1 // Copyright 2012-2014 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 rustc::hir::{self, ImplItemKind, TraitItemKind};
12 use rustc::infer::{self, InferOk};
13 use rustc::ty::{self, TyCtxt};
14 use rustc::ty::util::ExplicitSelf;
15 use rustc::traits::{self, ObligationCause, ObligationCauseCode, Reveal};
16 use rustc::ty::error::{ExpectedFound, TypeError};
17 use rustc::ty::subst::{Subst, Substs};
18 use rustc::util::common::ErrorReported;
22 use super::{Inherited, FnCtxt};
24 /// Checks that a method from an impl conforms to the signature of
25 /// the same method as declared in the trait.
29 /// - impl_m: type of the method we are checking
30 /// - impl_m_span: span to use for reporting errors
31 /// - trait_m: the method in the trait
32 /// - impl_trait_ref: the TraitRef corresponding to the trait implementation
34 pub fn compare_impl_method<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
35 impl_m: &ty::AssociatedItem,
37 trait_m: &ty::AssociatedItem,
38 impl_trait_ref: ty::TraitRef<'tcx>,
39 trait_item_span: Option<Span>) {
40 debug!("compare_impl_method(impl_trait_ref={:?})",
43 let impl_m_span = tcx.sess.codemap().def_span(impl_m_span);
45 if let Err(ErrorReported) = compare_self_type(tcx,
53 if let Err(ErrorReported) = compare_number_of_generics(tcx,
61 if let Err(ErrorReported) = compare_number_of_method_arguments(tcx,
69 if let Err(ErrorReported) = compare_synthetic_generics(tcx,
77 if let Err(ErrorReported) = compare_predicate_entailment(tcx,
86 fn compare_predicate_entailment<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
87 impl_m: &ty::AssociatedItem,
89 trait_m: &ty::AssociatedItem,
90 impl_trait_ref: ty::TraitRef<'tcx>)
91 -> Result<(), ErrorReported> {
92 let trait_to_impl_substs = impl_trait_ref.substs;
94 // This node-id should be used for the `body_id` field on each
95 // `ObligationCause` (and the `FnCtxt`). This is what
96 // `regionck_item` expects.
97 let impl_m_node_id = tcx.hir.as_local_node_id(impl_m.def_id).unwrap();
99 let cause = ObligationCause {
101 body_id: impl_m_node_id,
102 code: ObligationCauseCode::CompareImplMethodObligation {
103 item_name: impl_m.name,
104 impl_item_def_id: impl_m.def_id,
105 trait_item_def_id: trait_m.def_id,
109 // This code is best explained by example. Consider a trait:
111 // trait Trait<'t,T> {
112 // fn method<'a,M>(t: &'t T, m: &'a M) -> Self;
117 // impl<'i, 'j, U> Trait<'j, &'i U> for Foo {
118 // fn method<'b,N>(t: &'j &'i U, m: &'b N) -> Foo;
121 // We wish to decide if those two method types are compatible.
123 // We start out with trait_to_impl_substs, that maps the trait
124 // type parameters to impl type parameters. This is taken from the
125 // impl trait reference:
127 // trait_to_impl_substs = {'t => 'j, T => &'i U, Self => Foo}
129 // We create a mapping `dummy_substs` that maps from the impl type
130 // parameters to fresh types and regions. For type parameters,
131 // this is the identity transform, but we could as well use any
132 // skolemized types. For regions, we convert from bound to free
133 // regions (Note: but only early-bound regions, i.e., those
134 // declared on the impl or used in type parameter bounds).
136 // impl_to_skol_substs = {'i => 'i0, U => U0, N => N0 }
138 // Now we can apply skol_substs to the type of the impl method
139 // to yield a new function type in terms of our fresh, skolemized
142 // <'b> fn(t: &'i0 U0, m: &'b) -> Foo
144 // We now want to extract and substitute the type of the *trait*
145 // method and compare it. To do so, we must create a compound
146 // substitution by combining trait_to_impl_substs and
147 // impl_to_skol_substs, and also adding a mapping for the method
148 // type parameters. We extend the mapping to also include
149 // the method parameters.
151 // trait_to_skol_substs = { T => &'i0 U0, Self => Foo, M => N0 }
153 // Applying this to the trait method type yields:
155 // <'a> fn(t: &'i0 U0, m: &'a) -> Foo
157 // This type is also the same but the name of the bound region ('a
158 // vs 'b). However, the normal subtyping rules on fn types handle
159 // this kind of equivalency just fine.
161 // We now use these substitutions to ensure that all declared bounds are
162 // satisfied by the implementation's method.
164 // We do this by creating a parameter environment which contains a
165 // substitution corresponding to impl_to_skol_substs. We then build
166 // trait_to_skol_substs and use it to convert the predicates contained
167 // in the trait_m.generics to the skolemized form.
169 // Finally we register each of these predicates as an obligation in
170 // a fresh FulfillmentCtxt, and invoke select_all_or_error.
172 // Create mapping from impl to skolemized.
173 let impl_to_skol_substs = Substs::identity_for_item(tcx, impl_m.def_id);
175 // Create mapping from trait to skolemized.
176 let trait_to_skol_substs = impl_to_skol_substs.rebase_onto(tcx,
177 impl_m.container.id(),
178 trait_to_impl_substs);
179 debug!("compare_impl_method: trait_to_skol_substs={:?}",
180 trait_to_skol_substs);
182 let impl_m_generics = tcx.generics_of(impl_m.def_id);
183 let trait_m_generics = tcx.generics_of(trait_m.def_id);
184 let impl_m_predicates = tcx.predicates_of(impl_m.def_id);
185 let trait_m_predicates = tcx.predicates_of(trait_m.def_id);
187 // Check region bounds.
188 check_region_bounds_on_impl_method(tcx,
194 trait_to_skol_substs)?;
196 // Create obligations for each predicate declared by the impl
197 // definition in the context of the trait's parameter
198 // environment. We can't just use `impl_env.caller_bounds`,
199 // however, because we want to replace all late-bound regions with
201 let impl_predicates = tcx.predicates_of(impl_m_predicates.parent.unwrap());
202 let mut hybrid_preds = impl_predicates.instantiate_identity(tcx);
204 debug!("compare_impl_method: impl_bounds={:?}", hybrid_preds);
206 // This is the only tricky bit of the new way we check implementation methods
207 // We need to build a set of predicates where only the method-level bounds
208 // are from the trait and we assume all other bounds from the implementation
209 // to be previously satisfied.
211 // We then register the obligations from the impl_m and check to see
212 // if all constraints hold.
213 hybrid_preds.predicates
214 .extend(trait_m_predicates.instantiate_own(tcx, trait_to_skol_substs).predicates);
216 // Construct trait parameter environment and then shift it into the skolemized viewpoint.
217 // The key step here is to update the caller_bounds's predicates to be
218 // the new hybrid bounds we computed.
219 let normalize_cause = traits::ObligationCause::misc(impl_m_span, impl_m_node_id);
220 let param_env = ty::ParamEnv::new(tcx.intern_predicates(&hybrid_preds.predicates),
222 let param_env = traits::normalize_param_env_or_error(tcx,
225 normalize_cause.clone());
227 tcx.infer_ctxt().enter(|infcx| {
228 let inh = Inherited::new(infcx, impl_m.def_id);
229 let infcx = &inh.infcx;
231 debug!("compare_impl_method: caller_bounds={:?}",
232 param_env.caller_bounds);
234 let mut selcx = traits::SelectionContext::new(&infcx);
236 let impl_m_own_bounds = impl_m_predicates.instantiate_own(tcx, impl_to_skol_substs);
237 let (impl_m_own_bounds, _) = infcx.replace_late_bound_regions_with_fresh_var(
239 infer::HigherRankedType,
240 &ty::Binder::bind(impl_m_own_bounds.predicates)
242 for predicate in impl_m_own_bounds {
243 let traits::Normalized { value: predicate, obligations } =
244 traits::normalize(&mut selcx, param_env, normalize_cause.clone(), &predicate);
246 inh.register_predicates(obligations);
247 inh.register_predicate(traits::Obligation::new(cause.clone(), param_env, predicate));
250 // We now need to check that the signature of the impl method is
251 // compatible with that of the trait method. We do this by
252 // checking that `impl_fty <: trait_fty`.
254 // FIXME. Unfortunately, this doesn't quite work right now because
255 // associated type normalization is not integrated into subtype
256 // checks. For the comparison to be valid, we need to
257 // normalize the associated types in the impl/trait methods
258 // first. However, because function types bind regions, just
259 // calling `normalize_associated_types_in` would have no effect on
260 // any associated types appearing in the fn arguments or return
263 // Compute skolemized form of impl and trait method tys.
267 infcx.replace_late_bound_regions_with_fresh_var(impl_m_span,
268 infer::HigherRankedType,
269 &tcx.fn_sig(impl_m.def_id));
271 inh.normalize_associated_types_in(impl_m_span,
275 let impl_fty = tcx.mk_fn_ptr(ty::Binder::bind(impl_sig));
276 debug!("compare_impl_method: impl_fty={:?}", impl_fty);
278 let trait_sig = tcx.liberate_late_bound_regions(
280 &tcx.fn_sig(trait_m.def_id));
282 trait_sig.subst(tcx, trait_to_skol_substs);
284 inh.normalize_associated_types_in(impl_m_span,
288 let trait_fty = tcx.mk_fn_ptr(ty::Binder::bind(trait_sig));
290 debug!("compare_impl_method: trait_fty={:?}", trait_fty);
292 let sub_result = infcx.at(&cause, param_env)
293 .sup(trait_fty, impl_fty)
294 .map(|InferOk { obligations, .. }| {
295 inh.register_predicates(obligations);
298 if let Err(terr) = sub_result {
299 debug!("sub_types failed: impl ty {:?}, trait ty {:?}",
303 let (impl_err_span, trait_err_span) = extract_spans_for_error_reporting(&infcx,
312 let cause = ObligationCause {
317 let mut diag = struct_span_err!(tcx.sess,
320 "method `{}` has an incompatible type for trait",
323 infcx.note_type_err(&mut diag,
325 trait_err_span.map(|sp| (sp, format!("type in trait"))),
326 Some(infer::ValuePairs::Types(ExpectedFound {
332 return Err(ErrorReported);
335 // Check that all obligations are satisfied by the implementation's
337 if let Err(ref errors) = inh.fulfillment_cx.borrow_mut().select_all_or_error(&infcx) {
338 infcx.report_fulfillment_errors(errors, None, false);
339 return Err(ErrorReported);
342 // Finally, resolve all regions. This catches wily misuses of
343 // lifetime parameters.
344 let fcx = FnCtxt::new(&inh, param_env, impl_m_node_id);
345 fcx.regionck_item(impl_m_node_id, impl_m_span, &[]);
351 fn check_region_bounds_on_impl_method<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
353 impl_m: &ty::AssociatedItem,
354 trait_m: &ty::AssociatedItem,
355 trait_generics: &ty::Generics,
356 impl_generics: &ty::Generics,
357 trait_to_skol_substs: &Substs<'tcx>)
358 -> Result<(), ErrorReported> {
359 let span = tcx.sess.codemap().def_span(span);
360 let trait_params = &trait_generics.regions[..];
361 let impl_params = &impl_generics.regions[..];
363 debug!("check_region_bounds_on_impl_method: \
364 trait_generics={:?} \
366 trait_to_skol_substs={:?}",
369 trait_to_skol_substs);
371 // Must have same number of early-bound lifetime parameters.
372 // Unfortunately, if the user screws up the bounds, then this
373 // will change classification between early and late. E.g.,
374 // if in trait we have `<'a,'b:'a>`, and in impl we just have
375 // `<'a,'b>`, then we have 2 early-bound lifetime parameters
376 // in trait but 0 in the impl. But if we report "expected 2
377 // but found 0" it's confusing, because it looks like there
378 // are zero. Since I don't quite know how to phrase things at
379 // the moment, give a kind of vague error message.
380 if trait_params.len() != impl_params.len() {
381 let mut err = struct_span_err!(tcx.sess,
384 "lifetime parameters or bounds on method `{}` do not match \
385 the trait declaration",
387 err.span_label(span, "lifetimes do not match method in trait");
388 if let Some(sp) = tcx.hir.span_if_local(trait_m.def_id) {
389 err.span_label(tcx.sess.codemap().def_span(sp),
390 "lifetimes in impl do not match this method in trait");
393 return Err(ErrorReported);
399 fn extract_spans_for_error_reporting<'a, 'gcx, 'tcx>(infcx: &infer::InferCtxt<'a, 'gcx, 'tcx>,
400 param_env: ty::ParamEnv<'tcx>,
402 cause: &ObligationCause<'tcx>,
403 impl_m: &ty::AssociatedItem,
404 impl_sig: ty::FnSig<'tcx>,
405 trait_m: &ty::AssociatedItem,
406 trait_sig: ty::FnSig<'tcx>)
407 -> (Span, Option<Span>) {
409 let impl_m_node_id = tcx.hir.as_local_node_id(impl_m.def_id).unwrap();
410 let (impl_m_output, impl_m_iter) = match tcx.hir.expect_impl_item(impl_m_node_id).node {
411 ImplItemKind::Method(ref impl_m_sig, _) => {
412 (&impl_m_sig.decl.output, impl_m_sig.decl.inputs.iter())
414 _ => bug!("{:?} is not a method", impl_m),
418 TypeError::Mutability => {
419 if let Some(trait_m_node_id) = tcx.hir.as_local_node_id(trait_m.def_id) {
420 let trait_m_iter = match tcx.hir.expect_trait_item(trait_m_node_id).node {
421 TraitItemKind::Method(ref trait_m_sig, _) => {
422 trait_m_sig.decl.inputs.iter()
424 _ => bug!("{:?} is not a TraitItemKind::Method", trait_m),
427 impl_m_iter.zip(trait_m_iter).find(|&(ref impl_arg, ref trait_arg)| {
428 match (&impl_arg.node, &trait_arg.node) {
429 (&hir::TyRptr(_, ref impl_mt), &hir::TyRptr(_, ref trait_mt)) |
430 (&hir::TyPtr(ref impl_mt), &hir::TyPtr(ref trait_mt)) => {
431 impl_mt.mutbl != trait_mt.mutbl
435 }).map(|(ref impl_arg, ref trait_arg)| {
436 (impl_arg.span, Some(trait_arg.span))
438 .unwrap_or_else(|| (cause.span(&tcx), tcx.hir.span_if_local(trait_m.def_id)))
440 (cause.span(&tcx), tcx.hir.span_if_local(trait_m.def_id))
443 TypeError::Sorts(ExpectedFound { .. }) => {
444 if let Some(trait_m_node_id) = tcx.hir.as_local_node_id(trait_m.def_id) {
445 let (trait_m_output, trait_m_iter) =
446 match tcx.hir.expect_trait_item(trait_m_node_id).node {
447 TraitItemKind::Method(ref trait_m_sig, _) => {
448 (&trait_m_sig.decl.output, trait_m_sig.decl.inputs.iter())
450 _ => bug!("{:?} is not a TraitItemKind::Method", trait_m),
453 let impl_iter = impl_sig.inputs().iter();
454 let trait_iter = trait_sig.inputs().iter();
455 impl_iter.zip(trait_iter)
458 .filter_map(|(((&impl_arg_ty, &trait_arg_ty), impl_arg), trait_arg)| {
459 match infcx.at(&cause, param_env).sub(trait_arg_ty, impl_arg_ty) {
461 Err(_) => Some((impl_arg.span, Some(trait_arg.span))),
467 infcx.at(&cause, param_env)
468 .sup(trait_sig.output(), impl_sig.output())
471 (impl_m_output.span(), Some(trait_m_output.span()))
473 (cause.span(&tcx), tcx.hir.span_if_local(trait_m.def_id))
477 (cause.span(&tcx), tcx.hir.span_if_local(trait_m.def_id))
480 _ => (cause.span(&tcx), tcx.hir.span_if_local(trait_m.def_id)),
484 fn compare_self_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
485 impl_m: &ty::AssociatedItem,
487 trait_m: &ty::AssociatedItem,
488 impl_trait_ref: ty::TraitRef<'tcx>)
489 -> Result<(), ErrorReported>
491 // Try to give more informative error messages about self typing
492 // mismatches. Note that any mismatch will also be detected
493 // below, where we construct a canonical function type that
494 // includes the self parameter as a normal parameter. It's just
495 // that the error messages you get out of this code are a bit more
496 // inscrutable, particularly for cases where one method has no
499 let self_string = |method: &ty::AssociatedItem| {
500 let untransformed_self_ty = match method.container {
501 ty::ImplContainer(_) => impl_trait_ref.self_ty(),
502 ty::TraitContainer(_) => tcx.mk_self_type()
504 let self_arg_ty = *tcx.fn_sig(method.def_id).input(0).skip_binder();
505 let param_env = ty::ParamEnv::reveal_all();
507 tcx.infer_ctxt().enter(|infcx| {
508 let self_arg_ty = tcx.liberate_late_bound_regions(
510 &ty::Binder::bind(self_arg_ty)
512 let can_eq_self = |ty| infcx.can_eq(param_env, untransformed_self_ty, ty).is_ok();
513 match ExplicitSelf::determine(self_arg_ty, can_eq_self) {
514 ExplicitSelf::ByValue => "self".to_string(),
515 ExplicitSelf::ByReference(_, hir::MutImmutable) => "&self".to_string(),
516 ExplicitSelf::ByReference(_, hir::MutMutable) => "&mut self".to_string(),
517 _ => format!("self: {}", self_arg_ty)
522 match (trait_m.method_has_self_argument, impl_m.method_has_self_argument) {
523 (false, false) | (true, true) => {}
526 let self_descr = self_string(impl_m);
527 let mut err = struct_span_err!(tcx.sess,
530 "method `{}` has a `{}` declaration in the impl, but \
534 err.span_label(impl_m_span, format!("`{}` used in impl", self_descr));
535 if let Some(span) = tcx.hir.span_if_local(trait_m.def_id) {
536 err.span_label(span, format!("trait method declared without `{}`", self_descr));
538 err.note_trait_signature(trait_m.name.to_string(),
539 trait_m.signature(&tcx));
542 return Err(ErrorReported);
546 let self_descr = self_string(trait_m);
547 let mut err = struct_span_err!(tcx.sess,
550 "method `{}` has a `{}` declaration in the trait, but \
554 err.span_label(impl_m_span, format!("expected `{}` in impl", self_descr));
555 if let Some(span) = tcx.hir.span_if_local(trait_m.def_id) {
556 err.span_label(span, format!("`{}` used in trait", self_descr));
558 err.note_trait_signature(trait_m.name.to_string(),
559 trait_m.signature(&tcx));
562 return Err(ErrorReported);
569 fn compare_number_of_generics<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
570 impl_m: &ty::AssociatedItem,
572 trait_m: &ty::AssociatedItem,
573 trait_item_span: Option<Span>)
574 -> Result<(), ErrorReported> {
575 let impl_m_generics = tcx.generics_of(impl_m.def_id);
576 let trait_m_generics = tcx.generics_of(trait_m.def_id);
577 let num_impl_m_type_params = impl_m_generics.types.len();
578 let num_trait_m_type_params = trait_m_generics.types.len();
579 if num_impl_m_type_params != num_trait_m_type_params {
580 let impl_m_node_id = tcx.hir.as_local_node_id(impl_m.def_id).unwrap();
581 let impl_m_item = tcx.hir.expect_impl_item(impl_m_node_id);
582 let span = if impl_m_item.generics.params.is_empty() {
585 impl_m_item.generics.span
588 let mut err = struct_span_err!(tcx.sess,
591 "method `{}` has {} type parameter{} but its trait \
592 declaration has {} type parameter{}",
594 num_impl_m_type_params,
595 if num_impl_m_type_params == 1 { "" } else { "s" },
596 num_trait_m_type_params,
597 if num_trait_m_type_params == 1 {
603 let mut suffix = None;
605 if let Some(span) = trait_item_span {
607 format!("expected {}",
608 &if num_trait_m_type_params != 1 {
609 format!("{} type parameters", num_trait_m_type_params)
611 format!("{} type parameter", num_trait_m_type_params)
614 suffix = Some(format!(", expected {}", num_trait_m_type_params));
618 format!("found {}{}",
619 &if num_impl_m_type_params != 1 {
620 format!("{} type parameters", num_impl_m_type_params)
622 format!("1 type parameter")
624 suffix.as_ref().map(|s| &s[..]).unwrap_or("")));
628 return Err(ErrorReported);
634 fn compare_number_of_method_arguments<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
635 impl_m: &ty::AssociatedItem,
637 trait_m: &ty::AssociatedItem,
638 trait_item_span: Option<Span>)
639 -> Result<(), ErrorReported> {
640 let impl_m_fty = tcx.fn_sig(impl_m.def_id);
641 let trait_m_fty = tcx.fn_sig(trait_m.def_id);
642 let trait_number_args = trait_m_fty.inputs().skip_binder().len();
643 let impl_number_args = impl_m_fty.inputs().skip_binder().len();
644 if trait_number_args != impl_number_args {
645 let trait_m_node_id = tcx.hir.as_local_node_id(trait_m.def_id);
646 let trait_span = if let Some(trait_id) = trait_m_node_id {
647 match tcx.hir.expect_trait_item(trait_id).node {
648 TraitItemKind::Method(ref trait_m_sig, _) => {
649 if let Some(arg) = trait_m_sig.decl.inputs.get(if trait_number_args > 0 {
650 trait_number_args - 1
659 _ => bug!("{:?} is not a method", impl_m),
664 let impl_m_node_id = tcx.hir.as_local_node_id(impl_m.def_id).unwrap();
665 let impl_span = match tcx.hir.expect_impl_item(impl_m_node_id).node {
666 ImplItemKind::Method(ref impl_m_sig, _) => {
667 if let Some(arg) = impl_m_sig.decl.inputs.get(if impl_number_args > 0 {
677 _ => bug!("{:?} is not a method", impl_m),
679 let mut err = struct_span_err!(tcx.sess,
682 "method `{}` has {} parameter{} but the declaration in \
686 if impl_number_args == 1 { "" } else { "s" },
687 tcx.item_path_str(trait_m.def_id),
689 if let Some(trait_span) = trait_span {
690 err.span_label(trait_span,
691 format!("trait requires {}",
692 &if trait_number_args != 1 {
693 format!("{} parameters", trait_number_args)
695 format!("{} parameter", trait_number_args)
698 err.note_trait_signature(trait_m.name.to_string(),
699 trait_m.signature(&tcx));
701 err.span_label(impl_span,
702 format!("expected {}, found {}",
703 &if trait_number_args != 1 {
704 format!("{} parameters", trait_number_args)
706 format!("{} parameter", trait_number_args)
710 return Err(ErrorReported);
716 fn compare_synthetic_generics<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
717 impl_m: &ty::AssociatedItem,
718 _impl_m_span: Span, // FIXME necessary?
719 trait_m: &ty::AssociatedItem,
720 _trait_item_span: Option<Span>) // FIXME necessary?
721 -> Result<(), ErrorReported> {
722 // FIXME(chrisvittal) Clean up this function, list of FIXME items:
723 // 1. Better messages for the span lables
724 // 2. Explanation as to what is going on
725 // 3. Correct the function signature for what we actually use
726 // If we get here, we already have the same number of generics, so the zip will
728 let mut error_found = false;
729 let impl_m_generics = tcx.generics_of(impl_m.def_id);
730 let trait_m_generics = tcx.generics_of(trait_m.def_id);
731 for (impl_ty, trait_ty) in impl_m_generics.types.iter().zip(trait_m_generics.types.iter()) {
732 if impl_ty.synthetic != trait_ty.synthetic {
733 let impl_node_id = tcx.hir.as_local_node_id(impl_ty.def_id).unwrap();
734 let impl_span = tcx.hir.span(impl_node_id);
735 let trait_node_id = tcx.hir.as_local_node_id(trait_ty.def_id).unwrap();
736 let trait_span = tcx.hir.span(trait_node_id);
737 let mut err = struct_span_err!(tcx.sess,
740 "method `{}` has incompatible signature for trait",
742 err.span_label(trait_span, "annotation in trait");
743 err.span_label(impl_span, "annotation in impl");
755 pub fn compare_const_impl<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
756 impl_c: &ty::AssociatedItem,
758 trait_c: &ty::AssociatedItem,
759 impl_trait_ref: ty::TraitRef<'tcx>) {
760 debug!("compare_const_impl(impl_trait_ref={:?})", impl_trait_ref);
762 tcx.infer_ctxt().enter(|infcx| {
763 let param_env = ty::ParamEnv::empty();
764 let inh = Inherited::new(infcx, impl_c.def_id);
765 let infcx = &inh.infcx;
767 // The below is for the most part highly similar to the procedure
768 // for methods above. It is simpler in many respects, especially
769 // because we shouldn't really have to deal with lifetimes or
770 // predicates. In fact some of this should probably be put into
771 // shared functions because of DRY violations...
772 let trait_to_impl_substs = impl_trait_ref.substs;
774 // Create a parameter environment that represents the implementation's
776 let impl_c_node_id = tcx.hir.as_local_node_id(impl_c.def_id).unwrap();
778 // Compute skolemized form of impl and trait const tys.
779 let impl_ty = tcx.type_of(impl_c.def_id);
780 let trait_ty = tcx.type_of(trait_c.def_id).subst(tcx, trait_to_impl_substs);
781 let mut cause = ObligationCause::misc(impl_c_span, impl_c_node_id);
783 // There is no "body" here, so just pass dummy id.
784 let impl_ty = inh.normalize_associated_types_in(impl_c_span,
789 debug!("compare_const_impl: impl_ty={:?}", impl_ty);
791 let trait_ty = inh.normalize_associated_types_in(impl_c_span,
796 debug!("compare_const_impl: trait_ty={:?}", trait_ty);
798 let err = infcx.at(&cause, param_env)
799 .sup(trait_ty, impl_ty)
800 .map(|ok| inh.register_infer_ok_obligations(ok));
802 if let Err(terr) = err {
803 debug!("checking associated const for compatibility: impl ty {:?}, trait ty {:?}",
807 // Locate the Span containing just the type of the offending impl
808 match tcx.hir.expect_impl_item(impl_c_node_id).node {
809 ImplItemKind::Const(ref ty, _) => cause.span = ty.span,
810 _ => bug!("{:?} is not a impl const", impl_c),
813 let mut diag = struct_span_err!(tcx.sess,
816 "implemented const `{}` has an incompatible type for \
820 let trait_c_node_id = tcx.hir.as_local_node_id(trait_c.def_id);
821 let trait_c_span = trait_c_node_id.map(|trait_c_node_id| {
822 // Add a label to the Span containing just the type of the const
823 match tcx.hir.expect_trait_item(trait_c_node_id).node {
824 TraitItemKind::Const(ref ty, _) => ty.span,
825 _ => bug!("{:?} is not a trait const", trait_c),
829 infcx.note_type_err(&mut diag,
831 trait_c_span.map(|span| (span, format!("type in trait"))),
832 Some(infer::ValuePairs::Types(ExpectedFound {
840 // Check that all obligations are satisfied by the implementation's
842 if let Err(ref errors) = inh.fulfillment_cx.borrow_mut().select_all_or_error(&infcx) {
843 infcx.report_fulfillment_errors(errors, None, false);
847 let fcx = FnCtxt::new(&inh, param_env, impl_c_node_id);
848 fcx.regionck_item(impl_c_node_id, impl_c_span, &[]);