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 check::{Inherited, FnCtxt};
12 use constrained_type_params::{identify_constrained_type_params, Parameter};
14 use hir::def_id::DefId;
15 use rustc::traits::{self, ObligationCauseCode};
16 use rustc::ty::{self, Lift, Ty, TyCtxt, GenericParamDefKind, TypeFoldable};
17 use rustc::ty::subst::{Subst, Substs};
18 use rustc::ty::util::ExplicitSelf;
19 use rustc::util::nodemap::{FxHashSet, FxHashMap};
20 use rustc::middle::lang_items;
21 use rustc::infer::anon_types::may_define_existential_type;
24 use syntax::feature_gate::{self, GateIssue};
26 use errors::{DiagnosticBuilder, DiagnosticId};
28 use rustc::hir::intravisit::{self, Visitor, NestedVisitorMap};
31 /// Helper type of a temporary returned by .for_item(...).
32 /// Necessary because we can't write the following bound:
33 /// F: for<'b, 'tcx> where 'gcx: 'tcx FnOnce(FnCtxt<'b, 'gcx, 'tcx>).
34 struct CheckWfFcxBuilder<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
35 inherited: super::InheritedBuilder<'a, 'gcx, 'tcx>,
38 param_env: ty::ParamEnv<'tcx>,
41 impl<'a, 'gcx, 'tcx> CheckWfFcxBuilder<'a, 'gcx, 'tcx> {
42 fn with_fcx<F>(&'tcx mut self, f: F) where
43 F: for<'b> FnOnce(&FnCtxt<'b, 'gcx, 'tcx>,
44 TyCtxt<'b, 'gcx, 'gcx>) -> Vec<Ty<'tcx>>
48 let param_env = self.param_env;
49 self.inherited.enter(|inh| {
50 let fcx = FnCtxt::new(&inh, param_env, id);
51 if !inh.tcx.features().trivial_bounds {
52 // As predicates are cached rather than obligations, this
53 // needsto be called first so that they are checked with an
55 check_false_global_bounds(&fcx, span, id);
57 let wf_tys = f(&fcx, fcx.tcx.global_tcx());
58 fcx.select_all_obligations_or_error();
59 fcx.regionck_item(id, span, &wf_tys);
64 /// Checks that the field types (in a struct def'n) or argument types (in an enum def'n) are
65 /// well-formed, meaning that they do not require any constraints not declared in the struct
66 /// definition itself. For example, this definition would be illegal:
68 /// struct Ref<'a, T> { x: &'a T }
70 /// because the type did not declare that `T:'a`.
72 /// We do this check as a pre-pass before checking fn bodies because if these constraints are
73 /// not included it frequently leads to confusing errors in fn bodies. So it's better to check
75 pub fn check_item_well_formed<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) {
76 let node_id = tcx.hir.as_local_node_id(def_id).unwrap();
77 let item = tcx.hir.expect_item(node_id);
79 debug!("check_item_well_formed(it.id={}, it.name={})",
81 tcx.item_path_str(def_id));
84 // Right now we check that every default trait implementation
85 // has an implementation of itself. Basically, a case like:
87 // `impl Trait for T {}`
89 // has a requirement of `T: Trait` which was required for default
90 // method implementations. Although this could be improved now that
91 // there's a better infrastructure in place for this, it's being left
92 // for a follow-up work.
94 // Since there's such a requirement, we need to check *just* positive
95 // implementations, otherwise things like:
97 // impl !Send for T {}
99 // won't be allowed unless there's an *explicit* implementation of `Send`
101 hir::ItemKind::Impl(_, polarity, defaultness, _, ref trait_ref, ref self_ty, _) => {
102 let is_auto = tcx.impl_trait_ref(tcx.hir.local_def_id(item.id))
103 .map_or(false, |trait_ref| tcx.trait_is_auto(trait_ref.def_id));
104 if let (hir::Defaultness::Default { .. }, true) = (defaultness, is_auto) {
105 tcx.sess.span_err(item.span, "impls of auto traits cannot be default");
107 if polarity == hir::ImplPolarity::Positive {
108 check_impl(tcx, item, self_ty, trait_ref);
110 // FIXME(#27579) what amount of WF checking do we need for neg impls?
111 if trait_ref.is_some() && !is_auto {
112 span_err!(tcx.sess, item.span, E0192,
113 "negative impls are only allowed for \
114 auto traits (e.g., `Send` and `Sync`)")
118 hir::ItemKind::Fn(..) => {
119 check_item_fn(tcx, item);
121 hir::ItemKind::Static(..) => {
122 check_item_type(tcx, item);
124 hir::ItemKind::Const(..) => {
125 check_item_type(tcx, item);
127 hir::ItemKind::Struct(ref struct_def, ref ast_generics) => {
128 check_type_defn(tcx, item, false, |fcx| {
129 vec![fcx.non_enum_variant(struct_def)]
132 check_variances_for_type_defn(tcx, item, ast_generics);
134 hir::ItemKind::Union(ref struct_def, ref ast_generics) => {
135 check_type_defn(tcx, item, true, |fcx| {
136 vec![fcx.non_enum_variant(struct_def)]
139 check_variances_for_type_defn(tcx, item, ast_generics);
141 hir::ItemKind::Enum(ref enum_def, ref ast_generics) => {
142 check_type_defn(tcx, item, true, |fcx| {
143 fcx.enum_variants(enum_def)
146 check_variances_for_type_defn(tcx, item, ast_generics);
148 hir::ItemKind::Trait(..) => {
149 check_trait(tcx, item);
155 pub fn check_trait_item<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) {
156 let node_id = tcx.hir.as_local_node_id(def_id).unwrap();
157 let trait_item = tcx.hir.expect_trait_item(node_id);
159 let method_sig = match trait_item.node {
160 hir::TraitItemKind::Method(ref sig, _) => Some(sig),
163 check_associated_item(tcx, trait_item.id, trait_item.span, method_sig);
166 pub fn check_impl_item<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) {
167 let node_id = tcx.hir.as_local_node_id(def_id).unwrap();
168 let impl_item = tcx.hir.expect_impl_item(node_id);
170 let method_sig = match impl_item.node {
171 hir::ImplItemKind::Method(ref sig, _) => Some(sig),
174 check_associated_item(tcx, impl_item.id, impl_item.span, method_sig);
177 fn check_associated_item<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
178 item_id: ast::NodeId,
180 sig_if_method: Option<&hir::MethodSig>) {
181 let code = ObligationCauseCode::MiscObligation;
182 for_id(tcx, item_id, span).with_fcx(|fcx, tcx| {
183 let item = fcx.tcx.associated_item(fcx.tcx.hir.local_def_id(item_id));
185 let (mut implied_bounds, self_ty) = match item.container {
186 ty::TraitContainer(_) => (vec![], fcx.tcx.mk_self_type()),
187 ty::ImplContainer(def_id) => (fcx.impl_implied_bounds(def_id, span),
188 fcx.tcx.type_of(def_id))
192 ty::AssociatedKind::Const => {
193 let ty = fcx.tcx.type_of(item.def_id);
194 let ty = fcx.normalize_associated_types_in(span, &ty);
195 fcx.register_wf_obligation(ty, span, code.clone());
197 ty::AssociatedKind::Method => {
198 reject_shadowing_parameters(fcx.tcx, item.def_id);
199 let sig = fcx.tcx.fn_sig(item.def_id);
200 let sig = fcx.normalize_associated_types_in(span, &sig);
201 check_fn_or_method(tcx, fcx, span, sig,
202 item.def_id, &mut implied_bounds);
203 let sig_if_method = sig_if_method.expect("bad signature for method");
204 check_method_receiver(fcx, sig_if_method, &item, self_ty);
206 ty::AssociatedKind::Type => {
207 if item.defaultness.has_value() {
208 let ty = fcx.tcx.type_of(item.def_id);
209 let ty = fcx.normalize_associated_types_in(span, &ty);
210 fcx.register_wf_obligation(ty, span, code.clone());
213 ty::AssociatedKind::Existential => {
214 // FIXME(oli-obk) implement existential types in trait impls
223 fn for_item<'a, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'gcx>, item: &hir::Item)
224 -> CheckWfFcxBuilder<'a, 'gcx, 'tcx> {
225 for_id(tcx, item.id, item.span)
228 fn for_id<'a, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'gcx>, id: ast::NodeId, span: Span)
229 -> CheckWfFcxBuilder<'a, 'gcx, 'tcx> {
230 let def_id = tcx.hir.local_def_id(id);
232 inherited: Inherited::build(tcx, def_id),
235 param_env: tcx.param_env(def_id),
239 /// In a type definition, we check that to ensure that the types of the fields are well-formed.
240 fn check_type_defn<'a, 'tcx, F>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
241 item: &hir::Item, all_sized: bool, mut lookup_fields: F)
242 where F: for<'fcx, 'gcx, 'tcx2> FnMut(&FnCtxt<'fcx, 'gcx, 'tcx2>) -> Vec<AdtVariant<'tcx2>>
244 for_item(tcx, item).with_fcx(|fcx, fcx_tcx| {
245 let variants = lookup_fields(fcx);
246 let def_id = fcx.tcx.hir.local_def_id(item.id);
247 let packed = fcx.tcx.adt_def(def_id).repr.packed();
249 for variant in &variants {
250 // For DST, or when drop needs to copy things around, all
251 // intermediate types must be sized.
252 let needs_drop_copy = || {
254 let ty = variant.fields.last().unwrap().ty;
255 let ty = fcx.tcx.erase_regions(&ty).lift_to_tcx(fcx_tcx)
257 span_bug!(item.span, "inference variables in {:?}", ty)
259 ty.needs_drop(fcx_tcx, fcx_tcx.param_env(def_id))
264 variant.fields.is_empty() ||
271 for field in &variant.fields[..variant.fields.len() - unsized_len] {
274 fcx.tcx.require_lang_item(lang_items::SizedTraitLangItem),
275 traits::ObligationCause::new(field.span,
277 traits::FieldSized(match item.node.adt_kind() {
283 // All field types must be well-formed.
284 for field in &variant.fields {
285 fcx.register_wf_obligation(field.ty, field.span,
286 ObligationCauseCode::MiscObligation)
290 check_where_clauses(tcx, fcx, item.span, def_id, None);
292 vec![] // no implied bounds in a struct def'n
296 fn check_trait<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, item: &hir::Item) {
297 let trait_def_id = tcx.hir.local_def_id(item.id);
298 for_item(tcx, item).with_fcx(|fcx, _| {
299 check_where_clauses(tcx, fcx, item.span, trait_def_id, None);
304 fn check_item_fn<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, item: &hir::Item) {
305 for_item(tcx, item).with_fcx(|fcx, tcx| {
306 let def_id = fcx.tcx.hir.local_def_id(item.id);
307 let sig = fcx.tcx.fn_sig(def_id);
308 let sig = fcx.normalize_associated_types_in(item.span, &sig);
309 let mut implied_bounds = vec![];
310 check_fn_or_method(tcx, fcx, item.span, sig,
311 def_id, &mut implied_bounds);
316 fn check_item_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
319 debug!("check_item_type: {:?}", item);
321 for_item(tcx, item).with_fcx(|fcx, _this| {
322 let ty = fcx.tcx.type_of(fcx.tcx.hir.local_def_id(item.id));
323 let item_ty = fcx.normalize_associated_types_in(item.span, &ty);
325 fcx.register_wf_obligation(item_ty, item.span, ObligationCauseCode::MiscObligation);
327 vec![] // no implied bounds in a const etc
331 fn check_impl<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
333 ast_self_ty: &hir::Ty,
334 ast_trait_ref: &Option<hir::TraitRef>)
336 debug!("check_impl: {:?}", item);
338 for_item(tcx, item).with_fcx(|fcx, tcx| {
339 let item_def_id = fcx.tcx.hir.local_def_id(item.id);
341 match *ast_trait_ref {
342 Some(ref ast_trait_ref) => {
343 let trait_ref = fcx.tcx.impl_trait_ref(item_def_id).unwrap();
345 fcx.normalize_associated_types_in(
346 ast_trait_ref.path.span, &trait_ref);
348 ty::wf::trait_obligations(fcx,
352 ast_trait_ref.path.span);
353 for obligation in obligations {
354 fcx.register_predicate(obligation);
358 let self_ty = fcx.tcx.type_of(item_def_id);
359 let self_ty = fcx.normalize_associated_types_in(item.span, &self_ty);
360 fcx.register_wf_obligation(self_ty, ast_self_ty.span,
361 ObligationCauseCode::MiscObligation);
365 check_where_clauses(tcx, fcx, item.span, item_def_id, None);
367 fcx.impl_implied_bounds(item_def_id, item.span)
371 /// Checks where clauses and inline bounds that are declared on def_id.
372 fn check_where_clauses<'a, 'gcx, 'fcx, 'tcx>(
373 tcx: TyCtxt<'a, 'gcx, 'gcx>,
374 fcx: &FnCtxt<'fcx, 'gcx, 'tcx>,
377 return_ty: Option<Ty<'tcx>>,
379 use ty::subst::Subst;
380 use rustc::ty::TypeFoldable;
382 let predicates = fcx.tcx.predicates_of(def_id);
384 let generics = tcx.generics_of(def_id);
385 let is_our_default = |def: &ty::GenericParamDef| {
387 GenericParamDefKind::Type { has_default, .. } => {
388 has_default && def.index >= generics.parent_count as u32
394 // Check that concrete defaults are well-formed. See test `type-check-defaults.rs`.
395 // For example this forbids the declaration:
396 // struct Foo<T = Vec<[u32]>> { .. }
397 // Here the default `Vec<[u32]>` is not WF because `[u32]: Sized` does not hold.
398 for param in &generics.params {
399 if let GenericParamDefKind::Type {..} = param.kind {
400 if is_our_default(¶m) {
401 let ty = fcx.tcx.type_of(param.def_id);
402 // ignore dependent defaults -- that is, where the default of one type
403 // parameter includes another (e.g., <T, U = T>). In those cases, we can't
404 // be sure if it will error or not as user might always specify the other.
405 if !ty.needs_subst() {
406 fcx.register_wf_obligation(ty, fcx.tcx.def_span(param.def_id),
407 ObligationCauseCode::MiscObligation);
413 // Check that trait predicates are WF when params are substituted by their defaults.
414 // We don't want to overly constrain the predicates that may be written but we want to
415 // catch cases where a default my never be applied such as `struct Foo<T: Copy = String>`.
416 // Therefore we check if a predicate which contains a single type param
417 // with a concrete default is WF with that default substituted.
418 // For more examples see tests `defaults-well-formedness.rs` and `type-check-defaults.rs`.
420 // First we build the defaulted substitution.
421 let substs = Substs::for_item(fcx.tcx, def_id, |param, _| {
423 GenericParamDefKind::Lifetime => {
424 // All regions are identity.
425 fcx.tcx.mk_param_from_def(param)
427 GenericParamDefKind::Type {..} => {
428 // If the param has a default,
429 if is_our_default(param) {
430 let default_ty = fcx.tcx.type_of(param.def_id);
431 // and it's not a dependent default
432 if !default_ty.needs_subst() {
433 // then substitute with the default.
434 return default_ty.into();
437 // Mark unwanted params as err.
438 fcx.tcx.types.err.into()
442 // Now we build the substituted predicates.
443 let default_obligations = predicates.predicates.iter().flat_map(|&pred| {
444 struct CountParams { params: FxHashSet<u32> }
445 impl<'tcx> ty::fold::TypeVisitor<'tcx> for CountParams {
446 fn visit_ty(&mut self, t: Ty<'tcx>) -> bool {
449 self.params.insert(p.idx);
450 t.super_visit_with(self)
452 _ => t.super_visit_with(self)
456 fn visit_region(&mut self, _: ty::Region<'tcx>) -> bool {
460 let mut param_count = CountParams { params: FxHashSet() };
461 let has_region = pred.visit_with(&mut param_count);
462 let substituted_pred = pred.subst(fcx.tcx, substs);
463 // Don't check non-defaulted params, dependent defaults (including lifetimes)
464 // or preds with multiple params.
466 substituted_pred.references_error() || param_count.params.len() > 1
470 } else if predicates.predicates.contains(&substituted_pred) {
471 // Avoid duplication of predicates that contain no parameters, for example.
474 Some(substituted_pred)
477 // convert each of those into an obligation. So if you have
478 // something like `struct Foo<T: Copy = String>`, we would
479 // take that predicate `T: Copy`, substitute to `String: Copy`
480 // (actually that happens in the previous `flat_map` call),
481 // and then try to prove it (in this case, we'll fail).
483 // Note the subtle difference from how we handle `predicates`
484 // below: there, we are not trying to prove those predicates
485 // to be *true* but merely *well-formed*.
486 let pred = fcx.normalize_associated_types_in(span, &pred);
487 let cause = traits::ObligationCause::new(span, fcx.body_id, traits::ItemObligation(def_id));
488 traits::Obligation::new(cause, fcx.param_env, pred)
491 let mut predicates = predicates.instantiate_identity(fcx.tcx);
493 if let Some(return_ty) = return_ty {
494 predicates.predicates.extend(check_existential_types(tcx, fcx, def_id, span, return_ty));
497 let predicates = fcx.normalize_associated_types_in(span, &predicates);
499 debug!("check_where_clauses: predicates={:?}", predicates.predicates);
501 predicates.predicates
503 .flat_map(|p| ty::wf::predicate_obligations(fcx,
509 for obligation in wf_obligations.chain(default_obligations) {
510 debug!("next obligation cause: {:?}", obligation.cause);
511 fcx.register_predicate(obligation);
515 fn check_fn_or_method<'a, 'fcx, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'gcx>,
516 fcx: &FnCtxt<'fcx, 'gcx, 'tcx>,
518 sig: ty::PolyFnSig<'tcx>,
520 implied_bounds: &mut Vec<Ty<'tcx>>)
522 let sig = fcx.normalize_associated_types_in(span, &sig);
523 let sig = fcx.tcx.liberate_late_bound_regions(def_id, &sig);
525 for input_ty in sig.inputs() {
526 fcx.register_wf_obligation(&input_ty, span, ObligationCauseCode::MiscObligation);
528 implied_bounds.extend(sig.inputs());
530 fcx.register_wf_obligation(sig.output(), span, ObligationCauseCode::MiscObligation);
532 // FIXME(#25759) return types should not be implied bounds
533 implied_bounds.push(sig.output());
535 check_where_clauses(tcx, fcx, span, def_id, Some(sig.output()));
538 fn check_existential_types<'a, 'fcx, 'gcx, 'tcx>(
539 tcx: TyCtxt<'a, 'gcx, 'gcx>,
540 fcx: &FnCtxt<'fcx, 'gcx, 'tcx>,
544 ) -> Vec<ty::Predicate<'tcx>> {
545 trace!("check_existential_types: {:?}, {:?}", ty, ty.sty);
546 let mut substituted_predicates = Vec::new();
547 ty.fold_with(&mut ty::fold::BottomUpFolder {
550 if let ty::TyAnon(def_id, substs) = ty.sty {
551 trace!("check_existential_types: anon_ty, {:?}, {:?}", def_id, substs);
552 let generics = tcx.generics_of(def_id);
553 // only check named existential types
554 if generics.parent.is_none() {
555 let anon_node_id = tcx.hir.as_local_node_id(def_id).unwrap();
556 if may_define_existential_type(tcx, fn_def_id, anon_node_id) {
557 trace!("check_existential_types may define. Generics: {:#?}", generics);
558 for (subst, param) in substs.iter().zip(&generics.params) {
559 if let ty::subst::UnpackedKind::Type(ty) = subst.unpack() {
561 ty::TyParam(..) => {},
562 // prevent `fn foo() -> Foo<u32>` from being defining
568 "non-defining existential type use \
572 tcx.def_span(param.def_id),
574 "used non-generic type {} for \
580 return tcx.types.err;
583 } // if let Type = subst
584 } // for (subst, param)
585 } // if may_define_existential_type
587 // now register the bounds on the parameters of the existential type
588 // so the parameters given by the function need to fulfil them
590 // existential type Foo<T: Bar>: 'static;
591 // fn foo<U>() -> Foo<U> { .. *}
595 // existential type Foo<T: Bar>: 'static;
596 // fn foo<U: Bar>() -> Foo<U> { .. *}
598 let predicates = tcx.predicates_of(def_id);
600 "check_existential_types may define. adding predicates: {:#?}",
603 for &pred in predicates.predicates.iter() {
604 let substituted_pred = pred.subst(fcx.tcx, substs);
605 // Avoid duplication of predicates that contain no parameters, for example.
606 if !predicates.predicates.contains(&substituted_pred) {
607 substituted_predicates.push(substituted_pred);
610 } // if is_named_existential_type
615 substituted_predicates
618 fn check_method_receiver<'fcx, 'gcx, 'tcx>(fcx: &FnCtxt<'fcx, 'gcx, 'tcx>,
619 method_sig: &hir::MethodSig,
620 method: &ty::AssociatedItem,
623 // check that the method has a valid receiver type, given the type `Self`
624 debug!("check_method_receiver({:?}, self_ty={:?})",
627 if !method.method_has_self_argument {
631 let span = method_sig.decl.inputs[0].span;
633 let sig = fcx.tcx.fn_sig(method.def_id);
634 let sig = fcx.normalize_associated_types_in(span, &sig);
635 let sig = fcx.tcx.liberate_late_bound_regions(method.def_id, &sig);
637 debug!("check_method_receiver: sig={:?}", sig);
639 let self_ty = fcx.normalize_associated_types_in(span, &self_ty);
640 let self_ty = fcx.tcx.liberate_late_bound_regions(
642 &ty::Binder::bind(self_ty)
645 let self_arg_ty = sig.inputs()[0];
647 let cause = fcx.cause(span, ObligationCauseCode::MethodReceiver);
648 let self_arg_ty = fcx.normalize_associated_types_in(span, &self_arg_ty);
649 let self_arg_ty = fcx.tcx.liberate_late_bound_regions(
651 &ty::Binder::bind(self_arg_ty)
654 let mut autoderef = fcx.autoderef(span, self_arg_ty).include_raw_pointers();
657 if let Some((potential_self_ty, _)) = autoderef.next() {
658 debug!("check_method_receiver: potential self type `{:?}` to match `{:?}`",
659 potential_self_ty, self_ty);
661 if fcx.infcx.can_eq(fcx.param_env, self_ty, potential_self_ty).is_ok() {
662 autoderef.finalize();
663 if let Some(mut err) = fcx.demand_eqtype_with_origin(
664 &cause, self_ty, potential_self_ty) {
670 fcx.tcx.sess.diagnostic().mut_span_err(
671 span, &format!("invalid `self` type: {:?}", self_arg_ty))
672 .note(&format!("type must be `{:?}` or a type that dereferences to it", self_ty))
673 .help("consider changing to `self`, `&self`, `&mut self`, or `self: Box<Self>`")
674 .code(DiagnosticId::Error("E0307".into()))
680 let is_self_ty = |ty| fcx.infcx.can_eq(fcx.param_env, self_ty, ty).is_ok();
681 let self_kind = ExplicitSelf::determine(self_arg_ty, is_self_ty);
683 if !fcx.tcx.features().arbitrary_self_types {
685 ExplicitSelf::ByValue |
686 ExplicitSelf::ByReference(_, _) |
687 ExplicitSelf::ByBox => (),
689 ExplicitSelf::ByRawPointer(_) => {
690 feature_gate::feature_err(
691 &fcx.tcx.sess.parse_sess,
692 "arbitrary_self_types",
695 "raw pointer `self` is unstable")
696 .help("consider changing to `self`, `&self`, `&mut self`, or `self: Box<Self>`")
700 ExplicitSelf::Other => {
701 feature_gate::feature_err(
702 &fcx.tcx.sess.parse_sess,
703 "arbitrary_self_types",
705 GateIssue::Language,"arbitrary `self` types are unstable")
706 .help("consider changing to `self`, `&self`, `&mut self`, or `self: Box<Self>`")
713 fn check_variances_for_type_defn<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
715 hir_generics: &hir::Generics)
717 let item_def_id = tcx.hir.local_def_id(item.id);
718 let ty = tcx.type_of(item_def_id);
719 if tcx.has_error_field(ty) {
723 let ty_predicates = tcx.predicates_of(item_def_id);
724 assert_eq!(ty_predicates.parent, None);
725 let variances = tcx.variances_of(item_def_id);
727 let mut constrained_parameters: FxHashSet<_> =
728 variances.iter().enumerate()
729 .filter(|&(_, &variance)| variance != ty::Bivariant)
730 .map(|(index, _)| Parameter(index as u32))
733 identify_constrained_type_params(tcx,
734 ty_predicates.predicates.as_slice(),
736 &mut constrained_parameters);
738 for (index, _) in variances.iter().enumerate() {
739 if constrained_parameters.contains(&Parameter(index as u32)) {
743 let param = &hir_generics.params[index];
744 report_bivariance(tcx, param.span, param.name.ident().name);
748 fn report_bivariance<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
750 param_name: ast::Name)
752 let mut err = error_392(tcx, span, param_name);
754 let suggested_marker_id = tcx.lang_items().phantom_data();
755 match suggested_marker_id {
758 &format!("consider removing `{}` or using a marker such as `{}`",
760 tcx.item_path_str(def_id)));
763 // no lang items, no help!
769 fn reject_shadowing_parameters(tcx: TyCtxt, def_id: DefId) {
770 let generics = tcx.generics_of(def_id);
771 let parent = tcx.generics_of(generics.parent.unwrap());
772 let impl_params: FxHashMap<_, _> = parent.params.iter().flat_map(|param| match param.kind {
773 GenericParamDefKind::Lifetime => None,
774 GenericParamDefKind::Type {..} => Some((param.name, param.def_id)),
777 for method_param in &generics.params {
778 match method_param.kind {
779 // Shadowing is checked in resolve_lifetime.
780 GenericParamDefKind::Lifetime => continue,
783 if impl_params.contains_key(&method_param.name) {
784 // Tighten up the span to focus on only the shadowing type
785 let type_span = tcx.def_span(method_param.def_id);
787 // The expectation here is that the original trait declaration is
788 // local so it should be okay to just unwrap everything.
789 let trait_def_id = impl_params[&method_param.name];
790 let trait_decl_span = tcx.def_span(trait_def_id);
791 error_194(tcx, type_span, trait_decl_span, &method_param.name.as_str()[..]);
796 /// Feature gates RFC 2056 - trivial bounds, checking for global bounds that
798 fn check_false_global_bounds<'a, 'gcx, 'tcx>(
799 fcx: &FnCtxt<'a, 'gcx, 'tcx>,
803 use rustc::ty::TypeFoldable;
805 let empty_env = ty::ParamEnv::empty();
807 let def_id = fcx.tcx.hir.local_def_id(id);
808 let predicates = fcx.tcx.predicates_of(def_id).predicates;
809 // Check elaborated bounds
810 let implied_obligations = traits::elaborate_predicates(fcx.tcx, predicates);
812 for pred in implied_obligations {
813 // Match the existing behavior.
814 if pred.is_global() && !pred.has_late_bound_regions() {
815 let pred = fcx.normalize_associated_types_in(span, &pred);
816 let obligation = traits::Obligation::new(
817 traits::ObligationCause::new(
820 traits::TrivialBound,
825 fcx.register_predicate(obligation);
829 fcx.select_all_obligations_or_error();
832 pub struct CheckTypeWellFormedVisitor<'a, 'tcx: 'a> {
833 tcx: TyCtxt<'a, 'tcx, 'tcx>,
836 impl<'a, 'gcx> CheckTypeWellFormedVisitor<'a, 'gcx> {
837 pub fn new(tcx: TyCtxt<'a, 'gcx, 'gcx>)
838 -> CheckTypeWellFormedVisitor<'a, 'gcx> {
839 CheckTypeWellFormedVisitor {
845 impl<'a, 'tcx, 'v> Visitor<'v> for CheckTypeWellFormedVisitor<'a, 'tcx> {
846 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'v> {
847 NestedVisitorMap::None
850 fn visit_item(&mut self, i: &hir::Item) {
851 debug!("visit_item: {:?}", i);
852 let def_id = self.tcx.hir.local_def_id(i.id);
853 ty::query::queries::check_item_well_formed::ensure(self.tcx, def_id);
854 intravisit::walk_item(self, i);
857 fn visit_trait_item(&mut self, trait_item: &'v hir::TraitItem) {
858 debug!("visit_trait_item: {:?}", trait_item);
859 let def_id = self.tcx.hir.local_def_id(trait_item.id);
860 ty::query::queries::check_trait_item_well_formed::ensure(self.tcx, def_id);
861 intravisit::walk_trait_item(self, trait_item)
864 fn visit_impl_item(&mut self, impl_item: &'v hir::ImplItem) {
865 debug!("visit_impl_item: {:?}", impl_item);
866 let def_id = self.tcx.hir.local_def_id(impl_item.id);
867 ty::query::queries::check_impl_item_well_formed::ensure(self.tcx, def_id);
868 intravisit::walk_impl_item(self, impl_item)
872 ///////////////////////////////////////////////////////////////////////////
875 struct AdtVariant<'tcx> {
876 fields: Vec<AdtField<'tcx>>,
879 struct AdtField<'tcx> {
884 impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
885 fn non_enum_variant(&self, struct_def: &hir::VariantData) -> AdtVariant<'tcx> {
887 struct_def.fields().iter()
889 let field_ty = self.tcx.type_of(self.tcx.hir.local_def_id(field.id));
890 let field_ty = self.normalize_associated_types_in(field.span,
892 AdtField { ty: field_ty, span: field.span }
895 AdtVariant { fields: fields }
898 fn enum_variants(&self, enum_def: &hir::EnumDef) -> Vec<AdtVariant<'tcx>> {
899 enum_def.variants.iter()
900 .map(|variant| self.non_enum_variant(&variant.node.data))
904 fn impl_implied_bounds(&self, impl_def_id: DefId, span: Span) -> Vec<Ty<'tcx>> {
905 match self.tcx.impl_trait_ref(impl_def_id) {
906 Some(ref trait_ref) => {
907 // Trait impl: take implied bounds from all types that
908 // appear in the trait reference.
909 let trait_ref = self.normalize_associated_types_in(span, trait_ref);
910 trait_ref.substs.types().collect()
914 // Inherent impl: take implied bounds from the self type.
915 let self_ty = self.tcx.type_of(impl_def_id);
916 let self_ty = self.normalize_associated_types_in(span, &self_ty);
923 fn error_392<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, span: Span, param_name: ast::Name)
924 -> DiagnosticBuilder<'tcx> {
925 let mut err = struct_span_err!(tcx.sess, span, E0392,
926 "parameter `{}` is never used", param_name);
927 err.span_label(span, "unused type parameter");
931 fn error_194(tcx: TyCtxt, span: Span, trait_decl_span: Span, name: &str) {
932 struct_span_err!(tcx.sess, span, E0194,
933 "type parameter `{}` shadows another type parameter of the same name",
935 .span_label(span, "shadows another type parameter")
936 .span_label(trait_decl_span, format!("first `{}` declared here", name))