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 super::{probe, MethodCallee};
13 use check::{FnCtxt, LvalueOp, callee};
14 use hir::def_id::DefId;
15 use rustc::ty::subst::Substs;
17 use rustc::ty::{self, LvaluePreference, NoPreference, PreferMutLvalue, Ty};
18 use rustc::ty::adjustment::{Adjustment, Adjust, AutoBorrow, OverloadedDeref};
19 use rustc::ty::fold::TypeFoldable;
20 use rustc::infer::{self, InferOk};
26 struct ConfirmContext<'a, 'gcx: 'a + 'tcx, 'tcx: 'a> {
27 fcx: &'a FnCtxt<'a, 'gcx, 'tcx>,
29 self_expr: &'gcx hir::Expr,
30 call_expr: &'gcx hir::Expr,
33 impl<'a, 'gcx, 'tcx> Deref for ConfirmContext<'a, 'gcx, 'tcx> {
34 type Target = FnCtxt<'a, 'gcx, 'tcx>;
35 fn deref(&self) -> &Self::Target {
40 impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
41 pub fn confirm_method(&self,
43 self_expr: &'gcx hir::Expr,
44 call_expr: &'gcx hir::Expr,
45 unadjusted_self_ty: Ty<'tcx>,
46 pick: probe::Pick<'tcx>,
47 supplied_method_types: Vec<Ty<'tcx>>)
48 -> MethodCallee<'tcx> {
49 debug!("confirm(unadjusted_self_ty={:?}, pick={:?}, supplied_method_types={:?})",
52 supplied_method_types);
54 let mut confirm_cx = ConfirmContext::new(self, span, self_expr, call_expr);
55 confirm_cx.confirm(unadjusted_self_ty, pick, supplied_method_types)
59 impl<'a, 'gcx, 'tcx> ConfirmContext<'a, 'gcx, 'tcx> {
60 fn new(fcx: &'a FnCtxt<'a, 'gcx, 'tcx>,
62 self_expr: &'gcx hir::Expr,
63 call_expr: &'gcx hir::Expr)
64 -> ConfirmContext<'a, 'gcx, 'tcx> {
74 unadjusted_self_ty: Ty<'tcx>,
75 pick: probe::Pick<'tcx>,
76 supplied_method_types: Vec<Ty<'tcx>>)
77 -> MethodCallee<'tcx> {
78 // Adjust the self expression the user provided and obtain the adjusted type.
79 let self_ty = self.adjust_self_ty(unadjusted_self_ty, &pick);
81 // Make sure nobody calls `drop()` explicitly.
82 self.enforce_illegal_method_limitations(&pick);
84 // Create substitutions for the method's type parameters.
85 let rcvr_substs = self.fresh_receiver_substs(self_ty, &pick);
86 let all_substs = self.instantiate_method_substs(&pick, supplied_method_types, rcvr_substs);
88 debug!("all_substs={:?}", all_substs);
90 // Create the final signature for the method, replacing late-bound regions.
91 let (method_sig, method_predicates) = self.instantiate_method_sig(&pick, all_substs);
93 // Unify the (adjusted) self type with what the method expects.
94 self.unify_receivers(self_ty, method_sig.inputs()[0]);
96 // Add any trait/regions obligations specified on the method's type parameters.
97 let method_ty = self.tcx.mk_fn_ptr(ty::Binder(method_sig));
98 self.add_obligations(method_ty, all_substs, &method_predicates);
100 // Create the final `MethodCallee`.
101 let callee = MethodCallee {
102 def_id: pick.item.def_id,
107 if let Some(hir::MutMutable) = pick.autoref {
108 self.convert_lvalue_derefs_to_mutable();
114 ///////////////////////////////////////////////////////////////////////////
117 fn adjust_self_ty(&mut self,
118 unadjusted_self_ty: Ty<'tcx>,
119 pick: &probe::Pick<'tcx>)
121 // Commit the autoderefs by calling `autoderef` again, but this
122 // time writing the results into the various tables.
123 let mut autoderef = self.autoderef(self.span, unadjusted_self_ty);
124 let (_, n) = autoderef.nth(pick.autoderefs).unwrap();
125 assert_eq!(n, pick.autoderefs);
127 let mut adjustments = autoderef.adjust_steps(LvaluePreference::NoPreference);
129 let mut target = autoderef.unambiguous_final_ty();
131 if let Some(mutbl) = pick.autoref {
132 let region = self.next_region_var(infer::Autoref(self.span));
133 target = self.tcx.mk_ref(region, ty::TypeAndMut {
137 adjustments.push(Adjustment {
138 kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)),
142 if let Some(unsize_target) = pick.unsize {
143 target = self.tcx.mk_ref(region, ty::TypeAndMut {
147 adjustments.push(Adjustment {
148 kind: Adjust::Unsize,
153 // No unsizing should be performed without autoref (at
154 // least during method dispach). This is because we
155 // currently only unsize `[T;N]` to `[T]`, and naturally
156 // that must occur being a reference.
157 assert!(pick.unsize.is_none());
160 autoderef.finalize();
162 // Write out the final adjustments.
163 self.apply_adjustments(self.self_expr, adjustments);
168 ///////////////////////////////////////////////////////////////////////////
171 /// Returns a set of substitutions for the method *receiver* where all type and region
172 /// parameters are instantiated with fresh variables. This substitution does not include any
173 /// parameters declared on the method itself.
175 /// Note that this substitution may include late-bound regions from the impl level. If so,
176 /// these are instantiated later in the `instantiate_method_sig` routine.
177 fn fresh_receiver_substs(&mut self,
179 pick: &probe::Pick<'tcx>)
180 -> &'tcx Substs<'tcx> {
182 probe::InherentImplPick => {
183 let impl_def_id = pick.item.container.id();
184 assert!(self.tcx.impl_trait_ref(impl_def_id).is_none(),
185 "impl {:?} is not an inherent impl",
187 self.impl_self_ty(self.span, impl_def_id).substs
190 probe::ObjectPick => {
191 let trait_def_id = pick.item.container.id();
192 self.extract_existential_trait_ref(self_ty, |this, object_ty, principal| {
193 // The object data has no entry for the Self
194 // Type. For the purposes of this method call, we
195 // substitute the object type itself. This
196 // wouldn't be a sound substitution in all cases,
197 // since each instance of the object type is a
198 // different existential and hence could match
199 // distinct types (e.g., if `Self` appeared as an
200 // argument type), but those cases have already
201 // been ruled out when we deemed the trait to be
203 let original_poly_trait_ref = principal.with_self_ty(this.tcx, object_ty);
204 let upcast_poly_trait_ref = this.upcast(original_poly_trait_ref, trait_def_id);
205 let upcast_trait_ref =
206 this.replace_late_bound_regions_with_fresh_var(&upcast_poly_trait_ref);
207 debug!("original_poly_trait_ref={:?} upcast_trait_ref={:?} target_trait={:?}",
208 original_poly_trait_ref,
211 upcast_trait_ref.substs
215 probe::ExtensionImplPick(impl_def_id) => {
216 // The method being invoked is the method as defined on the trait,
217 // so return the substitutions from the trait. Consider:
219 // impl<A,B,C> Trait<A,B> for Foo<C> { ... }
221 // If we instantiate A, B, and C with $A, $B, and $C
222 // respectively, then we want to return the type
223 // parameters from the trait ([$A,$B]), not those from
224 // the impl ([$A,$B,$C]) not the receiver type ([$C]).
225 let impl_polytype = self.impl_self_ty(self.span, impl_def_id);
227 self.instantiate_type_scheme(self.span,
228 impl_polytype.substs,
229 &self.tcx.impl_trait_ref(impl_def_id).unwrap());
230 impl_trait_ref.substs
233 probe::TraitPick => {
234 let trait_def_id = pick.item.container.id();
236 // Make a trait reference `$0 : Trait<$1...$n>`
237 // consisting entirely of type variables. Later on in
238 // the process we will unify the transformed-self-type
239 // of the method with the actual type in order to
240 // unify some of these variables.
241 self.fresh_substs_for_item(self.span, trait_def_id)
244 probe::WhereClausePick(ref poly_trait_ref) => {
245 // Where clauses can have bound regions in them. We need to instantiate
246 // those to convert from a poly-trait-ref to a trait-ref.
247 self.replace_late_bound_regions_with_fresh_var(&poly_trait_ref).substs
252 fn extract_existential_trait_ref<R, F>(&mut self, self_ty: Ty<'tcx>, mut closure: F) -> R
253 where F: FnMut(&mut ConfirmContext<'a, 'gcx, 'tcx>,
255 ty::PolyExistentialTraitRef<'tcx>)
258 // If we specified that this is an object method, then the
259 // self-type ought to be something that can be dereferenced to
260 // yield an object-type (e.g., `&Object` or `Box<Object>`
263 // FIXME: this feels, like, super dubious
265 .autoderef(self.span, self_ty)
266 .filter_map(|(ty, _)| {
268 ty::TyDynamic(ref data, ..) => data.principal().map(|p| closure(self, ty, p)),
275 "self-type `{}` for ObjectPick never dereferenced to an object",
280 fn instantiate_method_substs(&mut self,
281 pick: &probe::Pick<'tcx>,
282 mut supplied_method_types: Vec<Ty<'tcx>>,
283 substs: &Substs<'tcx>)
284 -> &'tcx Substs<'tcx> {
285 // Determine the values for the generic parameters of the method.
286 // If they were not explicitly supplied, just construct fresh
288 let num_supplied_types = supplied_method_types.len();
289 let method_generics = self.tcx.generics_of(pick.item.def_id);
290 let num_method_types = method_generics.types.len();
292 if num_supplied_types > 0 && num_supplied_types != num_method_types {
293 if num_method_types == 0 {
294 struct_span_err!(self.tcx.sess,
297 "does not take type parameters")
298 .span_label(self.span, "called with unneeded type parameters")
301 struct_span_err!(self.tcx.sess,
304 "incorrect number of type parameters given for this method: \
305 expected {}, found {}",
308 .span_label(self.span,
309 format!("Passed {} type argument{}, expected {}",
311 if num_supplied_types != 1 { "s" } else { "" },
315 supplied_method_types = vec![self.tcx.types.err; num_method_types];
318 // Create subst for early-bound lifetime parameters, combining
319 // parameters from the type and those from the method.
321 // FIXME -- permit users to manually specify lifetimes
322 let supplied_start = substs.len() + method_generics.regions.len();
323 Substs::for_item(self.tcx, pick.item.def_id, |def, _| {
324 let i = def.index as usize;
325 if i < substs.len() {
328 self.region_var_for_def(self.span, def)
330 }, |def, cur_substs| {
331 let i = def.index as usize;
332 if i < substs.len() {
334 } else if supplied_method_types.is_empty() {
335 self.type_var_for_def(self.span, def, cur_substs)
337 supplied_method_types[i - supplied_start]
342 fn unify_receivers(&mut self, self_ty: Ty<'tcx>, method_self_ty: Ty<'tcx>) {
343 match self.at(&self.misc(self.span), self.param_env).sup(method_self_ty, self_ty) {
344 Ok(InferOk { obligations, value: () }) => {
345 self.register_predicates(obligations);
349 "{} was a subtype of {} but now is not?",
356 ///////////////////////////////////////////////////////////////////////////
359 fn instantiate_method_sig(&mut self,
360 pick: &probe::Pick<'tcx>,
361 all_substs: &'tcx Substs<'tcx>)
362 -> (ty::FnSig<'tcx>, ty::InstantiatedPredicates<'tcx>) {
363 debug!("instantiate_method_sig(pick={:?}, all_substs={:?})",
367 // Instantiate the bounds on the method with the
368 // type/early-bound-regions substitutions performed. There can
369 // be no late-bound regions appearing here.
370 let def_id = pick.item.def_id;
371 let method_predicates = self.tcx.predicates_of(def_id)
372 .instantiate(self.tcx, all_substs);
373 let method_predicates = self.normalize_associated_types_in(self.span,
376 debug!("method_predicates after subst = {:?}", method_predicates);
378 let sig = self.tcx.type_of(def_id).fn_sig();
380 // Instantiate late-bound regions and substitute the trait
381 // parameters into the method type to get the actual method type.
383 // NB: Instantiate late-bound regions first so that
384 // `instantiate_type_scheme` can normalize associated types that
385 // may reference those regions.
386 let method_sig = self.replace_late_bound_regions_with_fresh_var(&sig);
387 debug!("late-bound lifetimes from method instantiated, method_sig={:?}",
390 let method_sig = self.instantiate_type_scheme(self.span, all_substs, &method_sig);
391 debug!("type scheme substituted, method_sig={:?}", method_sig);
393 (method_sig, method_predicates)
396 fn add_obligations(&mut self,
398 all_substs: &Substs<'tcx>,
399 method_predicates: &ty::InstantiatedPredicates<'tcx>) {
400 debug!("add_obligations: fty={:?} all_substs={:?} method_predicates={:?}",
405 self.add_obligations_for_parameters(traits::ObligationCause::misc(self.span, self.body_id),
408 // this is a projection from a trait reference, so we have to
409 // make sure that the trait reference inputs are well-formed.
410 self.add_wf_bounds(all_substs, self.call_expr);
412 // the function type must also be well-formed (this is not
413 // implied by the substs being well-formed because of inherent
414 // impls and late-bound regions - see issue #28609).
415 self.register_wf_obligation(fty, self.span, traits::MiscObligation);
418 ///////////////////////////////////////////////////////////////////////////
421 /// When we select a method with a mutable autoref, we have to go convert any
422 /// auto-derefs, indices, etc from `Deref` and `Index` into `DerefMut` and `IndexMut`
424 fn convert_lvalue_derefs_to_mutable(&self) {
425 // Gather up expressions we want to munge.
426 let mut exprs = Vec::new();
427 exprs.push(self.self_expr);
429 let last = exprs[exprs.len() - 1];
431 hir::ExprField(ref expr, _) |
432 hir::ExprTupField(ref expr, _) |
433 hir::ExprIndex(ref expr, _) |
434 hir::ExprUnary(hir::UnDeref, ref expr) => exprs.push(&expr),
439 debug!("convert_lvalue_derefs_to_mutable: exprs={:?}", exprs);
441 // Fix up autoderefs and derefs.
442 for (i, &expr) in exprs.iter().rev().enumerate() {
443 debug!("convert_lvalue_derefs_to_mutable: i={} expr={:?}", i, expr);
445 // Fix up the autoderefs. Autorefs can only occur immediately preceding
446 // overloaded lvalue ops, and will be fixed by them in order to get
447 // the correct region.
448 let mut source = self.node_ty(expr.id);
449 // Do not mutate adjustments in place, but rather take them,
450 // and replace them after mutating them, to avoid having the
451 // tables borrowed during (`deref_mut`) method resolution.
452 let previous_adjustments = self.tables.borrow_mut().adjustments.remove(&expr.id);
453 if let Some(mut adjustments) = previous_adjustments {
454 let pref = LvaluePreference::PreferMutLvalue;
455 for adjustment in &mut adjustments {
456 if let Adjust::Deref(Some(ref mut deref)) = adjustment.kind {
457 if let Some(ok) = self.try_overloaded_deref(expr.span, source, pref) {
458 let method = self.register_infer_ok_obligations(ok);
459 if let ty::TyRef(region, mt) = method.sig.output().sty {
460 *deref = OverloadedDeref {
467 source = adjustment.target;
469 self.tables.borrow_mut().adjustments.insert(expr.id, adjustments);
473 hir::ExprIndex(ref base_expr, ref index_expr) => {
474 let index_expr_ty = self.node_ty(index_expr.id);
475 self.convert_lvalue_op_to_mutable(
476 LvalueOp::Index, expr, base_expr, &[index_expr_ty]);
478 hir::ExprUnary(hir::UnDeref, ref base_expr) => {
479 self.convert_lvalue_op_to_mutable(
480 LvalueOp::Deref, expr, base_expr, &[]);
487 fn convert_lvalue_op_to_mutable(&self,
490 base_expr: &hir::Expr,
491 arg_tys: &[Ty<'tcx>])
493 debug!("convert_lvalue_op_to_mutable({:?}, {:?}, {:?}, {:?})",
494 op, expr, base_expr, arg_tys);
495 if !self.tables.borrow().is_method_call(expr) {
496 debug!("convert_lvalue_op_to_mutable - builtin, nothing to do");
500 let base_ty = self.tables.borrow().expr_adjustments(base_expr).last()
501 .map_or_else(|| self.node_ty(expr.id), |adj| adj.target);
502 let base_ty = self.resolve_type_vars_if_possible(&base_ty);
504 // Need to deref because overloaded lvalue ops take self by-reference.
505 let base_ty = base_ty.builtin_deref(false, NoPreference)
506 .expect("lvalue op takes something that is not a ref")
509 let method = self.try_overloaded_lvalue_op(
510 expr.span, base_ty, arg_tys, PreferMutLvalue, op);
511 let method = match method {
512 Some(ok) => self.register_infer_ok_obligations(ok),
513 None => return self.tcx.sess.delay_span_bug(expr.span, "re-trying op failed")
515 debug!("convert_lvalue_op_to_mutable: method={:?}", method);
516 self.write_method_call(expr.id, method);
518 let (region, mutbl) = if let ty::TyRef(r, mt) = method.sig.inputs()[0].sty {
521 span_bug!(expr.span, "input to lvalue op is not a ref?");
524 // Convert the autoref in the base expr to mutable with the correct
525 // region and mutability.
526 let base_expr_ty = self.node_ty(base_expr.id);
527 if let Some(adjustments) = self.tables.borrow_mut().adjustments.get_mut(&base_expr.id) {
528 let mut source = base_expr_ty;
529 for adjustment in &mut adjustments[..] {
530 if let Adjust::Borrow(AutoBorrow::Ref(..)) = adjustment.kind {
531 debug!("convert_lvalue_op_to_mutable: converting autoref {:?}", adjustment);
532 adjustment.kind = Adjust::Borrow(AutoBorrow::Ref(region, mutbl));
533 adjustment.target = self.tcx.mk_ref(region, ty::TypeAndMut {
538 source = adjustment.target;
541 // If we have an autoref followed by unsizing at the end, fix the unsize target.
542 match adjustments[..] {
543 [.., Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(..)), .. },
544 Adjustment { kind: Adjust::Unsize, ref mut target }] => {
545 *target = method.sig.inputs()[0];
552 ///////////////////////////////////////////////////////////////////////////
555 fn enforce_illegal_method_limitations(&self, pick: &probe::Pick) {
556 // Disallow calls to the method `drop` defined in the `Drop` trait.
557 match pick.item.container {
558 ty::TraitContainer(trait_def_id) => {
559 callee::check_legal_trait_for_method_call(self.tcx, self.span, trait_def_id)
561 ty::ImplContainer(..) => {}
566 source_trait_ref: ty::PolyTraitRef<'tcx>,
567 target_trait_def_id: DefId)
568 -> ty::PolyTraitRef<'tcx> {
569 let upcast_trait_refs = self.tcx
570 .upcast_choices(source_trait_ref.clone(), target_trait_def_id);
572 // must be exactly one trait ref or we'd get an ambig error etc
573 if upcast_trait_refs.len() != 1 {
575 "cannot uniquely upcast `{:?}` to `{:?}`: `{:?}`",
581 upcast_trait_refs.into_iter().next().unwrap()
584 fn replace_late_bound_regions_with_fresh_var<T>(&self, value: &ty::Binder<T>) -> T
585 where T: TypeFoldable<'tcx>
588 .replace_late_bound_regions_with_fresh_var(self.span, infer::FnCall, value)