From 4343d360793e428460f69d6df81acf6944d48fe8 Mon Sep 17 00:00:00 2001 From: Michael Goulet Date: Fri, 16 Jun 2023 18:24:43 +0000 Subject: [PATCH] Move some bounds computation out of astconv into its own file --- .../rustc_hir_analysis/src/astconv/bounds.rs | 583 ++++++++++++++++++ .../rustc_hir_analysis/src/astconv/mod.rs | 569 +---------------- 2 files changed, 585 insertions(+), 567 deletions(-) create mode 100644 compiler/rustc_hir_analysis/src/astconv/bounds.rs diff --git a/compiler/rustc_hir_analysis/src/astconv/bounds.rs b/compiler/rustc_hir_analysis/src/astconv/bounds.rs new file mode 100644 index 0000000000000..e4eb0e6abd435 --- /dev/null +++ b/compiler/rustc_hir_analysis/src/astconv/bounds.rs @@ -0,0 +1,583 @@ +use rustc_data_structures::fx::FxHashMap; +use rustc_errors::struct_span_err; +use rustc_hir as hir; +use rustc_hir::def::{DefKind, Res}; +use rustc_hir::def_id::{DefId, LocalDefId}; +use rustc_lint_defs::Applicability; +use rustc_middle::ty::{self as ty, Ty, TypeVisitableExt}; +use rustc_span::symbol::Ident; +use rustc_span::{ErrorGuaranteed, Span}; +use rustc_trait_selection::traits; + +use crate::astconv::{AstConv, ConvertedBinding, ConvertedBindingKind}; +use crate::bounds::Bounds; +use crate::errors::{MultipleRelaxedDefaultBounds, ValueOfAssociatedStructAlreadySpecified}; + +use super::OnlySelfBounds; + +impl<'tcx> dyn AstConv<'tcx> + '_ { + /// Sets `implicitly_sized` to true on `Bounds` if necessary + pub(crate) fn add_implicitly_sized( + &self, + bounds: &mut Bounds<'tcx>, + self_ty: Ty<'tcx>, + ast_bounds: &'tcx [hir::GenericBound<'tcx>], + self_ty_where_predicates: Option<(LocalDefId, &'tcx [hir::WherePredicate<'tcx>])>, + span: Span, + ) { + let tcx = self.tcx(); + + // Try to find an unbound in bounds. + let mut unbound = None; + let mut search_bounds = |ast_bounds: &'tcx [hir::GenericBound<'tcx>]| { + for ab in ast_bounds { + if let hir::GenericBound::Trait(ptr, hir::TraitBoundModifier::Maybe) = ab { + if unbound.is_none() { + unbound = Some(&ptr.trait_ref); + } else { + tcx.sess.emit_err(MultipleRelaxedDefaultBounds { span }); + } + } + } + }; + search_bounds(ast_bounds); + if let Some((self_ty, where_clause)) = self_ty_where_predicates { + for clause in where_clause { + if let hir::WherePredicate::BoundPredicate(pred) = clause { + if pred.is_param_bound(self_ty.to_def_id()) { + search_bounds(pred.bounds); + } + } + } + } + + let sized_def_id = tcx.lang_items().sized_trait(); + match (&sized_def_id, unbound) { + (Some(sized_def_id), Some(tpb)) + if tpb.path.res == Res::Def(DefKind::Trait, *sized_def_id) => + { + // There was in fact a `?Sized` bound, return without doing anything + return; + } + (_, Some(_)) => { + // There was a `?Trait` bound, but it was not `?Sized`; warn. + tcx.sess.span_warn( + span, + "default bound relaxed for a type parameter, but \ + this does nothing because the given bound is not \ + a default; only `?Sized` is supported", + ); + // Otherwise, add implicitly sized if `Sized` is available. + } + _ => { + // There was no `?Sized` bound; add implicitly sized if `Sized` is available. + } + } + if sized_def_id.is_none() { + // No lang item for `Sized`, so we can't add it as a bound. + return; + } + bounds.push_sized(tcx, self_ty, span); + } + + /// This helper takes a *converted* parameter type (`param_ty`) + /// and an *unconverted* list of bounds: + /// + /// ```text + /// fn foo + /// ^ ^^^^^ `ast_bounds` parameter, in HIR form + /// | + /// `param_ty`, in ty form + /// ``` + /// + /// It adds these `ast_bounds` into the `bounds` structure. + /// + /// **A note on binders:** there is an implied binder around + /// `param_ty` and `ast_bounds`. See `instantiate_poly_trait_ref` + /// for more details. + #[instrument(level = "debug", skip(self, ast_bounds, bounds))] + pub(crate) fn add_bounds<'hir, I: Iterator>>( + &self, + param_ty: Ty<'tcx>, + ast_bounds: I, + bounds: &mut Bounds<'tcx>, + bound_vars: &'tcx ty::List, + only_self_bounds: OnlySelfBounds, + ) { + for ast_bound in ast_bounds { + match ast_bound { + hir::GenericBound::Trait(poly_trait_ref, modifier) => { + let (constness, polarity) = match modifier { + hir::TraitBoundModifier::MaybeConst => { + (ty::BoundConstness::ConstIfConst, ty::ImplPolarity::Positive) + } + hir::TraitBoundModifier::None => { + (ty::BoundConstness::NotConst, ty::ImplPolarity::Positive) + } + hir::TraitBoundModifier::Negative => { + (ty::BoundConstness::NotConst, ty::ImplPolarity::Negative) + } + hir::TraitBoundModifier::Maybe => continue, + }; + let _ = self.instantiate_poly_trait_ref( + &poly_trait_ref.trait_ref, + poly_trait_ref.span, + constness, + polarity, + param_ty, + bounds, + false, + only_self_bounds, + ); + } + &hir::GenericBound::LangItemTrait(lang_item, span, hir_id, args) => { + self.instantiate_lang_item_trait_ref( + lang_item, + span, + hir_id, + args, + param_ty, + bounds, + only_self_bounds, + ); + } + hir::GenericBound::Outlives(lifetime) => { + let region = self.ast_region_to_region(lifetime, None); + bounds.push_region_bound( + self.tcx(), + ty::Binder::bind_with_vars( + ty::OutlivesPredicate(param_ty, region), + bound_vars, + ), + lifetime.ident.span, + ); + } + } + } + } + + /// Translates a list of bounds from the HIR into the `Bounds` data structure. + /// The self-type for the bounds is given by `param_ty`. + /// + /// Example: + /// + /// ```ignore (illustrative) + /// fn foo() { } + /// // ^ ^^^^^^^^^ ast_bounds + /// // param_ty + /// ``` + /// + /// The `sized_by_default` parameter indicates if, in this context, the `param_ty` should be + /// considered `Sized` unless there is an explicit `?Sized` bound. This would be true in the + /// example above, but is not true in supertrait listings like `trait Foo: Bar + Baz`. + /// + /// `span` should be the declaration size of the parameter. + pub(crate) fn compute_bounds( + &self, + param_ty: Ty<'tcx>, + ast_bounds: &[hir::GenericBound<'_>], + only_self_bounds: OnlySelfBounds, + ) -> Bounds<'tcx> { + let mut bounds = Bounds::default(); + self.add_bounds( + param_ty, + ast_bounds.iter(), + &mut bounds, + ty::List::empty(), + only_self_bounds, + ); + debug!(?bounds); + + bounds + } + + /// Convert the bounds in `ast_bounds` that refer to traits which define an associated type + /// named `assoc_name` into ty::Bounds. Ignore the rest. + pub(crate) fn compute_bounds_that_match_assoc_item( + &self, + param_ty: Ty<'tcx>, + ast_bounds: &[hir::GenericBound<'_>], + assoc_name: Ident, + ) -> Bounds<'tcx> { + let mut result = Vec::new(); + + for ast_bound in ast_bounds { + if let Some(trait_ref) = ast_bound.trait_ref() + && let Some(trait_did) = trait_ref.trait_def_id() + && self.tcx().trait_may_define_assoc_item(trait_did, assoc_name) + { + result.push(ast_bound.clone()); + } + } + + let mut bounds = Bounds::default(); + self.add_bounds( + param_ty, + result.iter(), + &mut bounds, + ty::List::empty(), + OnlySelfBounds(true), + ); + debug!(?bounds); + + bounds + } + + /// Given an HIR binding like `Item = Foo` or `Item: Foo`, pushes the corresponding predicates + /// onto `bounds`. + /// + /// **A note on binders:** given something like `T: for<'a> Iterator`, the + /// `trait_ref` here will be `for<'a> T: Iterator`. The `binding` data however is from *inside* + /// the binder (e.g., `&'a u32`) and hence may reference bound regions. + #[instrument(level = "debug", skip(self, bounds, speculative, dup_bindings, path_span))] + pub(super) fn add_predicates_for_ast_type_binding( + &self, + hir_ref_id: hir::HirId, + trait_ref: ty::PolyTraitRef<'tcx>, + binding: &ConvertedBinding<'_, 'tcx>, + bounds: &mut Bounds<'tcx>, + speculative: bool, + dup_bindings: &mut FxHashMap, + path_span: Span, + constness: ty::BoundConstness, + only_self_bounds: OnlySelfBounds, + polarity: ty::ImplPolarity, + ) -> Result<(), ErrorGuaranteed> { + // Given something like `U: SomeTrait`, we want to produce a + // predicate like `::T = X`. This is somewhat + // subtle in the event that `T` is defined in a supertrait of + // `SomeTrait`, because in that case we need to upcast. + // + // That is, consider this case: + // + // ``` + // trait SubTrait: SuperTrait { } + // trait SuperTrait { type T; } + // + // ... B: SubTrait ... + // ``` + // + // We want to produce `>::T == foo`. + + let tcx = self.tcx(); + + let return_type_notation = + binding.gen_args.parenthesized == hir::GenericArgsParentheses::ReturnTypeNotation; + + let candidate = if return_type_notation { + if self.trait_defines_associated_item_named( + trait_ref.def_id(), + ty::AssocKind::Fn, + binding.item_name, + ) { + trait_ref + } else { + self.one_bound_for_assoc_method( + traits::supertraits(tcx, trait_ref), + trait_ref.print_only_trait_path(), + binding.item_name, + path_span, + )? + } + } else if self.trait_defines_associated_item_named( + trait_ref.def_id(), + ty::AssocKind::Type, + binding.item_name, + ) { + // Simple case: X is defined in the current trait. + trait_ref + } else { + // Otherwise, we have to walk through the supertraits to find + // those that do. + self.one_bound_for_assoc_type( + || traits::supertraits(tcx, trait_ref), + trait_ref.skip_binder().print_only_trait_name(), + binding.item_name, + path_span, + match binding.kind { + ConvertedBindingKind::Equality(term) => Some(term), + _ => None, + }, + )? + }; + + let (assoc_ident, def_scope) = + tcx.adjust_ident_and_get_scope(binding.item_name, candidate.def_id(), hir_ref_id); + + // We have already adjusted the item name above, so compare with `ident.normalize_to_macros_2_0()` instead + // of calling `filter_by_name_and_kind`. + let find_item_of_kind = |kind| { + tcx.associated_items(candidate.def_id()) + .filter_by_name_unhygienic(assoc_ident.name) + .find(|i| i.kind == kind && i.ident(tcx).normalize_to_macros_2_0() == assoc_ident) + }; + let assoc_item = if return_type_notation { + find_item_of_kind(ty::AssocKind::Fn) + } else { + find_item_of_kind(ty::AssocKind::Type) + .or_else(|| find_item_of_kind(ty::AssocKind::Const)) + } + .expect("missing associated type"); + + if !assoc_item.visibility(tcx).is_accessible_from(def_scope, tcx) { + tcx.sess + .struct_span_err( + binding.span, + format!("{} `{}` is private", assoc_item.kind, binding.item_name), + ) + .span_label(binding.span, format!("private {}", assoc_item.kind)) + .emit(); + } + tcx.check_stability(assoc_item.def_id, Some(hir_ref_id), binding.span, None); + + if !speculative { + dup_bindings + .entry(assoc_item.def_id) + .and_modify(|prev_span| { + tcx.sess.emit_err(ValueOfAssociatedStructAlreadySpecified { + span: binding.span, + prev_span: *prev_span, + item_name: binding.item_name, + def_path: tcx.def_path_str(assoc_item.container_id(tcx)), + }); + }) + .or_insert(binding.span); + } + + let projection_ty = if return_type_notation { + let mut emitted_bad_param_err = false; + // If we have an method return type bound, then we need to substitute + // the method's early bound params with suitable late-bound params. + let mut num_bound_vars = candidate.bound_vars().len(); + let substs = + candidate.skip_binder().substs.extend_to(tcx, assoc_item.def_id, |param, _| { + let subst = match param.kind { + ty::GenericParamDefKind::Lifetime => ty::Region::new_late_bound( + tcx, + ty::INNERMOST, + ty::BoundRegion { + var: ty::BoundVar::from_usize(num_bound_vars), + kind: ty::BoundRegionKind::BrNamed(param.def_id, param.name), + }, + ) + .into(), + ty::GenericParamDefKind::Type { .. } => { + if !emitted_bad_param_err { + tcx.sess.emit_err( + crate::errors::ReturnTypeNotationIllegalParam::Type { + span: path_span, + param_span: tcx.def_span(param.def_id), + }, + ); + emitted_bad_param_err = true; + } + tcx.mk_bound( + ty::INNERMOST, + ty::BoundTy { + var: ty::BoundVar::from_usize(num_bound_vars), + kind: ty::BoundTyKind::Param(param.def_id, param.name), + }, + ) + .into() + } + ty::GenericParamDefKind::Const { .. } => { + if !emitted_bad_param_err { + tcx.sess.emit_err( + crate::errors::ReturnTypeNotationIllegalParam::Const { + span: path_span, + param_span: tcx.def_span(param.def_id), + }, + ); + emitted_bad_param_err = true; + } + let ty = tcx + .type_of(param.def_id) + .no_bound_vars() + .expect("ct params cannot have early bound vars"); + tcx.mk_const( + ty::ConstKind::Bound( + ty::INNERMOST, + ty::BoundVar::from_usize(num_bound_vars), + ), + ty, + ) + .into() + } + }; + num_bound_vars += 1; + subst + }); + + // Next, we need to check that the return-type notation is being used on + // an RPITIT (return-position impl trait in trait) or AFIT (async fn in trait). + let output = tcx.fn_sig(assoc_item.def_id).skip_binder().output(); + let output = if let ty::Alias(ty::Projection, alias_ty) = *output.skip_binder().kind() + && tcx.def_kind(alias_ty.def_id) == DefKind::ImplTraitPlaceholder + { + alias_ty + } else { + return Err(self.tcx().sess.emit_err( + crate::errors::ReturnTypeNotationOnNonRpitit { + span: binding.span, + ty: tcx.liberate_late_bound_regions(assoc_item.def_id, output), + fn_span: tcx.hir().span_if_local(assoc_item.def_id), + note: (), + }, + )); + }; + + // Finally, move the fn return type's bound vars over to account for the early bound + // params (and trait ref's late bound params). This logic is very similar to + // `Predicate::subst_supertrait`, and it's no coincidence why. + let shifted_output = tcx.shift_bound_var_indices(num_bound_vars, output); + let subst_output = ty::EarlyBinder::bind(shifted_output).subst(tcx, substs); + + let bound_vars = tcx.late_bound_vars(binding.hir_id); + ty::Binder::bind_with_vars(subst_output, bound_vars) + } else { + // Include substitutions for generic parameters of associated types + candidate.map_bound(|trait_ref| { + let ident = Ident::new(assoc_item.name, binding.item_name.span); + let item_segment = hir::PathSegment { + ident, + hir_id: binding.hir_id, + res: Res::Err, + args: Some(binding.gen_args), + infer_args: false, + }; + + let substs_trait_ref_and_assoc_item = self.create_substs_for_associated_item( + path_span, + assoc_item.def_id, + &item_segment, + trait_ref.substs, + ); + + debug!(?substs_trait_ref_and_assoc_item); + + tcx.mk_alias_ty(assoc_item.def_id, substs_trait_ref_and_assoc_item) + }) + }; + + if !speculative { + // Find any late-bound regions declared in `ty` that are not + // declared in the trait-ref or assoc_item. These are not well-formed. + // + // Example: + // + // for<'a> ::Item = &'a str // <-- 'a is bad + // for<'a> >::Output = &'a str // <-- 'a is ok + if let ConvertedBindingKind::Equality(ty) = binding.kind { + let late_bound_in_trait_ref = + tcx.collect_constrained_late_bound_regions(&projection_ty); + let late_bound_in_ty = + tcx.collect_referenced_late_bound_regions(&trait_ref.rebind(ty)); + debug!(?late_bound_in_trait_ref); + debug!(?late_bound_in_ty); + + // FIXME: point at the type params that don't have appropriate lifetimes: + // struct S1 Fn(&i32, &i32) -> &'a i32>(F); + // ---- ---- ^^^^^^^ + self.validate_late_bound_regions( + late_bound_in_trait_ref, + late_bound_in_ty, + |br_name| { + struct_span_err!( + tcx.sess, + binding.span, + E0582, + "binding for associated type `{}` references {}, \ + which does not appear in the trait input types", + binding.item_name, + br_name + ) + }, + ); + } + } + + match binding.kind { + ConvertedBindingKind::Equality(..) if return_type_notation => { + return Err(self.tcx().sess.emit_err( + crate::errors::ReturnTypeNotationEqualityBound { span: binding.span }, + )); + } + ConvertedBindingKind::Equality(mut term) => { + // "Desugar" a constraint like `T: Iterator` this to + // the "projection predicate" for: + // + // `::Item = u32` + let assoc_item_def_id = projection_ty.skip_binder().def_id; + let def_kind = tcx.def_kind(assoc_item_def_id); + match (def_kind, term.unpack()) { + (hir::def::DefKind::AssocTy, ty::TermKind::Ty(_)) + | (hir::def::DefKind::AssocConst, ty::TermKind::Const(_)) => (), + (_, _) => { + let got = if let Some(_) = term.ty() { "type" } else { "constant" }; + let expected = tcx.def_descr(assoc_item_def_id); + let mut err = tcx.sess.struct_span_err( + binding.span, + format!("expected {expected} bound, found {got}"), + ); + err.span_note( + tcx.def_span(assoc_item_def_id), + format!("{expected} defined here"), + ); + + if let hir::def::DefKind::AssocConst = def_kind + && let Some(t) = term.ty() && (t.is_enum() || t.references_error()) + && tcx.features().associated_const_equality { + err.span_suggestion( + binding.span, + "if equating a const, try wrapping with braces", + format!("{} = {{ const }}", binding.item_name), + Applicability::HasPlaceholders, + ); + } + let reported = err.emit(); + term = match def_kind { + hir::def::DefKind::AssocTy => tcx.ty_error(reported).into(), + hir::def::DefKind::AssocConst => tcx + .const_error( + tcx.type_of(assoc_item_def_id) + .subst(tcx, projection_ty.skip_binder().substs), + reported, + ) + .into(), + _ => unreachable!(), + }; + } + } + bounds.push_projection_bound( + tcx, + projection_ty + .map_bound(|projection_ty| ty::ProjectionPredicate { projection_ty, term }), + binding.span, + ); + } + ConvertedBindingKind::Constraint(ast_bounds) => { + // "Desugar" a constraint like `T: Iterator` to + // + // `::Item: Debug` + // + // Calling `skip_binder` is okay, because `add_bounds` expects the `param_ty` + // parameter to have a skipped binder. + // + // NOTE: If `only_self_bounds` is true, do NOT expand this associated + // type bound into a trait predicate, since we only want to add predicates + // for the `Self` type. + if !only_self_bounds.0 { + let param_ty = tcx.mk_alias(ty::Projection, projection_ty.skip_binder()); + self.add_bounds( + param_ty, + ast_bounds.iter(), + bounds, + projection_ty.bound_vars(), + only_self_bounds, + ); + } + } + } + Ok(()) + } +} diff --git a/compiler/rustc_hir_analysis/src/astconv/mod.rs b/compiler/rustc_hir_analysis/src/astconv/mod.rs index f29ed903c95d7..d6645b784c439 100644 --- a/compiler/rustc_hir_analysis/src/astconv/mod.rs +++ b/compiler/rustc_hir_analysis/src/astconv/mod.rs @@ -2,6 +2,7 @@ //! The main routine here is `ast_ty_to_ty()`; each use is parameterized by an //! instance of `AstConv`. +mod bounds; mod errors; pub mod generics; mod lint; @@ -11,8 +12,7 @@ use crate::astconv::generics::{check_generic_arg_count, create_substs_for_generi use crate::bounds::Bounds; use crate::collect::HirPlaceholderCollector; use crate::errors::{ - AmbiguousLifetimeBound, MultipleRelaxedDefaultBounds, TraitObjectDeclaredWithNoTraits, - TypeofReservedKeywordUsed, ValueOfAssociatedStructAlreadySpecified, + AmbiguousLifetimeBound, TraitObjectDeclaredWithNoTraits, TypeofReservedKeywordUsed, }; use crate::middle::resolve_bound_vars as rbv; use crate::require_c_abi_if_c_variadic; @@ -885,571 +885,6 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o { .is_some() } - /// Sets `implicitly_sized` to true on `Bounds` if necessary - pub(crate) fn add_implicitly_sized( - &self, - bounds: &mut Bounds<'tcx>, - self_ty: Ty<'tcx>, - ast_bounds: &'tcx [hir::GenericBound<'tcx>], - self_ty_where_predicates: Option<(LocalDefId, &'tcx [hir::WherePredicate<'tcx>])>, - span: Span, - ) { - let tcx = self.tcx(); - - // Try to find an unbound in bounds. - let mut unbound = None; - let mut search_bounds = |ast_bounds: &'tcx [hir::GenericBound<'tcx>]| { - for ab in ast_bounds { - if let hir::GenericBound::Trait(ptr, hir::TraitBoundModifier::Maybe) = ab { - if unbound.is_none() { - unbound = Some(&ptr.trait_ref); - } else { - tcx.sess.emit_err(MultipleRelaxedDefaultBounds { span }); - } - } - } - }; - search_bounds(ast_bounds); - if let Some((self_ty, where_clause)) = self_ty_where_predicates { - for clause in where_clause { - if let hir::WherePredicate::BoundPredicate(pred) = clause { - if pred.is_param_bound(self_ty.to_def_id()) { - search_bounds(pred.bounds); - } - } - } - } - - let sized_def_id = tcx.lang_items().sized_trait(); - match (&sized_def_id, unbound) { - (Some(sized_def_id), Some(tpb)) - if tpb.path.res == Res::Def(DefKind::Trait, *sized_def_id) => - { - // There was in fact a `?Sized` bound, return without doing anything - return; - } - (_, Some(_)) => { - // There was a `?Trait` bound, but it was not `?Sized`; warn. - tcx.sess.span_warn( - span, - "default bound relaxed for a type parameter, but \ - this does nothing because the given bound is not \ - a default; only `?Sized` is supported", - ); - // Otherwise, add implicitly sized if `Sized` is available. - } - _ => { - // There was no `?Sized` bound; add implicitly sized if `Sized` is available. - } - } - if sized_def_id.is_none() { - // No lang item for `Sized`, so we can't add it as a bound. - return; - } - bounds.push_sized(tcx, self_ty, span); - } - - /// This helper takes a *converted* parameter type (`param_ty`) - /// and an *unconverted* list of bounds: - /// - /// ```text - /// fn foo - /// ^ ^^^^^ `ast_bounds` parameter, in HIR form - /// | - /// `param_ty`, in ty form - /// ``` - /// - /// It adds these `ast_bounds` into the `bounds` structure. - /// - /// **A note on binders:** there is an implied binder around - /// `param_ty` and `ast_bounds`. See `instantiate_poly_trait_ref` - /// for more details. - #[instrument(level = "debug", skip(self, ast_bounds, bounds))] - pub(crate) fn add_bounds<'hir, I: Iterator>>( - &self, - param_ty: Ty<'tcx>, - ast_bounds: I, - bounds: &mut Bounds<'tcx>, - bound_vars: &'tcx ty::List, - only_self_bounds: OnlySelfBounds, - ) { - for ast_bound in ast_bounds { - match ast_bound { - hir::GenericBound::Trait(poly_trait_ref, modifier) => { - let (constness, polarity) = match modifier { - hir::TraitBoundModifier::MaybeConst => { - (ty::BoundConstness::ConstIfConst, ty::ImplPolarity::Positive) - } - hir::TraitBoundModifier::None => { - (ty::BoundConstness::NotConst, ty::ImplPolarity::Positive) - } - hir::TraitBoundModifier::Negative => { - (ty::BoundConstness::NotConst, ty::ImplPolarity::Negative) - } - hir::TraitBoundModifier::Maybe => continue, - }; - let _ = self.instantiate_poly_trait_ref( - &poly_trait_ref.trait_ref, - poly_trait_ref.span, - constness, - polarity, - param_ty, - bounds, - false, - only_self_bounds, - ); - } - &hir::GenericBound::LangItemTrait(lang_item, span, hir_id, args) => { - self.instantiate_lang_item_trait_ref( - lang_item, - span, - hir_id, - args, - param_ty, - bounds, - only_self_bounds, - ); - } - hir::GenericBound::Outlives(lifetime) => { - let region = self.ast_region_to_region(lifetime, None); - bounds.push_region_bound( - self.tcx(), - ty::Binder::bind_with_vars( - ty::OutlivesPredicate(param_ty, region), - bound_vars, - ), - lifetime.ident.span, - ); - } - } - } - } - - /// Translates a list of bounds from the HIR into the `Bounds` data structure. - /// The self-type for the bounds is given by `param_ty`. - /// - /// Example: - /// - /// ```ignore (illustrative) - /// fn foo() { } - /// // ^ ^^^^^^^^^ ast_bounds - /// // param_ty - /// ``` - /// - /// The `sized_by_default` parameter indicates if, in this context, the `param_ty` should be - /// considered `Sized` unless there is an explicit `?Sized` bound. This would be true in the - /// example above, but is not true in supertrait listings like `trait Foo: Bar + Baz`. - /// - /// `span` should be the declaration size of the parameter. - pub(crate) fn compute_bounds( - &self, - param_ty: Ty<'tcx>, - ast_bounds: &[hir::GenericBound<'_>], - only_self_bounds: OnlySelfBounds, - ) -> Bounds<'tcx> { - let mut bounds = Bounds::default(); - self.add_bounds( - param_ty, - ast_bounds.iter(), - &mut bounds, - ty::List::empty(), - only_self_bounds, - ); - debug!(?bounds); - - bounds - } - - /// Convert the bounds in `ast_bounds` that refer to traits which define an associated type - /// named `assoc_name` into ty::Bounds. Ignore the rest. - pub(crate) fn compute_bounds_that_match_assoc_item( - &self, - param_ty: Ty<'tcx>, - ast_bounds: &[hir::GenericBound<'_>], - assoc_name: Ident, - ) -> Bounds<'tcx> { - let mut result = Vec::new(); - - for ast_bound in ast_bounds { - if let Some(trait_ref) = ast_bound.trait_ref() - && let Some(trait_did) = trait_ref.trait_def_id() - && self.tcx().trait_may_define_assoc_item(trait_did, assoc_name) - { - result.push(ast_bound.clone()); - } - } - - let mut bounds = Bounds::default(); - self.add_bounds( - param_ty, - result.iter(), - &mut bounds, - ty::List::empty(), - OnlySelfBounds(true), - ); - debug!(?bounds); - - bounds - } - - /// Given an HIR binding like `Item = Foo` or `Item: Foo`, pushes the corresponding predicates - /// onto `bounds`. - /// - /// **A note on binders:** given something like `T: for<'a> Iterator`, the - /// `trait_ref` here will be `for<'a> T: Iterator`. The `binding` data however is from *inside* - /// the binder (e.g., `&'a u32`) and hence may reference bound regions. - #[instrument(level = "debug", skip(self, bounds, speculative, dup_bindings, path_span))] - fn add_predicates_for_ast_type_binding( - &self, - hir_ref_id: hir::HirId, - trait_ref: ty::PolyTraitRef<'tcx>, - binding: &ConvertedBinding<'_, 'tcx>, - bounds: &mut Bounds<'tcx>, - speculative: bool, - dup_bindings: &mut FxHashMap, - path_span: Span, - constness: ty::BoundConstness, - only_self_bounds: OnlySelfBounds, - polarity: ty::ImplPolarity, - ) -> Result<(), ErrorGuaranteed> { - // Given something like `U: SomeTrait`, we want to produce a - // predicate like `::T = X`. This is somewhat - // subtle in the event that `T` is defined in a supertrait of - // `SomeTrait`, because in that case we need to upcast. - // - // That is, consider this case: - // - // ``` - // trait SubTrait: SuperTrait { } - // trait SuperTrait { type T; } - // - // ... B: SubTrait ... - // ``` - // - // We want to produce `>::T == foo`. - - let tcx = self.tcx(); - - let return_type_notation = - binding.gen_args.parenthesized == hir::GenericArgsParentheses::ReturnTypeNotation; - - let candidate = if return_type_notation { - if self.trait_defines_associated_item_named( - trait_ref.def_id(), - ty::AssocKind::Fn, - binding.item_name, - ) { - trait_ref - } else { - self.one_bound_for_assoc_method( - traits::supertraits(tcx, trait_ref), - trait_ref.print_only_trait_path(), - binding.item_name, - path_span, - )? - } - } else if self.trait_defines_associated_item_named( - trait_ref.def_id(), - ty::AssocKind::Type, - binding.item_name, - ) { - // Simple case: X is defined in the current trait. - trait_ref - } else { - // Otherwise, we have to walk through the supertraits to find - // those that do. - self.one_bound_for_assoc_type( - || traits::supertraits(tcx, trait_ref), - trait_ref.skip_binder().print_only_trait_name(), - binding.item_name, - path_span, - match binding.kind { - ConvertedBindingKind::Equality(term) => Some(term), - _ => None, - }, - )? - }; - - let (assoc_ident, def_scope) = - tcx.adjust_ident_and_get_scope(binding.item_name, candidate.def_id(), hir_ref_id); - - // We have already adjusted the item name above, so compare with `ident.normalize_to_macros_2_0()` instead - // of calling `filter_by_name_and_kind`. - let find_item_of_kind = |kind| { - tcx.associated_items(candidate.def_id()) - .filter_by_name_unhygienic(assoc_ident.name) - .find(|i| i.kind == kind && i.ident(tcx).normalize_to_macros_2_0() == assoc_ident) - }; - let assoc_item = if return_type_notation { - find_item_of_kind(ty::AssocKind::Fn) - } else { - find_item_of_kind(ty::AssocKind::Type) - .or_else(|| find_item_of_kind(ty::AssocKind::Const)) - } - .expect("missing associated type"); - - if !assoc_item.visibility(tcx).is_accessible_from(def_scope, tcx) { - tcx.sess - .struct_span_err( - binding.span, - format!("{} `{}` is private", assoc_item.kind, binding.item_name), - ) - .span_label(binding.span, format!("private {}", assoc_item.kind)) - .emit(); - } - tcx.check_stability(assoc_item.def_id, Some(hir_ref_id), binding.span, None); - - if !speculative { - dup_bindings - .entry(assoc_item.def_id) - .and_modify(|prev_span| { - tcx.sess.emit_err(ValueOfAssociatedStructAlreadySpecified { - span: binding.span, - prev_span: *prev_span, - item_name: binding.item_name, - def_path: tcx.def_path_str(assoc_item.container_id(tcx)), - }); - }) - .or_insert(binding.span); - } - - let projection_ty = if return_type_notation { - let mut emitted_bad_param_err = false; - // If we have an method return type bound, then we need to substitute - // the method's early bound params with suitable late-bound params. - let mut num_bound_vars = candidate.bound_vars().len(); - let substs = - candidate.skip_binder().substs.extend_to(tcx, assoc_item.def_id, |param, _| { - let subst = match param.kind { - GenericParamDefKind::Lifetime => ty::Region::new_late_bound( - tcx, - ty::INNERMOST, - ty::BoundRegion { - var: ty::BoundVar::from_usize(num_bound_vars), - kind: ty::BoundRegionKind::BrNamed(param.def_id, param.name), - }, - ) - .into(), - GenericParamDefKind::Type { .. } => { - if !emitted_bad_param_err { - tcx.sess.emit_err( - crate::errors::ReturnTypeNotationIllegalParam::Type { - span: path_span, - param_span: tcx.def_span(param.def_id), - }, - ); - emitted_bad_param_err = true; - } - tcx.mk_bound( - ty::INNERMOST, - ty::BoundTy { - var: ty::BoundVar::from_usize(num_bound_vars), - kind: ty::BoundTyKind::Param(param.def_id, param.name), - }, - ) - .into() - } - GenericParamDefKind::Const { .. } => { - if !emitted_bad_param_err { - tcx.sess.emit_err( - crate::errors::ReturnTypeNotationIllegalParam::Const { - span: path_span, - param_span: tcx.def_span(param.def_id), - }, - ); - emitted_bad_param_err = true; - } - let ty = tcx - .type_of(param.def_id) - .no_bound_vars() - .expect("ct params cannot have early bound vars"); - tcx.mk_const( - ty::ConstKind::Bound( - ty::INNERMOST, - ty::BoundVar::from_usize(num_bound_vars), - ), - ty, - ) - .into() - } - }; - num_bound_vars += 1; - subst - }); - - // Next, we need to check that the return-type notation is being used on - // an RPITIT (return-position impl trait in trait) or AFIT (async fn in trait). - let output = tcx.fn_sig(assoc_item.def_id).skip_binder().output(); - let output = if let ty::Alias(ty::Projection, alias_ty) = *output.skip_binder().kind() - && tcx.def_kind(alias_ty.def_id) == DefKind::ImplTraitPlaceholder - { - alias_ty - } else { - return Err(self.tcx().sess.emit_err( - crate::errors::ReturnTypeNotationOnNonRpitit { - span: binding.span, - ty: tcx.liberate_late_bound_regions(assoc_item.def_id, output), - fn_span: tcx.hir().span_if_local(assoc_item.def_id), - note: (), - }, - )); - }; - - // Finally, move the fn return type's bound vars over to account for the early bound - // params (and trait ref's late bound params). This logic is very similar to - // `Predicate::subst_supertrait`, and it's no coincidence why. - let shifted_output = tcx.shift_bound_var_indices(num_bound_vars, output); - let subst_output = ty::EarlyBinder::bind(shifted_output).subst(tcx, substs); - - let bound_vars = tcx.late_bound_vars(binding.hir_id); - ty::Binder::bind_with_vars(subst_output, bound_vars) - } else { - // Include substitutions for generic parameters of associated types - candidate.map_bound(|trait_ref| { - let ident = Ident::new(assoc_item.name, binding.item_name.span); - let item_segment = hir::PathSegment { - ident, - hir_id: binding.hir_id, - res: Res::Err, - args: Some(binding.gen_args), - infer_args: false, - }; - - let substs_trait_ref_and_assoc_item = self.create_substs_for_associated_item( - path_span, - assoc_item.def_id, - &item_segment, - trait_ref.substs, - ); - - debug!(?substs_trait_ref_and_assoc_item); - - tcx.mk_alias_ty(assoc_item.def_id, substs_trait_ref_and_assoc_item) - }) - }; - - if !speculative { - // Find any late-bound regions declared in `ty` that are not - // declared in the trait-ref or assoc_item. These are not well-formed. - // - // Example: - // - // for<'a> ::Item = &'a str // <-- 'a is bad - // for<'a> >::Output = &'a str // <-- 'a is ok - if let ConvertedBindingKind::Equality(ty) = binding.kind { - let late_bound_in_trait_ref = - tcx.collect_constrained_late_bound_regions(&projection_ty); - let late_bound_in_ty = - tcx.collect_referenced_late_bound_regions(&trait_ref.rebind(ty)); - debug!(?late_bound_in_trait_ref); - debug!(?late_bound_in_ty); - - // FIXME: point at the type params that don't have appropriate lifetimes: - // struct S1 Fn(&i32, &i32) -> &'a i32>(F); - // ---- ---- ^^^^^^^ - self.validate_late_bound_regions( - late_bound_in_trait_ref, - late_bound_in_ty, - |br_name| { - struct_span_err!( - tcx.sess, - binding.span, - E0582, - "binding for associated type `{}` references {}, \ - which does not appear in the trait input types", - binding.item_name, - br_name - ) - }, - ); - } - } - - match binding.kind { - ConvertedBindingKind::Equality(..) if return_type_notation => { - return Err(self.tcx().sess.emit_err( - crate::errors::ReturnTypeNotationEqualityBound { span: binding.span }, - )); - } - ConvertedBindingKind::Equality(mut term) => { - // "Desugar" a constraint like `T: Iterator` this to - // the "projection predicate" for: - // - // `::Item = u32` - let assoc_item_def_id = projection_ty.skip_binder().def_id; - let def_kind = tcx.def_kind(assoc_item_def_id); - match (def_kind, term.unpack()) { - (hir::def::DefKind::AssocTy, ty::TermKind::Ty(_)) - | (hir::def::DefKind::AssocConst, ty::TermKind::Const(_)) => (), - (_, _) => { - let got = if let Some(_) = term.ty() { "type" } else { "constant" }; - let expected = tcx.def_descr(assoc_item_def_id); - let mut err = tcx.sess.struct_span_err( - binding.span, - format!("expected {expected} bound, found {got}"), - ); - err.span_note( - tcx.def_span(assoc_item_def_id), - format!("{expected} defined here"), - ); - - if let hir::def::DefKind::AssocConst = def_kind - && let Some(t) = term.ty() && (t.is_enum() || t.references_error()) - && tcx.features().associated_const_equality { - err.span_suggestion( - binding.span, - "if equating a const, try wrapping with braces", - format!("{} = {{ const }}", binding.item_name), - Applicability::HasPlaceholders, - ); - } - let reported = err.emit(); - term = match def_kind { - hir::def::DefKind::AssocTy => tcx.ty_error(reported).into(), - hir::def::DefKind::AssocConst => tcx - .const_error( - tcx.type_of(assoc_item_def_id) - .subst(tcx, projection_ty.skip_binder().substs), - reported, - ) - .into(), - _ => unreachable!(), - }; - } - } - bounds.push_projection_bound( - tcx, - projection_ty - .map_bound(|projection_ty| ty::ProjectionPredicate { projection_ty, term }), - binding.span, - ); - } - ConvertedBindingKind::Constraint(ast_bounds) => { - // "Desugar" a constraint like `T: Iterator` to - // - // `::Item: Debug` - // - // Calling `skip_binder` is okay, because `add_bounds` expects the `param_ty` - // parameter to have a skipped binder. - // - // NOTE: If `only_self_bounds` is true, do NOT expand this associated - // type bound into a trait predicate, since we only want to add predicates - // for the `Self` type. - if !only_self_bounds.0 { - let param_ty = tcx.mk_alias(ty::Projection, projection_ty.skip_binder()); - self.add_bounds( - param_ty, - ast_bounds.iter(), - bounds, - projection_ty.bound_vars(), - only_self_bounds, - ); - } - } - } - Ok(()) - } - fn ast_path_to_ty( &self, span: Span,