1 use crate::check::intrinsicck::InlineAsmCtxt;
3 use super::coercion::CoerceMany;
4 use super::compare_method::check_type_bounds;
5 use super::compare_method::{compare_const_impl, compare_impl_method, compare_ty_impl};
7 use rustc_attr as attr;
8 use rustc_errors::{Applicability, ErrorGuaranteed, MultiSpan};
10 use rustc_hir::def::{DefKind, Res};
11 use rustc_hir::def_id::{DefId, LocalDefId};
12 use rustc_hir::intravisit::Visitor;
13 use rustc_hir::lang_items::LangItem;
14 use rustc_hir::{ItemKind, Node, PathSegment};
15 use rustc_infer::infer::outlives::env::OutlivesEnvironment;
16 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
17 use rustc_infer::infer::{DefiningAnchor, RegionVariableOrigin, TyCtxtInferExt};
18 use rustc_infer::traits::Obligation;
19 use rustc_lint::builtin::REPR_TRANSPARENT_EXTERNAL_PRIVATE_FIELDS;
20 use rustc_middle::hir::nested_filter;
21 use rustc_middle::middle::stability::EvalResult;
22 use rustc_middle::ty::layout::{LayoutError, MAX_SIMD_LANES};
23 use rustc_middle::ty::subst::GenericArgKind;
24 use rustc_middle::ty::util::{Discr, IntTypeExt};
25 use rustc_middle::ty::{
26 self, ParamEnv, ToPredicate, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable,
28 use rustc_session::lint::builtin::{UNINHABITED_STATIC, UNSUPPORTED_CALLING_CONVENTIONS};
29 use rustc_span::symbol::sym;
30 use rustc_span::{self, Span};
31 use rustc_target::spec::abi::Abi;
32 use rustc_trait_selection::traits::error_reporting::InferCtxtExt as _;
33 use rustc_trait_selection::traits::{self, ObligationCtxt};
34 use rustc_ty_utils::representability::{self, Representability};
36 use std::ops::ControlFlow;
38 pub(super) fn check_abi(tcx: TyCtxt<'_>, hir_id: hir::HirId, span: Span, abi: Abi) {
39 match tcx.sess.target.is_abi_supported(abi) {
46 "`{abi}` is not a supported ABI for the current target",
51 tcx.struct_span_lint_hir(
52 UNSUPPORTED_CALLING_CONVENTIONS,
55 "use of calling convention not supported on this target",
61 // This ABI is only allowed on function pointers
62 if abi == Abi::CCmseNonSecureCall {
67 "the `\"C-cmse-nonsecure-call\"` ABI is only allowed on function pointers"
73 /// Helper used for fns and closures. Does the grungy work of checking a function
74 /// body and returns the function context used for that purpose, since in the case of a fn item
75 /// there is still a bit more to do.
78 /// * inherited: other fields inherited from the enclosing fn (if any)
79 #[instrument(skip(inherited, body), level = "debug")]
80 pub(super) fn check_fn<'a, 'tcx>(
81 inherited: &'a Inherited<'a, 'tcx>,
82 param_env: ty::ParamEnv<'tcx>,
83 fn_sig: ty::FnSig<'tcx>,
84 decl: &'tcx hir::FnDecl<'tcx>,
86 body: &'tcx hir::Body<'tcx>,
87 can_be_generator: Option<hir::Movability>,
88 return_type_pre_known: bool,
89 ) -> (FnCtxt<'a, 'tcx>, Option<GeneratorTypes<'tcx>>) {
90 // Create the function context. This is either derived from scratch or,
91 // in the case of closures, based on the outer context.
92 let mut fcx = FnCtxt::new(inherited, param_env, body.value.hir_id);
93 fcx.ps.set(UnsafetyState::function(fn_sig.unsafety, fn_id));
94 fcx.return_type_pre_known = return_type_pre_known;
99 let declared_ret_ty = fn_sig.output();
102 fcx.register_infer_ok_obligations(fcx.infcx.replace_opaque_types_with_inference_vars(
108 // If we replaced declared_ret_ty with infer vars, then we must be inferring
109 // an opaque type, so set a flag so we can improve diagnostics.
110 fcx.return_type_has_opaque = ret_ty != declared_ret_ty;
112 fcx.ret_coercion = Some(RefCell::new(CoerceMany::new(ret_ty)));
114 let span = body.value.span;
116 fn_maybe_err(tcx, span, fn_sig.abi);
118 if fn_sig.abi == Abi::RustCall {
119 let expected_args = if let ImplicitSelfKind::None = decl.implicit_self { 1 } else { 2 };
122 let item = match tcx.hir().get(fn_id) {
123 Node::Item(hir::Item { kind: ItemKind::Fn(header, ..), .. }) => Some(header),
124 Node::ImplItem(hir::ImplItem {
125 kind: hir::ImplItemKind::Fn(header, ..), ..
127 Node::TraitItem(hir::TraitItem {
128 kind: hir::TraitItemKind::Fn(header, ..),
131 // Closures are RustCall, but they tuple their arguments, so shouldn't be checked
132 Node::Expr(hir::Expr { kind: hir::ExprKind::Closure { .. }, .. }) => None,
133 node => bug!("Item being checked wasn't a function/closure: {:?}", node),
136 if let Some(header) = item {
137 tcx.sess.span_err(header.span, "functions with the \"rust-call\" ABI must take a single non-self argument that is a tuple");
141 if fn_sig.inputs().len() != expected_args {
144 // FIXME(CraftSpider) Add a check on parameter expansion, so we don't just make the ICE happen later on
145 // This will probably require wide-scale changes to support a TupleKind obligation
146 // We can't resolve this without knowing the type of the param
147 if !matches!(fn_sig.inputs()[expected_args - 1].kind(), ty::Tuple(_) | ty::Param(_)) {
153 if body.generator_kind.is_some() && can_be_generator.is_some() {
155 .next_ty_var(TypeVariableOrigin { kind: TypeVariableOriginKind::TypeInference, span });
156 fcx.require_type_is_sized(yield_ty, span, traits::SizedYieldType);
158 // Resume type defaults to `()` if the generator has no argument.
159 let resume_ty = fn_sig.inputs().get(0).copied().unwrap_or_else(|| tcx.mk_unit());
161 fcx.resume_yield_tys = Some((resume_ty, yield_ty));
164 GatherLocalsVisitor::new(&fcx).visit_body(body);
166 // C-variadic fns also have a `VaList` input that's not listed in `fn_sig`
167 // (as it's created inside the body itself, not passed in from outside).
168 let maybe_va_list = if fn_sig.c_variadic {
169 let span = body.params.last().unwrap().span;
170 let va_list_did = tcx.require_lang_item(LangItem::VaList, Some(span));
171 let region = fcx.next_region_var(RegionVariableOrigin::MiscVariable(span));
173 Some(tcx.bound_type_of(va_list_did).subst(tcx, &[region.into()]))
178 // Add formal parameters.
179 let inputs_hir = hir.fn_decl_by_hir_id(fn_id).map(|decl| &decl.inputs);
180 let inputs_fn = fn_sig.inputs().iter().copied();
181 for (idx, (param_ty, param)) in inputs_fn.chain(maybe_va_list).zip(body.params).enumerate() {
182 // Check the pattern.
183 let ty_span = try { inputs_hir?.get(idx)?.span };
184 fcx.check_pat_top(¶m.pat, param_ty, ty_span, false);
186 // Check that argument is Sized.
187 // The check for a non-trivial pattern is a hack to avoid duplicate warnings
188 // for simple cases like `fn foo(x: Trait)`,
189 // where we would error once on the parameter as a whole, and once on the binding `x`.
190 if param.pat.simple_ident().is_none() && !tcx.features().unsized_fn_params {
191 fcx.require_type_is_sized(param_ty, param.pat.span, traits::SizedArgumentType(ty_span));
194 fcx.write_ty(param.hir_id, param_ty);
197 inherited.typeck_results.borrow_mut().liberated_fn_sigs_mut().insert(fn_id, fn_sig);
199 fcx.in_tail_expr = true;
200 if let ty::Dynamic(..) = declared_ret_ty.kind() {
201 // FIXME: We need to verify that the return type is `Sized` after the return expression has
202 // been evaluated so that we have types available for all the nodes being returned, but that
203 // requires the coerced evaluated type to be stored. Moving `check_return_expr` before this
204 // causes unsized errors caused by the `declared_ret_ty` to point at the return expression,
205 // while keeping the current ordering we will ignore the tail expression's type because we
206 // don't know it yet. We can't do `check_expr_kind` while keeping `check_return_expr`
207 // because we will trigger "unreachable expression" lints unconditionally.
208 // Because of all of this, we perform a crude check to know whether the simplest `!Sized`
209 // case that a newcomer might make, returning a bare trait, and in that case we populate
210 // the tail expression's type so that the suggestion will be correct, but ignore all other
212 fcx.check_expr(&body.value);
213 fcx.require_type_is_sized(declared_ret_ty, decl.output.span(), traits::SizedReturnType);
215 fcx.require_type_is_sized(declared_ret_ty, decl.output.span(), traits::SizedReturnType);
216 fcx.check_return_expr(&body.value, false);
218 fcx.in_tail_expr = false;
220 // We insert the deferred_generator_interiors entry after visiting the body.
221 // This ensures that all nested generators appear before the entry of this generator.
222 // resolve_generator_interiors relies on this property.
223 let gen_ty = if let (Some(_), Some(gen_kind)) = (can_be_generator, body.generator_kind) {
225 .next_ty_var(TypeVariableOrigin { kind: TypeVariableOriginKind::MiscVariable, span });
226 fcx.deferred_generator_interiors.borrow_mut().push((body.id(), interior, gen_kind));
228 let (resume_ty, yield_ty) = fcx.resume_yield_tys.unwrap();
229 Some(GeneratorTypes {
233 movability: can_be_generator.unwrap(),
239 // Finalize the return check by taking the LUB of the return types
240 // we saw and assigning it to the expected return type. This isn't
241 // really expected to fail, since the coercions would have failed
242 // earlier when trying to find a LUB.
243 let coercion = fcx.ret_coercion.take().unwrap().into_inner();
244 let mut actual_return_ty = coercion.complete(&fcx);
245 debug!("actual_return_ty = {:?}", actual_return_ty);
246 if let ty::Dynamic(..) = declared_ret_ty.kind() {
247 // We have special-cased the case where the function is declared
248 // `-> dyn Foo` and we don't actually relate it to the
249 // `fcx.ret_coercion`, so just substitute a type variable.
251 fcx.next_ty_var(TypeVariableOrigin { kind: TypeVariableOriginKind::DynReturnFn, span });
252 debug!("actual_return_ty replaced with {:?}", actual_return_ty);
255 // HACK(oli-obk, compiler-errors): We should be comparing this against
256 // `declared_ret_ty`, but then anything uninferred would be inferred to
257 // the opaque type itself. That again would cause writeback to assume
258 // we have a recursive call site and do the sadly stabilized fallback to `()`.
259 fcx.demand_suptype(span, ret_ty, actual_return_ty);
261 // Check that a function marked as `#[panic_handler]` has signature `fn(&PanicInfo) -> !`
262 if let Some(panic_impl_did) = tcx.lang_items().panic_impl()
263 && panic_impl_did == hir.local_def_id(fn_id).to_def_id()
265 check_panic_info_fn(tcx, panic_impl_did.expect_local(), fn_sig, decl, declared_ret_ty);
268 // Check that a function marked as `#[alloc_error_handler]` has signature `fn(Layout) -> !`
269 if let Some(alloc_error_handler_did) = tcx.lang_items().oom()
270 && alloc_error_handler_did == hir.local_def_id(fn_id).to_def_id()
272 check_alloc_error_fn(tcx, alloc_error_handler_did.expect_local(), fn_sig, decl, declared_ret_ty);
278 fn check_panic_info_fn(
281 fn_sig: ty::FnSig<'_>,
282 decl: &hir::FnDecl<'_>,
283 declared_ret_ty: Ty<'_>,
285 let Some(panic_info_did) = tcx.lang_items().panic_info() else {
286 tcx.sess.err("language item required, but not found: `panic_info`");
290 if *declared_ret_ty.kind() != ty::Never {
291 tcx.sess.span_err(decl.output.span(), "return type should be `!`");
294 let inputs = fn_sig.inputs();
295 if inputs.len() != 1 {
296 tcx.sess.span_err(tcx.def_span(fn_id), "function should have one argument");
300 let arg_is_panic_info = match *inputs[0].kind() {
301 ty::Ref(region, ty, mutbl) => match *ty.kind() {
302 ty::Adt(ref adt, _) => {
303 adt.did() == panic_info_did && mutbl == hir::Mutability::Not && !region.is_static()
310 if !arg_is_panic_info {
311 tcx.sess.span_err(decl.inputs[0].span, "argument should be `&PanicInfo`");
314 let DefKind::Fn = tcx.def_kind(fn_id) else {
315 let span = tcx.def_span(fn_id);
316 tcx.sess.span_err(span, "should be a function");
320 let generic_counts = tcx.generics_of(fn_id).own_counts();
321 if generic_counts.types != 0 {
322 let span = tcx.def_span(fn_id);
323 tcx.sess.span_err(span, "should have no type parameters");
325 if generic_counts.consts != 0 {
326 let span = tcx.def_span(fn_id);
327 tcx.sess.span_err(span, "should have no const parameters");
331 fn check_alloc_error_fn(
334 fn_sig: ty::FnSig<'_>,
335 decl: &hir::FnDecl<'_>,
336 declared_ret_ty: Ty<'_>,
338 let Some(alloc_layout_did) = tcx.lang_items().alloc_layout() else {
339 tcx.sess.err("language item required, but not found: `alloc_layout`");
343 if *declared_ret_ty.kind() != ty::Never {
344 tcx.sess.span_err(decl.output.span(), "return type should be `!`");
347 let inputs = fn_sig.inputs();
348 if inputs.len() != 1 {
349 tcx.sess.span_err(tcx.def_span(fn_id), "function should have one argument");
353 let arg_is_alloc_layout = match inputs[0].kind() {
354 ty::Adt(ref adt, _) => adt.did() == alloc_layout_did,
358 if !arg_is_alloc_layout {
359 tcx.sess.span_err(decl.inputs[0].span, "argument should be `Layout`");
362 let DefKind::Fn = tcx.def_kind(fn_id) else {
363 let span = tcx.def_span(fn_id);
364 tcx.sess.span_err(span, "`#[alloc_error_handler]` should be a function");
368 let generic_counts = tcx.generics_of(fn_id).own_counts();
369 if generic_counts.types != 0 {
370 let span = tcx.def_span(fn_id);
371 tcx.sess.span_err(span, "`#[alloc_error_handler]` function should have no type parameters");
373 if generic_counts.consts != 0 {
374 let span = tcx.def_span(fn_id);
376 .span_err(span, "`#[alloc_error_handler]` function should have no const parameters");
380 fn check_struct(tcx: TyCtxt<'_>, def_id: LocalDefId) {
381 let def = tcx.adt_def(def_id);
382 let span = tcx.def_span(def_id);
383 def.destructor(tcx); // force the destructor to be evaluated
384 check_representable(tcx, span, def_id);
386 if def.repr().simd() {
387 check_simd(tcx, span, def_id);
390 check_transparent(tcx, span, def);
391 check_packed(tcx, span, def);
394 fn check_union(tcx: TyCtxt<'_>, def_id: LocalDefId) {
395 let def = tcx.adt_def(def_id);
396 let span = tcx.def_span(def_id);
397 def.destructor(tcx); // force the destructor to be evaluated
398 check_representable(tcx, span, def_id);
399 check_transparent(tcx, span, def);
400 check_union_fields(tcx, span, def_id);
401 check_packed(tcx, span, def);
404 /// Check that the fields of the `union` do not need dropping.
405 fn check_union_fields(tcx: TyCtxt<'_>, span: Span, item_def_id: LocalDefId) -> bool {
406 let item_type = tcx.type_of(item_def_id);
407 if let ty::Adt(def, substs) = item_type.kind() {
408 assert!(def.is_union());
410 fn allowed_union_field<'tcx>(
413 param_env: ty::ParamEnv<'tcx>,
416 // We don't just accept all !needs_drop fields, due to semver concerns.
418 ty::Ref(..) => true, // references never drop (even mutable refs, which are non-Copy and hence fail the later check)
420 // allow tuples of allowed types
421 tys.iter().all(|ty| allowed_union_field(ty, tcx, param_env, span))
423 ty::Array(elem, _len) => {
424 // Like `Copy`, we do *not* special-case length 0.
425 allowed_union_field(*elem, tcx, param_env, span)
428 // Fallback case: allow `ManuallyDrop` and things that are `Copy`.
429 ty.ty_adt_def().is_some_and(|adt_def| adt_def.is_manually_drop())
430 || ty.is_copy_modulo_regions(tcx.at(span), param_env)
435 let param_env = tcx.param_env(item_def_id);
436 for field in &def.non_enum_variant().fields {
437 let field_ty = field.ty(tcx, substs);
439 if !allowed_union_field(field_ty, tcx, param_env, span) {
440 let (field_span, ty_span) = match tcx.hir().get_if_local(field.did) {
441 // We are currently checking the type this field came from, so it must be local.
442 Some(Node::Field(field)) => (field.span, field.ty.span),
443 _ => unreachable!("mir field has to correspond to hir field"),
449 "unions cannot contain fields that may need dropping"
452 "a type is guaranteed not to need dropping \
453 when it implements `Copy`, or when it is the special `ManuallyDrop<_>` type",
455 .multipart_suggestion_verbose(
456 "when the type does not implement `Copy`, \
457 wrap it inside a `ManuallyDrop<_>` and ensure it is manually dropped",
459 (ty_span.shrink_to_lo(), "std::mem::ManuallyDrop<".into()),
460 (ty_span.shrink_to_hi(), ">".into()),
462 Applicability::MaybeIncorrect,
466 } else if field_ty.needs_drop(tcx, param_env) {
467 // This should never happen. But we can get here e.g. in case of name resolution errors.
468 tcx.sess.delay_span_bug(span, "we should never accept maybe-dropping union fields");
472 span_bug!(span, "unions must be ty::Adt, but got {:?}", item_type.kind());
477 /// Check that a `static` is inhabited.
478 fn check_static_inhabited<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) {
479 // Make sure statics are inhabited.
480 // Other parts of the compiler assume that there are no uninhabited places. In principle it
481 // would be enough to check this for `extern` statics, as statics with an initializer will
482 // have UB during initialization if they are uninhabited, but there also seems to be no good
483 // reason to allow any statics to be uninhabited.
484 let ty = tcx.type_of(def_id);
485 let span = tcx.def_span(def_id);
486 let layout = match tcx.layout_of(ParamEnv::reveal_all().and(ty)) {
488 // Foreign statics that overflow their allowed size should emit an error
489 Err(LayoutError::SizeOverflow(_))
491 let node = tcx.hir().get_by_def_id(def_id);
494 hir::Node::ForeignItem(hir::ForeignItem {
495 kind: hir::ForeignItemKind::Static(..),
502 .struct_span_err(span, "extern static is too large for the current architecture")
506 // Generic statics are rejected, but we still reach this case.
508 tcx.sess.delay_span_bug(span, &e.to_string());
512 if layout.abi.is_uninhabited() {
513 tcx.struct_span_lint_hir(
515 tcx.hir().local_def_id_to_hir_id(def_id),
517 "static of uninhabited type",
520 .note("uninhabited statics cannot be initialized, and any access would be an immediate error")
526 /// Checks that an opaque type does not contain cycles and does not use `Self` or `T::Foo`
527 /// projections that would result in "inheriting lifetimes".
528 pub(super) fn check_opaque<'tcx>(
531 substs: SubstsRef<'tcx>,
532 origin: &hir::OpaqueTyOrigin,
534 let span = tcx.def_span(def_id);
535 check_opaque_for_inheriting_lifetimes(tcx, def_id, span);
536 if tcx.type_of(def_id).references_error() {
539 if check_opaque_for_cycles(tcx, def_id, substs, span, origin).is_err() {
542 check_opaque_meets_bounds(tcx, def_id, substs, span, origin);
545 /// Checks that an opaque type does not use `Self` or `T::Foo` projections that would result
546 /// in "inheriting lifetimes".
547 #[instrument(level = "debug", skip(tcx, span))]
548 pub(super) fn check_opaque_for_inheriting_lifetimes<'tcx>(
553 let item = tcx.hir().expect_item(def_id);
554 debug!(?item, ?span);
556 struct FoundParentLifetime;
557 struct FindParentLifetimeVisitor<'tcx>(&'tcx ty::Generics);
558 impl<'tcx> ty::visit::TypeVisitor<'tcx> for FindParentLifetimeVisitor<'tcx> {
559 type BreakTy = FoundParentLifetime;
561 fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> {
562 debug!("FindParentLifetimeVisitor: r={:?}", r);
563 if let ty::ReEarlyBound(ty::EarlyBoundRegion { index, .. }) = *r {
564 if index < self.0.parent_count as u32 {
565 return ControlFlow::Break(FoundParentLifetime);
567 return ControlFlow::CONTINUE;
571 r.super_visit_with(self)
574 fn visit_const(&mut self, c: ty::Const<'tcx>) -> ControlFlow<Self::BreakTy> {
575 if let ty::ConstKind::Unevaluated(..) = c.kind() {
576 // FIXME(#72219) We currently don't detect lifetimes within substs
577 // which would violate this check. Even though the particular substitution is not used
578 // within the const, this should still be fixed.
579 return ControlFlow::CONTINUE;
581 c.super_visit_with(self)
585 struct ProhibitOpaqueVisitor<'tcx> {
587 opaque_identity_ty: Ty<'tcx>,
588 generics: &'tcx ty::Generics,
589 selftys: Vec<(Span, Option<String>)>,
592 impl<'tcx> ty::visit::TypeVisitor<'tcx> for ProhibitOpaqueVisitor<'tcx> {
593 type BreakTy = Ty<'tcx>;
595 fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
596 debug!("check_opaque_for_inheriting_lifetimes: (visit_ty) t={:?}", t);
597 if t == self.opaque_identity_ty {
598 ControlFlow::CONTINUE
600 t.super_visit_with(&mut FindParentLifetimeVisitor(self.generics))
601 .map_break(|FoundParentLifetime| t)
606 impl<'tcx> Visitor<'tcx> for ProhibitOpaqueVisitor<'tcx> {
607 type NestedFilter = nested_filter::OnlyBodies;
609 fn nested_visit_map(&mut self) -> Self::Map {
613 fn visit_ty(&mut self, arg: &'tcx hir::Ty<'tcx>) {
615 hir::TyKind::Path(hir::QPath::Resolved(None, path)) => match &path.segments {
616 [PathSegment { res: Res::SelfTyParam { .. }, .. }] => {
617 let impl_ty_name = None;
618 self.selftys.push((path.span, impl_ty_name));
620 [PathSegment { res: Res::SelfTyAlias { alias_to: def_id, .. }, .. }] => {
621 let impl_ty_name = Some(self.tcx.def_path_str(*def_id));
622 self.selftys.push((path.span, impl_ty_name));
628 hir::intravisit::walk_ty(self, arg);
632 if let ItemKind::OpaqueTy(hir::OpaqueTy {
633 origin: hir::OpaqueTyOrigin::AsyncFn(..) | hir::OpaqueTyOrigin::FnReturn(..),
637 let mut visitor = ProhibitOpaqueVisitor {
638 opaque_identity_ty: tcx.mk_opaque(
640 InternalSubsts::identity_for_item(tcx, def_id.to_def_id()),
642 generics: tcx.generics_of(def_id),
646 let prohibit_opaque = tcx
647 .explicit_item_bounds(def_id)
649 .try_for_each(|(predicate, _)| predicate.visit_with(&mut visitor));
651 "check_opaque_for_inheriting_lifetimes: prohibit_opaque={:?}, visitor.opaque_identity_ty={:?}, visitor.generics={:?}",
652 prohibit_opaque, visitor.opaque_identity_ty, visitor.generics
655 if let Some(ty) = prohibit_opaque.break_value() {
656 visitor.visit_item(&item);
657 let is_async = match item.kind {
658 ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) => {
659 matches!(origin, hir::OpaqueTyOrigin::AsyncFn(..))
664 let mut err = struct_span_err!(
668 "`{}` return type cannot contain a projection or `Self` that references lifetimes from \
670 if is_async { "async fn" } else { "impl Trait" },
673 for (span, name) in visitor.selftys {
676 "consider spelling out the type instead",
677 name.unwrap_or_else(|| format!("{:?}", ty)),
678 Applicability::MaybeIncorrect,
686 /// Checks that an opaque type does not contain cycles.
687 pub(super) fn check_opaque_for_cycles<'tcx>(
690 substs: SubstsRef<'tcx>,
692 origin: &hir::OpaqueTyOrigin,
693 ) -> Result<(), ErrorGuaranteed> {
694 if tcx.try_expand_impl_trait_type(def_id.to_def_id(), substs).is_err() {
695 let reported = match origin {
696 hir::OpaqueTyOrigin::AsyncFn(..) => async_opaque_type_cycle_error(tcx, span),
697 _ => opaque_type_cycle_error(tcx, def_id, span),
705 /// Check that the concrete type behind `impl Trait` actually implements `Trait`.
707 /// This is mostly checked at the places that specify the opaque type, but we
708 /// check those cases in the `param_env` of that function, which may have
709 /// bounds not on this opaque type:
711 /// type X<T> = impl Clone
712 /// fn f<T: Clone>(t: T) -> X<T> {
716 /// Without this check the above code is incorrectly accepted: we would ICE if
717 /// some tried, for example, to clone an `Option<X<&mut ()>>`.
718 #[instrument(level = "debug", skip(tcx))]
719 fn check_opaque_meets_bounds<'tcx>(
722 substs: SubstsRef<'tcx>,
724 origin: &hir::OpaqueTyOrigin,
726 let hidden_type = tcx.bound_type_of(def_id.to_def_id()).subst(tcx, substs);
728 let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
729 let defining_use_anchor = match *origin {
730 hir::OpaqueTyOrigin::FnReturn(did) | hir::OpaqueTyOrigin::AsyncFn(did) => did,
731 hir::OpaqueTyOrigin::TyAlias => def_id,
733 let param_env = tcx.param_env(defining_use_anchor);
735 tcx.infer_ctxt().with_opaque_type_inference(DefiningAnchor::Bind(defining_use_anchor)).enter(
737 let ocx = ObligationCtxt::new(&infcx);
738 let opaque_ty = tcx.mk_opaque(def_id.to_def_id(), substs);
740 let misc_cause = traits::ObligationCause::misc(span, hir_id);
742 match infcx.at(&misc_cause, param_env).eq(opaque_ty, hidden_type) {
743 Ok(infer_ok) => ocx.register_infer_ok_obligations(infer_ok),
745 tcx.sess.delay_span_bug(
747 &format!("could not unify `{hidden_type}` with revealed type:\n{ty_err}"),
752 // Additionally require the hidden type to be well-formed with only the generics of the opaque type.
753 // Defining use functions may have more bounds than the opaque type, which is ok, as long as the
754 // hidden type is well formed even without those bounds.
755 let predicate = ty::Binder::dummy(ty::PredicateKind::WellFormed(hidden_type.into()))
757 ocx.register_obligation(Obligation::new(misc_cause, param_env, predicate));
759 // Check that all obligations are satisfied by the implementation's
761 let errors = ocx.select_all_or_error();
762 if !errors.is_empty() {
763 infcx.report_fulfillment_errors(&errors, None, false);
766 // Checked when type checking the function containing them.
767 hir::OpaqueTyOrigin::FnReturn(..) | hir::OpaqueTyOrigin::AsyncFn(..) => {}
768 // Can have different predicates to their defining use
769 hir::OpaqueTyOrigin::TyAlias => {
770 let outlives_environment = OutlivesEnvironment::new(param_env);
771 infcx.check_region_obligations_and_report_errors(
773 &outlives_environment,
777 // Clean up after ourselves
778 let _ = infcx.inner.borrow_mut().opaque_type_storage.take_opaque_types();
783 fn check_item_type<'tcx>(tcx: TyCtxt<'tcx>, id: hir::ItemId) {
785 "check_item_type(it.def_id={:?}, it.name={})",
787 tcx.def_path_str(id.def_id.to_def_id())
789 let _indenter = indenter();
790 match tcx.def_kind(id.def_id) {
791 DefKind::Static(..) => {
792 tcx.ensure().typeck(id.def_id.def_id);
793 maybe_check_static_with_link_section(tcx, id.def_id.def_id);
794 check_static_inhabited(tcx, id.def_id.def_id);
797 tcx.ensure().typeck(id.def_id.def_id);
800 let item = tcx.hir().item(id);
801 let hir::ItemKind::Enum(ref enum_definition, _) = item.kind else {
804 check_enum(tcx, &enum_definition.variants, item.def_id.def_id);
806 DefKind::Fn => {} // entirely within check_item_body
808 let it = tcx.hir().item(id);
809 let hir::ItemKind::Impl(ref impl_) = it.kind else {
812 debug!("ItemKind::Impl {} with id {:?}", it.ident, it.def_id);
813 if let Some(impl_trait_ref) = tcx.impl_trait_ref(it.def_id) {
814 check_impl_items_against_trait(
821 check_on_unimplemented(tcx, it);
825 let it = tcx.hir().item(id);
826 let hir::ItemKind::Trait(_, _, _, _, ref items) = it.kind else {
829 check_on_unimplemented(tcx, it);
831 for item in items.iter() {
832 let item = tcx.hir().trait_item(item.id);
834 hir::TraitItemKind::Fn(ref sig, _) => {
835 let abi = sig.header.abi;
836 fn_maybe_err(tcx, item.ident.span, abi);
838 hir::TraitItemKind::Type(.., Some(default)) => {
839 let assoc_item = tcx.associated_item(item.def_id);
841 InternalSubsts::identity_for_item(tcx, it.def_id.to_def_id());
842 let _: Result<_, rustc_errors::ErrorGuaranteed> = check_type_bounds(
847 ty::TraitRef { def_id: it.def_id.to_def_id(), substs: trait_substs },
855 check_struct(tcx, id.def_id.def_id);
858 check_union(tcx, id.def_id.def_id);
860 DefKind::OpaqueTy => {
861 let item = tcx.hir().item(id);
862 let hir::ItemKind::OpaqueTy(hir::OpaqueTy { origin, .. }) = item.kind else {
865 // HACK(jynelson): trying to infer the type of `impl trait` breaks documenting
866 // `async-std` (and `pub async fn` in general).
867 // Since rustdoc doesn't care about the concrete type behind `impl Trait`, just don't look at it!
868 // See https://github.com/rust-lang/rust/issues/75100
869 if !tcx.sess.opts.actually_rustdoc {
870 let substs = InternalSubsts::identity_for_item(tcx, item.def_id.to_def_id());
871 check_opaque(tcx, item.def_id.def_id, substs, &origin);
874 DefKind::TyAlias => {
875 let pty_ty = tcx.type_of(id.def_id);
876 let generics = tcx.generics_of(id.def_id);
877 check_type_params_are_used(tcx, &generics, pty_ty);
879 DefKind::ForeignMod => {
880 let it = tcx.hir().item(id);
881 let hir::ItemKind::ForeignMod { abi, items } = it.kind else {
884 check_abi(tcx, it.hir_id(), it.span, abi);
886 if abi == Abi::RustIntrinsic {
888 let item = tcx.hir().foreign_item(item.id);
889 intrinsic::check_intrinsic_type(tcx, item);
891 } else if abi == Abi::PlatformIntrinsic {
893 let item = tcx.hir().foreign_item(item.id);
894 intrinsic::check_platform_intrinsic_type(tcx, item);
898 let def_id = item.id.def_id.def_id;
899 let generics = tcx.generics_of(def_id);
900 let own_counts = generics.own_counts();
901 if generics.params.len() - own_counts.lifetimes != 0 {
902 let (kinds, kinds_pl, egs) = match (own_counts.types, own_counts.consts) {
903 (_, 0) => ("type", "types", Some("u32")),
904 // We don't specify an example value, because we can't generate
905 // a valid value for any type.
906 (0, _) => ("const", "consts", None),
907 _ => ("type or const", "types or consts", None),
913 "foreign items may not have {kinds} parameters",
915 .span_label(item.span, &format!("can't have {kinds} parameters"))
917 // FIXME: once we start storing spans for type arguments, turn this
918 // into a suggestion.
920 "replace the {} parameters with concrete {}{}",
923 egs.map(|egs| format!(" like `{}`", egs)).unwrap_or_default(),
929 let item = tcx.hir().foreign_item(item.id);
931 hir::ForeignItemKind::Fn(ref fn_decl, _, _) => {
932 require_c_abi_if_c_variadic(tcx, fn_decl, abi, item.span);
934 hir::ForeignItemKind::Static(..) => {
935 check_static_inhabited(tcx, def_id);
942 DefKind::GlobalAsm => {
943 let it = tcx.hir().item(id);
944 let hir::ItemKind::GlobalAsm(asm) = it.kind else { span_bug!(it.span, "DefKind::GlobalAsm but got {:#?}", it) };
945 InlineAsmCtxt::new_global_asm(tcx).check_asm(asm, id.hir_id());
951 pub(super) fn check_on_unimplemented(tcx: TyCtxt<'_>, item: &hir::Item<'_>) {
952 // an error would be reported if this fails.
953 let _ = traits::OnUnimplementedDirective::of_item(tcx, item.def_id.to_def_id());
956 pub(super) fn check_specialization_validity<'tcx>(
958 trait_def: &ty::TraitDef,
959 trait_item: &ty::AssocItem,
961 impl_item: &hir::ImplItemRef,
963 let Ok(ancestors) = trait_def.ancestors(tcx, impl_id) else { return };
964 let mut ancestor_impls = ancestors.skip(1).filter_map(|parent| {
965 if parent.is_from_trait() {
968 Some((parent, parent.item(tcx, trait_item.def_id)))
972 let opt_result = ancestor_impls.find_map(|(parent_impl, parent_item)| {
974 // Parent impl exists, and contains the parent item we're trying to specialize, but
975 // doesn't mark it `default`.
976 Some(parent_item) if traits::impl_item_is_final(tcx, &parent_item) => {
977 Some(Err(parent_impl.def_id()))
980 // Parent impl contains item and makes it specializable.
981 Some(_) => Some(Ok(())),
983 // Parent impl doesn't mention the item. This means it's inherited from the
984 // grandparent. In that case, if parent is a `default impl`, inherited items use the
985 // "defaultness" from the grandparent, else they are final.
987 if tcx.impl_defaultness(parent_impl.def_id()).is_default() {
990 Some(Err(parent_impl.def_id()))
996 // If `opt_result` is `None`, we have only encountered `default impl`s that don't contain the
997 // item. This is allowed, the item isn't actually getting specialized here.
998 let result = opt_result.unwrap_or(Ok(()));
1000 if let Err(parent_impl) = result {
1001 report_forbidden_specialization(tcx, impl_item, parent_impl);
1005 fn check_impl_items_against_trait<'tcx>(
1007 full_impl_span: Span,
1008 impl_id: LocalDefId,
1009 impl_trait_ref: ty::TraitRef<'tcx>,
1010 impl_item_refs: &[hir::ImplItemRef],
1012 // If the trait reference itself is erroneous (so the compilation is going
1013 // to fail), skip checking the items here -- the `impl_item` table in `tcx`
1014 // isn't populated for such impls.
1015 if impl_trait_ref.references_error() {
1019 // Negative impls are not expected to have any items
1020 match tcx.impl_polarity(impl_id) {
1021 ty::ImplPolarity::Reservation | ty::ImplPolarity::Positive => {}
1022 ty::ImplPolarity::Negative => {
1023 if let [first_item_ref, ..] = impl_item_refs {
1024 let first_item_span = tcx.hir().impl_item(first_item_ref.id).span;
1029 "negative impls cannot have any items"
1037 let trait_def = tcx.trait_def(impl_trait_ref.def_id);
1039 for impl_item in impl_item_refs {
1040 let ty_impl_item = tcx.associated_item(impl_item.id.def_id);
1041 let ty_trait_item = if let Some(trait_item_id) = ty_impl_item.trait_item_def_id {
1042 tcx.associated_item(trait_item_id)
1044 // Checked in `associated_item`.
1045 tcx.sess.delay_span_bug(impl_item.span, "missing associated item in trait");
1048 let impl_item_full = tcx.hir().impl_item(impl_item.id);
1049 match impl_item_full.kind {
1050 hir::ImplItemKind::Const(..) => {
1051 // Find associated const definition.
1060 hir::ImplItemKind::Fn(..) => {
1061 let opt_trait_span = tcx.hir().span_if_local(ty_trait_item.def_id);
1062 compare_impl_method(
1070 hir::ImplItemKind::TyAlias(impl_ty) => {
1071 let opt_trait_span = tcx.hir().span_if_local(ty_trait_item.def_id);
1083 check_specialization_validity(
1087 impl_id.to_def_id(),
1092 if let Ok(ancestors) = trait_def.ancestors(tcx, impl_id.to_def_id()) {
1093 // Check for missing items from trait
1094 let mut missing_items = Vec::new();
1096 let mut must_implement_one_of: Option<&[Ident]> =
1097 trait_def.must_implement_one_of.as_deref();
1099 for &trait_item_id in tcx.associated_item_def_ids(impl_trait_ref.def_id) {
1100 let is_implemented = ancestors
1101 .leaf_def(tcx, trait_item_id)
1102 .map_or(false, |node_item| node_item.item.defaultness(tcx).has_value());
1104 if !is_implemented && tcx.impl_defaultness(impl_id).is_final() {
1105 missing_items.push(tcx.associated_item(trait_item_id));
1108 // true if this item is specifically implemented in this impl
1109 let is_implemented_here = ancestors
1110 .leaf_def(tcx, trait_item_id)
1111 .map_or(false, |node_item| !node_item.defining_node.is_from_trait());
1113 if !is_implemented_here {
1114 match tcx.eval_default_body_stability(trait_item_id, full_impl_span) {
1115 EvalResult::Deny { feature, reason, issue, .. } => default_body_is_unstable(
1124 // Unmarked default bodies are considered stable (at least for now).
1125 EvalResult::Allow | EvalResult::Unmarked => {}
1129 if let Some(required_items) = &must_implement_one_of {
1130 if is_implemented_here {
1131 let trait_item = tcx.associated_item(trait_item_id);
1132 if required_items.contains(&trait_item.ident(tcx)) {
1133 must_implement_one_of = None;
1139 if !missing_items.is_empty() {
1140 missing_items_err(tcx, tcx.def_span(impl_id), &missing_items, full_impl_span);
1143 if let Some(missing_items) = must_implement_one_of {
1145 .get_attr(impl_trait_ref.def_id, sym::rustc_must_implement_one_of)
1146 .map(|attr| attr.span);
1148 missing_items_must_implement_one_of_err(
1150 tcx.def_span(impl_id),
1158 /// Checks whether a type can be represented in memory. In particular, it
1159 /// identifies types that contain themselves without indirection through a
1160 /// pointer, which would mean their size is unbounded.
1161 pub(super) fn check_representable(tcx: TyCtxt<'_>, sp: Span, item_def_id: LocalDefId) -> bool {
1162 let rty = tcx.type_of(item_def_id);
1164 // Check that it is possible to represent this type. This call identifies
1165 // (1) types that contain themselves and (2) types that contain a different
1166 // recursive type. It is only necessary to throw an error on those that
1167 // contain themselves. For case 2, there must be an inner type that will be
1168 // caught by case 1.
1169 match representability::ty_is_representable(tcx, rty, sp, None) {
1170 Representability::SelfRecursive(spans) => {
1171 recursive_type_with_infinite_size_error(tcx, item_def_id.to_def_id(), spans);
1174 Representability::Representable | Representability::ContainsRecursive => (),
1179 pub fn check_simd(tcx: TyCtxt<'_>, sp: Span, def_id: LocalDefId) {
1180 let t = tcx.type_of(def_id);
1181 if let ty::Adt(def, substs) = t.kind()
1184 let fields = &def.non_enum_variant().fields;
1185 if fields.is_empty() {
1186 struct_span_err!(tcx.sess, sp, E0075, "SIMD vector cannot be empty").emit();
1189 let e = fields[0].ty(tcx, substs);
1190 if !fields.iter().all(|f| f.ty(tcx, substs) == e) {
1191 struct_span_err!(tcx.sess, sp, E0076, "SIMD vector should be homogeneous")
1192 .span_label(sp, "SIMD elements must have the same type")
1197 let len = if let ty::Array(_ty, c) = e.kind() {
1198 c.try_eval_usize(tcx, tcx.param_env(def.did()))
1200 Some(fields.len() as u64)
1202 if let Some(len) = len {
1204 struct_span_err!(tcx.sess, sp, E0075, "SIMD vector cannot be empty").emit();
1206 } else if len > MAX_SIMD_LANES {
1211 "SIMD vector cannot have more than {MAX_SIMD_LANES} elements",
1218 // Check that we use types valid for use in the lanes of a SIMD "vector register"
1219 // These are scalar types which directly match a "machine" type
1220 // Yes: Integers, floats, "thin" pointers
1221 // No: char, "fat" pointers, compound types
1223 ty::Param(_) => (), // pass struct<T>(T, T, T, T) through, let monomorphization catch errors
1224 ty::Int(_) | ty::Uint(_) | ty::Float(_) | ty::RawPtr(_) => (), // struct(u8, u8, u8, u8) is ok
1225 ty::Array(t, _) if matches!(t.kind(), ty::Param(_)) => (), // pass struct<T>([T; N]) through, let monomorphization catch errors
1229 ty::Int(_) | ty::Uint(_) | ty::Float(_) | ty::RawPtr(_)
1231 { /* struct([f32; 4]) is ok */ }
1237 "SIMD vector element type should be a \
1238 primitive scalar (integer/float/pointer) type"
1247 pub(super) fn check_packed(tcx: TyCtxt<'_>, sp: Span, def: ty::AdtDef<'_>) {
1248 let repr = def.repr();
1250 for attr in tcx.get_attrs(def.did(), sym::repr) {
1251 for r in attr::parse_repr_attr(&tcx.sess, attr) {
1252 if let attr::ReprPacked(pack) = r
1253 && let Some(repr_pack) = repr.pack
1254 && pack as u64 != repr_pack.bytes()
1260 "type has conflicting packed representation hints"
1266 if repr.align.is_some() {
1271 "type has conflicting packed and align representation hints"
1275 if let Some(def_spans) = check_packed_inner(tcx, def.did(), &mut vec![]) {
1276 let mut err = struct_span_err!(
1280 "packed type cannot transitively contain a `#[repr(align)]` type"
1284 tcx.def_span(def_spans[0].0),
1286 "`{}` has a `#[repr(align)]` attribute",
1287 tcx.item_name(def_spans[0].0)
1291 if def_spans.len() > 2 {
1292 let mut first = true;
1293 for (adt_def, span) in def_spans.iter().skip(1).rev() {
1294 let ident = tcx.item_name(*adt_def);
1299 "`{}` contains a field of type `{}`",
1300 tcx.type_of(def.did()),
1304 format!("...which contains a field of type `{ident}`")
1317 pub(super) fn check_packed_inner(
1320 stack: &mut Vec<DefId>,
1321 ) -> Option<Vec<(DefId, Span)>> {
1322 if let ty::Adt(def, substs) = tcx.type_of(def_id).kind() {
1323 if def.is_struct() || def.is_union() {
1324 if def.repr().align.is_some() {
1325 return Some(vec![(def.did(), DUMMY_SP)]);
1329 for field in &def.non_enum_variant().fields {
1330 if let ty::Adt(def, _) = field.ty(tcx, substs).kind()
1331 && !stack.contains(&def.did())
1332 && let Some(mut defs) = check_packed_inner(tcx, def.did(), stack)
1334 defs.push((def.did(), field.ident(tcx).span));
1345 pub(super) fn check_transparent<'tcx>(tcx: TyCtxt<'tcx>, sp: Span, adt: ty::AdtDef<'tcx>) {
1346 if !adt.repr().transparent() {
1350 if adt.is_union() && !tcx.features().transparent_unions {
1352 &tcx.sess.parse_sess,
1353 sym::transparent_unions,
1355 "transparent unions are unstable",
1360 if adt.variants().len() != 1 {
1361 bad_variant_count(tcx, adt, sp, adt.did());
1362 if adt.variants().is_empty() {
1363 // Don't bother checking the fields. No variants (and thus no fields) exist.
1368 // For each field, figure out if it's known to be a ZST and align(1), with "known"
1369 // respecting #[non_exhaustive] attributes.
1370 let field_infos = adt.all_fields().map(|field| {
1371 let ty = field.ty(tcx, InternalSubsts::identity_for_item(tcx, field.did));
1372 let param_env = tcx.param_env(field.did);
1373 let layout = tcx.layout_of(param_env.and(ty));
1374 // We are currently checking the type this field came from, so it must be local
1375 let span = tcx.hir().span_if_local(field.did).unwrap();
1376 let zst = layout.map_or(false, |layout| layout.is_zst());
1377 let align1 = layout.map_or(false, |layout| layout.align.abi.bytes() == 1);
1379 return (span, zst, align1, None);
1382 fn check_non_exhaustive<'tcx>(
1385 ) -> ControlFlow<(&'static str, DefId, SubstsRef<'tcx>, bool)> {
1387 ty::Tuple(list) => list.iter().try_for_each(|t| check_non_exhaustive(tcx, t)),
1388 ty::Array(ty, _) => check_non_exhaustive(tcx, *ty),
1389 ty::Adt(def, subst) => {
1390 if !def.did().is_local() {
1391 let non_exhaustive = def.is_variant_list_non_exhaustive()
1395 .any(ty::VariantDef::is_field_list_non_exhaustive);
1396 let has_priv = def.all_fields().any(|f| !f.vis.is_public());
1397 if non_exhaustive || has_priv {
1398 return ControlFlow::Break((
1407 .map(|field| field.ty(tcx, subst))
1408 .try_for_each(|t| check_non_exhaustive(tcx, t))
1410 _ => ControlFlow::Continue(()),
1414 (span, zst, align1, check_non_exhaustive(tcx, ty).break_value())
1417 let non_zst_fields = field_infos
1419 .filter_map(|(span, zst, _align1, _non_exhaustive)| if !zst { Some(span) } else { None });
1420 let non_zst_count = non_zst_fields.clone().count();
1421 if non_zst_count >= 2 {
1422 bad_non_zero_sized_fields(tcx, adt, non_zst_count, non_zst_fields, sp);
1424 let incompatible_zst_fields =
1425 field_infos.clone().filter(|(_, _, _, opt)| opt.is_some()).count();
1426 let incompat = incompatible_zst_fields + non_zst_count >= 2 && non_zst_count < 2;
1427 for (span, zst, align1, non_exhaustive) in field_infos {
1433 "zero-sized field in transparent {} has alignment larger than 1",
1436 .span_label(span, "has alignment larger than 1")
1439 if incompat && let Some((descr, def_id, substs, non_exhaustive)) = non_exhaustive {
1440 tcx.struct_span_lint_hir(
1441 REPR_TRANSPARENT_EXTERNAL_PRIVATE_FIELDS,
1442 tcx.hir().local_def_id_to_hir_id(adt.did().expect_local()),
1444 "zero-sized fields in `repr(transparent)` cannot contain external non-exhaustive types",
1446 let note = if non_exhaustive {
1447 "is marked with `#[non_exhaustive]`"
1449 "contains private fields"
1451 let field_ty = tcx.def_path_str_with_substs(def_id, substs);
1453 .note(format!("this {descr} contains `{field_ty}`, which {note}, \
1454 and makes it not a breaking change to become non-zero-sized in the future."))
1461 #[allow(trivial_numeric_casts)]
1462 fn check_enum<'tcx>(tcx: TyCtxt<'tcx>, vs: &'tcx [hir::Variant<'tcx>], def_id: LocalDefId) {
1463 let def = tcx.adt_def(def_id);
1464 let sp = tcx.def_span(def_id);
1465 def.destructor(tcx); // force the destructor to be evaluated
1468 if let Some(attr) = tcx.get_attrs(def_id.to_def_id(), sym::repr).next() {
1473 "unsupported representation for zero-variant enum"
1475 .span_label(sp, "zero-variant enum")
1480 let repr_type_ty = def.repr().discr_type().to_ty(tcx);
1481 if repr_type_ty == tcx.types.i128 || repr_type_ty == tcx.types.u128 {
1482 if !tcx.features().repr128 {
1484 &tcx.sess.parse_sess,
1487 "repr with 128-bit type is unstable",
1494 if let Some(ref e) = v.disr_expr {
1495 tcx.ensure().typeck(tcx.hir().local_def_id(e.hir_id));
1499 if tcx.adt_def(def_id).repr().int.is_none() && tcx.features().arbitrary_enum_discriminant {
1500 let is_unit = |var: &hir::Variant<'_>| matches!(var.data, hir::VariantData::Unit(..));
1502 let has_disr = |var: &hir::Variant<'_>| var.disr_expr.is_some();
1503 let has_non_units = vs.iter().any(|var| !is_unit(var));
1504 let disr_units = vs.iter().any(|var| is_unit(&var) && has_disr(&var));
1505 let disr_non_unit = vs.iter().any(|var| !is_unit(&var) && has_disr(&var));
1507 if disr_non_unit || (disr_units && has_non_units) {
1509 struct_span_err!(tcx.sess, sp, E0732, "`#[repr(inttype)]` must be specified");
1514 detect_discriminant_duplicate(tcx, def.discriminants(tcx).collect(), vs, sp);
1516 check_representable(tcx, sp, def_id);
1517 check_transparent(tcx, sp, def);
1520 /// Part of enum check. Given the discriminants of an enum, errors if two or more discriminants are equal
1521 fn detect_discriminant_duplicate<'tcx>(
1523 mut discrs: Vec<(VariantIdx, Discr<'tcx>)>,
1524 vs: &'tcx [hir::Variant<'tcx>],
1527 // Helper closure to reduce duplicate code. This gets called everytime we detect a duplicate.
1528 // Here `idx` refers to the order of which the discriminant appears, and its index in `vs`
1529 let report = |dis: Discr<'tcx>, idx: usize, err: &mut Diagnostic| {
1530 let var = &vs[idx]; // HIR for the duplicate discriminant
1531 let (span, display_discr) = match var.disr_expr {
1533 // In the case the discriminant is both a duplicate and overflowed, let the user know
1534 if let hir::ExprKind::Lit(lit) = &tcx.hir().body(expr.body).value.kind
1535 && let rustc_ast::LitKind::Int(lit_value, _int_kind) = &lit.node
1536 && *lit_value != dis.val
1538 (tcx.hir().span(expr.hir_id), format!("`{dis}` (overflowed from `{lit_value}`)"))
1539 // Otherwise, format the value as-is
1541 (tcx.hir().span(expr.hir_id), format!("`{dis}`"))
1545 // At this point we know this discriminant is a duplicate, and was not explicitly
1546 // assigned by the user. Here we iterate backwards to fetch the HIR for the last
1547 // explicitly assigned discriminant, and letting the user know that this was the
1548 // increment startpoint, and how many steps from there leading to the duplicate
1549 if let Some((n, hir::Variant { span, ident, .. })) =
1550 vs[..idx].iter().rev().enumerate().find(|v| v.1.disr_expr.is_some())
1552 let ve_ident = var.ident;
1554 let sp = if n > 1 { "variants" } else { "variant" };
1558 format!("discriminant for `{ve_ident}` incremented from this startpoint (`{ident}` + {n} {sp} later => `{ve_ident}` = {dis})"),
1562 (vs[idx].span, format!("`{dis}`"))
1566 err.span_label(span, format!("{display_discr} assigned here"));
1569 // Here we loop through the discriminants, comparing each discriminant to another.
1570 // When a duplicate is detected, we instantiate an error and point to both
1571 // initial and duplicate value. The duplicate discriminant is then discarded by swapping
1572 // it with the last element and decrementing the `vec.len` (which is why we have to evaluate
1573 // `discrs.len()` anew every iteration, and why this could be tricky to do in a functional
1574 // style as we are mutating `discrs` on the fly).
1576 while i < discrs.len() {
1577 let hir_var_i_idx = discrs[i].0.index();
1578 let mut error: Option<DiagnosticBuilder<'_, _>> = None;
1581 while o < discrs.len() {
1582 let hir_var_o_idx = discrs[o].0.index();
1584 if discrs[i].1.val == discrs[o].1.val {
1585 let err = error.get_or_insert_with(|| {
1586 let mut ret = struct_span_err!(
1590 "discriminant value `{}` assigned more than once",
1594 report(discrs[i].1, hir_var_i_idx, &mut ret);
1599 report(discrs[o].1, hir_var_o_idx, err);
1601 // Safe to unwrap here, as we wouldn't reach this point if `discrs` was empty
1602 discrs[o] = *discrs.last().unwrap();
1609 if let Some(mut e) = error {
1617 pub(super) fn check_type_params_are_used<'tcx>(
1619 generics: &ty::Generics,
1622 debug!("check_type_params_are_used(generics={:?}, ty={:?})", generics, ty);
1624 assert_eq!(generics.parent, None);
1626 if generics.own_counts().types == 0 {
1630 let mut params_used = BitSet::new_empty(generics.params.len());
1632 if ty.references_error() {
1633 // If there is already another error, do not emit
1634 // an error for not using a type parameter.
1635 assert!(tcx.sess.has_errors().is_some());
1639 for leaf in ty.walk() {
1640 if let GenericArgKind::Type(leaf_ty) = leaf.unpack()
1641 && let ty::Param(param) = leaf_ty.kind()
1643 debug!("found use of ty param {:?}", param);
1644 params_used.insert(param.index);
1648 for param in &generics.params {
1649 if !params_used.contains(param.index)
1650 && let ty::GenericParamDefKind::Type { .. } = param.kind
1652 let span = tcx.def_span(param.def_id);
1657 "type parameter `{}` is unused",
1660 .span_label(span, "unused type parameter")
1666 pub(super) fn check_mod_item_types(tcx: TyCtxt<'_>, module_def_id: LocalDefId) {
1667 let module = tcx.hir_module_items(module_def_id);
1668 for id in module.items() {
1669 check_item_type(tcx, id);
1673 fn async_opaque_type_cycle_error(tcx: TyCtxt<'_>, span: Span) -> ErrorGuaranteed {
1674 struct_span_err!(tcx.sess, span, E0733, "recursion in an `async fn` requires boxing")
1675 .span_label(span, "recursive `async fn`")
1676 .note("a recursive `async fn` must be rewritten to return a boxed `dyn Future`")
1678 "consider using the `async_recursion` crate: https://crates.io/crates/async_recursion",
1683 /// Emit an error for recursive opaque types.
1685 /// If this is a return `impl Trait`, find the item's return expressions and point at them. For
1686 /// direct recursion this is enough, but for indirect recursion also point at the last intermediary
1689 /// If all the return expressions evaluate to `!`, then we explain that the error will go away
1690 /// after changing it. This can happen when a user uses `panic!()` or similar as a placeholder.
1691 fn opaque_type_cycle_error(tcx: TyCtxt<'_>, def_id: LocalDefId, span: Span) -> ErrorGuaranteed {
1692 let mut err = struct_span_err!(tcx.sess, span, E0720, "cannot resolve opaque type");
1694 let mut label = false;
1695 if let Some((def_id, visitor)) = get_owner_return_paths(tcx, def_id) {
1696 let typeck_results = tcx.typeck(def_id);
1700 .filter_map(|expr| typeck_results.node_type_opt(expr.hir_id))
1701 .all(|ty| matches!(ty.kind(), ty::Never))
1706 .filter(|expr| typeck_results.node_type_opt(expr.hir_id).is_some())
1707 .map(|expr| expr.span)
1708 .collect::<Vec<Span>>();
1709 let span_len = spans.len();
1711 err.span_label(spans[0], "this returned value is of `!` type");
1713 let mut multispan: MultiSpan = spans.clone().into();
1715 multispan.push_span_label(span, "this returned value is of `!` type");
1717 err.span_note(multispan, "these returned values have a concrete \"never\" type");
1719 err.help("this error will resolve once the item's body returns a concrete type");
1721 let mut seen = FxHashSet::default();
1723 err.span_label(span, "recursive opaque type");
1725 for (sp, ty) in visitor
1728 .filter_map(|e| typeck_results.node_type_opt(e.hir_id).map(|t| (e.span, t)))
1729 .filter(|(_, ty)| !matches!(ty.kind(), ty::Never))
1731 struct OpaqueTypeCollector(Vec<DefId>);
1732 impl<'tcx> ty::visit::TypeVisitor<'tcx> for OpaqueTypeCollector {
1733 fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
1735 ty::Opaque(def, _) => {
1737 ControlFlow::CONTINUE
1739 _ => t.super_visit_with(self),
1743 let mut visitor = OpaqueTypeCollector(vec![]);
1744 ty.visit_with(&mut visitor);
1745 for def_id in visitor.0 {
1746 let ty_span = tcx.def_span(def_id);
1747 if !seen.contains(&ty_span) {
1748 err.span_label(ty_span, &format!("returning this opaque type `{ty}`"));
1749 seen.insert(ty_span);
1751 err.span_label(sp, &format!("returning here with type `{ty}`"));
1757 err.span_label(span, "cannot resolve opaque type");