1 use super::{AnonymousLifetimeMode, LoweringContext, ParamMode};
2 use super::{ImplTraitContext, ImplTraitPosition, ImplTraitTypeIdVisitor};
4 use rustc::arena::Arena;
6 use rustc_errors::struct_span_err;
8 use rustc_hir::def::{DefKind, Res};
9 use rustc_hir::def_id::DefId;
10 use rustc_session::node_id::NodeMap;
11 use rustc_span::source_map::{respan, DesugaringKind};
12 use rustc_span::symbol::{kw, sym};
14 use rustc_target::spec::abi;
17 use syntax::visit::{self, Visitor};
20 use smallvec::{smallvec, SmallVec};
21 use std::collections::BTreeSet;
23 pub(super) struct ItemLowerer<'a, 'lowering, 'hir> {
24 pub(super) lctx: &'a mut LoweringContext<'lowering, 'hir>,
27 impl ItemLowerer<'_, '_, '_> {
28 fn with_trait_impl_ref(&mut self, impl_ref: &Option<TraitRef>, f: impl FnOnce(&mut Self)) {
29 let old = self.lctx.is_in_trait_impl;
30 self.lctx.is_in_trait_impl = if let &None = impl_ref { false } else { true };
32 self.lctx.is_in_trait_impl = old;
36 impl<'a> Visitor<'a> for ItemLowerer<'a, '_, '_> {
37 fn visit_mod(&mut self, m: &'a Mod, _s: Span, _attrs: &[Attribute], n: NodeId) {
38 let hir_id = self.lctx.lower_node_id(n);
40 self.lctx.modules.insert(
43 items: BTreeSet::new(),
44 trait_items: BTreeSet::new(),
45 impl_items: BTreeSet::new(),
49 let old = self.lctx.current_module;
50 self.lctx.current_module = hir_id;
51 visit::walk_mod(self, m);
52 self.lctx.current_module = old;
55 fn visit_item(&mut self, item: &'a Item) {
56 let mut item_hir_id = None;
57 self.lctx.with_hir_id_owner(item.id, |lctx| {
58 lctx.without_in_scope_lifetime_defs(|lctx| {
59 if let Some(hir_item) = lctx.lower_item(item) {
60 item_hir_id = Some(hir_item.hir_id);
61 lctx.insert_item(hir_item);
66 if let Some(hir_id) = item_hir_id {
67 self.lctx.with_parent_item_lifetime_defs(hir_id, |this| {
68 let this = &mut ItemLowerer { lctx: this };
69 if let ItemKind::Impl { constness, ref of_trait, .. } = item.kind {
70 if constness == Constness::Const {
73 .span_err(item.span, "const trait impls are not yet implemented");
76 this.with_trait_impl_ref(of_trait, |this| visit::walk_item(this, item));
78 visit::walk_item(this, item);
84 fn visit_trait_item(&mut self, item: &'a AssocItem) {
85 self.lctx.with_hir_id_owner(item.id, |lctx| {
86 let hir_item = lctx.lower_trait_item(item);
87 let id = hir::TraitItemId { hir_id: hir_item.hir_id };
88 lctx.trait_items.insert(id, hir_item);
89 lctx.modules.get_mut(&lctx.current_module).unwrap().trait_items.insert(id);
92 visit::walk_trait_item(self, item);
95 fn visit_impl_item(&mut self, item: &'a AssocItem) {
96 self.lctx.with_hir_id_owner(item.id, |lctx| {
97 let hir_item = lctx.lower_impl_item(item);
98 let id = hir::ImplItemId { hir_id: hir_item.hir_id };
99 lctx.impl_items.insert(id, hir_item);
100 lctx.modules.get_mut(&lctx.current_module).unwrap().impl_items.insert(id);
102 visit::walk_impl_item(self, item);
106 impl<'hir> LoweringContext<'_, 'hir> {
107 // Same as the method above, but accepts `hir::GenericParam`s
108 // instead of `ast::GenericParam`s.
109 // This should only be used with generics that have already had their
110 // in-band lifetimes added. In practice, this means that this function is
111 // only used when lowering a child item of a trait or impl.
112 fn with_parent_item_lifetime_defs<T>(
114 parent_hir_id: hir::HirId,
115 f: impl FnOnce(&mut LoweringContext<'_, '_>) -> T,
117 let old_len = self.in_scope_lifetimes.len();
119 let parent_generics = match self.items.get(&parent_hir_id).unwrap().kind {
120 hir::ItemKind::Impl { ref generics, .. }
121 | hir::ItemKind::Trait(_, _, ref generics, ..) => &generics.params[..],
124 let lt_def_names = parent_generics.iter().filter_map(|param| match param.kind {
125 hir::GenericParamKind::Lifetime { .. } => Some(param.name.modern()),
128 self.in_scope_lifetimes.extend(lt_def_names);
132 self.in_scope_lifetimes.truncate(old_len);
136 // Clears (and restores) the `in_scope_lifetimes` field. Used when
137 // visiting nested items, which never inherit in-scope lifetimes
138 // from their surrounding environment.
139 fn without_in_scope_lifetime_defs<T>(
141 f: impl FnOnce(&mut LoweringContext<'_, '_>) -> T,
143 let old_in_scope_lifetimes = std::mem::replace(&mut self.in_scope_lifetimes, vec![]);
145 // this vector is only used when walking over impl headers,
146 // input types, and the like, and should not be non-empty in
148 assert!(self.lifetimes_to_define.is_empty());
152 assert!(self.in_scope_lifetimes.is_empty());
153 self.in_scope_lifetimes = old_in_scope_lifetimes;
158 pub(super) fn lower_mod(&mut self, m: &Mod) -> hir::Mod<'hir> {
163 .alloc_from_iter(m.items.iter().flat_map(|x| self.lower_item_id(x))),
167 pub(super) fn lower_item_id(&mut self, i: &Item) -> SmallVec<[hir::ItemId; 1]> {
168 let node_ids = match i.kind {
169 ItemKind::Use(ref use_tree) => {
170 let mut vec = smallvec![i.id];
171 self.lower_item_id_use_tree(use_tree, i.id, &mut vec);
174 ItemKind::MacroDef(..) => SmallVec::new(),
175 ItemKind::Fn(..) | ItemKind::Impl { of_trait: None, .. } => smallvec![i.id],
176 ItemKind::Static(ref ty, ..) => {
177 let mut ids = smallvec![i.id];
178 if self.sess.features_untracked().impl_trait_in_bindings {
179 let mut visitor = ImplTraitTypeIdVisitor { ids: &mut ids };
180 visitor.visit_ty(ty);
184 ItemKind::Const(ref ty, ..) => {
185 let mut ids = smallvec![i.id];
186 if self.sess.features_untracked().impl_trait_in_bindings {
187 let mut visitor = ImplTraitTypeIdVisitor { ids: &mut ids };
188 visitor.visit_ty(ty);
192 _ => smallvec![i.id],
197 .map(|node_id| hir::ItemId { id: self.allocate_hir_id_counter(node_id) })
201 fn lower_item_id_use_tree(
205 vec: &mut SmallVec<[NodeId; 1]>,
208 UseTreeKind::Nested(ref nested_vec) => {
209 for &(ref nested, id) in nested_vec {
211 self.lower_item_id_use_tree(nested, id, vec);
214 UseTreeKind::Glob => {}
215 UseTreeKind::Simple(_, id1, id2) => {
217 self.expect_full_res_from_use(base_id).skip(1).zip([id1, id2].iter())
225 pub fn lower_item(&mut self, i: &Item) -> Option<hir::Item<'hir>> {
226 let mut ident = i.ident;
227 let mut vis = self.lower_visibility(&i.vis, None);
228 let attrs = self.lower_attrs(&i.attrs);
230 if let ItemKind::MacroDef(ref def) = i.kind {
231 if !def.legacy || attr::contains_name(&i.attrs, sym::macro_export) {
232 let body = self.lower_token_stream(def.body.inner_tokens());
233 let hir_id = self.lower_node_id(i.id);
234 self.exported_macros.push(hir::MacroDef {
244 self.non_exported_macro_attrs.extend(attrs.iter().cloned());
249 let kind = self.lower_item_kind(i.span, i.id, &mut ident, attrs, &mut vis, &i.kind);
251 Some(hir::Item { hir_id: self.lower_node_id(i.id), ident, attrs, kind, vis, span: i.span })
259 attrs: &'hir [Attribute],
260 vis: &mut hir::Visibility<'hir>,
262 ) -> hir::ItemKind<'hir> {
264 ItemKind::ExternCrate(orig_name) => hir::ItemKind::ExternCrate(orig_name),
265 ItemKind::Use(ref use_tree) => {
266 // Start with an empty prefix.
267 let prefix = Path { segments: vec![], span: use_tree.span };
269 self.lower_use_tree(use_tree, &prefix, id, vis, ident, attrs)
271 ItemKind::Static(ref t, m, ref e) => {
272 let ty = self.lower_ty(
274 if self.sess.features_untracked().impl_trait_in_bindings {
275 ImplTraitContext::OpaqueTy(None)
277 ImplTraitContext::Disallowed(ImplTraitPosition::Binding)
280 hir::ItemKind::Static(ty, m, self.lower_const_body(span, Some(e)))
282 ItemKind::Const(ref t, ref e) => {
283 let ty = self.lower_ty(
285 if self.sess.features_untracked().impl_trait_in_bindings {
286 ImplTraitContext::OpaqueTy(None)
288 ImplTraitContext::Disallowed(ImplTraitPosition::Binding)
291 hir::ItemKind::Const(ty, self.lower_const_body(span, Some(e)))
293 ItemKind::Fn(FnSig { ref decl, header }, ref generics, ref body) => {
294 let fn_def_id = self.resolver.definitions().local_def_id(id);
295 self.with_new_scopes(|this| {
296 this.current_item = Some(ident.span);
298 // Note: we don't need to change the return type from `T` to
299 // `impl Future<Output = T>` here because lower_body
300 // only cares about the input argument patterns in the function
301 // declaration (decl), not the return types.
303 this.lower_maybe_async_body(span, &decl, header.asyncness.node, Some(body));
305 let (generics, decl) = this.add_in_band_defs(
308 AnonymousLifetimeMode::PassThrough,
312 Some((fn_def_id, idty)),
314 header.asyncness.node.opt_return_id(),
318 let sig = hir::FnSig { decl, header: this.lower_fn_header(header) };
319 hir::ItemKind::Fn(sig, generics, body_id)
322 ItemKind::Mod(ref m) => hir::ItemKind::Mod(self.lower_mod(m)),
323 ItemKind::ForeignMod(ref nm) => hir::ItemKind::ForeignMod(self.lower_foreign_mod(nm)),
324 ItemKind::GlobalAsm(ref ga) => hir::ItemKind::GlobalAsm(self.lower_global_asm(ga)),
325 ItemKind::TyAlias(ref ty, ref generics) => match ty.kind.opaque_top_hack() {
327 let ty = self.lower_ty(ty, ImplTraitContext::disallowed());
328 let generics = self.lower_generics(generics, ImplTraitContext::disallowed());
329 hir::ItemKind::TyAlias(ty, generics)
332 let ty = hir::OpaqueTy {
333 generics: self.lower_generics(generics, ImplTraitContext::OpaqueTy(None)),
334 bounds: self.lower_param_bounds(bounds, ImplTraitContext::OpaqueTy(None)),
336 origin: hir::OpaqueTyOrigin::TypeAlias,
338 hir::ItemKind::OpaqueTy(ty)
341 ItemKind::Enum(ref enum_definition, ref generics) => hir::ItemKind::Enum(
343 variants: self.arena.alloc_from_iter(
344 enum_definition.variants.iter().map(|x| self.lower_variant(x)),
347 self.lower_generics(generics, ImplTraitContext::disallowed()),
349 ItemKind::Struct(ref struct_def, ref generics) => {
350 let struct_def = self.lower_variant_data(struct_def);
351 hir::ItemKind::Struct(
353 self.lower_generics(generics, ImplTraitContext::disallowed()),
356 ItemKind::Union(ref vdata, ref generics) => {
357 let vdata = self.lower_variant_data(vdata);
358 hir::ItemKind::Union(
360 self.lower_generics(generics, ImplTraitContext::disallowed()),
368 generics: ref ast_generics,
369 of_trait: ref trait_ref,
371 items: ref impl_items,
373 let def_id = self.resolver.definitions().local_def_id(id);
375 // Lower the "impl header" first. This ordering is important
376 // for in-band lifetimes! Consider `'a` here:
378 // impl Foo<'a> for u32 {
379 // fn method(&'a self) { .. }
382 // Because we start by lowering the `Foo<'a> for u32`
383 // part, we will add `'a` to the list of generics on
384 // the impl. When we then encounter it later in the
385 // method, it will not be considered an in-band
386 // lifetime to be added, but rather a reference to a
388 let lowered_trait_impl_id = self.lower_node_id(id);
389 let (generics, (trait_ref, lowered_ty)) = self.add_in_band_defs(
392 AnonymousLifetimeMode::CreateParameter,
394 let trait_ref = trait_ref.as_ref().map(|trait_ref| {
395 this.lower_trait_ref(trait_ref, ImplTraitContext::disallowed())
398 if let Some(ref trait_ref) = trait_ref {
399 if let Res::Def(DefKind::Trait, def_id) = trait_ref.path.res {
403 .push(lowered_trait_impl_id);
407 let lowered_ty = this.lower_ty(ty, ImplTraitContext::disallowed());
409 (trait_ref, lowered_ty)
414 self.with_in_scope_lifetime_defs(&ast_generics.params, |this| {
415 this.arena.alloc_from_iter(
416 impl_items.iter().map(|item| this.lower_impl_item_ref(item)),
420 hir::ItemKind::Impl {
423 defaultness: self.lower_defaultness(defaultness, true /* [1] */),
428 items: new_impl_items,
431 ItemKind::Trait(is_auto, unsafety, ref generics, ref bounds, ref items) => {
432 let bounds = self.lower_param_bounds(bounds, ImplTraitContext::disallowed());
435 .alloc_from_iter(items.iter().map(|item| self.lower_trait_item_ref(item)));
436 hir::ItemKind::Trait(
439 self.lower_generics(generics, ImplTraitContext::disallowed()),
444 ItemKind::TraitAlias(ref generics, ref bounds) => hir::ItemKind::TraitAlias(
445 self.lower_generics(generics, ImplTraitContext::disallowed()),
446 self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
448 ItemKind::MacroDef(..) | ItemKind::Mac(..) => {
449 bug!("`TyMac` should have been expanded by now")
453 // [1] `defaultness.has_value()` is never called for an `impl`, always `true` in order to
454 // not cause an assertion failure inside the `lower_defaultness` function.
462 vis: &mut hir::Visibility<'hir>,
464 attrs: &'hir [Attribute],
465 ) -> hir::ItemKind<'hir> {
466 debug!("lower_use_tree(tree={:?})", tree);
467 debug!("lower_use_tree: vis = {:?}", vis);
469 let path = &tree.prefix;
470 let segments = prefix.segments.iter().chain(path.segments.iter()).cloned().collect();
473 UseTreeKind::Simple(rename, id1, id2) => {
474 *ident = tree.ident();
476 // First, apply the prefix to the path.
477 let mut path = Path { segments, span: path.span };
479 // Correctly resolve `self` imports.
480 if path.segments.len() > 1
481 && path.segments.last().unwrap().ident.name == kw::SelfLower
483 let _ = path.segments.pop();
484 if rename.is_none() {
485 *ident = path.segments.last().unwrap().ident;
489 let mut resolutions = self.expect_full_res_from_use(id);
490 // We want to return *something* from this function, so hold onto the first item
492 let ret_res = self.lower_res(resolutions.next().unwrap_or(Res::Err));
494 // Here, we are looping over namespaces, if they exist for the definition
495 // being imported. We only handle type and value namespaces because we
496 // won't be dealing with macros in the rest of the compiler.
497 // Essentially a single `use` which imports two names is desugared into
499 for (res, &new_node_id) in resolutions.zip([id1, id2].iter()) {
501 let mut path = path.clone();
502 for seg in &mut path.segments {
503 seg.id = self.resolver.next_node_id();
505 let span = path.span;
507 self.with_hir_id_owner(new_node_id, |this| {
508 let new_id = this.lower_node_id(new_node_id);
509 let res = this.lower_res(res);
510 let path = this.lower_path_extra(res, &path, ParamMode::Explicit, None);
511 let kind = hir::ItemKind::Use(path, hir::UseKind::Single);
512 let vis = this.rebuild_vis(&vis);
514 this.insert_item(hir::Item {
525 let path = self.lower_path_extra(ret_res, &path, ParamMode::Explicit, None);
526 hir::ItemKind::Use(path, hir::UseKind::Single)
528 UseTreeKind::Glob => {
530 self.lower_path(id, &Path { segments, span: path.span }, ParamMode::Explicit);
531 hir::ItemKind::Use(path, hir::UseKind::Glob)
533 UseTreeKind::Nested(ref trees) => {
534 // Nested imports are desugared into simple imports.
535 // So, if we start with
538 // pub(x) use foo::{a, b};
541 // we will create three items:
544 // pub(x) use foo::a;
545 // pub(x) use foo::b;
546 // pub(x) use foo::{}; // <-- this is called the `ListStem`
549 // The first two are produced by recursively invoking
550 // `lower_use_tree` (and indeed there may be things
551 // like `use foo::{a::{b, c}}` and so forth). They
552 // wind up being directly added to
553 // `self.items`. However, the structure of this
554 // function also requires us to return one item, and
555 // for that we return the `{}` import (called the
558 let prefix = Path { segments, span: prefix.span.to(path.span) };
560 // Add all the nested `PathListItem`s to the HIR.
561 for &(ref use_tree, id) in trees {
562 let new_hir_id = self.lower_node_id(id);
564 let mut prefix = prefix.clone();
566 // Give the segments new node-ids since they are being cloned.
567 for seg in &mut prefix.segments {
568 seg.id = self.resolver.next_node_id();
571 // Each `use` import is an item and thus are owners of the
572 // names in the path. Up to this point the nested import is
573 // the current owner, since we want each desugared import to
574 // own its own names, we have to adjust the owner before
575 // lowering the rest of the import.
576 self.with_hir_id_owner(id, |this| {
577 let mut vis = this.rebuild_vis(&vis);
578 let mut ident = *ident;
581 this.lower_use_tree(use_tree, &prefix, id, &mut vis, &mut ident, attrs);
583 this.insert_item(hir::Item {
594 // Subtle and a bit hacky: we lower the privacy level
595 // of the list stem to "private" most of the time, but
596 // not for "restricted" paths. The key thing is that
597 // we don't want it to stay as `pub` (with no caveats)
598 // because that affects rustdoc and also the lints
599 // about `pub` items. But we can't *always* make it
600 // private -- particularly not for restricted paths --
601 // because it contains node-ids that would then be
602 // unused, failing the check that HirIds are "densely
605 hir::VisibilityKind::Public
606 | hir::VisibilityKind::Crate(_)
607 | hir::VisibilityKind::Inherited => {
608 *vis = respan(prefix.span.shrink_to_lo(), hir::VisibilityKind::Inherited);
610 hir::VisibilityKind::Restricted { .. } => {
611 // Do nothing here, as described in the comment on the match.
615 let res = self.expect_full_res_from_use(id).next().unwrap_or(Res::Err);
616 let res = self.lower_res(res);
617 let path = self.lower_path_extra(res, &prefix, ParamMode::Explicit, None);
618 hir::ItemKind::Use(path, hir::UseKind::ListStem)
623 /// Paths like the visibility path in `pub(super) use foo::{bar, baz}` are repeated
624 /// many times in the HIR tree; for each occurrence, we need to assign distinct
625 /// `NodeId`s. (See, e.g., #56128.)
626 fn rebuild_use_path(&mut self, path: &hir::Path<'hir>) -> &'hir hir::Path<'hir> {
627 debug!("rebuild_use_path(path = {:?})", path);
629 self.arena.alloc_from_iter(path.segments.iter().map(|seg| hir::PathSegment {
631 hir_id: seg.hir_id.map(|_| self.next_id()),
634 infer_args: seg.infer_args,
636 self.arena.alloc(hir::Path { span: path.span, res: path.res, segments })
639 fn rebuild_vis(&mut self, vis: &hir::Visibility<'hir>) -> hir::Visibility<'hir> {
640 let vis_kind = match vis.node {
641 hir::VisibilityKind::Public => hir::VisibilityKind::Public,
642 hir::VisibilityKind::Crate(sugar) => hir::VisibilityKind::Crate(sugar),
643 hir::VisibilityKind::Inherited => hir::VisibilityKind::Inherited,
644 hir::VisibilityKind::Restricted { ref path, hir_id: _ } => {
645 hir::VisibilityKind::Restricted {
646 path: self.rebuild_use_path(path),
647 hir_id: self.next_id(),
651 respan(vis.span, vis_kind)
654 fn lower_foreign_item(&mut self, i: &ForeignItem) -> hir::ForeignItem<'hir> {
655 let def_id = self.resolver.definitions().local_def_id(i.id);
657 hir_id: self.lower_node_id(i.id),
659 attrs: self.lower_attrs(&i.attrs),
661 ForeignItemKind::Fn(ref fdec, ref generics) => {
662 let (generics, (fn_dec, fn_args)) = self.add_in_band_defs(
665 AnonymousLifetimeMode::PassThrough,
668 // Disallow `impl Trait` in foreign items.
669 this.lower_fn_decl(fdec, None, false, None),
670 this.lower_fn_params_to_names(fdec),
675 hir::ForeignItemKind::Fn(fn_dec, fn_args, generics)
677 ForeignItemKind::Static(ref t, m) => {
678 let ty = self.lower_ty(t, ImplTraitContext::disallowed());
679 hir::ForeignItemKind::Static(ty, m)
681 ForeignItemKind::Ty => hir::ForeignItemKind::Type,
682 ForeignItemKind::Macro(_) => panic!("macro shouldn't exist here"),
684 vis: self.lower_visibility(&i.vis, None),
689 fn lower_foreign_mod(&mut self, fm: &ForeignMod) -> hir::ForeignMod<'hir> {
691 abi: fm.abi.map_or(abi::Abi::C, |abi| self.lower_abi(abi)),
692 items: self.arena.alloc_from_iter(fm.items.iter().map(|x| self.lower_foreign_item(x))),
696 fn lower_global_asm(&mut self, ga: &GlobalAsm) -> &'hir hir::GlobalAsm {
697 self.arena.alloc(hir::GlobalAsm { asm: ga.asm })
700 fn lower_variant(&mut self, v: &Variant) -> hir::Variant<'hir> {
702 attrs: self.lower_attrs(&v.attrs),
703 data: self.lower_variant_data(&v.data),
704 disr_expr: v.disr_expr.as_ref().map(|e| self.lower_anon_const(e)),
705 id: self.lower_node_id(v.id),
711 fn lower_variant_data(&mut self, vdata: &VariantData) -> hir::VariantData<'hir> {
713 VariantData::Struct(ref fields, recovered) => hir::VariantData::Struct(
715 .alloc_from_iter(fields.iter().enumerate().map(|f| self.lower_struct_field(f))),
718 VariantData::Tuple(ref fields, id) => hir::VariantData::Tuple(
720 .alloc_from_iter(fields.iter().enumerate().map(|f| self.lower_struct_field(f))),
721 self.lower_node_id(id),
723 VariantData::Unit(id) => hir::VariantData::Unit(self.lower_node_id(id)),
727 fn lower_struct_field(&mut self, (index, f): (usize, &StructField)) -> hir::StructField<'hir> {
728 let ty = if let TyKind::Path(ref qself, ref path) = f.ty.kind {
729 let t = self.lower_path_ty(
733 ParamMode::ExplicitNamed, // no `'_` in declarations (Issue #61124)
734 ImplTraitContext::disallowed(),
738 self.lower_ty(&f.ty, ImplTraitContext::disallowed())
742 hir_id: self.lower_node_id(f.id),
743 ident: match f.ident {
744 Some(ident) => ident,
745 // FIXME(jseyfried): positional field hygiene.
746 None => Ident::new(sym::integer(index), f.span),
748 vis: self.lower_visibility(&f.vis, None),
750 attrs: self.lower_attrs(&f.attrs),
754 fn lower_trait_item(&mut self, i: &AssocItem) -> hir::TraitItem<'hir> {
755 let trait_item_def_id = self.resolver.definitions().local_def_id(i.id);
757 let (generics, kind) = match i.kind {
758 AssocItemKind::Const(ref ty, ref default) => {
759 let generics = self.lower_generics(&i.generics, ImplTraitContext::disallowed());
760 let ty = self.lower_ty(ty, ImplTraitContext::disallowed());
763 hir::TraitItemKind::Const(
765 default.as_ref().map(|x| self.lower_const_body(i.span, Some(x))),
769 AssocItemKind::Fn(ref sig, None) => {
770 let names = self.lower_fn_params_to_names(&sig.decl);
771 let (generics, sig) =
772 self.lower_method_sig(&i.generics, sig, trait_item_def_id, false, None);
773 (generics, hir::TraitItemKind::Method(sig, hir::TraitMethod::Required(names)))
775 AssocItemKind::Fn(ref sig, Some(ref body)) => {
776 let body_id = self.lower_fn_body_block(i.span, &sig.decl, Some(body));
777 let (generics, sig) =
778 self.lower_method_sig(&i.generics, sig, trait_item_def_id, false, None);
779 (generics, hir::TraitItemKind::Method(sig, hir::TraitMethod::Provided(body_id)))
781 AssocItemKind::TyAlias(ref bounds, ref default) => {
782 let ty = default.as_ref().map(|x| self.lower_ty(x, ImplTraitContext::disallowed()));
783 let generics = self.lower_generics(&i.generics, ImplTraitContext::disallowed());
784 let kind = hir::TraitItemKind::Type(
785 self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
791 AssocItemKind::Macro(..) => bug!("macro item shouldn't exist at this point"),
795 hir_id: self.lower_node_id(i.id),
797 attrs: self.lower_attrs(&i.attrs),
804 fn lower_trait_item_ref(&mut self, i: &AssocItem) -> hir::TraitItemRef {
805 let (kind, has_default) = match i.kind {
806 AssocItemKind::Const(_, ref default) => (hir::AssocItemKind::Const, default.is_some()),
807 AssocItemKind::TyAlias(_, ref default) => (hir::AssocItemKind::Type, default.is_some()),
808 AssocItemKind::Fn(ref sig, ref default) => {
809 (hir::AssocItemKind::Method { has_self: sig.decl.has_self() }, default.is_some())
811 AssocItemKind::Macro(..) => unimplemented!(),
814 id: hir::TraitItemId { hir_id: self.lower_node_id(i.id) },
817 defaultness: self.lower_defaultness(Defaultness::Default, has_default),
822 /// Construct `ExprKind::Err` for the given `span`.
823 fn expr_err(&mut self, span: Span) -> hir::Expr<'hir> {
824 self.expr(span, hir::ExprKind::Err, AttrVec::new())
827 fn lower_impl_item(&mut self, i: &AssocItem) -> hir::ImplItem<'hir> {
828 let impl_item_def_id = self.resolver.definitions().local_def_id(i.id);
830 let (generics, kind) = match i.kind {
831 AssocItemKind::Const(ref ty, ref expr) => {
832 let generics = self.lower_generics(&i.generics, ImplTraitContext::disallowed());
833 let ty = self.lower_ty(ty, ImplTraitContext::disallowed());
836 hir::ImplItemKind::Const(ty, self.lower_const_body(i.span, expr.as_deref())),
839 AssocItemKind::Fn(ref sig, ref body) => {
840 self.current_item = Some(i.span);
841 let body_id = self.lower_maybe_async_body(
844 sig.header.asyncness.node,
847 let impl_trait_return_allow = !self.is_in_trait_impl;
848 let (generics, sig) = self.lower_method_sig(
852 impl_trait_return_allow,
853 sig.header.asyncness.node.opt_return_id(),
856 (generics, hir::ImplItemKind::Method(sig, body_id))
858 AssocItemKind::TyAlias(_, ref ty) => {
859 let generics = self.lower_generics(&i.generics, ImplTraitContext::disallowed());
860 let kind = match ty {
862 let ty = self.arena.alloc(self.ty(i.span, hir::TyKind::Err));
863 hir::ImplItemKind::TyAlias(ty)
865 Some(ty) => match ty.kind.opaque_top_hack() {
867 let ty = self.lower_ty(ty, ImplTraitContext::disallowed());
868 hir::ImplItemKind::TyAlias(ty)
871 let bs = self.lower_param_bounds(bs, ImplTraitContext::disallowed());
872 hir::ImplItemKind::OpaqueTy(bs)
878 AssocItemKind::Macro(..) => bug!("`TyMac` should have been expanded by now"),
882 hir_id: self.lower_node_id(i.id),
884 attrs: self.lower_attrs(&i.attrs),
886 vis: self.lower_visibility(&i.vis, None),
887 defaultness: self.lower_defaultness(i.defaultness, true /* [1] */),
892 // [1] since `default impl` is not yet implemented, this is always true in impls
895 fn lower_impl_item_ref(&mut self, i: &AssocItem) -> hir::ImplItemRef<'hir> {
897 id: hir::ImplItemId { hir_id: self.lower_node_id(i.id) },
900 vis: self.lower_visibility(&i.vis, Some(i.id)),
901 defaultness: self.lower_defaultness(i.defaultness, true /* [1] */),
902 kind: match &i.kind {
903 AssocItemKind::Const(..) => hir::AssocItemKind::Const,
904 AssocItemKind::TyAlias(_, ty) => {
905 match ty.as_deref().and_then(|ty| ty.kind.opaque_top_hack()) {
906 None => hir::AssocItemKind::Type,
907 Some(_) => hir::AssocItemKind::OpaqueTy,
910 AssocItemKind::Fn(sig, _) => {
911 hir::AssocItemKind::Method { has_self: sig.decl.has_self() }
913 AssocItemKind::Macro(..) => unimplemented!(),
917 // [1] since `default impl` is not yet implemented, this is always true in impls
920 /// If an `explicit_owner` is given, this method allocates the `HirId` in
921 /// the address space of that item instead of the item currently being
922 /// lowered. This can happen during `lower_impl_item_ref()` where we need to
923 /// lower a `Visibility` value although we haven't lowered the owning
924 /// `ImplItem` in question yet.
928 explicit_owner: Option<NodeId>,
929 ) -> hir::Visibility<'hir> {
930 let node = match v.node {
931 VisibilityKind::Public => hir::VisibilityKind::Public,
932 VisibilityKind::Crate(sugar) => hir::VisibilityKind::Crate(sugar),
933 VisibilityKind::Restricted { ref path, id } => {
934 debug!("lower_visibility: restricted path id = {:?}", id);
935 let lowered_id = if let Some(owner) = explicit_owner {
936 self.lower_node_id_with_owner(id, owner)
938 self.lower_node_id(id)
940 let res = self.expect_full_res(id);
941 let res = self.lower_res(res);
942 hir::VisibilityKind::Restricted {
943 path: self.lower_path_extra(res, path, ParamMode::Explicit, explicit_owner),
947 VisibilityKind::Inherited => hir::VisibilityKind::Inherited,
952 fn lower_defaultness(&self, d: Defaultness, has_value: bool) -> hir::Defaultness {
954 Defaultness::Default => hir::Defaultness::Default { has_value: has_value },
955 Defaultness::Final => {
957 hir::Defaultness::Final
964 params: &'hir [hir::Param<'hir>],
965 value: hir::Expr<'hir>,
967 let body = hir::Body { generator_kind: self.generator_kind, params, value };
969 self.bodies.insert(id, body);
975 f: impl FnOnce(&mut Self) -> (&'hir [hir::Param<'hir>], hir::Expr<'hir>),
977 let prev_gen_kind = self.generator_kind.take();
978 let (parameters, result) = f(self);
979 let body_id = self.record_body(parameters, result);
980 self.generator_kind = prev_gen_kind;
984 fn lower_param(&mut self, param: &Param) -> hir::Param<'hir> {
986 attrs: self.lower_attrs(¶m.attrs),
987 hir_id: self.lower_node_id(param.id),
988 pat: self.lower_pat(¶m.pat),
993 pub(super) fn lower_fn_body(
996 body: impl FnOnce(&mut Self) -> hir::Expr<'hir>,
998 self.lower_body(|this| {
1000 this.arena.alloc_from_iter(decl.inputs.iter().map(|x| this.lower_param(x))),
1006 fn lower_fn_body_block(
1010 body: Option<&Block>,
1012 self.lower_fn_body(decl, |this| this.lower_block_expr_opt(span, body))
1015 fn lower_block_expr_opt(&mut self, span: Span, block: Option<&Block>) -> hir::Expr<'hir> {
1017 Some(block) => self.lower_block_expr(block),
1018 None => self.expr_err(span),
1022 pub(super) fn lower_const_body(&mut self, span: Span, expr: Option<&Expr>) -> hir::BodyId {
1023 self.lower_body(|this| {
1027 Some(expr) => this.lower_expr_mut(expr),
1028 None => this.expr_err(span),
1034 fn lower_maybe_async_body(
1039 body: Option<&Block>,
1041 let closure_id = match asyncness {
1042 IsAsync::Async { closure_id, .. } => closure_id,
1043 IsAsync::NotAsync => return self.lower_fn_body_block(span, decl, body),
1046 self.lower_body(|this| {
1047 let mut parameters: Vec<hir::Param<'_>> = Vec::new();
1048 let mut statements: Vec<hir::Stmt<'_>> = Vec::new();
1050 // Async function parameters are lowered into the closure body so that they are
1051 // captured and so that the drop order matches the equivalent non-async functions.
1055 // async fn foo(<pattern>: <ty>, <pattern>: <ty>, <pattern>: <ty>) {
1061 // fn foo(__arg0: <ty>, __arg1: <ty>, __arg2: <ty>) {
1063 // let __arg2 = __arg2;
1064 // let <pattern> = __arg2;
1065 // let __arg1 = __arg1;
1066 // let <pattern> = __arg1;
1067 // let __arg0 = __arg0;
1068 // let <pattern> = __arg0;
1069 // drop-temps { <body> } // see comments later in fn for details
1073 // If `<pattern>` is a simple ident, then it is lowered to a single
1074 // `let <pattern> = <pattern>;` statement as an optimization.
1076 // Note that the body is embedded in `drop-temps`; an
1077 // equivalent desugaring would be `return { <body>
1078 // };`. The key point is that we wish to drop all the
1079 // let-bound variables and temporaries created in the body
1080 // (and its tail expression!) before we drop the
1081 // parameters (c.f. rust-lang/rust#64512).
1082 for (index, parameter) in decl.inputs.iter().enumerate() {
1083 let parameter = this.lower_param(parameter);
1084 let span = parameter.pat.span;
1086 // Check if this is a binding pattern, if so, we can optimize and avoid adding a
1087 // `let <pat> = __argN;` statement. In this case, we do not rename the parameter.
1088 let (ident, is_simple_parameter) = match parameter.pat.kind {
1089 hir::PatKind::Binding(hir::BindingAnnotation::Unannotated, _, ident, _) => {
1093 // Replace the ident for bindings that aren't simple.
1094 let name = format!("__arg{}", index);
1095 let ident = Ident::from_str(&name);
1101 let desugared_span = this.mark_span_with_reason(DesugaringKind::Async, span, None);
1103 // Construct a parameter representing `__argN: <ty>` to replace the parameter of the
1106 // If this is the simple case, this parameter will end up being the same as the
1107 // original parameter, but with a different pattern id.
1108 let mut stmt_attrs = AttrVec::new();
1109 stmt_attrs.extend(parameter.attrs.iter().cloned());
1110 let (new_parameter_pat, new_parameter_id) = this.pat_ident(desugared_span, ident);
1111 let new_parameter = hir::Param {
1112 attrs: parameter.attrs,
1113 hir_id: parameter.hir_id,
1114 pat: new_parameter_pat,
1115 span: parameter.span,
1118 if is_simple_parameter {
1119 // If this is the simple case, then we only insert one statement that is
1120 // `let <pat> = <pat>;`. We re-use the original argument's pattern so that
1121 // `HirId`s are densely assigned.
1122 let expr = this.expr_ident(desugared_span, ident, new_parameter_id);
1123 let stmt = this.stmt_let_pat(
1128 hir::LocalSource::AsyncFn,
1130 statements.push(stmt);
1132 // If this is not the simple case, then we construct two statements:
1135 // let __argN = __argN;
1136 // let <pat> = __argN;
1139 // The first statement moves the parameter into the closure and thus ensures
1140 // that the drop order is correct.
1142 // The second statement creates the bindings that the user wrote.
1144 // Construct the `let mut __argN = __argN;` statement. It must be a mut binding
1145 // because the user may have specified a `ref mut` binding in the next
1147 let (move_pat, move_id) = this.pat_ident_binding_mode(
1150 hir::BindingAnnotation::Mutable,
1152 let move_expr = this.expr_ident(desugared_span, ident, new_parameter_id);
1153 let move_stmt = this.stmt_let_pat(
1158 hir::LocalSource::AsyncFn,
1161 // Construct the `let <pat> = __argN;` statement. We re-use the original
1162 // parameter's pattern so that `HirId`s are densely assigned.
1163 let pattern_expr = this.expr_ident(desugared_span, ident, move_id);
1164 let pattern_stmt = this.stmt_let_pat(
1169 hir::LocalSource::AsyncFn,
1172 statements.push(move_stmt);
1173 statements.push(pattern_stmt);
1176 parameters.push(new_parameter);
1179 let body_span = body.map_or(span, |b| b.span);
1180 let async_expr = this.make_async_expr(
1185 hir::AsyncGeneratorKind::Fn,
1187 // Create a block from the user's function body:
1188 let user_body = this.lower_block_expr_opt(body_span, body);
1190 // Transform into `drop-temps { <user-body> }`, an expression:
1191 let desugared_span =
1192 this.mark_span_with_reason(DesugaringKind::Async, user_body.span, None);
1193 let user_body = this.expr_drop_temps(
1195 this.arena.alloc(user_body),
1199 // As noted above, create the final block like
1203 // let $param_pattern = $raw_param;
1205 // drop-temps { <user-body> }
1208 let body = this.block_all(
1210 this.arena.alloc_from_iter(statements),
1214 this.expr_block(body, AttrVec::new())
1219 this.arena.alloc_from_iter(parameters),
1220 this.expr(body_span, async_expr, AttrVec::new()),
1225 fn lower_method_sig(
1227 generics: &Generics,
1230 impl_trait_return_allow: bool,
1231 is_async: Option<NodeId>,
1232 ) -> (hir::Generics<'hir>, hir::FnSig<'hir>) {
1233 let header = self.lower_fn_header(sig.header);
1234 let (generics, decl) = self.add_in_band_defs(
1237 AnonymousLifetimeMode::PassThrough,
1241 Some((fn_def_id, idty)),
1242 impl_trait_return_allow,
1247 (generics, hir::FnSig { header, decl })
1250 fn lower_fn_header(&mut self, h: FnHeader) -> hir::FnHeader {
1252 unsafety: h.unsafety,
1253 asyncness: self.lower_asyncness(h.asyncness.node),
1254 constness: h.constness.node,
1255 abi: self.lower_extern(h.ext),
1259 pub(super) fn lower_abi(&mut self, abi: StrLit) -> abi::Abi {
1260 abi::lookup(&abi.symbol_unescaped.as_str()).unwrap_or_else(|| {
1261 self.error_on_invalid_abi(abi);
1266 pub(super) fn lower_extern(&mut self, ext: Extern) -> abi::Abi {
1268 Extern::None => abi::Abi::Rust,
1269 Extern::Implicit => abi::Abi::C,
1270 Extern::Explicit(abi) => self.lower_abi(abi),
1274 fn error_on_invalid_abi(&self, abi: StrLit) {
1275 struct_span_err!(self.sess, abi.span, E0703, "invalid ABI: found `{}`", abi.symbol)
1276 .span_label(abi.span, "invalid ABI")
1277 .help(&format!("valid ABIs: {}", abi::all_names().join(", ")))
1281 fn lower_asyncness(&mut self, a: IsAsync) -> hir::IsAsync {
1283 IsAsync::Async { .. } => hir::IsAsync::Async,
1284 IsAsync::NotAsync => hir::IsAsync::NotAsync,
1288 pub(super) fn lower_generics_mut(
1290 generics: &Generics,
1291 itctx: ImplTraitContext<'_, 'hir>,
1292 ) -> GenericsCtor<'hir> {
1293 // Collect `?Trait` bounds in where clause and move them to parameter definitions.
1294 // FIXME: this could probably be done with less rightward drift. It also looks like two
1295 // control paths where `report_error` is called are the only paths that advance to after the
1296 // match statement, so the error reporting could probably just be moved there.
1297 let mut add_bounds: NodeMap<Vec<_>> = Default::default();
1298 for pred in &generics.where_clause.predicates {
1299 if let WherePredicate::BoundPredicate(ref bound_pred) = *pred {
1300 'next_bound: for bound in &bound_pred.bounds {
1301 if let GenericBound::Trait(_, TraitBoundModifier::Maybe) = *bound {
1302 let report_error = |this: &mut Self| {
1303 this.diagnostic().span_err(
1304 bound_pred.bounded_ty.span,
1305 "`?Trait` bounds are only permitted at the \
1306 point where a type parameter is declared",
1309 // Check if the where clause type is a plain type parameter.
1310 match bound_pred.bounded_ty.kind {
1311 TyKind::Path(None, ref path)
1312 if path.segments.len() == 1
1313 && bound_pred.bound_generic_params.is_empty() =>
1315 if let Some(Res::Def(DefKind::TyParam, def_id)) = self
1317 .get_partial_res(bound_pred.bounded_ty.id)
1318 .map(|d| d.base_res())
1320 if let Some(node_id) =
1321 self.resolver.definitions().as_local_node_id(def_id)
1323 for param in &generics.params {
1325 GenericParamKind::Type { .. } => {
1326 if node_id == param.id {
1330 .push(bound.clone());
1331 continue 'next_bound;
1341 _ => report_error(self),
1349 params: self.lower_generic_params_mut(&generics.params, &add_bounds, itctx).collect(),
1350 where_clause: self.lower_where_clause(&generics.where_clause),
1351 span: generics.span,
1355 pub(super) fn lower_generics(
1357 generics: &Generics,
1358 itctx: ImplTraitContext<'_, 'hir>,
1359 ) -> hir::Generics<'hir> {
1360 let generics_ctor = self.lower_generics_mut(generics, itctx);
1361 generics_ctor.into_generics(self.arena)
1364 fn lower_where_clause(&mut self, wc: &WhereClause) -> hir::WhereClause<'hir> {
1365 self.with_anonymous_lifetime_mode(AnonymousLifetimeMode::ReportError, |this| {
1367 predicates: this.arena.alloc_from_iter(
1368 wc.predicates.iter().map(|predicate| this.lower_where_predicate(predicate)),
1375 fn lower_where_predicate(&mut self, pred: &WherePredicate) -> hir::WherePredicate<'hir> {
1377 WherePredicate::BoundPredicate(WhereBoundPredicate {
1378 ref bound_generic_params,
1383 self.with_in_scope_lifetime_defs(&bound_generic_params, |this| {
1384 hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
1385 bound_generic_params: this.lower_generic_params(
1386 bound_generic_params,
1387 &NodeMap::default(),
1388 ImplTraitContext::disallowed(),
1390 bounded_ty: this.lower_ty(bounded_ty, ImplTraitContext::disallowed()),
1391 bounds: this.arena.alloc_from_iter(bounds.iter().filter_map(|bound| {
1393 // Ignore `?Trait` bounds.
1394 // They were copied into type parameters already.
1395 GenericBound::Trait(_, TraitBoundModifier::Maybe) => None,
1397 this.lower_param_bound(bound, ImplTraitContext::disallowed()),
1405 WherePredicate::RegionPredicate(WhereRegionPredicate {
1409 }) => hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate {
1411 lifetime: self.lower_lifetime(lifetime),
1412 bounds: self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
1414 WherePredicate::EqPredicate(WhereEqPredicate { id, ref lhs_ty, ref rhs_ty, span }) => {
1415 hir::WherePredicate::EqPredicate(hir::WhereEqPredicate {
1416 hir_id: self.lower_node_id(id),
1417 lhs_ty: self.lower_ty(lhs_ty, ImplTraitContext::disallowed()),
1418 rhs_ty: self.lower_ty(rhs_ty, ImplTraitContext::disallowed()),
1426 /// Helper struct for delayed construction of Generics.
1427 pub(super) struct GenericsCtor<'hir> {
1428 pub(super) params: SmallVec<[hir::GenericParam<'hir>; 4]>,
1429 where_clause: hir::WhereClause<'hir>,
1433 impl<'hir> GenericsCtor<'hir> {
1434 pub(super) fn into_generics(self, arena: &'hir Arena<'hir>) -> hir::Generics<'hir> {
1436 params: arena.alloc_from_iter(self.params),
1437 where_clause: self.where_clause,