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 //! Code for type-checking closure expressions.
13 use super::{check_fn, Expectation, FnCtxt};
16 use rustc::infer::type_variable::TypeVariableOrigin;
17 use rustc::ty::{self, ToPolyTraitRef, Ty};
23 impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
24 pub fn check_expr_closure(&self,
26 _capture: hir::CaptureClause,
27 decl: &'gcx hir::FnDecl,
29 expected: Expectation<'tcx>)
31 debug!("check_expr_closure(expr={:?},expected={:?})",
35 // It's always helpful for inference if we know the kind of
36 // closure sooner rather than later, so first examine the expected
37 // type, and see if can glean a closure kind from there.
38 let (expected_sig, expected_kind) = match expected.to_option(self) {
39 Some(ty) => self.deduce_expectations_from_expected_type(ty),
42 let body = self.tcx.hir.body(body_id);
43 self.check_closure(expr, expected_kind, decl, body, expected_sig)
46 fn check_closure(&self,
48 opt_kind: Option<ty::ClosureKind>,
49 decl: &'gcx hir::FnDecl,
50 body: &'gcx hir::Body,
51 expected_sig: Option<ty::FnSig<'tcx>>)
53 debug!("check_closure opt_kind={:?} expected_sig={:?}",
57 let expr_def_id = self.tcx.hir.local_def_id(expr.id);
58 let sig = AstConv::ty_of_closure(self,
59 hir::Unsafety::Normal,
64 // Create type variables (for now) to represent the transformed
65 // types of upvars. These will be unified during the upvar
66 // inference phase (`upvar.rs`).
67 let closure_type = self.tcx.mk_closure(expr_def_id,
68 self.parameter_environment.free_substs.extend_to(self.tcx, expr_def_id,
69 |_, _| span_bug!(expr.span, "closure has region param"),
70 |_, _| self.infcx.next_ty_var(TypeVariableOrigin::TransformedUpvar(expr.span))
74 debug!("check_closure: expr.id={:?} closure_type={:?}", expr.id, closure_type);
76 let extent = self.tcx.region_maps().call_site_extent(expr.id, body.value.id);
77 let fn_sig = self.tcx.liberate_late_bound_regions(extent, &sig);
78 let fn_sig = self.inh.normalize_associated_types_in(body.value.span,
79 body.value.id, &fn_sig);
81 check_fn(self, fn_sig, decl, expr.id, body);
83 // Tuple up the arguments and insert the resulting function type into
84 // the `closures` table.
85 let sig = sig.map_bound(|sig| self.tcx.mk_fn_sig(
86 iter::once(self.tcx.intern_tup(sig.inputs(), false)),
93 debug!("closure for {:?} --> sig={:?} opt_kind={:?}",
98 self.tables.borrow_mut().closure_tys.insert(expr.id, sig);
101 self.tables.borrow_mut().closure_kinds.insert(expr.id, kind);
109 fn deduce_expectations_from_expected_type
111 expected_ty: Ty<'tcx>)
112 -> (Option<ty::FnSig<'tcx>>, Option<ty::ClosureKind>) {
113 debug!("deduce_expectations_from_expected_type(expected_ty={:?})",
116 match expected_ty.sty {
117 ty::TyDynamic(ref object_type, ..) => {
118 let sig = object_type.projection_bounds()
120 let pb = pb.with_self_ty(self.tcx, self.tcx.types.err);
121 self.deduce_sig_from_projection(&pb)
124 let kind = object_type.principal()
125 .and_then(|p| self.tcx.lang_items.fn_trait_kind(p.def_id()));
128 ty::TyInfer(ty::TyVar(vid)) => self.deduce_expectations_from_obligations(vid),
133 fn deduce_expectations_from_obligations
135 expected_vid: ty::TyVid)
136 -> (Option<ty::FnSig<'tcx>>, Option<ty::ClosureKind>) {
137 let fulfillment_cx = self.fulfillment_cx.borrow();
138 // Here `expected_ty` is known to be a type inference variable.
140 let expected_sig = fulfillment_cx.pending_obligations()
142 .map(|obligation| &obligation.obligation)
143 .filter_map(|obligation| {
144 debug!("deduce_expectations_from_obligations: obligation.predicate={:?}",
145 obligation.predicate);
147 match obligation.predicate {
148 // Given a Projection predicate, we can potentially infer
149 // the complete signature.
150 ty::Predicate::Projection(ref proj_predicate) => {
151 let trait_ref = proj_predicate.to_poly_trait_ref();
152 self.self_type_matches_expected_vid(trait_ref, expected_vid)
153 .and_then(|_| self.deduce_sig_from_projection(proj_predicate))
160 // Even if we can't infer the full signature, we may be able to
161 // infer the kind. This can occur if there is a trait-reference
162 // like `F : Fn<A>`. Note that due to subtyping we could encounter
163 // many viable options, so pick the most restrictive.
164 let expected_kind = fulfillment_cx.pending_obligations()
166 .map(|obligation| &obligation.obligation)
167 .filter_map(|obligation| {
168 let opt_trait_ref = match obligation.predicate {
169 ty::Predicate::Projection(ref data) => Some(data.to_poly_trait_ref()),
170 ty::Predicate::Trait(ref data) => Some(data.to_poly_trait_ref()),
171 ty::Predicate::Equate(..) => None,
172 ty::Predicate::Subtype(..) => None,
173 ty::Predicate::RegionOutlives(..) => None,
174 ty::Predicate::TypeOutlives(..) => None,
175 ty::Predicate::WellFormed(..) => None,
176 ty::Predicate::ObjectSafe(..) => None,
178 // NB: This predicate is created by breaking down a
179 // `ClosureType: FnFoo()` predicate, where
180 // `ClosureType` represents some `TyClosure`. It can't
181 // possibly be referring to the current closure,
182 // because we haven't produced the `TyClosure` for
183 // this closure yet; this is exactly why the other
184 // code is looking for a self type of a unresolved
185 // inference variable.
186 ty::Predicate::ClosureKind(..) => None,
188 opt_trait_ref.and_then(|tr| self.self_type_matches_expected_vid(tr, expected_vid))
189 .and_then(|tr| self.tcx.lang_items.fn_trait_kind(tr.def_id()))
192 |best, cur| Some(best.map_or(cur, |best| cmp::min(best, cur))));
194 (expected_sig, expected_kind)
197 /// Given a projection like "<F as Fn(X)>::Result == Y", we can deduce
198 /// everything we need to know about a closure.
199 fn deduce_sig_from_projection(&self,
200 projection: &ty::PolyProjectionPredicate<'tcx>)
201 -> Option<ty::FnSig<'tcx>> {
204 debug!("deduce_sig_from_projection({:?})", projection);
206 let trait_ref = projection.to_poly_trait_ref();
208 if tcx.lang_items.fn_trait_kind(trait_ref.def_id()).is_none() {
212 let arg_param_ty = trait_ref.substs().type_at(1);
213 let arg_param_ty = self.resolve_type_vars_if_possible(&arg_param_ty);
214 debug!("deduce_sig_from_projection: arg_param_ty {:?}",
217 let input_tys = match arg_param_ty.sty {
218 ty::TyTuple(tys, _) => tys.into_iter(),
224 let ret_param_ty = projection.0.ty;
225 let ret_param_ty = self.resolve_type_vars_if_possible(&ret_param_ty);
226 debug!("deduce_sig_from_projection: ret_param_ty {:?}", ret_param_ty);
228 let fn_sig = self.tcx.mk_fn_sig(
232 hir::Unsafety::Normal,
235 debug!("deduce_sig_from_projection: fn_sig {:?}", fn_sig);
240 fn self_type_matches_expected_vid(&self,
241 trait_ref: ty::PolyTraitRef<'tcx>,
242 expected_vid: ty::TyVid)
243 -> Option<ty::PolyTraitRef<'tcx>> {
244 let self_ty = self.shallow_resolve(trait_ref.self_ty());
245 debug!("self_type_matches_expected_vid(trait_ref={:?}, self_ty={:?})",
249 ty::TyInfer(ty::TyVar(v)) if expected_vid == v => Some(trait_ref),