1 // Copyright 2016 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.
13 use super::{FnCtxt, LvalueOp}
;
14 use super::method
::MethodCallee
;
16 use rustc
::infer
::InferOk
;
18 use rustc
::ty
::{self, Ty, TraitRef}
;
19 use rustc
::ty
::{ToPredicate, TypeFoldable}
;
20 use rustc
::ty
::{LvaluePreference, NoPreference}
;
21 use rustc
::ty
::adjustment
::{Adjustment, Adjust, OverloadedDeref}
;
24 use syntax
::symbol
::Symbol
;
28 #[derive(Copy, Clone, Debug)]
34 pub struct Autoderef
<'a
, 'gcx
: 'tcx
, 'tcx
: 'a
> {
35 fcx
: &'a FnCtxt
<'a
, 'gcx
, 'tcx
>,
36 steps
: Vec
<(Ty
<'tcx
>, AutoderefKind
)>,
38 obligations
: Vec
<traits
::PredicateObligation
<'tcx
>>,
43 impl<'a
, 'gcx
, 'tcx
> Iterator
for Autoderef
<'a
, 'gcx
, 'tcx
> {
44 type Item
= (Ty
<'tcx
>, usize);
46 fn next(&mut self) -> Option
<Self::Item
> {
47 let tcx
= self.fcx
.tcx
;
49 debug
!("autoderef: steps={:?}, cur_ty={:?}",
53 self.at_start
= false;
54 debug
!("autoderef stage #0 is {:?}", self.cur_ty
);
55 return Some((self.cur_ty
, 0));
58 if self.steps
.len() == tcx
.sess
.recursion_limit
.get() {
59 // We've reached the recursion limit, error gracefully.
60 let suggested_limit
= tcx
.sess
.recursion_limit
.get() * 2;
61 struct_span_err
!(tcx
.sess
,
64 "reached the recursion limit while auto-dereferencing {:?}",
66 .span_label(self.span
, "deref recursion limit reached")
68 "consider adding a `#[recursion_limit=\"{}\"]` attribute to your crate",
74 if self.cur_ty
.is_ty_var() {
78 // Otherwise, deref if type is derefable:
79 let (kind
, new_ty
) = if let Some(mt
) = self.cur_ty
.builtin_deref(false, NoPreference
) {
80 (AutoderefKind
::Builtin
, mt
.ty
)
82 match self.overloaded_deref_ty(self.cur_ty
) {
83 Some(ty
) => (AutoderefKind
::Overloaded
, ty
),
88 if new_ty
.references_error() {
92 self.steps
.push((self.cur_ty
, kind
));
93 debug
!("autoderef stage #{:?} is {:?} from {:?}",
99 Some((self.cur_ty
, self.steps
.len()))
103 impl<'a
, 'gcx
, 'tcx
> Autoderef
<'a
, 'gcx
, 'tcx
> {
104 fn overloaded_deref_ty(&mut self, ty
: Ty
<'tcx
>) -> Option
<Ty
<'tcx
>> {
105 debug
!("overloaded_deref_ty({:?})", ty
);
107 let tcx
= self.fcx
.tcx();
110 let trait_ref
= TraitRef
{
111 def_id
: match tcx
.lang_items
.deref_trait() {
115 substs
: tcx
.mk_substs_trait(self.cur_ty
, &[]),
118 let cause
= traits
::ObligationCause
::misc(self.span
, self.fcx
.body_id
);
120 let mut selcx
= traits
::SelectionContext
::new(self.fcx
);
121 let obligation
= traits
::Obligation
::new(cause
.clone(),
123 trait_ref
.to_predicate());
124 if !selcx
.evaluate_obligation(&obligation
) {
125 debug
!("overloaded_deref_ty: cannot match obligation");
129 let normalized
= traits
::normalize_projection_type(&mut selcx
,
131 ty
::ProjectionTy
::from_ref_and_name(
134 Symbol
::intern("Target"),
139 debug
!("overloaded_deref_ty({:?}) = {:?}", ty
, normalized
);
140 self.obligations
.extend(normalized
.obligations
);
142 Some(self.fcx
.resolve_type_vars_if_possible(&normalized
.value
))
145 /// Returns the final type, generating an error if it is an
146 /// unresolved inference variable.
147 pub fn unambiguous_final_ty(&self) -> Ty
<'tcx
> {
148 self.fcx
.structurally_resolved_type(self.span
, self.cur_ty
)
151 /// Returns the final type we ended up with, which may well be an
152 /// inference variable (we will resolve it first, if possible).
153 pub fn maybe_ambiguous_final_ty(&self) -> Ty
<'tcx
> {
154 self.fcx
.resolve_type_vars_if_possible(&self.cur_ty
)
157 pub fn step_count(&self) -> usize {
161 /// Returns the adjustment steps.
162 pub fn adjust_steps(&self, pref
: LvaluePreference
)
163 -> Vec
<Adjustment
<'tcx
>> {
164 self.fcx
.register_infer_ok_obligations(self.adjust_steps_as_infer_ok(pref
))
167 pub fn adjust_steps_as_infer_ok(&self, pref
: LvaluePreference
)
168 -> InferOk
<'tcx
, Vec
<Adjustment
<'tcx
>>> {
169 let mut obligations
= vec
![];
170 let targets
= self.steps
.iter().skip(1).map(|&(ty
, _
)| ty
)
171 .chain(iter
::once(self.cur_ty
));
172 let steps
: Vec
<_
> = self.steps
.iter().map(|&(source
, kind
)| {
173 if let AutoderefKind
::Overloaded
= kind
{
174 self.fcx
.try_overloaded_deref(self.span
, source
, pref
)
175 .and_then(|InferOk { value: method, obligations: o }
| {
176 obligations
.extend(o
);
177 if let ty
::TyRef(region
, mt
) = method
.sig
.output().sty
{
178 Some(OverloadedDeref
{
189 }).zip(targets
).map(|(autoderef
, target
)| {
191 kind
: Adjust
::Deref(autoderef
),
202 pub fn finalize(self) {
204 fcx
.register_predicates(self.into_obligations());
207 pub fn into_obligations(self) -> Vec
<traits
::PredicateObligation
<'tcx
>> {
212 impl<'a
, 'gcx
, 'tcx
> FnCtxt
<'a
, 'gcx
, 'tcx
> {
213 pub fn autoderef(&'a
self, span
: Span
, base_ty
: Ty
<'tcx
>) -> Autoderef
<'a
, 'gcx
, 'tcx
> {
217 cur_ty
: self.resolve_type_vars_if_possible(&base_ty
),
224 pub fn try_overloaded_deref(&self,
227 pref
: LvaluePreference
)
228 -> Option
<InferOk
<'tcx
, MethodCallee
<'tcx
>>> {
229 self.try_overloaded_lvalue_op(span
, base_ty
, &[], pref
, LvalueOp
::Deref
)