diff --git a/compiler/rustc_hir_analysis/src/astconv/mod.rs b/compiler/rustc_hir_analysis/src/astconv/mod.rs index c7d4d8e3517c9..455eb6f039e72 100644 --- a/compiler/rustc_hir_analysis/src/astconv/mod.rs +++ b/compiler/rustc_hir_analysis/src/astconv/mod.rs @@ -27,11 +27,12 @@ use rustc_hir::def_id::{DefId, LocalDefId}; use rustc_hir::intravisit::{walk_generics, Visitor as _}; use rustc_hir::{GenericArg, GenericArgs, OpaqueTyOrigin}; use rustc_infer::infer::{InferCtxt, InferOk, TyCtxtInferExt}; -use rustc_infer::traits::ObligationCause; +use rustc_infer::traits::{Obligation, ObligationCause}; use rustc_middle::middle::stability::AllowUnstable; use rustc_middle::ty::GenericParamDefKind; use rustc_middle::ty::{ - self, Const, GenericArgKind, GenericArgsRef, IsSuggestable, Ty, TyCtxt, TypeVisitableExt, + self, Const, GenericArgKind, GenericArgsRef, IsSuggestable, ParamEnv, Predicate, Ty, TyCtxt, + TypeVisitableExt, }; use rustc_session::lint::builtin::AMBIGUOUS_ASSOCIATED_ITEMS; use rustc_span::edit_distance::find_best_match_for_name; @@ -1607,7 +1608,6 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o { let param_env = tcx.param_env(block.owner); let cause = ObligationCause::misc(span, block.owner.def_id); - let mut fulfillment_errors = Vec::new(); let mut universes = if self_ty.has_escaping_bound_vars() { vec![None; self_ty.outer_exclusive_binder().as_usize()] } else { @@ -1619,94 +1619,110 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o { &mut universes, self_ty, |self_ty| { + let tcx = self.tcx(); let InferOk { value: self_ty, obligations } = infcx.at(&cause, param_env).normalize(self_ty); - let mut applicable_candidates: Vec<_> = candidates - .iter() - .copied() - .filter(|&(impl_, _)| { - infcx.probe(|_| { - let ocx = ObligationCtxt::new(infcx); - ocx.register_obligations(obligations.clone()); - - let impl_args = infcx.fresh_args_for_item(span, impl_); - let impl_ty = tcx.type_of(impl_).instantiate(tcx, impl_args); - let impl_ty = ocx.normalize(&cause, param_env, impl_ty); - - // Check that the self types can be related. - if ocx - .eq(&ObligationCause::dummy(), param_env, impl_ty, self_ty) - .is_err() - { - return false; - } - - // Check whether the impl imposes obligations we have to worry about. - let impl_bounds = tcx.predicates_of(impl_).instantiate(tcx, impl_args); - let impl_bounds = ocx.normalize(&cause, param_env, impl_bounds); - let impl_obligations = traits::predicates_for_generics( - |_, _| cause.clone(), - param_env, - impl_bounds, - ); - ocx.register_obligations(impl_obligations); + let (impl_, (assoc_item, def_scope)) = self.select_inherent_assoc_type_candidates( + infcx, + name, + span, + self_ty, + cause, + param_env, + obligations, + candidates, + )?; + + self.check_assoc_ty(assoc_item, name, def_scope, block, span); + + // FIXME(fmease): Currently creating throwaway `parent_args` to please + // `create_args_for_associated_item`. Modify the latter instead (or sth. similar) to + // not require the parent args logic. + let parent_args = ty::GenericArgs::identity_for_item(tcx, impl_); + let args = + self.create_args_for_associated_item(span, assoc_item, segment, parent_args); + let args = tcx.mk_args_from_iter( + std::iter::once(ty::GenericArg::from(self_ty)) + .chain(args.into_iter().skip(parent_args.len())), + ); - let mut errors = ocx.select_where_possible(); - if !errors.is_empty() { - fulfillment_errors.append(&mut errors); - return false; - } + let ty = Ty::new_alias(tcx, ty::Inherent, ty::AliasTy::new(tcx, assoc_item, args)); - true - }) - }) - .collect(); + Ok(Some((ty, assoc_item))) + }, + ) + } - if applicable_candidates.len() > 1 { - return Err(self.complain_about_ambiguous_inherent_assoc_type( - name, - applicable_candidates - .into_iter() - .map(|(_, (candidate, _))| candidate) - .collect(), - span, - )); - } + fn select_inherent_assoc_type_candidates( + &self, + infcx: &InferCtxt<'tcx>, + name: Ident, + span: Span, + self_ty: Ty<'tcx>, + cause: ObligationCause<'tcx>, + param_env: ParamEnv<'tcx>, + obligations: Vec>>, + candidates: Vec<(DefId, (DefId, DefId))>, + ) -> Result<(DefId, (DefId, DefId)), ErrorGuaranteed> { + let tcx = self.tcx(); + let mut fulfillment_errors = Vec::new(); - if let Some((impl_, (assoc_item, def_scope))) = applicable_candidates.pop() { - self.check_assoc_ty(assoc_item, name, def_scope, block, span); + let applicable_candidates: Vec<_> = candidates + .iter() + .copied() + .filter(|&(impl_, _)| { + infcx.probe(|_| { + let ocx = ObligationCtxt::new(infcx); + ocx.register_obligations(obligations.clone()); + + let impl_args = infcx.fresh_args_for_item(span, impl_); + let impl_ty = tcx.type_of(impl_).instantiate(tcx, impl_args); + let impl_ty = ocx.normalize(&cause, param_env, impl_ty); + + // Check that the self types can be related. + if ocx.eq(&ObligationCause::dummy(), param_env, impl_ty, self_ty).is_err() { + return false; + } - // FIXME(fmease): Currently creating throwaway `parent_args` to please - // `create_args_for_associated_item`. Modify the latter instead (or sth. similar) to - // not require the parent args logic. - let parent_args = ty::GenericArgs::identity_for_item(tcx, impl_); - let args = self.create_args_for_associated_item( - span, - assoc_item, - segment, - parent_args, - ); - let args = tcx.mk_args_from_iter( - std::iter::once(ty::GenericArg::from(self_ty)) - .chain(args.into_iter().skip(parent_args.len())), + // Check whether the impl imposes obligations we have to worry about. + let impl_bounds = tcx.predicates_of(impl_).instantiate(tcx, impl_args); + let impl_bounds = ocx.normalize(&cause, param_env, impl_bounds); + let impl_obligations = traits::predicates_for_generics( + |_, _| cause.clone(), + param_env, + impl_bounds, ); + ocx.register_obligations(impl_obligations); - let ty = - Ty::new_alias(tcx, ty::Inherent, ty::AliasTy::new(tcx, assoc_item, args)); + let mut errors = ocx.select_where_possible(); + if !errors.is_empty() { + fulfillment_errors.append(&mut errors); + return false; + } - return Ok(Some((ty, assoc_item))); - } + true + }) + }) + .collect(); - Err(self.complain_about_inherent_assoc_type_not_found( - name, - self_ty, - candidates, - fulfillment_errors, - span, - )) - }, - ) + match &applicable_candidates[..] { + &[] => Err(self.complain_about_inherent_assoc_type_not_found( + name, + self_ty, + candidates, + fulfillment_errors, + span, + )), + + &[applicable_candidate] => Ok(applicable_candidate), + + &[_, ..] => Err(self.complain_about_ambiguous_inherent_assoc_type( + name, + applicable_candidates.into_iter().map(|(_, (candidate, _))| candidate).collect(), + span, + )), + } } fn lookup_assoc_ty(