1 use crate::check::regionck::OutlivesEnvironmentExt;
2 use crate::check::{FnCtxt, Inherited};
3 use crate::constrained_generic_params::{identify_constrained_generic_params, Parameter};
4
5 use rustc_ast as ast;
6 use rustc_data_structures::fx::FxHashSet;
7 use rustc_errors::{struct_span_err, Applicability, DiagnosticBuilder};
8 use rustc_hir as hir;
9 use rustc_hir::def_id::{DefId, LocalDefId};
10 use rustc_hir::intravisit as hir_visit;
11 use rustc_hir::intravisit::Visitor;
12 use rustc_hir::itemlikevisit::ParItemLikeVisitor;
13 use rustc_hir::lang_items::LangItem;
14 use rustc_hir::ItemKind;
15 use rustc_infer::infer::outlives::env::OutlivesEnvironment;
16 use rustc_infer::infer::outlives::obligations::TypeOutlives;
17 use rustc_infer::infer::TyCtxtInferExt;
18 use rustc_infer::infer::{self, RegionckMode, SubregionOrigin};
19 use rustc_middle::hir::map as hir_map;
20 use rustc_middle::ty::subst::{GenericArgKind, InternalSubsts, Subst};
21 use rustc_middle::ty::trait_def::TraitSpecializationKind;
22 use rustc_middle::ty::{
23 self, AdtKind, GenericParamDefKind, ToPredicate, Ty, TyCtxt, TypeFoldable, TypeVisitor,
24 WithConstness,
25 };
26 use rustc_session::parse::feature_err;
27 use rustc_span::symbol::{sym, Ident, Symbol};
28 use rustc_span::{Span, DUMMY_SP};
29 use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt as _;
30 use rustc_trait_selection::traits::{self, ObligationCause, ObligationCauseCode, WellFormedLoc};
31
32 use std::convert::TryInto;
33 use std::iter;
34 use std::ops::ControlFlow;
35
36 /// Helper type of a temporary returned by `.for_item(...)`.
37 /// This is necessary because we can't write the following bound:
38 ///
39 /// ```rust
40 /// F: for<'b, 'tcx> where 'tcx FnOnce(FnCtxt<'b, 'tcx>)
41 /// ```
42 struct CheckWfFcxBuilder<'tcx> {
43 inherited: super::InheritedBuilder<'tcx>,
44 id: hir::HirId,
45 span: Span,
46 param_env: ty::ParamEnv<'tcx>,
47 }
48
49 impl<'tcx> CheckWfFcxBuilder<'tcx> {
with_fcx<F>(&mut self, f: F) where F: for<'b> FnOnce(&FnCtxt<'b, 'tcx>) -> FxHashSet<Ty<'tcx>>,50 fn with_fcx<F>(&mut self, f: F)
51 where
52 F: for<'b> FnOnce(&FnCtxt<'b, 'tcx>) -> FxHashSet<Ty<'tcx>>,
53 {
54 let id = self.id;
55 let span = self.span;
56 let param_env = self.param_env;
57 self.inherited.enter(|inh| {
58 let fcx = FnCtxt::new(&inh, param_env, id);
59 if !inh.tcx.features().trivial_bounds {
60 // As predicates are cached rather than obligations, this
61 // needs to be called first so that they are checked with an
62 // empty `param_env`.
63 check_false_global_bounds(&fcx, span, id);
64 }
65 let wf_tys = f(&fcx);
66 fcx.select_all_obligations_or_error();
67 fcx.regionck_item(id, span, wf_tys);
68 });
69 }
70 }
71
72 /// Checks that the field types (in a struct def'n) or argument types (in an enum def'n) are
73 /// well-formed, meaning that they do not require any constraints not declared in the struct
74 /// definition itself. For example, this definition would be illegal:
75 ///
76 /// ```rust
77 /// struct Ref<'a, T> { x: &'a T }
78 /// ```
79 ///
80 /// because the type did not declare that `T:'a`.
81 ///
82 /// We do this check as a pre-pass before checking fn bodies because if these constraints are
83 /// not included it frequently leads to confusing errors in fn bodies. So it's better to check
84 /// the types first.
85 #[instrument(skip(tcx), level = "debug")]
check_item_well_formed(tcx: TyCtxt<'_>, def_id: LocalDefId)86 pub fn check_item_well_formed(tcx: TyCtxt<'_>, def_id: LocalDefId) {
87 let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
88 let item = tcx.hir().expect_item(hir_id);
89
90 debug!(
91 ?item.def_id,
92 item.name = ? tcx.def_path_str(def_id.to_def_id())
93 );
94
95 match item.kind {
96 // Right now we check that every default trait implementation
97 // has an implementation of itself. Basically, a case like:
98 //
99 // impl Trait for T {}
100 //
101 // has a requirement of `T: Trait` which was required for default
102 // method implementations. Although this could be improved now that
103 // there's a better infrastructure in place for this, it's being left
104 // for a follow-up work.
105 //
106 // Since there's such a requirement, we need to check *just* positive
107 // implementations, otherwise things like:
108 //
109 // impl !Send for T {}
110 //
111 // won't be allowed unless there's an *explicit* implementation of `Send`
112 // for `T`
113 hir::ItemKind::Impl(ref impl_) => {
114 let is_auto = tcx
115 .impl_trait_ref(item.def_id)
116 .map_or(false, |trait_ref| tcx.trait_is_auto(trait_ref.def_id));
117 if let (hir::Defaultness::Default { .. }, true) = (impl_.defaultness, is_auto) {
118 let sp = impl_.of_trait.as_ref().map_or(item.span, |t| t.path.span);
119 let mut err =
120 tcx.sess.struct_span_err(sp, "impls of auto traits cannot be default");
121 err.span_labels(impl_.defaultness_span, "default because of this");
122 err.span_label(sp, "auto trait");
123 err.emit();
124 }
125 // We match on both `ty::ImplPolarity` and `ast::ImplPolarity` just to get the `!` span.
126 match (tcx.impl_polarity(def_id), impl_.polarity) {
127 (ty::ImplPolarity::Positive, _) => {
128 check_impl(tcx, item, impl_.self_ty, &impl_.of_trait);
129 }
130 (ty::ImplPolarity::Negative, ast::ImplPolarity::Negative(span)) => {
131 // FIXME(#27579): what amount of WF checking do we need for neg impls?
132 if let hir::Defaultness::Default { .. } = impl_.defaultness {
133 let mut spans = vec![span];
134 spans.extend(impl_.defaultness_span);
135 struct_span_err!(
136 tcx.sess,
137 spans,
138 E0750,
139 "negative impls cannot be default impls"
140 )
141 .emit();
142 }
143 }
144 (ty::ImplPolarity::Reservation, _) => {
145 // FIXME: what amount of WF checking do we need for reservation impls?
146 }
147 _ => unreachable!(),
148 }
149 }
150 hir::ItemKind::Fn(ref sig, ..) => {
151 check_item_fn(tcx, item.def_id, item.ident, item.span, sig.decl);
152 }
153 hir::ItemKind::Static(ty, ..) => {
154 check_item_type(tcx, item.def_id, ty.span, false);
155 }
156 hir::ItemKind::Const(ty, ..) => {
157 check_item_type(tcx, item.def_id, ty.span, false);
158 }
159 hir::ItemKind::ForeignMod { items, .. } => {
160 for it in items.iter() {
161 let it = tcx.hir().foreign_item(it.id);
162 match it.kind {
163 hir::ForeignItemKind::Fn(decl, ..) => {
164 check_item_fn(tcx, it.def_id, it.ident, it.span, decl)
165 }
166 hir::ForeignItemKind::Static(ty, ..) => {
167 check_item_type(tcx, it.def_id, ty.span, true)
168 }
169 hir::ForeignItemKind::Type => (),
170 }
171 }
172 }
173 hir::ItemKind::Struct(ref struct_def, ref ast_generics) => {
174 check_type_defn(tcx, item, false, |fcx| vec![fcx.non_enum_variant(struct_def)]);
175
176 check_variances_for_type_defn(tcx, item, ast_generics);
177 }
178 hir::ItemKind::Union(ref struct_def, ref ast_generics) => {
179 check_type_defn(tcx, item, true, |fcx| vec![fcx.non_enum_variant(struct_def)]);
180
181 check_variances_for_type_defn(tcx, item, ast_generics);
182 }
183 hir::ItemKind::Enum(ref enum_def, ref ast_generics) => {
184 check_type_defn(tcx, item, true, |fcx| fcx.enum_variants(enum_def));
185
186 check_variances_for_type_defn(tcx, item, ast_generics);
187 }
188 hir::ItemKind::Trait(..) => {
189 check_trait(tcx, item);
190 }
191 hir::ItemKind::TraitAlias(..) => {
192 check_trait(tcx, item);
193 }
194 _ => {}
195 }
196 }
197
check_trait_item(tcx: TyCtxt<'_>, def_id: LocalDefId)198 pub fn check_trait_item(tcx: TyCtxt<'_>, def_id: LocalDefId) {
199 let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
200 let trait_item = tcx.hir().expect_trait_item(hir_id);
201
202 let (method_sig, span) = match trait_item.kind {
203 hir::TraitItemKind::Fn(ref sig, _) => (Some(sig), trait_item.span),
204 hir::TraitItemKind::Type(_bounds, Some(ty)) => (None, ty.span),
205 _ => (None, trait_item.span),
206 };
207 check_object_unsafe_self_trait_by_name(tcx, trait_item);
208 check_associated_item(tcx, trait_item.def_id, span, method_sig);
209
210 let encl_trait_hir_id = tcx.hir().get_parent_item(hir_id);
211 let encl_trait = tcx.hir().expect_item(encl_trait_hir_id);
212 let encl_trait_def_id = encl_trait.def_id.to_def_id();
213 let fn_lang_item_name = if Some(encl_trait_def_id) == tcx.lang_items().fn_trait() {
214 Some("fn")
215 } else if Some(encl_trait_def_id) == tcx.lang_items().fn_mut_trait() {
216 Some("fn_mut")
217 } else {
218 None
219 };
220
221 if let (Some(fn_lang_item_name), "call") =
222 (fn_lang_item_name, trait_item.ident.name.to_ident_string().as_str())
223 {
224 // We are looking at the `call` function of the `fn` or `fn_mut` lang item.
225 // Do some rudimentary sanity checking to avoid an ICE later (issue #83471).
226 if let Some(hir::FnSig { decl, span, .. }) = method_sig {
227 if let [self_ty, _] = decl.inputs {
228 if !matches!(self_ty.kind, hir::TyKind::Rptr(_, _)) {
229 tcx.sess
230 .struct_span_err(
231 self_ty.span,
232 &format!(
233 "first argument of `call` in `{}` lang item must be a reference",
234 fn_lang_item_name
235 ),
236 )
237 .emit();
238 }
239 } else {
240 tcx.sess
241 .struct_span_err(
242 *span,
243 &format!(
244 "`call` function in `{}` lang item takes exactly two arguments",
245 fn_lang_item_name
246 ),
247 )
248 .emit();
249 }
250 } else {
251 tcx.sess
252 .struct_span_err(
253 trait_item.span,
254 &format!(
255 "`call` trait item in `{}` lang item must be a function",
256 fn_lang_item_name
257 ),
258 )
259 .emit();
260 }
261 }
262
263 check_gat_where_clauses(tcx, trait_item, encl_trait_def_id);
264 }
265
266 /// Require that the user writes where clauses on GATs for the implicit
267 /// outlives bounds involving trait parameters in trait functions and
268 /// lifetimes passed as GAT substs. See `self-outlives-lint` test.
269 ///
270 /// This trait will be our running example. We are currently WF checking the `Item` item...
271 ///
272 /// ```rust
273 /// trait LendingIterator {
274 /// type Item<'me>; // <-- WF checking this trait item
275 ///
276 /// fn next<'a>(&'a mut self) -> Option<Self::Item<'a>>;
277 /// }
278 /// ```
check_gat_where_clauses( tcx: TyCtxt<'_>, trait_item: &hir::TraitItem<'_>, encl_trait_def_id: DefId, )279 fn check_gat_where_clauses(
280 tcx: TyCtxt<'_>,
281 trait_item: &hir::TraitItem<'_>,
282 encl_trait_def_id: DefId,
283 ) {
284 let item = tcx.associated_item(trait_item.def_id);
285 // If the current trait item isn't a type, it isn't a GAT
286 if !matches!(item.kind, ty::AssocKind::Type) {
287 return;
288 }
289 let generics: &ty::Generics = tcx.generics_of(trait_item.def_id);
290 // If the current associated type doesn't have any (own) params, it's not a GAT
291 // FIXME(jackh726): we can also warn in the more general case
292 if generics.params.len() == 0 {
293 return;
294 }
295 let associated_items: &ty::AssocItems<'_> = tcx.associated_items(encl_trait_def_id);
296 let mut clauses: Option<FxHashSet<ty::Predicate<'_>>> = None;
297 // For every function in this trait...
298 // In our example, this would be the `next` method
299 for item in
300 associated_items.in_definition_order().filter(|item| matches!(item.kind, ty::AssocKind::Fn))
301 {
302 // The clauses we that we would require from this function
303 let mut function_clauses = FxHashSet::default();
304
305 let id = hir::HirId::make_owner(item.def_id.expect_local());
306 let param_env = tcx.param_env(item.def_id.expect_local());
307
308 let sig = tcx.fn_sig(item.def_id);
309 // Get the signature using placeholders. In our example, this would
310 // convert the late-bound 'a into a free region.
311 let sig = tcx.liberate_late_bound_regions(item.def_id, sig);
312 // Collect the arguments that are given to this GAT in the return type
313 // of the function signature. In our example, the GAT in the return
314 // type is `<Self as LendingIterator>::Item<'a>`, so 'a and Self are arguments.
315 let (regions, types) =
316 GATSubstCollector::visit(tcx, trait_item.def_id.to_def_id(), sig.output());
317
318 // If both regions and types are empty, then this GAT isn't in the
319 // return type, and we shouldn't try to do clause analysis
320 // (particularly, doing so would end up with an empty set of clauses,
321 // since the current method would require none, and we take the
322 // intersection of requirements of all methods)
323 if types.is_empty() && regions.is_empty() {
324 continue;
325 }
326
327 // The types we can assume to be well-formed. In our example, this
328 // would be &'a mut Self, from the first argument.
329 let mut wf_tys = FxHashSet::default();
330 wf_tys.extend(sig.inputs());
331
332 // For each region argument (e.g., 'a in our example), check for a
333 // relationship to the type arguments (e.g., Self). If there is an
334 // outlives relationship (`Self: 'a`), then we want to ensure that is
335 // reflected in a where clause on the GAT itself.
336 for (region, region_idx) in ®ions {
337 for (ty, ty_idx) in &types {
338 // In our example, requires that Self: 'a
339 if ty_known_to_outlive(tcx, id, param_env, &wf_tys, *ty, *region) {
340 debug!(?ty_idx, ?region_idx);
341 debug!("required clause: {} must outlive {}", ty, region);
342 // Translate into the generic parameters of the GAT. In
343 // our example, the type was Self, which will also be
344 // Self in the GAT.
345 let ty_param = generics.param_at(*ty_idx, tcx);
346 let ty_param = tcx.mk_ty(ty::Param(ty::ParamTy {
347 index: ty_param.index,
348 name: ty_param.name,
349 }));
350 // Same for the region. In our example, 'a corresponds
351 // to the 'me parameter.
352 let region_param = generics.param_at(*region_idx, tcx);
353 let region_param =
354 tcx.mk_region(ty::RegionKind::ReEarlyBound(ty::EarlyBoundRegion {
355 def_id: region_param.def_id,
356 index: region_param.index,
357 name: region_param.name,
358 }));
359 // The predicate we expect to see. (In our example,
360 // `Self: 'me`.)
361 let clause = ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(
362 ty_param,
363 region_param,
364 ));
365 let clause = tcx.mk_predicate(ty::Binder::dummy(clause));
366 function_clauses.insert(clause);
367 }
368 }
369 }
370
371 // For each region argument (e.g., 'a in our example), also check for a
372 // relationship to the other region arguments. If there is an
373 // outlives relationship, then we want to ensure that is
374 // reflected in a where clause on the GAT itself.
375 for (region_a, region_a_idx) in ®ions {
376 for (region_b, region_b_idx) in ®ions {
377 if region_a == region_b {
378 continue;
379 }
380
381 if region_known_to_outlive(tcx, id, param_env, &wf_tys, *region_a, *region_b) {
382 debug!(?region_a_idx, ?region_b_idx);
383 debug!("required clause: {} must outlive {}", region_a, region_b);
384 // Translate into the generic parameters of the GAT.
385 let region_a_param = generics.param_at(*region_a_idx, tcx);
386 let region_a_param =
387 tcx.mk_region(ty::RegionKind::ReEarlyBound(ty::EarlyBoundRegion {
388 def_id: region_a_param.def_id,
389 index: region_a_param.index,
390 name: region_a_param.name,
391 }));
392 // Same for the region.
393 let region_b_param = generics.param_at(*region_b_idx, tcx);
394 let region_b_param =
395 tcx.mk_region(ty::RegionKind::ReEarlyBound(ty::EarlyBoundRegion {
396 def_id: region_b_param.def_id,
397 index: region_b_param.index,
398 name: region_b_param.name,
399 }));
400 // The predicate we expect to see.
401 let clause = ty::PredicateKind::RegionOutlives(ty::OutlivesPredicate(
402 region_a_param,
403 region_b_param,
404 ));
405 let clause = tcx.mk_predicate(ty::Binder::dummy(clause));
406 function_clauses.insert(clause);
407 }
408 }
409 }
410
411 // Imagine we have:
412 // ```
413 // trait Foo {
414 // type Bar<'me>;
415 // fn gimme(&self) -> Self::Bar<'_>;
416 // fn gimme_default(&self) -> Self::Bar<'static>;
417 // }
418 // ```
419 // We only want to require clauses on `Bar` that we can prove from *all* functions (in this
420 // case, `'me` can be `static` from `gimme_default`)
421 match clauses.as_mut() {
422 Some(clauses) => {
423 clauses.drain_filter(|p| !function_clauses.contains(p));
424 }
425 None => {
426 clauses = Some(function_clauses);
427 }
428 }
429 }
430
431 // If there are any missing clauses, emit an error
432 let mut clauses = clauses.unwrap_or_default();
433 debug!(?clauses);
434 if !clauses.is_empty() {
435 let written_predicates: ty::GenericPredicates<'_> =
436 tcx.explicit_predicates_of(trait_item.def_id);
437 let mut clauses: Vec<_> = clauses
438 .drain_filter(|clause| !written_predicates.predicates.iter().any(|p| &p.0 == clause))
439 .map(|clause| format!("{}", clause))
440 .collect();
441 // We sort so that order is predictable
442 clauses.sort();
443 if !clauses.is_empty() {
444 let mut err = tcx.sess.struct_span_err(
445 trait_item.span,
446 &format!("Missing required bounds on {}", trait_item.ident),
447 );
448
449 let suggestion = format!(
450 "{} {}",
451 if !trait_item.generics.where_clause.predicates.is_empty() {
452 ","
453 } else {
454 " where"
455 },
456 clauses.join(", "),
457 );
458 err.span_suggestion(
459 trait_item.generics.where_clause.tail_span_for_suggestion(),
460 "add the required where clauses",
461 suggestion,
462 Applicability::MachineApplicable,
463 );
464
465 err.emit()
466 }
467 }
468 }
469
470 // FIXME(jackh726): refactor some of the shared logic between the two functions below
471
472 /// Given a known `param_env` and a set of well formed types, can we prove that
473 /// `ty` outlives `region`.
ty_known_to_outlive<'tcx>( tcx: TyCtxt<'tcx>, id: hir::HirId, param_env: ty::ParamEnv<'tcx>, wf_tys: &FxHashSet<Ty<'tcx>>, ty: Ty<'tcx>, region: ty::Region<'tcx>, ) -> bool474 fn ty_known_to_outlive<'tcx>(
475 tcx: TyCtxt<'tcx>,
476 id: hir::HirId,
477 param_env: ty::ParamEnv<'tcx>,
478 wf_tys: &FxHashSet<Ty<'tcx>>,
479 ty: Ty<'tcx>,
480 region: ty::Region<'tcx>,
481 ) -> bool {
482 // Unfortunately, we have to use a new `InferCtxt` each call, because
483 // region constraints get added and solved there and we need to test each
484 // call individually.
485 tcx.infer_ctxt().enter(|infcx| {
486 let mut outlives_environment = OutlivesEnvironment::new(param_env);
487 outlives_environment.add_implied_bounds(&infcx, wf_tys.clone(), id, DUMMY_SP);
488 outlives_environment.save_implied_bounds(id);
489 let region_bound_pairs = outlives_environment.region_bound_pairs_map().get(&id).unwrap();
490
491 let cause = ObligationCause::new(DUMMY_SP, id, ObligationCauseCode::MiscObligation);
492
493 let sup_type = ty;
494 let sub_region = region;
495
496 let origin = SubregionOrigin::from_obligation_cause(&cause, || {
497 infer::RelateParamBound(cause.span, sup_type, None)
498 });
499
500 let outlives = &mut TypeOutlives::new(
501 &infcx,
502 tcx,
503 ®ion_bound_pairs,
504 Some(infcx.tcx.lifetimes.re_root_empty),
505 param_env,
506 );
507 outlives.type_must_outlive(origin, sup_type, sub_region);
508
509 let errors = infcx.resolve_regions(
510 id.expect_owner().to_def_id(),
511 &outlives_environment,
512 RegionckMode::default(),
513 );
514
515 debug!(?errors, "errors");
516
517 // If we were able to prove that the type outlives the region without
518 // an error, it must be because of the implied or explicit bounds...
519 errors.is_empty()
520 })
521 }
522
region_known_to_outlive<'tcx>( tcx: TyCtxt<'tcx>, id: hir::HirId, param_env: ty::ParamEnv<'tcx>, wf_tys: &FxHashSet<Ty<'tcx>>, region_a: ty::Region<'tcx>, region_b: ty::Region<'tcx>, ) -> bool523 fn region_known_to_outlive<'tcx>(
524 tcx: TyCtxt<'tcx>,
525 id: hir::HirId,
526 param_env: ty::ParamEnv<'tcx>,
527 wf_tys: &FxHashSet<Ty<'tcx>>,
528 region_a: ty::Region<'tcx>,
529 region_b: ty::Region<'tcx>,
530 ) -> bool {
531 // Unfortunately, we have to use a new `InferCtxt` each call, because
532 // region constraints get added and solved there and we need to test each
533 // call individually.
534 tcx.infer_ctxt().enter(|infcx| {
535 let mut outlives_environment = OutlivesEnvironment::new(param_env);
536 outlives_environment.add_implied_bounds(&infcx, wf_tys.clone(), id, DUMMY_SP);
537 outlives_environment.save_implied_bounds(id);
538
539 let cause = ObligationCause::new(DUMMY_SP, id, ObligationCauseCode::MiscObligation);
540
541 let origin = SubregionOrigin::from_obligation_cause(&cause, || {
542 infer::RelateRegionParamBound(cause.span)
543 });
544
545 use rustc_infer::infer::outlives::obligations::TypeOutlivesDelegate;
546 (&infcx).push_sub_region_constraint(origin, region_a, region_b);
547
548 let errors = infcx.resolve_regions(
549 id.expect_owner().to_def_id(),
550 &outlives_environment,
551 RegionckMode::default(),
552 );
553
554 debug!(?errors, "errors");
555
556 // If we were able to prove that the type outlives the region without
557 // an error, it must be because of the implied or explicit bounds...
558 errors.is_empty()
559 })
560 }
561
562 /// TypeVisitor that looks for uses of GATs like
563 /// `<P0 as Trait<P1..Pn>>::GAT<Pn..Pm>` and adds the arguments `P0..Pm` into
564 /// the two vectors, `regions` and `types` (depending on their kind). For each
565 /// parameter `Pi` also track the index `i`.
566 struct GATSubstCollector<'tcx> {
567 tcx: TyCtxt<'tcx>,
568 gat: DefId,
569 // Which region appears and which parameter index its subsituted for
570 regions: FxHashSet<(ty::Region<'tcx>, usize)>,
571 // Which params appears and which parameter index its subsituted for
572 types: FxHashSet<(Ty<'tcx>, usize)>,
573 }
574
575 impl<'tcx> GATSubstCollector<'tcx> {
visit<T: TypeFoldable<'tcx>>( tcx: TyCtxt<'tcx>, gat: DefId, t: T, ) -> (FxHashSet<(ty::Region<'tcx>, usize)>, FxHashSet<(Ty<'tcx>, usize)>)576 fn visit<T: TypeFoldable<'tcx>>(
577 tcx: TyCtxt<'tcx>,
578 gat: DefId,
579 t: T,
580 ) -> (FxHashSet<(ty::Region<'tcx>, usize)>, FxHashSet<(Ty<'tcx>, usize)>) {
581 let mut visitor = GATSubstCollector {
582 tcx,
583 gat,
584 regions: FxHashSet::default(),
585 types: FxHashSet::default(),
586 };
587 t.visit_with(&mut visitor);
588 (visitor.regions, visitor.types)
589 }
590 }
591
592 impl<'tcx> TypeVisitor<'tcx> for GATSubstCollector<'tcx> {
593 type BreakTy = !;
594
visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy>595 fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
596 match t.kind() {
597 ty::Projection(p) if p.item_def_id == self.gat => {
598 for (idx, subst) in p.substs.iter().enumerate() {
599 match subst.unpack() {
600 GenericArgKind::Lifetime(lt) => {
601 self.regions.insert((lt, idx));
602 }
603 GenericArgKind::Type(t) => {
604 self.types.insert((t, idx));
605 }
606 _ => {}
607 }
608 }
609 }
610 _ => {}
611 }
612 t.super_visit_with(self)
613 }
614
tcx_for_anon_const_substs(&self) -> Option<TyCtxt<'tcx>>615 fn tcx_for_anon_const_substs(&self) -> Option<TyCtxt<'tcx>> {
616 Some(self.tcx)
617 }
618 }
619
could_be_self(trait_def_id: LocalDefId, ty: &hir::Ty<'_>) -> bool620 fn could_be_self(trait_def_id: LocalDefId, ty: &hir::Ty<'_>) -> bool {
621 match ty.kind {
622 hir::TyKind::TraitObject([trait_ref], ..) => match trait_ref.trait_ref.path.segments {
623 [s] => s.res.and_then(|r| r.opt_def_id()) == Some(trait_def_id.to_def_id()),
624 _ => false,
625 },
626 _ => false,
627 }
628 }
629
630 /// Detect when an object unsafe trait is referring to itself in one of its associated items.
631 /// When this is done, suggest using `Self` instead.
check_object_unsafe_self_trait_by_name(tcx: TyCtxt<'_>, item: &hir::TraitItem<'_>)632 fn check_object_unsafe_self_trait_by_name(tcx: TyCtxt<'_>, item: &hir::TraitItem<'_>) {
633 let (trait_name, trait_def_id) = match tcx.hir().get(tcx.hir().get_parent_item(item.hir_id())) {
634 hir::Node::Item(item) => match item.kind {
635 hir::ItemKind::Trait(..) => (item.ident, item.def_id),
636 _ => return,
637 },
638 _ => return,
639 };
640 let mut trait_should_be_self = vec![];
641 match &item.kind {
642 hir::TraitItemKind::Const(ty, _) | hir::TraitItemKind::Type(_, Some(ty))
643 if could_be_self(trait_def_id, ty) =>
644 {
645 trait_should_be_self.push(ty.span)
646 }
647 hir::TraitItemKind::Fn(sig, _) => {
648 for ty in sig.decl.inputs {
649 if could_be_self(trait_def_id, ty) {
650 trait_should_be_self.push(ty.span);
651 }
652 }
653 match sig.decl.output {
654 hir::FnRetTy::Return(ty) if could_be_self(trait_def_id, ty) => {
655 trait_should_be_self.push(ty.span);
656 }
657 _ => {}
658 }
659 }
660 _ => {}
661 }
662 if !trait_should_be_self.is_empty() {
663 if tcx.object_safety_violations(trait_def_id).is_empty() {
664 return;
665 }
666 let sugg = trait_should_be_self.iter().map(|span| (*span, "Self".to_string())).collect();
667 tcx.sess
668 .struct_span_err(
669 trait_should_be_self,
670 "associated item referring to unboxed trait object for its own trait",
671 )
672 .span_label(trait_name.span, "in this trait")
673 .multipart_suggestion(
674 "you might have meant to use `Self` to refer to the implementing type",
675 sugg,
676 Applicability::MachineApplicable,
677 )
678 .emit();
679 }
680 }
681
check_impl_item(tcx: TyCtxt<'_>, def_id: LocalDefId)682 pub fn check_impl_item(tcx: TyCtxt<'_>, def_id: LocalDefId) {
683 let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
684 let impl_item = tcx.hir().expect_impl_item(hir_id);
685
686 let (method_sig, span) = match impl_item.kind {
687 hir::ImplItemKind::Fn(ref sig, _) => (Some(sig), impl_item.span),
688 hir::ImplItemKind::TyAlias(ty) => (None, ty.span),
689 _ => (None, impl_item.span),
690 };
691
692 check_associated_item(tcx, impl_item.def_id, span, method_sig);
693 }
694
check_param_wf(tcx: TyCtxt<'_>, param: &hir::GenericParam<'_>)695 fn check_param_wf(tcx: TyCtxt<'_>, param: &hir::GenericParam<'_>) {
696 match param.kind {
697 // We currently only check wf of const params here.
698 hir::GenericParamKind::Lifetime { .. } | hir::GenericParamKind::Type { .. } => (),
699
700 // Const parameters are well formed if their type is structural match.
701 // FIXME(const_generics_defaults): we also need to check that the `default` is wf.
702 hir::GenericParamKind::Const { ty: hir_ty, default: _ } => {
703 let ty = tcx.type_of(tcx.hir().local_def_id(param.hir_id));
704
705 let err_ty_str;
706 let mut is_ptr = true;
707 let err = if tcx.features().adt_const_params {
708 match ty.peel_refs().kind() {
709 ty::FnPtr(_) => Some("function pointers"),
710 ty::RawPtr(_) => Some("raw pointers"),
711 _ => None,
712 }
713 } else {
714 match ty.kind() {
715 ty::Bool | ty::Char | ty::Int(_) | ty::Uint(_) | ty::Error(_) => None,
716 ty::FnPtr(_) => Some("function pointers"),
717 ty::RawPtr(_) => Some("raw pointers"),
718 _ => {
719 is_ptr = false;
720 err_ty_str = format!("`{}`", ty);
721 Some(err_ty_str.as_str())
722 }
723 }
724 };
725 if let Some(unsupported_type) = err {
726 if is_ptr {
727 tcx.sess.span_err(
728 hir_ty.span,
729 &format!(
730 "using {} as const generic parameters is forbidden",
731 unsupported_type
732 ),
733 )
734 } else {
735 let mut err = tcx.sess.struct_span_err(
736 hir_ty.span,
737 &format!(
738 "{} is forbidden as the type of a const generic parameter",
739 unsupported_type
740 ),
741 );
742 err.note("the only supported types are integers, `bool` and `char`");
743 if tcx.sess.is_nightly_build() {
744 err.help(
745 "more complex types are supported with `#![feature(adt_const_params)]`",
746 );
747 }
748 err.emit()
749 }
750 };
751
752 if traits::search_for_structural_match_violation(param.hir_id, param.span, tcx, ty)
753 .is_some()
754 {
755 // We use the same error code in both branches, because this is really the same
756 // issue: we just special-case the message for type parameters to make it
757 // clearer.
758 if let ty::Param(_) = ty.peel_refs().kind() {
759 // Const parameters may not have type parameters as their types,
760 // because we cannot be sure that the type parameter derives `PartialEq`
761 // and `Eq` (just implementing them is not enough for `structural_match`).
762 struct_span_err!(
763 tcx.sess,
764 hir_ty.span,
765 E0741,
766 "`{}` is not guaranteed to `#[derive(PartialEq, Eq)]`, so may not be \
767 used as the type of a const parameter",
768 ty,
769 )
770 .span_label(
771 hir_ty.span,
772 format!("`{}` may not derive both `PartialEq` and `Eq`", ty),
773 )
774 .note(
775 "it is not currently possible to use a type parameter as the type of a \
776 const parameter",
777 )
778 .emit();
779 } else {
780 struct_span_err!(
781 tcx.sess,
782 hir_ty.span,
783 E0741,
784 "`{}` must be annotated with `#[derive(PartialEq, Eq)]` to be used as \
785 the type of a const parameter",
786 ty,
787 )
788 .span_label(
789 hir_ty.span,
790 format!("`{}` doesn't derive both `PartialEq` and `Eq`", ty),
791 )
792 .emit();
793 }
794 }
795 }
796 }
797 }
798
799 #[tracing::instrument(level = "debug", skip(tcx, span, sig_if_method))]
check_associated_item( tcx: TyCtxt<'_>, item_id: LocalDefId, span: Span, sig_if_method: Option<&hir::FnSig<'_>>, )800 fn check_associated_item(
801 tcx: TyCtxt<'_>,
802 item_id: LocalDefId,
803 span: Span,
804 sig_if_method: Option<&hir::FnSig<'_>>,
805 ) {
806 let code = ObligationCauseCode::WellFormed(Some(WellFormedLoc::Ty(item_id)));
807 for_id(tcx, item_id, span).with_fcx(|fcx| {
808 let item = fcx.tcx.associated_item(item_id);
809
810 let (mut implied_bounds, self_ty) = match item.container {
811 ty::TraitContainer(_) => (FxHashSet::default(), fcx.tcx.types.self_param),
812 ty::ImplContainer(def_id) => {
813 (fcx.impl_implied_bounds(def_id, span), fcx.tcx.type_of(def_id))
814 }
815 };
816
817 match item.kind {
818 ty::AssocKind::Const => {
819 let ty = fcx.tcx.type_of(item.def_id);
820 let ty = fcx.normalize_associated_types_in_wf(span, ty, WellFormedLoc::Ty(item_id));
821 fcx.register_wf_obligation(ty.into(), span, code.clone());
822 }
823 ty::AssocKind::Fn => {
824 let sig = fcx.tcx.fn_sig(item.def_id);
825 let hir_sig = sig_if_method.expect("bad signature for method");
826 check_fn_or_method(
827 fcx,
828 item.ident.span,
829 sig,
830 hir_sig.decl,
831 item.def_id,
832 &mut implied_bounds,
833 );
834 check_method_receiver(fcx, hir_sig, item, self_ty);
835 }
836 ty::AssocKind::Type => {
837 if let ty::AssocItemContainer::TraitContainer(_) = item.container {
838 check_associated_type_bounds(fcx, item, span)
839 }
840 if item.defaultness.has_value() {
841 let ty = fcx.tcx.type_of(item.def_id);
842 let ty =
843 fcx.normalize_associated_types_in_wf(span, ty, WellFormedLoc::Ty(item_id));
844 fcx.register_wf_obligation(ty.into(), span, code.clone());
845 }
846 }
847 }
848
849 implied_bounds
850 })
851 }
852
for_item<'tcx>(tcx: TyCtxt<'tcx>, item: &hir::Item<'_>) -> CheckWfFcxBuilder<'tcx>853 fn for_item<'tcx>(tcx: TyCtxt<'tcx>, item: &hir::Item<'_>) -> CheckWfFcxBuilder<'tcx> {
854 for_id(tcx, item.def_id, item.span)
855 }
856
for_id(tcx: TyCtxt<'_>, def_id: LocalDefId, span: Span) -> CheckWfFcxBuilder<'_>857 fn for_id(tcx: TyCtxt<'_>, def_id: LocalDefId, span: Span) -> CheckWfFcxBuilder<'_> {
858 CheckWfFcxBuilder {
859 inherited: Inherited::build(tcx, def_id),
860 id: hir::HirId::make_owner(def_id),
861 span,
862 param_env: tcx.param_env(def_id),
863 }
864 }
865
item_adt_kind(kind: &ItemKind<'_>) -> Option<AdtKind>866 fn item_adt_kind(kind: &ItemKind<'_>) -> Option<AdtKind> {
867 match kind {
868 ItemKind::Struct(..) => Some(AdtKind::Struct),
869 ItemKind::Union(..) => Some(AdtKind::Union),
870 ItemKind::Enum(..) => Some(AdtKind::Enum),
871 _ => None,
872 }
873 }
874
875 /// In a type definition, we check that to ensure that the types of the fields are well-formed.
check_type_defn<'tcx, F>( tcx: TyCtxt<'tcx>, item: &hir::Item<'tcx>, all_sized: bool, mut lookup_fields: F, ) where F: for<'fcx> FnMut(&FnCtxt<'fcx, 'tcx>) -> Vec<AdtVariant<'tcx>>,876 fn check_type_defn<'tcx, F>(
877 tcx: TyCtxt<'tcx>,
878 item: &hir::Item<'tcx>,
879 all_sized: bool,
880 mut lookup_fields: F,
881 ) where
882 F: for<'fcx> FnMut(&FnCtxt<'fcx, 'tcx>) -> Vec<AdtVariant<'tcx>>,
883 {
884 for_item(tcx, item).with_fcx(|fcx| {
885 let variants = lookup_fields(fcx);
886 let packed = tcx.adt_def(item.def_id).repr.packed();
887
888 for variant in &variants {
889 // For DST, or when drop needs to copy things around, all
890 // intermediate types must be sized.
891 let needs_drop_copy = || {
892 packed && {
893 let ty = variant.fields.last().unwrap().ty;
894 let ty = tcx.erase_regions(ty);
895 if ty.needs_infer() {
896 tcx.sess
897 .delay_span_bug(item.span, &format!("inference variables in {:?}", ty));
898 // Just treat unresolved type expression as if it needs drop.
899 true
900 } else {
901 ty.needs_drop(tcx, tcx.param_env(item.def_id))
902 }
903 }
904 };
905 let all_sized = all_sized || variant.fields.is_empty() || needs_drop_copy();
906 let unsized_len = if all_sized { 0 } else { 1 };
907 for (idx, field) in
908 variant.fields[..variant.fields.len() - unsized_len].iter().enumerate()
909 {
910 let last = idx == variant.fields.len() - 1;
911 fcx.register_bound(
912 field.ty,
913 tcx.require_lang_item(LangItem::Sized, None),
914 traits::ObligationCause::new(
915 field.span,
916 fcx.body_id,
917 traits::FieldSized {
918 adt_kind: match item_adt_kind(&item.kind) {
919 Some(i) => i,
920 None => bug!(),
921 },
922 span: field.span,
923 last,
924 },
925 ),
926 );
927 }
928
929 // All field types must be well-formed.
930 for field in &variant.fields {
931 fcx.register_wf_obligation(
932 field.ty.into(),
933 field.span,
934 ObligationCauseCode::WellFormed(Some(WellFormedLoc::Ty(field.def_id))),
935 )
936 }
937
938 // Explicit `enum` discriminant values must const-evaluate successfully.
939 if let Some(discr_def_id) = variant.explicit_discr {
940 let discr_substs = InternalSubsts::identity_for_item(tcx, discr_def_id.to_def_id());
941
942 let cause = traits::ObligationCause::new(
943 tcx.def_span(discr_def_id),
944 fcx.body_id,
945 traits::MiscObligation,
946 );
947 fcx.register_predicate(traits::Obligation::new(
948 cause,
949 fcx.param_env,
950 ty::Binder::dummy(ty::PredicateKind::ConstEvaluatable(ty::Unevaluated::new(
951 ty::WithOptConstParam::unknown(discr_def_id.to_def_id()),
952 discr_substs,
953 )))
954 .to_predicate(tcx),
955 ));
956 }
957 }
958
959 check_where_clauses(fcx, item.span, item.def_id.to_def_id(), None);
960
961 // No implied bounds in a struct definition.
962 FxHashSet::default()
963 });
964 }
965
966 #[instrument(skip(tcx, item))]
check_trait(tcx: TyCtxt<'_>, item: &hir::Item<'_>)967 fn check_trait(tcx: TyCtxt<'_>, item: &hir::Item<'_>) {
968 debug!(?item.def_id);
969
970 let trait_def = tcx.trait_def(item.def_id);
971 if trait_def.is_marker
972 || matches!(trait_def.specialization_kind, TraitSpecializationKind::Marker)
973 {
974 for associated_def_id in &*tcx.associated_item_def_ids(item.def_id) {
975 struct_span_err!(
976 tcx.sess,
977 tcx.def_span(*associated_def_id),
978 E0714,
979 "marker traits cannot have associated items",
980 )
981 .emit();
982 }
983 }
984
985 // FIXME: this shouldn't use an `FnCtxt` at all.
986 for_item(tcx, item).with_fcx(|fcx| {
987 check_where_clauses(fcx, item.span, item.def_id.to_def_id(), None);
988
989 FxHashSet::default()
990 });
991 }
992
993 /// Checks all associated type defaults of trait `trait_def_id`.
994 ///
995 /// Assuming the defaults are used, check that all predicates (bounds on the
996 /// assoc type and where clauses on the trait) hold.
check_associated_type_bounds(fcx: &FnCtxt<'_, '_>, item: &ty::AssocItem, span: Span)997 fn check_associated_type_bounds(fcx: &FnCtxt<'_, '_>, item: &ty::AssocItem, span: Span) {
998 let tcx = fcx.tcx;
999
1000 let bounds = tcx.explicit_item_bounds(item.def_id);
1001
1002 debug!("check_associated_type_bounds: bounds={:?}", bounds);
1003 let wf_obligations = bounds.iter().flat_map(|&(bound, bound_span)| {
1004 let normalized_bound = fcx.normalize_associated_types_in(span, bound);
1005 traits::wf::predicate_obligations(
1006 fcx,
1007 fcx.param_env,
1008 fcx.body_id,
1009 normalized_bound,
1010 bound_span,
1011 )
1012 });
1013
1014 for obligation in wf_obligations {
1015 debug!("next obligation cause: {:?}", obligation.cause);
1016 fcx.register_predicate(obligation);
1017 }
1018 }
1019
check_item_fn( tcx: TyCtxt<'_>, def_id: LocalDefId, ident: Ident, span: Span, decl: &hir::FnDecl<'_>, )1020 fn check_item_fn(
1021 tcx: TyCtxt<'_>,
1022 def_id: LocalDefId,
1023 ident: Ident,
1024 span: Span,
1025 decl: &hir::FnDecl<'_>,
1026 ) {
1027 for_id(tcx, def_id, span).with_fcx(|fcx| {
1028 let sig = tcx.fn_sig(def_id);
1029 let mut implied_bounds = FxHashSet::default();
1030 check_fn_or_method(fcx, ident.span, sig, decl, def_id.to_def_id(), &mut implied_bounds);
1031 implied_bounds
1032 })
1033 }
1034
check_item_type(tcx: TyCtxt<'_>, item_id: LocalDefId, ty_span: Span, allow_foreign_ty: bool)1035 fn check_item_type(tcx: TyCtxt<'_>, item_id: LocalDefId, ty_span: Span, allow_foreign_ty: bool) {
1036 debug!("check_item_type: {:?}", item_id);
1037
1038 for_id(tcx, item_id, ty_span).with_fcx(|fcx| {
1039 let ty = tcx.type_of(item_id);
1040 let item_ty = fcx.normalize_associated_types_in_wf(ty_span, ty, WellFormedLoc::Ty(item_id));
1041
1042 let mut forbid_unsized = true;
1043 if allow_foreign_ty {
1044 let tail = fcx.tcx.struct_tail_erasing_lifetimes(item_ty, fcx.param_env);
1045 if let ty::Foreign(_) = tail.kind() {
1046 forbid_unsized = false;
1047 }
1048 }
1049
1050 fcx.register_wf_obligation(
1051 item_ty.into(),
1052 ty_span,
1053 ObligationCauseCode::WellFormed(Some(WellFormedLoc::Ty(item_id))),
1054 );
1055 if forbid_unsized {
1056 fcx.register_bound(
1057 item_ty,
1058 tcx.require_lang_item(LangItem::Sized, None),
1059 traits::ObligationCause::new(ty_span, fcx.body_id, traits::MiscObligation),
1060 );
1061 }
1062
1063 // No implied bounds in a const, etc.
1064 FxHashSet::default()
1065 });
1066 }
1067
1068 #[tracing::instrument(level = "debug", skip(tcx, ast_self_ty, ast_trait_ref))]
check_impl<'tcx>( tcx: TyCtxt<'tcx>, item: &'tcx hir::Item<'tcx>, ast_self_ty: &hir::Ty<'_>, ast_trait_ref: &Option<hir::TraitRef<'_>>, )1069 fn check_impl<'tcx>(
1070 tcx: TyCtxt<'tcx>,
1071 item: &'tcx hir::Item<'tcx>,
1072 ast_self_ty: &hir::Ty<'_>,
1073 ast_trait_ref: &Option<hir::TraitRef<'_>>,
1074 ) {
1075 for_item(tcx, item).with_fcx(|fcx| {
1076 match *ast_trait_ref {
1077 Some(ref ast_trait_ref) => {
1078 // `#[rustc_reservation_impl]` impls are not real impls and
1079 // therefore don't need to be WF (the trait's `Self: Trait` predicate
1080 // won't hold).
1081 let trait_ref = tcx.impl_trait_ref(item.def_id).unwrap();
1082 let trait_ref =
1083 fcx.normalize_associated_types_in(ast_trait_ref.path.span, trait_ref);
1084 let obligations = traits::wf::trait_obligations(
1085 fcx,
1086 fcx.param_env,
1087 fcx.body_id,
1088 &trait_ref,
1089 ast_trait_ref.path.span,
1090 Some(item),
1091 );
1092 debug!(?obligations);
1093 for obligation in obligations {
1094 fcx.register_predicate(obligation);
1095 }
1096 }
1097 None => {
1098 let self_ty = tcx.type_of(item.def_id);
1099 let self_ty = fcx.normalize_associated_types_in(item.span, self_ty);
1100 fcx.register_wf_obligation(
1101 self_ty.into(),
1102 ast_self_ty.span,
1103 ObligationCauseCode::WellFormed(Some(WellFormedLoc::Ty(
1104 item.hir_id().expect_owner(),
1105 ))),
1106 );
1107 }
1108 }
1109
1110 check_where_clauses(fcx, item.span, item.def_id.to_def_id(), None);
1111
1112 fcx.impl_implied_bounds(item.def_id.to_def_id(), item.span)
1113 });
1114 }
1115
1116 /// Checks where-clauses and inline bounds that are declared on `def_id`.
1117 #[instrument(skip(fcx), level = "debug")]
check_where_clauses<'tcx, 'fcx>( fcx: &FnCtxt<'fcx, 'tcx>, span: Span, def_id: DefId, return_ty: Option<(Ty<'tcx>, Span)>, )1118 fn check_where_clauses<'tcx, 'fcx>(
1119 fcx: &FnCtxt<'fcx, 'tcx>,
1120 span: Span,
1121 def_id: DefId,
1122 return_ty: Option<(Ty<'tcx>, Span)>,
1123 ) {
1124 let tcx = fcx.tcx;
1125
1126 let predicates = tcx.predicates_of(def_id);
1127 let generics = tcx.generics_of(def_id);
1128
1129 let is_our_default = |def: &ty::GenericParamDef| match def.kind {
1130 GenericParamDefKind::Type { has_default, .. }
1131 | GenericParamDefKind::Const { has_default } => {
1132 has_default && def.index >= generics.parent_count as u32
1133 }
1134 GenericParamDefKind::Lifetime => unreachable!(),
1135 };
1136
1137 // Check that concrete defaults are well-formed. See test `type-check-defaults.rs`.
1138 // For example, this forbids the declaration:
1139 //
1140 // struct Foo<T = Vec<[u32]>> { .. }
1141 //
1142 // Here, the default `Vec<[u32]>` is not WF because `[u32]: Sized` does not hold.
1143 for param in &generics.params {
1144 match param.kind {
1145 GenericParamDefKind::Type { .. } => {
1146 if is_our_default(param) {
1147 let ty = tcx.type_of(param.def_id);
1148 // Ignore dependent defaults -- that is, where the default of one type
1149 // parameter includes another (e.g., `<T, U = T>`). In those cases, we can't
1150 // be sure if it will error or not as user might always specify the other.
1151 if !ty.definitely_needs_subst(tcx) {
1152 fcx.register_wf_obligation(
1153 ty.into(),
1154 tcx.def_span(param.def_id),
1155 ObligationCauseCode::MiscObligation,
1156 );
1157 }
1158 }
1159 }
1160 GenericParamDefKind::Const { .. } => {
1161 if is_our_default(param) {
1162 // FIXME(const_generics_defaults): This
1163 // is incorrect when dealing with unused substs, for example
1164 // for `struct Foo<const N: usize, const M: usize = { 1 - 2 }>`
1165 // we should eagerly error.
1166 let default_ct = tcx.const_param_default(param.def_id);
1167 if !default_ct.definitely_needs_subst(tcx) {
1168 fcx.register_wf_obligation(
1169 default_ct.into(),
1170 tcx.def_span(param.def_id),
1171 ObligationCauseCode::WellFormed(None),
1172 );
1173 }
1174 }
1175 }
1176 // Doesn't have defaults.
1177 GenericParamDefKind::Lifetime => {}
1178 }
1179 }
1180
1181 // Check that trait predicates are WF when params are substituted by their defaults.
1182 // We don't want to overly constrain the predicates that may be written but we want to
1183 // catch cases where a default my never be applied such as `struct Foo<T: Copy = String>`.
1184 // Therefore we check if a predicate which contains a single type param
1185 // with a concrete default is WF with that default substituted.
1186 // For more examples see tests `defaults-well-formedness.rs` and `type-check-defaults.rs`.
1187 //
1188 // First we build the defaulted substitution.
1189 let substs = InternalSubsts::for_item(tcx, def_id, |param, _| {
1190 match param.kind {
1191 GenericParamDefKind::Lifetime => {
1192 // All regions are identity.
1193 tcx.mk_param_from_def(param)
1194 }
1195
1196 GenericParamDefKind::Type { .. } => {
1197 // If the param has a default, ...
1198 if is_our_default(param) {
1199 let default_ty = tcx.type_of(param.def_id);
1200 // ... and it's not a dependent default, ...
1201 if !default_ty.definitely_needs_subst(tcx) {
1202 // ... then substitute it with the default.
1203 return default_ty.into();
1204 }
1205 }
1206
1207 tcx.mk_param_from_def(param)
1208 }
1209 GenericParamDefKind::Const { .. } => {
1210 // If the param has a default, ...
1211 if is_our_default(param) {
1212 let default_ct = tcx.const_param_default(param.def_id);
1213 // ... and it's not a dependent default, ...
1214 if !default_ct.definitely_needs_subst(tcx) {
1215 // ... then substitute it with the default.
1216 return default_ct.into();
1217 }
1218 }
1219
1220 tcx.mk_param_from_def(param)
1221 }
1222 }
1223 });
1224
1225 // Now we build the substituted predicates.
1226 let default_obligations = predicates
1227 .predicates
1228 .iter()
1229 .flat_map(|&(pred, sp)| {
1230 struct CountParams<'tcx> {
1231 tcx: TyCtxt<'tcx>,
1232 params: FxHashSet<u32>,
1233 }
1234 impl<'tcx> ty::fold::TypeVisitor<'tcx> for CountParams<'tcx> {
1235 type BreakTy = ();
1236 fn tcx_for_anon_const_substs(&self) -> Option<TyCtxt<'tcx>> {
1237 Some(self.tcx)
1238 }
1239
1240 fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
1241 if let ty::Param(param) = t.kind() {
1242 self.params.insert(param.index);
1243 }
1244 t.super_visit_with(self)
1245 }
1246
1247 fn visit_region(&mut self, _: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> {
1248 ControlFlow::BREAK
1249 }
1250
1251 fn visit_const(&mut self, c: &'tcx ty::Const<'tcx>) -> ControlFlow<Self::BreakTy> {
1252 if let ty::ConstKind::Param(param) = c.val {
1253 self.params.insert(param.index);
1254 }
1255 c.super_visit_with(self)
1256 }
1257 }
1258 let mut param_count = CountParams { tcx: fcx.tcx, params: FxHashSet::default() };
1259 let has_region = pred.visit_with(&mut param_count).is_break();
1260 let substituted_pred = pred.subst(tcx, substs);
1261 // Don't check non-defaulted params, dependent defaults (including lifetimes)
1262 // or preds with multiple params.
1263 if substituted_pred.definitely_has_param_types_or_consts(tcx)
1264 || param_count.params.len() > 1
1265 || has_region
1266 {
1267 None
1268 } else if predicates.predicates.iter().any(|&(p, _)| p == substituted_pred) {
1269 // Avoid duplication of predicates that contain no parameters, for example.
1270 None
1271 } else {
1272 Some((substituted_pred, sp))
1273 }
1274 })
1275 .map(|(pred, sp)| {
1276 // Convert each of those into an obligation. So if you have
1277 // something like `struct Foo<T: Copy = String>`, we would
1278 // take that predicate `T: Copy`, substitute to `String: Copy`
1279 // (actually that happens in the previous `flat_map` call),
1280 // and then try to prove it (in this case, we'll fail).
1281 //
1282 // Note the subtle difference from how we handle `predicates`
1283 // below: there, we are not trying to prove those predicates
1284 // to be *true* but merely *well-formed*.
1285 let pred = fcx.normalize_associated_types_in(sp, pred);
1286 let cause =
1287 traits::ObligationCause::new(sp, fcx.body_id, traits::ItemObligation(def_id));
1288 traits::Obligation::new(cause, fcx.param_env, pred)
1289 });
1290
1291 let predicates = predicates.instantiate_identity(tcx);
1292
1293 if let Some((return_ty, _)) = return_ty {
1294 if return_ty.has_infer_types_or_consts() {
1295 fcx.select_obligations_where_possible(false, |_| {});
1296 }
1297 }
1298
1299 let predicates = fcx.normalize_associated_types_in(span, predicates);
1300
1301 debug!(?predicates.predicates);
1302 assert_eq!(predicates.predicates.len(), predicates.spans.len());
1303 let wf_obligations =
1304 iter::zip(&predicates.predicates, &predicates.spans).flat_map(|(&p, &sp)| {
1305 traits::wf::predicate_obligations(fcx, fcx.param_env, fcx.body_id, p, sp)
1306 });
1307
1308 for obligation in wf_obligations.chain(default_obligations) {
1309 debug!("next obligation cause: {:?}", obligation.cause);
1310 fcx.register_predicate(obligation);
1311 }
1312 }
1313
1314 #[tracing::instrument(level = "debug", skip(fcx, span, hir_decl))]
check_fn_or_method<'fcx, 'tcx>( fcx: &FnCtxt<'fcx, 'tcx>, span: Span, sig: ty::PolyFnSig<'tcx>, hir_decl: &hir::FnDecl<'_>, def_id: DefId, implied_bounds: &mut FxHashSet<Ty<'tcx>>, )1315 fn check_fn_or_method<'fcx, 'tcx>(
1316 fcx: &FnCtxt<'fcx, 'tcx>,
1317 span: Span,
1318 sig: ty::PolyFnSig<'tcx>,
1319 hir_decl: &hir::FnDecl<'_>,
1320 def_id: DefId,
1321 implied_bounds: &mut FxHashSet<Ty<'tcx>>,
1322 ) {
1323 let sig = fcx.tcx.liberate_late_bound_regions(def_id, sig);
1324
1325 // Normalize the input and output types one at a time, using a different
1326 // `WellFormedLoc` for each. We cannot call `normalize_associated_types`
1327 // on the entire `FnSig`, since this would use the same `WellFormedLoc`
1328 // for each type, preventing the HIR wf check from generating
1329 // a nice error message.
1330 let ty::FnSig { mut inputs_and_output, c_variadic, unsafety, abi } = sig;
1331 inputs_and_output =
1332 fcx.tcx.mk_type_list(inputs_and_output.iter().enumerate().map(|(i, ty)| {
1333 fcx.normalize_associated_types_in_wf(
1334 span,
1335 ty,
1336 WellFormedLoc::Param {
1337 function: def_id.expect_local(),
1338 // Note that the `param_idx` of the output type is
1339 // one greater than the index of the last input type.
1340 param_idx: i.try_into().unwrap(),
1341 },
1342 )
1343 }));
1344 // Manually call `normalize_assocaited_types_in` on the other types
1345 // in `FnSig`. This ensures that if the types of these fields
1346 // ever change to include projections, we will start normalizing
1347 // them automatically.
1348 let sig = ty::FnSig {
1349 inputs_and_output,
1350 c_variadic: fcx.normalize_associated_types_in(span, c_variadic),
1351 unsafety: fcx.normalize_associated_types_in(span, unsafety),
1352 abi: fcx.normalize_associated_types_in(span, abi),
1353 };
1354
1355 for (i, (&input_ty, ty)) in iter::zip(sig.inputs(), hir_decl.inputs).enumerate() {
1356 fcx.register_wf_obligation(
1357 input_ty.into(),
1358 ty.span,
1359 ObligationCauseCode::WellFormed(Some(WellFormedLoc::Param {
1360 function: def_id.expect_local(),
1361 param_idx: i.try_into().unwrap(),
1362 })),
1363 );
1364 }
1365
1366 implied_bounds.extend(sig.inputs());
1367
1368 fcx.register_wf_obligation(
1369 sig.output().into(),
1370 hir_decl.output.span(),
1371 ObligationCauseCode::ReturnType,
1372 );
1373
1374 // FIXME(#27579) return types should not be implied bounds
1375 implied_bounds.insert(sig.output());
1376
1377 debug!(?implied_bounds);
1378
1379 check_where_clauses(fcx, span, def_id, Some((sig.output(), hir_decl.output.span())));
1380 }
1381
1382 const HELP_FOR_SELF_TYPE: &str = "consider changing to `self`, `&self`, `&mut self`, `self: Box<Self>`, \
1383 `self: Rc<Self>`, `self: Arc<Self>`, or `self: Pin<P>` (where P is one \
1384 of the previous types except `Self`)";
1385
1386 #[tracing::instrument(level = "debug", skip(fcx))]
check_method_receiver<'fcx, 'tcx>( fcx: &FnCtxt<'fcx, 'tcx>, fn_sig: &hir::FnSig<'_>, method: &ty::AssocItem, self_ty: Ty<'tcx>, )1387 fn check_method_receiver<'fcx, 'tcx>(
1388 fcx: &FnCtxt<'fcx, 'tcx>,
1389 fn_sig: &hir::FnSig<'_>,
1390 method: &ty::AssocItem,
1391 self_ty: Ty<'tcx>,
1392 ) {
1393 // Check that the method has a valid receiver type, given the type `Self`.
1394 debug!("check_method_receiver({:?}, self_ty={:?})", method, self_ty);
1395
1396 if !method.fn_has_self_parameter {
1397 return;
1398 }
1399
1400 let span = fn_sig.decl.inputs[0].span;
1401
1402 let sig = fcx.tcx.fn_sig(method.def_id);
1403 let sig = fcx.tcx.liberate_late_bound_regions(method.def_id, sig);
1404 let sig = fcx.normalize_associated_types_in(span, sig);
1405
1406 debug!("check_method_receiver: sig={:?}", sig);
1407
1408 let self_ty = fcx.normalize_associated_types_in(span, self_ty);
1409
1410 let receiver_ty = sig.inputs()[0];
1411 let receiver_ty = fcx.normalize_associated_types_in(span, receiver_ty);
1412
1413 if fcx.tcx.features().arbitrary_self_types {
1414 if !receiver_is_valid(fcx, span, receiver_ty, self_ty, true) {
1415 // Report error; `arbitrary_self_types` was enabled.
1416 e0307(fcx, span, receiver_ty);
1417 }
1418 } else {
1419 if !receiver_is_valid(fcx, span, receiver_ty, self_ty, false) {
1420 if receiver_is_valid(fcx, span, receiver_ty, self_ty, true) {
1421 // Report error; would have worked with `arbitrary_self_types`.
1422 feature_err(
1423 &fcx.tcx.sess.parse_sess,
1424 sym::arbitrary_self_types,
1425 span,
1426 &format!(
1427 "`{}` cannot be used as the type of `self` without \
1428 the `arbitrary_self_types` feature",
1429 receiver_ty,
1430 ),
1431 )
1432 .help(HELP_FOR_SELF_TYPE)
1433 .emit();
1434 } else {
1435 // Report error; would not have worked with `arbitrary_self_types`.
1436 e0307(fcx, span, receiver_ty);
1437 }
1438 }
1439 }
1440 }
1441
e0307(fcx: &FnCtxt<'fcx, 'tcx>, span: Span, receiver_ty: Ty<'_>)1442 fn e0307(fcx: &FnCtxt<'fcx, 'tcx>, span: Span, receiver_ty: Ty<'_>) {
1443 struct_span_err!(
1444 fcx.tcx.sess.diagnostic(),
1445 span,
1446 E0307,
1447 "invalid `self` parameter type: {}",
1448 receiver_ty,
1449 )
1450 .note("type of `self` must be `Self` or a type that dereferences to it")
1451 .help(HELP_FOR_SELF_TYPE)
1452 .emit();
1453 }
1454
1455 /// Returns whether `receiver_ty` would be considered a valid receiver type for `self_ty`. If
1456 /// `arbitrary_self_types` is enabled, `receiver_ty` must transitively deref to `self_ty`, possibly
1457 /// through a `*const/mut T` raw pointer. If the feature is not enabled, the requirements are more
1458 /// strict: `receiver_ty` must implement `Receiver` and directly implement
1459 /// `Deref<Target = self_ty>`.
1460 ///
1461 /// N.B., there are cases this function returns `true` but causes an error to be emitted,
1462 /// particularly when `receiver_ty` derefs to a type that is the same as `self_ty` but has the
1463 /// wrong lifetime. Be careful of this if you are calling this function speculatively.
receiver_is_valid<'fcx, 'tcx>( fcx: &FnCtxt<'fcx, 'tcx>, span: Span, receiver_ty: Ty<'tcx>, self_ty: Ty<'tcx>, arbitrary_self_types_enabled: bool, ) -> bool1464 fn receiver_is_valid<'fcx, 'tcx>(
1465 fcx: &FnCtxt<'fcx, 'tcx>,
1466 span: Span,
1467 receiver_ty: Ty<'tcx>,
1468 self_ty: Ty<'tcx>,
1469 arbitrary_self_types_enabled: bool,
1470 ) -> bool {
1471 let cause = fcx.cause(span, traits::ObligationCauseCode::MethodReceiver);
1472
1473 let can_eq_self = |ty| fcx.infcx.can_eq(fcx.param_env, self_ty, ty).is_ok();
1474
1475 // `self: Self` is always valid.
1476 if can_eq_self(receiver_ty) {
1477 if let Some(mut err) = fcx.demand_eqtype_with_origin(&cause, self_ty, receiver_ty) {
1478 err.emit();
1479 }
1480 return true;
1481 }
1482
1483 let mut autoderef = fcx.autoderef(span, receiver_ty);
1484
1485 // The `arbitrary_self_types` feature allows raw pointer receivers like `self: *const Self`.
1486 if arbitrary_self_types_enabled {
1487 autoderef = autoderef.include_raw_pointers();
1488 }
1489
1490 // The first type is `receiver_ty`, which we know its not equal to `self_ty`; skip it.
1491 autoderef.next();
1492
1493 let receiver_trait_def_id = fcx.tcx.require_lang_item(LangItem::Receiver, None);
1494
1495 // Keep dereferencing `receiver_ty` until we get to `self_ty`.
1496 loop {
1497 if let Some((potential_self_ty, _)) = autoderef.next() {
1498 debug!(
1499 "receiver_is_valid: potential self type `{:?}` to match `{:?}`",
1500 potential_self_ty, self_ty
1501 );
1502
1503 if can_eq_self(potential_self_ty) {
1504 fcx.register_predicates(autoderef.into_obligations());
1505
1506 if let Some(mut err) =
1507 fcx.demand_eqtype_with_origin(&cause, self_ty, potential_self_ty)
1508 {
1509 err.emit();
1510 }
1511
1512 break;
1513 } else {
1514 // Without `feature(arbitrary_self_types)`, we require that each step in the
1515 // deref chain implement `receiver`
1516 if !arbitrary_self_types_enabled
1517 && !receiver_is_implemented(
1518 fcx,
1519 receiver_trait_def_id,
1520 cause.clone(),
1521 potential_self_ty,
1522 )
1523 {
1524 return false;
1525 }
1526 }
1527 } else {
1528 debug!("receiver_is_valid: type `{:?}` does not deref to `{:?}`", receiver_ty, self_ty);
1529 // If he receiver already has errors reported due to it, consider it valid to avoid
1530 // unnecessary errors (#58712).
1531 return receiver_ty.references_error();
1532 }
1533 }
1534
1535 // Without `feature(arbitrary_self_types)`, we require that `receiver_ty` implements `Receiver`.
1536 if !arbitrary_self_types_enabled
1537 && !receiver_is_implemented(fcx, receiver_trait_def_id, cause.clone(), receiver_ty)
1538 {
1539 return false;
1540 }
1541
1542 true
1543 }
1544
receiver_is_implemented( fcx: &FnCtxt<'_, 'tcx>, receiver_trait_def_id: DefId, cause: ObligationCause<'tcx>, receiver_ty: Ty<'tcx>, ) -> bool1545 fn receiver_is_implemented(
1546 fcx: &FnCtxt<'_, 'tcx>,
1547 receiver_trait_def_id: DefId,
1548 cause: ObligationCause<'tcx>,
1549 receiver_ty: Ty<'tcx>,
1550 ) -> bool {
1551 let trait_ref = ty::Binder::dummy(ty::TraitRef {
1552 def_id: receiver_trait_def_id,
1553 substs: fcx.tcx.mk_substs_trait(receiver_ty, &[]),
1554 });
1555
1556 let obligation = traits::Obligation::new(
1557 cause,
1558 fcx.param_env,
1559 trait_ref.without_const().to_predicate(fcx.tcx),
1560 );
1561
1562 if fcx.predicate_must_hold_modulo_regions(&obligation) {
1563 true
1564 } else {
1565 debug!(
1566 "receiver_is_implemented: type `{:?}` does not implement `Receiver` trait",
1567 receiver_ty
1568 );
1569 false
1570 }
1571 }
1572
check_variances_for_type_defn<'tcx>( tcx: TyCtxt<'tcx>, item: &hir::Item<'tcx>, hir_generics: &hir::Generics<'_>, )1573 fn check_variances_for_type_defn<'tcx>(
1574 tcx: TyCtxt<'tcx>,
1575 item: &hir::Item<'tcx>,
1576 hir_generics: &hir::Generics<'_>,
1577 ) {
1578 let ty = tcx.type_of(item.def_id);
1579 if tcx.has_error_field(ty) {
1580 return;
1581 }
1582
1583 let ty_predicates = tcx.predicates_of(item.def_id);
1584 assert_eq!(ty_predicates.parent, None);
1585 let variances = tcx.variances_of(item.def_id);
1586
1587 let mut constrained_parameters: FxHashSet<_> = variances
1588 .iter()
1589 .enumerate()
1590 .filter(|&(_, &variance)| variance != ty::Bivariant)
1591 .map(|(index, _)| Parameter(index as u32))
1592 .collect();
1593
1594 identify_constrained_generic_params(tcx, ty_predicates, None, &mut constrained_parameters);
1595
1596 for (index, _) in variances.iter().enumerate() {
1597 if constrained_parameters.contains(&Parameter(index as u32)) {
1598 continue;
1599 }
1600
1601 let param = &hir_generics.params[index];
1602
1603 match param.name {
1604 hir::ParamName::Error => {}
1605 _ => report_bivariance(tcx, param),
1606 }
1607 }
1608 }
1609
report_bivariance(tcx: TyCtxt<'_>, param: &rustc_hir::GenericParam<'_>)1610 fn report_bivariance(tcx: TyCtxt<'_>, param: &rustc_hir::GenericParam<'_>) {
1611 let span = param.span;
1612 let param_name = param.name.ident().name;
1613 let mut err = error_392(tcx, span, param_name);
1614
1615 let suggested_marker_id = tcx.lang_items().phantom_data();
1616 // Help is available only in presence of lang items.
1617 let msg = if let Some(def_id) = suggested_marker_id {
1618 format!(
1619 "consider removing `{}`, referring to it in a field, or using a marker such as `{}`",
1620 param_name,
1621 tcx.def_path_str(def_id),
1622 )
1623 } else {
1624 format!("consider removing `{}` or referring to it in a field", param_name)
1625 };
1626 err.help(&msg);
1627
1628 if matches!(param.kind, rustc_hir::GenericParamKind::Type { .. }) {
1629 err.help(&format!(
1630 "if you intended `{0}` to be a const parameter, use `const {0}: usize` instead",
1631 param_name
1632 ));
1633 }
1634 err.emit()
1635 }
1636
1637 /// Feature gates RFC 2056 -- trivial bounds, checking for global bounds that
1638 /// aren't true.
check_false_global_bounds(fcx: &FnCtxt<'_, '_>, mut span: Span, id: hir::HirId)1639 fn check_false_global_bounds(fcx: &FnCtxt<'_, '_>, mut span: Span, id: hir::HirId) {
1640 let empty_env = ty::ParamEnv::empty();
1641
1642 let def_id = fcx.tcx.hir().local_def_id(id);
1643 let predicates_with_span =
1644 fcx.tcx.predicates_of(def_id).predicates.iter().map(|(p, span)| (*p, *span));
1645 // Check elaborated bounds.
1646 let implied_obligations = traits::elaborate_predicates_with_span(fcx.tcx, predicates_with_span);
1647
1648 for obligation in implied_obligations {
1649 let pred = obligation.predicate;
1650 // Match the existing behavior.
1651 if pred.is_global(fcx.tcx) && !pred.has_late_bound_regions() {
1652 let pred = fcx.normalize_associated_types_in(span, pred);
1653 let hir_node = fcx.tcx.hir().find(id);
1654
1655 // only use the span of the predicate clause (#90869)
1656
1657 if let Some(hir::Generics { where_clause, .. }) =
1658 hir_node.and_then(|node| node.generics())
1659 {
1660 let obligation_span = obligation.cause.span(fcx.tcx);
1661
1662 span = where_clause
1663 .predicates
1664 .iter()
1665 // There seems to be no better way to find out which predicate we are in
1666 .find(|pred| pred.span().contains(obligation_span))
1667 .map(|pred| pred.span())
1668 .unwrap_or(obligation_span);
1669 }
1670
1671 let obligation = traits::Obligation::new(
1672 traits::ObligationCause::new(span, id, traits::TrivialBound),
1673 empty_env,
1674 pred,
1675 );
1676 fcx.register_predicate(obligation);
1677 }
1678 }
1679
1680 fcx.select_all_obligations_or_error();
1681 }
1682
1683 #[derive(Clone, Copy)]
1684 pub struct CheckTypeWellFormedVisitor<'tcx> {
1685 tcx: TyCtxt<'tcx>,
1686 }
1687
1688 impl CheckTypeWellFormedVisitor<'tcx> {
new(tcx: TyCtxt<'tcx>) -> CheckTypeWellFormedVisitor<'tcx>1689 pub fn new(tcx: TyCtxt<'tcx>) -> CheckTypeWellFormedVisitor<'tcx> {
1690 CheckTypeWellFormedVisitor { tcx }
1691 }
1692 }
1693
1694 impl ParItemLikeVisitor<'tcx> for CheckTypeWellFormedVisitor<'tcx> {
visit_item(&self, i: &'tcx hir::Item<'tcx>)1695 fn visit_item(&self, i: &'tcx hir::Item<'tcx>) {
1696 Visitor::visit_item(&mut self.clone(), i);
1697 }
1698
visit_trait_item(&self, trait_item: &'tcx hir::TraitItem<'tcx>)1699 fn visit_trait_item(&self, trait_item: &'tcx hir::TraitItem<'tcx>) {
1700 Visitor::visit_trait_item(&mut self.clone(), trait_item);
1701 }
1702
visit_impl_item(&self, impl_item: &'tcx hir::ImplItem<'tcx>)1703 fn visit_impl_item(&self, impl_item: &'tcx hir::ImplItem<'tcx>) {
1704 Visitor::visit_impl_item(&mut self.clone(), impl_item);
1705 }
1706
visit_foreign_item(&self, foreign_item: &'tcx hir::ForeignItem<'tcx>)1707 fn visit_foreign_item(&self, foreign_item: &'tcx hir::ForeignItem<'tcx>) {
1708 Visitor::visit_foreign_item(&mut self.clone(), foreign_item)
1709 }
1710 }
1711
1712 impl Visitor<'tcx> for CheckTypeWellFormedVisitor<'tcx> {
1713 type Map = hir_map::Map<'tcx>;
1714
nested_visit_map(&mut self) -> hir_visit::NestedVisitorMap<Self::Map>1715 fn nested_visit_map(&mut self) -> hir_visit::NestedVisitorMap<Self::Map> {
1716 hir_visit::NestedVisitorMap::OnlyBodies(self.tcx.hir())
1717 }
1718
1719 #[instrument(skip(self, i), level = "debug")]
visit_item(&mut self, i: &'tcx hir::Item<'tcx>)1720 fn visit_item(&mut self, i: &'tcx hir::Item<'tcx>) {
1721 trace!(?i);
1722 self.tcx.ensure().check_item_well_formed(i.def_id);
1723 hir_visit::walk_item(self, i);
1724 }
1725
1726 #[instrument(skip(self, trait_item), level = "debug")]
visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>)1727 fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
1728 trace!(?trait_item);
1729 self.tcx.ensure().check_trait_item_well_formed(trait_item.def_id);
1730 hir_visit::walk_trait_item(self, trait_item);
1731 }
1732
1733 #[instrument(skip(self, impl_item), level = "debug")]
visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>)1734 fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
1735 trace!(?impl_item);
1736 self.tcx.ensure().check_impl_item_well_formed(impl_item.def_id);
1737 hir_visit::walk_impl_item(self, impl_item);
1738 }
1739
visit_generic_param(&mut self, p: &'tcx hir::GenericParam<'tcx>)1740 fn visit_generic_param(&mut self, p: &'tcx hir::GenericParam<'tcx>) {
1741 check_param_wf(self.tcx, p);
1742 hir_visit::walk_generic_param(self, p);
1743 }
1744 }
1745
1746 ///////////////////////////////////////////////////////////////////////////
1747 // ADT
1748
1749 // FIXME(eddyb) replace this with getting fields/discriminants through `ty::AdtDef`.
1750 struct AdtVariant<'tcx> {
1751 /// Types of fields in the variant, that must be well-formed.
1752 fields: Vec<AdtField<'tcx>>,
1753
1754 /// Explicit discriminant of this variant (e.g. `A = 123`),
1755 /// that must evaluate to a constant value.
1756 explicit_discr: Option<LocalDefId>,
1757 }
1758
1759 struct AdtField<'tcx> {
1760 ty: Ty<'tcx>,
1761 def_id: LocalDefId,
1762 span: Span,
1763 }
1764
1765 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
1766 // FIXME(eddyb) replace this with getting fields through `ty::AdtDef`.
non_enum_variant(&self, struct_def: &hir::VariantData<'_>) -> AdtVariant<'tcx>1767 fn non_enum_variant(&self, struct_def: &hir::VariantData<'_>) -> AdtVariant<'tcx> {
1768 let fields = struct_def
1769 .fields()
1770 .iter()
1771 .map(|field| {
1772 let def_id = self.tcx.hir().local_def_id(field.hir_id);
1773 let field_ty = self.tcx.type_of(def_id);
1774 let field_ty = self.normalize_associated_types_in(field.ty.span, field_ty);
1775 let field_ty = self.resolve_vars_if_possible(field_ty);
1776 debug!("non_enum_variant: type of field {:?} is {:?}", field, field_ty);
1777 AdtField { ty: field_ty, span: field.ty.span, def_id }
1778 })
1779 .collect();
1780 AdtVariant { fields, explicit_discr: None }
1781 }
1782
enum_variants(&self, enum_def: &hir::EnumDef<'_>) -> Vec<AdtVariant<'tcx>>1783 fn enum_variants(&self, enum_def: &hir::EnumDef<'_>) -> Vec<AdtVariant<'tcx>> {
1784 enum_def
1785 .variants
1786 .iter()
1787 .map(|variant| AdtVariant {
1788 fields: self.non_enum_variant(&variant.data).fields,
1789 explicit_discr: variant
1790 .disr_expr
1791 .map(|explicit_discr| self.tcx.hir().local_def_id(explicit_discr.hir_id)),
1792 })
1793 .collect()
1794 }
1795
impl_implied_bounds( &self, impl_def_id: DefId, span: Span, ) -> FxHashSet<Ty<'tcx>>1796 pub(super) fn impl_implied_bounds(
1797 &self,
1798 impl_def_id: DefId,
1799 span: Span,
1800 ) -> FxHashSet<Ty<'tcx>> {
1801 match self.tcx.impl_trait_ref(impl_def_id) {
1802 Some(trait_ref) => {
1803 // Trait impl: take implied bounds from all types that
1804 // appear in the trait reference.
1805 let trait_ref = self.normalize_associated_types_in(span, trait_ref);
1806 trait_ref.substs.types().collect()
1807 }
1808
1809 None => {
1810 // Inherent impl: take implied bounds from the `self` type.
1811 let self_ty = self.tcx.type_of(impl_def_id);
1812 let self_ty = self.normalize_associated_types_in(span, self_ty);
1813 std::array::IntoIter::new([self_ty]).collect()
1814 }
1815 }
1816 }
1817 }
1818
error_392(tcx: TyCtxt<'_>, span: Span, param_name: Symbol) -> DiagnosticBuilder<'_>1819 fn error_392(tcx: TyCtxt<'_>, span: Span, param_name: Symbol) -> DiagnosticBuilder<'_> {
1820 let mut err =
1821 struct_span_err!(tcx.sess, span, E0392, "parameter `{}` is never used", param_name);
1822 err.span_label(span, "unused parameter");
1823 err
1824 }
1825