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-rw-r--r--compiler/rustc_ast_lowering/src/item.rs1513
1 files changed, 1513 insertions, 0 deletions
diff --git a/compiler/rustc_ast_lowering/src/item.rs b/compiler/rustc_ast_lowering/src/item.rs
new file mode 100644
index 000000000..ee4c0036f
--- /dev/null
+++ b/compiler/rustc_ast_lowering/src/item.rs
@@ -0,0 +1,1513 @@
+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<LocalDefId, AstOwner<'a>>,
+ pub(super) owners: &'a mut IndexVec<LocalDefId, hir::MaybeOwner<&'hir hir::OwnerInfo<'hir>>>,
+}
+
+/// 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<Item>], 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<Output = T>` 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<Span>) {
+ 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, &param.attrs);
+ hir::Param {
+ hir_id,
+ pat: self.lower_pat(&param.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<hir::Param<'_>> = Vec::new();
+ let mut statements: Vec<hir::Stmt<'_>> = 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(<pattern>: <ty>, <pattern>: <ty>, <pattern>: <ty>) {
+ // <body>
+ // }
+ //
+ // into:
+ //
+ // fn foo(__arg0: <ty>, __arg1: <ty>, __arg2: <ty>) {
+ // async move {
+ // let __arg2 = __arg2;
+ // let <pattern> = __arg2;
+ // let __arg1 = __arg1;
+ // let <pattern> = __arg1;
+ // let __arg0 = __arg0;
+ // let <pattern> = __arg0;
+ // drop-temps { <body> } // see comments later in fn for details
+ // }
+ // }
+ //
+ // If `<pattern>` is a simple ident, then it is lowered to a single
+ // `let <pattern> = <pattern>;` statement as an optimization.
+ //
+ // Note that the body is embedded in `drop-temps`; an
+ // equivalent desugaring would be `return { <body>
+ // };`. 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 <pat> = __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: <ty>` 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(&parameter.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 <pat> = <pat>;`. 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 <pat> = __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 <pat> = __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 { <user-body> }`, 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 { <user-body> }
+ // }
+ // ```
+ 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<NodeId>,
+ ) -> (&'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<T>(
+ &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<bool> = 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,
+ &param.kind,
+ &param.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<hir::WherePredicate<'hir>> {
+ // 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<Span>, 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),
+ })
+ }
+ }
+ }
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-06-12 06:23:07 +0000