From 20431706a863f92cb37dc512fef6e48d192aaf2c Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Wed, 17 Apr 2024 14:11:38 +0200 Subject: Merging upstream version 1.66.0+dfsg1. Signed-off-by: Daniel Baumann --- .../rustc_hir_analysis/src/collect/generics_of.rs | 481 +++++ .../rustc_hir_analysis/src/collect/item_bounds.rs | 110 ++ .../rustc_hir_analysis/src/collect/lifetimes.rs | 1888 ++++++++++++++++++++ .../src/collect/predicates_of.rs | 707 ++++++++ compiler/rustc_hir_analysis/src/collect/type_of.rs | 966 ++++++++++ 5 files changed, 4152 insertions(+) create mode 100644 compiler/rustc_hir_analysis/src/collect/generics_of.rs create mode 100644 compiler/rustc_hir_analysis/src/collect/item_bounds.rs create mode 100644 compiler/rustc_hir_analysis/src/collect/lifetimes.rs create mode 100644 compiler/rustc_hir_analysis/src/collect/predicates_of.rs create mode 100644 compiler/rustc_hir_analysis/src/collect/type_of.rs (limited to 'compiler/rustc_hir_analysis/src/collect') diff --git a/compiler/rustc_hir_analysis/src/collect/generics_of.rs b/compiler/rustc_hir_analysis/src/collect/generics_of.rs new file mode 100644 index 000000000..c7777a946 --- /dev/null +++ b/compiler/rustc_hir_analysis/src/collect/generics_of.rs @@ -0,0 +1,481 @@ +use crate::middle::resolve_lifetime as rl; +use hir::{ + intravisit::{self, Visitor}, + GenericParamKind, HirId, Node, +}; +use rustc_hir as hir; +use rustc_hir::def::DefKind; +use rustc_hir::def_id::DefId; +use rustc_middle::ty::{self, TyCtxt}; +use rustc_session::lint; +use rustc_span::symbol::{kw, Symbol}; +use rustc_span::Span; + +pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::Generics { + use rustc_hir::*; + + let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local()); + + let node = tcx.hir().get(hir_id); + let parent_def_id = match node { + Node::ImplItem(_) + | Node::TraitItem(_) + | Node::Variant(_) + | Node::Ctor(..) + | Node::Field(_) => { + let parent_id = tcx.hir().get_parent_item(hir_id); + Some(parent_id.to_def_id()) + } + // FIXME(#43408) always enable this once `lazy_normalization` is + // stable enough and does not need a feature gate anymore. + Node::AnonConst(_) => { + let parent_def_id = tcx.hir().get_parent_item(hir_id); + + let mut in_param_ty = false; + for (_parent, node) in tcx.hir().parent_iter(hir_id) { + if let Some(generics) = node.generics() { + let mut visitor = AnonConstInParamTyDetector { + in_param_ty: false, + found_anon_const_in_param_ty: false, + ct: hir_id, + }; + + visitor.visit_generics(generics); + in_param_ty = visitor.found_anon_const_in_param_ty; + break; + } + } + + if in_param_ty { + // We do not allow generic parameters in anon consts if we are inside + // of a const parameter type, e.g. `struct Foo` is not allowed. + None + } else if tcx.lazy_normalization() { + if let Some(param_id) = tcx.hir().opt_const_param_default_param_hir_id(hir_id) { + // If the def_id we are calling generics_of on is an anon ct default i.e: + // + // struct Foo; + // ^^^ ^ ^^^^^^ def id of this anon const + // ^ ^ param_id + // ^ parent_def_id + // + // then we only want to return generics for params to the left of `N`. If we don't do that we + // end up with that const looking like: `ty::ConstKind::Unevaluated(def_id, substs: [N#0])`. + // + // This causes ICEs (#86580) when building the substs for Foo in `fn foo() -> Foo { .. }` as + // we substitute the defaults with the partially built substs when we build the substs. Subst'ing + // the `N#0` on the unevaluated const indexes into the empty substs we're in the process of building. + // + // We fix this by having this function return the parent's generics ourselves and truncating the + // generics to only include non-forward declared params (with the exception of the `Self` ty) + // + // For the above code example that means we want `substs: []` + // For the following struct def we want `substs: [N#0]` when generics_of is called on + // the def id of the `{ N + 1 }` anon const + // struct Foo; + // + // This has some implications for how we get the predicates available to the anon const + // see `explicit_predicates_of` for more information on this + let generics = tcx.generics_of(parent_def_id.to_def_id()); + let param_def = tcx.hir().local_def_id(param_id).to_def_id(); + let param_def_idx = generics.param_def_id_to_index[¶m_def]; + // In the above example this would be .params[..N#0] + let params = generics.params[..param_def_idx as usize].to_owned(); + let param_def_id_to_index = + params.iter().map(|param| (param.def_id, param.index)).collect(); + + return ty::Generics { + // we set the parent of these generics to be our parent's parent so that we + // dont end up with substs: [N, M, N] for the const default on a struct like this: + // struct Foo; + parent: generics.parent, + parent_count: generics.parent_count, + params, + param_def_id_to_index, + has_self: generics.has_self, + has_late_bound_regions: generics.has_late_bound_regions, + }; + } + + // HACK(eddyb) this provides the correct generics when + // `feature(generic_const_expressions)` is enabled, so that const expressions + // used with const generics, e.g. `Foo<{N+1}>`, can work at all. + // + // Note that we do not supply the parent generics when using + // `min_const_generics`. + Some(parent_def_id.to_def_id()) + } else { + let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id)); + match parent_node { + // HACK(eddyb) this provides the correct generics for repeat + // expressions' count (i.e. `N` in `[x; N]`), and explicit + // `enum` discriminants (i.e. `D` in `enum Foo { Bar = D }`), + // as they shouldn't be able to cause query cycle errors. + Node::Expr(&Expr { kind: ExprKind::Repeat(_, ref constant), .. }) + if constant.hir_id() == hir_id => + { + Some(parent_def_id.to_def_id()) + } + Node::Variant(Variant { disr_expr: Some(ref constant), .. }) + if constant.hir_id == hir_id => + { + Some(parent_def_id.to_def_id()) + } + Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) => { + Some(tcx.typeck_root_def_id(def_id)) + } + // Exclude `GlobalAsm` here which cannot have generics. + Node::Expr(&Expr { kind: ExprKind::InlineAsm(asm), .. }) + if asm.operands.iter().any(|(op, _op_sp)| match op { + hir::InlineAsmOperand::Const { anon_const } + | hir::InlineAsmOperand::SymFn { anon_const } => { + anon_const.hir_id == hir_id + } + _ => false, + }) => + { + Some(parent_def_id.to_def_id()) + } + _ => None, + } + } + } + Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure { .. }, .. }) => { + Some(tcx.typeck_root_def_id(def_id)) + } + Node::Item(item) => match item.kind { + ItemKind::OpaqueTy(hir::OpaqueTy { + origin: + hir::OpaqueTyOrigin::FnReturn(fn_def_id) | hir::OpaqueTyOrigin::AsyncFn(fn_def_id), + in_trait, + .. + }) => { + if in_trait { + assert!(matches!(tcx.def_kind(fn_def_id), DefKind::AssocFn)) + } else { + assert!(matches!(tcx.def_kind(fn_def_id), DefKind::AssocFn | DefKind::Fn)) + } + Some(fn_def_id.to_def_id()) + } + ItemKind::OpaqueTy(hir::OpaqueTy { origin: hir::OpaqueTyOrigin::TyAlias, .. }) => { + let parent_id = tcx.hir().get_parent_item(hir_id); + assert_ne!(parent_id, hir::CRATE_OWNER_ID); + debug!("generics_of: parent of opaque ty {:?} is {:?}", def_id, parent_id); + // Opaque types are always nested within another item, and + // inherit the generics of the item. + Some(parent_id.to_def_id()) + } + _ => None, + }, + _ => None, + }; + + enum Defaults { + Allowed, + // See #36887 + FutureCompatDisallowed, + Deny, + } + + let no_generics = hir::Generics::empty(); + let ast_generics = node.generics().unwrap_or(&no_generics); + let (opt_self, allow_defaults) = match node { + Node::Item(item) => { + match item.kind { + ItemKind::Trait(..) | ItemKind::TraitAlias(..) => { + // Add in the self type parameter. + // + // Something of a hack: use the node id for the trait, also as + // the node id for the Self type parameter. + let opt_self = Some(ty::GenericParamDef { + index: 0, + name: kw::SelfUpper, + def_id, + pure_wrt_drop: false, + kind: ty::GenericParamDefKind::Type { + has_default: false, + synthetic: false, + }, + }); + + (opt_self, Defaults::Allowed) + } + ItemKind::TyAlias(..) + | ItemKind::Enum(..) + | ItemKind::Struct(..) + | ItemKind::OpaqueTy(..) + | ItemKind::Union(..) => (None, Defaults::Allowed), + _ => (None, Defaults::FutureCompatDisallowed), + } + } + + // GATs + Node::TraitItem(item) if matches!(item.kind, TraitItemKind::Type(..)) => { + (None, Defaults::Deny) + } + Node::ImplItem(item) if matches!(item.kind, ImplItemKind::Type(..)) => { + (None, Defaults::Deny) + } + + _ => (None, Defaults::FutureCompatDisallowed), + }; + + let has_self = opt_self.is_some(); + let mut parent_has_self = false; + let mut own_start = has_self as u32; + let parent_count = parent_def_id.map_or(0, |def_id| { + let generics = tcx.generics_of(def_id); + assert!(!has_self); + parent_has_self = generics.has_self; + own_start = generics.count() as u32; + generics.parent_count + generics.params.len() + }); + + let mut params: Vec<_> = Vec::with_capacity(ast_generics.params.len() + has_self as usize); + + if let Some(opt_self) = opt_self { + params.push(opt_self); + } + + let early_lifetimes = super::early_bound_lifetimes_from_generics(tcx, ast_generics); + params.extend(early_lifetimes.enumerate().map(|(i, param)| ty::GenericParamDef { + name: param.name.ident().name, + index: own_start + i as u32, + def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(), + pure_wrt_drop: param.pure_wrt_drop, + kind: ty::GenericParamDefKind::Lifetime, + })); + + // Now create the real type and const parameters. + let type_start = own_start - has_self as u32 + params.len() as u32; + let mut i = 0; + let mut next_index = || { + let prev = i; + i += 1; + prev as u32 + type_start + }; + + const TYPE_DEFAULT_NOT_ALLOWED: &'static str = "defaults for type parameters are only allowed in \ + `struct`, `enum`, `type`, or `trait` definitions"; + + params.extend(ast_generics.params.iter().filter_map(|param| match param.kind { + GenericParamKind::Lifetime { .. } => None, + GenericParamKind::Type { ref default, synthetic, .. } => { + if default.is_some() { + match allow_defaults { + Defaults::Allowed => {} + Defaults::FutureCompatDisallowed + if tcx.features().default_type_parameter_fallback => {} + Defaults::FutureCompatDisallowed => { + tcx.struct_span_lint_hir( + lint::builtin::INVALID_TYPE_PARAM_DEFAULT, + param.hir_id, + param.span, + TYPE_DEFAULT_NOT_ALLOWED, + |lint| lint, + ); + } + Defaults::Deny => { + tcx.sess.span_err(param.span, TYPE_DEFAULT_NOT_ALLOWED); + } + } + } + + let kind = ty::GenericParamDefKind::Type { has_default: default.is_some(), synthetic }; + + Some(ty::GenericParamDef { + index: next_index(), + name: param.name.ident().name, + def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(), + pure_wrt_drop: param.pure_wrt_drop, + kind, + }) + } + GenericParamKind::Const { default, .. } => { + if !matches!(allow_defaults, Defaults::Allowed) && default.is_some() { + tcx.sess.span_err( + param.span, + "defaults for const parameters are only allowed in \ + `struct`, `enum`, `type`, or `trait` definitions", + ); + } + + Some(ty::GenericParamDef { + index: next_index(), + name: param.name.ident().name, + def_id: tcx.hir().local_def_id(param.hir_id).to_def_id(), + pure_wrt_drop: param.pure_wrt_drop, + kind: ty::GenericParamDefKind::Const { has_default: default.is_some() }, + }) + } + })); + + // provide junk type parameter defs - the only place that + // cares about anything but the length is instantiation, + // and we don't do that for closures. + if let Node::Expr(&hir::Expr { + kind: hir::ExprKind::Closure(hir::Closure { movability: gen, .. }), + .. + }) = node + { + let dummy_args = if gen.is_some() { + &["", "", "", "", ""][..] + } else { + &["", "", ""][..] + }; + + params.extend(dummy_args.iter().map(|&arg| ty::GenericParamDef { + index: next_index(), + name: Symbol::intern(arg), + def_id, + pure_wrt_drop: false, + kind: ty::GenericParamDefKind::Type { has_default: false, synthetic: false }, + })); + } + + // provide junk type parameter defs for const blocks. + if let Node::AnonConst(_) = node { + let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id)); + if let Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) = parent_node { + params.push(ty::GenericParamDef { + index: next_index(), + name: Symbol::intern(""), + def_id, + pure_wrt_drop: false, + kind: ty::GenericParamDefKind::Type { has_default: false, synthetic: false }, + }); + } + } + + let param_def_id_to_index = params.iter().map(|param| (param.def_id, param.index)).collect(); + + ty::Generics { + parent: parent_def_id, + parent_count, + params, + param_def_id_to_index, + has_self: has_self || parent_has_self, + has_late_bound_regions: has_late_bound_regions(tcx, node), + } +} + +fn has_late_bound_regions<'tcx>(tcx: TyCtxt<'tcx>, node: Node<'tcx>) -> Option { + struct LateBoundRegionsDetector<'tcx> { + tcx: TyCtxt<'tcx>, + outer_index: ty::DebruijnIndex, + has_late_bound_regions: Option, + } + + impl<'tcx> Visitor<'tcx> for LateBoundRegionsDetector<'tcx> { + fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) { + if self.has_late_bound_regions.is_some() { + return; + } + match ty.kind { + hir::TyKind::BareFn(..) => { + self.outer_index.shift_in(1); + intravisit::walk_ty(self, ty); + self.outer_index.shift_out(1); + } + _ => intravisit::walk_ty(self, ty), + } + } + + fn visit_poly_trait_ref(&mut self, tr: &'tcx hir::PolyTraitRef<'tcx>) { + if self.has_late_bound_regions.is_some() { + return; + } + self.outer_index.shift_in(1); + intravisit::walk_poly_trait_ref(self, tr); + self.outer_index.shift_out(1); + } + + fn visit_lifetime(&mut self, lt: &'tcx hir::Lifetime) { + if self.has_late_bound_regions.is_some() { + return; + } + + match self.tcx.named_region(lt.hir_id) { + Some(rl::Region::Static | rl::Region::EarlyBound(..)) => {} + Some(rl::Region::LateBound(debruijn, _, _)) if debruijn < self.outer_index => {} + Some(rl::Region::LateBound(..) | rl::Region::Free(..)) | None => { + self.has_late_bound_regions = Some(lt.span); + } + } + } + } + + fn has_late_bound_regions<'tcx>( + tcx: TyCtxt<'tcx>, + generics: &'tcx hir::Generics<'tcx>, + decl: &'tcx hir::FnDecl<'tcx>, + ) -> Option { + let mut visitor = LateBoundRegionsDetector { + tcx, + outer_index: ty::INNERMOST, + has_late_bound_regions: None, + }; + for param in generics.params { + if let GenericParamKind::Lifetime { .. } = param.kind { + if tcx.is_late_bound(param.hir_id) { + return Some(param.span); + } + } + } + visitor.visit_fn_decl(decl); + visitor.has_late_bound_regions + } + + match node { + Node::TraitItem(item) => match item.kind { + hir::TraitItemKind::Fn(ref sig, _) => { + has_late_bound_regions(tcx, &item.generics, sig.decl) + } + _ => None, + }, + Node::ImplItem(item) => match item.kind { + hir::ImplItemKind::Fn(ref sig, _) => { + has_late_bound_regions(tcx, &item.generics, sig.decl) + } + _ => None, + }, + Node::ForeignItem(item) => match item.kind { + hir::ForeignItemKind::Fn(fn_decl, _, ref generics) => { + has_late_bound_regions(tcx, generics, fn_decl) + } + _ => None, + }, + Node::Item(item) => match item.kind { + hir::ItemKind::Fn(ref sig, .., ref generics, _) => { + has_late_bound_regions(tcx, generics, sig.decl) + } + _ => None, + }, + _ => None, + } +} + +struct AnonConstInParamTyDetector { + in_param_ty: bool, + found_anon_const_in_param_ty: bool, + ct: HirId, +} + +impl<'v> Visitor<'v> for AnonConstInParamTyDetector { + fn visit_generic_param(&mut self, p: &'v hir::GenericParam<'v>) { + if let GenericParamKind::Const { ty, default: _ } = p.kind { + let prev = self.in_param_ty; + self.in_param_ty = true; + self.visit_ty(ty); + self.in_param_ty = prev; + } + } + + fn visit_anon_const(&mut self, c: &'v hir::AnonConst) { + if self.in_param_ty && self.ct == c.hir_id { + self.found_anon_const_in_param_ty = true; + } else { + intravisit::walk_anon_const(self, c) + } + } +} diff --git a/compiler/rustc_hir_analysis/src/collect/item_bounds.rs b/compiler/rustc_hir_analysis/src/collect/item_bounds.rs new file mode 100644 index 000000000..0d34a8bfe --- /dev/null +++ b/compiler/rustc_hir_analysis/src/collect/item_bounds.rs @@ -0,0 +1,110 @@ +use super::ItemCtxt; +use crate::astconv::AstConv; +use rustc_hir as hir; +use rustc_infer::traits::util; +use rustc_middle::ty::subst::InternalSubsts; +use rustc_middle::ty::{self, DefIdTree, TyCtxt}; +use rustc_span::def_id::DefId; +use rustc_span::Span; + +/// For associated types we include both bounds written on the type +/// (`type X: Trait`) and predicates from the trait: `where Self::X: Trait`. +/// +/// Note that this filtering is done with the items identity substs to +/// simplify checking that these bounds are met in impls. This means that +/// a bound such as `for<'b> >::U: Clone` can't be used, as in +/// `hr-associated-type-bound-1.rs`. +fn associated_type_bounds<'tcx>( + tcx: TyCtxt<'tcx>, + assoc_item_def_id: DefId, + ast_bounds: &'tcx [hir::GenericBound<'tcx>], + span: Span, +) -> &'tcx [(ty::Predicate<'tcx>, Span)] { + let item_ty = tcx.mk_projection( + assoc_item_def_id, + InternalSubsts::identity_for_item(tcx, assoc_item_def_id), + ); + + let icx = ItemCtxt::new(tcx, assoc_item_def_id); + let mut bounds = >::compute_bounds(&icx, item_ty, ast_bounds); + // Associated types are implicitly sized unless a `?Sized` bound is found + >::add_implicitly_sized(&icx, &mut bounds, ast_bounds, None, span); + + let trait_def_id = tcx.parent(assoc_item_def_id); + let trait_predicates = tcx.trait_explicit_predicates_and_bounds(trait_def_id.expect_local()); + + let bounds_from_parent = trait_predicates.predicates.iter().copied().filter(|(pred, _)| { + match pred.kind().skip_binder() { + ty::PredicateKind::Trait(tr) => tr.self_ty() == item_ty, + ty::PredicateKind::Projection(proj) => proj.projection_ty.self_ty() == item_ty, + ty::PredicateKind::TypeOutlives(outlives) => outlives.0 == item_ty, + _ => false, + } + }); + + let all_bounds = tcx + .arena + .alloc_from_iter(bounds.predicates(tcx, item_ty).into_iter().chain(bounds_from_parent)); + debug!("associated_type_bounds({}) = {:?}", tcx.def_path_str(assoc_item_def_id), all_bounds); + all_bounds +} + +/// Opaque types don't inherit bounds from their parent: for return position +/// impl trait it isn't possible to write a suitable predicate on the +/// containing function and for type-alias impl trait we don't have a backwards +/// compatibility issue. +#[instrument(level = "trace", skip(tcx), ret)] +fn opaque_type_bounds<'tcx>( + tcx: TyCtxt<'tcx>, + opaque_def_id: DefId, + ast_bounds: &'tcx [hir::GenericBound<'tcx>], + span: Span, + in_trait: bool, +) -> &'tcx [(ty::Predicate<'tcx>, Span)] { + ty::print::with_no_queries!({ + let substs = InternalSubsts::identity_for_item(tcx, opaque_def_id); + let item_ty = if in_trait { + tcx.mk_projection(opaque_def_id, substs) + } else { + tcx.mk_opaque(opaque_def_id, substs) + }; + + let icx = ItemCtxt::new(tcx, opaque_def_id); + let mut bounds = >::compute_bounds(&icx, item_ty, ast_bounds); + // Opaque types are implicitly sized unless a `?Sized` bound is found + >::add_implicitly_sized(&icx, &mut bounds, ast_bounds, None, span); + debug!(?bounds); + + tcx.arena.alloc_from_iter(bounds.predicates(tcx, item_ty)) + }) +} + +pub(super) fn explicit_item_bounds( + tcx: TyCtxt<'_>, + def_id: DefId, +) -> &'_ [(ty::Predicate<'_>, Span)] { + let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local()); + match tcx.hir().get(hir_id) { + hir::Node::TraitItem(hir::TraitItem { + kind: hir::TraitItemKind::Type(bounds, _), + span, + .. + }) => associated_type_bounds(tcx, def_id, bounds, *span), + hir::Node::Item(hir::Item { + kind: hir::ItemKind::OpaqueTy(hir::OpaqueTy { bounds, in_trait, .. }), + span, + .. + }) => opaque_type_bounds(tcx, def_id, bounds, *span, *in_trait), + _ => bug!("item_bounds called on {:?}", def_id), + } +} + +pub(super) fn item_bounds(tcx: TyCtxt<'_>, def_id: DefId) -> &'_ ty::List> { + tcx.mk_predicates( + util::elaborate_predicates( + tcx, + tcx.explicit_item_bounds(def_id).iter().map(|&(bound, _span)| bound), + ) + .map(|obligation| obligation.predicate), + ) +} diff --git a/compiler/rustc_hir_analysis/src/collect/lifetimes.rs b/compiler/rustc_hir_analysis/src/collect/lifetimes.rs new file mode 100644 index 000000000..3f263a6de --- /dev/null +++ b/compiler/rustc_hir_analysis/src/collect/lifetimes.rs @@ -0,0 +1,1888 @@ +//! Resolution of early vs late bound lifetimes. +//! +//! Name resolution for lifetimes is performed on the AST and embedded into HIR. From this +//! information, typechecking needs to transform the lifetime parameters into bound lifetimes. +//! Lifetimes can be early-bound or late-bound. Construction of typechecking terms needs to visit +//! the types in HIR to identify late-bound lifetimes and assign their Debruijn indices. This file +//! is also responsible for assigning their semantics to implicit lifetimes in trait objects. + +use rustc_ast::walk_list; +use rustc_data_structures::fx::{FxHashSet, FxIndexMap, FxIndexSet}; +use rustc_errors::struct_span_err; +use rustc_hir as hir; +use rustc_hir::def::{DefKind, Res}; +use rustc_hir::def_id::LocalDefId; +use rustc_hir::intravisit::{self, Visitor}; +use rustc_hir::{GenericArg, GenericParam, GenericParamKind, HirIdMap, LifetimeName, Node}; +use rustc_middle::bug; +use rustc_middle::hir::map::Map; +use rustc_middle::hir::nested_filter; +use rustc_middle::middle::resolve_lifetime::*; +use rustc_middle::ty::{self, DefIdTree, TyCtxt}; +use rustc_span::def_id::DefId; +use rustc_span::symbol::{sym, Ident}; +use rustc_span::Span; +use std::fmt; + +trait RegionExt { + fn early(hir_map: Map<'_>, param: &GenericParam<'_>) -> (LocalDefId, Region); + + fn late(index: u32, hir_map: Map<'_>, param: &GenericParam<'_>) -> (LocalDefId, Region); + + fn id(&self) -> Option; + + fn shifted(self, amount: u32) -> Region; +} + +impl RegionExt for Region { + fn early(hir_map: Map<'_>, param: &GenericParam<'_>) -> (LocalDefId, Region) { + let def_id = hir_map.local_def_id(param.hir_id); + debug!("Region::early: def_id={:?}", def_id); + (def_id, Region::EarlyBound(def_id.to_def_id())) + } + + fn late(idx: u32, hir_map: Map<'_>, param: &GenericParam<'_>) -> (LocalDefId, Region) { + let depth = ty::INNERMOST; + let def_id = hir_map.local_def_id(param.hir_id); + debug!( + "Region::late: idx={:?}, param={:?} depth={:?} def_id={:?}", + idx, param, depth, def_id, + ); + (def_id, Region::LateBound(depth, idx, def_id.to_def_id())) + } + + fn id(&self) -> Option { + match *self { + Region::Static => None, + + Region::EarlyBound(id) | Region::LateBound(_, _, id) | Region::Free(_, id) => Some(id), + } + } + + fn shifted(self, amount: u32) -> Region { + match self { + Region::LateBound(debruijn, idx, id) => { + Region::LateBound(debruijn.shifted_in(amount), idx, id) + } + _ => self, + } + } +} + +/// Maps the id of each lifetime reference to the lifetime decl +/// that it corresponds to. +/// +/// FIXME. This struct gets converted to a `ResolveLifetimes` for +/// actual use. It has the same data, but indexed by `LocalDefId`. This +/// is silly. +#[derive(Debug, Default)] +struct NamedRegionMap { + // maps from every use of a named (not anonymous) lifetime to a + // `Region` describing how that region is bound + defs: HirIdMap, + + // Maps relevant hir items to the bound vars on them. These include: + // - function defs + // - function pointers + // - closures + // - trait refs + // - bound types (like `T` in `for<'a> T<'a>: Foo`) + late_bound_vars: HirIdMap>, +} + +struct LifetimeContext<'a, 'tcx> { + tcx: TyCtxt<'tcx>, + map: &'a mut NamedRegionMap, + scope: ScopeRef<'a>, + + /// Indicates that we only care about the definition of a trait. This should + /// be false if the `Item` we are resolving lifetimes for is not a trait or + /// we eventually need lifetimes resolve for trait items. + trait_definition_only: bool, +} + +#[derive(Debug)] +enum Scope<'a> { + /// Declares lifetimes, and each can be early-bound or late-bound. + /// The `DebruijnIndex` of late-bound lifetimes starts at `1` and + /// it should be shifted by the number of `Binder`s in between the + /// declaration `Binder` and the location it's referenced from. + Binder { + /// We use an IndexMap here because we want these lifetimes in order + /// for diagnostics. + lifetimes: FxIndexMap, + + scope_type: BinderScopeType, + + /// The late bound vars for a given item are stored by `HirId` to be + /// queried later. However, if we enter an elision scope, we have to + /// later append the elided bound vars to the list and need to know what + /// to append to. + hir_id: hir::HirId, + + s: ScopeRef<'a>, + + /// If this binder comes from a where clause, specify how it was created. + /// This is used to diagnose inaccessible lifetimes in APIT: + /// ```ignore (illustrative) + /// fn foo(x: impl for<'a> Trait<'a, Assoc = impl Copy + 'a>) {} + /// ``` + where_bound_origin: Option, + }, + + /// Lifetimes introduced by a fn are scoped to the call-site for that fn, + /// if this is a fn body, otherwise the original definitions are used. + /// Unspecified lifetimes are inferred, unless an elision scope is nested, + /// e.g., `(&T, fn(&T) -> &T);` becomes `(&'_ T, for<'a> fn(&'a T) -> &'a T)`. + Body { + id: hir::BodyId, + s: ScopeRef<'a>, + }, + + /// A scope which either determines unspecified lifetimes or errors + /// on them (e.g., due to ambiguity). + Elision { + s: ScopeRef<'a>, + }, + + /// Use a specific lifetime (if `Some`) or leave it unset (to be + /// inferred in a function body or potentially error outside one), + /// for the default choice of lifetime in a trait object type. + ObjectLifetimeDefault { + lifetime: Option, + s: ScopeRef<'a>, + }, + + /// When we have nested trait refs, we concatenate late bound vars for inner + /// trait refs from outer ones. But we also need to include any HRTB + /// lifetimes encountered when identifying the trait that an associated type + /// is declared on. + Supertrait { + lifetimes: Vec, + s: ScopeRef<'a>, + }, + + TraitRefBoundary { + s: ScopeRef<'a>, + }, + + Root, +} + +#[derive(Copy, Clone, Debug)] +enum BinderScopeType { + /// Any non-concatenating binder scopes. + Normal, + /// Within a syntactic trait ref, there may be multiple poly trait refs that + /// are nested (under the `associated_type_bounds` feature). The binders of + /// the inner poly trait refs are extended from the outer poly trait refs + /// and don't increase the late bound depth. If you had + /// `T: for<'a> Foo Baz<'a, 'b>>`, then the `for<'b>` scope + /// would be `Concatenating`. This also used in trait refs in where clauses + /// where we have two binders `for<> T: for<> Foo` (I've intentionally left + /// out any lifetimes because they aren't needed to show the two scopes). + /// The inner `for<>` has a scope of `Concatenating`. + Concatenating, +} + +// A helper struct for debugging scopes without printing parent scopes +struct TruncatedScopeDebug<'a>(&'a Scope<'a>); + +impl<'a> fmt::Debug for TruncatedScopeDebug<'a> { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + match self.0 { + Scope::Binder { lifetimes, scope_type, hir_id, where_bound_origin, s: _ } => f + .debug_struct("Binder") + .field("lifetimes", lifetimes) + .field("scope_type", scope_type) + .field("hir_id", hir_id) + .field("where_bound_origin", where_bound_origin) + .field("s", &"..") + .finish(), + Scope::Body { id, s: _ } => { + f.debug_struct("Body").field("id", id).field("s", &"..").finish() + } + Scope::Elision { s: _ } => f.debug_struct("Elision").field("s", &"..").finish(), + Scope::ObjectLifetimeDefault { lifetime, s: _ } => f + .debug_struct("ObjectLifetimeDefault") + .field("lifetime", lifetime) + .field("s", &"..") + .finish(), + Scope::Supertrait { lifetimes, s: _ } => f + .debug_struct("Supertrait") + .field("lifetimes", lifetimes) + .field("s", &"..") + .finish(), + Scope::TraitRefBoundary { s: _ } => f.debug_struct("TraitRefBoundary").finish(), + Scope::Root => f.debug_struct("Root").finish(), + } + } +} + +type ScopeRef<'a> = &'a Scope<'a>; + +const ROOT_SCOPE: ScopeRef<'static> = &Scope::Root; + +pub(crate) fn provide(providers: &mut ty::query::Providers) { + *providers = ty::query::Providers { + resolve_lifetimes_trait_definition, + resolve_lifetimes, + + named_region_map: |tcx, id| resolve_lifetimes_for(tcx, id).defs.get(&id), + is_late_bound_map, + object_lifetime_default, + late_bound_vars_map: |tcx, id| resolve_lifetimes_for(tcx, id).late_bound_vars.get(&id), + + ..*providers + }; +} + +/// Like `resolve_lifetimes`, but does not resolve lifetimes for trait items. +/// Also does not generate any diagnostics. +/// +/// This is ultimately a subset of the `resolve_lifetimes` work. It effectively +/// resolves lifetimes only within the trait "header" -- that is, the trait +/// and supertrait list. In contrast, `resolve_lifetimes` resolves all the +/// lifetimes within the trait and its items. There is room to refactor this, +/// for example to resolve lifetimes for each trait item in separate queries, +/// but it's convenient to do the entire trait at once because the lifetimes +/// from the trait definition are in scope within the trait items as well. +/// +/// The reason for this separate call is to resolve what would otherwise +/// be a cycle. Consider this example: +/// +/// ```ignore UNSOLVED (maybe @jackh726 knows what lifetime parameter to give Sub) +/// trait Base<'a> { +/// type BaseItem; +/// } +/// trait Sub<'b>: for<'a> Base<'a> { +/// type SubItem: Sub; +/// } +/// ``` +/// +/// When we resolve `Sub` and all its items, we also have to resolve `Sub`. +/// To figure out the index of `'b`, we have to know about the supertraits +/// of `Sub` so that we can determine that the `for<'a>` will be in scope. +/// (This is because we -- currently at least -- flatten all the late-bound +/// lifetimes into a single binder.) This requires us to resolve the +/// *trait definition* of `Sub`; basically just enough lifetime information +/// to look at the supertraits. +#[instrument(level = "debug", skip(tcx))] +fn resolve_lifetimes_trait_definition( + tcx: TyCtxt<'_>, + local_def_id: LocalDefId, +) -> ResolveLifetimes { + convert_named_region_map(do_resolve(tcx, local_def_id, true)) +} + +/// Computes the `ResolveLifetimes` map that contains data for an entire `Item`. +/// You should not read the result of this query directly, but rather use +/// `named_region_map`, `is_late_bound_map`, etc. +#[instrument(level = "debug", skip(tcx))] +fn resolve_lifetimes(tcx: TyCtxt<'_>, local_def_id: LocalDefId) -> ResolveLifetimes { + convert_named_region_map(do_resolve(tcx, local_def_id, false)) +} + +fn do_resolve( + tcx: TyCtxt<'_>, + local_def_id: LocalDefId, + trait_definition_only: bool, +) -> NamedRegionMap { + let item = tcx.hir().expect_item(local_def_id); + let mut named_region_map = + NamedRegionMap { defs: Default::default(), late_bound_vars: Default::default() }; + let mut visitor = LifetimeContext { + tcx, + map: &mut named_region_map, + scope: ROOT_SCOPE, + trait_definition_only, + }; + visitor.visit_item(item); + + named_region_map +} + +fn convert_named_region_map(named_region_map: NamedRegionMap) -> ResolveLifetimes { + let mut rl = ResolveLifetimes::default(); + + for (hir_id, v) in named_region_map.defs { + let map = rl.defs.entry(hir_id.owner).or_default(); + map.insert(hir_id.local_id, v); + } + for (hir_id, v) in named_region_map.late_bound_vars { + let map = rl.late_bound_vars.entry(hir_id.owner).or_default(); + map.insert(hir_id.local_id, v); + } + + debug!(?rl.defs); + debug!(?rl.late_bound_vars); + rl +} + +/// Given `any` owner (structs, traits, trait methods, etc.), does lifetime resolution. +/// There are two important things this does. +/// First, we have to resolve lifetimes for +/// the entire *`Item`* that contains this owner, because that's the largest "scope" +/// where we can have relevant lifetimes. +/// Second, if we are asking for lifetimes in a trait *definition*, we use `resolve_lifetimes_trait_definition` +/// instead of `resolve_lifetimes`, which does not descend into the trait items and does not emit diagnostics. +/// This allows us to avoid cycles. Importantly, if we ask for lifetimes for lifetimes that have an owner +/// other than the trait itself (like the trait methods or associated types), then we just use the regular +/// `resolve_lifetimes`. +fn resolve_lifetimes_for<'tcx>(tcx: TyCtxt<'tcx>, def_id: hir::OwnerId) -> &'tcx ResolveLifetimes { + let item_id = item_for(tcx, def_id.def_id); + let local_def_id = item_id.owner_id.def_id; + if item_id.owner_id == def_id { + let item = tcx.hir().item(item_id); + match item.kind { + hir::ItemKind::Trait(..) => tcx.resolve_lifetimes_trait_definition(local_def_id), + _ => tcx.resolve_lifetimes(local_def_id), + } + } else { + tcx.resolve_lifetimes(local_def_id) + } +} + +/// Finds the `Item` that contains the given `LocalDefId` +fn item_for(tcx: TyCtxt<'_>, local_def_id: LocalDefId) -> hir::ItemId { + match tcx.hir().find_by_def_id(local_def_id) { + Some(Node::Item(item)) => { + return item.item_id(); + } + _ => {} + } + let item = { + let hir_id = tcx.hir().local_def_id_to_hir_id(local_def_id); + let mut parent_iter = tcx.hir().parent_iter(hir_id); + loop { + let node = parent_iter.next().map(|n| n.1); + match node { + Some(hir::Node::Item(item)) => break item.item_id(), + Some(hir::Node::Crate(_)) | None => bug!("Called `item_for` on an Item."), + _ => {} + } + } + }; + item +} + +fn late_region_as_bound_region<'tcx>(tcx: TyCtxt<'tcx>, region: &Region) -> ty::BoundVariableKind { + match region { + Region::LateBound(_, _, def_id) => { + let name = tcx.hir().name(tcx.hir().local_def_id_to_hir_id(def_id.expect_local())); + ty::BoundVariableKind::Region(ty::BrNamed(*def_id, name)) + } + _ => bug!("{:?} is not a late region", region), + } +} + +impl<'a, 'tcx> LifetimeContext<'a, 'tcx> { + /// Returns the binders in scope and the type of `Binder` that should be created for a poly trait ref. + fn poly_trait_ref_binder_info(&mut self) -> (Vec, BinderScopeType) { + let mut scope = self.scope; + let mut supertrait_lifetimes = vec![]; + loop { + match scope { + Scope::Body { .. } | Scope::Root => { + break (vec![], BinderScopeType::Normal); + } + + Scope::Elision { s, .. } | Scope::ObjectLifetimeDefault { s, .. } => { + scope = s; + } + + Scope::Supertrait { s, lifetimes } => { + supertrait_lifetimes = lifetimes.clone(); + scope = s; + } + + Scope::TraitRefBoundary { .. } => { + // We should only see super trait lifetimes if there is a `Binder` above + assert!(supertrait_lifetimes.is_empty()); + break (vec![], BinderScopeType::Normal); + } + + Scope::Binder { hir_id, .. } => { + // Nested poly trait refs have the binders concatenated + let mut full_binders = + self.map.late_bound_vars.entry(*hir_id).or_default().clone(); + full_binders.extend(supertrait_lifetimes.into_iter()); + break (full_binders, BinderScopeType::Concatenating); + } + } + } + } +} +impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> { + type NestedFilter = nested_filter::All; + + fn nested_visit_map(&mut self) -> Self::Map { + self.tcx.hir() + } + + // We want to nest trait/impl items in their parent, but nothing else. + fn visit_nested_item(&mut self, _: hir::ItemId) {} + + fn visit_trait_item_ref(&mut self, ii: &'tcx hir::TraitItemRef) { + if !self.trait_definition_only { + intravisit::walk_trait_item_ref(self, ii) + } + } + + fn visit_nested_body(&mut self, body: hir::BodyId) { + let body = self.tcx.hir().body(body); + self.with(Scope::Body { id: body.id(), s: self.scope }, |this| { + this.visit_body(body); + }); + } + + fn visit_expr(&mut self, e: &'tcx hir::Expr<'tcx>) { + if let hir::ExprKind::Closure(hir::Closure { + binder, bound_generic_params, fn_decl, .. + }) = e.kind + { + if let &hir::ClosureBinder::For { span: for_sp, .. } = binder { + fn span_of_infer(ty: &hir::Ty<'_>) -> Option { + struct V(Option); + + impl<'v> Visitor<'v> for V { + fn visit_ty(&mut self, t: &'v hir::Ty<'v>) { + match t.kind { + _ if self.0.is_some() => (), + hir::TyKind::Infer => { + self.0 = Some(t.span); + } + _ => intravisit::walk_ty(self, t), + } + } + } + + let mut v = V(None); + v.visit_ty(ty); + v.0 + } + + let infer_in_rt_sp = match fn_decl.output { + hir::FnRetTy::DefaultReturn(sp) => Some(sp), + hir::FnRetTy::Return(ty) => span_of_infer(ty), + }; + + let infer_spans = fn_decl + .inputs + .into_iter() + .filter_map(span_of_infer) + .chain(infer_in_rt_sp) + .collect::>(); + + if !infer_spans.is_empty() { + self.tcx.sess + .struct_span_err( + infer_spans, + "implicit types in closure signatures are forbidden when `for<...>` is present", + ) + .span_label(for_sp, "`for<...>` is here") + .emit(); + } + } + + let (lifetimes, binders): (FxIndexMap, Vec<_>) = + bound_generic_params + .iter() + .filter(|param| matches!(param.kind, GenericParamKind::Lifetime { .. })) + .enumerate() + .map(|(late_bound_idx, param)| { + let pair = Region::late(late_bound_idx as u32, self.tcx.hir(), param); + let r = late_region_as_bound_region(self.tcx, &pair.1); + (pair, r) + }) + .unzip(); + + self.record_late_bound_vars(e.hir_id, binders); + let scope = Scope::Binder { + hir_id: e.hir_id, + lifetimes, + s: self.scope, + scope_type: BinderScopeType::Normal, + where_bound_origin: None, + }; + + self.with(scope, |this| { + // a closure has no bounds, so everything + // contained within is scoped within its binder. + intravisit::walk_expr(this, e) + }); + } else { + intravisit::walk_expr(self, e) + } + } + + #[instrument(level = "debug", skip(self))] + fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) { + match &item.kind { + hir::ItemKind::Impl(hir::Impl { of_trait, .. }) => { + if let Some(of_trait) = of_trait { + self.record_late_bound_vars(of_trait.hir_ref_id, Vec::default()); + } + } + _ => {} + } + match item.kind { + hir::ItemKind::Fn(_, ref generics, _) => { + self.visit_early_late(item.hir_id(), generics, |this| { + intravisit::walk_item(this, item); + }); + } + + hir::ItemKind::ExternCrate(_) + | hir::ItemKind::Use(..) + | hir::ItemKind::Macro(..) + | hir::ItemKind::Mod(..) + | hir::ItemKind::ForeignMod { .. } + | hir::ItemKind::GlobalAsm(..) => { + // These sorts of items have no lifetime parameters at all. + intravisit::walk_item(self, item); + } + hir::ItemKind::Static(..) | hir::ItemKind::Const(..) => { + // No lifetime parameters, but implied 'static. + self.with(Scope::Elision { s: self.scope }, |this| { + intravisit::walk_item(this, item) + }); + } + hir::ItemKind::OpaqueTy(hir::OpaqueTy { .. }) => { + // Opaque types are visited when we visit the + // `TyKind::OpaqueDef`, so that they have the lifetimes from + // their parent opaque_ty in scope. + // + // The core idea here is that since OpaqueTys are generated with the impl Trait as + // their owner, we can keep going until we find the Item that owns that. We then + // conservatively add all resolved lifetimes. Otherwise we run into problems in + // cases like `type Foo<'a> = impl Bar`. + for (_hir_id, node) in self.tcx.hir().parent_iter(item.owner_id.into()) { + match node { + hir::Node::Item(parent_item) => { + let resolved_lifetimes: &ResolveLifetimes = self.tcx.resolve_lifetimes( + item_for(self.tcx, parent_item.owner_id.def_id).owner_id.def_id, + ); + // We need to add *all* deps, since opaque tys may want them from *us* + for (&owner, defs) in resolved_lifetimes.defs.iter() { + defs.iter().for_each(|(&local_id, region)| { + self.map.defs.insert(hir::HirId { owner, local_id }, *region); + }); + } + for (&owner, late_bound_vars) in + resolved_lifetimes.late_bound_vars.iter() + { + late_bound_vars.iter().for_each(|(&local_id, late_bound_vars)| { + self.record_late_bound_vars( + hir::HirId { owner, local_id }, + late_bound_vars.clone(), + ); + }); + } + break; + } + hir::Node::Crate(_) => bug!("No Item about an OpaqueTy"), + _ => {} + } + } + } + hir::ItemKind::TyAlias(_, ref generics) + | hir::ItemKind::Enum(_, ref generics) + | hir::ItemKind::Struct(_, ref generics) + | hir::ItemKind::Union(_, ref generics) + | hir::ItemKind::Trait(_, _, ref generics, ..) + | hir::ItemKind::TraitAlias(ref generics, ..) + | hir::ItemKind::Impl(hir::Impl { ref generics, .. }) => { + // These kinds of items have only early-bound lifetime parameters. + let lifetimes = generics + .params + .iter() + .filter_map(|param| match param.kind { + GenericParamKind::Lifetime { .. } => { + Some(Region::early(self.tcx.hir(), param)) + } + GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => None, + }) + .collect(); + self.record_late_bound_vars(item.hir_id(), vec![]); + let scope = Scope::Binder { + hir_id: item.hir_id(), + lifetimes, + scope_type: BinderScopeType::Normal, + s: ROOT_SCOPE, + where_bound_origin: None, + }; + self.with(scope, |this| { + let scope = Scope::TraitRefBoundary { s: this.scope }; + this.with(scope, |this| { + intravisit::walk_item(this, item); + }); + }); + } + } + } + + fn visit_foreign_item(&mut self, item: &'tcx hir::ForeignItem<'tcx>) { + match item.kind { + hir::ForeignItemKind::Fn(_, _, ref generics) => { + self.visit_early_late(item.hir_id(), generics, |this| { + intravisit::walk_foreign_item(this, item); + }) + } + hir::ForeignItemKind::Static(..) => { + intravisit::walk_foreign_item(self, item); + } + hir::ForeignItemKind::Type => { + intravisit::walk_foreign_item(self, item); + } + } + } + + #[instrument(level = "debug", skip(self))] + fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) { + match ty.kind { + hir::TyKind::BareFn(ref c) => { + let (lifetimes, binders): (FxIndexMap, Vec<_>) = c + .generic_params + .iter() + .filter(|param| matches!(param.kind, GenericParamKind::Lifetime { .. })) + .enumerate() + .map(|(late_bound_idx, param)| { + let pair = Region::late(late_bound_idx as u32, self.tcx.hir(), param); + let r = late_region_as_bound_region(self.tcx, &pair.1); + (pair, r) + }) + .unzip(); + self.record_late_bound_vars(ty.hir_id, binders); + let scope = Scope::Binder { + hir_id: ty.hir_id, + lifetimes, + s: self.scope, + scope_type: BinderScopeType::Normal, + where_bound_origin: None, + }; + self.with(scope, |this| { + // a bare fn has no bounds, so everything + // contained within is scoped within its binder. + intravisit::walk_ty(this, ty); + }); + } + hir::TyKind::TraitObject(bounds, ref lifetime, _) => { + debug!(?bounds, ?lifetime, "TraitObject"); + let scope = Scope::TraitRefBoundary { s: self.scope }; + self.with(scope, |this| { + for bound in bounds { + this.visit_poly_trait_ref(bound); + } + }); + match lifetime.name { + LifetimeName::ImplicitObjectLifetimeDefault => { + // If the user does not write *anything*, we + // use the object lifetime defaulting + // rules. So e.g., `Box` becomes + // `Box`. + self.resolve_object_lifetime_default(lifetime) + } + LifetimeName::Infer => { + // If the user writes `'_`, we use the *ordinary* elision + // rules. So the `'_` in e.g., `Box` will be + // resolved the same as the `'_` in `&'_ Foo`. + // + // cc #48468 + } + LifetimeName::Param(..) | LifetimeName::Static => { + // If the user wrote an explicit name, use that. + self.visit_lifetime(lifetime); + } + LifetimeName::Error => {} + } + } + hir::TyKind::Rptr(ref lifetime_ref, ref mt) => { + self.visit_lifetime(lifetime_ref); + let scope = Scope::ObjectLifetimeDefault { + lifetime: self.map.defs.get(&lifetime_ref.hir_id).cloned(), + s: self.scope, + }; + self.with(scope, |this| this.visit_ty(&mt.ty)); + } + hir::TyKind::OpaqueDef(item_id, lifetimes, _in_trait) => { + // Resolve the lifetimes in the bounds to the lifetime defs in the generics. + // `fn foo<'a>() -> impl MyTrait<'a> { ... }` desugars to + // `type MyAnonTy<'b> = impl MyTrait<'b>;` + // ^ ^ this gets resolved in the scope of + // the opaque_ty generics + let opaque_ty = self.tcx.hir().item(item_id); + let (generics, bounds) = match opaque_ty.kind { + hir::ItemKind::OpaqueTy(hir::OpaqueTy { + origin: hir::OpaqueTyOrigin::TyAlias, + .. + }) => { + intravisit::walk_ty(self, ty); + + // Elided lifetimes are not allowed in non-return + // position impl Trait + let scope = Scope::TraitRefBoundary { s: self.scope }; + self.with(scope, |this| { + let scope = Scope::Elision { s: this.scope }; + this.with(scope, |this| { + intravisit::walk_item(this, opaque_ty); + }) + }); + + return; + } + hir::ItemKind::OpaqueTy(hir::OpaqueTy { + origin: hir::OpaqueTyOrigin::FnReturn(..) | hir::OpaqueTyOrigin::AsyncFn(..), + ref generics, + bounds, + .. + }) => (generics, bounds), + ref i => bug!("`impl Trait` pointed to non-opaque type?? {:#?}", i), + }; + + // Resolve the lifetimes that are applied to the opaque type. + // These are resolved in the current scope. + // `fn foo<'a>() -> impl MyTrait<'a> { ... }` desugars to + // `fn foo<'a>() -> MyAnonTy<'a> { ... }` + // ^ ^this gets resolved in the current scope + for lifetime in lifetimes { + let hir::GenericArg::Lifetime(lifetime) = lifetime else { + continue + }; + self.visit_lifetime(lifetime); + + // Check for predicates like `impl for<'a> Trait>` + // and ban them. Type variables instantiated inside binders aren't + // well-supported at the moment, so this doesn't work. + // In the future, this should be fixed and this error should be removed. + let def = self.map.defs.get(&lifetime.hir_id).cloned(); + let Some(Region::LateBound(_, _, def_id)) = def else { + continue + }; + let Some(def_id) = def_id.as_local() else { + continue + }; + let hir_id = self.tcx.hir().local_def_id_to_hir_id(def_id); + // Ensure that the parent of the def is an item, not HRTB + let parent_id = self.tcx.hir().get_parent_node(hir_id); + if !parent_id.is_owner() { + if !self.trait_definition_only { + struct_span_err!( + self.tcx.sess, + lifetime.span, + E0657, + "`impl Trait` can only capture lifetimes \ + bound at the fn or impl level" + ) + .emit(); + } + self.uninsert_lifetime_on_error(lifetime, def.unwrap()); + } + if let hir::Node::Item(hir::Item { + kind: hir::ItemKind::OpaqueTy { .. }, .. + }) = self.tcx.hir().get(parent_id) + { + if !self.trait_definition_only { + let mut err = self.tcx.sess.struct_span_err( + lifetime.span, + "higher kinded lifetime bounds on nested opaque types are not supported yet", + ); + err.span_note(self.tcx.def_span(def_id), "lifetime declared here"); + err.emit(); + } + self.uninsert_lifetime_on_error(lifetime, def.unwrap()); + } + } + + // We want to start our early-bound indices at the end of the parent scope, + // not including any parent `impl Trait`s. + let mut lifetimes = FxIndexMap::default(); + debug!(?generics.params); + for param in generics.params { + match param.kind { + GenericParamKind::Lifetime { .. } => { + let (def_id, reg) = Region::early(self.tcx.hir(), ¶m); + lifetimes.insert(def_id, reg); + } + GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {} + } + } + self.record_late_bound_vars(ty.hir_id, vec![]); + + let scope = Scope::Binder { + hir_id: ty.hir_id, + lifetimes, + s: self.scope, + scope_type: BinderScopeType::Normal, + where_bound_origin: None, + }; + self.with(scope, |this| { + let scope = Scope::TraitRefBoundary { s: this.scope }; + this.with(scope, |this| { + this.visit_generics(generics); + for bound in bounds { + this.visit_param_bound(bound); + } + }) + }); + } + _ => intravisit::walk_ty(self, ty), + } + } + + #[instrument(level = "debug", skip(self))] + fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) { + use self::hir::TraitItemKind::*; + match trait_item.kind { + Fn(_, _) => { + self.visit_early_late(trait_item.hir_id(), &trait_item.generics, |this| { + intravisit::walk_trait_item(this, trait_item) + }); + } + Type(bounds, ref ty) => { + let generics = &trait_item.generics; + let lifetimes = generics + .params + .iter() + .filter_map(|param| match param.kind { + GenericParamKind::Lifetime { .. } => { + Some(Region::early(self.tcx.hir(), param)) + } + GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => None, + }) + .collect(); + self.record_late_bound_vars(trait_item.hir_id(), vec![]); + let scope = Scope::Binder { + hir_id: trait_item.hir_id(), + lifetimes, + s: self.scope, + scope_type: BinderScopeType::Normal, + where_bound_origin: None, + }; + self.with(scope, |this| { + let scope = Scope::TraitRefBoundary { s: this.scope }; + this.with(scope, |this| { + this.visit_generics(generics); + for bound in bounds { + this.visit_param_bound(bound); + } + if let Some(ty) = ty { + this.visit_ty(ty); + } + }) + }); + } + Const(_, _) => { + // Only methods and types support generics. + assert!(trait_item.generics.params.is_empty()); + intravisit::walk_trait_item(self, trait_item); + } + } + } + + #[instrument(level = "debug", skip(self))] + fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) { + use self::hir::ImplItemKind::*; + match impl_item.kind { + Fn(..) => self.visit_early_late(impl_item.hir_id(), &impl_item.generics, |this| { + intravisit::walk_impl_item(this, impl_item) + }), + Type(ref ty) => { + let generics = &impl_item.generics; + let lifetimes: FxIndexMap = generics + .params + .iter() + .filter_map(|param| match param.kind { + GenericParamKind::Lifetime { .. } => { + Some(Region::early(self.tcx.hir(), param)) + } + GenericParamKind::Const { .. } | GenericParamKind::Type { .. } => None, + }) + .collect(); + self.record_late_bound_vars(impl_item.hir_id(), vec![]); + let scope = Scope::Binder { + hir_id: impl_item.hir_id(), + lifetimes, + s: self.scope, + scope_type: BinderScopeType::Normal, + where_bound_origin: None, + }; + self.with(scope, |this| { + let scope = Scope::TraitRefBoundary { s: this.scope }; + this.with(scope, |this| { + this.visit_generics(generics); + this.visit_ty(ty); + }) + }); + } + Const(_, _) => { + // Only methods and types support generics. + assert!(impl_item.generics.params.is_empty()); + intravisit::walk_impl_item(self, impl_item); + } + } + } + + #[instrument(level = "debug", skip(self))] + fn visit_lifetime(&mut self, lifetime_ref: &'tcx hir::Lifetime) { + match lifetime_ref.name { + hir::LifetimeName::Static => self.insert_lifetime(lifetime_ref, Region::Static), + hir::LifetimeName::Param(param_def_id, _) => { + self.resolve_lifetime_ref(param_def_id, lifetime_ref) + } + // If we've already reported an error, just ignore `lifetime_ref`. + hir::LifetimeName::Error => {} + // Those will be resolved by typechecking. + hir::LifetimeName::ImplicitObjectLifetimeDefault | hir::LifetimeName::Infer => {} + } + } + + fn visit_path(&mut self, path: &'tcx hir::Path<'tcx>, _: hir::HirId) { + for (i, segment) in path.segments.iter().enumerate() { + let depth = path.segments.len() - i - 1; + if let Some(ref args) = segment.args { + self.visit_segment_args(path.res, depth, args); + } + } + } + + fn visit_fn( + &mut self, + fk: intravisit::FnKind<'tcx>, + fd: &'tcx hir::FnDecl<'tcx>, + body_id: hir::BodyId, + _: Span, + _: hir::HirId, + ) { + let output = match fd.output { + hir::FnRetTy::DefaultReturn(_) => None, + hir::FnRetTy::Return(ref ty) => Some(&**ty), + }; + self.visit_fn_like_elision(&fd.inputs, output, matches!(fk, intravisit::FnKind::Closure)); + intravisit::walk_fn_kind(self, fk); + self.visit_nested_body(body_id) + } + + fn visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>) { + let scope = Scope::TraitRefBoundary { s: self.scope }; + self.with(scope, |this| { + for param in generics.params { + match param.kind { + GenericParamKind::Lifetime { .. } => {} + GenericParamKind::Type { ref default, .. } => { + if let Some(ref ty) = default { + this.visit_ty(&ty); + } + } + GenericParamKind::Const { ref ty, default } => { + this.visit_ty(&ty); + if let Some(default) = default { + this.visit_body(this.tcx.hir().body(default.body)); + } + } + } + } + for predicate in generics.predicates { + match predicate { + &hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate { + hir_id, + ref bounded_ty, + bounds, + ref bound_generic_params, + origin, + .. + }) => { + let lifetimes: FxIndexMap = + bound_generic_params + .iter() + .filter(|param| { + matches!(param.kind, GenericParamKind::Lifetime { .. }) + }) + .enumerate() + .map(|(late_bound_idx, param)| { + Region::late(late_bound_idx as u32, this.tcx.hir(), param) + }) + .collect(); + let binders: Vec<_> = + lifetimes + .iter() + .map(|(_, region)| { + late_region_as_bound_region(this.tcx, region) + }) + .collect(); + this.record_late_bound_vars(hir_id, binders.clone()); + // Even if there are no lifetimes defined here, we still wrap it in a binder + // scope. If there happens to be a nested poly trait ref (an error), that + // will be `Concatenating` anyways, so we don't have to worry about the depth + // being wrong. + let scope = Scope::Binder { + hir_id, + lifetimes, + s: this.scope, + scope_type: BinderScopeType::Normal, + where_bound_origin: Some(origin), + }; + this.with(scope, |this| { + this.visit_ty(&bounded_ty); + walk_list!(this, visit_param_bound, bounds); + }) + } + &hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate { + ref lifetime, + bounds, + .. + }) => { + this.visit_lifetime(lifetime); + walk_list!(this, visit_param_bound, bounds); + + if lifetime.name != hir::LifetimeName::Static { + for bound in bounds { + let hir::GenericBound::Outlives(ref lt) = bound else { + continue; + }; + if lt.name != hir::LifetimeName::Static { + continue; + } + this.insert_lifetime(lt, Region::Static); + this.tcx + .sess + .struct_span_warn( + lifetime.span, + &format!( + "unnecessary lifetime parameter `{}`", + lifetime.name.ident(), + ), + ) + .help(&format!( + "you can use the `'static` lifetime directly, in place of `{}`", + lifetime.name.ident(), + )) + .emit(); + } + } + } + &hir::WherePredicate::EqPredicate(hir::WhereEqPredicate { + ref lhs_ty, + ref rhs_ty, + .. + }) => { + this.visit_ty(lhs_ty); + this.visit_ty(rhs_ty); + } + } + } + }) + } + + fn visit_param_bound(&mut self, bound: &'tcx hir::GenericBound<'tcx>) { + match bound { + hir::GenericBound::LangItemTrait(_, _, hir_id, _) => { + // FIXME(jackh726): This is pretty weird. `LangItemTrait` doesn't go + // through the regular poly trait ref code, so we don't get another + // chance to introduce a binder. For now, I'm keeping the existing logic + // of "if there isn't a Binder scope above us, add one", but I + // imagine there's a better way to go about this. + let (binders, scope_type) = self.poly_trait_ref_binder_info(); + + self.record_late_bound_vars(*hir_id, binders); + let scope = Scope::Binder { + hir_id: *hir_id, + lifetimes: FxIndexMap::default(), + s: self.scope, + scope_type, + where_bound_origin: None, + }; + self.with(scope, |this| { + intravisit::walk_param_bound(this, bound); + }); + } + _ => intravisit::walk_param_bound(self, bound), + } + } + + fn visit_poly_trait_ref(&mut self, trait_ref: &'tcx hir::PolyTraitRef<'tcx>) { + debug!("visit_poly_trait_ref(trait_ref={:?})", trait_ref); + + let (mut binders, scope_type) = self.poly_trait_ref_binder_info(); + + let initial_bound_vars = binders.len() as u32; + let mut lifetimes: FxIndexMap = FxIndexMap::default(); + let binders_iter = trait_ref + .bound_generic_params + .iter() + .filter(|param| matches!(param.kind, GenericParamKind::Lifetime { .. })) + .enumerate() + .map(|(late_bound_idx, param)| { + let pair = + Region::late(initial_bound_vars + late_bound_idx as u32, self.tcx.hir(), param); + let r = late_region_as_bound_region(self.tcx, &pair.1); + lifetimes.insert(pair.0, pair.1); + r + }); + binders.extend(binders_iter); + + debug!(?binders); + self.record_late_bound_vars(trait_ref.trait_ref.hir_ref_id, binders); + + // Always introduce a scope here, even if this is in a where clause and + // we introduced the binders around the bounded Ty. In that case, we + // just reuse the concatenation functionality also present in nested trait + // refs. + let scope = Scope::Binder { + hir_id: trait_ref.trait_ref.hir_ref_id, + lifetimes, + s: self.scope, + scope_type, + where_bound_origin: None, + }; + self.with(scope, |this| { + walk_list!(this, visit_generic_param, trait_ref.bound_generic_params); + this.visit_trait_ref(&trait_ref.trait_ref); + }); + } +} + +fn object_lifetime_default<'tcx>(tcx: TyCtxt<'tcx>, param_def_id: DefId) -> ObjectLifetimeDefault { + debug_assert_eq!(tcx.def_kind(param_def_id), DefKind::TyParam); + let param_def_id = param_def_id.expect_local(); + let parent_def_id = tcx.local_parent(param_def_id); + let generics = tcx.hir().get_generics(parent_def_id).unwrap(); + let param_hir_id = tcx.local_def_id_to_hir_id(param_def_id); + let param = generics.params.iter().find(|p| p.hir_id == param_hir_id).unwrap(); + + // Scan the bounds and where-clauses on parameters to extract bounds + // of the form `T:'a` so as to determine the `ObjectLifetimeDefault` + // for each type parameter. + match param.kind { + GenericParamKind::Type { .. } => { + let mut set = Set1::Empty; + + // Look for `type: ...` where clauses. + for bound in generics.bounds_for_param(param_def_id) { + // Ignore `for<'a> type: ...` as they can change what + // lifetimes mean (although we could "just" handle it). + if !bound.bound_generic_params.is_empty() { + continue; + } + + for bound in bound.bounds { + if let hir::GenericBound::Outlives(ref lifetime) = *bound { + set.insert(lifetime.name.normalize_to_macros_2_0()); + } + } + } + + match set { + Set1::Empty => ObjectLifetimeDefault::Empty, + Set1::One(hir::LifetimeName::Static) => ObjectLifetimeDefault::Static, + Set1::One(hir::LifetimeName::Param(param_def_id, _)) => { + ObjectLifetimeDefault::Param(param_def_id.to_def_id()) + } + _ => ObjectLifetimeDefault::Ambiguous, + } + } + _ => { + bug!("object_lifetime_default_raw must only be called on a type parameter") + } + } +} + +impl<'a, 'tcx> LifetimeContext<'a, 'tcx> { + fn with(&mut self, wrap_scope: Scope<'_>, f: F) + where + F: for<'b> FnOnce(&mut LifetimeContext<'b, 'tcx>), + { + let LifetimeContext { tcx, map, .. } = self; + let mut this = LifetimeContext { + tcx: *tcx, + map, + scope: &wrap_scope, + trait_definition_only: self.trait_definition_only, + }; + let span = debug_span!("scope", scope = ?TruncatedScopeDebug(&this.scope)); + { + let _enter = span.enter(); + f(&mut this); + } + } + + fn record_late_bound_vars(&mut self, hir_id: hir::HirId, binder: Vec) { + if let Some(old) = self.map.late_bound_vars.insert(hir_id, binder) { + bug!( + "overwrote bound vars for {hir_id:?}:\nold={old:?}\nnew={:?}", + self.map.late_bound_vars[&hir_id] + ) + } + } + + /// Visits self by adding a scope and handling recursive walk over the contents with `walk`. + /// + /// Handles visiting fns and methods. These are a bit complicated because we must distinguish + /// early- vs late-bound lifetime parameters. We do this by checking which lifetimes appear + /// within type bounds; those are early bound lifetimes, and the rest are late bound. + /// + /// For example: + /// + /// fn foo<'a,'b,'c,T:Trait<'b>>(...) + /// + /// Here `'a` and `'c` are late bound but `'b` is early bound. Note that early- and late-bound + /// lifetimes may be interspersed together. + /// + /// If early bound lifetimes are present, we separate them into their own list (and likewise + /// for late bound). They will be numbered sequentially, starting from the lowest index that is + /// already in scope (for a fn item, that will be 0, but for a method it might not be). Late + /// bound lifetimes are resolved by name and associated with a binder ID (`binder_id`), so the + /// ordering is not important there. + fn visit_early_late( + &mut self, + hir_id: hir::HirId, + generics: &'tcx hir::Generics<'tcx>, + walk: F, + ) where + F: for<'b, 'c> FnOnce(&'b mut LifetimeContext<'c, 'tcx>), + { + let mut named_late_bound_vars = 0; + let lifetimes: FxIndexMap = generics + .params + .iter() + .filter_map(|param| match param.kind { + GenericParamKind::Lifetime { .. } => { + if self.tcx.is_late_bound(param.hir_id) { + let late_bound_idx = named_late_bound_vars; + named_late_bound_vars += 1; + Some(Region::late(late_bound_idx, self.tcx.hir(), param)) + } else { + Some(Region::early(self.tcx.hir(), param)) + } + } + GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => None, + }) + .collect(); + + let binders: Vec<_> = generics + .params + .iter() + .filter(|param| { + matches!(param.kind, GenericParamKind::Lifetime { .. }) + && self.tcx.is_late_bound(param.hir_id) + }) + .enumerate() + .map(|(late_bound_idx, param)| { + let pair = Region::late(late_bound_idx as u32, self.tcx.hir(), param); + late_region_as_bound_region(self.tcx, &pair.1) + }) + .collect(); + self.record_late_bound_vars(hir_id, binders); + let scope = Scope::Binder { + hir_id, + lifetimes, + s: self.scope, + scope_type: BinderScopeType::Normal, + where_bound_origin: None, + }; + self.with(scope, walk); + } + + #[instrument(level = "debug", skip(self))] + fn resolve_lifetime_ref( + &mut self, + region_def_id: LocalDefId, + lifetime_ref: &'tcx hir::Lifetime, + ) { + // Walk up the scope chain, tracking the number of fn scopes + // that we pass through, until we find a lifetime with the + // given name or we run out of scopes. + // search. + let mut late_depth = 0; + let mut scope = self.scope; + let mut outermost_body = None; + let result = loop { + match *scope { + Scope::Body { id, s } => { + outermost_body = Some(id); + scope = s; + } + + Scope::Root => { + break None; + } + + Scope::Binder { ref lifetimes, scope_type, s, where_bound_origin, .. } => { + if let Some(&def) = lifetimes.get(®ion_def_id) { + break Some(def.shifted(late_depth)); + } + match scope_type { + BinderScopeType::Normal => late_depth += 1, + BinderScopeType::Concatenating => {} + } + // Fresh lifetimes in APIT used to be allowed in async fns and forbidden in + // regular fns. + if let Some(hir::PredicateOrigin::ImplTrait) = where_bound_origin + && let hir::LifetimeName::Param(_, hir::ParamName::Fresh) = lifetime_ref.name + && let hir::IsAsync::NotAsync = self.tcx.asyncness(lifetime_ref.hir_id.owner.def_id) + && !self.tcx.features().anonymous_lifetime_in_impl_trait + { + let mut diag = rustc_session::parse::feature_err( + &self.tcx.sess.parse_sess, + sym::anonymous_lifetime_in_impl_trait, + lifetime_ref.span, + "anonymous lifetimes in `impl Trait` are unstable", + ); + + match self.tcx.hir().get_generics(lifetime_ref.hir_id.owner.def_id) { + Some(generics) => { + + let new_param_sugg_tuple; + + new_param_sugg_tuple = match generics.span_for_param_suggestion() { + Some(_) => { + Some((self.tcx.sess.source_map().span_through_char(generics.span, '<').shrink_to_hi(), "'a, ".to_owned())) + }, + None => Some((generics.span, "<'a>".to_owned())) + }; + + let mut multi_sugg_vec = vec![(lifetime_ref.span.shrink_to_hi(), "'a ".to_owned())]; + + if let Some(new_tuple) = new_param_sugg_tuple{ + multi_sugg_vec.push(new_tuple); + } + + diag.span_label(lifetime_ref.span, "expected named lifetime parameter"); + diag.multipart_suggestion("consider introducing a named lifetime parameter", + multi_sugg_vec, + rustc_errors::Applicability::MaybeIncorrect); + + }, + None => { } + } + + diag.emit(); + return; + } + scope = s; + } + + Scope::Elision { s, .. } + | Scope::ObjectLifetimeDefault { s, .. } + | Scope::Supertrait { s, .. } + | Scope::TraitRefBoundary { s, .. } => { + scope = s; + } + } + }; + + if let Some(mut def) = result { + if let Region::EarlyBound(..) = def { + // Do not free early-bound regions, only late-bound ones. + } else if let Some(body_id) = outermost_body { + let fn_id = self.tcx.hir().body_owner(body_id); + match self.tcx.hir().get(fn_id) { + Node::Item(&hir::Item { kind: hir::ItemKind::Fn(..), .. }) + | Node::TraitItem(&hir::TraitItem { + kind: hir::TraitItemKind::Fn(..), .. + }) + | Node::ImplItem(&hir::ImplItem { kind: hir::ImplItemKind::Fn(..), .. }) => { + let scope = self.tcx.hir().local_def_id(fn_id); + def = Region::Free(scope.to_def_id(), def.id().unwrap()); + } + _ => {} + } + } + + self.insert_lifetime(lifetime_ref, def); + return; + } + + // We may fail to resolve higher-ranked lifetimes that are mentioned by APIT. + // AST-based resolution does not care for impl-trait desugaring, which are the + // responibility of lowering. This may create a mismatch between the resolution + // AST found (`region_def_id`) which points to HRTB, and what HIR allows. + // ``` + // fn foo(x: impl for<'a> Trait<'a, Assoc = impl Copy + 'a>) {} + // ``` + // + // In such case, walk back the binders to diagnose it properly. + let mut scope = self.scope; + loop { + match *scope { + Scope::Binder { + where_bound_origin: Some(hir::PredicateOrigin::ImplTrait), .. + } => { + let mut err = self.tcx.sess.struct_span_err( + lifetime_ref.span, + "`impl Trait` can only mention lifetimes bound at the fn or impl level", + ); + err.span_note(self.tcx.def_span(region_def_id), "lifetime declared here"); + err.emit(); + return; + } + Scope::Root => break, + Scope::Binder { s, .. } + | Scope::Body { s, .. } + | Scope::Elision { s, .. } + | Scope::ObjectLifetimeDefault { s, .. } + | Scope::Supertrait { s, .. } + | Scope::TraitRefBoundary { s, .. } => { + scope = s; + } + } + } + + self.tcx.sess.delay_span_bug( + lifetime_ref.span, + &format!("Could not resolve {:?} in scope {:#?}", lifetime_ref, self.scope,), + ); + } + + #[instrument(level = "debug", skip(self))] + fn visit_segment_args( + &mut self, + res: Res, + depth: usize, + generic_args: &'tcx hir::GenericArgs<'tcx>, + ) { + if generic_args.parenthesized { + self.visit_fn_like_elision( + generic_args.inputs(), + Some(generic_args.bindings[0].ty()), + false, + ); + return; + } + + for arg in generic_args.args { + if let hir::GenericArg::Lifetime(lt) = arg { + self.visit_lifetime(lt); + } + } + + // Figure out if this is a type/trait segment, + // which requires object lifetime defaults. + let type_def_id = match res { + Res::Def(DefKind::AssocTy, def_id) if depth == 1 => Some(self.tcx.parent(def_id)), + Res::Def(DefKind::Variant, def_id) if depth == 0 => Some(self.tcx.parent(def_id)), + Res::Def( + DefKind::Struct + | DefKind::Union + | DefKind::Enum + | DefKind::TyAlias + | DefKind::Trait, + def_id, + ) if depth == 0 => Some(def_id), + _ => None, + }; + + debug!(?type_def_id); + + // Compute a vector of defaults, one for each type parameter, + // per the rules given in RFCs 599 and 1156. Example: + // + // ```rust + // struct Foo<'a, T: 'a, U> { } + // ``` + // + // If you have `Foo<'x, dyn Bar, dyn Baz>`, we want to default + // `dyn Bar` to `dyn Bar + 'x` (because of the `T: 'a` bound) + // and `dyn Baz` to `dyn Baz + 'static` (because there is no + // such bound). + // + // Therefore, we would compute `object_lifetime_defaults` to a + // vector like `['x, 'static]`. Note that the vector only + // includes type parameters. + let object_lifetime_defaults = type_def_id.map_or_else(Vec::new, |def_id| { + let in_body = { + let mut scope = self.scope; + loop { + match *scope { + Scope::Root => break false, + + Scope::Body { .. } => break true, + + Scope::Binder { s, .. } + | Scope::Elision { s, .. } + | Scope::ObjectLifetimeDefault { s, .. } + | Scope::Supertrait { s, .. } + | Scope::TraitRefBoundary { s, .. } => { + scope = s; + } + } + } + }; + + let map = &self.map; + let generics = self.tcx.generics_of(def_id); + + // `type_def_id` points to an item, so there is nothing to inherit generics from. + debug_assert_eq!(generics.parent_count, 0); + + let set_to_region = |set: ObjectLifetimeDefault| match set { + ObjectLifetimeDefault::Empty => { + if in_body { + None + } else { + Some(Region::Static) + } + } + ObjectLifetimeDefault::Static => Some(Region::Static), + ObjectLifetimeDefault::Param(param_def_id) => { + // This index can be used with `generic_args` since `parent_count == 0`. + let index = generics.param_def_id_to_index[¶m_def_id] as usize; + generic_args.args.get(index).and_then(|arg| match arg { + GenericArg::Lifetime(lt) => map.defs.get(<.hir_id).copied(), + _ => None, + }) + } + ObjectLifetimeDefault::Ambiguous => None, + }; + generics + .params + .iter() + .filter_map(|param| { + match self.tcx.def_kind(param.def_id) { + // Generic consts don't impose any constraints. + // + // We still store a dummy value here to allow generic parameters + // in an arbitrary order. + DefKind::ConstParam => Some(ObjectLifetimeDefault::Empty), + DefKind::TyParam => Some(self.tcx.object_lifetime_default(param.def_id)), + // We may also get a `Trait` or `TraitAlias` because of how generics `Self` parameter + // works. Ignore it because it can't have a meaningful lifetime default. + DefKind::LifetimeParam | DefKind::Trait | DefKind::TraitAlias => None, + dk => bug!("unexpected def_kind {:?}", dk), + } + }) + .map(set_to_region) + .collect() + }); + + debug!(?object_lifetime_defaults); + + let mut i = 0; + for arg in generic_args.args { + match arg { + GenericArg::Lifetime(_) => {} + GenericArg::Type(ty) => { + if let Some(<) = object_lifetime_defaults.get(i) { + let scope = Scope::ObjectLifetimeDefault { lifetime: lt, s: self.scope }; + self.with(scope, |this| this.visit_ty(ty)); + } else { + self.visit_ty(ty); + } + i += 1; + } + GenericArg::Const(ct) => { + self.visit_anon_const(&ct.value); + i += 1; + } + GenericArg::Infer(inf) => { + self.visit_id(inf.hir_id); + i += 1; + } + } + } + + // Hack: when resolving the type `XX` in binding like `dyn + // Foo<'b, Item = XX>`, the current object-lifetime default + // would be to examine the trait `Foo` to check whether it has + // a lifetime bound declared on `Item`. e.g., if `Foo` is + // declared like so, then the default object lifetime bound in + // `XX` should be `'b`: + // + // ```rust + // trait Foo<'a> { + // type Item: 'a; + // } + // ``` + // + // but if we just have `type Item;`, then it would be + // `'static`. However, we don't get all of this logic correct. + // + // Instead, we do something hacky: if there are no lifetime parameters + // to the trait, then we simply use a default object lifetime + // bound of `'static`, because there is no other possibility. On the other hand, + // if there ARE lifetime parameters, then we require the user to give an + // explicit bound for now. + // + // This is intended to leave room for us to implement the + // correct behavior in the future. + let has_lifetime_parameter = + generic_args.args.iter().any(|arg| matches!(arg, GenericArg::Lifetime(_))); + + // Resolve lifetimes found in the bindings, so either in the type `XX` in `Item = XX` or + // in the trait ref `YY<...>` in `Item: YY<...>`. + for binding in generic_args.bindings { + let scope = Scope::ObjectLifetimeDefault { + lifetime: if has_lifetime_parameter { None } else { Some(Region::Static) }, + s: self.scope, + }; + if let Some(type_def_id) = type_def_id { + let lifetimes = LifetimeContext::supertrait_hrtb_lifetimes( + self.tcx, + type_def_id, + binding.ident, + ); + self.with(scope, |this| { + let scope = Scope::Supertrait { + lifetimes: lifetimes.unwrap_or_default(), + s: this.scope, + }; + this.with(scope, |this| this.visit_assoc_type_binding(binding)); + }); + } else { + self.with(scope, |this| this.visit_assoc_type_binding(binding)); + } + } + } + + /// Returns all the late-bound vars that come into scope from supertrait HRTBs, based on the + /// associated type name and starting trait. + /// For example, imagine we have + /// ```ignore (illustrative) + /// trait Foo<'a, 'b> { + /// type As; + /// } + /// trait Bar<'b>: for<'a> Foo<'a, 'b> {} + /// trait Bar: for<'b> Bar<'b> {} + /// ``` + /// In this case, if we wanted to the supertrait HRTB lifetimes for `As` on + /// the starting trait `Bar`, we would return `Some(['b, 'a])`. + fn supertrait_hrtb_lifetimes( + tcx: TyCtxt<'tcx>, + def_id: DefId, + assoc_name: Ident, + ) -> Option> { + let trait_defines_associated_type_named = |trait_def_id: DefId| { + tcx.associated_items(trait_def_id) + .find_by_name_and_kind(tcx, assoc_name, ty::AssocKind::Type, trait_def_id) + .is_some() + }; + + use smallvec::{smallvec, SmallVec}; + let mut stack: SmallVec<[(DefId, SmallVec<[ty::BoundVariableKind; 8]>); 8]> = + smallvec![(def_id, smallvec![])]; + let mut visited: FxHashSet = FxHashSet::default(); + loop { + let Some((def_id, bound_vars)) = stack.pop() else { + break None; + }; + // See issue #83753. If someone writes an associated type on a non-trait, just treat it as + // there being no supertrait HRTBs. + match tcx.def_kind(def_id) { + DefKind::Trait | DefKind::TraitAlias | DefKind::Impl => {} + _ => break None, + } + + if trait_defines_associated_type_named(def_id) { + break Some(bound_vars.into_iter().collect()); + } + let predicates = + tcx.super_predicates_that_define_assoc_type((def_id, Some(assoc_name))); + let obligations = predicates.predicates.iter().filter_map(|&(pred, _)| { + let bound_predicate = pred.kind(); + match bound_predicate.skip_binder() { + ty::PredicateKind::Trait(data) => { + // The order here needs to match what we would get from `subst_supertrait` + let pred_bound_vars = bound_predicate.bound_vars(); + let mut all_bound_vars = bound_vars.clone(); + all_bound_vars.extend(pred_bound_vars.iter()); + let super_def_id = data.trait_ref.def_id; + Some((super_def_id, all_bound_vars)) + } + _ => None, + } + }); + + let obligations = obligations.filter(|o| visited.insert(o.0)); + stack.extend(obligations); + } + } + + #[instrument(level = "debug", skip(self))] + fn visit_fn_like_elision( + &mut self, + inputs: &'tcx [hir::Ty<'tcx>], + output: Option<&'tcx hir::Ty<'tcx>>, + in_closure: bool, + ) { + self.with(Scope::Elision { s: self.scope }, |this| { + for input in inputs { + this.visit_ty(input); + } + if !in_closure && let Some(output) = output { + this.visit_ty(output); + } + }); + if in_closure && let Some(output) = output { + self.visit_ty(output); + } + } + + fn resolve_object_lifetime_default(&mut self, lifetime_ref: &'tcx hir::Lifetime) { + debug!("resolve_object_lifetime_default(lifetime_ref={:?})", lifetime_ref); + let mut late_depth = 0; + let mut scope = self.scope; + let lifetime = loop { + match *scope { + Scope::Binder { s, scope_type, .. } => { + match scope_type { + BinderScopeType::Normal => late_depth += 1, + BinderScopeType::Concatenating => {} + } + scope = s; + } + + Scope::Root | Scope::Elision { .. } => break Region::Static, + + Scope::Body { .. } | Scope::ObjectLifetimeDefault { lifetime: None, .. } => return, + + Scope::ObjectLifetimeDefault { lifetime: Some(l), .. } => break l, + + Scope::Supertrait { s, .. } | Scope::TraitRefBoundary { s, .. } => { + scope = s; + } + } + }; + self.insert_lifetime(lifetime_ref, lifetime.shifted(late_depth)); + } + + #[instrument(level = "debug", skip(self))] + fn insert_lifetime(&mut self, lifetime_ref: &'tcx hir::Lifetime, def: Region) { + debug!( + node = ?self.tcx.hir().node_to_string(lifetime_ref.hir_id), + span = ?self.tcx.sess.source_map().span_to_diagnostic_string(lifetime_ref.span) + ); + self.map.defs.insert(lifetime_ref.hir_id, def); + } + + /// Sometimes we resolve a lifetime, but later find that it is an + /// error (esp. around impl trait). In that case, we remove the + /// entry into `map.defs` so as not to confuse later code. + fn uninsert_lifetime_on_error(&mut self, lifetime_ref: &'tcx hir::Lifetime, bad_def: Region) { + let old_value = self.map.defs.remove(&lifetime_ref.hir_id); + assert_eq!(old_value, Some(bad_def)); + } +} + +/// Detects late-bound lifetimes and inserts them into +/// `late_bound`. +/// +/// A region declared on a fn is **late-bound** if: +/// - it is constrained by an argument type; +/// - it does not appear in a where-clause. +/// +/// "Constrained" basically means that it appears in any type but +/// not amongst the inputs to a projection. In other words, `<&'a +/// T as Trait<''b>>::Foo` does not constrain `'a` or `'b`. +fn is_late_bound_map(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option<&FxIndexSet> { + let hir_id = tcx.hir().local_def_id_to_hir_id(def_id); + let decl = tcx.hir().fn_decl_by_hir_id(hir_id)?; + let generics = tcx.hir().get_generics(def_id)?; + + let mut late_bound = FxIndexSet::default(); + + let mut constrained_by_input = ConstrainedCollector::default(); + for arg_ty in decl.inputs { + constrained_by_input.visit_ty(arg_ty); + } + + let mut appears_in_output = AllCollector::default(); + intravisit::walk_fn_ret_ty(&mut appears_in_output, &decl.output); + + debug!(?constrained_by_input.regions); + + // Walk the lifetimes that appear in where clauses. + // + // Subtle point: because we disallow nested bindings, we can just + // ignore binders here and scrape up all names we see. + let mut appears_in_where_clause = AllCollector::default(); + appears_in_where_clause.visit_generics(generics); + debug!(?appears_in_where_clause.regions); + + // Late bound regions are those that: + // - appear in the inputs + // - do not appear in the where-clauses + // - are not implicitly captured by `impl Trait` + for param in generics.params { + match param.kind { + hir::GenericParamKind::Lifetime { .. } => { /* fall through */ } + + // Neither types nor consts are late-bound. + hir::GenericParamKind::Type { .. } | hir::GenericParamKind::Const { .. } => continue, + } + + let param_def_id = tcx.hir().local_def_id(param.hir_id); + + // appears in the where clauses? early-bound. + if appears_in_where_clause.regions.contains(¶m_def_id) { + continue; + } + + // does not appear in the inputs, but appears in the return type? early-bound. + if !constrained_by_input.regions.contains(¶m_def_id) + && appears_in_output.regions.contains(¶m_def_id) + { + continue; + } + + debug!("lifetime {:?} with id {:?} is late-bound", param.name.ident(), param.hir_id); + + let inserted = late_bound.insert(param_def_id); + assert!(inserted, "visited lifetime {:?} twice", param.hir_id); + } + + debug!(?late_bound); + return Some(tcx.arena.alloc(late_bound)); + + #[derive(Default)] + struct ConstrainedCollector { + regions: FxHashSet, + } + + impl<'v> Visitor<'v> for ConstrainedCollector { + fn visit_ty(&mut self, ty: &'v hir::Ty<'v>) { + match ty.kind { + hir::TyKind::Path( + hir::QPath::Resolved(Some(_), _) | hir::QPath::TypeRelative(..), + ) => { + // ignore lifetimes appearing in associated type + // projections, as they are not *constrained* + // (defined above) + } + + hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => { + // consider only the lifetimes on the final + // segment; I am not sure it's even currently + // valid to have them elsewhere, but even if it + // is, those would be potentially inputs to + // projections + if let Some(last_segment) = path.segments.last() { + self.visit_path_segment(last_segment); + } + } + + _ => { + intravisit::walk_ty(self, ty); + } + } + } + + fn visit_lifetime(&mut self, lifetime_ref: &'v hir::Lifetime) { + if let hir::LifetimeName::Param(def_id, _) = lifetime_ref.name { + self.regions.insert(def_id); + } + } + } + + #[derive(Default)] + struct AllCollector { + regions: FxHashSet, + } + + impl<'v> Visitor<'v> for AllCollector { + fn visit_lifetime(&mut self, lifetime_ref: &'v hir::Lifetime) { + if let hir::LifetimeName::Param(def_id, _) = lifetime_ref.name { + self.regions.insert(def_id); + } + } + } +} diff --git a/compiler/rustc_hir_analysis/src/collect/predicates_of.rs b/compiler/rustc_hir_analysis/src/collect/predicates_of.rs new file mode 100644 index 000000000..2e84e1d01 --- /dev/null +++ b/compiler/rustc_hir_analysis/src/collect/predicates_of.rs @@ -0,0 +1,707 @@ +use crate::astconv::AstConv; +use crate::bounds::Bounds; +use crate::collect::ItemCtxt; +use crate::constrained_generic_params as cgp; +use hir::{HirId, Node}; +use rustc_data_structures::fx::FxIndexSet; +use rustc_hir as hir; +use rustc_hir::def::DefKind; +use rustc_hir::def_id::{DefId, LocalDefId}; +use rustc_hir::intravisit::{self, Visitor}; +use rustc_middle::ty::subst::InternalSubsts; +use rustc_middle::ty::ToPredicate; +use rustc_middle::ty::{self, Ty, TyCtxt}; +use rustc_span::symbol::{sym, Ident}; +use rustc_span::{Span, DUMMY_SP}; + +#[derive(Debug)] +struct OnlySelfBounds(bool); + +/// Returns a list of all type predicates (explicit and implicit) for the definition with +/// ID `def_id`. This includes all predicates returned by `predicates_defined_on`, plus +/// `Self: Trait` predicates for traits. +pub(super) fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> { + let mut result = tcx.predicates_defined_on(def_id); + + if tcx.is_trait(def_id) { + // For traits, add `Self: Trait` predicate. This is + // not part of the predicates that a user writes, but it + // is something that one must prove in order to invoke a + // method or project an associated type. + // + // In the chalk setup, this predicate is not part of the + // "predicates" for a trait item. But it is useful in + // rustc because if you directly (e.g.) invoke a trait + // method like `Trait::method(...)`, you must naturally + // prove that the trait applies to the types that were + // used, and adding the predicate into this list ensures + // that this is done. + // + // We use a DUMMY_SP here as a way to signal trait bounds that come + // from the trait itself that *shouldn't* be shown as the source of + // an obligation and instead be skipped. Otherwise we'd use + // `tcx.def_span(def_id);` + + let constness = if tcx.has_attr(def_id, sym::const_trait) { + ty::BoundConstness::ConstIfConst + } else { + ty::BoundConstness::NotConst + }; + + let span = rustc_span::DUMMY_SP; + result.predicates = + tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(std::iter::once(( + ty::TraitRef::identity(tcx, def_id).with_constness(constness).to_predicate(tcx), + span, + )))); + } + debug!("predicates_of(def_id={:?}) = {:?}", def_id, result); + result +} + +/// Returns a list of user-specified type predicates for the definition with ID `def_id`. +/// N.B., this does not include any implied/inferred constraints. +#[instrument(level = "trace", skip(tcx), ret)] +fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredicates<'_> { + use rustc_hir::*; + + let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local()); + let node = tcx.hir().get(hir_id); + + let mut is_trait = None; + let mut is_default_impl_trait = None; + + let icx = ItemCtxt::new(tcx, def_id); + + const NO_GENERICS: &hir::Generics<'_> = hir::Generics::empty(); + + // We use an `IndexSet` to preserves order of insertion. + // Preserving the order of insertion is important here so as not to break UI tests. + let mut predicates: FxIndexSet<(ty::Predicate<'_>, Span)> = FxIndexSet::default(); + + let ast_generics = match node { + Node::TraitItem(item) => item.generics, + + Node::ImplItem(item) => item.generics, + + Node::Item(item) => { + match item.kind { + ItemKind::Impl(ref impl_) => { + if impl_.defaultness.is_default() { + is_default_impl_trait = tcx.impl_trait_ref(def_id).map(ty::Binder::dummy); + } + &impl_.generics + } + ItemKind::Fn(.., ref generics, _) + | ItemKind::TyAlias(_, ref generics) + | ItemKind::Enum(_, ref generics) + | ItemKind::Struct(_, ref generics) + | ItemKind::Union(_, ref generics) => *generics, + + ItemKind::Trait(_, _, ref generics, ..) => { + is_trait = Some(ty::TraitRef::identity(tcx, def_id)); + *generics + } + ItemKind::TraitAlias(ref generics, _) => { + is_trait = Some(ty::TraitRef::identity(tcx, def_id)); + *generics + } + ItemKind::OpaqueTy(OpaqueTy { + origin: hir::OpaqueTyOrigin::AsyncFn(..) | hir::OpaqueTyOrigin::FnReturn(..), + .. + }) => { + // return-position impl trait + // + // We don't inherit predicates from the parent here: + // If we have, say `fn f<'a, T: 'a>() -> impl Sized {}` + // then the return type is `f::<'static, T>::{{opaque}}`. + // + // If we inherited the predicates of `f` then we would + // require that `T: 'static` to show that the return + // type is well-formed. + // + // The only way to have something with this opaque type + // is from the return type of the containing function, + // which will ensure that the function's predicates + // hold. + return ty::GenericPredicates { parent: None, predicates: &[] }; + } + ItemKind::OpaqueTy(OpaqueTy { + ref generics, + origin: hir::OpaqueTyOrigin::TyAlias, + .. + }) => { + // type-alias impl trait + generics + } + + _ => NO_GENERICS, + } + } + + Node::ForeignItem(item) => match item.kind { + ForeignItemKind::Static(..) => NO_GENERICS, + ForeignItemKind::Fn(_, _, ref generics) => *generics, + ForeignItemKind::Type => NO_GENERICS, + }, + + _ => NO_GENERICS, + }; + + let generics = tcx.generics_of(def_id); + let parent_count = generics.parent_count as u32; + let has_own_self = generics.has_self && parent_count == 0; + + // Below we'll consider the bounds on the type parameters (including `Self`) + // and the explicit where-clauses, but to get the full set of predicates + // on a trait we need to add in the supertrait bounds and bounds found on + // associated types. + if let Some(_trait_ref) = is_trait { + predicates.extend(tcx.super_predicates_of(def_id).predicates.iter().cloned()); + } + + // In default impls, we can assume that the self type implements + // the trait. So in: + // + // default impl Foo for Bar { .. } + // + // we add a default where clause `Foo: Bar`. We do a similar thing for traits + // (see below). Recall that a default impl is not itself an impl, but rather a + // set of defaults that can be incorporated into another impl. + if let Some(trait_ref) = is_default_impl_trait { + predicates.insert((trait_ref.without_const().to_predicate(tcx), tcx.def_span(def_id))); + } + + // Collect the region predicates that were declared inline as + // well. In the case of parameters declared on a fn or method, we + // have to be careful to only iterate over early-bound regions. + let mut index = parent_count + + has_own_self as u32 + + super::early_bound_lifetimes_from_generics(tcx, ast_generics).count() as u32; + + trace!(?predicates); + trace!(?ast_generics); + + // Collect the predicates that were written inline by the user on each + // type parameter (e.g., ``). + for param in ast_generics.params { + match param.kind { + // We already dealt with early bound lifetimes above. + GenericParamKind::Lifetime { .. } => (), + GenericParamKind::Type { .. } => { + let name = param.name.ident().name; + let param_ty = ty::ParamTy::new(index, name).to_ty(tcx); + index += 1; + + let mut bounds = Bounds::default(); + // Params are implicitly sized unless a `?Sized` bound is found + >::add_implicitly_sized( + &icx, + &mut bounds, + &[], + Some((param.hir_id, ast_generics.predicates)), + param.span, + ); + trace!(?bounds); + predicates.extend(bounds.predicates(tcx, param_ty)); + trace!(?predicates); + } + GenericParamKind::Const { .. } => { + // Bounds on const parameters are currently not possible. + index += 1; + } + } + } + + trace!(?predicates); + // Add in the bounds that appear in the where-clause. + for predicate in ast_generics.predicates { + match predicate { + hir::WherePredicate::BoundPredicate(bound_pred) => { + let ty = icx.to_ty(bound_pred.bounded_ty); + let bound_vars = icx.tcx.late_bound_vars(bound_pred.hir_id); + + // Keep the type around in a dummy predicate, in case of no bounds. + // That way, `where Ty:` is not a complete noop (see #53696) and `Ty` + // is still checked for WF. + if bound_pred.bounds.is_empty() { + if let ty::Param(_) = ty.kind() { + // This is a `where T:`, which can be in the HIR from the + // transformation that moves `?Sized` to `T`'s declaration. + // We can skip the predicate because type parameters are + // trivially WF, but also we *should*, to avoid exposing + // users who never wrote `where Type:,` themselves, to + // compiler/tooling bugs from not handling WF predicates. + } else { + let span = bound_pred.bounded_ty.span; + let predicate = ty::Binder::bind_with_vars( + ty::PredicateKind::WellFormed(ty.into()), + bound_vars, + ); + predicates.insert((predicate.to_predicate(tcx), span)); + } + } + + let mut bounds = Bounds::default(); + >::add_bounds( + &icx, + ty, + bound_pred.bounds.iter(), + &mut bounds, + bound_vars, + ); + predicates.extend(bounds.predicates(tcx, ty)); + } + + hir::WherePredicate::RegionPredicate(region_pred) => { + let r1 = >::ast_region_to_region(&icx, ®ion_pred.lifetime, None); + predicates.extend(region_pred.bounds.iter().map(|bound| { + let (r2, span) = match bound { + hir::GenericBound::Outlives(lt) => { + (>::ast_region_to_region(&icx, lt, None), lt.span) + } + _ => bug!(), + }; + let pred = ty::Binder::dummy(ty::PredicateKind::RegionOutlives( + ty::OutlivesPredicate(r1, r2), + )) + .to_predicate(icx.tcx); + + (pred, span) + })) + } + + hir::WherePredicate::EqPredicate(..) => { + // FIXME(#20041) + } + } + } + + if tcx.features().generic_const_exprs { + predicates.extend(const_evaluatable_predicates_of(tcx, def_id.expect_local())); + } + + let mut predicates: Vec<_> = predicates.into_iter().collect(); + + // Subtle: before we store the predicates into the tcx, we + // sort them so that predicates like `T: Foo` come + // before uses of `U`. This avoids false ambiguity errors + // in trait checking. See `setup_constraining_predicates` + // for details. + if let Node::Item(&Item { kind: ItemKind::Impl { .. }, .. }) = node { + let self_ty = tcx.type_of(def_id); + let trait_ref = tcx.impl_trait_ref(def_id); + cgp::setup_constraining_predicates( + tcx, + &mut predicates, + trait_ref, + &mut cgp::parameters_for_impl(self_ty, trait_ref), + ); + } + + ty::GenericPredicates { + parent: generics.parent, + predicates: tcx.arena.alloc_from_iter(predicates), + } +} + +fn const_evaluatable_predicates_of<'tcx>( + tcx: TyCtxt<'tcx>, + def_id: LocalDefId, +) -> FxIndexSet<(ty::Predicate<'tcx>, Span)> { + struct ConstCollector<'tcx> { + tcx: TyCtxt<'tcx>, + preds: FxIndexSet<(ty::Predicate<'tcx>, Span)>, + } + + impl<'tcx> intravisit::Visitor<'tcx> for ConstCollector<'tcx> { + fn visit_anon_const(&mut self, c: &'tcx hir::AnonConst) { + let def_id = self.tcx.hir().local_def_id(c.hir_id); + let ct = ty::Const::from_anon_const(self.tcx, def_id); + if let ty::ConstKind::Unevaluated(_) = ct.kind() { + let span = self.tcx.hir().span(c.hir_id); + self.preds.insert(( + ty::Binder::dummy(ty::PredicateKind::ConstEvaluatable(ct)) + .to_predicate(self.tcx), + span, + )); + } + } + + fn visit_const_param_default(&mut self, _param: HirId, _ct: &'tcx hir::AnonConst) { + // Do not look into const param defaults, + // these get checked when they are actually instantiated. + // + // We do not want the following to error: + // + // struct Foo; + // struct Bar(Foo); + } + } + + let hir_id = tcx.hir().local_def_id_to_hir_id(def_id); + let node = tcx.hir().get(hir_id); + + let mut collector = ConstCollector { tcx, preds: FxIndexSet::default() }; + if let hir::Node::Item(item) = node && let hir::ItemKind::Impl(ref impl_) = item.kind { + if let Some(of_trait) = &impl_.of_trait { + debug!("const_evaluatable_predicates_of({:?}): visit impl trait_ref", def_id); + collector.visit_trait_ref(of_trait); + } + + debug!("const_evaluatable_predicates_of({:?}): visit_self_ty", def_id); + collector.visit_ty(impl_.self_ty); + } + + if let Some(generics) = node.generics() { + debug!("const_evaluatable_predicates_of({:?}): visit_generics", def_id); + collector.visit_generics(generics); + } + + if let Some(fn_sig) = tcx.hir().fn_sig_by_hir_id(hir_id) { + debug!("const_evaluatable_predicates_of({:?}): visit_fn_decl", def_id); + collector.visit_fn_decl(fn_sig.decl); + } + debug!("const_evaluatable_predicates_of({:?}) = {:?}", def_id, collector.preds); + + collector.preds +} + +pub(super) fn trait_explicit_predicates_and_bounds( + tcx: TyCtxt<'_>, + def_id: LocalDefId, +) -> ty::GenericPredicates<'_> { + assert_eq!(tcx.def_kind(def_id), DefKind::Trait); + gather_explicit_predicates_of(tcx, def_id.to_def_id()) +} + +pub(super) fn explicit_predicates_of<'tcx>( + tcx: TyCtxt<'tcx>, + def_id: DefId, +) -> ty::GenericPredicates<'tcx> { + let def_kind = tcx.def_kind(def_id); + if let DefKind::Trait = def_kind { + // Remove bounds on associated types from the predicates, they will be + // returned by `explicit_item_bounds`. + let predicates_and_bounds = tcx.trait_explicit_predicates_and_bounds(def_id.expect_local()); + let trait_identity_substs = InternalSubsts::identity_for_item(tcx, def_id); + + let is_assoc_item_ty = |ty: Ty<'tcx>| { + // For a predicate from a where clause to become a bound on an + // associated type: + // * It must use the identity substs of the item. + // * Since any generic parameters on the item are not in scope, + // this means that the item is not a GAT, and its identity + // substs are the same as the trait's. + // * It must be an associated type for this trait (*not* a + // supertrait). + if let ty::Projection(projection) = ty.kind() { + projection.substs == trait_identity_substs + && tcx.associated_item(projection.item_def_id).container_id(tcx) == def_id + } else { + false + } + }; + + let predicates: Vec<_> = predicates_and_bounds + .predicates + .iter() + .copied() + .filter(|(pred, _)| match pred.kind().skip_binder() { + ty::PredicateKind::Trait(tr) => !is_assoc_item_ty(tr.self_ty()), + ty::PredicateKind::Projection(proj) => { + !is_assoc_item_ty(proj.projection_ty.self_ty()) + } + ty::PredicateKind::TypeOutlives(outlives) => !is_assoc_item_ty(outlives.0), + _ => true, + }) + .collect(); + if predicates.len() == predicates_and_bounds.predicates.len() { + predicates_and_bounds + } else { + ty::GenericPredicates { + parent: predicates_and_bounds.parent, + predicates: tcx.arena.alloc_slice(&predicates), + } + } + } else { + if matches!(def_kind, DefKind::AnonConst) && tcx.lazy_normalization() { + let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local()); + if tcx.hir().opt_const_param_default_param_hir_id(hir_id).is_some() { + // In `generics_of` we set the generics' parent to be our parent's parent which means that + // we lose out on the predicates of our actual parent if we dont return those predicates here. + // (See comment in `generics_of` for more information on why the parent shenanigans is necessary) + // + // struct Foo::ASSOC }>(T) where T: Trait; + // ^^^ ^^^^^^^^^^^^^^^^^^^^^^^ the def id we are calling + // ^^^ explicit_predicates_of on + // parent item we dont have set as the + // parent of generics returned by `generics_of` + // + // In the above code we want the anon const to have predicates in its param env for `T: Trait` + let item_def_id = tcx.hir().get_parent_item(hir_id); + // In the above code example we would be calling `explicit_predicates_of(Foo)` here + return tcx.explicit_predicates_of(item_def_id); + } + } + gather_explicit_predicates_of(tcx, def_id) + } +} + +/// Ensures that the super-predicates of the trait with a `DefId` +/// of `trait_def_id` are converted and stored. This also ensures that +/// the transitive super-predicates are converted. +pub(super) fn super_predicates_of( + tcx: TyCtxt<'_>, + trait_def_id: DefId, +) -> ty::GenericPredicates<'_> { + tcx.super_predicates_that_define_assoc_type((trait_def_id, None)) +} + +/// Ensures that the super-predicates of the trait with a `DefId` +/// of `trait_def_id` are converted and stored. This also ensures that +/// the transitive super-predicates are converted. +pub(super) fn super_predicates_that_define_assoc_type( + tcx: TyCtxt<'_>, + (trait_def_id, assoc_name): (DefId, Option), +) -> ty::GenericPredicates<'_> { + if trait_def_id.is_local() { + debug!("local trait"); + let trait_hir_id = tcx.hir().local_def_id_to_hir_id(trait_def_id.expect_local()); + + let Node::Item(item) = tcx.hir().get(trait_hir_id) else { + bug!("trait_node_id {} is not an item", trait_hir_id); + }; + + let (generics, bounds) = match item.kind { + hir::ItemKind::Trait(.., ref generics, ref supertraits, _) => (generics, supertraits), + hir::ItemKind::TraitAlias(ref generics, ref supertraits) => (generics, supertraits), + _ => span_bug!(item.span, "super_predicates invoked on non-trait"), + }; + + let icx = ItemCtxt::new(tcx, trait_def_id); + + // Convert the bounds that follow the colon, e.g., `Bar + Zed` in `trait Foo: Bar + Zed`. + let self_param_ty = tcx.types.self_param; + let superbounds1 = if let Some(assoc_name) = assoc_name { + >::compute_bounds_that_match_assoc_type( + &icx, + self_param_ty, + bounds, + assoc_name, + ) + } else { + >::compute_bounds(&icx, self_param_ty, bounds) + }; + + let superbounds1 = superbounds1.predicates(tcx, self_param_ty); + + // Convert any explicit superbounds in the where-clause, + // e.g., `trait Foo where Self: Bar`. + // In the case of trait aliases, however, we include all bounds in the where-clause, + // so e.g., `trait Foo = where u32: PartialEq` would include `u32: PartialEq` + // as one of its "superpredicates". + let is_trait_alias = tcx.is_trait_alias(trait_def_id); + let superbounds2 = icx.type_parameter_bounds_in_generics( + generics, + item.hir_id(), + self_param_ty, + OnlySelfBounds(!is_trait_alias), + assoc_name, + ); + + // Combine the two lists to form the complete set of superbounds: + let superbounds = &*tcx.arena.alloc_from_iter(superbounds1.into_iter().chain(superbounds2)); + debug!(?superbounds); + + // Now require that immediate supertraits are converted, + // which will, in turn, reach indirect supertraits. + if assoc_name.is_none() { + // Now require that immediate supertraits are converted, + // which will, in turn, reach indirect supertraits. + for &(pred, span) in superbounds { + debug!("superbound: {:?}", pred); + if let ty::PredicateKind::Trait(bound) = pred.kind().skip_binder() { + tcx.at(span).super_predicates_of(bound.def_id()); + } + } + } + + ty::GenericPredicates { parent: None, predicates: superbounds } + } else { + // if `assoc_name` is None, then the query should've been redirected to an + // external provider + assert!(assoc_name.is_some()); + tcx.super_predicates_of(trait_def_id) + } +} + +/// Returns the predicates defined on `item_def_id` of the form +/// `X: Foo` where `X` is the type parameter `def_id`. +#[instrument(level = "trace", skip(tcx))] +pub(super) fn type_param_predicates( + tcx: TyCtxt<'_>, + (item_def_id, def_id, assoc_name): (DefId, LocalDefId, Ident), +) -> ty::GenericPredicates<'_> { + use rustc_hir::*; + + // In the AST, bounds can derive from two places. Either + // written inline like `` or in a where-clause like + // `where T: Foo`. + + let param_id = tcx.hir().local_def_id_to_hir_id(def_id); + let param_owner = tcx.hir().ty_param_owner(def_id); + let generics = tcx.generics_of(param_owner); + let index = generics.param_def_id_to_index[&def_id.to_def_id()]; + let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(def_id)); + + // Don't look for bounds where the type parameter isn't in scope. + let parent = if item_def_id == param_owner.to_def_id() { + None + } else { + tcx.generics_of(item_def_id).parent + }; + + let mut result = parent + .map(|parent| { + let icx = ItemCtxt::new(tcx, parent); + icx.get_type_parameter_bounds(DUMMY_SP, def_id.to_def_id(), assoc_name) + }) + .unwrap_or_default(); + let mut extend = None; + + let item_hir_id = tcx.hir().local_def_id_to_hir_id(item_def_id.expect_local()); + let ast_generics = match tcx.hir().get(item_hir_id) { + Node::TraitItem(item) => &item.generics, + + Node::ImplItem(item) => &item.generics, + + Node::Item(item) => { + match item.kind { + ItemKind::Fn(.., ref generics, _) + | ItemKind::Impl(hir::Impl { ref generics, .. }) + | ItemKind::TyAlias(_, ref generics) + | ItemKind::OpaqueTy(OpaqueTy { + ref generics, + origin: hir::OpaqueTyOrigin::TyAlias, + .. + }) + | ItemKind::Enum(_, ref generics) + | ItemKind::Struct(_, ref generics) + | ItemKind::Union(_, ref generics) => generics, + ItemKind::Trait(_, _, ref generics, ..) => { + // Implied `Self: Trait` and supertrait bounds. + if param_id == item_hir_id { + let identity_trait_ref = ty::TraitRef::identity(tcx, item_def_id); + extend = + Some((identity_trait_ref.without_const().to_predicate(tcx), item.span)); + } + generics + } + _ => return result, + } + } + + Node::ForeignItem(item) => match item.kind { + ForeignItemKind::Fn(_, _, ref generics) => generics, + _ => return result, + }, + + _ => return result, + }; + + let icx = ItemCtxt::new(tcx, item_def_id); + let extra_predicates = extend.into_iter().chain( + icx.type_parameter_bounds_in_generics( + ast_generics, + param_id, + ty, + OnlySelfBounds(true), + Some(assoc_name), + ) + .into_iter() + .filter(|(predicate, _)| match predicate.kind().skip_binder() { + ty::PredicateKind::Trait(data) => data.self_ty().is_param(index), + _ => false, + }), + ); + result.predicates = + tcx.arena.alloc_from_iter(result.predicates.iter().copied().chain(extra_predicates)); + result +} + +impl<'tcx> ItemCtxt<'tcx> { + /// Finds bounds from `hir::Generics`. This requires scanning through the + /// AST. We do this to avoid having to convert *all* the bounds, which + /// would create artificial cycles. Instead, we can only convert the + /// bounds for a type parameter `X` if `X::Foo` is used. + #[instrument(level = "trace", skip(self, ast_generics))] + fn type_parameter_bounds_in_generics( + &self, + ast_generics: &'tcx hir::Generics<'tcx>, + param_id: hir::HirId, + ty: Ty<'tcx>, + only_self_bounds: OnlySelfBounds, + assoc_name: Option, + ) -> Vec<(ty::Predicate<'tcx>, Span)> { + let param_def_id = self.tcx.hir().local_def_id(param_id).to_def_id(); + trace!(?param_def_id); + ast_generics + .predicates + .iter() + .filter_map(|wp| match *wp { + hir::WherePredicate::BoundPredicate(ref bp) => Some(bp), + _ => None, + }) + .flat_map(|bp| { + let bt = if bp.is_param_bound(param_def_id) { + Some(ty) + } else if !only_self_bounds.0 { + Some(self.to_ty(bp.bounded_ty)) + } else { + None + }; + let bvars = self.tcx.late_bound_vars(bp.hir_id); + + bp.bounds.iter().filter_map(move |b| bt.map(|bt| (bt, b, bvars))).filter( + |(_, b, _)| match assoc_name { + Some(assoc_name) => self.bound_defines_assoc_item(b, assoc_name), + None => true, + }, + ) + }) + .flat_map(|(bt, b, bvars)| predicates_from_bound(self, bt, b, bvars)) + .collect() + } + + #[instrument(level = "trace", skip(self))] + fn bound_defines_assoc_item(&self, b: &hir::GenericBound<'_>, assoc_name: Ident) -> bool { + match b { + hir::GenericBound::Trait(poly_trait_ref, _) => { + let trait_ref = &poly_trait_ref.trait_ref; + if let Some(trait_did) = trait_ref.trait_def_id() { + self.tcx.trait_may_define_assoc_type(trait_did, assoc_name) + } else { + false + } + } + _ => false, + } + } +} + +/// Converts a specific `GenericBound` from the AST into a set of +/// predicates that apply to the self type. A vector is returned +/// because this can be anywhere from zero predicates (`T: ?Sized` adds no +/// predicates) to one (`T: Foo`) to many (`T: Bar` adds `T: Bar` +/// and `::X == i32`). +fn predicates_from_bound<'tcx>( + astconv: &dyn AstConv<'tcx>, + param_ty: Ty<'tcx>, + bound: &'tcx hir::GenericBound<'tcx>, + bound_vars: &'tcx ty::List, +) -> Vec<(ty::Predicate<'tcx>, Span)> { + let mut bounds = Bounds::default(); + astconv.add_bounds(param_ty, [bound].into_iter(), &mut bounds, bound_vars); + bounds.predicates(astconv.tcx(), param_ty).collect() +} diff --git a/compiler/rustc_hir_analysis/src/collect/type_of.rs b/compiler/rustc_hir_analysis/src/collect/type_of.rs new file mode 100644 index 000000000..c29a645eb --- /dev/null +++ b/compiler/rustc_hir_analysis/src/collect/type_of.rs @@ -0,0 +1,966 @@ +use rustc_errors::{Applicability, StashKey}; +use rustc_hir as hir; +use rustc_hir::def_id::{DefId, LocalDefId}; +use rustc_hir::intravisit; +use rustc_hir::intravisit::Visitor; +use rustc_hir::{HirId, Node}; +use rustc_middle::hir::nested_filter; +use rustc_middle::ty::subst::InternalSubsts; +use rustc_middle::ty::util::IntTypeExt; +use rustc_middle::ty::{self, DefIdTree, Ty, TyCtxt, TypeFolder, TypeSuperFoldable, TypeVisitable}; +use rustc_span::symbol::Ident; +use rustc_span::{Span, DUMMY_SP}; + +use super::ItemCtxt; +use super::{bad_placeholder, is_suggestable_infer_ty}; +use crate::errors::UnconstrainedOpaqueType; + +/// Computes the relevant generic parameter for a potential generic const argument. +/// +/// This should be called using the query `tcx.opt_const_param_of`. +pub(super) fn opt_const_param_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option { + use hir::*; + let hir_id = tcx.hir().local_def_id_to_hir_id(def_id); + + match tcx.hir().get(hir_id) { + Node::AnonConst(_) => (), + _ => return None, + }; + + let parent_node_id = tcx.hir().get_parent_node(hir_id); + let parent_node = tcx.hir().get(parent_node_id); + + let (generics, arg_idx) = match parent_node { + // This match arm is for when the def_id appears in a GAT whose + // path can't be resolved without typechecking e.g. + // + // trait Foo { + // type Assoc; + // fn foo() -> Self::Assoc<3>; + // } + // + // In the above code we would call this query with the def_id of 3 and + // the parent_node we match on would be the hir node for Self::Assoc<3> + // + // `Self::Assoc<3>` cant be resolved without typechecking here as we + // didnt write ::Assoc<3>. If we did then another match + // arm would handle this. + // + // I believe this match arm is only needed for GAT but I am not 100% sure - BoxyUwU + Node::Ty(hir_ty @ Ty { kind: TyKind::Path(QPath::TypeRelative(_, segment)), .. }) => { + // Find the Item containing the associated type so we can create an ItemCtxt. + // Using the ItemCtxt convert the HIR for the unresolved assoc type into a + // ty which is a fully resolved projection. + // For the code example above, this would mean converting Self::Assoc<3> + // into a ty::Projection(::Assoc<3>) + let item_hir_id = tcx + .hir() + .parent_iter(hir_id) + .filter(|(_, node)| matches!(node, Node::Item(_))) + .map(|(id, _)| id) + .next() + .unwrap(); + let item_did = tcx.hir().local_def_id(item_hir_id).to_def_id(); + let item_ctxt = &ItemCtxt::new(tcx, item_did) as &dyn crate::astconv::AstConv<'_>; + let ty = item_ctxt.ast_ty_to_ty(hir_ty); + + // Iterate through the generics of the projection to find the one that corresponds to + // the def_id that this query was called with. We filter to only type and const args here + // as a precaution for if it's ever allowed to elide lifetimes in GAT's. It currently isn't + // but it can't hurt to be safe ^^ + if let ty::Projection(projection) = ty.kind() { + let generics = tcx.generics_of(projection.item_def_id); + + let arg_index = segment + .args + .and_then(|args| { + args.args + .iter() + .filter(|arg| arg.is_ty_or_const()) + .position(|arg| arg.hir_id() == hir_id) + }) + .unwrap_or_else(|| { + bug!("no arg matching AnonConst in segment"); + }); + + (generics, arg_index) + } else { + // I dont think it's possible to reach this but I'm not 100% sure - BoxyUwU + tcx.sess.delay_span_bug( + tcx.def_span(def_id), + "unexpected non-GAT usage of an anon const", + ); + return None; + } + } + Node::Expr(&Expr { + kind: + ExprKind::MethodCall(segment, ..) | ExprKind::Path(QPath::TypeRelative(_, segment)), + .. + }) => { + let body_owner = tcx.hir().enclosing_body_owner(hir_id); + let tables = tcx.typeck(body_owner); + // This may fail in case the method/path does not actually exist. + // As there is no relevant param for `def_id`, we simply return + // `None` here. + let type_dependent_def = tables.type_dependent_def_id(parent_node_id)?; + let idx = segment + .args + .and_then(|args| { + args.args + .iter() + .filter(|arg| arg.is_ty_or_const()) + .position(|arg| arg.hir_id() == hir_id) + }) + .unwrap_or_else(|| { + bug!("no arg matching AnonConst in segment"); + }); + + (tcx.generics_of(type_dependent_def), idx) + } + + Node::Ty(&Ty { kind: TyKind::Path(_), .. }) + | Node::Expr(&Expr { kind: ExprKind::Path(_) | ExprKind::Struct(..), .. }) + | Node::TraitRef(..) + | Node::Pat(_) => { + let path = match parent_node { + Node::Ty(&Ty { kind: TyKind::Path(QPath::Resolved(_, path)), .. }) + | Node::TraitRef(&TraitRef { path, .. }) => &*path, + Node::Expr(&Expr { + kind: + ExprKind::Path(QPath::Resolved(_, path)) + | ExprKind::Struct(&QPath::Resolved(_, path), ..), + .. + }) => { + let body_owner = tcx.hir().enclosing_body_owner(hir_id); + let _tables = tcx.typeck(body_owner); + &*path + } + Node::Pat(pat) => { + if let Some(path) = get_path_containing_arg_in_pat(pat, hir_id) { + path + } else { + tcx.sess.delay_span_bug( + tcx.def_span(def_id), + &format!("unable to find const parent for {} in pat {:?}", hir_id, pat), + ); + return None; + } + } + _ => { + tcx.sess.delay_span_bug( + tcx.def_span(def_id), + &format!("unexpected const parent path {:?}", parent_node), + ); + return None; + } + }; + + // We've encountered an `AnonConst` in some path, so we need to + // figure out which generic parameter it corresponds to and return + // the relevant type. + let Some((arg_index, segment)) = path.segments.iter().find_map(|seg| { + let args = seg.args?; + args.args + .iter() + .filter(|arg| arg.is_ty_or_const()) + .position(|arg| arg.hir_id() == hir_id) + .map(|index| (index, seg)).or_else(|| args.bindings + .iter() + .filter_map(TypeBinding::opt_const) + .position(|ct| ct.hir_id == hir_id) + .map(|idx| (idx, seg))) + }) else { + tcx.sess.delay_span_bug( + tcx.def_span(def_id), + "no arg matching AnonConst in path", + ); + return None; + }; + + let generics = match tcx.res_generics_def_id(segment.res) { + Some(def_id) => tcx.generics_of(def_id), + None => { + tcx.sess.delay_span_bug( + tcx.def_span(def_id), + &format!("unexpected anon const res {:?} in path: {:?}", segment.res, path), + ); + return None; + } + }; + + (generics, arg_index) + } + _ => return None, + }; + + debug!(?parent_node); + debug!(?generics, ?arg_idx); + generics + .params + .iter() + .filter(|param| param.kind.is_ty_or_const()) + .nth(match generics.has_self && generics.parent.is_none() { + true => arg_idx + 1, + false => arg_idx, + }) + .and_then(|param| match param.kind { + ty::GenericParamDefKind::Const { .. } => { + debug!(?param); + Some(param.def_id) + } + _ => None, + }) +} + +fn get_path_containing_arg_in_pat<'hir>( + pat: &'hir hir::Pat<'hir>, + arg_id: HirId, +) -> Option<&'hir hir::Path<'hir>> { + use hir::*; + + let is_arg_in_path = |p: &hir::Path<'_>| { + p.segments + .iter() + .filter_map(|seg| seg.args) + .flat_map(|args| args.args) + .any(|arg| arg.hir_id() == arg_id) + }; + let mut arg_path = None; + pat.walk(|pat| match pat.kind { + PatKind::Struct(QPath::Resolved(_, path), _, _) + | PatKind::TupleStruct(QPath::Resolved(_, path), _, _) + | PatKind::Path(QPath::Resolved(_, path)) + if is_arg_in_path(path) => + { + arg_path = Some(path); + false + } + _ => true, + }); + arg_path +} + +pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> { + let def_id = def_id.expect_local(); + use rustc_hir::*; + + let hir_id = tcx.hir().local_def_id_to_hir_id(def_id); + + let icx = ItemCtxt::new(tcx, def_id.to_def_id()); + + match tcx.hir().get(hir_id) { + Node::TraitItem(item) => match item.kind { + TraitItemKind::Fn(..) => { + let substs = InternalSubsts::identity_for_item(tcx, def_id.to_def_id()); + tcx.mk_fn_def(def_id.to_def_id(), substs) + } + TraitItemKind::Const(ty, body_id) => body_id + .and_then(|body_id| { + if is_suggestable_infer_ty(ty) { + Some(infer_placeholder_type( + tcx, def_id, body_id, ty.span, item.ident, "constant", + )) + } else { + None + } + }) + .unwrap_or_else(|| icx.to_ty(ty)), + TraitItemKind::Type(_, Some(ty)) => icx.to_ty(ty), + TraitItemKind::Type(_, None) => { + span_bug!(item.span, "associated type missing default"); + } + }, + + Node::ImplItem(item) => match item.kind { + ImplItemKind::Fn(..) => { + let substs = InternalSubsts::identity_for_item(tcx, def_id.to_def_id()); + tcx.mk_fn_def(def_id.to_def_id(), substs) + } + ImplItemKind::Const(ty, body_id) => { + if is_suggestable_infer_ty(ty) { + infer_placeholder_type(tcx, def_id, body_id, ty.span, item.ident, "constant") + } else { + icx.to_ty(ty) + } + } + ImplItemKind::Type(ty) => { + if tcx.impl_trait_ref(tcx.hir().get_parent_item(hir_id)).is_none() { + check_feature_inherent_assoc_ty(tcx, item.span); + } + + icx.to_ty(ty) + } + }, + + Node::Item(item) => { + match item.kind { + ItemKind::Static(ty, .., body_id) => { + if is_suggestable_infer_ty(ty) { + infer_placeholder_type( + tcx, + def_id, + body_id, + ty.span, + item.ident, + "static variable", + ) + } else { + icx.to_ty(ty) + } + } + ItemKind::Const(ty, body_id) => { + if is_suggestable_infer_ty(ty) { + infer_placeholder_type( + tcx, def_id, body_id, ty.span, item.ident, "constant", + ) + } else { + icx.to_ty(ty) + } + } + ItemKind::TyAlias(self_ty, _) => icx.to_ty(self_ty), + ItemKind::Impl(hir::Impl { self_ty, .. }) => { + match self_ty.find_self_aliases() { + spans if spans.len() > 0 => { + tcx.sess.emit_err(crate::errors::SelfInImplSelf { span: spans.into(), note: (), }); + tcx.ty_error() + }, + _ => icx.to_ty(*self_ty), + } + }, + ItemKind::Fn(..) => { + let substs = InternalSubsts::identity_for_item(tcx, def_id.to_def_id()); + tcx.mk_fn_def(def_id.to_def_id(), substs) + } + ItemKind::Enum(..) | ItemKind::Struct(..) | ItemKind::Union(..) => { + let def = tcx.adt_def(def_id); + let substs = InternalSubsts::identity_for_item(tcx, def_id.to_def_id()); + tcx.mk_adt(def, substs) + } + ItemKind::OpaqueTy(OpaqueTy { origin: hir::OpaqueTyOrigin::TyAlias, .. }) => { + find_opaque_ty_constraints_for_tait(tcx, def_id) + } + // Opaque types desugared from `impl Trait`. + ItemKind::OpaqueTy(OpaqueTy { + origin: + hir::OpaqueTyOrigin::FnReturn(owner) | hir::OpaqueTyOrigin::AsyncFn(owner), + in_trait, + .. + }) => { + if in_trait { + assert!(tcx.impl_defaultness(owner).has_value()); + } + find_opaque_ty_constraints_for_rpit(tcx, def_id, owner) + } + ItemKind::Trait(..) + | ItemKind::TraitAlias(..) + | ItemKind::Macro(..) + | ItemKind::Mod(..) + | ItemKind::ForeignMod { .. } + | ItemKind::GlobalAsm(..) + | ItemKind::ExternCrate(..) + | ItemKind::Use(..) => { + span_bug!( + item.span, + "compute_type_of_item: unexpected item type: {:?}", + item.kind + ); + } + } + } + + Node::ForeignItem(foreign_item) => match foreign_item.kind { + ForeignItemKind::Fn(..) => { + let substs = InternalSubsts::identity_for_item(tcx, def_id.to_def_id()); + tcx.mk_fn_def(def_id.to_def_id(), substs) + } + ForeignItemKind::Static(t, _) => icx.to_ty(t), + ForeignItemKind::Type => tcx.mk_foreign(def_id.to_def_id()), + }, + + Node::Ctor(&ref def) | Node::Variant(Variant { data: ref def, .. }) => match *def { + VariantData::Unit(..) | VariantData::Struct(..) => { + tcx.type_of(tcx.hir().get_parent_item(hir_id)) + } + VariantData::Tuple(..) => { + let substs = InternalSubsts::identity_for_item(tcx, def_id.to_def_id()); + tcx.mk_fn_def(def_id.to_def_id(), substs) + } + }, + + Node::Field(field) => icx.to_ty(field.ty), + + Node::Expr(&Expr { kind: ExprKind::Closure { .. }, .. }) => { + tcx.typeck(def_id).node_type(hir_id) + } + + Node::AnonConst(_) if let Some(param) = tcx.opt_const_param_of(def_id) => { + // We defer to `type_of` of the corresponding parameter + // for generic arguments. + tcx.type_of(param) + } + + Node::AnonConst(_) => { + let parent_node = tcx.hir().get(tcx.hir().get_parent_node(hir_id)); + match parent_node { + Node::Ty(&Ty { kind: TyKind::Array(_, ref constant), .. }) + | Node::Expr(&Expr { kind: ExprKind::Repeat(_, ref constant), .. }) + if constant.hir_id() == hir_id => + { + tcx.types.usize + } + Node::Ty(&Ty { kind: TyKind::Typeof(ref e), .. }) if e.hir_id == hir_id => { + tcx.typeck(def_id).node_type(e.hir_id) + } + + Node::Expr(&Expr { kind: ExprKind::ConstBlock(ref anon_const), .. }) + if anon_const.hir_id == hir_id => + { + let substs = InternalSubsts::identity_for_item(tcx, def_id.to_def_id()); + substs.as_inline_const().ty() + } + + Node::Expr(&Expr { kind: ExprKind::InlineAsm(asm), .. }) + | Node::Item(&Item { kind: ItemKind::GlobalAsm(asm), .. }) + if asm.operands.iter().any(|(op, _op_sp)| match op { + hir::InlineAsmOperand::Const { anon_const } + | hir::InlineAsmOperand::SymFn { anon_const } => { + anon_const.hir_id == hir_id + } + _ => false, + }) => + { + tcx.typeck(def_id).node_type(hir_id) + } + + Node::Variant(Variant { disr_expr: Some(ref e), .. }) if e.hir_id == hir_id => { + tcx.adt_def(tcx.hir().get_parent_item(hir_id)).repr().discr_type().to_ty(tcx) + } + + Node::TypeBinding( + binding @ &TypeBinding { + hir_id: binding_id, + kind: TypeBindingKind::Equality { term: Term::Const(ref e) }, + .. + }, + ) if let Node::TraitRef(trait_ref) = + tcx.hir().get(tcx.hir().get_parent_node(binding_id)) + && e.hir_id == hir_id => + { + let Some(trait_def_id) = trait_ref.trait_def_id() else { + return tcx.ty_error_with_message(DUMMY_SP, "Could not find trait"); + }; + let assoc_items = tcx.associated_items(trait_def_id); + let assoc_item = assoc_items.find_by_name_and_kind( + tcx, + binding.ident, + ty::AssocKind::Const, + def_id.to_def_id(), + ); + if let Some(assoc_item) = assoc_item { + tcx.type_of(assoc_item.def_id) + } else { + // FIXME(associated_const_equality): add a useful error message here. + tcx.ty_error_with_message( + DUMMY_SP, + "Could not find associated const on trait", + ) + } + } + + Node::TypeBinding( + binding @ &TypeBinding { hir_id: binding_id, gen_args, ref kind, .. }, + ) if let Node::TraitRef(trait_ref) = + tcx.hir().get(tcx.hir().get_parent_node(binding_id)) + && let Some((idx, _)) = + gen_args.args.iter().enumerate().find(|(_, arg)| { + if let GenericArg::Const(ct) = arg { + ct.value.hir_id == hir_id + } else { + false + } + }) => + { + let Some(trait_def_id) = trait_ref.trait_def_id() else { + return tcx.ty_error_with_message(DUMMY_SP, "Could not find trait"); + }; + let assoc_items = tcx.associated_items(trait_def_id); + let assoc_item = assoc_items.find_by_name_and_kind( + tcx, + binding.ident, + match kind { + // I think `` type bindings requires that `A` is a type + TypeBindingKind::Constraint { .. } + | TypeBindingKind::Equality { term: Term::Ty(..) } => { + ty::AssocKind::Type + } + TypeBindingKind::Equality { term: Term::Const(..) } => { + ty::AssocKind::Const + } + }, + def_id.to_def_id(), + ); + if let Some(param) + = assoc_item.map(|item| &tcx.generics_of(item.def_id).params[idx]).filter(|param| param.kind.is_ty_or_const()) + { + tcx.type_of(param.def_id) + } else { + // FIXME(associated_const_equality): add a useful error message here. + tcx.ty_error_with_message( + DUMMY_SP, + "Could not find associated const on trait", + ) + } + } + + Node::GenericParam(&GenericParam { + hir_id: param_hir_id, + kind: GenericParamKind::Const { default: Some(ct), .. }, + .. + }) if ct.hir_id == hir_id => tcx.type_of(tcx.hir().local_def_id(param_hir_id)), + + x => tcx.ty_error_with_message( + DUMMY_SP, + &format!("unexpected const parent in type_of(): {x:?}"), + ), + } + } + + Node::GenericParam(param) => match ¶m.kind { + GenericParamKind::Type { default: Some(ty), .. } + | GenericParamKind::Const { ty, .. } => icx.to_ty(ty), + x => bug!("unexpected non-type Node::GenericParam: {:?}", x), + }, + + x => { + bug!("unexpected sort of node in type_of(): {:?}", x); + } + } +} + +#[instrument(skip(tcx), level = "debug")] +/// Checks "defining uses" of opaque `impl Trait` types to ensure that they meet the restrictions +/// laid for "higher-order pattern unification". +/// This ensures that inference is tractable. +/// In particular, definitions of opaque types can only use other generics as arguments, +/// and they cannot repeat an argument. Example: +/// +/// ```ignore (illustrative) +/// type Foo = impl Bar; +/// +/// // Okay -- `Foo` is applied to two distinct, generic types. +/// fn a() -> Foo { .. } +/// +/// // Not okay -- `Foo` is applied to `T` twice. +/// fn b() -> Foo { .. } +/// +/// // Not okay -- `Foo` is applied to a non-generic type. +/// fn b() -> Foo { .. } +/// ``` +/// +fn find_opaque_ty_constraints_for_tait(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Ty<'_> { + use rustc_hir::{Expr, ImplItem, Item, TraitItem}; + + struct ConstraintLocator<'tcx> { + tcx: TyCtxt<'tcx>, + + /// def_id of the opaque type whose defining uses are being checked + def_id: LocalDefId, + + /// as we walk the defining uses, we are checking that all of them + /// define the same hidden type. This variable is set to `Some` + /// with the first type that we find, and then later types are + /// checked against it (we also carry the span of that first + /// type). + found: Option>, + + /// In the presence of dead code, typeck may figure out a hidden type + /// while borrowck will now. We collect these cases here and check at + /// the end that we actually found a type that matches (modulo regions). + typeck_types: Vec>, + } + + impl ConstraintLocator<'_> { + #[instrument(skip(self), level = "debug")] + fn check(&mut self, item_def_id: LocalDefId) { + // Don't try to check items that cannot possibly constrain the type. + if !self.tcx.has_typeck_results(item_def_id) { + debug!("no constraint: no typeck results"); + return; + } + // Calling `mir_borrowck` can lead to cycle errors through + // const-checking, avoid calling it if we don't have to. + // ```rust + // type Foo = impl Fn() -> usize; // when computing type for this + // const fn bar() -> Foo { + // || 0usize + // } + // const BAZR: Foo = bar(); // we would mir-borrowck this, causing cycles + // // because we again need to reveal `Foo` so we can check whether the + // // constant does not contain interior mutability. + // ``` + let tables = self.tcx.typeck(item_def_id); + if let Some(_) = tables.tainted_by_errors { + self.found = Some(ty::OpaqueHiddenType { span: DUMMY_SP, ty: self.tcx.ty_error() }); + return; + } + let Some(&typeck_hidden_ty) = tables.concrete_opaque_types.get(&self.def_id) else { + debug!("no constraints in typeck results"); + return; + }; + if self.typeck_types.iter().all(|prev| prev.ty != typeck_hidden_ty.ty) { + self.typeck_types.push(typeck_hidden_ty); + } + + // Use borrowck to get the type with unerased regions. + let concrete_opaque_types = &self.tcx.mir_borrowck(item_def_id).concrete_opaque_types; + debug!(?concrete_opaque_types); + if let Some(&concrete_type) = concrete_opaque_types.get(&self.def_id) { + debug!(?concrete_type, "found constraint"); + if let Some(prev) = &mut self.found { + if concrete_type.ty != prev.ty && !(concrete_type, prev.ty).references_error() { + prev.report_mismatch(&concrete_type, self.tcx); + prev.ty = self.tcx.ty_error(); + } + } else { + self.found = Some(concrete_type); + } + } + } + } + + impl<'tcx> intravisit::Visitor<'tcx> for ConstraintLocator<'tcx> { + type NestedFilter = nested_filter::All; + + fn nested_visit_map(&mut self) -> Self::Map { + self.tcx.hir() + } + fn visit_expr(&mut self, ex: &'tcx Expr<'tcx>) { + if let hir::ExprKind::Closure { .. } = ex.kind { + let def_id = self.tcx.hir().local_def_id(ex.hir_id); + self.check(def_id); + } + intravisit::walk_expr(self, ex); + } + fn visit_item(&mut self, it: &'tcx Item<'tcx>) { + trace!(?it.owner_id); + // The opaque type itself or its children are not within its reveal scope. + if it.owner_id.def_id != self.def_id { + self.check(it.owner_id.def_id); + intravisit::walk_item(self, it); + } + } + fn visit_impl_item(&mut self, it: &'tcx ImplItem<'tcx>) { + trace!(?it.owner_id); + // The opaque type itself or its children are not within its reveal scope. + if it.owner_id.def_id != self.def_id { + self.check(it.owner_id.def_id); + intravisit::walk_impl_item(self, it); + } + } + fn visit_trait_item(&mut self, it: &'tcx TraitItem<'tcx>) { + trace!(?it.owner_id); + self.check(it.owner_id.def_id); + intravisit::walk_trait_item(self, it); + } + } + + let hir_id = tcx.hir().local_def_id_to_hir_id(def_id); + let scope = tcx.hir().get_defining_scope(hir_id); + let mut locator = ConstraintLocator { def_id: def_id, tcx, found: None, typeck_types: vec![] }; + + debug!(?scope); + + if scope == hir::CRATE_HIR_ID { + tcx.hir().walk_toplevel_module(&mut locator); + } else { + trace!("scope={:#?}", tcx.hir().get(scope)); + match tcx.hir().get(scope) { + // We explicitly call `visit_*` methods, instead of using `intravisit::walk_*` methods + // This allows our visitor to process the defining item itself, causing + // it to pick up any 'sibling' defining uses. + // + // For example, this code: + // ``` + // fn foo() { + // type Blah = impl Debug; + // let my_closure = || -> Blah { true }; + // } + // ``` + // + // requires us to explicitly process `foo()` in order + // to notice the defining usage of `Blah`. + Node::Item(it) => locator.visit_item(it), + Node::ImplItem(it) => locator.visit_impl_item(it), + Node::TraitItem(it) => locator.visit_trait_item(it), + other => bug!("{:?} is not a valid scope for an opaque type item", other), + } + } + + let Some(hidden) = locator.found else { + tcx.sess.emit_err(UnconstrainedOpaqueType { + span: tcx.def_span(def_id), + name: tcx.item_name(tcx.local_parent(def_id).to_def_id()), + what: match tcx.hir().get(scope) { + _ if scope == hir::CRATE_HIR_ID => "module", + Node::Item(hir::Item { kind: hir::ItemKind::Mod(_), .. }) => "module", + Node::Item(hir::Item { kind: hir::ItemKind::Impl(_), .. }) => "impl", + _ => "item", + }, + }); + return tcx.ty_error(); + }; + + // Only check against typeck if we didn't already error + if !hidden.ty.references_error() { + for concrete_type in locator.typeck_types { + if tcx.erase_regions(concrete_type.ty) != tcx.erase_regions(hidden.ty) + && !(concrete_type, hidden).references_error() + { + hidden.report_mismatch(&concrete_type, tcx); + } + } + } + + hidden.ty +} + +fn find_opaque_ty_constraints_for_rpit( + tcx: TyCtxt<'_>, + def_id: LocalDefId, + owner_def_id: LocalDefId, +) -> Ty<'_> { + use rustc_hir::{Expr, ImplItem, Item, TraitItem}; + + struct ConstraintChecker<'tcx> { + tcx: TyCtxt<'tcx>, + + /// def_id of the opaque type whose defining uses are being checked + def_id: LocalDefId, + + found: ty::OpaqueHiddenType<'tcx>, + } + + impl ConstraintChecker<'_> { + #[instrument(skip(self), level = "debug")] + fn check(&self, def_id: LocalDefId) { + // Use borrowck to get the type with unerased regions. + let concrete_opaque_types = &self.tcx.mir_borrowck(def_id).concrete_opaque_types; + debug!(?concrete_opaque_types); + for &(def_id, concrete_type) in concrete_opaque_types { + if def_id != self.def_id { + // Ignore constraints for other opaque types. + continue; + } + + debug!(?concrete_type, "found constraint"); + + if concrete_type.ty != self.found.ty + && !(concrete_type, self.found).references_error() + { + self.found.report_mismatch(&concrete_type, self.tcx); + } + } + } + } + + impl<'tcx> intravisit::Visitor<'tcx> for ConstraintChecker<'tcx> { + type NestedFilter = nested_filter::OnlyBodies; + + fn nested_visit_map(&mut self) -> Self::Map { + self.tcx.hir() + } + fn visit_expr(&mut self, ex: &'tcx Expr<'tcx>) { + if let hir::ExprKind::Closure { .. } = ex.kind { + let def_id = self.tcx.hir().local_def_id(ex.hir_id); + self.check(def_id); + } + intravisit::walk_expr(self, ex); + } + fn visit_item(&mut self, it: &'tcx Item<'tcx>) { + trace!(?it.owner_id); + // The opaque type itself or its children are not within its reveal scope. + if it.owner_id.def_id != self.def_id { + self.check(it.owner_id.def_id); + intravisit::walk_item(self, it); + } + } + fn visit_impl_item(&mut self, it: &'tcx ImplItem<'tcx>) { + trace!(?it.owner_id); + // The opaque type itself or its children are not within its reveal scope. + if it.owner_id.def_id != self.def_id { + self.check(it.owner_id.def_id); + intravisit::walk_impl_item(self, it); + } + } + fn visit_trait_item(&mut self, it: &'tcx TraitItem<'tcx>) { + trace!(?it.owner_id); + self.check(it.owner_id.def_id); + intravisit::walk_trait_item(self, it); + } + } + + let concrete = tcx.mir_borrowck(owner_def_id).concrete_opaque_types.get(&def_id).copied(); + + if let Some(concrete) = concrete { + let scope = tcx.hir().local_def_id_to_hir_id(owner_def_id); + debug!(?scope); + let mut locator = ConstraintChecker { def_id: def_id, tcx, found: concrete }; + + match tcx.hir().get(scope) { + Node::Item(it) => intravisit::walk_item(&mut locator, it), + Node::ImplItem(it) => intravisit::walk_impl_item(&mut locator, it), + Node::TraitItem(it) => intravisit::walk_trait_item(&mut locator, it), + other => bug!("{:?} is not a valid scope for an opaque type item", other), + } + } + + concrete.map(|concrete| concrete.ty).unwrap_or_else(|| { + let table = tcx.typeck(owner_def_id); + if let Some(_) = table.tainted_by_errors { + // Some error in the + // owner fn prevented us from populating + // the `concrete_opaque_types` table. + tcx.ty_error() + } else { + table.concrete_opaque_types.get(&def_id).map(|ty| ty.ty).unwrap_or_else(|| { + // We failed to resolve the opaque type or it + // resolves to itself. We interpret this as the + // no values of the hidden type ever being constructed, + // so we can just make the hidden type be `!`. + // For backwards compatibility reasons, we fall back to + // `()` until we the diverging default is changed. + tcx.mk_diverging_default() + }) + } + }) +} + +fn infer_placeholder_type<'a>( + tcx: TyCtxt<'a>, + def_id: LocalDefId, + body_id: hir::BodyId, + span: Span, + item_ident: Ident, + kind: &'static str, +) -> Ty<'a> { + // Attempts to make the type nameable by turning FnDefs into FnPtrs. + struct MakeNameable<'tcx> { + success: bool, + tcx: TyCtxt<'tcx>, + } + + impl<'tcx> MakeNameable<'tcx> { + fn new(tcx: TyCtxt<'tcx>) -> Self { + MakeNameable { success: true, tcx } + } + } + + impl<'tcx> TypeFolder<'tcx> for MakeNameable<'tcx> { + fn tcx(&self) -> TyCtxt<'tcx> { + self.tcx + } + + fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> { + if !self.success { + return ty; + } + + match ty.kind() { + ty::FnDef(def_id, _) => self.tcx.mk_fn_ptr(self.tcx.fn_sig(*def_id)), + // FIXME: non-capturing closures should also suggest a function pointer + ty::Closure(..) | ty::Generator(..) => { + self.success = false; + ty + } + _ => ty.super_fold_with(self), + } + } + } + + let ty = tcx.diagnostic_only_typeck(def_id).node_type(body_id.hir_id); + + // If this came from a free `const` or `static mut?` item, + // then the user may have written e.g. `const A = 42;`. + // In this case, the parser has stashed a diagnostic for + // us to improve in typeck so we do that now. + match tcx.sess.diagnostic().steal_diagnostic(span, StashKey::ItemNoType) { + Some(mut err) => { + if !ty.references_error() { + // Only suggest adding `:` if it was missing (and suggested by parsing diagnostic) + let colon = if span == item_ident.span.shrink_to_hi() { ":" } else { "" }; + + // The parser provided a sub-optimal `HasPlaceholders` suggestion for the type. + // We are typeck and have the real type, so remove that and suggest the actual type. + // FIXME(eddyb) this looks like it should be functionality on `Diagnostic`. + if let Ok(suggestions) = &mut err.suggestions { + suggestions.clear(); + } + + // Suggesting unnameable types won't help. + let mut mk_nameable = MakeNameable::new(tcx); + let ty = mk_nameable.fold_ty(ty); + let sugg_ty = if mk_nameable.success { Some(ty) } else { None }; + if let Some(sugg_ty) = sugg_ty { + err.span_suggestion( + span, + &format!("provide a type for the {item}", item = kind), + format!("{colon} {sugg_ty}"), + Applicability::MachineApplicable, + ); + } else { + err.span_note( + tcx.hir().body(body_id).value.span, + &format!("however, the inferred type `{}` cannot be named", ty), + ); + } + } + + err.emit(); + } + None => { + let mut diag = bad_placeholder(tcx, vec![span], kind); + + if !ty.references_error() { + let mut mk_nameable = MakeNameable::new(tcx); + let ty = mk_nameable.fold_ty(ty); + let sugg_ty = if mk_nameable.success { Some(ty) } else { None }; + if let Some(sugg_ty) = sugg_ty { + diag.span_suggestion( + span, + "replace with the correct type", + sugg_ty, + Applicability::MaybeIncorrect, + ); + } else { + diag.span_note( + tcx.hir().body(body_id).value.span, + &format!("however, the inferred type `{}` cannot be named", ty), + ); + } + } + + diag.emit(); + } + } + + // Typeck doesn't expect erased regions to be returned from `type_of`. + tcx.fold_regions(ty, |r, _| match *r { + ty::ReErased => tcx.lifetimes.re_static, + _ => r, + }) +} + +fn check_feature_inherent_assoc_ty(tcx: TyCtxt<'_>, span: Span) { + if !tcx.features().inherent_associated_types { + use rustc_session::parse::feature_err; + use rustc_span::symbol::sym; + feature_err( + &tcx.sess.parse_sess, + sym::inherent_associated_types, + span, + "inherent associated types are unstable", + ) + .emit(); + } +} -- cgit v1.2.3