1 use super::{AnonymousLifetimeMode, LoweringContext, ParamMode};
2 use super::{ImplTraitContext, ImplTraitPosition, ImplTraitTypeIdVisitor};
4 use rustc::arena::Arena;
6 use rustc_error_codes::*;
7 use rustc_errors::struct_span_err;
9 use rustc_hir::def::{DefKind, Res};
10 use rustc_hir::def_id::DefId;
11 use rustc_session::node_id::NodeMap;
12 use rustc_span::source_map::{respan, DesugaringKind};
13 use rustc_span::symbol::{kw, sym};
15 use rustc_target::spec::abi;
18 use syntax::visit::{self, Visitor};
21 use smallvec::{smallvec, SmallVec};
22 use std::collections::BTreeSet;
24 pub(super) struct ItemLowerer<'a, 'lowering, 'hir> {
25 pub(super) lctx: &'a mut LoweringContext<'lowering, 'hir>,
28 impl<'a, 'lowering, 'hir> ItemLowerer<'a, 'lowering, 'hir> {
29 fn with_trait_impl_ref<F>(&mut self, trait_impl_ref: &Option<TraitRef>, f: F)
33 let old = self.lctx.is_in_trait_impl;
34 self.lctx.is_in_trait_impl = if let &None = trait_impl_ref { false } else { true };
36 self.lctx.is_in_trait_impl = old;
40 impl<'a, 'lowering, 'hir> Visitor<'a> for ItemLowerer<'a, 'lowering, 'hir> {
41 fn visit_mod(&mut self, m: &'a Mod, _s: Span, _attrs: &[Attribute], n: NodeId) {
42 let hir_id = self.lctx.lower_node_id(n);
44 self.lctx.modules.insert(
47 items: BTreeSet::new(),
48 trait_items: BTreeSet::new(),
49 impl_items: BTreeSet::new(),
53 let old = self.lctx.current_module;
54 self.lctx.current_module = hir_id;
55 visit::walk_mod(self, m);
56 self.lctx.current_module = old;
59 fn visit_item(&mut self, item: &'a Item) {
60 let mut item_hir_id = None;
61 self.lctx.with_hir_id_owner(item.id, |lctx| {
62 lctx.without_in_scope_lifetime_defs(|lctx| {
63 if let Some(hir_item) = lctx.lower_item(item) {
64 item_hir_id = Some(hir_item.hir_id);
65 lctx.insert_item(hir_item);
70 if let Some(hir_id) = item_hir_id {
71 self.lctx.with_parent_item_lifetime_defs(hir_id, |this| {
72 let this = &mut ItemLowerer { lctx: this };
73 if let ItemKind::Impl(.., ref opt_trait_ref, _, _) = item.kind {
74 if opt_trait_ref.as_ref().map(|tr| tr.constness.is_some()).unwrap_or(false) {
77 .span_err(item.span, "const trait impls are not yet implemented");
80 this.with_trait_impl_ref(opt_trait_ref, |this| visit::walk_item(this, item));
82 visit::walk_item(this, item);
88 fn visit_trait_item(&mut self, item: &'a AssocItem) {
89 self.lctx.with_hir_id_owner(item.id, |lctx| {
90 let hir_item = lctx.lower_trait_item(item);
91 let id = hir::TraitItemId { hir_id: hir_item.hir_id };
92 lctx.trait_items.insert(id, hir_item);
93 lctx.modules.get_mut(&lctx.current_module).unwrap().trait_items.insert(id);
96 visit::walk_trait_item(self, item);
99 fn visit_impl_item(&mut self, item: &'a AssocItem) {
100 self.lctx.with_hir_id_owner(item.id, |lctx| {
101 let hir_item = lctx.lower_impl_item(item);
102 let id = hir::ImplItemId { hir_id: hir_item.hir_id };
103 lctx.impl_items.insert(id, hir_item);
104 lctx.modules.get_mut(&lctx.current_module).unwrap().impl_items.insert(id);
106 visit::walk_impl_item(self, item);
110 impl<'hir> LoweringContext<'_, 'hir> {
111 // Same as the method above, but accepts `hir::GenericParam`s
112 // instead of `ast::GenericParam`s.
113 // This should only be used with generics that have already had their
114 // in-band lifetimes added. In practice, this means that this function is
115 // only used when lowering a child item of a trait or impl.
116 fn with_parent_item_lifetime_defs<T>(
118 parent_hir_id: hir::HirId,
119 f: impl FnOnce(&mut LoweringContext<'_, '_>) -> T,
121 let old_len = self.in_scope_lifetimes.len();
123 let parent_generics = match self.items.get(&parent_hir_id).unwrap().kind {
124 hir::ItemKind::Impl(_, _, _, ref generics, ..)
125 | hir::ItemKind::Trait(_, _, ref generics, ..) => &generics.params[..],
128 let lt_def_names = parent_generics.iter().filter_map(|param| match param.kind {
129 hir::GenericParamKind::Lifetime { .. } => Some(param.name.modern()),
132 self.in_scope_lifetimes.extend(lt_def_names);
136 self.in_scope_lifetimes.truncate(old_len);
140 // Clears (and restores) the `in_scope_lifetimes` field. Used when
141 // visiting nested items, which never inherit in-scope lifetimes
142 // from their surrounding environment.
143 fn without_in_scope_lifetime_defs<T>(
145 f: impl FnOnce(&mut LoweringContext<'_, '_>) -> T,
147 let old_in_scope_lifetimes = std::mem::replace(&mut self.in_scope_lifetimes, vec![]);
149 // this vector is only used when walking over impl headers,
150 // input types, and the like, and should not be non-empty in
152 assert!(self.lifetimes_to_define.is_empty());
156 assert!(self.in_scope_lifetimes.is_empty());
157 self.in_scope_lifetimes = old_in_scope_lifetimes;
162 pub(super) fn lower_mod(&mut self, m: &Mod) -> hir::Mod<'hir> {
167 .alloc_from_iter(m.items.iter().flat_map(|x| self.lower_item_id(x))),
171 pub(super) fn lower_item_id(&mut self, i: &Item) -> SmallVec<[hir::ItemId; 1]> {
172 let node_ids = match i.kind {
173 ItemKind::Use(ref use_tree) => {
174 let mut vec = smallvec![i.id];
175 self.lower_item_id_use_tree(use_tree, i.id, &mut vec);
178 ItemKind::MacroDef(..) => SmallVec::new(),
179 ItemKind::Fn(..) | ItemKind::Impl(.., None, _, _) => smallvec![i.id],
180 ItemKind::Static(ref ty, ..) => {
181 let mut ids = smallvec![i.id];
182 if self.sess.features_untracked().impl_trait_in_bindings {
183 let mut visitor = ImplTraitTypeIdVisitor { ids: &mut ids };
184 visitor.visit_ty(ty);
188 ItemKind::Const(ref ty, ..) => {
189 let mut ids = smallvec![i.id];
190 if self.sess.features_untracked().impl_trait_in_bindings {
191 let mut visitor = ImplTraitTypeIdVisitor { ids: &mut ids };
192 visitor.visit_ty(ty);
196 _ => smallvec![i.id],
201 .map(|node_id| hir::ItemId { id: self.allocate_hir_id_counter(node_id) })
205 fn lower_item_id_use_tree(
209 vec: &mut SmallVec<[NodeId; 1]>,
212 UseTreeKind::Nested(ref nested_vec) => {
213 for &(ref nested, id) in nested_vec {
215 self.lower_item_id_use_tree(nested, id, vec);
218 UseTreeKind::Glob => {}
219 UseTreeKind::Simple(_, id1, id2) => {
221 self.expect_full_res_from_use(base_id).skip(1).zip([id1, id2].iter())
229 pub fn lower_item(&mut self, i: &Item) -> Option<hir::Item<'hir>> {
230 let mut ident = i.ident;
231 let mut vis = self.lower_visibility(&i.vis, None);
232 let attrs = self.lower_attrs(&i.attrs);
234 if let ItemKind::MacroDef(ref def) = i.kind {
235 if !def.legacy || attr::contains_name(&i.attrs, sym::macro_export) {
236 let body = self.lower_token_stream(def.body.inner_tokens());
237 let hir_id = self.lower_node_id(i.id);
238 self.exported_macros.push(hir::MacroDef {
248 self.non_exported_macro_attrs.extend(attrs.iter().cloned());
253 let kind = self.lower_item_kind(i.span, i.id, &mut ident, attrs, &mut vis, &i.kind);
255 Some(hir::Item { hir_id: self.lower_node_id(i.id), ident, attrs, kind, vis, span: i.span })
263 attrs: &'hir [Attribute],
264 vis: &mut hir::Visibility<'hir>,
266 ) -> hir::ItemKind<'hir> {
268 ItemKind::ExternCrate(orig_name) => hir::ItemKind::ExternCrate(orig_name),
269 ItemKind::Use(ref use_tree) => {
270 // Start with an empty prefix.
271 let prefix = Path { segments: vec![], span: use_tree.span };
273 self.lower_use_tree(use_tree, &prefix, id, vis, ident, attrs)
275 ItemKind::Static(ref t, m, ref e) => {
276 let ty = self.lower_ty(
278 if self.sess.features_untracked().impl_trait_in_bindings {
279 ImplTraitContext::OpaqueTy(None)
281 ImplTraitContext::Disallowed(ImplTraitPosition::Binding)
284 hir::ItemKind::Static(ty, m, self.lower_const_body(span, Some(e)))
286 ItemKind::Const(ref t, ref e) => {
287 let ty = self.lower_ty(
289 if self.sess.features_untracked().impl_trait_in_bindings {
290 ImplTraitContext::OpaqueTy(None)
292 ImplTraitContext::Disallowed(ImplTraitPosition::Binding)
295 hir::ItemKind::Const(ty, self.lower_const_body(span, Some(e)))
297 ItemKind::Fn(FnSig { ref decl, header }, ref generics, ref body) => {
298 let fn_def_id = self.resolver.definitions().local_def_id(id);
299 self.with_new_scopes(|this| {
300 this.current_item = Some(ident.span);
302 // Note: we don't need to change the return type from `T` to
303 // `impl Future<Output = T>` here because lower_body
304 // only cares about the input argument patterns in the function
305 // declaration (decl), not the return types.
307 this.lower_maybe_async_body(span, &decl, header.asyncness.node, Some(body));
309 let (generics, decl) = this.add_in_band_defs(
312 AnonymousLifetimeMode::PassThrough,
316 Some((fn_def_id, idty)),
318 header.asyncness.node.opt_return_id(),
322 let sig = hir::FnSig { decl, header: this.lower_fn_header(header) };
323 hir::ItemKind::Fn(sig, generics, body_id)
326 ItemKind::Mod(ref m) => hir::ItemKind::Mod(self.lower_mod(m)),
327 ItemKind::ForeignMod(ref nm) => hir::ItemKind::ForeignMod(self.lower_foreign_mod(nm)),
328 ItemKind::GlobalAsm(ref ga) => hir::ItemKind::GlobalAsm(self.lower_global_asm(ga)),
329 ItemKind::TyAlias(ref ty, ref generics) => match ty.kind.opaque_top_hack() {
331 let ty = self.lower_ty(ty, ImplTraitContext::disallowed());
332 let generics = self.lower_generics(generics, ImplTraitContext::disallowed());
333 hir::ItemKind::TyAlias(ty, generics)
336 let ty = hir::OpaqueTy {
337 generics: self.lower_generics(generics, ImplTraitContext::OpaqueTy(None)),
338 bounds: self.lower_param_bounds(bounds, ImplTraitContext::OpaqueTy(None)),
340 origin: hir::OpaqueTyOrigin::TypeAlias,
342 hir::ItemKind::OpaqueTy(ty)
345 ItemKind::Enum(ref enum_definition, ref generics) => hir::ItemKind::Enum(
347 variants: self.arena.alloc_from_iter(
348 enum_definition.variants.iter().map(|x| self.lower_variant(x)),
351 self.lower_generics(generics, ImplTraitContext::disallowed()),
353 ItemKind::Struct(ref struct_def, ref generics) => {
354 let struct_def = self.lower_variant_data(struct_def);
355 hir::ItemKind::Struct(
357 self.lower_generics(generics, ImplTraitContext::disallowed()),
360 ItemKind::Union(ref vdata, ref generics) => {
361 let vdata = self.lower_variant_data(vdata);
362 hir::ItemKind::Union(
364 self.lower_generics(generics, ImplTraitContext::disallowed()),
376 let def_id = self.resolver.definitions().local_def_id(id);
378 // Lower the "impl header" first. This ordering is important
379 // for in-band lifetimes! Consider `'a` here:
381 // impl Foo<'a> for u32 {
382 // fn method(&'a self) { .. }
385 // Because we start by lowering the `Foo<'a> for u32`
386 // part, we will add `'a` to the list of generics on
387 // the impl. When we then encounter it later in the
388 // method, it will not be considered an in-band
389 // lifetime to be added, but rather a reference to a
391 let lowered_trait_impl_id = self.lower_node_id(id);
392 let (generics, (trait_ref, lowered_ty)) = self.add_in_band_defs(
395 AnonymousLifetimeMode::CreateParameter,
397 let trait_ref = trait_ref.as_ref().map(|trait_ref| {
398 this.lower_trait_ref(trait_ref, ImplTraitContext::disallowed())
401 if let Some(ref trait_ref) = trait_ref {
402 if let Res::Def(DefKind::Trait, def_id) = trait_ref.path.res {
406 .push(lowered_trait_impl_id);
410 let lowered_ty = this.lower_ty(ty, ImplTraitContext::disallowed());
412 (trait_ref, lowered_ty)
417 self.with_in_scope_lifetime_defs(&ast_generics.params, |this| {
418 this.arena.alloc_from_iter(
419 impl_items.iter().map(|item| this.lower_impl_item_ref(item)),
426 self.lower_defaultness(defaultness, true /* [1] */),
433 ItemKind::Trait(is_auto, unsafety, ref generics, ref bounds, ref items) => {
434 let bounds = self.lower_param_bounds(bounds, ImplTraitContext::disallowed());
437 .alloc_from_iter(items.iter().map(|item| self.lower_trait_item_ref(item)));
438 hir::ItemKind::Trait(
441 self.lower_generics(generics, ImplTraitContext::disallowed()),
446 ItemKind::TraitAlias(ref generics, ref bounds) => hir::ItemKind::TraitAlias(
447 self.lower_generics(generics, ImplTraitContext::disallowed()),
448 self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
450 ItemKind::MacroDef(..) | ItemKind::Mac(..) => {
451 bug!("`TyMac` should have been expanded by now")
455 // [1] `defaultness.has_value()` is never called for an `impl`, always `true` in order to
456 // not cause an assertion failure inside the `lower_defaultness` function.
464 vis: &mut hir::Visibility<'hir>,
466 attrs: &'hir [Attribute],
467 ) -> hir::ItemKind<'hir> {
468 debug!("lower_use_tree(tree={:?})", tree);
469 debug!("lower_use_tree: vis = {:?}", vis);
471 let path = &tree.prefix;
472 let segments = prefix.segments.iter().chain(path.segments.iter()).cloned().collect();
475 UseTreeKind::Simple(rename, id1, id2) => {
476 *ident = tree.ident();
478 // First, apply the prefix to the path.
479 let mut path = Path { segments, span: path.span };
481 // Correctly resolve `self` imports.
482 if path.segments.len() > 1
483 && path.segments.last().unwrap().ident.name == kw::SelfLower
485 let _ = path.segments.pop();
486 if rename.is_none() {
487 *ident = path.segments.last().unwrap().ident;
491 let mut resolutions = self.expect_full_res_from_use(id);
492 // We want to return *something* from this function, so hold onto the first item
494 let ret_res = self.lower_res(resolutions.next().unwrap_or(Res::Err));
496 // Here, we are looping over namespaces, if they exist for the definition
497 // being imported. We only handle type and value namespaces because we
498 // won't be dealing with macros in the rest of the compiler.
499 // Essentially a single `use` which imports two names is desugared into
501 for (res, &new_node_id) in resolutions.zip([id1, id2].iter()) {
503 let mut path = path.clone();
504 for seg in &mut path.segments {
505 seg.id = self.resolver.next_node_id();
507 let span = path.span;
509 self.with_hir_id_owner(new_node_id, |this| {
510 let new_id = this.lower_node_id(new_node_id);
511 let res = this.lower_res(res);
512 let path = this.lower_path_extra(res, &path, ParamMode::Explicit, None);
513 let kind = hir::ItemKind::Use(path, hir::UseKind::Single);
514 let vis = this.rebuild_vis(&vis);
516 this.insert_item(hir::Item {
527 let path = self.lower_path_extra(ret_res, &path, ParamMode::Explicit, None);
528 hir::ItemKind::Use(path, hir::UseKind::Single)
530 UseTreeKind::Glob => {
532 self.lower_path(id, &Path { segments, span: path.span }, ParamMode::Explicit);
533 hir::ItemKind::Use(path, hir::UseKind::Glob)
535 UseTreeKind::Nested(ref trees) => {
536 // Nested imports are desugared into simple imports.
537 // So, if we start with
540 // pub(x) use foo::{a, b};
543 // we will create three items:
546 // pub(x) use foo::a;
547 // pub(x) use foo::b;
548 // pub(x) use foo::{}; // <-- this is called the `ListStem`
551 // The first two are produced by recursively invoking
552 // `lower_use_tree` (and indeed there may be things
553 // like `use foo::{a::{b, c}}` and so forth). They
554 // wind up being directly added to
555 // `self.items`. However, the structure of this
556 // function also requires us to return one item, and
557 // for that we return the `{}` import (called the
560 let prefix = Path { segments, span: prefix.span.to(path.span) };
562 // Add all the nested `PathListItem`s to the HIR.
563 for &(ref use_tree, id) in trees {
564 let new_hir_id = self.lower_node_id(id);
566 let mut prefix = prefix.clone();
568 // Give the segments new node-ids since they are being cloned.
569 for seg in &mut prefix.segments {
570 seg.id = self.resolver.next_node_id();
573 // Each `use` import is an item and thus are owners of the
574 // names in the path. Up to this point the nested import is
575 // the current owner, since we want each desugared import to
576 // own its own names, we have to adjust the owner before
577 // lowering the rest of the import.
578 self.with_hir_id_owner(id, |this| {
579 let mut vis = this.rebuild_vis(&vis);
580 let mut ident = *ident;
583 this.lower_use_tree(use_tree, &prefix, id, &mut vis, &mut ident, attrs);
585 this.insert_item(hir::Item {
596 // Subtle and a bit hacky: we lower the privacy level
597 // of the list stem to "private" most of the time, but
598 // not for "restricted" paths. The key thing is that
599 // we don't want it to stay as `pub` (with no caveats)
600 // because that affects rustdoc and also the lints
601 // about `pub` items. But we can't *always* make it
602 // private -- particularly not for restricted paths --
603 // because it contains node-ids that would then be
604 // unused, failing the check that HirIds are "densely
607 hir::VisibilityKind::Public
608 | hir::VisibilityKind::Crate(_)
609 | hir::VisibilityKind::Inherited => {
610 *vis = respan(prefix.span.shrink_to_lo(), hir::VisibilityKind::Inherited);
612 hir::VisibilityKind::Restricted { .. } => {
613 // Do nothing here, as described in the comment on the match.
617 let res = self.expect_full_res_from_use(id).next().unwrap_or(Res::Err);
618 let res = self.lower_res(res);
619 let path = self.lower_path_extra(res, &prefix, ParamMode::Explicit, None);
620 hir::ItemKind::Use(path, hir::UseKind::ListStem)
625 /// Paths like the visibility path in `pub(super) use foo::{bar, baz}` are repeated
626 /// many times in the HIR tree; for each occurrence, we need to assign distinct
627 /// `NodeId`s. (See, e.g., #56128.)
628 fn rebuild_use_path(&mut self, path: &hir::Path<'hir>) -> &'hir hir::Path<'hir> {
629 debug!("rebuild_use_path(path = {:?})", path);
631 self.arena.alloc_from_iter(path.segments.iter().map(|seg| hir::PathSegment {
633 hir_id: seg.hir_id.map(|_| self.next_id()),
636 infer_args: seg.infer_args,
638 self.arena.alloc(hir::Path { span: path.span, res: path.res, segments })
641 fn rebuild_vis(&mut self, vis: &hir::Visibility<'hir>) -> hir::Visibility<'hir> {
642 let vis_kind = match vis.node {
643 hir::VisibilityKind::Public => hir::VisibilityKind::Public,
644 hir::VisibilityKind::Crate(sugar) => hir::VisibilityKind::Crate(sugar),
645 hir::VisibilityKind::Inherited => hir::VisibilityKind::Inherited,
646 hir::VisibilityKind::Restricted { ref path, hir_id: _ } => {
647 hir::VisibilityKind::Restricted {
648 path: self.rebuild_use_path(path),
649 hir_id: self.next_id(),
653 respan(vis.span, vis_kind)
656 fn lower_foreign_item(&mut self, i: &ForeignItem) -> hir::ForeignItem<'hir> {
657 let def_id = self.resolver.definitions().local_def_id(i.id);
659 hir_id: self.lower_node_id(i.id),
661 attrs: self.lower_attrs(&i.attrs),
663 ForeignItemKind::Fn(ref fdec, ref generics) => {
664 let (generics, (fn_dec, fn_args)) = self.add_in_band_defs(
667 AnonymousLifetimeMode::PassThrough,
670 // Disallow `impl Trait` in foreign items.
671 this.lower_fn_decl(fdec, None, false, None),
672 this.lower_fn_params_to_names(fdec),
677 hir::ForeignItemKind::Fn(fn_dec, fn_args, generics)
679 ForeignItemKind::Static(ref t, m) => {
680 let ty = self.lower_ty(t, ImplTraitContext::disallowed());
681 hir::ForeignItemKind::Static(ty, m)
683 ForeignItemKind::Ty => hir::ForeignItemKind::Type,
684 ForeignItemKind::Macro(_) => panic!("macro shouldn't exist here"),
686 vis: self.lower_visibility(&i.vis, None),
691 fn lower_foreign_mod(&mut self, fm: &ForeignMod) -> hir::ForeignMod<'hir> {
693 abi: fm.abi.map_or(abi::Abi::C, |abi| self.lower_abi(abi)),
694 items: self.arena.alloc_from_iter(fm.items.iter().map(|x| self.lower_foreign_item(x))),
698 fn lower_global_asm(&mut self, ga: &GlobalAsm) -> &'hir hir::GlobalAsm {
699 self.arena.alloc(hir::GlobalAsm { asm: ga.asm })
702 fn lower_variant(&mut self, v: &Variant) -> hir::Variant<'hir> {
704 attrs: self.lower_attrs(&v.attrs),
705 data: self.lower_variant_data(&v.data),
706 disr_expr: v.disr_expr.as_ref().map(|e| self.lower_anon_const(e)),
707 id: self.lower_node_id(v.id),
713 fn lower_variant_data(&mut self, vdata: &VariantData) -> hir::VariantData<'hir> {
715 VariantData::Struct(ref fields, recovered) => hir::VariantData::Struct(
717 .alloc_from_iter(fields.iter().enumerate().map(|f| self.lower_struct_field(f))),
720 VariantData::Tuple(ref fields, id) => hir::VariantData::Tuple(
722 .alloc_from_iter(fields.iter().enumerate().map(|f| self.lower_struct_field(f))),
723 self.lower_node_id(id),
725 VariantData::Unit(id) => hir::VariantData::Unit(self.lower_node_id(id)),
729 fn lower_struct_field(&mut self, (index, f): (usize, &StructField)) -> hir::StructField<'hir> {
730 let ty = if let TyKind::Path(ref qself, ref path) = f.ty.kind {
731 let t = self.lower_path_ty(
735 ParamMode::ExplicitNamed, // no `'_` in declarations (Issue #61124)
736 ImplTraitContext::disallowed(),
740 self.lower_ty(&f.ty, ImplTraitContext::disallowed())
744 hir_id: self.lower_node_id(f.id),
745 ident: match f.ident {
746 Some(ident) => ident,
747 // FIXME(jseyfried): positional field hygiene.
748 None => Ident::new(sym::integer(index), f.span),
750 vis: self.lower_visibility(&f.vis, None),
752 attrs: self.lower_attrs(&f.attrs),
756 fn lower_trait_item(&mut self, i: &AssocItem) -> hir::TraitItem<'hir> {
757 let trait_item_def_id = self.resolver.definitions().local_def_id(i.id);
759 let (generics, kind) = match i.kind {
760 AssocItemKind::Const(ref ty, ref default) => {
761 let generics = self.lower_generics(&i.generics, ImplTraitContext::disallowed());
762 let ty = self.lower_ty(ty, ImplTraitContext::disallowed());
765 hir::TraitItemKind::Const(
767 default.as_ref().map(|x| self.lower_const_body(i.span, Some(x))),
771 AssocItemKind::Fn(ref sig, None) => {
772 let names = self.lower_fn_params_to_names(&sig.decl);
773 let (generics, sig) =
774 self.lower_method_sig(&i.generics, sig, trait_item_def_id, false, None);
775 (generics, hir::TraitItemKind::Method(sig, hir::TraitMethod::Required(names)))
777 AssocItemKind::Fn(ref sig, Some(ref body)) => {
778 let body_id = self.lower_fn_body_block(i.span, &sig.decl, Some(body));
779 let (generics, sig) =
780 self.lower_method_sig(&i.generics, sig, trait_item_def_id, false, None);
781 (generics, hir::TraitItemKind::Method(sig, hir::TraitMethod::Provided(body_id)))
783 AssocItemKind::TyAlias(ref bounds, ref default) => {
784 let ty = default.as_ref().map(|x| self.lower_ty(x, ImplTraitContext::disallowed()));
785 let generics = self.lower_generics(&i.generics, ImplTraitContext::disallowed());
786 let kind = hir::TraitItemKind::Type(
787 self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
793 AssocItemKind::Macro(..) => bug!("macro item shouldn't exist at this point"),
797 hir_id: self.lower_node_id(i.id),
799 attrs: self.lower_attrs(&i.attrs),
806 fn lower_trait_item_ref(&mut self, i: &AssocItem) -> hir::TraitItemRef {
807 let (kind, has_default) = match i.kind {
808 AssocItemKind::Const(_, ref default) => (hir::AssocItemKind::Const, default.is_some()),
809 AssocItemKind::TyAlias(_, ref default) => (hir::AssocItemKind::Type, default.is_some()),
810 AssocItemKind::Fn(ref sig, ref default) => {
811 (hir::AssocItemKind::Method { has_self: sig.decl.has_self() }, default.is_some())
813 AssocItemKind::Macro(..) => unimplemented!(),
816 id: hir::TraitItemId { hir_id: self.lower_node_id(i.id) },
819 defaultness: self.lower_defaultness(Defaultness::Default, has_default),
824 /// Construct `ExprKind::Err` for the given `span`.
825 fn expr_err(&mut self, span: Span) -> hir::Expr<'hir> {
826 self.expr(span, hir::ExprKind::Err, AttrVec::new())
829 fn lower_impl_item(&mut self, i: &AssocItem) -> hir::ImplItem<'hir> {
830 let impl_item_def_id = self.resolver.definitions().local_def_id(i.id);
832 let (generics, kind) = match i.kind {
833 AssocItemKind::Const(ref ty, ref expr) => {
834 let generics = self.lower_generics(&i.generics, ImplTraitContext::disallowed());
835 let ty = self.lower_ty(ty, ImplTraitContext::disallowed());
838 hir::ImplItemKind::Const(ty, self.lower_const_body(i.span, expr.as_deref())),
841 AssocItemKind::Fn(ref sig, ref body) => {
842 self.current_item = Some(i.span);
843 let body_id = self.lower_maybe_async_body(
846 sig.header.asyncness.node,
849 let impl_trait_return_allow = !self.is_in_trait_impl;
850 let (generics, sig) = self.lower_method_sig(
854 impl_trait_return_allow,
855 sig.header.asyncness.node.opt_return_id(),
858 (generics, hir::ImplItemKind::Method(sig, body_id))
860 AssocItemKind::TyAlias(_, ref ty) => {
861 let generics = self.lower_generics(&i.generics, ImplTraitContext::disallowed());
862 let kind = match ty {
864 let ty = self.arena.alloc(self.ty(i.span, hir::TyKind::Err));
865 hir::ImplItemKind::TyAlias(ty)
867 Some(ty) => match ty.kind.opaque_top_hack() {
869 let ty = self.lower_ty(ty, ImplTraitContext::disallowed());
870 hir::ImplItemKind::TyAlias(ty)
873 let bs = self.lower_param_bounds(bs, ImplTraitContext::disallowed());
874 hir::ImplItemKind::OpaqueTy(bs)
880 AssocItemKind::Macro(..) => bug!("`TyMac` should have been expanded by now"),
884 hir_id: self.lower_node_id(i.id),
886 attrs: self.lower_attrs(&i.attrs),
888 vis: self.lower_visibility(&i.vis, None),
889 defaultness: self.lower_defaultness(i.defaultness, true /* [1] */),
894 // [1] since `default impl` is not yet implemented, this is always true in impls
897 fn lower_impl_item_ref(&mut self, i: &AssocItem) -> hir::ImplItemRef<'hir> {
899 id: hir::ImplItemId { hir_id: self.lower_node_id(i.id) },
902 vis: self.lower_visibility(&i.vis, Some(i.id)),
903 defaultness: self.lower_defaultness(i.defaultness, true /* [1] */),
904 kind: match &i.kind {
905 AssocItemKind::Const(..) => hir::AssocItemKind::Const,
906 AssocItemKind::TyAlias(_, ty) => {
907 match ty.as_deref().and_then(|ty| ty.kind.opaque_top_hack()) {
908 None => hir::AssocItemKind::Type,
909 Some(_) => hir::AssocItemKind::OpaqueTy,
912 AssocItemKind::Fn(sig, _) => {
913 hir::AssocItemKind::Method { has_self: sig.decl.has_self() }
915 AssocItemKind::Macro(..) => unimplemented!(),
919 // [1] since `default impl` is not yet implemented, this is always true in impls
922 /// If an `explicit_owner` is given, this method allocates the `HirId` in
923 /// the address space of that item instead of the item currently being
924 /// lowered. This can happen during `lower_impl_item_ref()` where we need to
925 /// lower a `Visibility` value although we haven't lowered the owning
926 /// `ImplItem` in question yet.
930 explicit_owner: Option<NodeId>,
931 ) -> hir::Visibility<'hir> {
932 let node = match v.node {
933 VisibilityKind::Public => hir::VisibilityKind::Public,
934 VisibilityKind::Crate(sugar) => hir::VisibilityKind::Crate(sugar),
935 VisibilityKind::Restricted { ref path, id } => {
936 debug!("lower_visibility: restricted path id = {:?}", id);
937 let lowered_id = if let Some(owner) = explicit_owner {
938 self.lower_node_id_with_owner(id, owner)
940 self.lower_node_id(id)
942 let res = self.expect_full_res(id);
943 let res = self.lower_res(res);
944 hir::VisibilityKind::Restricted {
945 path: self.lower_path_extra(res, path, ParamMode::Explicit, explicit_owner),
949 VisibilityKind::Inherited => hir::VisibilityKind::Inherited,
954 fn lower_defaultness(&self, d: Defaultness, has_value: bool) -> hir::Defaultness {
956 Defaultness::Default => hir::Defaultness::Default { has_value: has_value },
957 Defaultness::Final => {
959 hir::Defaultness::Final
966 params: &'hir [hir::Param<'hir>],
967 value: hir::Expr<'hir>,
969 let body = hir::Body { generator_kind: self.generator_kind, params, value };
971 self.bodies.insert(id, body);
977 f: impl FnOnce(&mut Self) -> (&'hir [hir::Param<'hir>], hir::Expr<'hir>),
979 let prev_gen_kind = self.generator_kind.take();
980 let (parameters, result) = f(self);
981 let body_id = self.record_body(parameters, result);
982 self.generator_kind = prev_gen_kind;
986 fn lower_param(&mut self, param: &Param) -> hir::Param<'hir> {
988 attrs: self.lower_attrs(¶m.attrs),
989 hir_id: self.lower_node_id(param.id),
990 pat: self.lower_pat(¶m.pat),
995 pub(super) fn lower_fn_body(
998 body: impl FnOnce(&mut Self) -> hir::Expr<'hir>,
1000 self.lower_body(|this| {
1002 this.arena.alloc_from_iter(decl.inputs.iter().map(|x| this.lower_param(x))),
1008 fn lower_fn_body_block(
1012 body: Option<&Block>,
1014 self.lower_fn_body(decl, |this| this.lower_block_expr_opt(span, body))
1017 fn lower_block_expr_opt(&mut self, span: Span, block: Option<&Block>) -> hir::Expr<'hir> {
1019 Some(block) => self.lower_block_expr(block),
1020 None => self.expr_err(span),
1024 pub(super) fn lower_const_body(&mut self, span: Span, expr: Option<&Expr>) -> hir::BodyId {
1025 self.lower_body(|this| {
1029 Some(expr) => this.lower_expr_mut(expr),
1030 None => this.expr_err(span),
1036 fn lower_maybe_async_body(
1041 body: Option<&Block>,
1043 let closure_id = match asyncness {
1044 IsAsync::Async { closure_id, .. } => closure_id,
1045 IsAsync::NotAsync => return self.lower_fn_body_block(span, decl, body),
1048 self.lower_body(|this| {
1049 let mut parameters: Vec<hir::Param<'_>> = Vec::new();
1050 let mut statements: Vec<hir::Stmt<'_>> = Vec::new();
1052 // Async function parameters are lowered into the closure body so that they are
1053 // captured and so that the drop order matches the equivalent non-async functions.
1057 // async fn foo(<pattern>: <ty>, <pattern>: <ty>, <pattern>: <ty>) {
1063 // fn foo(__arg0: <ty>, __arg1: <ty>, __arg2: <ty>) {
1065 // let __arg2 = __arg2;
1066 // let <pattern> = __arg2;
1067 // let __arg1 = __arg1;
1068 // let <pattern> = __arg1;
1069 // let __arg0 = __arg0;
1070 // let <pattern> = __arg0;
1071 // drop-temps { <body> } // see comments later in fn for details
1075 // If `<pattern>` is a simple ident, then it is lowered to a single
1076 // `let <pattern> = <pattern>;` statement as an optimization.
1078 // Note that the body is embedded in `drop-temps`; an
1079 // equivalent desugaring would be `return { <body>
1080 // };`. The key point is that we wish to drop all the
1081 // let-bound variables and temporaries created in the body
1082 // (and its tail expression!) before we drop the
1083 // parameters (c.f. rust-lang/rust#64512).
1084 for (index, parameter) in decl.inputs.iter().enumerate() {
1085 let parameter = this.lower_param(parameter);
1086 let span = parameter.pat.span;
1088 // Check if this is a binding pattern, if so, we can optimize and avoid adding a
1089 // `let <pat> = __argN;` statement. In this case, we do not rename the parameter.
1090 let (ident, is_simple_parameter) = match parameter.pat.kind {
1091 hir::PatKind::Binding(hir::BindingAnnotation::Unannotated, _, ident, _) => {
1095 // Replace the ident for bindings that aren't simple.
1096 let name = format!("__arg{}", index);
1097 let ident = Ident::from_str(&name);
1103 let desugared_span = this.mark_span_with_reason(DesugaringKind::Async, span, None);
1105 // Construct a parameter representing `__argN: <ty>` to replace the parameter of the
1108 // If this is the simple case, this parameter will end up being the same as the
1109 // original parameter, but with a different pattern id.
1110 let mut stmt_attrs = AttrVec::new();
1111 stmt_attrs.extend(parameter.attrs.iter().cloned());
1112 let (new_parameter_pat, new_parameter_id) = this.pat_ident(desugared_span, ident);
1113 let new_parameter = hir::Param {
1114 attrs: parameter.attrs,
1115 hir_id: parameter.hir_id,
1116 pat: new_parameter_pat,
1117 span: parameter.span,
1120 if is_simple_parameter {
1121 // If this is the simple case, then we only insert one statement that is
1122 // `let <pat> = <pat>;`. We re-use the original argument's pattern so that
1123 // `HirId`s are densely assigned.
1124 let expr = this.expr_ident(desugared_span, ident, new_parameter_id);
1125 let stmt = this.stmt_let_pat(
1130 hir::LocalSource::AsyncFn,
1132 statements.push(stmt);
1134 // If this is not the simple case, then we construct two statements:
1137 // let __argN = __argN;
1138 // let <pat> = __argN;
1141 // The first statement moves the parameter into the closure and thus ensures
1142 // that the drop order is correct.
1144 // The second statement creates the bindings that the user wrote.
1146 // Construct the `let mut __argN = __argN;` statement. It must be a mut binding
1147 // because the user may have specified a `ref mut` binding in the next
1149 let (move_pat, move_id) = this.pat_ident_binding_mode(
1152 hir::BindingAnnotation::Mutable,
1154 let move_expr = this.expr_ident(desugared_span, ident, new_parameter_id);
1155 let move_stmt = this.stmt_let_pat(
1160 hir::LocalSource::AsyncFn,
1163 // Construct the `let <pat> = __argN;` statement. We re-use the original
1164 // parameter's pattern so that `HirId`s are densely assigned.
1165 let pattern_expr = this.expr_ident(desugared_span, ident, move_id);
1166 let pattern_stmt = this.stmt_let_pat(
1171 hir::LocalSource::AsyncFn,
1174 statements.push(move_stmt);
1175 statements.push(pattern_stmt);
1178 parameters.push(new_parameter);
1181 let body_span = body.map_or(span, |b| b.span);
1182 let async_expr = this.make_async_expr(
1187 hir::AsyncGeneratorKind::Fn,
1189 // Create a block from the user's function body:
1190 let user_body = this.lower_block_expr_opt(body_span, body);
1192 // Transform into `drop-temps { <user-body> }`, an expression:
1193 let desugared_span =
1194 this.mark_span_with_reason(DesugaringKind::Async, user_body.span, None);
1195 let user_body = this.expr_drop_temps(
1197 this.arena.alloc(user_body),
1201 // As noted above, create the final block like
1205 // let $param_pattern = $raw_param;
1207 // drop-temps { <user-body> }
1210 let body = this.block_all(
1212 this.arena.alloc_from_iter(statements),
1216 this.expr_block(body, AttrVec::new())
1221 this.arena.alloc_from_iter(parameters),
1222 this.expr(body_span, async_expr, AttrVec::new()),
1227 fn lower_method_sig(
1229 generics: &Generics,
1232 impl_trait_return_allow: bool,
1233 is_async: Option<NodeId>,
1234 ) -> (hir::Generics<'hir>, hir::FnSig<'hir>) {
1235 let header = self.lower_fn_header(sig.header);
1236 let (generics, decl) = self.add_in_band_defs(
1239 AnonymousLifetimeMode::PassThrough,
1243 Some((fn_def_id, idty)),
1244 impl_trait_return_allow,
1249 (generics, hir::FnSig { header, decl })
1252 fn lower_fn_header(&mut self, h: FnHeader) -> hir::FnHeader {
1254 unsafety: h.unsafety,
1255 asyncness: self.lower_asyncness(h.asyncness.node),
1256 constness: h.constness.node,
1257 abi: self.lower_extern(h.ext),
1261 pub(super) fn lower_abi(&mut self, abi: StrLit) -> abi::Abi {
1262 abi::lookup(&abi.symbol_unescaped.as_str()).unwrap_or_else(|| {
1263 self.error_on_invalid_abi(abi);
1268 pub(super) fn lower_extern(&mut self, ext: Extern) -> abi::Abi {
1270 Extern::None => abi::Abi::Rust,
1271 Extern::Implicit => abi::Abi::C,
1272 Extern::Explicit(abi) => self.lower_abi(abi),
1276 fn error_on_invalid_abi(&self, abi: StrLit) {
1277 struct_span_err!(self.sess, abi.span, E0703, "invalid ABI: found `{}`", abi.symbol)
1278 .span_label(abi.span, "invalid ABI")
1279 .help(&format!("valid ABIs: {}", abi::all_names().join(", ")))
1283 fn lower_asyncness(&mut self, a: IsAsync) -> hir::IsAsync {
1285 IsAsync::Async { .. } => hir::IsAsync::Async,
1286 IsAsync::NotAsync => hir::IsAsync::NotAsync,
1290 pub(super) fn lower_generics_mut(
1292 generics: &Generics,
1293 itctx: ImplTraitContext<'_, 'hir>,
1294 ) -> GenericsCtor<'hir> {
1295 // Collect `?Trait` bounds in where clause and move them to parameter definitions.
1296 // FIXME: this could probably be done with less rightward drift. It also looks like two
1297 // control paths where `report_error` is called are the only paths that advance to after the
1298 // match statement, so the error reporting could probably just be moved there.
1299 let mut add_bounds: NodeMap<Vec<_>> = Default::default();
1300 for pred in &generics.where_clause.predicates {
1301 if let WherePredicate::BoundPredicate(ref bound_pred) = *pred {
1302 'next_bound: for bound in &bound_pred.bounds {
1303 if let GenericBound::Trait(_, TraitBoundModifier::Maybe) = *bound {
1304 let report_error = |this: &mut Self| {
1305 this.diagnostic().span_err(
1306 bound_pred.bounded_ty.span,
1307 "`?Trait` bounds are only permitted at the \
1308 point where a type parameter is declared",
1311 // Check if the where clause type is a plain type parameter.
1312 match bound_pred.bounded_ty.kind {
1313 TyKind::Path(None, ref path)
1314 if path.segments.len() == 1
1315 && bound_pred.bound_generic_params.is_empty() =>
1317 if let Some(Res::Def(DefKind::TyParam, def_id)) = self
1319 .get_partial_res(bound_pred.bounded_ty.id)
1320 .map(|d| d.base_res())
1322 if let Some(node_id) =
1323 self.resolver.definitions().as_local_node_id(def_id)
1325 for param in &generics.params {
1327 GenericParamKind::Type { .. } => {
1328 if node_id == param.id {
1332 .push(bound.clone());
1333 continue 'next_bound;
1343 _ => report_error(self),
1351 params: self.lower_generic_params_mut(&generics.params, &add_bounds, itctx).collect(),
1352 where_clause: self.lower_where_clause(&generics.where_clause),
1353 span: generics.span,
1357 pub(super) fn lower_generics(
1359 generics: &Generics,
1360 itctx: ImplTraitContext<'_, 'hir>,
1361 ) -> hir::Generics<'hir> {
1362 let generics_ctor = self.lower_generics_mut(generics, itctx);
1363 generics_ctor.into_generics(self.arena)
1366 fn lower_where_clause(&mut self, wc: &WhereClause) -> hir::WhereClause<'hir> {
1367 self.with_anonymous_lifetime_mode(AnonymousLifetimeMode::ReportError, |this| {
1369 predicates: this.arena.alloc_from_iter(
1370 wc.predicates.iter().map(|predicate| this.lower_where_predicate(predicate)),
1377 fn lower_where_predicate(&mut self, pred: &WherePredicate) -> hir::WherePredicate<'hir> {
1379 WherePredicate::BoundPredicate(WhereBoundPredicate {
1380 ref bound_generic_params,
1385 self.with_in_scope_lifetime_defs(&bound_generic_params, |this| {
1386 hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
1387 bound_generic_params: this.lower_generic_params(
1388 bound_generic_params,
1389 &NodeMap::default(),
1390 ImplTraitContext::disallowed(),
1392 bounded_ty: this.lower_ty(bounded_ty, ImplTraitContext::disallowed()),
1393 bounds: this.arena.alloc_from_iter(bounds.iter().filter_map(|bound| {
1395 // Ignore `?Trait` bounds.
1396 // They were copied into type parameters already.
1397 GenericBound::Trait(_, TraitBoundModifier::Maybe) => None,
1399 this.lower_param_bound(bound, ImplTraitContext::disallowed()),
1407 WherePredicate::RegionPredicate(WhereRegionPredicate {
1411 }) => hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate {
1413 lifetime: self.lower_lifetime(lifetime),
1414 bounds: self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
1416 WherePredicate::EqPredicate(WhereEqPredicate { id, ref lhs_ty, ref rhs_ty, span }) => {
1417 hir::WherePredicate::EqPredicate(hir::WhereEqPredicate {
1418 hir_id: self.lower_node_id(id),
1419 lhs_ty: self.lower_ty(lhs_ty, ImplTraitContext::disallowed()),
1420 rhs_ty: self.lower_ty(rhs_ty, ImplTraitContext::disallowed()),
1428 /// Helper struct for delayed construction of Generics.
1429 pub(super) struct GenericsCtor<'hir> {
1430 pub(super) params: SmallVec<[hir::GenericParam<'hir>; 4]>,
1431 where_clause: hir::WhereClause<'hir>,
1435 impl<'hir> GenericsCtor<'hir> {
1436 pub(super) fn into_generics(self, arena: &'hir Arena<'hir>) -> hir::Generics<'hir> {
1438 params: arena.alloc_from_iter(self.params),
1439 where_clause: self.where_clause,