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.set(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 Node::TraitItem(hir::TraitItem {
107 kind: hir::TraitItemKind::Fn(header, ..),
110 // Closures are RustCall, but they tuple their arguments, so shouldn't be checked
111 Node::Expr(hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => None,
112 node => bug!("Item being checked wasn't a function/closure: {:?}", node),
115 if let Some(header) = item {
116 tcx.sess.span_err(header.span, "functions with the \"rust-call\" ABI must take a single non-self argument that is a tuple")
120 if fn_sig.inputs().len() != expected_args {
123 // FIXME(CraftSpider) Add a check on parameter expansion, so we don't just make the ICE happen later on
124 // This will probably require wide-scale changes to support a TupleKind obligation
125 // We can't resolve this without knowing the type of the param
126 if !matches!(fn_sig.inputs()[expected_args - 1].kind(), ty::Tuple(_) | ty::Param(_)) {
132 if body.generator_kind.is_some() && can_be_generator.is_some() {
134 .next_ty_var(TypeVariableOrigin { kind: TypeVariableOriginKind::TypeInference, span });
135 fcx.require_type_is_sized(yield_ty, span, traits::SizedYieldType);
137 // Resume type defaults to `()` if the generator has no argument.
138 let resume_ty = fn_sig.inputs().get(0).copied().unwrap_or_else(|| tcx.mk_unit());
140 fcx.resume_yield_tys = Some((resume_ty, yield_ty));
143 let outer_def_id = tcx.closure_base_def_id(hir.local_def_id(fn_id).to_def_id()).expect_local();
144 let outer_hir_id = hir.local_def_id_to_hir_id(outer_def_id);
145 GatherLocalsVisitor::new(&fcx, outer_hir_id).visit_body(body);
147 // C-variadic fns also have a `VaList` input that's not listed in `fn_sig`
148 // (as it's created inside the body itself, not passed in from outside).
149 let maybe_va_list = if fn_sig.c_variadic {
150 let span = body.params.last().unwrap().span;
151 let va_list_did = tcx.require_lang_item(LangItem::VaList, Some(span));
152 let region = fcx.next_region_var(RegionVariableOrigin::MiscVariable(span));
154 Some(tcx.type_of(va_list_did).subst(tcx, &[region.into()]))
159 // Add formal parameters.
160 let inputs_hir = hir.fn_decl_by_hir_id(fn_id).map(|decl| &decl.inputs);
161 let inputs_fn = fn_sig.inputs().iter().copied();
162 for (idx, (param_ty, param)) in inputs_fn.chain(maybe_va_list).zip(body.params).enumerate() {
163 // Check the pattern.
164 let ty_span = try { inputs_hir?.get(idx)?.span };
165 fcx.check_pat_top(¶m.pat, param_ty, ty_span, false);
167 // Check that argument is Sized.
168 // The check for a non-trivial pattern is a hack to avoid duplicate warnings
169 // for simple cases like `fn foo(x: Trait)`,
170 // where we would error once on the parameter as a whole, and once on the binding `x`.
171 if param.pat.simple_ident().is_none() && !tcx.features().unsized_fn_params {
172 fcx.require_type_is_sized(param_ty, param.pat.span, traits::SizedArgumentType(ty_span));
175 fcx.write_ty(param.hir_id, param_ty);
178 inherited.typeck_results.borrow_mut().liberated_fn_sigs_mut().insert(fn_id, fn_sig);
180 fcx.in_tail_expr = true;
181 if let ty::Dynamic(..) = declared_ret_ty.kind() {
182 // FIXME: We need to verify that the return type is `Sized` after the return expression has
183 // been evaluated so that we have types available for all the nodes being returned, but that
184 // requires the coerced evaluated type to be stored. Moving `check_return_expr` before this
185 // causes unsized errors caused by the `declared_ret_ty` to point at the return expression,
186 // while keeping the current ordering we will ignore the tail expression's type because we
187 // don't know it yet. We can't do `check_expr_kind` while keeping `check_return_expr`
188 // because we will trigger "unreachable expression" lints unconditionally.
189 // Because of all of this, we perform a crude check to know whether the simplest `!Sized`
190 // case that a newcomer might make, returning a bare trait, and in that case we populate
191 // the tail expression's type so that the suggestion will be correct, but ignore all other
193 fcx.check_expr(&body.value);
194 fcx.require_type_is_sized(declared_ret_ty, decl.output.span(), traits::SizedReturnType);
195 tcx.sess.delay_span_bug(decl.output.span(), "`!Sized` return type");
197 fcx.require_type_is_sized(declared_ret_ty, decl.output.span(), traits::SizedReturnType);
198 fcx.check_return_expr(&body.value);
200 fcx.in_tail_expr = false;
202 // We insert the deferred_generator_interiors entry after visiting the body.
203 // This ensures that all nested generators appear before the entry of this generator.
204 // resolve_generator_interiors relies on this property.
205 let gen_ty = if let (Some(_), Some(gen_kind)) = (can_be_generator, body.generator_kind) {
207 .next_ty_var(TypeVariableOrigin { kind: TypeVariableOriginKind::MiscVariable, span });
208 fcx.deferred_generator_interiors.borrow_mut().push((body.id(), interior, gen_kind));
210 let (resume_ty, yield_ty) = fcx.resume_yield_tys.unwrap();
211 Some(GeneratorTypes {
215 movability: can_be_generator.unwrap(),
221 // Finalize the return check by taking the LUB of the return types
222 // we saw and assigning it to the expected return type. This isn't
223 // really expected to fail, since the coercions would have failed
224 // earlier when trying to find a LUB.
226 // However, the behavior around `!` is sort of complex. In the
227 // event that the `actual_return_ty` comes back as `!`, that
228 // indicates that the fn either does not return or "returns" only
229 // values of type `!`. In this case, if there is an expected
230 // return type that is *not* `!`, that should be ok. But if the
231 // return type is being inferred, we want to "fallback" to `!`:
233 // let x = move || panic!();
235 // To allow for that, I am creating a type variable with diverging
236 // fallback. This was deemed ever so slightly better than unifying
237 // the return value with `!` because it allows for the caller to
238 // make more assumptions about the return type (e.g., they could do
240 // let y: Option<u32> = Some(x());
242 // which would then cause this return type to become `u32`, not
244 let coercion = fcx.ret_coercion.take().unwrap().into_inner();
245 let mut actual_return_ty = coercion.complete(&fcx);
246 if actual_return_ty.is_never() {
247 actual_return_ty = fcx.next_diverging_ty_var(TypeVariableOrigin {
248 kind: TypeVariableOriginKind::DivergingFn,
252 fcx.demand_suptype(span, revealed_ret_ty, actual_return_ty);
254 // Check that the main return type implements the termination trait.
255 if let Some(term_id) = tcx.lang_items().termination() {
256 if let Some((def_id, EntryFnType::Main)) = tcx.entry_fn(LOCAL_CRATE) {
257 let main_id = hir.local_def_id_to_hir_id(def_id);
258 if main_id == fn_id {
259 let substs = tcx.mk_substs_trait(declared_ret_ty, &[]);
260 let trait_ref = ty::TraitRef::new(term_id, substs);
261 let return_ty_span = decl.output.span();
262 let cause = traits::ObligationCause::new(
265 ObligationCauseCode::MainFunctionType,
268 inherited.register_predicate(traits::Obligation::new(
271 trait_ref.without_const().to_predicate(tcx),
277 // Check that a function marked as `#[panic_handler]` has signature `fn(&PanicInfo) -> !`
278 if let Some(panic_impl_did) = tcx.lang_items().panic_impl() {
279 if panic_impl_did == hir.local_def_id(fn_id).to_def_id() {
280 if let Some(panic_info_did) = tcx.lang_items().panic_info() {
281 if *declared_ret_ty.kind() != ty::Never {
282 sess.span_err(decl.output.span(), "return type should be `!`");
285 let inputs = fn_sig.inputs();
286 let span = hir.span(fn_id);
287 if inputs.len() == 1 {
288 let arg_is_panic_info = match *inputs[0].kind() {
289 ty::Ref(region, ty, mutbl) => match *ty.kind() {
290 ty::Adt(ref adt, _) => {
291 adt.did == panic_info_did
292 && mutbl == hir::Mutability::Not
293 && *region != RegionKind::ReStatic
300 if !arg_is_panic_info {
301 sess.span_err(decl.inputs[0].span, "argument should be `&PanicInfo`");
304 if let Node::Item(item) = hir.get(fn_id) {
305 if let ItemKind::Fn(_, ref generics, _) = item.kind {
306 if !generics.params.is_empty() {
307 sess.span_err(span, "should have no type parameters");
312 let span = sess.source_map().guess_head_span(span);
313 sess.span_err(span, "function should have one argument");
316 sess.err("language item required, but not found: `panic_info`");
321 // Check that a function marked as `#[alloc_error_handler]` has signature `fn(Layout) -> !`
322 if let Some(alloc_error_handler_did) = tcx.lang_items().oom() {
323 if alloc_error_handler_did == hir.local_def_id(fn_id).to_def_id() {
324 if let Some(alloc_layout_did) = tcx.lang_items().alloc_layout() {
325 if *declared_ret_ty.kind() != ty::Never {
326 sess.span_err(decl.output.span(), "return type should be `!`");
329 let inputs = fn_sig.inputs();
330 let span = hir.span(fn_id);
331 if inputs.len() == 1 {
332 let arg_is_alloc_layout = match inputs[0].kind() {
333 ty::Adt(ref adt, _) => adt.did == alloc_layout_did,
337 if !arg_is_alloc_layout {
338 sess.span_err(decl.inputs[0].span, "argument should be `Layout`");
341 if let Node::Item(item) = hir.get(fn_id) {
342 if let ItemKind::Fn(_, ref generics, _) = item.kind {
343 if !generics.params.is_empty() {
346 "`#[alloc_error_handler]` function should have no type \
353 let span = sess.source_map().guess_head_span(span);
354 sess.span_err(span, "function should have one argument");
357 sess.err("language item required, but not found: `alloc_layout`");
365 pub(super) fn check_struct(tcx: TyCtxt<'_>, id: hir::HirId, span: Span) {
366 let def_id = tcx.hir().local_def_id(id);
367 let def = tcx.adt_def(def_id);
368 def.destructor(tcx); // force the destructor to be evaluated
369 check_representable(tcx, span, def_id);
372 check_simd(tcx, span, def_id);
375 check_transparent(tcx, span, def);
376 check_packed(tcx, span, def);
379 fn check_union(tcx: TyCtxt<'_>, id: hir::HirId, span: Span) {
380 let def_id = tcx.hir().local_def_id(id);
381 let def = tcx.adt_def(def_id);
382 def.destructor(tcx); // force the destructor to be evaluated
383 check_representable(tcx, span, def_id);
384 check_transparent(tcx, span, def);
385 check_union_fields(tcx, span, def_id);
386 check_packed(tcx, span, def);
389 /// Check that the fields of the `union` do not need dropping.
390 fn check_union_fields(tcx: TyCtxt<'_>, span: Span, item_def_id: LocalDefId) -> bool {
391 let item_type = tcx.type_of(item_def_id);
392 if let ty::Adt(def, substs) = item_type.kind() {
393 assert!(def.is_union());
394 let fields = &def.non_enum_variant().fields;
395 let param_env = tcx.param_env(item_def_id);
396 for field in fields {
397 let field_ty = field.ty(tcx, substs);
398 // We are currently checking the type this field came from, so it must be local.
399 let field_span = tcx.hir().span_if_local(field.did).unwrap();
400 if field_ty.needs_drop(tcx, param_env) {
405 "unions may not contain fields that need dropping"
407 .span_note(field_span, "`std::mem::ManuallyDrop` can be used to wrap the type")
413 span_bug!(span, "unions must be ty::Adt, but got {:?}", item_type.kind());
418 /// Check that a `static` is inhabited.
419 fn check_static_inhabited<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId, span: Span) {
420 // Make sure statics are inhabited.
421 // Other parts of the compiler assume that there are no uninhabited places. In principle it
422 // would be enough to check this for `extern` statics, as statics with an initializer will
423 // have UB during initialization if they are uninhabited, but there also seems to be no good
424 // reason to allow any statics to be uninhabited.
425 let ty = tcx.type_of(def_id);
426 let layout = match tcx.layout_of(ParamEnv::reveal_all().and(ty)) {
429 // Generic statics are rejected, but we still reach this case.
430 tcx.sess.delay_span_bug(span, "generic static must be rejected");
434 if layout.abi.is_uninhabited() {
435 tcx.struct_span_lint_hir(
437 tcx.hir().local_def_id_to_hir_id(def_id),
440 lint.build("static of uninhabited type")
441 .note("uninhabited statics cannot be initialized, and any access would be an immediate error")
448 /// Checks that an opaque type does not contain cycles and does not use `Self` or `T::Foo`
449 /// projections that would result in "inheriting lifetimes".
450 pub(super) fn check_opaque<'tcx>(
453 substs: SubstsRef<'tcx>,
455 origin: &hir::OpaqueTyOrigin,
457 check_opaque_for_inheriting_lifetimes(tcx, def_id, span);
458 if tcx.type_of(def_id).references_error() {
461 if check_opaque_for_cycles(tcx, def_id, substs, span, origin).is_err() {
464 check_opaque_meets_bounds(tcx, def_id, substs, span, origin);
467 /// Checks that an opaque type does not use `Self` or `T::Foo` projections that would result
468 /// in "inheriting lifetimes".
469 #[instrument(skip(tcx, span))]
470 pub(super) fn check_opaque_for_inheriting_lifetimes(
475 let item = tcx.hir().expect_item(tcx.hir().local_def_id_to_hir_id(def_id));
476 debug!(?item, ?span);
478 struct FoundParentLifetime;
479 struct FindParentLifetimeVisitor<'tcx>(&'tcx ty::Generics);
480 impl<'tcx> ty::fold::TypeVisitor<'tcx> for FindParentLifetimeVisitor<'tcx> {
481 type BreakTy = FoundParentLifetime;
483 fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> {
484 debug!("FindParentLifetimeVisitor: r={:?}", r);
485 if let RegionKind::ReEarlyBound(ty::EarlyBoundRegion { index, .. }) = r {
486 if *index < self.0.parent_count as u32 {
487 return ControlFlow::Break(FoundParentLifetime);
489 return ControlFlow::CONTINUE;
493 r.super_visit_with(self)
496 fn visit_const(&mut self, c: &'tcx ty::Const<'tcx>) -> ControlFlow<Self::BreakTy> {
497 if let ty::ConstKind::Unevaluated(..) = c.val {
498 // FIXME(#72219) We currently don't detect lifetimes within substs
499 // which would violate this check. Even though the particular substitution is not used
500 // within the const, this should still be fixed.
501 return ControlFlow::CONTINUE;
503 c.super_visit_with(self)
508 struct ProhibitOpaqueVisitor<'tcx> {
509 opaque_identity_ty: Ty<'tcx>,
510 generics: &'tcx ty::Generics,
513 impl<'tcx> ty::fold::TypeVisitor<'tcx> for ProhibitOpaqueVisitor<'tcx> {
514 type BreakTy = Ty<'tcx>;
516 fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
517 debug!("check_opaque_for_inheriting_lifetimes: (visit_ty) t={:?}", t);
518 if t == self.opaque_identity_ty {
519 ControlFlow::CONTINUE
521 t.super_visit_with(&mut FindParentLifetimeVisitor(self.generics))
522 .map_break(|FoundParentLifetime| t)
527 if let ItemKind::OpaqueTy(hir::OpaqueTy {
528 origin: hir::OpaqueTyOrigin::AsyncFn | hir::OpaqueTyOrigin::FnReturn,
532 let mut visitor = ProhibitOpaqueVisitor {
533 opaque_identity_ty: tcx.mk_opaque(
535 InternalSubsts::identity_for_item(tcx, def_id.to_def_id()),
537 generics: tcx.generics_of(def_id),
539 let prohibit_opaque = tcx
540 .explicit_item_bounds(def_id)
542 .try_for_each(|(predicate, _)| predicate.visit_with(&mut visitor));
544 "check_opaque_for_inheriting_lifetimes: prohibit_opaque={:?}, visitor={:?}",
545 prohibit_opaque, visitor
548 if let Some(ty) = prohibit_opaque.break_value() {
549 let is_async = match item.kind {
550 ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) => {
551 matches!(origin, hir::OpaqueTyOrigin::AsyncFn)
556 let mut err = struct_span_err!(
560 "`{}` return type cannot contain a projection or `Self` that references lifetimes from \
562 if is_async { "async fn" } else { "impl Trait" },
565 if let Ok(snippet) = tcx.sess.source_map().span_to_snippet(span) {
566 if snippet == "Self" {
569 "consider spelling out the type instead",
571 Applicability::MaybeIncorrect,
580 /// Checks that an opaque type does not contain cycles.
581 pub(super) fn check_opaque_for_cycles<'tcx>(
584 substs: SubstsRef<'tcx>,
586 origin: &hir::OpaqueTyOrigin,
587 ) -> Result<(), ErrorReported> {
588 if let Err(partially_expanded_type) = tcx.try_expand_impl_trait_type(def_id.to_def_id(), substs)
591 hir::OpaqueTyOrigin::AsyncFn => async_opaque_type_cycle_error(tcx, span),
592 hir::OpaqueTyOrigin::Binding => {
593 binding_opaque_type_cycle_error(tcx, def_id, span, partially_expanded_type)
595 _ => opaque_type_cycle_error(tcx, def_id, span),
603 /// Check that the concrete type behind `impl Trait` actually implements `Trait`.
605 /// This is mostly checked at the places that specify the opaque type, but we
606 /// check those cases in the `param_env` of that function, which may have
607 /// bounds not on this opaque type:
609 /// type X<T> = impl Clone
610 /// fn f<T: Clone>(t: T) -> X<T> {
614 /// Without this check the above code is incorrectly accepted: we would ICE if
615 /// some tried, for example, to clone an `Option<X<&mut ()>>`.
616 fn check_opaque_meets_bounds<'tcx>(
619 substs: SubstsRef<'tcx>,
621 origin: &hir::OpaqueTyOrigin,
624 // Checked when type checking the function containing them.
625 hir::OpaqueTyOrigin::FnReturn | hir::OpaqueTyOrigin::AsyncFn => return,
626 // Can have different predicates to their defining use
627 hir::OpaqueTyOrigin::Binding | hir::OpaqueTyOrigin::Misc => {}
630 let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
631 let param_env = tcx.param_env(def_id);
633 tcx.infer_ctxt().enter(move |infcx| {
634 let inh = Inherited::new(infcx, def_id);
635 let infcx = &inh.infcx;
636 let opaque_ty = tcx.mk_opaque(def_id.to_def_id(), substs);
638 let misc_cause = traits::ObligationCause::misc(span, hir_id);
640 let (_, opaque_type_map) = inh.register_infer_ok_obligations(
641 infcx.instantiate_opaque_types(def_id, hir_id, param_env, opaque_ty, span),
644 for (def_id, opaque_defn) in opaque_type_map {
646 .at(&misc_cause, param_env)
647 .eq(opaque_defn.concrete_ty, tcx.type_of(def_id).subst(tcx, opaque_defn.substs))
649 Ok(infer_ok) => inh.register_infer_ok_obligations(infer_ok),
650 Err(ty_err) => tcx.sess.delay_span_bug(
651 opaque_defn.definition_span,
653 "could not unify `{}` with revealed type:\n{}",
654 opaque_defn.concrete_ty, ty_err,
660 // Check that all obligations are satisfied by the implementation's
662 if let Err(ref errors) = inh.fulfillment_cx.borrow_mut().select_all_or_error(&infcx) {
663 infcx.report_fulfillment_errors(errors, None, false);
666 // Finally, resolve all regions. This catches wily misuses of
667 // lifetime parameters.
668 let fcx = FnCtxt::new(&inh, param_env, hir_id);
669 fcx.regionck_item(hir_id, span, &[]);
673 pub fn check_item_type<'tcx>(tcx: TyCtxt<'tcx>, it: &'tcx hir::Item<'tcx>) {
675 "check_item_type(it.hir_id={}, it.name={})",
677 tcx.def_path_str(tcx.hir().local_def_id(it.hir_id).to_def_id())
679 let _indenter = indenter();
681 // Consts can play a role in type-checking, so they are included here.
682 hir::ItemKind::Static(..) => {
683 let def_id = tcx.hir().local_def_id(it.hir_id);
684 tcx.ensure().typeck(def_id);
685 maybe_check_static_with_link_section(tcx, def_id, it.span);
686 check_static_inhabited(tcx, def_id, it.span);
688 hir::ItemKind::Const(..) => {
689 tcx.ensure().typeck(tcx.hir().local_def_id(it.hir_id));
691 hir::ItemKind::Enum(ref enum_definition, _) => {
692 check_enum(tcx, it.span, &enum_definition.variants, it.hir_id);
694 hir::ItemKind::Fn(..) => {} // entirely within check_item_body
695 hir::ItemKind::Impl(ref impl_) => {
696 debug!("ItemKind::Impl {} with id {}", it.ident, it.hir_id);
697 let impl_def_id = tcx.hir().local_def_id(it.hir_id);
698 if let Some(impl_trait_ref) = tcx.impl_trait_ref(impl_def_id) {
699 check_impl_items_against_trait(
706 let trait_def_id = impl_trait_ref.def_id;
707 check_on_unimplemented(tcx, trait_def_id, it);
710 hir::ItemKind::Trait(_, _, _, _, ref items) => {
711 let def_id = tcx.hir().local_def_id(it.hir_id);
712 check_on_unimplemented(tcx, def_id.to_def_id(), it);
714 for item in items.iter() {
715 let item = tcx.hir().trait_item(item.id);
717 hir::TraitItemKind::Fn(ref sig, _) => {
718 let abi = sig.header.abi;
719 fn_maybe_err(tcx, item.ident.span, abi);
721 hir::TraitItemKind::Type(.., Some(_default)) => {
722 let item_def_id = tcx.hir().local_def_id(item.hir_id).to_def_id();
723 let assoc_item = tcx.associated_item(item_def_id);
725 InternalSubsts::identity_for_item(tcx, def_id.to_def_id());
726 let _: Result<_, rustc_errors::ErrorReported> = check_type_bounds(
731 ty::TraitRef { def_id: def_id.to_def_id(), substs: trait_substs },
738 hir::ItemKind::Struct(..) => {
739 check_struct(tcx, it.hir_id, it.span);
741 hir::ItemKind::Union(..) => {
742 check_union(tcx, it.hir_id, it.span);
744 hir::ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) => {
745 // HACK(jynelson): trying to infer the type of `impl trait` breaks documenting
746 // `async-std` (and `pub async fn` in general).
747 // Since rustdoc doesn't care about the concrete type behind `impl Trait`, just don't look at it!
748 // See https://github.com/rust-lang/rust/issues/75100
749 if !tcx.sess.opts.actually_rustdoc {
750 let def_id = tcx.hir().local_def_id(it.hir_id);
752 let substs = InternalSubsts::identity_for_item(tcx, def_id.to_def_id());
753 check_opaque(tcx, def_id, substs, it.span, &origin);
756 hir::ItemKind::TyAlias(..) => {
757 let def_id = tcx.hir().local_def_id(it.hir_id);
758 let pty_ty = tcx.type_of(def_id);
759 let generics = tcx.generics_of(def_id);
760 check_type_params_are_used(tcx, &generics, pty_ty);
762 hir::ItemKind::ForeignMod { abi, items } => {
763 check_abi(tcx, it.span, abi);
765 if abi == Abi::RustIntrinsic {
767 let item = tcx.hir().foreign_item(item.id);
768 intrinsic::check_intrinsic_type(tcx, item);
770 } else if abi == Abi::PlatformIntrinsic {
772 let item = tcx.hir().foreign_item(item.id);
773 intrinsic::check_platform_intrinsic_type(tcx, item);
777 let def_id = tcx.hir().local_def_id(item.id.hir_id);
778 let generics = tcx.generics_of(def_id);
779 let own_counts = generics.own_counts();
780 if generics.params.len() - own_counts.lifetimes != 0 {
781 let (kinds, kinds_pl, egs) = match (own_counts.types, own_counts.consts) {
782 (_, 0) => ("type", "types", Some("u32")),
783 // We don't specify an example value, because we can't generate
784 // a valid value for any type.
785 (0, _) => ("const", "consts", None),
786 _ => ("type or const", "types or consts", None),
792 "foreign items may not have {} parameters",
795 .span_label(item.span, &format!("can't have {} parameters", kinds))
797 // FIXME: once we start storing spans for type arguments, turn this
798 // into a suggestion.
800 "replace the {} parameters with concrete {}{}",
803 egs.map(|egs| format!(" like `{}`", egs)).unwrap_or_default(),
809 let item = tcx.hir().foreign_item(item.id);
811 hir::ForeignItemKind::Fn(ref fn_decl, _, _) => {
812 require_c_abi_if_c_variadic(tcx, fn_decl, abi, item.span);
814 hir::ForeignItemKind::Static(..) => {
815 check_static_inhabited(tcx, def_id, item.span);
822 _ => { /* nothing to do */ }
826 pub(super) fn check_on_unimplemented(tcx: TyCtxt<'_>, trait_def_id: DefId, item: &hir::Item<'_>) {
827 let item_def_id = tcx.hir().local_def_id(item.hir_id);
828 // an error would be reported if this fails.
829 let _ = traits::OnUnimplementedDirective::of_item(tcx, trait_def_id, item_def_id.to_def_id());
832 pub(super) fn check_specialization_validity<'tcx>(
834 trait_def: &ty::TraitDef,
835 trait_item: &ty::AssocItem,
837 impl_item: &hir::ImplItem<'_>,
839 let kind = match impl_item.kind {
840 hir::ImplItemKind::Const(..) => ty::AssocKind::Const,
841 hir::ImplItemKind::Fn(..) => ty::AssocKind::Fn,
842 hir::ImplItemKind::TyAlias(_) => ty::AssocKind::Type,
845 let ancestors = match trait_def.ancestors(tcx, impl_id) {
846 Ok(ancestors) => ancestors,
849 let mut ancestor_impls = ancestors.skip(1).filter_map(|parent| {
850 if parent.is_from_trait() {
853 Some((parent, parent.item(tcx, trait_item.ident, kind, trait_def.def_id)))
857 let opt_result = ancestor_impls.find_map(|(parent_impl, parent_item)| {
859 // Parent impl exists, and contains the parent item we're trying to specialize, but
860 // doesn't mark it `default`.
861 Some(parent_item) if traits::impl_item_is_final(tcx, &parent_item) => {
862 Some(Err(parent_impl.def_id()))
865 // Parent impl contains item and makes it specializable.
866 Some(_) => Some(Ok(())),
868 // Parent impl doesn't mention the item. This means it's inherited from the
869 // grandparent. In that case, if parent is a `default impl`, inherited items use the
870 // "defaultness" from the grandparent, else they are final.
872 if tcx.impl_defaultness(parent_impl.def_id()).is_default() {
875 Some(Err(parent_impl.def_id()))
881 // If `opt_result` is `None`, we have only encountered `default impl`s that don't contain the
882 // item. This is allowed, the item isn't actually getting specialized here.
883 let result = opt_result.unwrap_or(Ok(()));
885 if let Err(parent_impl) = result {
886 report_forbidden_specialization(tcx, impl_item, parent_impl);
890 pub(super) fn check_impl_items_against_trait<'tcx>(
892 full_impl_span: Span,
894 impl_trait_ref: ty::TraitRef<'tcx>,
895 impl_item_refs: &[hir::ImplItemRef<'_>],
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);
924 let impl_items = impl_item_refs.iter().map(|iiref| tcx.hir().impl_item(iiref.id));
925 let associated_items = tcx.associated_items(impl_trait_ref.def_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 ty_impl_item = tcx.associated_item(tcx.hir().local_def_id(impl_item.hir_id));
933 associated_items.filter_by_name(tcx, ty_impl_item.ident, impl_trait_ref.def_id);
935 let (compatible_kind, ty_trait_item) = if let Some(ty_trait_item) = items.next() {
936 let is_compatible = |ty: &&ty::AssocItem| match (ty.kind, &impl_item.kind) {
937 (ty::AssocKind::Const, hir::ImplItemKind::Const(..)) => true,
938 (ty::AssocKind::Fn, hir::ImplItemKind::Fn(..)) => true,
939 (ty::AssocKind::Type, hir::ImplItemKind::TyAlias(..)) => true,
943 // If we don't have a compatible item, we'll use the first one whose name matches
944 // to report an error.
945 let mut compatible_kind = is_compatible(&ty_trait_item);
946 let mut trait_item = ty_trait_item;
948 if !compatible_kind {
949 if let Some(ty_trait_item) = items.find(is_compatible) {
950 compatible_kind = true;
951 trait_item = ty_trait_item;
955 (compatible_kind, trait_item)
961 match impl_item.kind {
962 hir::ImplItemKind::Const(..) => {
963 // Find associated const definition.
972 hir::ImplItemKind::Fn(..) => {
973 let opt_trait_span = tcx.hir().span_if_local(ty_trait_item.def_id);
983 hir::ImplItemKind::TyAlias(_) => {
984 let opt_trait_span = tcx.hir().span_if_local(ty_trait_item.def_id);
996 check_specialization_validity(
1000 impl_id.to_def_id(),
1004 report_mismatch_error(
1006 ty_trait_item.def_id,
1014 if let Ok(ancestors) = trait_def.ancestors(tcx, impl_id.to_def_id()) {
1015 let impl_span = tcx.sess.source_map().guess_head_span(full_impl_span);
1017 // Check for missing items from trait
1018 let mut missing_items = Vec::new();
1019 for trait_item in tcx.associated_items(impl_trait_ref.def_id).in_definition_order() {
1020 let is_implemented = ancestors
1021 .leaf_def(tcx, trait_item.ident, trait_item.kind)
1022 .map(|node_item| !node_item.defining_node.is_from_trait())
1025 if !is_implemented && tcx.impl_defaultness(impl_id).is_final() {
1026 if !trait_item.defaultness.has_value() {
1027 missing_items.push(*trait_item);
1032 if !missing_items.is_empty() {
1033 missing_items_err(tcx, impl_span, &missing_items, full_impl_span);
1040 fn report_mismatch_error<'tcx>(
1042 trait_item_def_id: DefId,
1043 impl_trait_ref: ty::TraitRef<'tcx>,
1044 impl_item: &hir::ImplItem<'_>,
1045 ty_impl_item: &ty::AssocItem,
1047 let mut err = match impl_item.kind {
1048 hir::ImplItemKind::Const(..) => {
1049 // Find associated const definition.
1054 "item `{}` is an associated const, which doesn't match its trait `{}`",
1056 impl_trait_ref.print_only_trait_path()
1060 hir::ImplItemKind::Fn(..) => {
1065 "item `{}` is an associated method, which doesn't match its trait `{}`",
1067 impl_trait_ref.print_only_trait_path()
1071 hir::ImplItemKind::TyAlias(_) => {
1076 "item `{}` is an associated type, which doesn't match its trait `{}`",
1078 impl_trait_ref.print_only_trait_path()
1083 err.span_label(impl_item.span, "does not match trait");
1084 if let Some(trait_span) = tcx.hir().span_if_local(trait_item_def_id) {
1085 err.span_label(trait_span, "item in trait");
1090 /// Checks whether a type can be represented in memory. In particular, it
1091 /// identifies types that contain themselves without indirection through a
1092 /// pointer, which would mean their size is unbounded.
1093 pub(super) fn check_representable(tcx: TyCtxt<'_>, sp: Span, item_def_id: LocalDefId) -> bool {
1094 let rty = tcx.type_of(item_def_id);
1096 // Check that it is possible to represent this type. This call identifies
1097 // (1) types that contain themselves and (2) types that contain a different
1098 // recursive type. It is only necessary to throw an error on those that
1099 // contain themselves. For case 2, there must be an inner type that will be
1100 // caught by case 1.
1101 match rty.is_representable(tcx, sp) {
1102 Representability::SelfRecursive(spans) => {
1103 recursive_type_with_infinite_size_error(tcx, item_def_id.to_def_id(), spans);
1106 Representability::Representable | Representability::ContainsRecursive => (),
1111 pub fn check_simd(tcx: TyCtxt<'_>, sp: Span, def_id: LocalDefId) {
1112 let t = tcx.type_of(def_id);
1113 if let ty::Adt(def, substs) = t.kind() {
1114 if def.is_struct() {
1115 let fields = &def.non_enum_variant().fields;
1116 if fields.is_empty() {
1117 struct_span_err!(tcx.sess, sp, E0075, "SIMD vector cannot be empty").emit();
1120 let e = fields[0].ty(tcx, substs);
1121 if !fields.iter().all(|f| f.ty(tcx, substs) == e) {
1122 struct_span_err!(tcx.sess, sp, E0076, "SIMD vector should be homogeneous")
1123 .span_label(sp, "SIMD elements must have the same type")
1128 ty::Param(_) => { /* struct<T>(T, T, T, T) is ok */ }
1129 _ if e.is_machine() => { /* struct(u8, u8, u8, u8) is ok */ }
1130 ty::Array(ty, _c) if ty.is_machine() => { /* struct([f32; 4]) */ }
1136 "SIMD vector element type should be a \
1137 primitive scalar (integer/float/pointer) type"
1147 pub(super) fn check_packed(tcx: TyCtxt<'_>, sp: Span, def: &ty::AdtDef) {
1148 let repr = def.repr;
1150 for attr in tcx.get_attrs(def.did).iter() {
1151 for r in attr::find_repr_attrs(&tcx.sess, attr) {
1152 if let attr::ReprPacked(pack) = r {
1153 if let Some(repr_pack) = repr.pack {
1154 if pack as u64 != repr_pack.bytes() {
1159 "type has conflicting packed representation hints"
1167 if repr.align.is_some() {
1172 "type has conflicting packed and align representation hints"
1176 if let Some(def_spans) = check_packed_inner(tcx, def.did, &mut vec![]) {
1177 let mut err = struct_span_err!(
1181 "packed type cannot transitively contain a `#[repr(align)]` type"
1185 tcx.def_span(def_spans[0].0),
1187 "`{}` has a `#[repr(align)]` attribute",
1188 tcx.item_name(def_spans[0].0)
1192 if def_spans.len() > 2 {
1193 let mut first = true;
1194 for (adt_def, span) in def_spans.iter().skip(1).rev() {
1195 let ident = tcx.item_name(*adt_def);
1200 "`{}` contains a field of type `{}`",
1201 tcx.type_of(def.did),
1205 format!("...which contains a field of type `{}`", ident)
1218 pub(super) fn check_packed_inner(
1221 stack: &mut Vec<DefId>,
1222 ) -> Option<Vec<(DefId, Span)>> {
1223 if let ty::Adt(def, substs) = tcx.type_of(def_id).kind() {
1224 if def.is_struct() || def.is_union() {
1225 if def.repr.align.is_some() {
1226 return Some(vec![(def.did, DUMMY_SP)]);
1230 for field in &def.non_enum_variant().fields {
1231 if let ty::Adt(def, _) = field.ty(tcx, substs).kind() {
1232 if !stack.contains(&def.did) {
1233 if let Some(mut defs) = check_packed_inner(tcx, def.did, stack) {
1234 defs.push((def.did, field.ident.span));
1247 pub(super) fn check_transparent<'tcx>(tcx: TyCtxt<'tcx>, sp: Span, adt: &'tcx ty::AdtDef) {
1248 if !adt.repr.transparent() {
1251 let sp = tcx.sess.source_map().guess_head_span(sp);
1253 if adt.is_union() && !tcx.features().transparent_unions {
1255 &tcx.sess.parse_sess,
1256 sym::transparent_unions,
1258 "transparent unions are unstable",
1263 if adt.variants.len() != 1 {
1264 bad_variant_count(tcx, adt, sp, adt.did);
1265 if adt.variants.is_empty() {
1266 // Don't bother checking the fields. No variants (and thus no fields) exist.
1271 // For each field, figure out if it's known to be a ZST and align(1)
1272 let field_infos = adt.all_fields().map(|field| {
1273 let ty = field.ty(tcx, InternalSubsts::identity_for_item(tcx, field.did));
1274 let param_env = tcx.param_env(field.did);
1275 let layout = tcx.layout_of(param_env.and(ty));
1276 // We are currently checking the type this field came from, so it must be local
1277 let span = tcx.hir().span_if_local(field.did).unwrap();
1278 let zst = layout.map_or(false, |layout| layout.is_zst());
1279 let align1 = layout.map_or(false, |layout| layout.align.abi.bytes() == 1);
1283 let non_zst_fields =
1284 field_infos.clone().filter_map(|(span, zst, _align1)| if !zst { Some(span) } else { None });
1285 let non_zst_count = non_zst_fields.clone().count();
1286 if non_zst_count != 1 {
1287 bad_non_zero_sized_fields(tcx, adt, non_zst_count, non_zst_fields, sp);
1289 for (span, zst, align1) in field_infos {
1295 "zero-sized field in transparent {} has alignment larger than 1",
1298 .span_label(span, "has alignment larger than 1")
1304 #[allow(trivial_numeric_casts)]
1305 pub fn check_enum<'tcx>(
1308 vs: &'tcx [hir::Variant<'tcx>],
1311 let def_id = tcx.hir().local_def_id(id);
1312 let def = tcx.adt_def(def_id);
1313 def.destructor(tcx); // force the destructor to be evaluated
1316 let attributes = tcx.get_attrs(def_id.to_def_id());
1317 if let Some(attr) = tcx.sess.find_by_name(&attributes, sym::repr) {
1322 "unsupported representation for zero-variant enum"
1324 .span_label(sp, "zero-variant enum")
1329 let repr_type_ty = def.repr.discr_type().to_ty(tcx);
1330 if repr_type_ty == tcx.types.i128 || repr_type_ty == tcx.types.u128 {
1331 if !tcx.features().repr128 {
1333 &tcx.sess.parse_sess,
1336 "repr with 128-bit type is unstable",
1343 if let Some(ref e) = v.disr_expr {
1344 tcx.ensure().typeck(tcx.hir().local_def_id(e.hir_id));
1348 if tcx.adt_def(def_id).repr.int.is_none() && tcx.features().arbitrary_enum_discriminant {
1349 let is_unit = |var: &hir::Variant<'_>| matches!(var.data, hir::VariantData::Unit(..));
1351 let has_disr = |var: &hir::Variant<'_>| var.disr_expr.is_some();
1352 let has_non_units = vs.iter().any(|var| !is_unit(var));
1353 let disr_units = vs.iter().any(|var| is_unit(&var) && has_disr(&var));
1354 let disr_non_unit = vs.iter().any(|var| !is_unit(&var) && has_disr(&var));
1356 if disr_non_unit || (disr_units && has_non_units) {
1358 struct_span_err!(tcx.sess, sp, E0732, "`#[repr(inttype)]` must be specified");
1363 let mut disr_vals: Vec<Discr<'tcx>> = Vec::with_capacity(vs.len());
1364 for ((_, discr), v) in def.discriminants(tcx).zip(vs) {
1365 // Check for duplicate discriminant values
1366 if let Some(i) = disr_vals.iter().position(|&x| x.val == discr.val) {
1367 let variant_did = def.variants[VariantIdx::new(i)].def_id;
1368 let variant_i_hir_id = tcx.hir().local_def_id_to_hir_id(variant_did.expect_local());
1369 let variant_i = tcx.hir().expect_variant(variant_i_hir_id);
1370 let i_span = match variant_i.disr_expr {
1371 Some(ref expr) => tcx.hir().span(expr.hir_id),
1372 None => tcx.hir().span(variant_i_hir_id),
1374 let span = match v.disr_expr {
1375 Some(ref expr) => tcx.hir().span(expr.hir_id),
1382 "discriminant value `{}` already exists",
1385 .span_label(i_span, format!("first use of `{}`", disr_vals[i]))
1386 .span_label(span, format!("enum already has `{}`", disr_vals[i]))
1389 disr_vals.push(discr);
1392 check_representable(tcx, sp, def_id);
1393 check_transparent(tcx, sp, def);
1396 pub(super) fn check_type_params_are_used<'tcx>(
1398 generics: &ty::Generics,
1401 debug!("check_type_params_are_used(generics={:?}, ty={:?})", generics, ty);
1403 assert_eq!(generics.parent, None);
1405 if generics.own_counts().types == 0 {
1409 let mut params_used = BitSet::new_empty(generics.params.len());
1411 if ty.references_error() {
1412 // If there is already another error, do not emit
1413 // an error for not using a type parameter.
1414 assert!(tcx.sess.has_errors());
1418 for leaf in ty.walk() {
1419 if let GenericArgKind::Type(leaf_ty) = leaf.unpack() {
1420 if let ty::Param(param) = leaf_ty.kind() {
1421 debug!("found use of ty param {:?}", param);
1422 params_used.insert(param.index);
1427 for param in &generics.params {
1428 if !params_used.contains(param.index) {
1429 if let ty::GenericParamDefKind::Type { .. } = param.kind {
1430 let span = tcx.def_span(param.def_id);
1435 "type parameter `{}` is unused",
1438 .span_label(span, "unused type parameter")
1445 pub(super) fn check_mod_item_types(tcx: TyCtxt<'_>, module_def_id: LocalDefId) {
1446 tcx.hir().visit_item_likes_in_module(module_def_id, &mut CheckItemTypesVisitor { tcx });
1449 pub(super) fn check_item_well_formed(tcx: TyCtxt<'_>, def_id: LocalDefId) {
1450 wfcheck::check_item_well_formed(tcx, def_id);
1453 pub(super) fn check_trait_item_well_formed(tcx: TyCtxt<'_>, def_id: LocalDefId) {
1454 wfcheck::check_trait_item(tcx, def_id);
1457 pub(super) fn check_impl_item_well_formed(tcx: TyCtxt<'_>, def_id: LocalDefId) {
1458 wfcheck::check_impl_item(tcx, def_id);
1461 fn async_opaque_type_cycle_error(tcx: TyCtxt<'tcx>, span: Span) {
1462 struct_span_err!(tcx.sess, span, E0733, "recursion in an `async fn` requires boxing")
1463 .span_label(span, "recursive `async fn`")
1464 .note("a recursive `async fn` must be rewritten to return a boxed `dyn Future`")
1468 /// Emit an error for recursive opaque types.
1470 /// If this is a return `impl Trait`, find the item's return expressions and point at them. For
1471 /// direct recursion this is enough, but for indirect recursion also point at the last intermediary
1474 /// If all the return expressions evaluate to `!`, then we explain that the error will go away
1475 /// after changing it. This can happen when a user uses `panic!()` or similar as a placeholder.
1476 fn opaque_type_cycle_error(tcx: TyCtxt<'tcx>, def_id: LocalDefId, span: Span) {
1477 let mut err = struct_span_err!(tcx.sess, span, E0720, "cannot resolve opaque type");
1479 let mut label = false;
1480 if let Some((hir_id, visitor)) = get_owner_return_paths(tcx, def_id) {
1481 let typeck_results = tcx.typeck(tcx.hir().local_def_id(hir_id));
1485 .filter_map(|expr| typeck_results.node_type_opt(expr.hir_id))
1486 .all(|ty| matches!(ty.kind(), ty::Never))
1491 .filter(|expr| typeck_results.node_type_opt(expr.hir_id).is_some())
1492 .map(|expr| expr.span)
1493 .collect::<Vec<Span>>();
1494 let span_len = spans.len();
1496 err.span_label(spans[0], "this returned value is of `!` type");
1498 let mut multispan: MultiSpan = spans.clone().into();
1501 .push_span_label(span, "this returned value is of `!` type".to_string());
1503 err.span_note(multispan, "these returned values have a concrete \"never\" type");
1505 err.help("this error will resolve once the item's body returns a concrete type");
1507 let mut seen = FxHashSet::default();
1509 err.span_label(span, "recursive opaque type");
1511 for (sp, ty) in visitor
1514 .filter_map(|e| typeck_results.node_type_opt(e.hir_id).map(|t| (e.span, t)))
1515 .filter(|(_, ty)| !matches!(ty.kind(), ty::Never))
1517 struct VisitTypes(Vec<DefId>);
1518 impl<'tcx> ty::fold::TypeVisitor<'tcx> for VisitTypes {
1519 fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
1521 ty::Opaque(def, _) => {
1523 ControlFlow::CONTINUE
1525 _ => t.super_visit_with(self),
1529 let mut visitor = VisitTypes(vec![]);
1530 ty.visit_with(&mut visitor);
1531 for def_id in visitor.0 {
1532 let ty_span = tcx.def_span(def_id);
1533 if !seen.contains(&ty_span) {
1534 err.span_label(ty_span, &format!("returning this opaque type `{}`", ty));
1535 seen.insert(ty_span);
1537 err.span_label(sp, &format!("returning here with type `{}`", ty));
1543 err.span_label(span, "cannot resolve opaque type");