimplifiedType(def_id)), | |
76 | Err(msg) => tcx.sess.fatal(&msg), | |
77 | } | |
1a4d82fc | 78 | } |
62682a34 | 79 | ty::TyClosure(def_id, _) => { |
85aaf69f | 80 | Some(ClosureSimplifiedType(def_id)) |
1a4d82fc | 81 | } |
62682a34 | 82 | ty::TyTuple(ref tys) => { |
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83 | Some(TupleSimplifiedType(tys.len())) |
84 | } | |
62682a34 | 85 | ty::TyBareFn(_, ref f) => { |
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86 | Some(FunctionSimplifiedType(f.sig.0.inputs.len())) |
87 | } | |
62682a34 | 88 | ty::TyProjection(_) => { |
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89 | None |
90 | } | |
62682a34 | 91 | ty::TyParam(_) => { |
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92 | if can_simplify_params { |
93 | Some(ParameterSimplifiedType) | |
94 | } else { | |
95 | None | |
96 | } | |
97 | } | |
62682a34 | 98 | ty::TyInfer(_) | ty::TyError => None, |
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99 | } |
100 | } |