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.
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.
11 use hir::def_id::DefId;
12 use ty::{self, Ty, TyCtxt};
15 use self::SimplifiedType::*;
17 /// See `simplify_type
18 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
19 pub enum SimplifiedType {
22 IntSimplifiedType(ast::IntTy),
23 UintSimplifiedType(ast::UintTy),
24 FloatSimplifiedType(ast::FloatTy),
25 AdtSimplifiedType(DefId),
30 TupleSimplifiedType(usize),
31 TraitSimplifiedType(DefId),
32 ClosureSimplifiedType(DefId),
33 AnonSimplifiedType(DefId),
34 FunctionSimplifiedType(usize),
35 ParameterSimplifiedType,
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.
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.
47 pub fn simplify_type<'a, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
49 can_simplify_params: bool)
50 -> Option<SimplifiedType>
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)),
58 ty::TyAdt(def, _) => Some(AdtSimplifiedType(def.did)),
59 ty::TyStr => Some(StrSimplifiedType),
60 ty::TyArray(..) | ty::TySlice(_) => Some(VecSimplifiedType),
61 ty::TyRawPtr(_) => Some(PtrSimplifiedType),
62 ty::TyTrait(ref trait_info) => {
63 Some(TraitSimplifiedType(trait_info.principal.def_id()))
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)
72 // treat like we would treat `Box`
73 match tcx.lang_items.require_owned_box() {
74 Ok(def_id) => Some(AdtSimplifiedType(def_id)),
75 Err(msg) => tcx.sess.fatal(&msg),
78 ty::TyClosure(def_id, _) => {
79 Some(ClosureSimplifiedType(def_id))
81 ty::TyNever => Some(NeverSimplifiedType),
82 ty::TyTuple(ref tys) => {
83 Some(TupleSimplifiedType(tys.len()))
85 ty::TyFnDef(.., ref f) | ty::TyFnPtr(ref f) => {
86 Some(FunctionSimplifiedType(f.sig.0.inputs.len()))
88 ty::TyProjection(_) | ty::TyParam(_) => {
89 if can_simplify_params {
90 // In normalized types, projections don't unify with
91 // anything. when lazy normalization happens, this
92 // will change. It would still be nice to have a way
93 // to deal with known-not-to-unify-with-anything
94 // projections (e.g. the likes of <__S as Encoder>::Error).
95 Some(ParameterSimplifiedType)
100 ty::TyAnon(def_id, _) => {
101 Some(AnonSimplifiedType(def_id))
103 ty::TyInfer(_) | ty::TyError => None,