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};
10 use rustc_hir::intravisit::Visitor;
11 use rustc_hir::lang_items::LangItem;
12 use rustc_hir::{def::Res, ItemKind, Node, PathSegment};
13 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
14 use rustc_infer::infer::{RegionVariableOrigin, TyCtxtInferExt};
15 use rustc_middle::hir::nested_filter;
16 use rustc_middle::ty::fold::TypeFoldable;
17 use rustc_middle::ty::layout::MAX_SIMD_LANES;
18 use rustc_middle::ty::subst::GenericArgKind;
19 use rustc_middle::ty::util::{Discr, IntTypeExt};
20 use rustc_middle::ty::{self, ParamEnv, RegionKind, Ty, TyCtxt};
21 use rustc_session::lint::builtin::{UNINHABITED_STATIC, UNSUPPORTED_CALLING_CONVENTIONS};
22 use rustc_span::symbol::sym;
23 use rustc_span::{self, MultiSpan, Span};
24 use rustc_target::spec::abi::Abi;
25 use rustc_trait_selection::traits;
26 use rustc_trait_selection::traits::error_reporting::InferCtxtExt as _;
27 use rustc_ty_utils::representability::{self, Representability};
30 use std::ops::ControlFlow;
32 pub fn check_wf_new(tcx: TyCtxt<'_>) {
33 let visit = wfcheck::CheckTypeWellFormedVisitor::new(tcx);
34 tcx.hir().par_visit_all_item_likes(&visit);
37 pub(super) fn check_abi(tcx: TyCtxt<'_>, hir_id: hir::HirId, span: Span, abi: Abi) {
38 match tcx.sess.target.is_abi_supported(abi) {
40 Some(false) => struct_span_err!(
44 "`{}` is not a supported ABI for the current target",
49 tcx.struct_span_lint_hir(UNSUPPORTED_CALLING_CONVENTIONS, hir_id, span, |lint| {
50 lint.build("use of calling convention not supported on this target").emit()
55 // This ABI is only allowed on function pointers
56 if abi == Abi::CCmseNonSecureCall {
61 "the `\"C-cmse-nonsecure-call\"` ABI is only allowed on function pointers"
67 /// Helper used for fns and closures. Does the grungy work of checking a function
68 /// body and returns the function context used for that purpose, since in the case of a fn item
69 /// there is still a bit more to do.
72 /// * inherited: other fields inherited from the enclosing fn (if any)
73 #[instrument(skip(inherited, body), level = "debug")]
74 pub(super) fn check_fn<'a, 'tcx>(
75 inherited: &'a Inherited<'a, 'tcx>,
76 param_env: ty::ParamEnv<'tcx>,
77 fn_sig: ty::FnSig<'tcx>,
78 decl: &'tcx hir::FnDecl<'tcx>,
80 body: &'tcx hir::Body<'tcx>,
81 can_be_generator: Option<hir::Movability>,
82 return_type_pre_known: bool,
83 ) -> (FnCtxt<'a, 'tcx>, Option<GeneratorTypes<'tcx>>) {
84 // Create the function context. This is either derived from scratch or,
85 // in the case of closures, based on the outer context.
86 let mut fcx = FnCtxt::new(inherited, param_env, body.value.hir_id);
87 fcx.ps.set(UnsafetyState::function(fn_sig.unsafety, fn_id));
88 fcx.return_type_pre_known = return_type_pre_known;
94 let declared_ret_ty = fn_sig.output();
96 fcx.ret_coercion = Some(RefCell::new(CoerceMany::new(declared_ret_ty)));
97 fcx.ret_type_span = Some(decl.output.span());
99 let span = body.value.span;
101 fn_maybe_err(tcx, span, fn_sig.abi);
103 if fn_sig.abi == Abi::RustCall {
104 let expected_args = if let ImplicitSelfKind::None = decl.implicit_self { 1 } else { 2 };
107 let item = match tcx.hir().get(fn_id) {
108 Node::Item(hir::Item { kind: ItemKind::Fn(header, ..), .. }) => Some(header),
109 Node::ImplItem(hir::ImplItem {
110 kind: hir::ImplItemKind::Fn(header, ..), ..
112 Node::TraitItem(hir::TraitItem {
113 kind: hir::TraitItemKind::Fn(header, ..),
116 // Closures are RustCall, but they tuple their arguments, so shouldn't be checked
117 Node::Expr(hir::Expr { kind: hir::ExprKind::Closure(..), .. }) => None,
118 node => bug!("Item being checked wasn't a function/closure: {:?}", node),
121 if let Some(header) = item {
122 tcx.sess.span_err(header.span, "functions with the \"rust-call\" ABI must take a single non-self argument that is a tuple")
126 if fn_sig.inputs().len() != expected_args {
129 // FIXME(CraftSpider) Add a check on parameter expansion, so we don't just make the ICE happen later on
130 // This will probably require wide-scale changes to support a TupleKind obligation
131 // We can't resolve this without knowing the type of the param
132 if !matches!(fn_sig.inputs()[expected_args - 1].kind(), ty::Tuple(_) | ty::Param(_)) {
138 if body.generator_kind.is_some() && can_be_generator.is_some() {
140 .next_ty_var(TypeVariableOrigin { kind: TypeVariableOriginKind::TypeInference, span });
141 fcx.require_type_is_sized(yield_ty, span, traits::SizedYieldType);
143 // Resume type defaults to `()` if the generator has no argument.
144 let resume_ty = fn_sig.inputs().get(0).copied().unwrap_or_else(|| tcx.mk_unit());
146 fcx.resume_yield_tys = Some((resume_ty, yield_ty));
149 GatherLocalsVisitor::new(&fcx).visit_body(body);
151 // C-variadic fns also have a `VaList` input that's not listed in `fn_sig`
152 // (as it's created inside the body itself, not passed in from outside).
153 let maybe_va_list = if fn_sig.c_variadic {
154 let span = body.params.last().unwrap().span;
155 let va_list_did = tcx.require_lang_item(LangItem::VaList, Some(span));
156 let region = fcx.next_region_var(RegionVariableOrigin::MiscVariable(span));
158 Some(tcx.type_of(va_list_did).subst(tcx, &[region.into()]))
163 // Add formal parameters.
164 let inputs_hir = hir.fn_decl_by_hir_id(fn_id).map(|decl| &decl.inputs);
165 let inputs_fn = fn_sig.inputs().iter().copied();
166 for (idx, (param_ty, param)) in inputs_fn.chain(maybe_va_list).zip(body.params).enumerate() {
167 // Check the pattern.
168 let ty_span = try { inputs_hir?.get(idx)?.span };
169 fcx.check_pat_top(¶m.pat, param_ty, ty_span, false);
171 // Check that argument is Sized.
172 // The check for a non-trivial pattern is a hack to avoid duplicate warnings
173 // for simple cases like `fn foo(x: Trait)`,
174 // where we would error once on the parameter as a whole, and once on the binding `x`.
175 if param.pat.simple_ident().is_none() && !tcx.features().unsized_fn_params {
176 fcx.require_type_is_sized(param_ty, param.pat.span, traits::SizedArgumentType(ty_span));
179 fcx.write_ty(param.hir_id, param_ty);
182 inherited.typeck_results.borrow_mut().liberated_fn_sigs_mut().insert(fn_id, fn_sig);
184 fcx.in_tail_expr = true;
185 if let ty::Dynamic(..) = declared_ret_ty.kind() {
186 // FIXME: We need to verify that the return type is `Sized` after the return expression has
187 // been evaluated so that we have types available for all the nodes being returned, but that
188 // requires the coerced evaluated type to be stored. Moving `check_return_expr` before this
189 // causes unsized errors caused by the `declared_ret_ty` to point at the return expression,
190 // while keeping the current ordering we will ignore the tail expression's type because we
191 // don't know it yet. We can't do `check_expr_kind` while keeping `check_return_expr`
192 // because we will trigger "unreachable expression" lints unconditionally.
193 // Because of all of this, we perform a crude check to know whether the simplest `!Sized`
194 // case that a newcomer might make, returning a bare trait, and in that case we populate
195 // the tail expression's type so that the suggestion will be correct, but ignore all other
197 fcx.check_expr(&body.value);
198 fcx.require_type_is_sized(declared_ret_ty, decl.output.span(), traits::SizedReturnType);
200 fcx.require_type_is_sized(declared_ret_ty, decl.output.span(), traits::SizedReturnType);
201 fcx.check_return_expr(&body.value, false);
203 fcx.in_tail_expr = false;
205 // We insert the deferred_generator_interiors entry after visiting the body.
206 // This ensures that all nested generators appear before the entry of this generator.
207 // resolve_generator_interiors relies on this property.
208 let gen_ty = if let (Some(_), Some(gen_kind)) = (can_be_generator, body.generator_kind) {
210 .next_ty_var(TypeVariableOrigin { kind: TypeVariableOriginKind::MiscVariable, span });
211 fcx.deferred_generator_interiors.borrow_mut().push((body.id(), interior, gen_kind));
213 let (resume_ty, yield_ty) = fcx.resume_yield_tys.unwrap();
214 Some(GeneratorTypes {
218 movability: can_be_generator.unwrap(),
224 // Finalize the return check by taking the LUB of the return types
225 // we saw and assigning it to the expected return type. This isn't
226 // really expected to fail, since the coercions would have failed
227 // earlier when trying to find a LUB.
228 let coercion = fcx.ret_coercion.take().unwrap().into_inner();
229 let mut actual_return_ty = coercion.complete(&fcx);
230 debug!("actual_return_ty = {:?}", actual_return_ty);
231 if let ty::Dynamic(..) = declared_ret_ty.kind() {
232 // We have special-cased the case where the function is declared
233 // `-> dyn Foo` and we don't actually relate it to the
234 // `fcx.ret_coercion`, so just substitute a type variable.
236 fcx.next_ty_var(TypeVariableOrigin { kind: TypeVariableOriginKind::DynReturnFn, span });
237 debug!("actual_return_ty replaced with {:?}", actual_return_ty);
239 fcx.demand_suptype(span, declared_ret_ty, actual_return_ty);
241 // Check that a function marked as `#[panic_handler]` has signature `fn(&PanicInfo) -> !`
242 if let Some(panic_impl_did) = tcx.lang_items().panic_impl() {
243 if panic_impl_did == hir.local_def_id(fn_id).to_def_id() {
244 if let Some(panic_info_did) = tcx.lang_items().panic_info() {
245 if *declared_ret_ty.kind() != ty::Never {
246 sess.span_err(decl.output.span(), "return type should be `!`");
249 let inputs = fn_sig.inputs();
250 let span = hir.span(fn_id);
251 if inputs.len() == 1 {
252 let arg_is_panic_info = match *inputs[0].kind() {
253 ty::Ref(region, ty, mutbl) => match *ty.kind() {
254 ty::Adt(ref adt, _) => {
255 adt.did == panic_info_did
256 && mutbl == hir::Mutability::Not
257 && *region != RegionKind::ReStatic
264 if !arg_is_panic_info {
265 sess.span_err(decl.inputs[0].span, "argument should be `&PanicInfo`");
268 if let Node::Item(item) = hir.get(fn_id) {
269 if let ItemKind::Fn(_, ref generics, _) = item.kind {
270 if !generics.params.is_empty() {
271 sess.span_err(span, "should have no type parameters");
276 let span = sess.source_map().guess_head_span(span);
277 sess.span_err(span, "function should have one argument");
280 sess.err("language item required, but not found: `panic_info`");
285 // Check that a function marked as `#[alloc_error_handler]` has signature `fn(Layout) -> !`
286 if let Some(alloc_error_handler_did) = tcx.lang_items().oom() {
287 if alloc_error_handler_did == hir.local_def_id(fn_id).to_def_id() {
288 if let Some(alloc_layout_did) = tcx.lang_items().alloc_layout() {
289 if *declared_ret_ty.kind() != ty::Never {
290 sess.span_err(decl.output.span(), "return type should be `!`");
293 let inputs = fn_sig.inputs();
294 let span = hir.span(fn_id);
295 if inputs.len() == 1 {
296 let arg_is_alloc_layout = match inputs[0].kind() {
297 ty::Adt(ref adt, _) => adt.did == alloc_layout_did,
301 if !arg_is_alloc_layout {
302 sess.span_err(decl.inputs[0].span, "argument should be `Layout`");
305 if let Node::Item(item) = hir.get(fn_id) {
306 if let ItemKind::Fn(_, ref generics, _) = item.kind {
307 if !generics.params.is_empty() {
310 "`#[alloc_error_handler]` function should have no type \
317 let span = sess.source_map().guess_head_span(span);
318 sess.span_err(span, "function should have one argument");
321 sess.err("language item required, but not found: `alloc_layout`");
329 fn check_struct(tcx: TyCtxt<'_>, def_id: LocalDefId, span: Span) {
330 let def = tcx.adt_def(def_id);
331 def.destructor(tcx); // force the destructor to be evaluated
332 check_representable(tcx, span, def_id);
335 check_simd(tcx, span, def_id);
338 check_transparent(tcx, span, def);
339 check_packed(tcx, span, def);
342 fn check_union(tcx: TyCtxt<'_>, def_id: LocalDefId, span: Span) {
343 let def = tcx.adt_def(def_id);
344 def.destructor(tcx); // force the destructor to be evaluated
345 check_representable(tcx, span, def_id);
346 check_transparent(tcx, span, def);
347 check_union_fields(tcx, span, def_id);
348 check_packed(tcx, span, def);
351 /// Check that the fields of the `union` do not need dropping.
352 fn check_union_fields(tcx: TyCtxt<'_>, span: Span, item_def_id: LocalDefId) -> bool {
353 let item_type = tcx.type_of(item_def_id);
354 if let ty::Adt(def, substs) = item_type.kind() {
355 assert!(def.is_union());
356 let fields = &def.non_enum_variant().fields;
357 let param_env = tcx.param_env(item_def_id);
358 for field in fields {
359 let field_ty = field.ty(tcx, substs);
360 if field_ty.needs_drop(tcx, param_env) {
361 let (field_span, ty_span) = match tcx.hir().get_if_local(field.did) {
362 // We are currently checking the type this field came from, so it must be local.
363 Some(Node::Field(field)) => (field.span, field.ty.span),
364 _ => unreachable!("mir field has to correspond to hir field"),
370 "unions may not contain fields that need dropping"
372 .multipart_suggestion_verbose(
373 "wrap the type with `std::mem::ManuallyDrop` and ensure it is manually dropped",
375 (ty_span.shrink_to_lo(), format!("std::mem::ManuallyDrop<")),
376 (ty_span.shrink_to_hi(), ">".into()),
378 Applicability::MaybeIncorrect,
385 span_bug!(span, "unions must be ty::Adt, but got {:?}", item_type.kind());
390 /// Check that a `static` is inhabited.
391 fn check_static_inhabited<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId, span: Span) {
392 // Make sure statics are inhabited.
393 // Other parts of the compiler assume that there are no uninhabited places. In principle it
394 // would be enough to check this for `extern` statics, as statics with an initializer will
395 // have UB during initialization if they are uninhabited, but there also seems to be no good
396 // reason to allow any statics to be uninhabited.
397 let ty = tcx.type_of(def_id);
398 let layout = match tcx.layout_of(ParamEnv::reveal_all().and(ty)) {
401 // Generic statics are rejected, but we still reach this case.
402 tcx.sess.delay_span_bug(span, "generic static must be rejected");
406 if layout.abi.is_uninhabited() {
407 tcx.struct_span_lint_hir(
409 tcx.hir().local_def_id_to_hir_id(def_id),
412 lint.build("static of uninhabited type")
413 .note("uninhabited statics cannot be initialized, and any access would be an immediate error")
420 /// Checks that an opaque type does not contain cycles and does not use `Self` or `T::Foo`
421 /// projections that would result in "inheriting lifetimes".
422 pub(super) fn check_opaque<'tcx>(
425 substs: SubstsRef<'tcx>,
427 origin: &hir::OpaqueTyOrigin,
429 check_opaque_for_inheriting_lifetimes(tcx, def_id, span);
430 if tcx.type_of(def_id).references_error() {
433 if check_opaque_for_cycles(tcx, def_id, substs, span, origin).is_err() {
436 check_opaque_meets_bounds(tcx, def_id, substs, span, origin);
439 /// Checks that an opaque type does not use `Self` or `T::Foo` projections that would result
440 /// in "inheriting lifetimes".
441 #[instrument(level = "debug", skip(tcx, span))]
442 pub(super) fn check_opaque_for_inheriting_lifetimes<'tcx>(
447 let item = tcx.hir().expect_item(def_id);
448 debug!(?item, ?span);
450 struct FoundParentLifetime;
451 struct FindParentLifetimeVisitor<'tcx>(&'tcx ty::Generics);
452 impl<'tcx> ty::fold::TypeVisitor<'tcx> for FindParentLifetimeVisitor<'tcx> {
453 type BreakTy = FoundParentLifetime;
455 fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> {
456 debug!("FindParentLifetimeVisitor: r={:?}", r);
457 if let RegionKind::ReEarlyBound(ty::EarlyBoundRegion { index, .. }) = r {
458 if *index < self.0.parent_count as u32 {
459 return ControlFlow::Break(FoundParentLifetime);
461 return ControlFlow::CONTINUE;
465 r.super_visit_with(self)
468 fn visit_const(&mut self, c: &'tcx ty::Const<'tcx>) -> ControlFlow<Self::BreakTy> {
469 if let ty::ConstKind::Unevaluated(..) = c.val {
470 // FIXME(#72219) We currently don't detect lifetimes within substs
471 // which would violate this check. Even though the particular substitution is not used
472 // within the const, this should still be fixed.
473 return ControlFlow::CONTINUE;
475 c.super_visit_with(self)
479 struct ProhibitOpaqueVisitor<'tcx> {
481 opaque_identity_ty: Ty<'tcx>,
482 generics: &'tcx ty::Generics,
483 selftys: Vec<(Span, Option<String>)>,
486 impl<'tcx> ty::fold::TypeVisitor<'tcx> for ProhibitOpaqueVisitor<'tcx> {
487 type BreakTy = Ty<'tcx>;
489 fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
490 debug!("check_opaque_for_inheriting_lifetimes: (visit_ty) t={:?}", t);
491 if t == self.opaque_identity_ty {
492 ControlFlow::CONTINUE
494 t.super_visit_with(&mut FindParentLifetimeVisitor(self.generics))
495 .map_break(|FoundParentLifetime| t)
500 impl<'tcx> Visitor<'tcx> for ProhibitOpaqueVisitor<'tcx> {
501 type NestedFilter = nested_filter::OnlyBodies;
503 fn nested_visit_map(&mut self) -> Self::Map {
507 fn visit_ty(&mut self, arg: &'tcx hir::Ty<'tcx>) {
509 hir::TyKind::Path(hir::QPath::Resolved(None, path)) => match &path.segments {
510 [PathSegment { res: Some(Res::SelfTy(_, impl_ref)), .. }] => {
512 impl_ref.map(|(def_id, _)| self.tcx.def_path_str(def_id));
513 self.selftys.push((path.span, impl_ty_name));
519 hir::intravisit::walk_ty(self, arg);
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),
537 let prohibit_opaque = tcx
538 .explicit_item_bounds(def_id)
540 .try_for_each(|(predicate, _)| predicate.visit_with(&mut visitor));
542 "check_opaque_for_inheriting_lifetimes: prohibit_opaque={:?}, visitor.opaque_identity_ty={:?}, visitor.generics={:?}",
543 prohibit_opaque, visitor.opaque_identity_ty, visitor.generics
546 if let Some(ty) = prohibit_opaque.break_value() {
547 visitor.visit_item(&item);
548 let is_async = match item.kind {
549 ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) => {
550 matches!(origin, hir::OpaqueTyOrigin::AsyncFn(..))
555 let mut err = struct_span_err!(
559 "`{}` return type cannot contain a projection or `Self` that references lifetimes from \
561 if is_async { "async fn" } else { "impl Trait" },
564 for (span, name) in visitor.selftys {
567 "consider spelling out the type instead",
568 name.unwrap_or_else(|| format!("{:?}", ty)),
569 Applicability::MaybeIncorrect,
577 /// Checks that an opaque type does not contain cycles.
578 pub(super) fn check_opaque_for_cycles<'tcx>(
581 substs: SubstsRef<'tcx>,
583 origin: &hir::OpaqueTyOrigin,
584 ) -> Result<(), ErrorReported> {
585 if tcx.try_expand_impl_trait_type(def_id.to_def_id(), substs).is_err() {
587 hir::OpaqueTyOrigin::AsyncFn(..) => async_opaque_type_cycle_error(tcx, span),
588 _ => opaque_type_cycle_error(tcx, def_id, span),
596 /// Check that the concrete type behind `impl Trait` actually implements `Trait`.
598 /// This is mostly checked at the places that specify the opaque type, but we
599 /// check those cases in the `param_env` of that function, which may have
600 /// bounds not on this opaque type:
602 /// type X<T> = impl Clone
603 /// fn f<T: Clone>(t: T) -> X<T> {
607 /// Without this check the above code is incorrectly accepted: we would ICE if
608 /// some tried, for example, to clone an `Option<X<&mut ()>>`.
609 #[instrument(level = "debug", skip(tcx))]
610 fn check_opaque_meets_bounds<'tcx>(
613 substs: SubstsRef<'tcx>,
615 origin: &hir::OpaqueTyOrigin,
617 let hidden_type = tcx.type_of(def_id).subst(tcx, substs);
619 let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
620 let defining_use_anchor = match *origin {
621 hir::OpaqueTyOrigin::FnReturn(did) | hir::OpaqueTyOrigin::AsyncFn(did) => did,
622 hir::OpaqueTyOrigin::TyAlias => def_id,
624 let param_env = tcx.param_env(defining_use_anchor);
626 tcx.infer_ctxt().with_opaque_type_inference(defining_use_anchor).enter(move |infcx| {
627 let inh = Inherited::new(infcx, def_id);
628 let infcx = &inh.infcx;
629 let opaque_ty = tcx.mk_opaque(def_id.to_def_id(), substs);
631 let misc_cause = traits::ObligationCause::misc(span, hir_id);
633 match infcx.at(&misc_cause, param_env).eq(opaque_ty, hidden_type) {
634 Ok(infer_ok) => inh.register_infer_ok_obligations(infer_ok),
635 Err(ty_err) => tcx.sess.delay_span_bug(
637 &format!("could not unify `{}` with revealed type:\n{}", hidden_type, ty_err,),
641 // Check that all obligations are satisfied by the implementation's
643 let errors = inh.fulfillment_cx.borrow_mut().select_all_or_error(&infcx);
644 if !errors.is_empty() {
645 infcx.report_fulfillment_errors(&errors, None, false);
649 // Checked when type checking the function containing them.
650 hir::OpaqueTyOrigin::FnReturn(..) | hir::OpaqueTyOrigin::AsyncFn(..) => {}
651 // Can have different predicates to their defining use
652 hir::OpaqueTyOrigin::TyAlias => {
653 // Finally, resolve all regions. This catches wily misuses of
654 // lifetime parameters.
655 let fcx = FnCtxt::new(&inh, param_env, hir_id);
656 fcx.regionck_item(hir_id, span, FxHashSet::default());
660 // Clean up after ourselves
661 let _ = infcx.inner.borrow_mut().opaque_type_storage.take_opaque_types();
665 pub fn check_item_type<'tcx>(tcx: TyCtxt<'tcx>, it: &'tcx hir::Item<'tcx>) {
667 "check_item_type(it.def_id={:?}, it.name={})",
669 tcx.def_path_str(it.def_id.to_def_id())
671 let _indenter = indenter();
673 // Consts can play a role in type-checking, so they are included here.
674 hir::ItemKind::Static(..) => {
675 tcx.ensure().typeck(it.def_id);
676 maybe_check_static_with_link_section(tcx, it.def_id, it.span);
677 check_static_inhabited(tcx, it.def_id, it.span);
679 hir::ItemKind::Const(..) => {
680 tcx.ensure().typeck(it.def_id);
682 hir::ItemKind::Enum(ref enum_definition, _) => {
683 check_enum(tcx, it.span, &enum_definition.variants, it.def_id);
685 hir::ItemKind::Fn(..) => {} // entirely within check_item_body
686 hir::ItemKind::Impl(ref impl_) => {
687 debug!("ItemKind::Impl {} with id {:?}", it.ident, it.def_id);
688 if let Some(impl_trait_ref) = tcx.impl_trait_ref(it.def_id) {
689 check_impl_items_against_trait(
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 check_on_unimplemented(tcx, it.def_id.to_def_id(), it);
703 for item in items.iter() {
704 let item = tcx.hir().trait_item(item.id);
706 hir::TraitItemKind::Fn(ref sig, _) => {
707 let abi = sig.header.abi;
708 fn_maybe_err(tcx, item.ident.span, abi);
710 hir::TraitItemKind::Type(.., Some(default)) => {
711 let assoc_item = tcx.associated_item(item.def_id);
713 InternalSubsts::identity_for_item(tcx, it.def_id.to_def_id());
714 let _: Result<_, rustc_errors::ErrorReported> = check_type_bounds(
719 ty::TraitRef { def_id: it.def_id.to_def_id(), substs: trait_substs },
726 hir::ItemKind::Struct(..) => {
727 check_struct(tcx, it.def_id, it.span);
729 hir::ItemKind::Union(..) => {
730 check_union(tcx, it.def_id, it.span);
732 hir::ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) => {
733 // HACK(jynelson): trying to infer the type of `impl trait` breaks documenting
734 // `async-std` (and `pub async fn` in general).
735 // Since rustdoc doesn't care about the concrete type behind `impl Trait`, just don't look at it!
736 // See https://github.com/rust-lang/rust/issues/75100
737 if !tcx.sess.opts.actually_rustdoc {
738 let substs = InternalSubsts::identity_for_item(tcx, it.def_id.to_def_id());
739 check_opaque(tcx, it.def_id, substs, it.span, &origin);
742 hir::ItemKind::TyAlias(..) => {
743 let pty_ty = tcx.type_of(it.def_id);
744 let generics = tcx.generics_of(it.def_id);
745 check_type_params_are_used(tcx, &generics, pty_ty);
747 hir::ItemKind::ForeignMod { abi, items } => {
748 check_abi(tcx, it.hir_id(), it.span, abi);
750 if abi == Abi::RustIntrinsic {
752 let item = tcx.hir().foreign_item(item.id);
753 intrinsic::check_intrinsic_type(tcx, item);
755 } else if abi == Abi::PlatformIntrinsic {
757 let item = tcx.hir().foreign_item(item.id);
758 intrinsic::check_platform_intrinsic_type(tcx, item);
762 let def_id = item.id.def_id;
763 let generics = tcx.generics_of(def_id);
764 let own_counts = generics.own_counts();
765 if generics.params.len() - own_counts.lifetimes != 0 {
766 let (kinds, kinds_pl, egs) = match (own_counts.types, own_counts.consts) {
767 (_, 0) => ("type", "types", Some("u32")),
768 // We don't specify an example value, because we can't generate
769 // a valid value for any type.
770 (0, _) => ("const", "consts", None),
771 _ => ("type or const", "types or consts", None),
777 "foreign items may not have {} parameters",
780 .span_label(item.span, &format!("can't have {} parameters", kinds))
782 // FIXME: once we start storing spans for type arguments, turn this
783 // into a suggestion.
785 "replace the {} parameters with concrete {}{}",
788 egs.map(|egs| format!(" like `{}`", egs)).unwrap_or_default(),
794 let item = tcx.hir().foreign_item(item.id);
796 hir::ForeignItemKind::Fn(ref fn_decl, _, _) => {
797 require_c_abi_if_c_variadic(tcx, fn_decl, abi, item.span);
799 hir::ForeignItemKind::Static(..) => {
800 check_static_inhabited(tcx, def_id, item.span);
807 _ => { /* nothing to do */ }
811 pub(super) fn check_on_unimplemented(tcx: TyCtxt<'_>, trait_def_id: DefId, item: &hir::Item<'_>) {
812 // an error would be reported if this fails.
813 let _ = traits::OnUnimplementedDirective::of_item(tcx, trait_def_id, item.def_id.to_def_id());
816 pub(super) fn check_specialization_validity<'tcx>(
818 trait_def: &ty::TraitDef,
819 trait_item: &ty::AssocItem,
821 impl_item: &hir::ImplItemRef,
823 let ancestors = match trait_def.ancestors(tcx, impl_id) {
824 Ok(ancestors) => ancestors,
827 let mut ancestor_impls = ancestors.skip(1).filter_map(|parent| {
828 if parent.is_from_trait() {
831 Some((parent, parent.item(tcx, trait_item.def_id)))
835 let opt_result = ancestor_impls.find_map(|(parent_impl, parent_item)| {
837 // Parent impl exists, and contains the parent item we're trying to specialize, but
838 // doesn't mark it `default`.
839 Some(parent_item) if traits::impl_item_is_final(tcx, &parent_item) => {
840 Some(Err(parent_impl.def_id()))
843 // Parent impl contains item and makes it specializable.
844 Some(_) => Some(Ok(())),
846 // Parent impl doesn't mention the item. This means it's inherited from the
847 // grandparent. In that case, if parent is a `default impl`, inherited items use the
848 // "defaultness" from the grandparent, else they are final.
850 if tcx.impl_defaultness(parent_impl.def_id()).is_default() {
853 Some(Err(parent_impl.def_id()))
859 // If `opt_result` is `None`, we have only encountered `default impl`s that don't contain the
860 // item. This is allowed, the item isn't actually getting specialized here.
861 let result = opt_result.unwrap_or(Ok(()));
863 if let Err(parent_impl) = result {
864 report_forbidden_specialization(tcx, impl_item, parent_impl);
868 fn check_impl_items_against_trait<'tcx>(
870 full_impl_span: Span,
872 impl_trait_ref: ty::TraitRef<'tcx>,
873 impl_item_refs: &[hir::ImplItemRef],
875 // If the trait reference itself is erroneous (so the compilation is going
876 // to fail), skip checking the items here -- the `impl_item` table in `tcx`
877 // isn't populated for such impls.
878 if impl_trait_ref.references_error() {
882 // Negative impls are not expected to have any items
883 match tcx.impl_polarity(impl_id) {
884 ty::ImplPolarity::Reservation | ty::ImplPolarity::Positive => {}
885 ty::ImplPolarity::Negative => {
886 if let [first_item_ref, ..] = impl_item_refs {
887 let first_item_span = tcx.hir().impl_item(first_item_ref.id).span;
892 "negative impls cannot have any items"
900 let trait_def = tcx.trait_def(impl_trait_ref.def_id);
902 for impl_item in impl_item_refs {
903 let ty_impl_item = tcx.associated_item(impl_item.id.def_id);
904 let ty_trait_item = if let Some(trait_item_id) = ty_impl_item.trait_item_def_id {
905 tcx.associated_item(trait_item_id)
907 // Checked in `associated_item`.
908 tcx.sess.delay_span_bug(impl_item.span, "missing associated item in trait");
911 let impl_item_full = tcx.hir().impl_item(impl_item.id);
912 match impl_item_full.kind {
913 hir::ImplItemKind::Const(..) => {
914 // Find associated const definition.
923 hir::ImplItemKind::Fn(..) => {
924 let opt_trait_span = tcx.hir().span_if_local(ty_trait_item.def_id);
934 hir::ImplItemKind::TyAlias(impl_ty) => {
935 let opt_trait_span = tcx.hir().span_if_local(ty_trait_item.def_id);
947 check_specialization_validity(
956 if let Ok(ancestors) = trait_def.ancestors(tcx, impl_id.to_def_id()) {
957 // Check for missing items from trait
958 let mut missing_items = Vec::new();
960 let mut must_implement_one_of: Option<&[Ident]> =
961 trait_def.must_implement_one_of.as_deref();
963 for &trait_item_id in tcx.associated_item_def_ids(impl_trait_ref.def_id) {
964 let is_implemented = ancestors
965 .leaf_def(tcx, trait_item_id)
966 .map_or(false, |node_item| node_item.item.defaultness.has_value());
968 if !is_implemented && tcx.impl_defaultness(impl_id).is_final() {
969 missing_items.push(tcx.associated_item(trait_item_id));
972 if let Some(required_items) = &must_implement_one_of {
973 // true if this item is specifically implemented in this impl
974 let is_implemented_here = ancestors
975 .leaf_def(tcx, trait_item_id)
976 .map_or(false, |node_item| !node_item.defining_node.is_from_trait());
978 if is_implemented_here {
979 let trait_item = tcx.associated_item(trait_item_id);
980 if required_items.contains(&trait_item.ident(tcx)) {
981 must_implement_one_of = None;
987 if !missing_items.is_empty() {
988 let impl_span = tcx.sess.source_map().guess_head_span(full_impl_span);
989 missing_items_err(tcx, impl_span, &missing_items, full_impl_span);
992 if let Some(missing_items) = must_implement_one_of {
993 let impl_span = tcx.sess.source_map().guess_head_span(full_impl_span);
995 .get_attrs(impl_trait_ref.def_id)
997 .find(|attr| attr.has_name(sym::rustc_must_implement_one_of))
998 .map(|attr| attr.span);
1000 missing_items_must_implement_one_of_err(tcx, impl_span, missing_items, attr_span);
1005 /// Checks whether a type can be represented in memory. In particular, it
1006 /// identifies types that contain themselves without indirection through a
1007 /// pointer, which would mean their size is unbounded.
1008 pub(super) fn check_representable(tcx: TyCtxt<'_>, sp: Span, item_def_id: LocalDefId) -> bool {
1009 let rty = tcx.type_of(item_def_id);
1011 // Check that it is possible to represent this type. This call identifies
1012 // (1) types that contain themselves and (2) types that contain a different
1013 // recursive type. It is only necessary to throw an error on those that
1014 // contain themselves. For case 2, there must be an inner type that will be
1015 // caught by case 1.
1016 match representability::ty_is_representable(tcx, rty, sp) {
1017 Representability::SelfRecursive(spans) => {
1018 recursive_type_with_infinite_size_error(tcx, item_def_id.to_def_id(), spans);
1021 Representability::Representable | Representability::ContainsRecursive => (),
1026 pub fn check_simd(tcx: TyCtxt<'_>, sp: Span, def_id: LocalDefId) {
1027 let t = tcx.type_of(def_id);
1028 if let ty::Adt(def, substs) = t.kind() {
1029 if def.is_struct() {
1030 let fields = &def.non_enum_variant().fields;
1031 if fields.is_empty() {
1032 struct_span_err!(tcx.sess, sp, E0075, "SIMD vector cannot be empty").emit();
1035 let e = fields[0].ty(tcx, substs);
1036 if !fields.iter().all(|f| f.ty(tcx, substs) == e) {
1037 struct_span_err!(tcx.sess, sp, E0076, "SIMD vector should be homogeneous")
1038 .span_label(sp, "SIMD elements must have the same type")
1043 let len = if let ty::Array(_ty, c) = e.kind() {
1044 c.try_eval_usize(tcx, tcx.param_env(def.did))
1046 Some(fields.len() as u64)
1048 if let Some(len) = len {
1050 struct_span_err!(tcx.sess, sp, E0075, "SIMD vector cannot be empty").emit();
1052 } else if len > MAX_SIMD_LANES {
1057 "SIMD vector cannot have more than {} elements",
1065 // Check that we use types valid for use in the lanes of a SIMD "vector register"
1066 // These are scalar types which directly match a "machine" type
1067 // Yes: Integers, floats, "thin" pointers
1068 // No: char, "fat" pointers, compound types
1070 ty::Param(_) => (), // pass struct<T>(T, T, T, T) through, let monomorphization catch errors
1071 ty::Int(_) | ty::Uint(_) | ty::Float(_) | ty::RawPtr(_) => (), // struct(u8, u8, u8, u8) is ok
1072 ty::Array(t, _) if matches!(t.kind(), ty::Param(_)) => (), // pass struct<T>([T; N]) through, let monomorphization catch errors
1076 ty::Int(_) | ty::Uint(_) | ty::Float(_) | ty::RawPtr(_)
1078 { /* struct([f32; 4]) is ok */ }
1084 "SIMD vector element type should be a \
1085 primitive scalar (integer/float/pointer) type"
1095 pub(super) fn check_packed(tcx: TyCtxt<'_>, sp: Span, def: &ty::AdtDef) {
1096 let repr = def.repr;
1098 for attr in tcx.get_attrs(def.did).iter() {
1099 for r in attr::find_repr_attrs(&tcx.sess, attr) {
1100 if let attr::ReprPacked(pack) = r {
1101 if let Some(repr_pack) = repr.pack {
1102 if pack as u64 != repr_pack.bytes() {
1107 "type has conflicting packed representation hints"
1115 if repr.align.is_some() {
1120 "type has conflicting packed and align representation hints"
1124 if let Some(def_spans) = check_packed_inner(tcx, def.did, &mut vec![]) {
1125 let mut err = struct_span_err!(
1129 "packed type cannot transitively contain a `#[repr(align)]` type"
1133 tcx.def_span(def_spans[0].0),
1135 "`{}` has a `#[repr(align)]` attribute",
1136 tcx.item_name(def_spans[0].0)
1140 if def_spans.len() > 2 {
1141 let mut first = true;
1142 for (adt_def, span) in def_spans.iter().skip(1).rev() {
1143 let ident = tcx.item_name(*adt_def);
1148 "`{}` contains a field of type `{}`",
1149 tcx.type_of(def.did),
1153 format!("...which contains a field of type `{}`", ident)
1166 pub(super) fn check_packed_inner(
1169 stack: &mut Vec<DefId>,
1170 ) -> Option<Vec<(DefId, Span)>> {
1171 if let ty::Adt(def, substs) = tcx.type_of(def_id).kind() {
1172 if def.is_struct() || def.is_union() {
1173 if def.repr.align.is_some() {
1174 return Some(vec![(def.did, DUMMY_SP)]);
1178 for field in &def.non_enum_variant().fields {
1179 if let ty::Adt(def, _) = field.ty(tcx, substs).kind() {
1180 if !stack.contains(&def.did) {
1181 if let Some(mut defs) = check_packed_inner(tcx, def.did, stack) {
1182 defs.push((def.did, field.ident(tcx).span));
1195 pub(super) fn check_transparent<'tcx>(tcx: TyCtxt<'tcx>, sp: Span, adt: &'tcx ty::AdtDef) {
1196 if !adt.repr.transparent() {
1199 let sp = tcx.sess.source_map().guess_head_span(sp);
1201 if adt.is_union() && !tcx.features().transparent_unions {
1203 &tcx.sess.parse_sess,
1204 sym::transparent_unions,
1206 "transparent unions are unstable",
1211 if adt.variants.len() != 1 {
1212 bad_variant_count(tcx, adt, sp, adt.did);
1213 if adt.variants.is_empty() {
1214 // Don't bother checking the fields. No variants (and thus no fields) exist.
1219 // For each field, figure out if it's known to be a ZST and align(1)
1220 let field_infos = adt.all_fields().map(|field| {
1221 let ty = field.ty(tcx, InternalSubsts::identity_for_item(tcx, field.did));
1222 let param_env = tcx.param_env(field.did);
1223 let layout = tcx.layout_of(param_env.and(ty));
1224 // We are currently checking the type this field came from, so it must be local
1225 let span = tcx.hir().span_if_local(field.did).unwrap();
1226 let zst = layout.map_or(false, |layout| layout.is_zst());
1227 let align1 = layout.map_or(false, |layout| layout.align.abi.bytes() == 1);
1231 let non_zst_fields =
1232 field_infos.clone().filter_map(|(span, zst, _align1)| if !zst { Some(span) } else { None });
1233 let non_zst_count = non_zst_fields.clone().count();
1234 if non_zst_count >= 2 {
1235 bad_non_zero_sized_fields(tcx, adt, non_zst_count, non_zst_fields, sp);
1237 for (span, zst, align1) in field_infos {
1243 "zero-sized field in transparent {} has alignment larger than 1",
1246 .span_label(span, "has alignment larger than 1")
1252 #[allow(trivial_numeric_casts)]
1253 fn check_enum<'tcx>(
1256 vs: &'tcx [hir::Variant<'tcx>],
1259 let def = tcx.adt_def(def_id);
1260 def.destructor(tcx); // force the destructor to be evaluated
1263 let attributes = tcx.get_attrs(def_id.to_def_id());
1264 if let Some(attr) = tcx.sess.find_by_name(&attributes, sym::repr) {
1269 "unsupported representation for zero-variant enum"
1271 .span_label(sp, "zero-variant enum")
1276 let repr_type_ty = def.repr.discr_type().to_ty(tcx);
1277 if repr_type_ty == tcx.types.i128 || repr_type_ty == tcx.types.u128 {
1278 if !tcx.features().repr128 {
1280 &tcx.sess.parse_sess,
1283 "repr with 128-bit type is unstable",
1290 if let Some(ref e) = v.disr_expr {
1291 tcx.ensure().typeck(tcx.hir().local_def_id(e.hir_id));
1295 if tcx.adt_def(def_id).repr.int.is_none() && tcx.features().arbitrary_enum_discriminant {
1296 let is_unit = |var: &hir::Variant<'_>| matches!(var.data, hir::VariantData::Unit(..));
1298 let has_disr = |var: &hir::Variant<'_>| var.disr_expr.is_some();
1299 let has_non_units = vs.iter().any(|var| !is_unit(var));
1300 let disr_units = vs.iter().any(|var| is_unit(&var) && has_disr(&var));
1301 let disr_non_unit = vs.iter().any(|var| !is_unit(&var) && has_disr(&var));
1303 if disr_non_unit || (disr_units && has_non_units) {
1305 struct_span_err!(tcx.sess, sp, E0732, "`#[repr(inttype)]` must be specified");
1310 let mut disr_vals: Vec<Discr<'tcx>> = Vec::with_capacity(vs.len());
1311 for ((_, discr), v) in iter::zip(def.discriminants(tcx), vs) {
1312 // Check for duplicate discriminant values
1313 if let Some(i) = disr_vals.iter().position(|&x| x.val == discr.val) {
1314 let variant_did = def.variants[VariantIdx::new(i)].def_id;
1315 let variant_i_hir_id = tcx.hir().local_def_id_to_hir_id(variant_did.expect_local());
1316 let variant_i = tcx.hir().expect_variant(variant_i_hir_id);
1317 let i_span = match variant_i.disr_expr {
1318 Some(ref expr) => tcx.hir().span(expr.hir_id),
1319 None => tcx.def_span(variant_did),
1321 let span = match v.disr_expr {
1322 Some(ref expr) => tcx.hir().span(expr.hir_id),
1325 let display_discr = display_discriminant_value(tcx, v, discr.val);
1326 let display_discr_i = display_discriminant_value(tcx, variant_i, disr_vals[i].val);
1331 "discriminant value `{}` already exists",
1334 .span_label(i_span, format!("first use of {}", display_discr_i))
1335 .span_label(span, format!("enum already has {}", display_discr))
1338 disr_vals.push(discr);
1341 check_representable(tcx, sp, def_id);
1342 check_transparent(tcx, sp, def);
1345 /// Format an enum discriminant value for use in a diagnostic message.
1346 fn display_discriminant_value<'tcx>(
1348 variant: &hir::Variant<'_>,
1351 if let Some(expr) = &variant.disr_expr {
1352 let body = &tcx.hir().body(expr.body).value;
1353 if let hir::ExprKind::Lit(lit) = &body.kind {
1354 if let rustc_ast::LitKind::Int(lit_value, _int_kind) = &lit.node {
1355 if evaluated != *lit_value {
1356 return format!("`{}` (overflowed from `{}`)", evaluated, lit_value);
1361 format!("`{}`", evaluated)
1364 pub(super) fn check_type_params_are_used<'tcx>(
1366 generics: &ty::Generics,
1369 debug!("check_type_params_are_used(generics={:?}, ty={:?})", generics, ty);
1371 assert_eq!(generics.parent, None);
1373 if generics.own_counts().types == 0 {
1377 let mut params_used = BitSet::new_empty(generics.params.len());
1379 if ty.references_error() {
1380 // If there is already another error, do not emit
1381 // an error for not using a type parameter.
1382 assert!(tcx.sess.has_errors());
1386 for leaf in ty.walk() {
1387 if let GenericArgKind::Type(leaf_ty) = leaf.unpack() {
1388 if let ty::Param(param) = leaf_ty.kind() {
1389 debug!("found use of ty param {:?}", param);
1390 params_used.insert(param.index);
1395 for param in &generics.params {
1396 if !params_used.contains(param.index) {
1397 if let ty::GenericParamDefKind::Type { .. } = param.kind {
1398 let span = tcx.def_span(param.def_id);
1403 "type parameter `{}` is unused",
1406 .span_label(span, "unused type parameter")
1413 pub(super) fn check_mod_item_types(tcx: TyCtxt<'_>, module_def_id: LocalDefId) {
1414 tcx.hir().visit_item_likes_in_module(module_def_id, &mut CheckItemTypesVisitor { tcx });
1417 pub(super) use wfcheck::check_item_well_formed;
1419 pub(super) use wfcheck::check_trait_item as check_trait_item_well_formed;
1421 pub(super) use wfcheck::check_impl_item as check_impl_item_well_formed;
1423 fn async_opaque_type_cycle_error(tcx: TyCtxt<'_>, span: Span) {
1424 struct_span_err!(tcx.sess, span, E0733, "recursion in an `async fn` requires boxing")
1425 .span_label(span, "recursive `async fn`")
1426 .note("a recursive `async fn` must be rewritten to return a boxed `dyn Future`")
1428 "consider using the `async_recursion` crate: https://crates.io/crates/async_recursion",
1433 /// Emit an error for recursive opaque types.
1435 /// If this is a return `impl Trait`, find the item's return expressions and point at them. For
1436 /// direct recursion this is enough, but for indirect recursion also point at the last intermediary
1439 /// If all the return expressions evaluate to `!`, then we explain that the error will go away
1440 /// after changing it. This can happen when a user uses `panic!()` or similar as a placeholder.
1441 fn opaque_type_cycle_error(tcx: TyCtxt<'_>, def_id: LocalDefId, span: Span) {
1442 let mut err = struct_span_err!(tcx.sess, span, E0720, "cannot resolve opaque type");
1444 let mut label = false;
1445 if let Some((def_id, visitor)) = get_owner_return_paths(tcx, def_id) {
1446 let typeck_results = tcx.typeck(def_id);
1450 .filter_map(|expr| typeck_results.node_type_opt(expr.hir_id))
1451 .all(|ty| matches!(ty.kind(), ty::Never))
1456 .filter(|expr| typeck_results.node_type_opt(expr.hir_id).is_some())
1457 .map(|expr| expr.span)
1458 .collect::<Vec<Span>>();
1459 let span_len = spans.len();
1461 err.span_label(spans[0], "this returned value is of `!` type");
1463 let mut multispan: MultiSpan = spans.clone().into();
1466 .push_span_label(span, "this returned value is of `!` type".to_string());
1468 err.span_note(multispan, "these returned values have a concrete \"never\" type");
1470 err.help("this error will resolve once the item's body returns a concrete type");
1472 let mut seen = FxHashSet::default();
1474 err.span_label(span, "recursive opaque type");
1476 for (sp, ty) in visitor
1479 .filter_map(|e| typeck_results.node_type_opt(e.hir_id).map(|t| (e.span, t)))
1480 .filter(|(_, ty)| !matches!(ty.kind(), ty::Never))
1482 struct OpaqueTypeCollector(Vec<DefId>);
1483 impl<'tcx> ty::fold::TypeVisitor<'tcx> for OpaqueTypeCollector {
1484 fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
1486 ty::Opaque(def, _) => {
1488 ControlFlow::CONTINUE
1490 _ => t.super_visit_with(self),
1494 let mut visitor = OpaqueTypeCollector(vec![]);
1495 ty.visit_with(&mut visitor);
1496 for def_id in visitor.0 {
1497 let ty_span = tcx.def_span(def_id);
1498 if !seen.contains(&ty_span) {
1499 err.span_label(ty_span, &format!("returning this opaque type `{}`", ty));
1500 seen.insert(ty_span);
1502 err.span_label(sp, &format!("returning here with type `{}`", ty));
1508 err.span_label(span, "cannot resolve opaque type");