| //! Check properties that are required by built-in traits and set |
| //! up data structures required by type-checking/codegen. |
| |
| use std::assert_matches::assert_matches; |
| use std::collections::BTreeMap; |
| |
| use rustc_data_structures::fx::FxHashSet; |
| use rustc_errors::{ErrorGuaranteed, MultiSpan}; |
| use rustc_hir as hir; |
| use rustc_hir::ItemKind; |
| use rustc_hir::def_id::{DefId, LocalDefId}; |
| use rustc_hir::lang_items::LangItem; |
| use rustc_infer::infer::outlives::env::OutlivesEnvironment; |
| use rustc_infer::infer::{self, RegionResolutionError, TyCtxtInferExt}; |
| use rustc_infer::traits::Obligation; |
| use rustc_middle::ty::adjustment::CoerceUnsizedInfo; |
| use rustc_middle::ty::print::PrintTraitRefExt as _; |
| use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitableExt, suggest_constraining_type_params}; |
| use rustc_span::{DUMMY_SP, Span}; |
| use rustc_trait_selection::error_reporting::InferCtxtErrorExt; |
| use rustc_trait_selection::traits::misc::{ |
| ConstParamTyImplementationError, CopyImplementationError, InfringingFieldsReason, |
| type_allowed_to_implement_const_param_ty, type_allowed_to_implement_copy, |
| }; |
| use rustc_trait_selection::traits::{self, ObligationCause, ObligationCtxt}; |
| use tracing::debug; |
| |
| use crate::errors; |
| |
| pub(super) fn check_trait<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| trait_def_id: DefId, |
| impl_def_id: LocalDefId, |
| impl_header: ty::ImplTraitHeader<'tcx>, |
| ) -> Result<(), ErrorGuaranteed> { |
| let lang_items = tcx.lang_items(); |
| let checker = Checker { tcx, trait_def_id, impl_def_id, impl_header }; |
| let mut res = checker.check(lang_items.drop_trait(), visit_implementation_of_drop); |
| res = res.and(checker.check(lang_items.copy_trait(), visit_implementation_of_copy)); |
| res = res.and(checker.check(lang_items.const_param_ty_trait(), |checker| { |
| visit_implementation_of_const_param_ty(checker, LangItem::ConstParamTy) |
| })); |
| res = res.and(checker.check(lang_items.unsized_const_param_ty_trait(), |checker| { |
| visit_implementation_of_const_param_ty(checker, LangItem::UnsizedConstParamTy) |
| })); |
| |
| res = res.and( |
| checker.check(lang_items.coerce_unsized_trait(), visit_implementation_of_coerce_unsized), |
| ); |
| res.and( |
| checker |
| .check(lang_items.dispatch_from_dyn_trait(), visit_implementation_of_dispatch_from_dyn), |
| ) |
| } |
| |
| struct Checker<'tcx> { |
| tcx: TyCtxt<'tcx>, |
| trait_def_id: DefId, |
| impl_def_id: LocalDefId, |
| impl_header: ty::ImplTraitHeader<'tcx>, |
| } |
| |
| impl<'tcx> Checker<'tcx> { |
| fn check( |
| &self, |
| trait_def_id: Option<DefId>, |
| f: impl FnOnce(&Self) -> Result<(), ErrorGuaranteed>, |
| ) -> Result<(), ErrorGuaranteed> { |
| if Some(self.trait_def_id) == trait_def_id { f(self) } else { Ok(()) } |
| } |
| } |
| |
| fn visit_implementation_of_drop(checker: &Checker<'_>) -> Result<(), ErrorGuaranteed> { |
| let tcx = checker.tcx; |
| let impl_did = checker.impl_def_id; |
| // Destructors only work on local ADT types. |
| match checker.impl_header.trait_ref.instantiate_identity().self_ty().kind() { |
| ty::Adt(def, _) if def.did().is_local() => return Ok(()), |
| ty::Error(_) => return Ok(()), |
| _ => {} |
| } |
| |
| let impl_ = tcx.hir().expect_item(impl_did).expect_impl(); |
| |
| Err(tcx.dcx().emit_err(errors::DropImplOnWrongItem { span: impl_.self_ty.span })) |
| } |
| |
| fn visit_implementation_of_copy(checker: &Checker<'_>) -> Result<(), ErrorGuaranteed> { |
| let tcx = checker.tcx; |
| let impl_header = checker.impl_header; |
| let impl_did = checker.impl_def_id; |
| debug!("visit_implementation_of_copy: impl_did={:?}", impl_did); |
| |
| let self_type = impl_header.trait_ref.instantiate_identity().self_ty(); |
| debug!("visit_implementation_of_copy: self_type={:?} (bound)", self_type); |
| |
| let param_env = tcx.param_env(impl_did); |
| assert!(!self_type.has_escaping_bound_vars()); |
| |
| debug!("visit_implementation_of_copy: self_type={:?} (free)", self_type); |
| |
| if let ty::ImplPolarity::Negative = impl_header.polarity { |
| return Ok(()); |
| } |
| |
| let cause = traits::ObligationCause::misc(DUMMY_SP, impl_did); |
| match type_allowed_to_implement_copy(tcx, param_env, self_type, cause) { |
| Ok(()) => Ok(()), |
| Err(CopyImplementationError::InfringingFields(fields)) => { |
| let span = tcx.hir().expect_item(impl_did).expect_impl().self_ty.span; |
| Err(infringing_fields_error( |
| tcx, |
| fields.into_iter().map(|(field, ty, reason)| (tcx.def_span(field.did), ty, reason)), |
| LangItem::Copy, |
| impl_did, |
| span, |
| )) |
| } |
| Err(CopyImplementationError::NotAnAdt) => { |
| let span = tcx.hir().expect_item(impl_did).expect_impl().self_ty.span; |
| Err(tcx.dcx().emit_err(errors::CopyImplOnNonAdt { span })) |
| } |
| Err(CopyImplementationError::HasDestructor) => { |
| let span = tcx.hir().expect_item(impl_did).expect_impl().self_ty.span; |
| Err(tcx.dcx().emit_err(errors::CopyImplOnTypeWithDtor { span })) |
| } |
| } |
| } |
| |
| fn visit_implementation_of_const_param_ty( |
| checker: &Checker<'_>, |
| kind: LangItem, |
| ) -> Result<(), ErrorGuaranteed> { |
| assert_matches!(kind, LangItem::ConstParamTy | LangItem::UnsizedConstParamTy); |
| |
| let tcx = checker.tcx; |
| let header = checker.impl_header; |
| let impl_did = checker.impl_def_id; |
| let self_type = header.trait_ref.instantiate_identity().self_ty(); |
| assert!(!self_type.has_escaping_bound_vars()); |
| |
| let param_env = tcx.param_env(impl_did); |
| |
| if let ty::ImplPolarity::Negative | ty::ImplPolarity::Reservation = header.polarity { |
| return Ok(()); |
| } |
| |
| let cause = traits::ObligationCause::misc(DUMMY_SP, impl_did); |
| match type_allowed_to_implement_const_param_ty(tcx, param_env, self_type, kind, cause) { |
| Ok(()) => Ok(()), |
| Err(ConstParamTyImplementationError::InfrigingFields(fields)) => { |
| let span = tcx.hir().expect_item(impl_did).expect_impl().self_ty.span; |
| Err(infringing_fields_error( |
| tcx, |
| fields.into_iter().map(|(field, ty, reason)| (tcx.def_span(field.did), ty, reason)), |
| LangItem::ConstParamTy, |
| impl_did, |
| span, |
| )) |
| } |
| Err(ConstParamTyImplementationError::NotAnAdtOrBuiltinAllowed) => { |
| let span = tcx.hir().expect_item(impl_did).expect_impl().self_ty.span; |
| Err(tcx.dcx().emit_err(errors::ConstParamTyImplOnNonAdt { span })) |
| } |
| Err(ConstParamTyImplementationError::InvalidInnerTyOfBuiltinTy(infringing_tys)) => { |
| let span = tcx.hir().expect_item(impl_did).expect_impl().self_ty.span; |
| Err(infringing_fields_error( |
| tcx, |
| infringing_tys.into_iter().map(|(ty, reason)| (span, ty, reason)), |
| LangItem::ConstParamTy, |
| impl_did, |
| span, |
| )) |
| } |
| Err(ConstParamTyImplementationError::UnsizedConstParamsFeatureRequired) => { |
| let span = tcx.hir().expect_item(impl_did).expect_impl().self_ty.span; |
| Err(tcx.dcx().emit_err(errors::ConstParamTyImplOnUnsized { span })) |
| } |
| } |
| } |
| |
| fn visit_implementation_of_coerce_unsized(checker: &Checker<'_>) -> Result<(), ErrorGuaranteed> { |
| let tcx = checker.tcx; |
| let impl_did = checker.impl_def_id; |
| debug!("visit_implementation_of_coerce_unsized: impl_did={:?}", impl_did); |
| |
| // Just compute this for the side-effects, in particular reporting |
| // errors; other parts of the code may demand it for the info of |
| // course. |
| let span = tcx.def_span(impl_did); |
| tcx.at(span).ensure().coerce_unsized_info(impl_did) |
| } |
| |
| fn visit_implementation_of_dispatch_from_dyn(checker: &Checker<'_>) -> Result<(), ErrorGuaranteed> { |
| let tcx = checker.tcx; |
| let impl_did = checker.impl_def_id; |
| let trait_ref = checker.impl_header.trait_ref.instantiate_identity(); |
| debug!("visit_implementation_of_dispatch_from_dyn: impl_did={:?}", impl_did); |
| |
| let span = tcx.def_span(impl_did); |
| |
| let dispatch_from_dyn_trait = tcx.require_lang_item(LangItem::DispatchFromDyn, Some(span)); |
| |
| let source = trait_ref.self_ty(); |
| assert!(!source.has_escaping_bound_vars()); |
| let target = { |
| assert_eq!(trait_ref.def_id, dispatch_from_dyn_trait); |
| |
| trait_ref.args.type_at(1) |
| }; |
| |
| debug!("visit_implementation_of_dispatch_from_dyn: {:?} -> {:?}", source, target); |
| |
| let param_env = tcx.param_env(impl_did); |
| |
| let infcx = tcx.infer_ctxt().build(); |
| let cause = ObligationCause::misc(span, impl_did); |
| |
| // Later parts of the compiler rely on all DispatchFromDyn types to be ABI-compatible with raw |
| // pointers. This is enforced here: we only allow impls for references, raw pointers, and things |
| // that are effectively repr(transparent) newtypes around types that already hav a |
| // DispatchedFromDyn impl. We cannot literally use repr(transparent) on those types since some |
| // of them support an allocator, but we ensure that for the cases where the type implements this |
| // trait, they *do* satisfy the repr(transparent) rules, and then we assume that everything else |
| // in the compiler (in particular, all the call ABI logic) will treat them as repr(transparent) |
| // even if they do not carry that attribute. |
| use rustc_type_ir::TyKind::*; |
| match (source.kind(), target.kind()) { |
| (&Ref(r_a, _, mutbl_a), Ref(r_b, _, mutbl_b)) if r_a == *r_b && mutbl_a == *mutbl_b => { |
| Ok(()) |
| } |
| (&RawPtr(_, a_mutbl), &RawPtr(_, b_mutbl)) if a_mutbl == b_mutbl => Ok(()), |
| (&Adt(def_a, args_a), &Adt(def_b, args_b)) if def_a.is_struct() && def_b.is_struct() => { |
| if def_a != def_b { |
| let source_path = tcx.def_path_str(def_a.did()); |
| let target_path = tcx.def_path_str(def_b.did()); |
| |
| return Err(tcx.dcx().emit_err(errors::DispatchFromDynCoercion { |
| span, |
| trait_name: "DispatchFromDyn", |
| note: true, |
| source_path, |
| target_path, |
| })); |
| } |
| |
| let mut res = Ok(()); |
| if def_a.repr().c() || def_a.repr().packed() { |
| res = Err(tcx.dcx().emit_err(errors::DispatchFromDynRepr { span })); |
| } |
| |
| let fields = &def_a.non_enum_variant().fields; |
| |
| let coerced_fields = fields |
| .iter() |
| .filter(|field| { |
| let ty_a = field.ty(tcx, args_a); |
| let ty_b = field.ty(tcx, args_b); |
| |
| if let Ok(layout) = tcx.layout_of(param_env.and(ty_a)) { |
| if layout.is_1zst() { |
| // ignore 1-ZST fields |
| return false; |
| } |
| } |
| |
| if ty_a == ty_b { |
| res = Err(tcx.dcx().emit_err(errors::DispatchFromDynZST { |
| span, |
| name: field.name, |
| ty: ty_a, |
| })); |
| |
| return false; |
| } |
| |
| true |
| }) |
| .collect::<Vec<_>>(); |
| |
| if coerced_fields.is_empty() { |
| res = Err(tcx.dcx().emit_err(errors::DispatchFromDynSingle { |
| span, |
| trait_name: "DispatchFromDyn", |
| note: true, |
| })); |
| } else if coerced_fields.len() > 1 { |
| res = Err(tcx.dcx().emit_err(errors::DispatchFromDynMulti { |
| span, |
| coercions_note: true, |
| number: coerced_fields.len(), |
| coercions: coerced_fields |
| .iter() |
| .map(|field| { |
| format!( |
| "`{}` (`{}` to `{}`)", |
| field.name, |
| field.ty(tcx, args_a), |
| field.ty(tcx, args_b), |
| ) |
| }) |
| .collect::<Vec<_>>() |
| .join(", "), |
| })); |
| } else { |
| let ocx = ObligationCtxt::new_with_diagnostics(&infcx); |
| for field in coerced_fields { |
| ocx.register_obligation(Obligation::new( |
| tcx, |
| cause.clone(), |
| param_env, |
| ty::TraitRef::new(tcx, dispatch_from_dyn_trait, [ |
| field.ty(tcx, args_a), |
| field.ty(tcx, args_b), |
| ]), |
| )); |
| } |
| let errors = ocx.select_all_or_error(); |
| if !errors.is_empty() { |
| res = Err(infcx.err_ctxt().report_fulfillment_errors(errors)); |
| } |
| |
| // Finally, resolve all regions. |
| let outlives_env = OutlivesEnvironment::new(param_env); |
| res = res.and(ocx.resolve_regions_and_report_errors(impl_did, &outlives_env)); |
| } |
| res |
| } |
| _ => Err(tcx |
| .dcx() |
| .emit_err(errors::CoerceUnsizedMay { span, trait_name: "DispatchFromDyn" })), |
| } |
| } |
| |
| pub(crate) fn coerce_unsized_info<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| impl_did: LocalDefId, |
| ) -> Result<CoerceUnsizedInfo, ErrorGuaranteed> { |
| debug!("compute_coerce_unsized_info(impl_did={:?})", impl_did); |
| let span = tcx.def_span(impl_did); |
| |
| let coerce_unsized_trait = tcx.require_lang_item(LangItem::CoerceUnsized, Some(span)); |
| |
| let unsize_trait = tcx.require_lang_item(LangItem::Unsize, Some(span)); |
| |
| let source = tcx.type_of(impl_did).instantiate_identity(); |
| let trait_ref = tcx.impl_trait_ref(impl_did).unwrap().instantiate_identity(); |
| assert_eq!(trait_ref.def_id, coerce_unsized_trait); |
| let target = trait_ref.args.type_at(1); |
| debug!("visit_implementation_of_coerce_unsized: {:?} -> {:?} (bound)", source, target); |
| |
| let param_env = tcx.param_env(impl_did); |
| assert!(!source.has_escaping_bound_vars()); |
| |
| debug!("visit_implementation_of_coerce_unsized: {:?} -> {:?} (free)", source, target); |
| |
| let infcx = tcx.infer_ctxt().build(); |
| let cause = ObligationCause::misc(span, impl_did); |
| let check_mutbl = |mt_a: ty::TypeAndMut<'tcx>, |
| mt_b: ty::TypeAndMut<'tcx>, |
| mk_ptr: &dyn Fn(Ty<'tcx>) -> Ty<'tcx>| { |
| if mt_a.mutbl < mt_b.mutbl { |
| infcx |
| .err_ctxt() |
| .report_mismatched_types( |
| &cause, |
| param_env, |
| mk_ptr(mt_b.ty), |
| target, |
| ty::error::TypeError::Mutability, |
| ) |
| .emit(); |
| } |
| (mt_a.ty, mt_b.ty, unsize_trait, None) |
| }; |
| let (source, target, trait_def_id, kind) = match (source.kind(), target.kind()) { |
| (&ty::Ref(r_a, ty_a, mutbl_a), &ty::Ref(r_b, ty_b, mutbl_b)) => { |
| infcx.sub_regions(infer::RelateObjectBound(span), r_b, r_a); |
| let mt_a = ty::TypeAndMut { ty: ty_a, mutbl: mutbl_a }; |
| let mt_b = ty::TypeAndMut { ty: ty_b, mutbl: mutbl_b }; |
| check_mutbl(mt_a, mt_b, &|ty| Ty::new_imm_ref(tcx, r_b, ty)) |
| } |
| |
| (&ty::Ref(_, ty_a, mutbl_a), &ty::RawPtr(ty_b, mutbl_b)) => check_mutbl( |
| ty::TypeAndMut { ty: ty_a, mutbl: mutbl_a }, |
| ty::TypeAndMut { ty: ty_b, mutbl: mutbl_b }, |
| &|ty| Ty::new_imm_ptr(tcx, ty), |
| ), |
| |
| (&ty::RawPtr(ty_a, mutbl_a), &ty::RawPtr(ty_b, mutbl_b)) => check_mutbl( |
| ty::TypeAndMut { ty: ty_a, mutbl: mutbl_a }, |
| ty::TypeAndMut { ty: ty_b, mutbl: mutbl_b }, |
| &|ty| Ty::new_imm_ptr(tcx, ty), |
| ), |
| |
| (&ty::Adt(def_a, args_a), &ty::Adt(def_b, args_b)) |
| if def_a.is_struct() && def_b.is_struct() => |
| { |
| if def_a != def_b { |
| let source_path = tcx.def_path_str(def_a.did()); |
| let target_path = tcx.def_path_str(def_b.did()); |
| return Err(tcx.dcx().emit_err(errors::DispatchFromDynSame { |
| span, |
| trait_name: "CoerceUnsized", |
| note: true, |
| source_path, |
| target_path, |
| })); |
| } |
| |
| // Here we are considering a case of converting |
| // `S<P0...Pn>` to `S<Q0...Qn>`. As an example, let's imagine a struct `Foo<T, U>`, |
| // which acts like a pointer to `U`, but carries along some extra data of type `T`: |
| // |
| // struct Foo<T, U> { |
| // extra: T, |
| // ptr: *mut U, |
| // } |
| // |
| // We might have an impl that allows (e.g.) `Foo<T, [i32; 3]>` to be unsized |
| // to `Foo<T, [i32]>`. That impl would look like: |
| // |
| // impl<T, U: Unsize<V>, V> CoerceUnsized<Foo<T, V>> for Foo<T, U> {} |
| // |
| // Here `U = [i32; 3]` and `V = [i32]`. At runtime, |
| // when this coercion occurs, we would be changing the |
| // field `ptr` from a thin pointer of type `*mut [i32; |
| // 3]` to a wide pointer of type `*mut [i32]` (with |
| // extra data `3`). **The purpose of this check is to |
| // make sure that we know how to do this conversion.** |
| // |
| // To check if this impl is legal, we would walk down |
| // the fields of `Foo` and consider their types with |
| // both generic parameters. We are looking to find that |
| // exactly one (non-phantom) field has changed its |
| // type, which we will expect to be the pointer that |
| // is becoming fat (we could probably generalize this |
| // to multiple thin pointers of the same type becoming |
| // fat, but we don't). In this case: |
| // |
| // - `extra` has type `T` before and type `T` after |
| // - `ptr` has type `*mut U` before and type `*mut V` after |
| // |
| // Since just one field changed, we would then check |
| // that `*mut U: CoerceUnsized<*mut V>` is implemented |
| // (in other words, that we know how to do this |
| // conversion). This will work out because `U: |
| // Unsize<V>`, and we have a builtin rule that `*mut |
| // U` can be coerced to `*mut V` if `U: Unsize<V>`. |
| let fields = &def_a.non_enum_variant().fields; |
| let diff_fields = fields |
| .iter_enumerated() |
| .filter_map(|(i, f)| { |
| let (a, b) = (f.ty(tcx, args_a), f.ty(tcx, args_b)); |
| |
| if tcx.type_of(f.did).instantiate_identity().is_phantom_data() { |
| // Ignore PhantomData fields |
| return None; |
| } |
| |
| // Ignore fields that aren't changed; it may |
| // be that we could get away with subtyping or |
| // something more accepting, but we use |
| // equality because we want to be able to |
| // perform this check without computing |
| // variance or constraining opaque types' hidden types. |
| // (This is because we may have to evaluate constraint |
| // expressions in the course of execution.) |
| // See e.g., #41936. |
| if a == b { |
| return None; |
| } |
| |
| // Collect up all fields that were significantly changed |
| // i.e., those that contain T in coerce_unsized T -> U |
| Some((i, a, b)) |
| }) |
| .collect::<Vec<_>>(); |
| |
| if diff_fields.is_empty() { |
| return Err(tcx.dcx().emit_err(errors::CoerceUnsizedOneField { |
| span, |
| trait_name: "CoerceUnsized", |
| note: true, |
| })); |
| } else if diff_fields.len() > 1 { |
| let item = tcx.hir().expect_item(impl_did); |
| let span = if let ItemKind::Impl(hir::Impl { of_trait: Some(t), .. }) = &item.kind { |
| t.path.span |
| } else { |
| tcx.def_span(impl_did) |
| }; |
| |
| return Err(tcx.dcx().emit_err(errors::CoerceUnsizedMulti { |
| span, |
| coercions_note: true, |
| number: diff_fields.len(), |
| coercions: diff_fields |
| .iter() |
| .map(|&(i, a, b)| format!("`{}` (`{}` to `{}`)", fields[i].name, a, b)) |
| .collect::<Vec<_>>() |
| .join(", "), |
| })); |
| } |
| |
| let (i, a, b) = diff_fields[0]; |
| let kind = ty::adjustment::CustomCoerceUnsized::Struct(i); |
| (a, b, coerce_unsized_trait, Some(kind)) |
| } |
| |
| _ => { |
| return Err(tcx |
| .dcx() |
| .emit_err(errors::DispatchFromDynStruct { span, trait_name: "CoerceUnsized" })); |
| } |
| }; |
| |
| // Register an obligation for `A: Trait<B>`. |
| let ocx = ObligationCtxt::new_with_diagnostics(&infcx); |
| let cause = traits::ObligationCause::misc(span, impl_did); |
| let obligation = Obligation::new( |
| tcx, |
| cause, |
| param_env, |
| ty::TraitRef::new(tcx, trait_def_id, [source, target]), |
| ); |
| ocx.register_obligation(obligation); |
| let errors = ocx.select_all_or_error(); |
| if !errors.is_empty() { |
| infcx.err_ctxt().report_fulfillment_errors(errors); |
| } |
| |
| // Finally, resolve all regions. |
| let outlives_env = OutlivesEnvironment::new(param_env); |
| let _ = ocx.resolve_regions_and_report_errors(impl_did, &outlives_env); |
| |
| Ok(CoerceUnsizedInfo { custom_kind: kind }) |
| } |
| |
| fn infringing_fields_error<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| infringing_tys: impl Iterator<Item = (Span, Ty<'tcx>, InfringingFieldsReason<'tcx>)>, |
| lang_item: LangItem, |
| impl_did: LocalDefId, |
| impl_span: Span, |
| ) -> ErrorGuaranteed { |
| let trait_did = tcx.require_lang_item(lang_item, Some(impl_span)); |
| |
| let trait_name = tcx.def_path_str(trait_did); |
| |
| // We'll try to suggest constraining type parameters to fulfill the requirements of |
| // their `Copy` implementation. |
| let mut errors: BTreeMap<_, Vec<_>> = Default::default(); |
| let mut bounds = vec![]; |
| |
| let mut seen_tys = FxHashSet::default(); |
| |
| let mut label_spans = Vec::new(); |
| |
| for (span, ty, reason) in infringing_tys { |
| // Only report an error once per type. |
| if !seen_tys.insert(ty) { |
| continue; |
| } |
| |
| label_spans.push(span); |
| |
| match reason { |
| InfringingFieldsReason::Fulfill(fulfillment_errors) => { |
| for error in fulfillment_errors { |
| let error_predicate = error.obligation.predicate; |
| // Only note if it's not the root obligation, otherwise it's trivial and |
| // should be self-explanatory (i.e. a field literally doesn't implement Copy). |
| |
| // FIXME: This error could be more descriptive, especially if the error_predicate |
| // contains a foreign type or if it's a deeply nested type... |
| if error_predicate != error.root_obligation.predicate { |
| errors |
| .entry((ty.to_string(), error_predicate.to_string())) |
| .or_default() |
| .push(error.obligation.cause.span); |
| } |
| if let ty::PredicateKind::Clause(ty::ClauseKind::Trait(ty::TraitPredicate { |
| trait_ref, |
| polarity: ty::PredicatePolarity::Positive, |
| .. |
| })) = error_predicate.kind().skip_binder() |
| { |
| let ty = trait_ref.self_ty(); |
| if let ty::Param(_) = ty.kind() { |
| bounds.push(( |
| format!("{ty}"), |
| trait_ref.print_trait_sugared().to_string(), |
| Some(trait_ref.def_id), |
| )); |
| } |
| } |
| } |
| } |
| InfringingFieldsReason::Regions(region_errors) => { |
| for error in region_errors { |
| let ty = ty.to_string(); |
| match error { |
| RegionResolutionError::ConcreteFailure(origin, a, b) => { |
| let predicate = format!("{b}: {a}"); |
| errors |
| .entry((ty.clone(), predicate.clone())) |
| .or_default() |
| .push(origin.span()); |
| if let ty::RegionKind::ReEarlyParam(ebr) = *b |
| && ebr.has_name() |
| { |
| bounds.push((b.to_string(), a.to_string(), None)); |
| } |
| } |
| RegionResolutionError::GenericBoundFailure(origin, a, b) => { |
| let predicate = format!("{a}: {b}"); |
| errors |
| .entry((ty.clone(), predicate.clone())) |
| .or_default() |
| .push(origin.span()); |
| if let infer::region_constraints::GenericKind::Param(_) = a { |
| bounds.push((a.to_string(), b.to_string(), None)); |
| } |
| } |
| _ => continue, |
| } |
| } |
| } |
| } |
| } |
| let mut notes = Vec::new(); |
| for ((ty, error_predicate), spans) in errors { |
| let span: MultiSpan = spans.into(); |
| notes.push(errors::ImplForTyRequires { |
| span, |
| error_predicate, |
| trait_name: trait_name.clone(), |
| ty, |
| }); |
| } |
| |
| let mut err = tcx.dcx().create_err(errors::TraitCannotImplForTy { |
| span: impl_span, |
| trait_name, |
| label_spans, |
| notes, |
| }); |
| |
| suggest_constraining_type_params( |
| tcx, |
| tcx.hir().get_generics(impl_did).expect("impls always have generics"), |
| &mut err, |
| bounds |
| .iter() |
| .map(|(param, constraint, def_id)| (param.as_str(), constraint.as_str(), *def_id)), |
| None, |
| ); |
| |
| err.emit() |
| } |
