use super::ResolverAstLoweringExt; use super::{AstOwner, ImplTraitContext, ImplTraitPosition}; use super::{FnDeclKind, LoweringContext, ParamMode}; use rustc_ast::ptr::P; use rustc_ast::visit::AssocCtxt; use rustc_ast::*; use rustc_data_structures::fx::FxHashMap; use rustc_data_structures::sorted_map::SortedMap; use rustc_errors::struct_span_err; use rustc_hir as hir; use rustc_hir::def::{DefKind, Res}; use rustc_hir::def_id::{LocalDefId, CRATE_DEF_ID}; use rustc_hir::PredicateOrigin; use rustc_index::vec::{Idx, IndexVec}; use rustc_middle::ty::{DefIdTree, ResolverAstLowering, TyCtxt}; use rustc_span::source_map::DesugaringKind; use rustc_span::symbol::{kw, sym, Ident}; use rustc_span::Span; use rustc_target::spec::abi; use smallvec::{smallvec, SmallVec}; use std::iter; pub(super) struct ItemLowerer<'a, 'hir> { pub(super) tcx: TyCtxt<'hir>, pub(super) resolver: &'a mut ResolverAstLowering, pub(super) ast_index: &'a IndexVec>, pub(super) owners: &'a mut IndexVec>>, } /// When we have a ty alias we *may* have two where clauses. To give the best diagnostics, we set the span /// to the where clause that is preferred, if it exists. Otherwise, it sets the span to the other where /// clause if it exists. fn add_ty_alias_where_clause( generics: &mut ast::Generics, mut where_clauses: (TyAliasWhereClause, TyAliasWhereClause), prefer_first: bool, ) { if !prefer_first { where_clauses = (where_clauses.1, where_clauses.0); } if where_clauses.0.0 || !where_clauses.1.0 { generics.where_clause.has_where_token = where_clauses.0.0; generics.where_clause.span = where_clauses.0.1; } else { generics.where_clause.has_where_token = where_clauses.1.0; generics.where_clause.span = where_clauses.1.1; } } impl<'a, 'hir> ItemLowerer<'a, 'hir> { fn with_lctx( &mut self, owner: NodeId, f: impl FnOnce(&mut LoweringContext<'_, 'hir>) -> hir::OwnerNode<'hir>, ) { let mut lctx = LoweringContext { // Pseudo-globals. tcx: self.tcx, resolver: self.resolver, arena: self.tcx.hir_arena, // HirId handling. bodies: Vec::new(), attrs: SortedMap::default(), children: FxHashMap::default(), current_hir_id_owner: CRATE_DEF_ID, item_local_id_counter: hir::ItemLocalId::new(0), node_id_to_local_id: Default::default(), local_id_to_def_id: SortedMap::new(), trait_map: Default::default(), // Lowering state. catch_scope: None, loop_scope: None, is_in_loop_condition: false, is_in_trait_impl: false, is_in_dyn_type: false, generator_kind: None, task_context: None, current_item: None, impl_trait_defs: Vec::new(), impl_trait_bounds: Vec::new(), allow_try_trait: Some([sym::try_trait_v2, sym::yeet_desugar_details][..].into()), allow_gen_future: Some([sym::gen_future][..].into()), allow_into_future: Some([sym::into_future][..].into()), }; lctx.with_hir_id_owner(owner, |lctx| f(lctx)); for (def_id, info) in lctx.children { self.owners.ensure_contains_elem(def_id, || hir::MaybeOwner::Phantom); debug_assert!(matches!(self.owners[def_id], hir::MaybeOwner::Phantom)); self.owners[def_id] = info; } } pub(super) fn lower_node( &mut self, def_id: LocalDefId, ) -> hir::MaybeOwner<&'hir hir::OwnerInfo<'hir>> { self.owners.ensure_contains_elem(def_id, || hir::MaybeOwner::Phantom); if let hir::MaybeOwner::Phantom = self.owners[def_id] { let node = self.ast_index[def_id]; match node { AstOwner::NonOwner => {} AstOwner::Crate(c) => self.lower_crate(c), AstOwner::Item(item) => self.lower_item(item), AstOwner::AssocItem(item, ctxt) => self.lower_assoc_item(item, ctxt), AstOwner::ForeignItem(item) => self.lower_foreign_item(item), } } self.owners[def_id] } #[instrument(level = "debug", skip(self, c))] fn lower_crate(&mut self, c: &Crate) { debug_assert_eq!(self.resolver.node_id_to_def_id[&CRATE_NODE_ID], CRATE_DEF_ID); self.with_lctx(CRATE_NODE_ID, |lctx| { let module = lctx.lower_mod(&c.items, &c.spans); lctx.lower_attrs(hir::CRATE_HIR_ID, &c.attrs); hir::OwnerNode::Crate(lctx.arena.alloc(module)) }) } #[instrument(level = "debug", skip(self))] fn lower_item(&mut self, item: &Item) { self.with_lctx(item.id, |lctx| hir::OwnerNode::Item(lctx.lower_item(item))) } fn lower_assoc_item(&mut self, item: &AssocItem, ctxt: AssocCtxt) { let def_id = self.resolver.node_id_to_def_id[&item.id]; let parent_id = self.tcx.local_parent(def_id); let parent_hir = self.lower_node(parent_id).unwrap(); self.with_lctx(item.id, |lctx| { // Evaluate with the lifetimes in `params` in-scope. // This is used to track which lifetimes have already been defined, // and which need to be replicated when lowering an async fn. match parent_hir.node().expect_item().kind { hir::ItemKind::Impl(hir::Impl { ref of_trait, .. }) => { lctx.is_in_trait_impl = of_trait.is_some(); } _ => {} }; match ctxt { AssocCtxt::Trait => hir::OwnerNode::TraitItem(lctx.lower_trait_item(item)), AssocCtxt::Impl => hir::OwnerNode::ImplItem(lctx.lower_impl_item(item)), } }) } fn lower_foreign_item(&mut self, item: &ForeignItem) { self.with_lctx(item.id, |lctx| hir::OwnerNode::ForeignItem(lctx.lower_foreign_item(item))) } } impl<'hir> LoweringContext<'_, 'hir> { pub(super) fn lower_mod(&mut self, items: &[P], spans: &ModSpans) -> hir::Mod<'hir> { hir::Mod { spans: hir::ModSpans { inner_span: self.lower_span(spans.inner_span), inject_use_span: self.lower_span(spans.inject_use_span), }, item_ids: self.arena.alloc_from_iter(items.iter().flat_map(|x| self.lower_item_ref(x))), } } pub(super) fn lower_item_ref(&mut self, i: &Item) -> SmallVec<[hir::ItemId; 1]> { let mut node_ids = smallvec![hir::ItemId { def_id: self.local_def_id(i.id) }]; if let ItemKind::Use(ref use_tree) = &i.kind { self.lower_item_id_use_tree(use_tree, i.id, &mut node_ids); } node_ids } fn lower_item_id_use_tree( &mut self, tree: &UseTree, base_id: NodeId, vec: &mut SmallVec<[hir::ItemId; 1]>, ) { match tree.kind { UseTreeKind::Nested(ref nested_vec) => { for &(ref nested, id) in nested_vec { vec.push(hir::ItemId { def_id: self.local_def_id(id) }); self.lower_item_id_use_tree(nested, id, vec); } } UseTreeKind::Glob => {} UseTreeKind::Simple(_, id1, id2) => { for (_, &id) in iter::zip(self.expect_full_res_from_use(base_id).skip(1), &[id1, id2]) { vec.push(hir::ItemId { def_id: self.local_def_id(id) }); } } } } fn lower_item(&mut self, i: &Item) -> &'hir hir::Item<'hir> { let mut ident = i.ident; let vis_span = self.lower_span(i.vis.span); let hir_id = self.lower_node_id(i.id); let attrs = self.lower_attrs(hir_id, &i.attrs); let kind = self.lower_item_kind(i.span, i.id, hir_id, &mut ident, attrs, vis_span, &i.kind); let item = hir::Item { def_id: hir_id.expect_owner(), ident: self.lower_ident(ident), kind, vis_span, span: self.lower_span(i.span), }; self.arena.alloc(item) } fn lower_item_kind( &mut self, span: Span, id: NodeId, hir_id: hir::HirId, ident: &mut Ident, attrs: Option<&'hir [Attribute]>, vis_span: Span, i: &ItemKind, ) -> hir::ItemKind<'hir> { match *i { ItemKind::ExternCrate(orig_name) => hir::ItemKind::ExternCrate(orig_name), ItemKind::Use(ref use_tree) => { // Start with an empty prefix. let prefix = Path { segments: vec![], span: use_tree.span, tokens: None }; self.lower_use_tree(use_tree, &prefix, id, vis_span, ident, attrs) } ItemKind::Static(ref t, m, ref e) => { let (ty, body_id) = self.lower_const_item(t, span, e.as_deref()); hir::ItemKind::Static(ty, m, body_id) } ItemKind::Const(_, ref t, ref e) => { let (ty, body_id) = self.lower_const_item(t, span, e.as_deref()); hir::ItemKind::Const(ty, body_id) } ItemKind::Fn(box Fn { sig: FnSig { ref decl, header, span: fn_sig_span }, ref generics, ref body, .. }) => { self.with_new_scopes(|this| { this.current_item = Some(ident.span); // Note: we don't need to change the return type from `T` to // `impl Future` here because lower_body // only cares about the input argument patterns in the function // declaration (decl), not the return types. let asyncness = header.asyncness; let body_id = this.lower_maybe_async_body(span, &decl, asyncness, body.as_deref()); let itctx = ImplTraitContext::Universal; let (generics, decl) = this.lower_generics(generics, id, itctx, |this| { let ret_id = asyncness.opt_return_id(); this.lower_fn_decl(&decl, Some(id), FnDeclKind::Fn, ret_id) }); let sig = hir::FnSig { decl, header: this.lower_fn_header(header), span: this.lower_span(fn_sig_span), }; hir::ItemKind::Fn(sig, generics, body_id) }) } ItemKind::Mod(_, ref mod_kind) => match mod_kind { ModKind::Loaded(items, _, spans) => { hir::ItemKind::Mod(self.lower_mod(items, spans)) } ModKind::Unloaded => panic!("`mod` items should have been loaded by now"), }, ItemKind::ForeignMod(ref fm) => hir::ItemKind::ForeignMod { abi: fm.abi.map_or(abi::Abi::FALLBACK, |abi| self.lower_abi(abi)), items: self .arena .alloc_from_iter(fm.items.iter().map(|x| self.lower_foreign_item_ref(x))), }, ItemKind::GlobalAsm(ref asm) => { hir::ItemKind::GlobalAsm(self.lower_inline_asm(span, asm)) } ItemKind::TyAlias(box TyAlias { ref generics, where_clauses, ty: Some(ref ty), .. }) => { // We lower // // type Foo = impl Trait // // to // // type Foo = Foo1 // opaque type Foo1: Trait let mut generics = generics.clone(); add_ty_alias_where_clause(&mut generics, where_clauses, true); let (generics, ty) = self.lower_generics( &generics, id, ImplTraitContext::Disallowed(ImplTraitPosition::Generic), |this| this.lower_ty(ty, ImplTraitContext::TypeAliasesOpaqueTy), ); hir::ItemKind::TyAlias(ty, generics) } ItemKind::TyAlias(box TyAlias { ref generics, ref where_clauses, ty: None, .. }) => { let mut generics = generics.clone(); add_ty_alias_where_clause(&mut generics, *where_clauses, true); let (generics, ty) = self.lower_generics( &generics, id, ImplTraitContext::Disallowed(ImplTraitPosition::Generic), |this| this.arena.alloc(this.ty(span, hir::TyKind::Err)), ); hir::ItemKind::TyAlias(ty, generics) } ItemKind::Enum(ref enum_definition, ref generics) => { let (generics, variants) = self.lower_generics( generics, id, ImplTraitContext::Disallowed(ImplTraitPosition::Generic), |this| { this.arena.alloc_from_iter( enum_definition.variants.iter().map(|x| this.lower_variant(x)), ) }, ); hir::ItemKind::Enum(hir::EnumDef { variants }, generics) } ItemKind::Struct(ref struct_def, ref generics) => { let (generics, struct_def) = self.lower_generics( generics, id, ImplTraitContext::Disallowed(ImplTraitPosition::Generic), |this| this.lower_variant_data(hir_id, struct_def), ); hir::ItemKind::Struct(struct_def, generics) } ItemKind::Union(ref vdata, ref generics) => { let (generics, vdata) = self.lower_generics( generics, id, ImplTraitContext::Disallowed(ImplTraitPosition::Generic), |this| this.lower_variant_data(hir_id, vdata), ); hir::ItemKind::Union(vdata, generics) } ItemKind::Impl(box Impl { unsafety, polarity, defaultness, constness, generics: ref ast_generics, of_trait: ref trait_ref, self_ty: ref ty, items: ref impl_items, }) => { // Lower the "impl header" first. This ordering is important // for in-band lifetimes! Consider `'a` here: // // impl Foo<'a> for u32 { // fn method(&'a self) { .. } // } // // Because we start by lowering the `Foo<'a> for u32` // part, we will add `'a` to the list of generics on // the impl. When we then encounter it later in the // method, it will not be considered an in-band // lifetime to be added, but rather a reference to a // parent lifetime. let itctx = ImplTraitContext::Universal; let (generics, (trait_ref, lowered_ty)) = self.lower_generics(ast_generics, id, itctx, |this| { let trait_ref = trait_ref.as_ref().map(|trait_ref| { this.lower_trait_ref( trait_ref, ImplTraitContext::Disallowed(ImplTraitPosition::Trait), ) }); let lowered_ty = this .lower_ty(ty, ImplTraitContext::Disallowed(ImplTraitPosition::Type)); (trait_ref, lowered_ty) }); let new_impl_items = self .arena .alloc_from_iter(impl_items.iter().map(|item| self.lower_impl_item_ref(item))); // `defaultness.has_value()` is never called for an `impl`, always `true` in order // to not cause an assertion failure inside the `lower_defaultness` function. let has_val = true; let (defaultness, defaultness_span) = self.lower_defaultness(defaultness, has_val); let polarity = match polarity { ImplPolarity::Positive => ImplPolarity::Positive, ImplPolarity::Negative(s) => ImplPolarity::Negative(self.lower_span(s)), }; hir::ItemKind::Impl(self.arena.alloc(hir::Impl { unsafety: self.lower_unsafety(unsafety), polarity, defaultness, defaultness_span, constness: self.lower_constness(constness), generics, of_trait: trait_ref, self_ty: lowered_ty, items: new_impl_items, })) } ItemKind::Trait(box Trait { is_auto, unsafety, ref generics, ref bounds, ref items, }) => { let (generics, (unsafety, items, bounds)) = self.lower_generics( generics, id, ImplTraitContext::Disallowed(ImplTraitPosition::Generic), |this| { let bounds = this.lower_param_bounds( bounds, ImplTraitContext::Disallowed(ImplTraitPosition::Bound), ); let items = this.arena.alloc_from_iter( items.iter().map(|item| this.lower_trait_item_ref(item)), ); let unsafety = this.lower_unsafety(unsafety); (unsafety, items, bounds) }, ); hir::ItemKind::Trait(is_auto, unsafety, generics, bounds, items) } ItemKind::TraitAlias(ref generics, ref bounds) => { let (generics, bounds) = self.lower_generics( generics, id, ImplTraitContext::Disallowed(ImplTraitPosition::Generic), |this| { this.lower_param_bounds( bounds, ImplTraitContext::Disallowed(ImplTraitPosition::Bound), ) }, ); hir::ItemKind::TraitAlias(generics, bounds) } ItemKind::MacroDef(MacroDef { ref body, macro_rules }) => { let body = P(self.lower_mac_args(body)); let macro_kind = self.resolver.decl_macro_kind(self.local_def_id(id)); hir::ItemKind::Macro(ast::MacroDef { body, macro_rules }, macro_kind) } ItemKind::MacCall(..) => { panic!("`TyMac` should have been expanded by now") } } } fn lower_const_item( &mut self, ty: &Ty, span: Span, body: Option<&Expr>, ) -> (&'hir hir::Ty<'hir>, hir::BodyId) { let ty = self.lower_ty(ty, ImplTraitContext::Disallowed(ImplTraitPosition::Type)); (ty, self.lower_const_body(span, body)) } #[instrument(level = "debug", skip(self))] fn lower_use_tree( &mut self, tree: &UseTree, prefix: &Path, id: NodeId, vis_span: Span, ident: &mut Ident, attrs: Option<&'hir [Attribute]>, ) -> hir::ItemKind<'hir> { let path = &tree.prefix; let segments = prefix.segments.iter().chain(path.segments.iter()).cloned().collect(); match tree.kind { UseTreeKind::Simple(rename, id1, id2) => { *ident = tree.ident(); // First, apply the prefix to the path. let mut path = Path { segments, span: path.span, tokens: None }; // Correctly resolve `self` imports. if path.segments.len() > 1 && path.segments.last().unwrap().ident.name == kw::SelfLower { let _ = path.segments.pop(); if rename.is_none() { *ident = path.segments.last().unwrap().ident; } } let mut resolutions = self.expect_full_res_from_use(id).fuse(); // We want to return *something* from this function, so hold onto the first item // for later. let ret_res = self.lower_res(resolutions.next().unwrap_or(Res::Err)); // Here, we are looping over namespaces, if they exist for the definition // being imported. We only handle type and value namespaces because we // won't be dealing with macros in the rest of the compiler. // Essentially a single `use` which imports two names is desugared into // two imports. for new_node_id in [id1, id2] { let new_id = self.local_def_id(new_node_id); let Some(res) = resolutions.next() else { // Associate an HirId to both ids even if there is no resolution. let _old = self.children.insert( new_id, hir::MaybeOwner::NonOwner(hir::HirId::make_owner(new_id)), ); debug_assert!(_old.is_none()); continue; }; let ident = *ident; let mut path = path.clone(); for seg in &mut path.segments { seg.id = self.next_node_id(); } let span = path.span; self.with_hir_id_owner(new_node_id, |this| { let res = this.lower_res(res); let path = this.lower_path_extra(res, &path, ParamMode::Explicit); let kind = hir::ItemKind::Use(path, hir::UseKind::Single); if let Some(attrs) = attrs { this.attrs.insert(hir::ItemLocalId::new(0), attrs); } let item = hir::Item { def_id: new_id, ident: this.lower_ident(ident), kind, vis_span, span: this.lower_span(span), }; hir::OwnerNode::Item(this.arena.alloc(item)) }); } let path = self.lower_path_extra(ret_res, &path, ParamMode::Explicit); hir::ItemKind::Use(path, hir::UseKind::Single) } UseTreeKind::Glob => { let path = self.lower_path( id, &Path { segments, span: path.span, tokens: None }, ParamMode::Explicit, ); hir::ItemKind::Use(path, hir::UseKind::Glob) } UseTreeKind::Nested(ref trees) => { // Nested imports are desugared into simple imports. // So, if we start with // // ``` // pub(x) use foo::{a, b}; // ``` // // we will create three items: // // ``` // pub(x) use foo::a; // pub(x) use foo::b; // pub(x) use foo::{}; // <-- this is called the `ListStem` // ``` // // The first two are produced by recursively invoking // `lower_use_tree` (and indeed there may be things // like `use foo::{a::{b, c}}` and so forth). They // wind up being directly added to // `self.items`. However, the structure of this // function also requires us to return one item, and // for that we return the `{}` import (called the // `ListStem`). let prefix = Path { segments, span: prefix.span.to(path.span), tokens: None }; // Add all the nested `PathListItem`s to the HIR. for &(ref use_tree, id) in trees { let new_hir_id = self.local_def_id(id); let mut prefix = prefix.clone(); // Give the segments new node-ids since they are being cloned. for seg in &mut prefix.segments { seg.id = self.next_node_id(); } // Each `use` import is an item and thus are owners of the // names in the path. Up to this point the nested import is // the current owner, since we want each desugared import to // own its own names, we have to adjust the owner before // lowering the rest of the import. self.with_hir_id_owner(id, |this| { let mut ident = *ident; let kind = this.lower_use_tree(use_tree, &prefix, id, vis_span, &mut ident, attrs); if let Some(attrs) = attrs { this.attrs.insert(hir::ItemLocalId::new(0), attrs); } let item = hir::Item { def_id: new_hir_id, ident: this.lower_ident(ident), kind, vis_span, span: this.lower_span(use_tree.span), }; hir::OwnerNode::Item(this.arena.alloc(item)) }); } let res = self.expect_full_res_from_use(id).next().unwrap_or(Res::Err); let res = self.lower_res(res); let path = self.lower_path_extra(res, &prefix, ParamMode::Explicit); hir::ItemKind::Use(path, hir::UseKind::ListStem) } } } fn lower_foreign_item(&mut self, i: &ForeignItem) -> &'hir hir::ForeignItem<'hir> { let hir_id = self.lower_node_id(i.id); let def_id = hir_id.expect_owner(); self.lower_attrs(hir_id, &i.attrs); let item = hir::ForeignItem { def_id, ident: self.lower_ident(i.ident), kind: match i.kind { ForeignItemKind::Fn(box Fn { ref sig, ref generics, .. }) => { let fdec = &sig.decl; let itctx = ImplTraitContext::Universal; let (generics, (fn_dec, fn_args)) = self.lower_generics(generics, i.id, itctx, |this| { ( // Disallow `impl Trait` in foreign items. this.lower_fn_decl(fdec, None, FnDeclKind::ExternFn, None), this.lower_fn_params_to_names(fdec), ) }); hir::ForeignItemKind::Fn(fn_dec, fn_args, generics) } ForeignItemKind::Static(ref t, m, _) => { let ty = self.lower_ty(t, ImplTraitContext::Disallowed(ImplTraitPosition::Type)); hir::ForeignItemKind::Static(ty, m) } ForeignItemKind::TyAlias(..) => hir::ForeignItemKind::Type, ForeignItemKind::MacCall(_) => panic!("macro shouldn't exist here"), }, vis_span: self.lower_span(i.vis.span), span: self.lower_span(i.span), }; self.arena.alloc(item) } fn lower_foreign_item_ref(&mut self, i: &ForeignItem) -> hir::ForeignItemRef { hir::ForeignItemRef { id: hir::ForeignItemId { def_id: self.local_def_id(i.id) }, ident: self.lower_ident(i.ident), span: self.lower_span(i.span), } } fn lower_variant(&mut self, v: &Variant) -> hir::Variant<'hir> { let id = self.lower_node_id(v.id); self.lower_attrs(id, &v.attrs); hir::Variant { id, data: self.lower_variant_data(id, &v.data), disr_expr: v.disr_expr.as_ref().map(|e| self.lower_anon_const(e)), ident: self.lower_ident(v.ident), span: self.lower_span(v.span), } } fn lower_variant_data( &mut self, parent_id: hir::HirId, vdata: &VariantData, ) -> hir::VariantData<'hir> { match *vdata { VariantData::Struct(ref fields, recovered) => hir::VariantData::Struct( self.arena .alloc_from_iter(fields.iter().enumerate().map(|f| self.lower_field_def(f))), recovered, ), VariantData::Tuple(ref fields, id) => { let ctor_id = self.lower_node_id(id); self.alias_attrs(ctor_id, parent_id); hir::VariantData::Tuple( self.arena.alloc_from_iter( fields.iter().enumerate().map(|f| self.lower_field_def(f)), ), ctor_id, ) } VariantData::Unit(id) => { let ctor_id = self.lower_node_id(id); self.alias_attrs(ctor_id, parent_id); hir::VariantData::Unit(ctor_id) } } } fn lower_field_def(&mut self, (index, f): (usize, &FieldDef)) -> hir::FieldDef<'hir> { let ty = if let TyKind::Path(ref qself, ref path) = f.ty.kind { let t = self.lower_path_ty( &f.ty, qself, path, ParamMode::ExplicitNamed, // no `'_` in declarations (Issue #61124) ImplTraitContext::Disallowed(ImplTraitPosition::Path), ); self.arena.alloc(t) } else { self.lower_ty(&f.ty, ImplTraitContext::Disallowed(ImplTraitPosition::Type)) }; let hir_id = self.lower_node_id(f.id); self.lower_attrs(hir_id, &f.attrs); hir::FieldDef { span: self.lower_span(f.span), hir_id, ident: match f.ident { Some(ident) => self.lower_ident(ident), // FIXME(jseyfried): positional field hygiene. None => Ident::new(sym::integer(index), self.lower_span(f.span)), }, vis_span: self.lower_span(f.vis.span), ty, } } fn lower_trait_item(&mut self, i: &AssocItem) -> &'hir hir::TraitItem<'hir> { let hir_id = self.lower_node_id(i.id); let trait_item_def_id = hir_id.expect_owner(); let (generics, kind, has_default) = match i.kind { AssocItemKind::Const(_, ref ty, ref default) => { let ty = self.lower_ty(ty, ImplTraitContext::Disallowed(ImplTraitPosition::Type)); let body = default.as_ref().map(|x| self.lower_const_body(i.span, Some(x))); (hir::Generics::empty(), hir::TraitItemKind::Const(ty, body), body.is_some()) } AssocItemKind::Fn(box Fn { ref sig, ref generics, body: None, .. }) => { let names = self.lower_fn_params_to_names(&sig.decl); let (generics, sig) = self.lower_method_sig(generics, sig, i.id, FnDeclKind::Trait, None); (generics, hir::TraitItemKind::Fn(sig, hir::TraitFn::Required(names)), false) } AssocItemKind::Fn(box Fn { ref sig, ref generics, body: Some(ref body), .. }) => { let asyncness = sig.header.asyncness; let body_id = self.lower_maybe_async_body(i.span, &sig.decl, asyncness, Some(&body)); let (generics, sig) = self.lower_method_sig( generics, sig, i.id, FnDeclKind::Trait, asyncness.opt_return_id(), ); (generics, hir::TraitItemKind::Fn(sig, hir::TraitFn::Provided(body_id)), true) } AssocItemKind::TyAlias(box TyAlias { ref generics, where_clauses, ref bounds, ref ty, .. }) => { let mut generics = generics.clone(); add_ty_alias_where_clause(&mut generics, where_clauses, false); let (generics, kind) = self.lower_generics( &generics, i.id, ImplTraitContext::Disallowed(ImplTraitPosition::Generic), |this| { let ty = ty.as_ref().map(|x| { this.lower_ty(x, ImplTraitContext::Disallowed(ImplTraitPosition::Type)) }); hir::TraitItemKind::Type( this.lower_param_bounds( bounds, ImplTraitContext::Disallowed(ImplTraitPosition::Generic), ), ty, ) }, ); (generics, kind, ty.is_some()) } AssocItemKind::MacCall(..) => panic!("macro item shouldn't exist at this point"), }; self.lower_attrs(hir_id, &i.attrs); let item = hir::TraitItem { def_id: trait_item_def_id, ident: self.lower_ident(i.ident), generics, kind, span: self.lower_span(i.span), defaultness: hir::Defaultness::Default { has_value: has_default }, }; self.arena.alloc(item) } fn lower_trait_item_ref(&mut self, i: &AssocItem) -> hir::TraitItemRef { let kind = match &i.kind { AssocItemKind::Const(..) => hir::AssocItemKind::Const, AssocItemKind::TyAlias(..) => hir::AssocItemKind::Type, AssocItemKind::Fn(box Fn { sig, .. }) => { hir::AssocItemKind::Fn { has_self: sig.decl.has_self() } } AssocItemKind::MacCall(..) => unimplemented!(), }; let id = hir::TraitItemId { def_id: self.local_def_id(i.id) }; hir::TraitItemRef { id, ident: self.lower_ident(i.ident), span: self.lower_span(i.span), kind, } } /// Construct `ExprKind::Err` for the given `span`. pub(crate) fn expr_err(&mut self, span: Span) -> hir::Expr<'hir> { self.expr(span, hir::ExprKind::Err, AttrVec::new()) } fn lower_impl_item(&mut self, i: &AssocItem) -> &'hir hir::ImplItem<'hir> { // Since `default impl` is not yet implemented, this is always true in impls. let has_value = true; let (defaultness, _) = self.lower_defaultness(i.kind.defaultness(), has_value); let (generics, kind) = match &i.kind { AssocItemKind::Const(_, ty, expr) => { let ty = self.lower_ty(ty, ImplTraitContext::Disallowed(ImplTraitPosition::Type)); ( hir::Generics::empty(), hir::ImplItemKind::Const(ty, self.lower_const_body(i.span, expr.as_deref())), ) } AssocItemKind::Fn(box Fn { sig, generics, body, .. }) => { self.current_item = Some(i.span); let asyncness = sig.header.asyncness; let body_id = self.lower_maybe_async_body(i.span, &sig.decl, asyncness, body.as_deref()); let (generics, sig) = self.lower_method_sig( generics, sig, i.id, if self.is_in_trait_impl { FnDeclKind::Impl } else { FnDeclKind::Inherent }, asyncness.opt_return_id(), ); (generics, hir::ImplItemKind::Fn(sig, body_id)) } AssocItemKind::TyAlias(box TyAlias { generics, where_clauses, ty, .. }) => { let mut generics = generics.clone(); add_ty_alias_where_clause(&mut generics, *where_clauses, false); self.lower_generics( &generics, i.id, ImplTraitContext::Disallowed(ImplTraitPosition::Generic), |this| match ty { None => { let ty = this.arena.alloc(this.ty(i.span, hir::TyKind::Err)); hir::ImplItemKind::TyAlias(ty) } Some(ty) => { let ty = this.lower_ty(ty, ImplTraitContext::TypeAliasesOpaqueTy); hir::ImplItemKind::TyAlias(ty) } }, ) } AssocItemKind::MacCall(..) => panic!("`TyMac` should have been expanded by now"), }; let hir_id = self.lower_node_id(i.id); self.lower_attrs(hir_id, &i.attrs); let item = hir::ImplItem { def_id: hir_id.expect_owner(), ident: self.lower_ident(i.ident), generics, kind, vis_span: self.lower_span(i.vis.span), span: self.lower_span(i.span), defaultness, }; self.arena.alloc(item) } fn lower_impl_item_ref(&mut self, i: &AssocItem) -> hir::ImplItemRef { hir::ImplItemRef { id: hir::ImplItemId { def_id: self.local_def_id(i.id) }, ident: self.lower_ident(i.ident), span: self.lower_span(i.span), kind: match &i.kind { AssocItemKind::Const(..) => hir::AssocItemKind::Const, AssocItemKind::TyAlias(..) => hir::AssocItemKind::Type, AssocItemKind::Fn(box Fn { sig, .. }) => { hir::AssocItemKind::Fn { has_self: sig.decl.has_self() } } AssocItemKind::MacCall(..) => unimplemented!(), }, trait_item_def_id: self.resolver.get_partial_res(i.id).map(|r| r.base_res().def_id()), } } fn lower_defaultness( &self, d: Defaultness, has_value: bool, ) -> (hir::Defaultness, Option) { match d { Defaultness::Default(sp) => { (hir::Defaultness::Default { has_value }, Some(self.lower_span(sp))) } Defaultness::Final => { assert!(has_value); (hir::Defaultness::Final, None) } } } fn record_body( &mut self, params: &'hir [hir::Param<'hir>], value: hir::Expr<'hir>, ) -> hir::BodyId { let body = hir::Body { generator_kind: self.generator_kind, params, value }; let id = body.id(); debug_assert_eq!(id.hir_id.owner, self.current_hir_id_owner); self.bodies.push((id.hir_id.local_id, self.arena.alloc(body))); id } pub(super) fn lower_body( &mut self, f: impl FnOnce(&mut Self) -> (&'hir [hir::Param<'hir>], hir::Expr<'hir>), ) -> hir::BodyId { let prev_gen_kind = self.generator_kind.take(); let task_context = self.task_context.take(); let (parameters, result) = f(self); let body_id = self.record_body(parameters, result); self.task_context = task_context; self.generator_kind = prev_gen_kind; body_id } fn lower_param(&mut self, param: &Param) -> hir::Param<'hir> { let hir_id = self.lower_node_id(param.id); self.lower_attrs(hir_id, ¶m.attrs); hir::Param { hir_id, pat: self.lower_pat(¶m.pat), ty_span: self.lower_span(param.ty.span), span: self.lower_span(param.span), } } pub(super) fn lower_fn_body( &mut self, decl: &FnDecl, body: impl FnOnce(&mut Self) -> hir::Expr<'hir>, ) -> hir::BodyId { self.lower_body(|this| { ( this.arena.alloc_from_iter(decl.inputs.iter().map(|x| this.lower_param(x))), body(this), ) }) } fn lower_fn_body_block( &mut self, span: Span, decl: &FnDecl, body: Option<&Block>, ) -> hir::BodyId { self.lower_fn_body(decl, |this| this.lower_block_expr_opt(span, body)) } fn lower_block_expr_opt(&mut self, span: Span, block: Option<&Block>) -> hir::Expr<'hir> { match block { Some(block) => self.lower_block_expr(block), None => self.expr_err(span), } } pub(super) fn lower_const_body(&mut self, span: Span, expr: Option<&Expr>) -> hir::BodyId { self.lower_body(|this| { ( &[], match expr { Some(expr) => this.lower_expr_mut(expr), None => this.expr_err(span), }, ) }) } fn lower_maybe_async_body( &mut self, span: Span, decl: &FnDecl, asyncness: Async, body: Option<&Block>, ) -> hir::BodyId { let closure_id = match asyncness { Async::Yes { closure_id, .. } => closure_id, Async::No => return self.lower_fn_body_block(span, decl, body), }; self.lower_body(|this| { let mut parameters: Vec> = Vec::new(); let mut statements: Vec> = Vec::new(); // Async function parameters are lowered into the closure body so that they are // captured and so that the drop order matches the equivalent non-async functions. // // from: // // async fn foo(: , : , : ) { // // } // // into: // // fn foo(__arg0: , __arg1: , __arg2: ) { // async move { // let __arg2 = __arg2; // let = __arg2; // let __arg1 = __arg1; // let = __arg1; // let __arg0 = __arg0; // let = __arg0; // drop-temps { } // see comments later in fn for details // } // } // // If `` is a simple ident, then it is lowered to a single // `let = ;` statement as an optimization. // // Note that the body is embedded in `drop-temps`; an // equivalent desugaring would be `return { // };`. The key point is that we wish to drop all the // let-bound variables and temporaries created in the body // (and its tail expression!) before we drop the // parameters (c.f. rust-lang/rust#64512). for (index, parameter) in decl.inputs.iter().enumerate() { let parameter = this.lower_param(parameter); let span = parameter.pat.span; // Check if this is a binding pattern, if so, we can optimize and avoid adding a // `let = __argN;` statement. In this case, we do not rename the parameter. let (ident, is_simple_parameter) = match parameter.pat.kind { hir::PatKind::Binding( hir::BindingAnnotation::Unannotated | hir::BindingAnnotation::Mutable, _, ident, _, ) => (ident, true), // For `ref mut` or wildcard arguments, we can't reuse the binding, but // we can keep the same name for the parameter. // This lets rustdoc render it correctly in documentation. hir::PatKind::Binding(_, _, ident, _) => (ident, false), hir::PatKind::Wild => { (Ident::with_dummy_span(rustc_span::symbol::kw::Underscore), false) } _ => { // Replace the ident for bindings that aren't simple. let name = format!("__arg{}", index); let ident = Ident::from_str(&name); (ident, false) } }; let desugared_span = this.mark_span_with_reason(DesugaringKind::Async, span, None); // Construct a parameter representing `__argN: ` to replace the parameter of the // async function. // // If this is the simple case, this parameter will end up being the same as the // original parameter, but with a different pattern id. let stmt_attrs = this.attrs.get(¶meter.hir_id.local_id).copied(); let (new_parameter_pat, new_parameter_id) = this.pat_ident(desugared_span, ident); let new_parameter = hir::Param { hir_id: parameter.hir_id, pat: new_parameter_pat, ty_span: this.lower_span(parameter.ty_span), span: this.lower_span(parameter.span), }; if is_simple_parameter { // If this is the simple case, then we only insert one statement that is // `let = ;`. We re-use the original argument's pattern so that // `HirId`s are densely assigned. let expr = this.expr_ident(desugared_span, ident, new_parameter_id); let stmt = this.stmt_let_pat( stmt_attrs, desugared_span, Some(expr), parameter.pat, hir::LocalSource::AsyncFn, ); statements.push(stmt); } else { // If this is not the simple case, then we construct two statements: // // ``` // let __argN = __argN; // let = __argN; // ``` // // The first statement moves the parameter into the closure and thus ensures // that the drop order is correct. // // The second statement creates the bindings that the user wrote. // Construct the `let mut __argN = __argN;` statement. It must be a mut binding // because the user may have specified a `ref mut` binding in the next // statement. let (move_pat, move_id) = this.pat_ident_binding_mode( desugared_span, ident, hir::BindingAnnotation::Mutable, ); let move_expr = this.expr_ident(desugared_span, ident, new_parameter_id); let move_stmt = this.stmt_let_pat( None, desugared_span, Some(move_expr), move_pat, hir::LocalSource::AsyncFn, ); // Construct the `let = __argN;` statement. We re-use the original // parameter's pattern so that `HirId`s are densely assigned. let pattern_expr = this.expr_ident(desugared_span, ident, move_id); let pattern_stmt = this.stmt_let_pat( stmt_attrs, desugared_span, Some(pattern_expr), parameter.pat, hir::LocalSource::AsyncFn, ); statements.push(move_stmt); statements.push(pattern_stmt); }; parameters.push(new_parameter); } let body_span = body.map_or(span, |b| b.span); let async_expr = this.make_async_expr( CaptureBy::Value, closure_id, None, body_span, hir::AsyncGeneratorKind::Fn, |this| { // Create a block from the user's function body: let user_body = this.lower_block_expr_opt(body_span, body); // Transform into `drop-temps { }`, an expression: let desugared_span = this.mark_span_with_reason(DesugaringKind::Async, user_body.span, None); let user_body = this.expr_drop_temps( desugared_span, this.arena.alloc(user_body), AttrVec::new(), ); // As noted above, create the final block like // // ``` // { // let $param_pattern = $raw_param; // ... // drop-temps { } // } // ``` let body = this.block_all( desugared_span, this.arena.alloc_from_iter(statements), Some(user_body), ); this.expr_block(body, AttrVec::new()) }, ); ( this.arena.alloc_from_iter(parameters), this.expr(body_span, async_expr, AttrVec::new()), ) }) } fn lower_method_sig( &mut self, generics: &Generics, sig: &FnSig, id: NodeId, kind: FnDeclKind, is_async: Option, ) -> (&'hir hir::Generics<'hir>, hir::FnSig<'hir>) { let header = self.lower_fn_header(sig.header); let itctx = ImplTraitContext::Universal; let (generics, decl) = self.lower_generics(generics, id, itctx, |this| { this.lower_fn_decl(&sig.decl, Some(id), kind, is_async) }); (generics, hir::FnSig { header, decl, span: self.lower_span(sig.span) }) } fn lower_fn_header(&mut self, h: FnHeader) -> hir::FnHeader { hir::FnHeader { unsafety: self.lower_unsafety(h.unsafety), asyncness: self.lower_asyncness(h.asyncness), constness: self.lower_constness(h.constness), abi: self.lower_extern(h.ext), } } pub(super) fn lower_abi(&mut self, abi: StrLit) -> abi::Abi { abi::lookup(abi.symbol_unescaped.as_str()).unwrap_or_else(|| { self.error_on_invalid_abi(abi); abi::Abi::Rust }) } pub(super) fn lower_extern(&mut self, ext: Extern) -> abi::Abi { match ext { Extern::None => abi::Abi::Rust, Extern::Implicit(_) => abi::Abi::FALLBACK, Extern::Explicit(abi, _) => self.lower_abi(abi), } } fn error_on_invalid_abi(&self, abi: StrLit) { struct_span_err!(self.tcx.sess, abi.span, E0703, "invalid ABI: found `{}`", abi.symbol) .span_label(abi.span, "invalid ABI") .help(&format!("valid ABIs: {}", abi::all_names().join(", "))) .emit(); } fn lower_asyncness(&mut self, a: Async) -> hir::IsAsync { match a { Async::Yes { .. } => hir::IsAsync::Async, Async::No => hir::IsAsync::NotAsync, } } fn lower_constness(&mut self, c: Const) -> hir::Constness { match c { Const::Yes(_) => hir::Constness::Const, Const::No => hir::Constness::NotConst, } } pub(super) fn lower_unsafety(&mut self, u: Unsafe) -> hir::Unsafety { match u { Unsafe::Yes(_) => hir::Unsafety::Unsafe, Unsafe::No => hir::Unsafety::Normal, } } /// Return the pair of the lowered `generics` as `hir::Generics` and the evaluation of `f` with /// the carried impl trait definitions and bounds. #[instrument(level = "debug", skip(self, f))] fn lower_generics( &mut self, generics: &Generics, parent_node_id: NodeId, itctx: ImplTraitContext, f: impl FnOnce(&mut Self) -> T, ) -> (&'hir hir::Generics<'hir>, T) { debug_assert!(self.impl_trait_defs.is_empty()); debug_assert!(self.impl_trait_bounds.is_empty()); // Error if `?Trait` bounds in where clauses don't refer directly to type parameters. // Note: we used to clone these bounds directly onto the type parameter (and avoid lowering // these into hir when we lower thee where clauses), but this makes it quite difficult to // keep track of the Span info. Now, `add_implicitly_sized` in `AstConv` checks both param bounds and // where clauses for `?Sized`. for pred in &generics.where_clause.predicates { let WherePredicate::BoundPredicate(ref bound_pred) = *pred else { continue; }; let compute_is_param = || { // Check if the where clause type is a plain type parameter. match self .resolver .get_partial_res(bound_pred.bounded_ty.id) .map(|d| (d.base_res(), d.unresolved_segments())) { Some((Res::Def(DefKind::TyParam, def_id), 0)) if bound_pred.bound_generic_params.is_empty() => { generics .params .iter() .any(|p| def_id == self.local_def_id(p.id).to_def_id()) } // Either the `bounded_ty` is not a plain type parameter, or // it's not found in the generic type parameters list. _ => false, } }; // We only need to compute this once per `WherePredicate`, but don't // need to compute this at all unless there is a Maybe bound. let mut is_param: Option = None; for bound in &bound_pred.bounds { if !matches!(*bound, GenericBound::Trait(_, TraitBoundModifier::Maybe)) { continue; } let is_param = *is_param.get_or_insert_with(compute_is_param); if !is_param { self.diagnostic().span_err( bound.span(), "`?Trait` bounds are only permitted at the \ point where a type parameter is declared", ); } } } let mut predicates: SmallVec<[hir::WherePredicate<'hir>; 4]> = SmallVec::new(); predicates.extend(generics.params.iter().filter_map(|param| { self.lower_generic_bound_predicate( param.ident, param.id, ¶m.kind, ¶m.bounds, itctx, PredicateOrigin::GenericParam, ) })); predicates.extend( generics .where_clause .predicates .iter() .map(|predicate| self.lower_where_predicate(predicate)), ); let mut params: SmallVec<[hir::GenericParam<'hir>; 4]> = self.lower_generic_params_mut(&generics.params).collect(); // Introduce extra lifetimes if late resolution tells us to. let extra_lifetimes = self.resolver.take_extra_lifetime_params(parent_node_id); params.extend(extra_lifetimes.into_iter().filter_map(|(ident, node_id, res)| { self.lifetime_res_to_generic_param(ident, node_id, res) })); let has_where_clause_predicates = !generics.where_clause.predicates.is_empty(); let where_clause_span = self.lower_span(generics.where_clause.span); let span = self.lower_span(generics.span); let res = f(self); let impl_trait_defs = std::mem::take(&mut self.impl_trait_defs); params.extend(impl_trait_defs.into_iter()); let impl_trait_bounds = std::mem::take(&mut self.impl_trait_bounds); predicates.extend(impl_trait_bounds.into_iter()); let lowered_generics = self.arena.alloc(hir::Generics { params: self.arena.alloc_from_iter(params), predicates: self.arena.alloc_from_iter(predicates), has_where_clause_predicates, where_clause_span, span, }); (lowered_generics, res) } pub(super) fn lower_generic_bound_predicate( &mut self, ident: Ident, id: NodeId, kind: &GenericParamKind, bounds: &[GenericBound], itctx: ImplTraitContext, origin: PredicateOrigin, ) -> Option> { // Do not create a clause if we do not have anything inside it. if bounds.is_empty() { return None; } let bounds = self.lower_param_bounds(bounds, itctx); let ident = self.lower_ident(ident); let param_span = ident.span; let span = bounds .iter() .fold(Some(param_span.shrink_to_hi()), |span: Option, bound| { let bound_span = bound.span(); // We include bounds that come from a `#[derive(_)]` but point at the user's code, // as we use this method to get a span appropriate for suggestions. if !bound_span.can_be_used_for_suggestions() { None } else if let Some(span) = span { Some(span.to(bound_span)) } else { Some(bound_span) } }) .unwrap_or(param_span.shrink_to_hi()); match kind { GenericParamKind::Const { .. } => None, GenericParamKind::Type { .. } => { let def_id = self.local_def_id(id).to_def_id(); let ty_path = self.arena.alloc(hir::Path { span: param_span, res: Res::Def(DefKind::TyParam, def_id), segments: self.arena.alloc_from_iter([hir::PathSegment::from_ident(ident)]), }); let ty_id = self.next_id(); let bounded_ty = self.ty_path(ty_id, param_span, hir::QPath::Resolved(None, ty_path)); Some(hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate { bounded_ty: self.arena.alloc(bounded_ty), bounds, span, bound_generic_params: &[], origin, })) } GenericParamKind::Lifetime => { let ident_span = self.lower_span(ident.span); let ident = self.lower_ident(ident); let lt_id = self.next_node_id(); let lifetime = self.new_named_lifetime(id, lt_id, ident_span, ident); Some(hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate { lifetime, span, bounds, in_where_clause: false, })) } } } fn lower_where_predicate(&mut self, pred: &WherePredicate) -> hir::WherePredicate<'hir> { match *pred { WherePredicate::BoundPredicate(WhereBoundPredicate { ref bound_generic_params, ref bounded_ty, ref bounds, span, }) => hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate { bound_generic_params: self.lower_generic_params(bound_generic_params), bounded_ty: self .lower_ty(bounded_ty, ImplTraitContext::Disallowed(ImplTraitPosition::Type)), bounds: self.arena.alloc_from_iter(bounds.iter().map(|bound| { self.lower_param_bound( bound, ImplTraitContext::Disallowed(ImplTraitPosition::Bound), ) })), span: self.lower_span(span), origin: PredicateOrigin::WhereClause, }), WherePredicate::RegionPredicate(WhereRegionPredicate { ref lifetime, ref bounds, span, }) => hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate { span: self.lower_span(span), lifetime: self.lower_lifetime(lifetime), bounds: self.lower_param_bounds( bounds, ImplTraitContext::Disallowed(ImplTraitPosition::Bound), ), in_where_clause: true, }), WherePredicate::EqPredicate(WhereEqPredicate { id, ref lhs_ty, ref rhs_ty, span }) => { hir::WherePredicate::EqPredicate(hir::WhereEqPredicate { hir_id: self.lower_node_id(id), lhs_ty: self .lower_ty(lhs_ty, ImplTraitContext::Disallowed(ImplTraitPosition::Type)), rhs_ty: self .lower_ty(rhs_ty, ImplTraitContext::Disallowed(ImplTraitPosition::Type)), span: self.lower_span(span), }) } } } }