99 lines
3.7 KiB
Rust
99 lines
3.7 KiB
Rust
// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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use middle::ty::{self, Ty};
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use syntax::ast;
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use self::SimplifiedType::*;
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/// See `simplify_type
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#[derive(Clone, Copy, PartialEq, Eq, Hash)]
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pub enum SimplifiedType {
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BoolSimplifiedType,
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CharSimplifiedType,
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IntSimplifiedType(ast::IntTy),
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UintSimplifiedType(ast::UintTy),
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FloatSimplifiedType(ast::FloatTy),
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EnumSimplifiedType(ast::DefId),
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StrSimplifiedType,
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VecSimplifiedType,
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PtrSimplifiedType,
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TupleSimplifiedType(uint),
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TraitSimplifiedType(ast::DefId),
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StructSimplifiedType(ast::DefId),
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ClosureSimplifiedType(ast::DefId),
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FunctionSimplifiedType(uint),
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ParameterSimplifiedType,
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}
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/// Tries to simplify a type by dropping type parameters, deref'ing away any reference types, etc.
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/// The idea is to get something simple that we can use to quickly decide if two types could unify
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/// during method lookup.
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///
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/// If `can_simplify_params` is false, then we will fail to simplify type parameters entirely. This
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/// is useful when those type parameters would be instantiated with fresh type variables, since
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/// then we can't say much about whether two types would unify. Put another way,
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/// `can_simplify_params` should be true if type parameters appear free in `ty` and `false` if they
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/// are to be considered bound.
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pub fn simplify_type(tcx: &ty::ctxt,
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ty: Ty,
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can_simplify_params: bool)
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-> Option<SimplifiedType>
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{
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match ty.sty {
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ty::ty_bool => Some(BoolSimplifiedType),
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ty::ty_char => Some(CharSimplifiedType),
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ty::ty_int(int_type) => Some(IntSimplifiedType(int_type)),
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ty::ty_uint(uint_type) => Some(UintSimplifiedType(uint_type)),
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ty::ty_float(float_type) => Some(FloatSimplifiedType(float_type)),
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ty::ty_enum(def_id, _) => Some(EnumSimplifiedType(def_id)),
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ty::ty_str => Some(StrSimplifiedType),
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ty::ty_vec(..) => Some(VecSimplifiedType),
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ty::ty_ptr(_) => Some(PtrSimplifiedType),
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ty::ty_trait(ref trait_info) => {
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Some(TraitSimplifiedType(trait_info.principal_def_id()))
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}
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ty::ty_struct(def_id, _) => {
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Some(StructSimplifiedType(def_id))
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}
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ty::ty_rptr(_, mt) => {
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// since we introduce auto-refs during method lookup, we
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// just treat &T and T as equivalent from the point of
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// view of possibly unifying
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simplify_type(tcx, mt.ty, can_simplify_params)
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}
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ty::ty_uniq(_) => {
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// treat like we would treat `Box`
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let def_id = tcx.lang_items.owned_box().unwrap();
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Some(StructSimplifiedType(def_id))
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}
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ty::ty_closure(def_id, _) => {
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Some(ClosureSimplifiedType(def_id))
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}
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ty::ty_tup(ref tys) => {
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Some(TupleSimplifiedType(tys.len()))
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}
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ty::ty_bare_fn(_, ref f) => {
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Some(FunctionSimplifiedType(f.sig.0.inputs.len()))
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}
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ty::ty_projection(_) => {
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None
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}
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ty::ty_param(_) => {
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if can_simplify_params {
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Some(ParameterSimplifiedType)
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} else {
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None
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}
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}
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ty::ty_infer(_) | ty::ty_err => None,
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}
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}
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