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};
14 use check::{FnCtxt, LvalueOp, callee};
15 use hir::def_id::DefId;
16 use rustc::ty::subst::Substs;
18 use rustc::ty::{self, LvaluePreference, NoPreference, PreferMutLvalue, Ty};
19 use rustc::ty::adjustment::{Adjustment, Adjust, AutoBorrow, OverloadedDeref};
20 use rustc::ty::fold::TypeFoldable;
21 use rustc::infer::{self, InferOk};
27 struct ConfirmContext<'a, 'gcx: 'a + 'tcx, 'tcx: 'a> {
28 fcx: &'a FnCtxt<'a, 'gcx, 'tcx>,
30 self_expr: &'gcx hir::Expr,
31 call_expr: &'gcx hir::Expr,
34 impl<'a, 'gcx, 'tcx> Deref for ConfirmContext<'a, 'gcx, 'tcx> {
35 type Target = FnCtxt<'a, 'gcx, 'tcx>;
36 fn deref(&self) -> &Self::Target {
41 impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
42 pub fn confirm_method(&self,
44 self_expr: &'gcx hir::Expr,
45 call_expr: &'gcx hir::Expr,
46 unadjusted_self_ty: Ty<'tcx>,
47 pick: probe::Pick<'tcx>,
48 segment: &hir::PathSegment)
49 -> MethodCallee<'tcx> {
50 debug!("confirm(unadjusted_self_ty={:?}, pick={:?}, generic_args={:?})",
55 let mut confirm_cx = ConfirmContext::new(self, span, self_expr, call_expr);
56 confirm_cx.confirm(unadjusted_self_ty, pick, segment)
60 impl<'a, 'gcx, 'tcx> ConfirmContext<'a, 'gcx, 'tcx> {
61 fn new(fcx: &'a FnCtxt<'a, 'gcx, 'tcx>,
63 self_expr: &'gcx hir::Expr,
64 call_expr: &'gcx hir::Expr)
65 -> ConfirmContext<'a, 'gcx, 'tcx> {
75 unadjusted_self_ty: Ty<'tcx>,
76 pick: probe::Pick<'tcx>,
77 segment: &hir::PathSegment)
78 -> MethodCallee<'tcx> {
79 // Adjust the self expression the user provided and obtain the adjusted type.
80 let self_ty = self.adjust_self_ty(unadjusted_self_ty, &pick);
82 // Make sure nobody calls `drop()` explicitly.
83 self.enforce_illegal_method_limitations(&pick);
85 // Create substitutions for the method's type parameters.
86 let rcvr_substs = self.fresh_receiver_substs(self_ty, &pick);
87 let all_substs = self.instantiate_method_substs(&pick, segment, rcvr_substs);
89 debug!("all_substs={:?}", all_substs);
91 // Create the final signature for the method, replacing late-bound regions.
92 let (method_sig, method_predicates) = self.instantiate_method_sig(&pick, all_substs);
94 // Unify the (adjusted) self type with what the method expects.
95 self.unify_receivers(self_ty, method_sig.inputs()[0]);
97 // Add any trait/regions obligations specified on the method's type parameters.
98 let method_ty = self.tcx.mk_fn_ptr(ty::Binder(method_sig));
99 self.add_obligations(method_ty, all_substs, &method_predicates);
101 // Create the final `MethodCallee`.
102 let callee = MethodCallee {
103 def_id: pick.item.def_id,
108 if let Some(hir::MutMutable) = pick.autoref {
109 self.convert_lvalue_derefs_to_mutable();
115 ///////////////////////////////////////////////////////////////////////////
118 fn adjust_self_ty(&mut self,
119 unadjusted_self_ty: Ty<'tcx>,
120 pick: &probe::Pick<'tcx>)
122 // Commit the autoderefs by calling `autoderef` again, but this
123 // time writing the results into the various tables.
124 let mut autoderef = self.autoderef(self.span, unadjusted_self_ty);
125 let (_, n) = autoderef.nth(pick.autoderefs).unwrap();
126 assert_eq!(n, pick.autoderefs);
128 let mut adjustments = autoderef.adjust_steps(LvaluePreference::NoPreference);
130 let mut target = autoderef.unambiguous_final_ty();
132 if let Some(mutbl) = pick.autoref {
133 let region = self.next_region_var(infer::Autoref(self.span));
134 target = self.tcx.mk_ref(region, ty::TypeAndMut {
138 adjustments.push(Adjustment {
139 kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)),
143 if let Some(unsize_target) = pick.unsize {
144 target = self.tcx.mk_ref(region, ty::TypeAndMut {
148 adjustments.push(Adjustment {
149 kind: Adjust::Unsize,
154 // No unsizing should be performed without autoref (at
155 // least during method dispach). This is because we
156 // currently only unsize `[T;N]` to `[T]`, and naturally
157 // that must occur being a reference.
158 assert!(pick.unsize.is_none());
161 autoderef.finalize();
163 // Write out the final adjustments.
164 self.apply_adjustments(self.self_expr, adjustments);
169 ///////////////////////////////////////////////////////////////////////////
172 /// Returns a set of substitutions for the method *receiver* where all type and region
173 /// parameters are instantiated with fresh variables. This substitution does not include any
174 /// parameters declared on the method itself.
176 /// Note that this substitution may include late-bound regions from the impl level. If so,
177 /// these are instantiated later in the `instantiate_method_sig` routine.
178 fn fresh_receiver_substs(&mut self,
180 pick: &probe::Pick<'tcx>)
181 -> &'tcx Substs<'tcx> {
183 probe::InherentImplPick => {
184 let impl_def_id = pick.item.container.id();
185 assert!(self.tcx.impl_trait_ref(impl_def_id).is_none(),
186 "impl {:?} is not an inherent impl",
188 self.impl_self_ty(self.span, impl_def_id).substs
191 probe::ObjectPick => {
192 let trait_def_id = pick.item.container.id();
193 self.extract_existential_trait_ref(self_ty, |this, object_ty, principal| {
194 // The object data has no entry for the Self
195 // Type. For the purposes of this method call, we
196 // substitute the object type itself. This
197 // wouldn't be a sound substitution in all cases,
198 // since each instance of the object type is a
199 // different existential and hence could match
200 // distinct types (e.g., if `Self` appeared as an
201 // argument type), but those cases have already
202 // been ruled out when we deemed the trait to be
204 let original_poly_trait_ref = principal.with_self_ty(this.tcx, object_ty);
205 let upcast_poly_trait_ref = this.upcast(original_poly_trait_ref, trait_def_id);
206 let upcast_trait_ref =
207 this.replace_late_bound_regions_with_fresh_var(&upcast_poly_trait_ref);
208 debug!("original_poly_trait_ref={:?} upcast_trait_ref={:?} target_trait={:?}",
209 original_poly_trait_ref,
212 upcast_trait_ref.substs
216 probe::ExtensionImplPick(impl_def_id) => {
217 // The method being invoked is the method as defined on the trait,
218 // so return the substitutions from the trait. Consider:
220 // impl<A,B,C> Trait<A,B> for Foo<C> { ... }
222 // If we instantiate A, B, and C with $A, $B, and $C
223 // respectively, then we want to return the type
224 // parameters from the trait ([$A,$B]), not those from
225 // the impl ([$A,$B,$C]) not the receiver type ([$C]).
226 let impl_polytype = self.impl_self_ty(self.span, impl_def_id);
228 self.instantiate_type_scheme(self.span,
229 impl_polytype.substs,
230 &self.tcx.impl_trait_ref(impl_def_id).unwrap());
231 impl_trait_ref.substs
234 probe::TraitPick => {
235 let trait_def_id = pick.item.container.id();
237 // Make a trait reference `$0 : Trait<$1...$n>`
238 // consisting entirely of type variables. Later on in
239 // the process we will unify the transformed-self-type
240 // of the method with the actual type in order to
241 // unify some of these variables.
242 self.fresh_substs_for_item(self.span, trait_def_id)
245 probe::WhereClausePick(ref poly_trait_ref) => {
246 // Where clauses can have bound regions in them. We need to instantiate
247 // those to convert from a poly-trait-ref to a trait-ref.
248 self.replace_late_bound_regions_with_fresh_var(&poly_trait_ref).substs
253 fn extract_existential_trait_ref<R, F>(&mut self, self_ty: Ty<'tcx>, mut closure: F) -> R
254 where F: FnMut(&mut ConfirmContext<'a, 'gcx, 'tcx>,
256 ty::PolyExistentialTraitRef<'tcx>)
259 // If we specified that this is an object method, then the
260 // self-type ought to be something that can be dereferenced to
261 // yield an object-type (e.g., `&Object` or `Box<Object>`
264 // FIXME: this feels, like, super dubious
266 .autoderef(self.span, self_ty)
267 .filter_map(|(ty, _)| {
269 ty::TyDynamic(ref data, ..) => data.principal().map(|p| closure(self, ty, p)),
276 "self-type `{}` for ObjectPick never dereferenced to an object",
281 fn instantiate_method_substs(&mut self,
282 pick: &probe::Pick<'tcx>,
283 segment: &hir::PathSegment,
284 parent_substs: &Substs<'tcx>)
285 -> &'tcx Substs<'tcx> {
286 // Determine the values for the generic parameters of the method.
287 // If they were not explicitly supplied, just construct fresh
289 let method_generics = self.tcx.generics_of(pick.item.def_id);
290 let mut fn_segment = Some((segment, method_generics));
291 self.fcx.check_path_parameter_count(self.span, &mut fn_segment, true);
293 // Create subst for early-bound lifetime parameters, combining
294 // parameters from the type and those from the method.
295 let (supplied_types, supplied_lifetimes) = match segment.parameters {
296 hir::AngleBracketedParameters(ref data) => (&data.types, &data.lifetimes),
297 _ => bug!("unexpected generic arguments: {:?}", segment.parameters),
299 assert_eq!(method_generics.parent_count(), parent_substs.len());
300 Substs::for_item(self.tcx, pick.item.def_id, |def, _| {
301 let i = def.index as usize;
302 if i < parent_substs.len() {
303 parent_substs.region_at(i)
304 } else if let Some(lifetime) =
305 supplied_lifetimes.get(i - parent_substs.len()) {
306 AstConv::ast_region_to_region(self.fcx, lifetime, Some(def))
308 self.region_var_for_def(self.span, def)
310 }, |def, cur_substs| {
311 let i = def.index as usize;
312 if i < parent_substs.len() {
313 parent_substs.type_at(i)
314 } else if let Some(ast_ty) =
315 supplied_types.get(i - parent_substs.len() - method_generics.regions.len()) {
318 self.type_var_for_def(self.span, def, cur_substs)
323 fn unify_receivers(&mut self, self_ty: Ty<'tcx>, method_self_ty: Ty<'tcx>) {
324 match self.at(&self.misc(self.span), self.param_env).sup(method_self_ty, self_ty) {
325 Ok(InferOk { obligations, value: () }) => {
326 self.register_predicates(obligations);
330 "{} was a subtype of {} but now is not?",
337 ///////////////////////////////////////////////////////////////////////////
340 fn instantiate_method_sig(&mut self,
341 pick: &probe::Pick<'tcx>,
342 all_substs: &'tcx Substs<'tcx>)
343 -> (ty::FnSig<'tcx>, ty::InstantiatedPredicates<'tcx>) {
344 debug!("instantiate_method_sig(pick={:?}, all_substs={:?})",
348 // Instantiate the bounds on the method with the
349 // type/early-bound-regions substitutions performed. There can
350 // be no late-bound regions appearing here.
351 let def_id = pick.item.def_id;
352 let method_predicates = self.tcx.predicates_of(def_id)
353 .instantiate(self.tcx, all_substs);
354 let method_predicates = self.normalize_associated_types_in(self.span,
357 debug!("method_predicates after subst = {:?}", method_predicates);
359 let sig = self.tcx.fn_sig(def_id);
361 // Instantiate late-bound regions and substitute the trait
362 // parameters into the method type to get the actual method type.
364 // NB: Instantiate late-bound regions first so that
365 // `instantiate_type_scheme` can normalize associated types that
366 // may reference those regions.
367 let method_sig = self.replace_late_bound_regions_with_fresh_var(&sig);
368 debug!("late-bound lifetimes from method instantiated, method_sig={:?}",
371 let method_sig = self.instantiate_type_scheme(self.span, all_substs, &method_sig);
372 debug!("type scheme substituted, method_sig={:?}", method_sig);
374 (method_sig, method_predicates)
377 fn add_obligations(&mut self,
379 all_substs: &Substs<'tcx>,
380 method_predicates: &ty::InstantiatedPredicates<'tcx>) {
381 debug!("add_obligations: fty={:?} all_substs={:?} method_predicates={:?}",
386 self.add_obligations_for_parameters(traits::ObligationCause::misc(self.span, self.body_id),
389 // this is a projection from a trait reference, so we have to
390 // make sure that the trait reference inputs are well-formed.
391 self.add_wf_bounds(all_substs, self.call_expr);
393 // the function type must also be well-formed (this is not
394 // implied by the substs being well-formed because of inherent
395 // impls and late-bound regions - see issue #28609).
396 self.register_wf_obligation(fty, self.span, traits::MiscObligation);
399 ///////////////////////////////////////////////////////////////////////////
402 /// When we select a method with a mutable autoref, we have to go convert any
403 /// auto-derefs, indices, etc from `Deref` and `Index` into `DerefMut` and `IndexMut`
405 fn convert_lvalue_derefs_to_mutable(&self) {
406 // Gather up expressions we want to munge.
407 let mut exprs = Vec::new();
408 exprs.push(self.self_expr);
410 let last = exprs[exprs.len() - 1];
412 hir::ExprField(ref expr, _) |
413 hir::ExprTupField(ref expr, _) |
414 hir::ExprIndex(ref expr, _) |
415 hir::ExprUnary(hir::UnDeref, ref expr) => exprs.push(&expr),
420 debug!("convert_lvalue_derefs_to_mutable: exprs={:?}", exprs);
422 // Fix up autoderefs and derefs.
423 for (i, &expr) in exprs.iter().rev().enumerate() {
424 debug!("convert_lvalue_derefs_to_mutable: i={} expr={:?}", i, expr);
426 // Fix up the autoderefs. Autorefs can only occur immediately preceding
427 // overloaded lvalue ops, and will be fixed by them in order to get
428 // the correct region.
429 let mut source = self.node_ty(expr.id);
430 // Do not mutate adjustments in place, but rather take them,
431 // and replace them after mutating them, to avoid having the
432 // tables borrowed during (`deref_mut`) method resolution.
433 let previous_adjustments = self.tables.borrow_mut().adjustments.remove(&expr.id);
434 if let Some(mut adjustments) = previous_adjustments {
435 let pref = LvaluePreference::PreferMutLvalue;
436 for adjustment in &mut adjustments {
437 if let Adjust::Deref(Some(ref mut deref)) = adjustment.kind {
438 if let Some(ok) = self.try_overloaded_deref(expr.span, source, pref) {
439 let method = self.register_infer_ok_obligations(ok);
440 if let ty::TyRef(region, mt) = method.sig.output().sty {
441 *deref = OverloadedDeref {
448 source = adjustment.target;
450 self.tables.borrow_mut().adjustments.insert(expr.id, adjustments);
454 hir::ExprIndex(ref base_expr, ref index_expr) => {
455 let index_expr_ty = self.node_ty(index_expr.id);
456 self.convert_lvalue_op_to_mutable(
457 LvalueOp::Index, expr, base_expr, &[index_expr_ty]);
459 hir::ExprUnary(hir::UnDeref, ref base_expr) => {
460 self.convert_lvalue_op_to_mutable(
461 LvalueOp::Deref, expr, base_expr, &[]);
468 fn convert_lvalue_op_to_mutable(&self,
471 base_expr: &hir::Expr,
472 arg_tys: &[Ty<'tcx>])
474 debug!("convert_lvalue_op_to_mutable({:?}, {:?}, {:?}, {:?})",
475 op, expr, base_expr, arg_tys);
476 if !self.tables.borrow().is_method_call(expr) {
477 debug!("convert_lvalue_op_to_mutable - builtin, nothing to do");
481 let base_ty = self.tables.borrow().expr_adjustments(base_expr).last()
482 .map_or_else(|| self.node_ty(expr.id), |adj| adj.target);
483 let base_ty = self.resolve_type_vars_if_possible(&base_ty);
485 // Need to deref because overloaded lvalue ops take self by-reference.
486 let base_ty = base_ty.builtin_deref(false, NoPreference)
487 .expect("lvalue op takes something that is not a ref")
490 let method = self.try_overloaded_lvalue_op(
491 expr.span, base_ty, arg_tys, PreferMutLvalue, op);
492 let method = match method {
493 Some(ok) => self.register_infer_ok_obligations(ok),
494 None => return self.tcx.sess.delay_span_bug(expr.span, "re-trying op failed")
496 debug!("convert_lvalue_op_to_mutable: method={:?}", method);
497 self.write_method_call(expr.id, method);
499 let (region, mutbl) = if let ty::TyRef(r, mt) = method.sig.inputs()[0].sty {
502 span_bug!(expr.span, "input to lvalue op is not a ref?");
505 // Convert the autoref in the base expr to mutable with the correct
506 // region and mutability.
507 let base_expr_ty = self.node_ty(base_expr.id);
508 if let Some(adjustments) = self.tables.borrow_mut().adjustments.get_mut(&base_expr.id) {
509 let mut source = base_expr_ty;
510 for adjustment in &mut adjustments[..] {
511 if let Adjust::Borrow(AutoBorrow::Ref(..)) = adjustment.kind {
512 debug!("convert_lvalue_op_to_mutable: converting autoref {:?}", adjustment);
513 adjustment.kind = Adjust::Borrow(AutoBorrow::Ref(region, mutbl));
514 adjustment.target = self.tcx.mk_ref(region, ty::TypeAndMut {
519 source = adjustment.target;
522 // If we have an autoref followed by unsizing at the end, fix the unsize target.
523 match adjustments[..] {
524 [.., Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(..)), .. },
525 Adjustment { kind: Adjust::Unsize, ref mut target }] => {
526 *target = method.sig.inputs()[0];
533 ///////////////////////////////////////////////////////////////////////////
536 fn enforce_illegal_method_limitations(&self, pick: &probe::Pick) {
537 // Disallow calls to the method `drop` defined in the `Drop` trait.
538 match pick.item.container {
539 ty::TraitContainer(trait_def_id) => {
540 callee::check_legal_trait_for_method_call(self.tcx, self.span, trait_def_id)
542 ty::ImplContainer(..) => {}
547 source_trait_ref: ty::PolyTraitRef<'tcx>,
548 target_trait_def_id: DefId)
549 -> ty::PolyTraitRef<'tcx> {
550 let upcast_trait_refs = self.tcx
551 .upcast_choices(source_trait_ref.clone(), target_trait_def_id);
553 // must be exactly one trait ref or we'd get an ambig error etc
554 if upcast_trait_refs.len() != 1 {
556 "cannot uniquely upcast `{:?}` to `{:?}`: `{:?}`",
562 upcast_trait_refs.into_iter().next().unwrap()
565 fn replace_late_bound_regions_with_fresh_var<T>(&self, value: &ty::Binder<T>) -> T
566 where T: TypeFoldable<'tcx>
569 .replace_late_bound_regions_with_fresh_var(self.span, infer::FnCall, value)