diff options
Diffstat (limited to 'compiler/rustc_hir_analysis/src/delegation.rs')
| -rw-r--r-- | compiler/rustc_hir_analysis/src/delegation.rs | 445 |
1 files changed, 345 insertions, 100 deletions
diff --git a/compiler/rustc_hir_analysis/src/delegation.rs b/compiler/rustc_hir_analysis/src/delegation.rs index 20aaa43219f..2c9f20b7840 100644 --- a/compiler/rustc_hir_analysis/src/delegation.rs +++ b/compiler/rustc_hir_analysis/src/delegation.rs @@ -1,3 +1,7 @@ +//! Support inheriting generic parameters and predicates for function delegation. +//! +//! For more information about delegation design, see the tracking issue #118212. + use std::assert_matches::debug_assert_matches; use rustc_data_structures::fx::FxHashMap; @@ -5,7 +9,7 @@ use rustc_hir::def::DefKind; use rustc_hir::def_id::{DefId, LocalDefId}; use rustc_middle::ty::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable}; use rustc_middle::ty::{self, Ty, TyCtxt}; -use rustc_span::ErrorGuaranteed; +use rustc_span::{ErrorGuaranteed, Span}; use rustc_type_ir::visit::TypeVisitableExt; type RemapTable = FxHashMap<u32, u32>; @@ -76,127 +80,381 @@ fn fn_kind<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> FnKind { } } +/// Given the current context(caller and callee `FnKind`), it specifies +/// the policy of predicates and generic parameters inheritance. +#[derive(Clone, Copy, Debug, PartialEq)] +enum InheritanceKind { + /// Copying all predicates and parameters, including those of the parent + /// container. + /// + /// Boolean value defines whether the `Self` parameter or `Self: Trait` + /// predicate are copied. It's always equal to `false` except when + /// delegating from a free function to a trait method. + /// + /// FIXME(fn_delegation): This often leads to type inference + /// errors. Support providing generic arguments or restrict use sites. + WithParent(bool), + /// The trait implementation should be compatible with the original trait. + /// Therefore, for trait implementations only the method's own parameters + /// and predicates are copied. + Own, +} + +struct GenericsBuilder<'tcx> { + tcx: TyCtxt<'tcx>, + sig_id: DefId, + parent: Option<DefId>, + inh_kind: InheritanceKind, +} + +impl<'tcx> GenericsBuilder<'tcx> { + fn new(tcx: TyCtxt<'tcx>, sig_id: DefId) -> GenericsBuilder<'tcx> { + GenericsBuilder { tcx, sig_id, parent: None, inh_kind: InheritanceKind::WithParent(false) } + } + + fn with_parent(mut self, parent: DefId) -> Self { + self.parent = Some(parent); + self + } + + fn with_inheritance_kind(mut self, inh_kind: InheritanceKind) -> Self { + self.inh_kind = inh_kind; + self + } + + fn build(self) -> ty::Generics { + let mut own_params = vec![]; + + let sig_generics = self.tcx.generics_of(self.sig_id); + if let InheritanceKind::WithParent(has_self) = self.inh_kind + && let Some(parent_def_id) = sig_generics.parent + { + let sig_parent_generics = self.tcx.generics_of(parent_def_id); + own_params.append(&mut sig_parent_generics.own_params.clone()); + if !has_self { + own_params.remove(0); + } + } + own_params.append(&mut sig_generics.own_params.clone()); + + // Lifetime parameters must be declared before type and const parameters. + // Therefore, When delegating from a free function to a associated function, + // generic parameters need to be reordered: + // + // trait Trait<'a, A> { + // fn foo<'b, B>(...) {...} + // } + // + // reuse Trait::foo; + // desugaring: + // fn foo<'a, 'b, This: Trait<'a, A>, A, B>(...) { + // Trait::foo(...) + // } + own_params.sort_by_key(|key| key.kind.is_ty_or_const()); + + let param_def_id_to_index = + own_params.iter().map(|param| (param.def_id, param.index)).collect(); + + let (parent_count, has_self) = if let Some(def_id) = self.parent { + let parent_generics = self.tcx.generics_of(def_id); + let parent_kind = self.tcx.def_kind(def_id); + (parent_generics.count(), parent_kind == DefKind::Trait) + } else { + (0, false) + }; + + for (idx, param) in own_params.iter_mut().enumerate() { + param.index = (idx + parent_count) as u32; + // FIXME(fn_delegation): Default parameters are not inherited, because they are + // not permitted in functions. Therefore, there are 2 options here: + // + // - We can create non-default generic parameters. + // - We can substitute default parameters into the signature. + // + // At the moment, first option has been selected as the most general. + if let ty::GenericParamDefKind::Type { has_default, .. } + | ty::GenericParamDefKind::Const { has_default, .. } = &mut param.kind + { + *has_default = false; + } + } + + ty::Generics { + parent: self.parent, + parent_count, + own_params, + param_def_id_to_index, + has_self, + has_late_bound_regions: sig_generics.has_late_bound_regions, + host_effect_index: sig_generics.host_effect_index, + } + } +} + +struct PredicatesBuilder<'tcx> { + tcx: TyCtxt<'tcx>, + sig_id: DefId, + parent: Option<DefId>, + inh_kind: InheritanceKind, + args: ty::GenericArgsRef<'tcx>, +} + +impl<'tcx> PredicatesBuilder<'tcx> { + fn new( + tcx: TyCtxt<'tcx>, + args: ty::GenericArgsRef<'tcx>, + sig_id: DefId, + ) -> PredicatesBuilder<'tcx> { + PredicatesBuilder { + tcx, + sig_id, + parent: None, + inh_kind: InheritanceKind::WithParent(false), + args, + } + } + + fn with_parent(mut self, parent: DefId) -> Self { + self.parent = Some(parent); + self + } + + fn with_inheritance_kind(mut self, inh_kind: InheritanceKind) -> Self { + self.inh_kind = inh_kind; + self + } + + fn build(self) -> ty::GenericPredicates<'tcx> { + struct PredicatesCollector<'tcx> { + tcx: TyCtxt<'tcx>, + preds: Vec<(ty::Clause<'tcx>, Span)>, + args: ty::GenericArgsRef<'tcx>, + } + + impl<'tcx> PredicatesCollector<'tcx> { + fn new(tcx: TyCtxt<'tcx>, args: ty::GenericArgsRef<'tcx>) -> PredicatesCollector<'tcx> { + PredicatesCollector { tcx, preds: vec![], args } + } + + fn with_own_preds( + mut self, + f: impl Fn(DefId) -> ty::GenericPredicates<'tcx>, + def_id: DefId, + ) -> Self { + let preds = f(def_id).instantiate_own(self.tcx, self.args); + self.preds.extend(preds); + self + } + + fn with_preds( + mut self, + f: impl Fn(DefId) -> ty::GenericPredicates<'tcx> + Copy, + def_id: DefId, + ) -> Self { + let preds = f(def_id); + if let Some(parent_def_id) = preds.parent { + self = self.with_own_preds(f, parent_def_id); + } + self.with_own_preds(f, def_id) + } + } + let collector = PredicatesCollector::new(self.tcx, self.args); + + // `explicit_predicates_of` is used here to avoid copying `Self: Trait` predicate. + // Note: `predicates_of` query can also add inferred outlives predicates, but that + // is not the case here as `sig_id` is either a trait or a function. + let preds = match self.inh_kind { + InheritanceKind::WithParent(false) => { + collector.with_preds(|def_id| self.tcx.explicit_predicates_of(def_id), self.sig_id) + } + InheritanceKind::WithParent(true) => { + collector.with_preds(|def_id| self.tcx.predicates_of(def_id), self.sig_id) + } + InheritanceKind::Own => { + collector.with_own_preds(|def_id| self.tcx.predicates_of(def_id), self.sig_id) + } + } + .preds; + + ty::GenericPredicates { + parent: self.parent, + predicates: self.tcx.arena.alloc_from_iter(preds), + // FIXME(fn_delegation): Support effects. + effects_min_tys: ty::List::empty(), + } + } +} + +struct GenericArgsBuilder<'tcx> { + tcx: TyCtxt<'tcx>, + remap_table: RemapTable, + sig_id: DefId, + def_id: LocalDefId, +} + +impl<'tcx> GenericArgsBuilder<'tcx> { + fn new(tcx: TyCtxt<'tcx>, sig_id: DefId, def_id: LocalDefId) -> GenericArgsBuilder<'tcx> { + GenericArgsBuilder { tcx, remap_table: FxHashMap::default(), sig_id, def_id } + } + + fn build_from_args(mut self, args: ty::GenericArgsRef<'tcx>) -> ty::GenericArgsRef<'tcx> { + let caller_generics = self.tcx.generics_of(self.def_id); + let callee_generics = self.tcx.generics_of(self.sig_id); + + for caller_param in &caller_generics.own_params { + let callee_index = + callee_generics.param_def_id_to_index(self.tcx, caller_param.def_id).unwrap(); + self.remap_table.insert(callee_index, caller_param.index); + } + + let mut folder = ParamIndexRemapper { tcx: self.tcx, remap_table: self.remap_table }; + args.fold_with(&mut folder) + } +} + fn create_generic_args<'tcx>( tcx: TyCtxt<'tcx>, def_id: LocalDefId, sig_id: DefId, ) -> ty::GenericArgsRef<'tcx> { - let caller_generics = tcx.generics_of(def_id); - let callee_generics = tcx.generics_of(sig_id); + let builder = GenericArgsBuilder::new(tcx, sig_id, def_id); let caller_kind = fn_kind(tcx, def_id.into()); let callee_kind = fn_kind(tcx, sig_id); - // FIXME(fn_delegation): Support generics on associated delegation items. - // Error will be reported in `check_constraints`. match (caller_kind, callee_kind) { - (FnKind::Free, _) => { - // Lifetime parameters must be declared before type and const parameters. - // Therefore, When delegating from a free function to a associated function, - // generic parameters need to be reordered: - // - // trait Trait<'a, A> { - // fn foo<'b, B>(...) {...} - // } - // - // reuse Trait::foo; - // desugaring: - // fn foo<'a, 'b, This: Trait<'a, A>, A, B>(...) { - // Trait::foo(...) - // } - let mut remap_table = RemapTable::default(); - for caller_param in &caller_generics.own_params { - let callee_index = - callee_generics.param_def_id_to_index(tcx, caller_param.def_id).unwrap(); - remap_table.insert(callee_index, caller_param.index); - } - let mut folder = ParamIndexRemapper { tcx, remap_table }; - ty::GenericArgs::identity_for_item(tcx, sig_id).fold_with(&mut folder) + (FnKind::Free, FnKind::Free) + | (FnKind::Free, FnKind::AssocTrait) + | (FnKind::AssocInherentImpl, FnKind::Free) + | (FnKind::AssocTrait, FnKind::Free) + | (FnKind::AssocTrait, FnKind::AssocTrait) => { + let args = ty::GenericArgs::identity_for_item(tcx, sig_id); + builder.build_from_args(args) } - // FIXME(fn_delegation): Only `Self` param supported here. - (FnKind::AssocTraitImpl, FnKind::AssocTrait) - | (FnKind::AssocInherentImpl, FnKind::AssocTrait) => { + + (FnKind::AssocTraitImpl, FnKind::AssocTrait) => { + let callee_generics = tcx.generics_of(sig_id); + let parent = tcx.parent(def_id.into()); + let parent_args = + tcx.impl_trait_header(parent).unwrap().trait_ref.instantiate_identity().args; + + let trait_args = ty::GenericArgs::identity_for_item(tcx, sig_id); + let method_args = tcx.mk_args_from_iter(trait_args.iter().skip(callee_generics.parent_count)); + let method_args = builder.build_from_args(method_args); + + tcx.mk_args_from_iter(parent_args.iter().chain(method_args)) + } + + (FnKind::AssocInherentImpl, FnKind::AssocTrait) => { let parent = tcx.parent(def_id.into()); let self_ty = tcx.type_of(parent).instantiate_identity(); let generic_self_ty = ty::GenericArg::from(self_ty); - tcx.mk_args_from_iter(std::iter::once(generic_self_ty)) + + let trait_args = ty::GenericArgs::identity_for_item(tcx, sig_id); + let trait_args = builder.build_from_args(trait_args); + + let args = std::iter::once(generic_self_ty).chain(trait_args.iter().skip(1)); + tcx.mk_args_from_iter(args) } - _ => ty::GenericArgs::identity_for_item(tcx, sig_id), + + // For trait impl's `sig_id` is always equal to the corresponding trait method. + (FnKind::AssocTraitImpl, _) + | (_, FnKind::AssocTraitImpl) + // Delegation to inherent methods is not yet supported. + | (_, FnKind::AssocInherentImpl) => unreachable!(), } } +// FIXME(fn_delegation): Move generics inheritance to the AST->HIR lowering. +// For now, generic parameters are not propagated to the generated call, +// which leads to inference errors: +// +// fn foo<T>(x: i32) {} +// +// reuse foo as bar; +// desugaring: +// fn bar<T>() { +// foo::<_>() // ERROR: type annotations needed +// } pub(crate) fn inherit_generics_for_delegation_item<'tcx>( tcx: TyCtxt<'tcx>, def_id: LocalDefId, sig_id: DefId, -) -> Option<ty::Generics> { - // FIXME(fn_delegation): Support generics on associated delegation items. - // Error will be reported in `check_constraints`. - if fn_kind(tcx, def_id.into()) != FnKind::Free { - return None; - } +) -> ty::Generics { + let builder = GenericsBuilder::new(tcx, sig_id); - let mut own_params = vec![]; - - let callee_generics = tcx.generics_of(sig_id); - if let Some(parent_sig_id) = callee_generics.parent { - let parent_sig_generics = tcx.generics_of(parent_sig_id); - own_params.append(&mut parent_sig_generics.own_params.clone()); - } - own_params.append(&mut callee_generics.own_params.clone()); + let caller_kind = fn_kind(tcx, def_id.into()); + let callee_kind = fn_kind(tcx, sig_id); + match (caller_kind, callee_kind) { + (FnKind::Free, FnKind::Free) + | (FnKind::Free, FnKind::AssocTrait) => builder.with_inheritance_kind(InheritanceKind::WithParent(true)).build(), + + (FnKind::AssocTraitImpl, FnKind::AssocTrait) => { + builder + .with_parent(tcx.parent(def_id.into())) + .with_inheritance_kind(InheritanceKind::Own) + .build() + } - // Lifetimes go first. - own_params.sort_by_key(|key| key.kind.is_ty_or_const()); + (FnKind::AssocInherentImpl, FnKind::AssocTrait) + | (FnKind::AssocTrait, FnKind::AssocTrait) => { + builder + .with_parent(tcx.parent(def_id.into())) + .build() + } - for (idx, param) in own_params.iter_mut().enumerate() { - param.index = idx as u32; - // Default parameters are not inherited: they are not allowed - // in fn's. - if let ty::GenericParamDefKind::Type { has_default, .. } - | ty::GenericParamDefKind::Const { has_default, .. } = &mut param.kind - { - *has_default = false; + (FnKind::AssocInherentImpl, FnKind::Free) + | (FnKind::AssocTrait, FnKind::Free) => { + builder + .with_parent(tcx.parent(def_id.into())) + .build() } - } - let param_def_id_to_index = - own_params.iter().map(|param| (param.def_id, param.index)).collect(); - - Some(ty::Generics { - parent: None, - parent_count: 0, - own_params, - param_def_id_to_index, - has_self: false, - has_late_bound_regions: callee_generics.has_late_bound_regions, - host_effect_index: callee_generics.host_effect_index, - }) + // For trait impl's `sig_id` is always equal to the corresponding trait method. + (FnKind::AssocTraitImpl, _) + | (_, FnKind::AssocTraitImpl) + // Delegation to inherent methods is not yet supported. + | (_, FnKind::AssocInherentImpl) => unreachable!(), + } } pub(crate) fn inherit_predicates_for_delegation_item<'tcx>( tcx: TyCtxt<'tcx>, def_id: LocalDefId, sig_id: DefId, -) -> Option<ty::GenericPredicates<'tcx>> { - // FIXME(fn_delegation): Support generics on associated delegation items. - // Error will be reported in `check_constraints`. - if fn_kind(tcx, def_id.into()) != FnKind::Free { - return None; - } - - let callee_predicates = tcx.predicates_of(sig_id); +) -> ty::GenericPredicates<'tcx> { let args = create_generic_args(tcx, def_id, sig_id); + let builder = PredicatesBuilder::new(tcx, args, sig_id); - let mut preds = vec![]; - if let Some(parent_id) = callee_predicates.parent { - preds.extend(tcx.predicates_of(parent_id).instantiate_own(tcx, args)); - } - preds.extend(callee_predicates.instantiate_own(tcx, args)); + let caller_kind = fn_kind(tcx, def_id.into()); + let callee_kind = fn_kind(tcx, sig_id); + match (caller_kind, callee_kind) { + (FnKind::Free, FnKind::Free) + | (FnKind::Free, FnKind::AssocTrait) => { + builder.with_inheritance_kind(InheritanceKind::WithParent(true)).build() + } + + (FnKind::AssocTraitImpl, FnKind::AssocTrait) => { + builder + .with_parent(tcx.parent(def_id.into())) + .with_inheritance_kind(InheritanceKind::Own) + .build() + } + + (FnKind::AssocInherentImpl, FnKind::AssocTrait) + | (FnKind::AssocTrait, FnKind::AssocTrait) + | (FnKind::AssocInherentImpl, FnKind::Free) + | (FnKind::AssocTrait, FnKind::Free) => { + builder + .with_parent(tcx.parent(def_id.into())) + .build() + } - Some(ty::GenericPredicates { - parent: None, - predicates: tcx.arena.alloc_from_iter(preds), - effects_min_tys: ty::List::empty(), - }) + // For trait impl's `sig_id` is always equal to the corresponding trait method. + (FnKind::AssocTraitImpl, _) + | (_, FnKind::AssocTraitImpl) + // Delegation to inherent methods is not yet supported. + | (_, FnKind::AssocInherentImpl) => unreachable!(), + } } fn check_constraints<'tcx>( @@ -224,19 +482,6 @@ fn check_constraints<'tcx>( emit("recursive delegation is not supported yet"); } - if fn_kind(tcx, def_id.into()) != FnKind::Free { - let sig_generics = tcx.generics_of(sig_id); - let parent = tcx.parent(def_id.into()); - let parent_generics = tcx.generics_of(parent); - - let parent_has_self = parent_generics.has_self as usize; - let sig_has_self = sig_generics.has_self as usize; - - if sig_generics.count() > sig_has_self || parent_generics.count() > parent_has_self { - emit("early bound generics are not supported for associated delegation items"); - } - } - ret } |