1 use super::coercion::CoerceMany;
2 use super::compare_method::check_type_bounds;
3 use super::compare_method::{compare_const_impl, compare_impl_method, compare_ty_impl};
6 use rustc_attr as attr;
7 use rustc_errors::{Applicability, ErrorReported};
9 use rustc_hir::def_id::{DefId, LocalDefId, LOCAL_CRATE};
10 use rustc_hir::lang_items::LangItem;
11 use rustc_hir::{ItemKind, Node};
12 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
13 use rustc_infer::infer::{RegionVariableOrigin, TyCtxtInferExt};
14 use rustc_middle::ty::fold::TypeFoldable;
15 use rustc_middle::ty::subst::GenericArgKind;
16 use rustc_middle::ty::util::{Discr, IntTypeExt, Representability};
17 use rustc_middle::ty::{self, ParamEnv, RegionKind, ToPredicate, Ty, TyCtxt};
18 use rustc_session::config::EntryFnType;
19 use rustc_session::lint::builtin::UNINHABITED_STATIC;
20 use rustc_span::symbol::sym;
21 use rustc_span::{self, MultiSpan, Span};
22 use rustc_target::spec::abi::Abi;
23 use rustc_trait_selection::opaque_types::InferCtxtExt as _;
24 use rustc_trait_selection::traits::error_reporting::InferCtxtExt as _;
25 use rustc_trait_selection::traits::{self, ObligationCauseCode};
27 use std::ops::ControlFlow;
29 pub fn check_wf_new(tcx: TyCtxt<'_>) {
30 let visit = wfcheck::CheckTypeWellFormedVisitor::new(tcx);
31 tcx.hir().krate().par_visit_all_item_likes(&visit);
34 pub(super) fn check_abi(tcx: TyCtxt<'_>, span: Span, abi: Abi) {
35 if !tcx.sess.target.is_abi_supported(abi) {
40 "The ABI `{}` is not supported for the current target",
47 /// Helper used for fns and closures. Does the grungy work of checking a function
48 /// body and returns the function context used for that purpose, since in the case of a fn item
49 /// there is still a bit more to do.
52 /// * inherited: other fields inherited from the enclosing fn (if any)
53 pub(super) fn check_fn<'a, 'tcx>(
54 inherited: &'a Inherited<'a, 'tcx>,
55 param_env: ty::ParamEnv<'tcx>,
56 fn_sig: ty::FnSig<'tcx>,
57 decl: &'tcx hir::FnDecl<'tcx>,
59 body: &'tcx hir::Body<'tcx>,
60 can_be_generator: Option<hir::Movability>,
61 ) -> (FnCtxt<'a, 'tcx>, Option<GeneratorTypes<'tcx>>) {
62 let mut fn_sig = fn_sig;
64 debug!("check_fn(sig={:?}, fn_id={}, param_env={:?})", fn_sig, fn_id, param_env);
66 // Create the function context. This is either derived from scratch or,
67 // in the case of closures, based on the outer context.
68 let mut fcx = FnCtxt::new(inherited, param_env, body.value.hir_id);
69 *fcx.ps.borrow_mut() = UnsafetyState::function(fn_sig.unsafety, fn_id);
75 let declared_ret_ty = fn_sig.output();
78 fcx.instantiate_opaque_types_from_value(fn_id, declared_ret_ty, decl.output.span());
79 debug!("check_fn: declared_ret_ty: {}, revealed_ret_ty: {}", declared_ret_ty, revealed_ret_ty);
80 fcx.ret_coercion = Some(RefCell::new(CoerceMany::new(revealed_ret_ty)));
81 fcx.ret_type_span = Some(decl.output.span());
82 if let ty::Opaque(..) = declared_ret_ty.kind() {
83 fcx.ret_coercion_impl_trait = Some(declared_ret_ty);
85 fn_sig = tcx.mk_fn_sig(
86 fn_sig.inputs().iter().cloned(),
93 let span = body.value.span;
95 fn_maybe_err(tcx, span, fn_sig.abi);
97 if fn_sig.abi == Abi::RustCall {
98 let expected_args = if let ImplicitSelfKind::None = decl.implicit_self { 1 } else { 2 };
101 let item = match tcx.hir().get(fn_id) {
102 Node::Item(hir::Item { kind: ItemKind::Fn(header, ..), .. }) => Some(header),
103 Node::ImplItem(hir::ImplItem {
104 kind: hir::ImplItemKind::Fn(header, ..), ..
106 // Closures are RustCall, but they tuple their arguments, so shouldn't be checked
107 Node::Expr(hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => None,
108 node => bug!("Item being checked wasn't a function/closure: {:?}", node),
111 if let Some(header) = item {
112 tcx.sess.span_err(header.span, "A function with the \"rust-call\" ABI must take a single non-self argument that is a tuple")
116 if fn_sig.inputs().len() != expected_args {
119 // FIXME(CraftSpider) Add a check on parameter expansion, so we don't just make the ICE happen later on
120 // This will probably require wide-scale changes to support a TupleKind obligation
121 // We can't resolve this without knowing the type of the param
122 if !matches!(fn_sig.inputs()[expected_args - 1].kind(), ty::Tuple(_) | ty::Param(_)) {
128 if body.generator_kind.is_some() && can_be_generator.is_some() {
130 .next_ty_var(TypeVariableOrigin { kind: TypeVariableOriginKind::TypeInference, span });
131 fcx.require_type_is_sized(yield_ty, span, traits::SizedYieldType);
133 // Resume type defaults to `()` if the generator has no argument.
134 let resume_ty = fn_sig.inputs().get(0).copied().unwrap_or_else(|| tcx.mk_unit());
136 fcx.resume_yield_tys = Some((resume_ty, yield_ty));
139 let outer_def_id = tcx.closure_base_def_id(hir.local_def_id(fn_id).to_def_id()).expect_local();
140 let outer_hir_id = hir.local_def_id_to_hir_id(outer_def_id);
141 GatherLocalsVisitor::new(&fcx, outer_hir_id).visit_body(body);
143 // C-variadic fns also have a `VaList` input that's not listed in `fn_sig`
144 // (as it's created inside the body itself, not passed in from outside).
145 let maybe_va_list = if fn_sig.c_variadic {
146 let span = body.params.last().unwrap().span;
147 let va_list_did = tcx.require_lang_item(LangItem::VaList, Some(span));
148 let region = fcx.next_region_var(RegionVariableOrigin::MiscVariable(span));
150 Some(tcx.type_of(va_list_did).subst(tcx, &[region.into()]))
155 // Add formal parameters.
156 let inputs_hir = hir.fn_decl_by_hir_id(fn_id).map(|decl| &decl.inputs);
157 let inputs_fn = fn_sig.inputs().iter().copied();
158 for (idx, (param_ty, param)) in inputs_fn.chain(maybe_va_list).zip(body.params).enumerate() {
159 // Check the pattern.
160 let ty_span = try { inputs_hir?.get(idx)?.span };
161 fcx.check_pat_top(¶m.pat, param_ty, ty_span, false);
163 // Check that argument is Sized.
164 // The check for a non-trivial pattern is a hack to avoid duplicate warnings
165 // for simple cases like `fn foo(x: Trait)`,
166 // where we would error once on the parameter as a whole, and once on the binding `x`.
167 if param.pat.simple_ident().is_none() && !tcx.features().unsized_fn_params {
168 fcx.require_type_is_sized(param_ty, param.pat.span, traits::SizedArgumentType(ty_span));
171 fcx.write_ty(param.hir_id, param_ty);
174 inherited.typeck_results.borrow_mut().liberated_fn_sigs_mut().insert(fn_id, fn_sig);
176 fcx.in_tail_expr = true;
177 if let ty::Dynamic(..) = declared_ret_ty.kind() {
178 // FIXME: We need to verify that the return type is `Sized` after the return expression has
179 // been evaluated so that we have types available for all the nodes being returned, but that
180 // requires the coerced evaluated type to be stored. Moving `check_return_expr` before this
181 // causes unsized errors caused by the `declared_ret_ty` to point at the return expression,
182 // while keeping the current ordering we will ignore the tail expression's type because we
183 // don't know it yet. We can't do `check_expr_kind` while keeping `check_return_expr`
184 // because we will trigger "unreachable expression" lints unconditionally.
185 // Because of all of this, we perform a crude check to know whether the simplest `!Sized`
186 // case that a newcomer might make, returning a bare trait, and in that case we populate
187 // the tail expression's type so that the suggestion will be correct, but ignore all other
189 fcx.check_expr(&body.value);
190 fcx.require_type_is_sized(declared_ret_ty, decl.output.span(), traits::SizedReturnType);
191 tcx.sess.delay_span_bug(decl.output.span(), "`!Sized` return type");
193 fcx.require_type_is_sized(declared_ret_ty, decl.output.span(), traits::SizedReturnType);
194 fcx.check_return_expr(&body.value);
196 fcx.in_tail_expr = false;
198 // We insert the deferred_generator_interiors entry after visiting the body.
199 // This ensures that all nested generators appear before the entry of this generator.
200 // resolve_generator_interiors relies on this property.
201 let gen_ty = if let (Some(_), Some(gen_kind)) = (can_be_generator, body.generator_kind) {
203 .next_ty_var(TypeVariableOrigin { kind: TypeVariableOriginKind::MiscVariable, span });
204 fcx.deferred_generator_interiors.borrow_mut().push((body.id(), interior, gen_kind));
206 let (resume_ty, yield_ty) = fcx.resume_yield_tys.unwrap();
207 Some(GeneratorTypes {
211 movability: can_be_generator.unwrap(),
217 // Finalize the return check by taking the LUB of the return types
218 // we saw and assigning it to the expected return type. This isn't
219 // really expected to fail, since the coercions would have failed
220 // earlier when trying to find a LUB.
222 // However, the behavior around `!` is sort of complex. In the
223 // event that the `actual_return_ty` comes back as `!`, that
224 // indicates that the fn either does not return or "returns" only
225 // values of type `!`. In this case, if there is an expected
226 // return type that is *not* `!`, that should be ok. But if the
227 // return type is being inferred, we want to "fallback" to `!`:
229 // let x = move || panic!();
231 // To allow for that, I am creating a type variable with diverging
232 // fallback. This was deemed ever so slightly better than unifying
233 // the return value with `!` because it allows for the caller to
234 // make more assumptions about the return type (e.g., they could do
236 // let y: Option<u32> = Some(x());
238 // which would then cause this return type to become `u32`, not
240 let coercion = fcx.ret_coercion.take().unwrap().into_inner();
241 let mut actual_return_ty = coercion.complete(&fcx);
242 if actual_return_ty.is_never() {
243 actual_return_ty = fcx.next_diverging_ty_var(TypeVariableOrigin {
244 kind: TypeVariableOriginKind::DivergingFn,
248 fcx.demand_suptype(span, revealed_ret_ty, actual_return_ty);
250 // Check that the main return type implements the termination trait.
251 if let Some(term_id) = tcx.lang_items().termination() {
252 if let Some((def_id, EntryFnType::Main)) = tcx.entry_fn(LOCAL_CRATE) {
253 let main_id = hir.local_def_id_to_hir_id(def_id);
254 if main_id == fn_id {
255 let substs = tcx.mk_substs_trait(declared_ret_ty, &[]);
256 let trait_ref = ty::TraitRef::new(term_id, substs);
257 let return_ty_span = decl.output.span();
258 let cause = traits::ObligationCause::new(
261 ObligationCauseCode::MainFunctionType,
264 inherited.register_predicate(traits::Obligation::new(
267 trait_ref.without_const().to_predicate(tcx),
273 // Check that a function marked as `#[panic_handler]` has signature `fn(&PanicInfo) -> !`
274 if let Some(panic_impl_did) = tcx.lang_items().panic_impl() {
275 if panic_impl_did == hir.local_def_id(fn_id).to_def_id() {
276 if let Some(panic_info_did) = tcx.lang_items().panic_info() {
277 if *declared_ret_ty.kind() != ty::Never {
278 sess.span_err(decl.output.span(), "return type should be `!`");
281 let inputs = fn_sig.inputs();
282 let span = hir.span(fn_id);
283 if inputs.len() == 1 {
284 let arg_is_panic_info = match *inputs[0].kind() {
285 ty::Ref(region, ty, mutbl) => match *ty.kind() {
286 ty::Adt(ref adt, _) => {
287 adt.did == panic_info_did
288 && mutbl == hir::Mutability::Not
289 && *region != RegionKind::ReStatic
296 if !arg_is_panic_info {
297 sess.span_err(decl.inputs[0].span, "argument should be `&PanicInfo`");
300 if let Node::Item(item) = hir.get(fn_id) {
301 if let ItemKind::Fn(_, ref generics, _) = item.kind {
302 if !generics.params.is_empty() {
303 sess.span_err(span, "should have no type parameters");
308 let span = sess.source_map().guess_head_span(span);
309 sess.span_err(span, "function should have one argument");
312 sess.err("language item required, but not found: `panic_info`");
317 // Check that a function marked as `#[alloc_error_handler]` has signature `fn(Layout) -> !`
318 if let Some(alloc_error_handler_did) = tcx.lang_items().oom() {
319 if alloc_error_handler_did == hir.local_def_id(fn_id).to_def_id() {
320 if let Some(alloc_layout_did) = tcx.lang_items().alloc_layout() {
321 if *declared_ret_ty.kind() != ty::Never {
322 sess.span_err(decl.output.span(), "return type should be `!`");
325 let inputs = fn_sig.inputs();
326 let span = hir.span(fn_id);
327 if inputs.len() == 1 {
328 let arg_is_alloc_layout = match inputs[0].kind() {
329 ty::Adt(ref adt, _) => adt.did == alloc_layout_did,
333 if !arg_is_alloc_layout {
334 sess.span_err(decl.inputs[0].span, "argument should be `Layout`");
337 if let Node::Item(item) = hir.get(fn_id) {
338 if let ItemKind::Fn(_, ref generics, _) = item.kind {
339 if !generics.params.is_empty() {
342 "`#[alloc_error_handler]` function should have no type \
349 let span = sess.source_map().guess_head_span(span);
350 sess.span_err(span, "function should have one argument");
353 sess.err("language item required, but not found: `alloc_layout`");
361 pub(super) fn check_struct(tcx: TyCtxt<'_>, id: hir::HirId, span: Span) {
362 let def_id = tcx.hir().local_def_id(id);
363 let def = tcx.adt_def(def_id);
364 def.destructor(tcx); // force the destructor to be evaluated
365 check_representable(tcx, span, def_id);
368 check_simd(tcx, span, def_id);
371 check_transparent(tcx, span, def);
372 check_packed(tcx, span, def);
375 fn check_union(tcx: TyCtxt<'_>, id: hir::HirId, span: Span) {
376 let def_id = tcx.hir().local_def_id(id);
377 let def = tcx.adt_def(def_id);
378 def.destructor(tcx); // force the destructor to be evaluated
379 check_representable(tcx, span, def_id);
380 check_transparent(tcx, span, def);
381 check_union_fields(tcx, span, def_id);
382 check_packed(tcx, span, def);
385 /// Check that the fields of the `union` do not need dropping.
386 fn check_union_fields(tcx: TyCtxt<'_>, span: Span, item_def_id: LocalDefId) -> bool {
387 let item_type = tcx.type_of(item_def_id);
388 if let ty::Adt(def, substs) = item_type.kind() {
389 assert!(def.is_union());
390 let fields = &def.non_enum_variant().fields;
391 let param_env = tcx.param_env(item_def_id);
392 for field in fields {
393 let field_ty = field.ty(tcx, substs);
394 // We are currently checking the type this field came from, so it must be local.
395 let field_span = tcx.hir().span_if_local(field.did).unwrap();
396 if field_ty.needs_drop(tcx, param_env) {
401 "unions may not contain fields that need dropping"
403 .span_note(field_span, "`std::mem::ManuallyDrop` can be used to wrap the type")
409 span_bug!(span, "unions must be ty::Adt, but got {:?}", item_type.kind());
414 /// Check that a `static` is inhabited.
415 fn check_static_inhabited<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId, span: Span) {
416 // Make sure statics are inhabited.
417 // Other parts of the compiler assume that there are no uninhabited places. In principle it
418 // would be enough to check this for `extern` statics, as statics with an initializer will
419 // have UB during initialization if they are uninhabited, but there also seems to be no good
420 // reason to allow any statics to be uninhabited.
421 let ty = tcx.type_of(def_id);
422 let layout = match tcx.layout_of(ParamEnv::reveal_all().and(ty)) {
425 // Generic statics are rejected, but we still reach this case.
426 tcx.sess.delay_span_bug(span, "generic static must be rejected");
430 if layout.abi.is_uninhabited() {
431 tcx.struct_span_lint_hir(
433 tcx.hir().local_def_id_to_hir_id(def_id),
436 lint.build("static of uninhabited type")
437 .note("uninhabited statics cannot be initialized, and any access would be an immediate error")
444 /// Checks that an opaque type does not contain cycles and does not use `Self` or `T::Foo`
445 /// projections that would result in "inheriting lifetimes".
446 pub(super) fn check_opaque<'tcx>(
449 substs: SubstsRef<'tcx>,
451 origin: &hir::OpaqueTyOrigin,
453 check_opaque_for_inheriting_lifetimes(tcx, def_id, span);
454 if tcx.type_of(def_id).references_error() {
457 if check_opaque_for_cycles(tcx, def_id, substs, span, origin).is_err() {
460 check_opaque_meets_bounds(tcx, def_id, substs, span, origin);
463 /// Checks that an opaque type does not use `Self` or `T::Foo` projections that would result
464 /// in "inheriting lifetimes".
465 #[instrument(skip(tcx, span))]
466 pub(super) fn check_opaque_for_inheriting_lifetimes(
471 let item = tcx.hir().expect_item(tcx.hir().local_def_id_to_hir_id(def_id));
472 debug!(?item, ?span);
474 struct FoundParentLifetime;
475 struct FindParentLifetimeVisitor<'tcx>(&'tcx ty::Generics);
476 impl<'tcx> ty::fold::TypeVisitor<'tcx> for FindParentLifetimeVisitor<'tcx> {
477 type BreakTy = FoundParentLifetime;
479 fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> {
480 debug!("FindParentLifetimeVisitor: r={:?}", r);
481 if let RegionKind::ReEarlyBound(ty::EarlyBoundRegion { index, .. }) = r {
482 if *index < self.0.parent_count as u32 {
483 return ControlFlow::Break(FoundParentLifetime);
485 return ControlFlow::CONTINUE;
489 r.super_visit_with(self)
492 fn visit_const(&mut self, c: &'tcx ty::Const<'tcx>) -> ControlFlow<Self::BreakTy> {
493 if let ty::ConstKind::Unevaluated(..) = c.val {
494 // FIXME(#72219) We currently don't detect lifetimes within substs
495 // which would violate this check. Even though the particular substitution is not used
496 // within the const, this should still be fixed.
497 return ControlFlow::CONTINUE;
499 c.super_visit_with(self)
504 struct ProhibitOpaqueVisitor<'tcx> {
505 opaque_identity_ty: Ty<'tcx>,
506 generics: &'tcx ty::Generics,
509 impl<'tcx> ty::fold::TypeVisitor<'tcx> for ProhibitOpaqueVisitor<'tcx> {
510 type BreakTy = Ty<'tcx>;
512 fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
513 debug!("check_opaque_for_inheriting_lifetimes: (visit_ty) t={:?}", t);
514 if t == self.opaque_identity_ty {
515 ControlFlow::CONTINUE
517 t.super_visit_with(&mut FindParentLifetimeVisitor(self.generics))
518 .map_break(|FoundParentLifetime| t)
523 if let ItemKind::OpaqueTy(hir::OpaqueTy {
524 origin: hir::OpaqueTyOrigin::AsyncFn | hir::OpaqueTyOrigin::FnReturn,
528 let mut visitor = ProhibitOpaqueVisitor {
529 opaque_identity_ty: tcx.mk_opaque(
531 InternalSubsts::identity_for_item(tcx, def_id.to_def_id()),
533 generics: tcx.generics_of(def_id),
535 let prohibit_opaque = tcx
536 .explicit_item_bounds(def_id)
538 .try_for_each(|(predicate, _)| predicate.visit_with(&mut visitor));
540 "check_opaque_for_inheriting_lifetimes: prohibit_opaque={:?}, visitor={:?}",
541 prohibit_opaque, visitor
544 if let Some(ty) = prohibit_opaque.break_value() {
545 let is_async = match item.kind {
546 ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) => {
547 matches!(origin, hir::OpaqueTyOrigin::AsyncFn)
552 let mut err = struct_span_err!(
556 "`{}` return type cannot contain a projection or `Self` that references lifetimes from \
558 if is_async { "async fn" } else { "impl Trait" },
561 if let Ok(snippet) = tcx.sess.source_map().span_to_snippet(span) {
562 if snippet == "Self" {
565 "consider spelling out the type instead",
567 Applicability::MaybeIncorrect,
576 /// Checks that an opaque type does not contain cycles.
577 pub(super) fn check_opaque_for_cycles<'tcx>(
580 substs: SubstsRef<'tcx>,
582 origin: &hir::OpaqueTyOrigin,
583 ) -> Result<(), ErrorReported> {
584 if let Err(partially_expanded_type) = tcx.try_expand_impl_trait_type(def_id.to_def_id(), substs)
587 hir::OpaqueTyOrigin::AsyncFn => async_opaque_type_cycle_error(tcx, span),
588 hir::OpaqueTyOrigin::Binding => {
589 binding_opaque_type_cycle_error(tcx, def_id, span, partially_expanded_type)
591 _ => opaque_type_cycle_error(tcx, def_id, span),
599 /// Check that the concrete type behind `impl Trait` actually implements `Trait`.
601 /// This is mostly checked at the places that specify the opaque type, but we
602 /// check those cases in the `param_env` of that function, which may have
603 /// bounds not on this opaque type:
605 /// type X<T> = impl Clone
606 /// fn f<T: Clone>(t: T) -> X<T> {
610 /// Without this check the above code is incorrectly accepted: we would ICE if
611 /// some tried, for example, to clone an `Option<X<&mut ()>>`.
612 fn check_opaque_meets_bounds<'tcx>(
615 substs: SubstsRef<'tcx>,
617 origin: &hir::OpaqueTyOrigin,
620 // Checked when type checking the function containing them.
621 hir::OpaqueTyOrigin::FnReturn | hir::OpaqueTyOrigin::AsyncFn => return,
622 // Can have different predicates to their defining use
623 hir::OpaqueTyOrigin::Binding | hir::OpaqueTyOrigin::Misc => {}
626 let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
627 let param_env = tcx.param_env(def_id);
629 tcx.infer_ctxt().enter(move |infcx| {
630 let inh = Inherited::new(infcx, def_id);
631 let infcx = &inh.infcx;
632 let opaque_ty = tcx.mk_opaque(def_id.to_def_id(), substs);
634 let misc_cause = traits::ObligationCause::misc(span, hir_id);
636 let (_, opaque_type_map) = inh.register_infer_ok_obligations(
637 infcx.instantiate_opaque_types(def_id, hir_id, param_env, opaque_ty, span),
640 for (def_id, opaque_defn) in opaque_type_map {
642 .at(&misc_cause, param_env)
643 .eq(opaque_defn.concrete_ty, tcx.type_of(def_id).subst(tcx, opaque_defn.substs))
645 Ok(infer_ok) => inh.register_infer_ok_obligations(infer_ok),
646 Err(ty_err) => tcx.sess.delay_span_bug(
647 opaque_defn.definition_span,
649 "could not unify `{}` with revealed type:\n{}",
650 opaque_defn.concrete_ty, ty_err,
656 // Check that all obligations are satisfied by the implementation's
658 if let Err(ref errors) = inh.fulfillment_cx.borrow_mut().select_all_or_error(&infcx) {
659 infcx.report_fulfillment_errors(errors, None, false);
662 // Finally, resolve all regions. This catches wily misuses of
663 // lifetime parameters.
664 let fcx = FnCtxt::new(&inh, param_env, hir_id);
665 fcx.regionck_item(hir_id, span, &[]);
669 pub fn check_item_type<'tcx>(tcx: TyCtxt<'tcx>, it: &'tcx hir::Item<'tcx>) {
671 "check_item_type(it.hir_id={}, it.name={})",
673 tcx.def_path_str(tcx.hir().local_def_id(it.hir_id).to_def_id())
675 let _indenter = indenter();
677 // Consts can play a role in type-checking, so they are included here.
678 hir::ItemKind::Static(..) => {
679 let def_id = tcx.hir().local_def_id(it.hir_id);
680 tcx.ensure().typeck(def_id);
681 maybe_check_static_with_link_section(tcx, def_id, it.span);
682 check_static_inhabited(tcx, def_id, it.span);
684 hir::ItemKind::Const(..) => {
685 tcx.ensure().typeck(tcx.hir().local_def_id(it.hir_id));
687 hir::ItemKind::Enum(ref enum_definition, _) => {
688 check_enum(tcx, it.span, &enum_definition.variants, it.hir_id);
690 hir::ItemKind::Fn(..) => {} // entirely within check_item_body
691 hir::ItemKind::Impl { ref items, .. } => {
692 debug!("ItemKind::Impl {} with id {}", it.ident, it.hir_id);
693 let impl_def_id = tcx.hir().local_def_id(it.hir_id);
694 if let Some(impl_trait_ref) = tcx.impl_trait_ref(impl_def_id) {
695 check_impl_items_against_trait(tcx, it.span, impl_def_id, impl_trait_ref, items);
696 let trait_def_id = impl_trait_ref.def_id;
697 check_on_unimplemented(tcx, trait_def_id, it);
700 hir::ItemKind::Trait(_, _, _, _, ref items) => {
701 let def_id = tcx.hir().local_def_id(it.hir_id);
702 check_on_unimplemented(tcx, def_id.to_def_id(), it);
704 for item in items.iter() {
705 let item = tcx.hir().trait_item(item.id);
707 hir::TraitItemKind::Fn(ref sig, _) => {
708 let abi = sig.header.abi;
709 fn_maybe_err(tcx, item.ident.span, abi);
711 hir::TraitItemKind::Type(.., Some(_default)) => {
712 let item_def_id = tcx.hir().local_def_id(item.hir_id).to_def_id();
713 let assoc_item = tcx.associated_item(item_def_id);
715 InternalSubsts::identity_for_item(tcx, def_id.to_def_id());
716 let _: Result<_, rustc_errors::ErrorReported> = check_type_bounds(
721 ty::TraitRef { def_id: def_id.to_def_id(), substs: trait_substs },
728 hir::ItemKind::Struct(..) => {
729 check_struct(tcx, it.hir_id, it.span);
731 hir::ItemKind::Union(..) => {
732 check_union(tcx, it.hir_id, it.span);
734 hir::ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) => {
735 // HACK(jynelson): trying to infer the type of `impl trait` breaks documenting
736 // `async-std` (and `pub async fn` in general).
737 // Since rustdoc doesn't care about the concrete type behind `impl Trait`, just don't look at it!
738 // See https://github.com/rust-lang/rust/issues/75100
739 if !tcx.sess.opts.actually_rustdoc {
740 let def_id = tcx.hir().local_def_id(it.hir_id);
742 let substs = InternalSubsts::identity_for_item(tcx, def_id.to_def_id());
743 check_opaque(tcx, def_id, substs, it.span, &origin);
746 hir::ItemKind::TyAlias(..) => {
747 let def_id = tcx.hir().local_def_id(it.hir_id);
748 let pty_ty = tcx.type_of(def_id);
749 let generics = tcx.generics_of(def_id);
750 check_type_params_are_used(tcx, &generics, pty_ty);
752 hir::ItemKind::ForeignMod { abi, items } => {
753 check_abi(tcx, it.span, abi);
755 if abi == Abi::RustIntrinsic {
757 let item = tcx.hir().foreign_item(item.id);
758 intrinsic::check_intrinsic_type(tcx, item);
760 } else if abi == Abi::PlatformIntrinsic {
762 let item = tcx.hir().foreign_item(item.id);
763 intrinsic::check_platform_intrinsic_type(tcx, item);
767 let def_id = tcx.hir().local_def_id(item.id.hir_id);
768 let generics = tcx.generics_of(def_id);
769 let own_counts = generics.own_counts();
770 if generics.params.len() - own_counts.lifetimes != 0 {
771 let (kinds, kinds_pl, egs) = match (own_counts.types, own_counts.consts) {
772 (_, 0) => ("type", "types", Some("u32")),
773 // We don't specify an example value, because we can't generate
774 // a valid value for any type.
775 (0, _) => ("const", "consts", None),
776 _ => ("type or const", "types or consts", None),
782 "foreign items may not have {} parameters",
785 .span_label(item.span, &format!("can't have {} parameters", kinds))
787 // FIXME: once we start storing spans for type arguments, turn this
788 // into a suggestion.
790 "replace the {} parameters with concrete {}{}",
793 egs.map(|egs| format!(" like `{}`", egs)).unwrap_or_default(),
799 let item = tcx.hir().foreign_item(item.id);
801 hir::ForeignItemKind::Fn(ref fn_decl, _, _) => {
802 require_c_abi_if_c_variadic(tcx, fn_decl, abi, item.span);
804 hir::ForeignItemKind::Static(..) => {
805 check_static_inhabited(tcx, def_id, item.span);
812 _ => { /* nothing to do */ }
816 pub(super) fn check_on_unimplemented(tcx: TyCtxt<'_>, trait_def_id: DefId, item: &hir::Item<'_>) {
817 let item_def_id = tcx.hir().local_def_id(item.hir_id);
818 // an error would be reported if this fails.
819 let _ = traits::OnUnimplementedDirective::of_item(tcx, trait_def_id, item_def_id.to_def_id());
822 pub(super) fn check_specialization_validity<'tcx>(
824 trait_def: &ty::TraitDef,
825 trait_item: &ty::AssocItem,
827 impl_item: &hir::ImplItem<'_>,
829 let kind = match impl_item.kind {
830 hir::ImplItemKind::Const(..) => ty::AssocKind::Const,
831 hir::ImplItemKind::Fn(..) => ty::AssocKind::Fn,
832 hir::ImplItemKind::TyAlias(_) => ty::AssocKind::Type,
835 let ancestors = match trait_def.ancestors(tcx, impl_id) {
836 Ok(ancestors) => ancestors,
839 let mut ancestor_impls = ancestors
841 .filter_map(|parent| {
842 if parent.is_from_trait() {
845 Some((parent, parent.item(tcx, trait_item.ident, kind, trait_def.def_id)))
850 if ancestor_impls.peek().is_none() {
851 // No parent, nothing to specialize.
855 let opt_result = ancestor_impls.find_map(|(parent_impl, parent_item)| {
857 // Parent impl exists, and contains the parent item we're trying to specialize, but
858 // doesn't mark it `default`.
859 Some(parent_item) if traits::impl_item_is_final(tcx, &parent_item) => {
860 Some(Err(parent_impl.def_id()))
863 // Parent impl contains item and makes it specializable.
864 Some(_) => Some(Ok(())),
866 // Parent impl doesn't mention the item. This means it's inherited from the
867 // grandparent. In that case, if parent is a `default impl`, inherited items use the
868 // "defaultness" from the grandparent, else they are final.
870 if tcx.impl_defaultness(parent_impl.def_id()).is_default() {
873 Some(Err(parent_impl.def_id()))
879 // If `opt_result` is `None`, we have only encountered `default impl`s that don't contain the
880 // item. This is allowed, the item isn't actually getting specialized here.
881 let result = opt_result.unwrap_or(Ok(()));
883 if let Err(parent_impl) = result {
884 report_forbidden_specialization(tcx, impl_item, parent_impl);
888 pub(super) fn check_impl_items_against_trait<'tcx>(
890 full_impl_span: Span,
892 impl_trait_ref: ty::TraitRef<'tcx>,
893 impl_item_refs: &[hir::ImplItemRef<'_>],
895 let impl_span = tcx.sess.source_map().guess_head_span(full_impl_span);
897 // If the trait reference itself is erroneous (so the compilation is going
898 // to fail), skip checking the items here -- the `impl_item` table in `tcx`
899 // isn't populated for such impls.
900 if impl_trait_ref.references_error() {
904 // Negative impls are not expected to have any items
905 match tcx.impl_polarity(impl_id) {
906 ty::ImplPolarity::Reservation | ty::ImplPolarity::Positive => {}
907 ty::ImplPolarity::Negative => {
908 if let [first_item_ref, ..] = impl_item_refs {
909 let first_item_span = tcx.hir().impl_item(first_item_ref.id).span;
914 "negative impls cannot have any items"
922 // Locate trait definition and items
923 let trait_def = tcx.trait_def(impl_trait_ref.def_id);
925 let impl_items = || impl_item_refs.iter().map(|iiref| tcx.hir().impl_item(iiref.id));
927 // Check existing impl methods to see if they are both present in trait
928 // and compatible with trait signature
929 for impl_item in impl_items() {
930 let namespace = impl_item.kind.namespace();
931 let ty_impl_item = tcx.associated_item(tcx.hir().local_def_id(impl_item.hir_id));
932 let ty_trait_item = tcx
933 .associated_items(impl_trait_ref.def_id)
934 .find_by_name_and_namespace(tcx, ty_impl_item.ident, namespace, impl_trait_ref.def_id)
936 // Not compatible, but needed for the error message
937 tcx.associated_items(impl_trait_ref.def_id)
938 .filter_by_name(tcx, ty_impl_item.ident, impl_trait_ref.def_id)
942 // Check that impl definition matches trait definition
943 if let Some(ty_trait_item) = ty_trait_item {
944 match impl_item.kind {
945 hir::ImplItemKind::Const(..) => {
946 // Find associated const definition.
947 if ty_trait_item.kind == ty::AssocKind::Const {
956 let mut err = struct_span_err!(
960 "item `{}` is an associated const, \
961 which doesn't match its trait `{}`",
963 impl_trait_ref.print_only_trait_path()
965 err.span_label(impl_item.span, "does not match trait");
966 // We can only get the spans from local trait definition
967 // Same for E0324 and E0325
968 if let Some(trait_span) = tcx.hir().span_if_local(ty_trait_item.def_id) {
969 err.span_label(trait_span, "item in trait");
974 hir::ImplItemKind::Fn(..) => {
975 let opt_trait_span = tcx.hir().span_if_local(ty_trait_item.def_id);
976 if ty_trait_item.kind == ty::AssocKind::Fn {
986 let mut err = struct_span_err!(
990 "item `{}` is an associated method, \
991 which doesn't match its trait `{}`",
993 impl_trait_ref.print_only_trait_path()
995 err.span_label(impl_item.span, "does not match trait");
996 if let Some(trait_span) = opt_trait_span {
997 err.span_label(trait_span, "item in trait");
1002 hir::ImplItemKind::TyAlias(_) => {
1003 let opt_trait_span = tcx.hir().span_if_local(ty_trait_item.def_id);
1004 if ty_trait_item.kind == ty::AssocKind::Type {
1014 let mut err = struct_span_err!(
1018 "item `{}` is an associated type, \
1019 which doesn't match its trait `{}`",
1021 impl_trait_ref.print_only_trait_path()
1023 err.span_label(impl_item.span, "does not match trait");
1024 if let Some(trait_span) = opt_trait_span {
1025 err.span_label(trait_span, "item in trait");
1032 check_specialization_validity(
1036 impl_id.to_def_id(),
1042 // Check for missing items from trait
1043 let mut missing_items = Vec::new();
1044 if let Ok(ancestors) = trait_def.ancestors(tcx, impl_id.to_def_id()) {
1045 for trait_item in tcx.associated_items(impl_trait_ref.def_id).in_definition_order() {
1046 let is_implemented = ancestors
1047 .leaf_def(tcx, trait_item.ident, trait_item.kind)
1048 .map(|node_item| !node_item.defining_node.is_from_trait())
1051 if !is_implemented && tcx.impl_defaultness(impl_id).is_final() {
1052 if !trait_item.defaultness.has_value() {
1053 missing_items.push(*trait_item);
1059 if !missing_items.is_empty() {
1060 missing_items_err(tcx, impl_span, &missing_items, full_impl_span);
1064 /// Checks whether a type can be represented in memory. In particular, it
1065 /// identifies types that contain themselves without indirection through a
1066 /// pointer, which would mean their size is unbounded.
1067 pub(super) fn check_representable(tcx: TyCtxt<'_>, sp: Span, item_def_id: LocalDefId) -> bool {
1068 let rty = tcx.type_of(item_def_id);
1070 // Check that it is possible to represent this type. This call identifies
1071 // (1) types that contain themselves and (2) types that contain a different
1072 // recursive type. It is only necessary to throw an error on those that
1073 // contain themselves. For case 2, there must be an inner type that will be
1074 // caught by case 1.
1075 match rty.is_representable(tcx, sp) {
1076 Representability::SelfRecursive(spans) => {
1077 recursive_type_with_infinite_size_error(tcx, item_def_id.to_def_id(), spans);
1080 Representability::Representable | Representability::ContainsRecursive => (),
1085 pub fn check_simd(tcx: TyCtxt<'_>, sp: Span, def_id: LocalDefId) {
1086 let t = tcx.type_of(def_id);
1087 if let ty::Adt(def, substs) = t.kind() {
1088 if def.is_struct() {
1089 let fields = &def.non_enum_variant().fields;
1090 if fields.is_empty() {
1091 struct_span_err!(tcx.sess, sp, E0075, "SIMD vector cannot be empty").emit();
1094 let e = fields[0].ty(tcx, substs);
1095 if !fields.iter().all(|f| f.ty(tcx, substs) == e) {
1096 struct_span_err!(tcx.sess, sp, E0076, "SIMD vector should be homogeneous")
1097 .span_label(sp, "SIMD elements must have the same type")
1102 let len = if let ty::Array(_ty, c) = e.kind() {
1103 c.try_eval_usize(tcx, tcx.param_env(def.did))
1105 Some(fields.len() as u64)
1107 if let Some(len) = len {
1109 struct_span_err!(tcx.sess, sp, E0075, "SIMD vector cannot be empty").emit();
1111 } else if len > 65536 {
1116 "SIMD vector cannot have more than 65536 elements"
1124 ty::Param(_) => { /* struct<T>(T, T, T, T) is ok */ }
1125 _ if e.is_machine() => { /* struct(u8, u8, u8, u8) is ok */ }
1126 ty::Array(ty, _c) if ty.is_machine() => { /* struct([f32; 4]) */ }
1132 "SIMD vector element type should be a \
1133 primitive scalar (integer/float/pointer) type"
1143 pub(super) fn check_packed(tcx: TyCtxt<'_>, sp: Span, def: &ty::AdtDef) {
1144 let repr = def.repr;
1146 for attr in tcx.get_attrs(def.did).iter() {
1147 for r in attr::find_repr_attrs(&tcx.sess, attr) {
1148 if let attr::ReprPacked(pack) = r {
1149 if let Some(repr_pack) = repr.pack {
1150 if pack as u64 != repr_pack.bytes() {
1155 "type has conflicting packed representation hints"
1163 if repr.align.is_some() {
1168 "type has conflicting packed and align representation hints"
1172 if let Some(def_spans) = check_packed_inner(tcx, def.did, &mut vec![]) {
1173 let mut err = struct_span_err!(
1177 "packed type cannot transitively contain a `#[repr(align)]` type"
1181 tcx.def_span(def_spans[0].0),
1183 "`{}` has a `#[repr(align)]` attribute",
1184 tcx.item_name(def_spans[0].0)
1188 if def_spans.len() > 2 {
1189 let mut first = true;
1190 for (adt_def, span) in def_spans.iter().skip(1).rev() {
1191 let ident = tcx.item_name(*adt_def);
1196 "`{}` contains a field of type `{}`",
1197 tcx.type_of(def.did),
1201 format!("...which contains a field of type `{}`", ident)
1214 pub(super) fn check_packed_inner(
1217 stack: &mut Vec<DefId>,
1218 ) -> Option<Vec<(DefId, Span)>> {
1219 if let ty::Adt(def, substs) = tcx.type_of(def_id).kind() {
1220 if def.is_struct() || def.is_union() {
1221 if def.repr.align.is_some() {
1222 return Some(vec![(def.did, DUMMY_SP)]);
1226 for field in &def.non_enum_variant().fields {
1227 if let ty::Adt(def, _) = field.ty(tcx, substs).kind() {
1228 if !stack.contains(&def.did) {
1229 if let Some(mut defs) = check_packed_inner(tcx, def.did, stack) {
1230 defs.push((def.did, field.ident.span));
1243 pub(super) fn check_transparent<'tcx>(tcx: TyCtxt<'tcx>, sp: Span, adt: &'tcx ty::AdtDef) {
1244 if !adt.repr.transparent() {
1247 let sp = tcx.sess.source_map().guess_head_span(sp);
1249 if adt.is_union() && !tcx.features().transparent_unions {
1251 &tcx.sess.parse_sess,
1252 sym::transparent_unions,
1254 "transparent unions are unstable",
1259 if adt.variants.len() != 1 {
1260 bad_variant_count(tcx, adt, sp, adt.did);
1261 if adt.variants.is_empty() {
1262 // Don't bother checking the fields. No variants (and thus no fields) exist.
1267 // For each field, figure out if it's known to be a ZST and align(1)
1268 let field_infos = adt.all_fields().map(|field| {
1269 let ty = field.ty(tcx, InternalSubsts::identity_for_item(tcx, field.did));
1270 let param_env = tcx.param_env(field.did);
1271 let layout = tcx.layout_of(param_env.and(ty));
1272 // We are currently checking the type this field came from, so it must be local
1273 let span = tcx.hir().span_if_local(field.did).unwrap();
1274 let zst = layout.map(|layout| layout.is_zst()).unwrap_or(false);
1275 let align1 = layout.map(|layout| layout.align.abi.bytes() == 1).unwrap_or(false);
1279 let non_zst_fields =
1280 field_infos.clone().filter_map(|(span, zst, _align1)| if !zst { Some(span) } else { None });
1281 let non_zst_count = non_zst_fields.clone().count();
1282 if non_zst_count != 1 {
1283 bad_non_zero_sized_fields(tcx, adt, non_zst_count, non_zst_fields, sp);
1285 for (span, zst, align1) in field_infos {
1291 "zero-sized field in transparent {} has alignment larger than 1",
1294 .span_label(span, "has alignment larger than 1")
1300 #[allow(trivial_numeric_casts)]
1301 pub fn check_enum<'tcx>(
1304 vs: &'tcx [hir::Variant<'tcx>],
1307 let def_id = tcx.hir().local_def_id(id);
1308 let def = tcx.adt_def(def_id);
1309 def.destructor(tcx); // force the destructor to be evaluated
1312 let attributes = tcx.get_attrs(def_id.to_def_id());
1313 if let Some(attr) = tcx.sess.find_by_name(&attributes, sym::repr) {
1318 "unsupported representation for zero-variant enum"
1320 .span_label(sp, "zero-variant enum")
1325 let repr_type_ty = def.repr.discr_type().to_ty(tcx);
1326 if repr_type_ty == tcx.types.i128 || repr_type_ty == tcx.types.u128 {
1327 if !tcx.features().repr128 {
1329 &tcx.sess.parse_sess,
1332 "repr with 128-bit type is unstable",
1339 if let Some(ref e) = v.disr_expr {
1340 tcx.ensure().typeck(tcx.hir().local_def_id(e.hir_id));
1344 if tcx.adt_def(def_id).repr.int.is_none() && tcx.features().arbitrary_enum_discriminant {
1345 let is_unit = |var: &hir::Variant<'_>| matches!(var.data, hir::VariantData::Unit(..));
1347 let has_disr = |var: &hir::Variant<'_>| var.disr_expr.is_some();
1348 let has_non_units = vs.iter().any(|var| !is_unit(var));
1349 let disr_units = vs.iter().any(|var| is_unit(&var) && has_disr(&var));
1350 let disr_non_unit = vs.iter().any(|var| !is_unit(&var) && has_disr(&var));
1352 if disr_non_unit || (disr_units && has_non_units) {
1354 struct_span_err!(tcx.sess, sp, E0732, "`#[repr(inttype)]` must be specified");
1359 let mut disr_vals: Vec<Discr<'tcx>> = Vec::with_capacity(vs.len());
1360 for ((_, discr), v) in def.discriminants(tcx).zip(vs) {
1361 // Check for duplicate discriminant values
1362 if let Some(i) = disr_vals.iter().position(|&x| x.val == discr.val) {
1363 let variant_did = def.variants[VariantIdx::new(i)].def_id;
1364 let variant_i_hir_id = tcx.hir().local_def_id_to_hir_id(variant_did.expect_local());
1365 let variant_i = tcx.hir().expect_variant(variant_i_hir_id);
1366 let i_span = match variant_i.disr_expr {
1367 Some(ref expr) => tcx.hir().span(expr.hir_id),
1368 None => tcx.hir().span(variant_i_hir_id),
1370 let span = match v.disr_expr {
1371 Some(ref expr) => tcx.hir().span(expr.hir_id),
1378 "discriminant value `{}` already exists",
1381 .span_label(i_span, format!("first use of `{}`", disr_vals[i]))
1382 .span_label(span, format!("enum already has `{}`", disr_vals[i]))
1385 disr_vals.push(discr);
1388 check_representable(tcx, sp, def_id);
1389 check_transparent(tcx, sp, def);
1392 pub(super) fn check_type_params_are_used<'tcx>(
1394 generics: &ty::Generics,
1397 debug!("check_type_params_are_used(generics={:?}, ty={:?})", generics, ty);
1399 assert_eq!(generics.parent, None);
1401 if generics.own_counts().types == 0 {
1405 let mut params_used = BitSet::new_empty(generics.params.len());
1407 if ty.references_error() {
1408 // If there is already another error, do not emit
1409 // an error for not using a type parameter.
1410 assert!(tcx.sess.has_errors());
1414 for leaf in ty.walk() {
1415 if let GenericArgKind::Type(leaf_ty) = leaf.unpack() {
1416 if let ty::Param(param) = leaf_ty.kind() {
1417 debug!("found use of ty param {:?}", param);
1418 params_used.insert(param.index);
1423 for param in &generics.params {
1424 if !params_used.contains(param.index) {
1425 if let ty::GenericParamDefKind::Type { .. } = param.kind {
1426 let span = tcx.def_span(param.def_id);
1431 "type parameter `{}` is unused",
1434 .span_label(span, "unused type parameter")
1441 pub(super) fn check_mod_item_types(tcx: TyCtxt<'_>, module_def_id: LocalDefId) {
1442 tcx.hir().visit_item_likes_in_module(module_def_id, &mut CheckItemTypesVisitor { tcx });
1445 pub(super) fn check_item_well_formed(tcx: TyCtxt<'_>, def_id: LocalDefId) {
1446 wfcheck::check_item_well_formed(tcx, def_id);
1449 pub(super) fn check_trait_item_well_formed(tcx: TyCtxt<'_>, def_id: LocalDefId) {
1450 wfcheck::check_trait_item(tcx, def_id);
1453 pub(super) fn check_impl_item_well_formed(tcx: TyCtxt<'_>, def_id: LocalDefId) {
1454 wfcheck::check_impl_item(tcx, def_id);
1457 fn async_opaque_type_cycle_error(tcx: TyCtxt<'tcx>, span: Span) {
1458 struct_span_err!(tcx.sess, span, E0733, "recursion in an `async fn` requires boxing")
1459 .span_label(span, "recursive `async fn`")
1460 .note("a recursive `async fn` must be rewritten to return a boxed `dyn Future`")
1464 /// Emit an error for recursive opaque types.
1466 /// If this is a return `impl Trait`, find the item's return expressions and point at them. For
1467 /// direct recursion this is enough, but for indirect recursion also point at the last intermediary
1470 /// If all the return expressions evaluate to `!`, then we explain that the error will go away
1471 /// after changing it. This can happen when a user uses `panic!()` or similar as a placeholder.
1472 fn opaque_type_cycle_error(tcx: TyCtxt<'tcx>, def_id: LocalDefId, span: Span) {
1473 let mut err = struct_span_err!(tcx.sess, span, E0720, "cannot resolve opaque type");
1475 let mut label = false;
1476 if let Some((hir_id, visitor)) = get_owner_return_paths(tcx, def_id) {
1477 let typeck_results = tcx.typeck(tcx.hir().local_def_id(hir_id));
1481 .filter_map(|expr| typeck_results.node_type_opt(expr.hir_id))
1482 .all(|ty| matches!(ty.kind(), ty::Never))
1487 .filter(|expr| typeck_results.node_type_opt(expr.hir_id).is_some())
1488 .map(|expr| expr.span)
1489 .collect::<Vec<Span>>();
1490 let span_len = spans.len();
1492 err.span_label(spans[0], "this returned value is of `!` type");
1494 let mut multispan: MultiSpan = spans.clone().into();
1497 .push_span_label(span, "this returned value is of `!` type".to_string());
1499 err.span_note(multispan, "these returned values have a concrete \"never\" type");
1501 err.help("this error will resolve once the item's body returns a concrete type");
1503 let mut seen = FxHashSet::default();
1505 err.span_label(span, "recursive opaque type");
1507 for (sp, ty) in visitor
1510 .filter_map(|e| typeck_results.node_type_opt(e.hir_id).map(|t| (e.span, t)))
1511 .filter(|(_, ty)| !matches!(ty.kind(), ty::Never))
1513 struct VisitTypes(Vec<DefId>);
1514 impl<'tcx> ty::fold::TypeVisitor<'tcx> for VisitTypes {
1515 fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
1517 ty::Opaque(def, _) => {
1519 ControlFlow::CONTINUE
1521 _ => t.super_visit_with(self),
1525 let mut visitor = VisitTypes(vec![]);
1526 ty.visit_with(&mut visitor);
1527 for def_id in visitor.0 {
1528 let ty_span = tcx.def_span(def_id);
1529 if !seen.contains(&ty_span) {
1530 err.span_label(ty_span, &format!("returning this opaque type `{}`", ty));
1531 seen.insert(ty_span);
1533 err.span_label(sp, &format!("returning here with type `{}`", ty));
1539 err.span_label(span, "cannot resolve opaque type");