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 this.with_trait_impl_ref(opt_trait_ref, |this| visit::walk_item(this, item));
76 visit::walk_item(this, item);
82 fn visit_trait_item(&mut self, item: &'a AssocItem) {
83 self.lctx.with_hir_id_owner(item.id, |lctx| {
84 let hir_item = lctx.lower_trait_item(item);
85 let id = hir::TraitItemId { hir_id: hir_item.hir_id };
86 lctx.trait_items.insert(id, hir_item);
87 lctx.modules.get_mut(&lctx.current_module).unwrap().trait_items.insert(id);
90 visit::walk_trait_item(self, item);
93 fn visit_impl_item(&mut self, item: &'a AssocItem) {
94 self.lctx.with_hir_id_owner(item.id, |lctx| {
95 let hir_item = lctx.lower_impl_item(item);
96 let id = hir::ImplItemId { hir_id: hir_item.hir_id };
97 lctx.impl_items.insert(id, hir_item);
98 lctx.modules.get_mut(&lctx.current_module).unwrap().impl_items.insert(id);
100 visit::walk_impl_item(self, item);
104 impl<'hir> LoweringContext<'_, 'hir> {
105 // Same as the method above, but accepts `hir::GenericParam`s
106 // instead of `ast::GenericParam`s.
107 // This should only be used with generics that have already had their
108 // in-band lifetimes added. In practice, this means that this function is
109 // only used when lowering a child item of a trait or impl.
110 fn with_parent_item_lifetime_defs<T>(
112 parent_hir_id: hir::HirId,
113 f: impl FnOnce(&mut LoweringContext<'_, '_>) -> T,
115 let old_len = self.in_scope_lifetimes.len();
117 let parent_generics = match self.items.get(&parent_hir_id).unwrap().kind {
118 hir::ItemKind::Impl(_, _, _, ref generics, ..)
119 | hir::ItemKind::Trait(_, _, ref generics, ..) => &generics.params[..],
122 let lt_def_names = parent_generics.iter().filter_map(|param| match param.kind {
123 hir::GenericParamKind::Lifetime { .. } => Some(param.name.modern()),
126 self.in_scope_lifetimes.extend(lt_def_names);
130 self.in_scope_lifetimes.truncate(old_len);
134 // Clears (and restores) the `in_scope_lifetimes` field. Used when
135 // visiting nested items, which never inherit in-scope lifetimes
136 // from their surrounding environment.
137 fn without_in_scope_lifetime_defs<T>(
139 f: impl FnOnce(&mut LoweringContext<'_, '_>) -> T,
141 let old_in_scope_lifetimes = std::mem::replace(&mut self.in_scope_lifetimes, vec![]);
143 // this vector is only used when walking over impl headers,
144 // input types, and the like, and should not be non-empty in
146 assert!(self.lifetimes_to_define.is_empty());
150 assert!(self.in_scope_lifetimes.is_empty());
151 self.in_scope_lifetimes = old_in_scope_lifetimes;
156 pub(super) fn lower_mod(&mut self, m: &Mod) -> hir::Mod<'hir> {
161 .alloc_from_iter(m.items.iter().flat_map(|x| self.lower_item_id(x))),
165 pub(super) fn lower_item_id(&mut self, i: &Item) -> SmallVec<[hir::ItemId; 1]> {
166 let node_ids = match i.kind {
167 ItemKind::Use(ref use_tree) => {
168 let mut vec = smallvec![i.id];
169 self.lower_item_id_use_tree(use_tree, i.id, &mut vec);
172 ItemKind::MacroDef(..) => SmallVec::new(),
173 ItemKind::Fn(..) | ItemKind::Impl(.., None, _, _) => smallvec![i.id],
174 ItemKind::Static(ref ty, ..) => {
175 let mut ids = smallvec![i.id];
176 if self.sess.features_untracked().impl_trait_in_bindings {
177 let mut visitor = ImplTraitTypeIdVisitor { ids: &mut ids };
178 visitor.visit_ty(ty);
182 ItemKind::Const(ref ty, ..) => {
183 let mut ids = smallvec![i.id];
184 if self.sess.features_untracked().impl_trait_in_bindings {
185 let mut visitor = ImplTraitTypeIdVisitor { ids: &mut ids };
186 visitor.visit_ty(ty);
190 _ => smallvec![i.id],
195 .map(|node_id| hir::ItemId { id: self.allocate_hir_id_counter(node_id) })
199 fn lower_item_id_use_tree(
203 vec: &mut SmallVec<[NodeId; 1]>,
206 UseTreeKind::Nested(ref nested_vec) => {
207 for &(ref nested, id) in nested_vec {
209 self.lower_item_id_use_tree(nested, id, vec);
212 UseTreeKind::Glob => {}
213 UseTreeKind::Simple(_, id1, id2) => {
215 self.expect_full_res_from_use(base_id).skip(1).zip([id1, id2].iter())
223 pub fn lower_item(&mut self, i: &Item) -> Option<hir::Item<'hir>> {
224 let mut ident = i.ident;
225 let mut vis = self.lower_visibility(&i.vis, None);
226 let attrs = self.lower_attrs(&i.attrs);
228 if let ItemKind::MacroDef(ref def) = i.kind {
229 if !def.legacy || attr::contains_name(&i.attrs, sym::macro_export) {
230 let body = self.lower_token_stream(def.body.inner_tokens());
231 let hir_id = self.lower_node_id(i.id);
232 self.exported_macros.push(hir::MacroDef {
242 self.non_exported_macro_attrs.extend(attrs.iter().cloned());
247 let kind = self.lower_item_kind(i.span, i.id, &mut ident, attrs, &mut vis, &i.kind);
249 Some(hir::Item { hir_id: self.lower_node_id(i.id), ident, attrs, kind, vis, span: i.span })
257 attrs: &'hir [Attribute],
258 vis: &mut hir::Visibility<'hir>,
260 ) -> hir::ItemKind<'hir> {
262 ItemKind::ExternCrate(orig_name) => hir::ItemKind::ExternCrate(orig_name),
263 ItemKind::Use(ref use_tree) => {
264 // Start with an empty prefix.
265 let prefix = Path { segments: vec![], span: use_tree.span };
267 self.lower_use_tree(use_tree, &prefix, id, vis, ident, attrs)
269 ItemKind::Static(ref t, m, ref e) => {
270 let ty = self.lower_ty(
272 if self.sess.features_untracked().impl_trait_in_bindings {
273 ImplTraitContext::OpaqueTy(None)
275 ImplTraitContext::Disallowed(ImplTraitPosition::Binding)
278 hir::ItemKind::Static(ty, m, self.lower_const_body(span, Some(e)))
280 ItemKind::Const(ref t, ref e) => {
281 let ty = self.lower_ty(
283 if self.sess.features_untracked().impl_trait_in_bindings {
284 ImplTraitContext::OpaqueTy(None)
286 ImplTraitContext::Disallowed(ImplTraitPosition::Binding)
289 hir::ItemKind::Const(ty, self.lower_const_body(span, Some(e)))
291 ItemKind::Fn(FnSig { ref decl, header }, ref generics, ref body) => {
292 let fn_def_id = self.resolver.definitions().local_def_id(id);
293 self.with_new_scopes(|this| {
294 this.current_item = Some(ident.span);
296 // Note: we don't need to change the return type from `T` to
297 // `impl Future<Output = T>` here because lower_body
298 // only cares about the input argument patterns in the function
299 // declaration (decl), not the return types.
301 this.lower_maybe_async_body(span, &decl, header.asyncness.node, Some(body));
303 let (generics, decl) = this.add_in_band_defs(
306 AnonymousLifetimeMode::PassThrough,
310 Some((fn_def_id, idty)),
312 header.asyncness.node.opt_return_id(),
316 let sig = hir::FnSig { decl, header: this.lower_fn_header(header) };
317 hir::ItemKind::Fn(sig, generics, body_id)
320 ItemKind::Mod(ref m) => hir::ItemKind::Mod(self.lower_mod(m)),
321 ItemKind::ForeignMod(ref nm) => hir::ItemKind::ForeignMod(self.lower_foreign_mod(nm)),
322 ItemKind::GlobalAsm(ref ga) => hir::ItemKind::GlobalAsm(self.lower_global_asm(ga)),
323 ItemKind::TyAlias(ref ty, ref generics) => match ty.kind.opaque_top_hack() {
325 let ty = self.lower_ty(ty, ImplTraitContext::disallowed());
326 let generics = self.lower_generics(generics, ImplTraitContext::disallowed());
327 hir::ItemKind::TyAlias(ty, generics)
330 let ty = hir::OpaqueTy {
331 generics: self.lower_generics(generics, ImplTraitContext::OpaqueTy(None)),
332 bounds: self.lower_param_bounds(bounds, ImplTraitContext::OpaqueTy(None)),
334 origin: hir::OpaqueTyOrigin::TypeAlias,
336 hir::ItemKind::OpaqueTy(ty)
339 ItemKind::Enum(ref enum_definition, ref generics) => hir::ItemKind::Enum(
341 variants: self.arena.alloc_from_iter(
342 enum_definition.variants.iter().map(|x| self.lower_variant(x)),
345 self.lower_generics(generics, ImplTraitContext::disallowed()),
347 ItemKind::Struct(ref struct_def, ref generics) => {
348 let struct_def = self.lower_variant_data(struct_def);
349 hir::ItemKind::Struct(
351 self.lower_generics(generics, ImplTraitContext::disallowed()),
354 ItemKind::Union(ref vdata, ref generics) => {
355 let vdata = self.lower_variant_data(vdata);
356 hir::ItemKind::Union(
358 self.lower_generics(generics, ImplTraitContext::disallowed()),
370 let def_id = self.resolver.definitions().local_def_id(id);
372 // Lower the "impl header" first. This ordering is important
373 // for in-band lifetimes! Consider `'a` here:
375 // impl Foo<'a> for u32 {
376 // fn method(&'a self) { .. }
379 // Because we start by lowering the `Foo<'a> for u32`
380 // part, we will add `'a` to the list of generics on
381 // the impl. When we then encounter it later in the
382 // method, it will not be considered an in-band
383 // lifetime to be added, but rather a reference to a
385 let lowered_trait_impl_id = self.lower_node_id(id);
386 let (generics, (trait_ref, lowered_ty)) = self.add_in_band_defs(
389 AnonymousLifetimeMode::CreateParameter,
391 let trait_ref = trait_ref.as_ref().map(|trait_ref| {
392 this.lower_trait_ref(trait_ref, ImplTraitContext::disallowed())
395 if let Some(ref trait_ref) = trait_ref {
396 if let Res::Def(DefKind::Trait, def_id) = trait_ref.path.res {
400 .push(lowered_trait_impl_id);
404 let lowered_ty = this.lower_ty(ty, ImplTraitContext::disallowed());
406 (trait_ref, lowered_ty)
411 self.with_in_scope_lifetime_defs(&ast_generics.params, |this| {
412 this.arena.alloc_from_iter(
413 impl_items.iter().map(|item| this.lower_impl_item_ref(item)),
420 self.lower_defaultness(defaultness, true /* [1] */),
427 ItemKind::Trait(is_auto, unsafety, ref generics, ref bounds, ref items) => {
428 let bounds = self.lower_param_bounds(bounds, ImplTraitContext::disallowed());
431 .alloc_from_iter(items.iter().map(|item| self.lower_trait_item_ref(item)));
432 hir::ItemKind::Trait(
435 self.lower_generics(generics, ImplTraitContext::disallowed()),
440 ItemKind::TraitAlias(ref generics, ref bounds) => hir::ItemKind::TraitAlias(
441 self.lower_generics(generics, ImplTraitContext::disallowed()),
442 self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
444 ItemKind::MacroDef(..) | ItemKind::Mac(..) => {
445 bug!("`TyMac` should have been expanded by now")
449 // [1] `defaultness.has_value()` is never called for an `impl`, always `true` in order to
450 // not cause an assertion failure inside the `lower_defaultness` function.
458 vis: &mut hir::Visibility<'hir>,
460 attrs: &'hir [Attribute],
461 ) -> hir::ItemKind<'hir> {
462 debug!("lower_use_tree(tree={:?})", tree);
463 debug!("lower_use_tree: vis = {:?}", vis);
465 let path = &tree.prefix;
466 let segments = prefix.segments.iter().chain(path.segments.iter()).cloned().collect();
469 UseTreeKind::Simple(rename, id1, id2) => {
470 *ident = tree.ident();
472 // First, apply the prefix to the path.
473 let mut path = Path { segments, span: path.span };
475 // Correctly resolve `self` imports.
476 if path.segments.len() > 1
477 && path.segments.last().unwrap().ident.name == kw::SelfLower
479 let _ = path.segments.pop();
480 if rename.is_none() {
481 *ident = path.segments.last().unwrap().ident;
485 let mut resolutions = self.expect_full_res_from_use(id);
486 // We want to return *something* from this function, so hold onto the first item
488 let ret_res = self.lower_res(resolutions.next().unwrap_or(Res::Err));
490 // Here, we are looping over namespaces, if they exist for the definition
491 // being imported. We only handle type and value namespaces because we
492 // won't be dealing with macros in the rest of the compiler.
493 // Essentially a single `use` which imports two names is desugared into
495 for (res, &new_node_id) in resolutions.zip([id1, id2].iter()) {
497 let mut path = path.clone();
498 for seg in &mut path.segments {
499 seg.id = self.resolver.next_node_id();
501 let span = path.span;
503 self.with_hir_id_owner(new_node_id, |this| {
504 let new_id = this.lower_node_id(new_node_id);
505 let res = this.lower_res(res);
506 let path = this.lower_path_extra(res, &path, ParamMode::Explicit, None);
507 let kind = hir::ItemKind::Use(path, hir::UseKind::Single);
508 let vis = this.rebuild_vis(&vis);
510 this.insert_item(hir::Item {
521 let path = self.lower_path_extra(ret_res, &path, ParamMode::Explicit, None);
522 hir::ItemKind::Use(path, hir::UseKind::Single)
524 UseTreeKind::Glob => {
526 self.lower_path(id, &Path { segments, span: path.span }, ParamMode::Explicit);
527 hir::ItemKind::Use(path, hir::UseKind::Glob)
529 UseTreeKind::Nested(ref trees) => {
530 // Nested imports are desugared into simple imports.
531 // So, if we start with
534 // pub(x) use foo::{a, b};
537 // we will create three items:
540 // pub(x) use foo::a;
541 // pub(x) use foo::b;
542 // pub(x) use foo::{}; // <-- this is called the `ListStem`
545 // The first two are produced by recursively invoking
546 // `lower_use_tree` (and indeed there may be things
547 // like `use foo::{a::{b, c}}` and so forth). They
548 // wind up being directly added to
549 // `self.items`. However, the structure of this
550 // function also requires us to return one item, and
551 // for that we return the `{}` import (called the
554 let prefix = Path { segments, span: prefix.span.to(path.span) };
556 // Add all the nested `PathListItem`s to the HIR.
557 for &(ref use_tree, id) in trees {
558 let new_hir_id = self.lower_node_id(id);
560 let mut prefix = prefix.clone();
562 // Give the segments new node-ids since they are being cloned.
563 for seg in &mut prefix.segments {
564 seg.id = self.resolver.next_node_id();
567 // Each `use` import is an item and thus are owners of the
568 // names in the path. Up to this point the nested import is
569 // the current owner, since we want each desugared import to
570 // own its own names, we have to adjust the owner before
571 // lowering the rest of the import.
572 self.with_hir_id_owner(id, |this| {
573 let mut vis = this.rebuild_vis(&vis);
574 let mut ident = *ident;
577 this.lower_use_tree(use_tree, &prefix, id, &mut vis, &mut ident, attrs);
579 this.insert_item(hir::Item {
590 // Subtle and a bit hacky: we lower the privacy level
591 // of the list stem to "private" most of the time, but
592 // not for "restricted" paths. The key thing is that
593 // we don't want it to stay as `pub` (with no caveats)
594 // because that affects rustdoc and also the lints
595 // about `pub` items. But we can't *always* make it
596 // private -- particularly not for restricted paths --
597 // because it contains node-ids that would then be
598 // unused, failing the check that HirIds are "densely
601 hir::VisibilityKind::Public
602 | hir::VisibilityKind::Crate(_)
603 | hir::VisibilityKind::Inherited => {
604 *vis = respan(prefix.span.shrink_to_lo(), hir::VisibilityKind::Inherited);
606 hir::VisibilityKind::Restricted { .. } => {
607 // Do nothing here, as described in the comment on the match.
611 let res = self.expect_full_res_from_use(id).next().unwrap_or(Res::Err);
612 let res = self.lower_res(res);
613 let path = self.lower_path_extra(res, &prefix, ParamMode::Explicit, None);
614 hir::ItemKind::Use(path, hir::UseKind::ListStem)
619 /// Paths like the visibility path in `pub(super) use foo::{bar, baz}` are repeated
620 /// many times in the HIR tree; for each occurrence, we need to assign distinct
621 /// `NodeId`s. (See, e.g., #56128.)
622 fn rebuild_use_path(&mut self, path: &hir::Path<'hir>) -> &'hir hir::Path<'hir> {
623 debug!("rebuild_use_path(path = {:?})", path);
625 self.arena.alloc_from_iter(path.segments.iter().map(|seg| hir::PathSegment {
627 hir_id: seg.hir_id.map(|_| self.next_id()),
630 infer_args: seg.infer_args,
632 self.arena.alloc(hir::Path { span: path.span, res: path.res, segments })
635 fn rebuild_vis(&mut self, vis: &hir::Visibility<'hir>) -> hir::Visibility<'hir> {
636 let vis_kind = match vis.node {
637 hir::VisibilityKind::Public => hir::VisibilityKind::Public,
638 hir::VisibilityKind::Crate(sugar) => hir::VisibilityKind::Crate(sugar),
639 hir::VisibilityKind::Inherited => hir::VisibilityKind::Inherited,
640 hir::VisibilityKind::Restricted { ref path, hir_id: _ } => {
641 hir::VisibilityKind::Restricted {
642 path: self.rebuild_use_path(path),
643 hir_id: self.next_id(),
647 respan(vis.span, vis_kind)
650 fn lower_foreign_item(&mut self, i: &ForeignItem) -> hir::ForeignItem<'hir> {
651 let def_id = self.resolver.definitions().local_def_id(i.id);
653 hir_id: self.lower_node_id(i.id),
655 attrs: self.lower_attrs(&i.attrs),
657 ForeignItemKind::Fn(ref fdec, ref generics) => {
658 let (generics, (fn_dec, fn_args)) = self.add_in_band_defs(
661 AnonymousLifetimeMode::PassThrough,
664 // Disallow `impl Trait` in foreign items.
665 this.lower_fn_decl(fdec, None, false, None),
666 this.lower_fn_params_to_names(fdec),
671 hir::ForeignItemKind::Fn(fn_dec, fn_args, generics)
673 ForeignItemKind::Static(ref t, m) => {
674 let ty = self.lower_ty(t, ImplTraitContext::disallowed());
675 hir::ForeignItemKind::Static(ty, m)
677 ForeignItemKind::Ty => hir::ForeignItemKind::Type,
678 ForeignItemKind::Macro(_) => panic!("macro shouldn't exist here"),
680 vis: self.lower_visibility(&i.vis, None),
685 fn lower_foreign_mod(&mut self, fm: &ForeignMod) -> hir::ForeignMod<'hir> {
687 abi: fm.abi.map_or(abi::Abi::C, |abi| self.lower_abi(abi)),
688 items: self.arena.alloc_from_iter(fm.items.iter().map(|x| self.lower_foreign_item(x))),
692 fn lower_global_asm(&mut self, ga: &GlobalAsm) -> &'hir hir::GlobalAsm {
693 self.arena.alloc(hir::GlobalAsm { asm: ga.asm })
696 fn lower_variant(&mut self, v: &Variant) -> hir::Variant<'hir> {
698 attrs: self.lower_attrs(&v.attrs),
699 data: self.lower_variant_data(&v.data),
700 disr_expr: v.disr_expr.as_ref().map(|e| self.lower_anon_const(e)),
701 id: self.lower_node_id(v.id),
707 fn lower_variant_data(&mut self, vdata: &VariantData) -> hir::VariantData<'hir> {
709 VariantData::Struct(ref fields, recovered) => hir::VariantData::Struct(
711 .alloc_from_iter(fields.iter().enumerate().map(|f| self.lower_struct_field(f))),
714 VariantData::Tuple(ref fields, id) => hir::VariantData::Tuple(
716 .alloc_from_iter(fields.iter().enumerate().map(|f| self.lower_struct_field(f))),
717 self.lower_node_id(id),
719 VariantData::Unit(id) => hir::VariantData::Unit(self.lower_node_id(id)),
723 fn lower_struct_field(&mut self, (index, f): (usize, &StructField)) -> hir::StructField<'hir> {
724 let ty = if let TyKind::Path(ref qself, ref path) = f.ty.kind {
725 let t = self.lower_path_ty(
729 ParamMode::ExplicitNamed, // no `'_` in declarations (Issue #61124)
730 ImplTraitContext::disallowed(),
734 self.lower_ty(&f.ty, ImplTraitContext::disallowed())
738 hir_id: self.lower_node_id(f.id),
739 ident: match f.ident {
740 Some(ident) => ident,
741 // FIXME(jseyfried): positional field hygiene.
742 None => Ident::new(sym::integer(index), f.span),
744 vis: self.lower_visibility(&f.vis, None),
746 attrs: self.lower_attrs(&f.attrs),
750 fn lower_trait_item(&mut self, i: &AssocItem) -> hir::TraitItem<'hir> {
751 let trait_item_def_id = self.resolver.definitions().local_def_id(i.id);
753 let (generics, kind) = match i.kind {
754 AssocItemKind::Const(ref ty, ref default) => {
755 let generics = self.lower_generics(&i.generics, ImplTraitContext::disallowed());
756 let ty = self.lower_ty(ty, ImplTraitContext::disallowed());
759 hir::TraitItemKind::Const(
761 default.as_ref().map(|x| self.lower_const_body(i.span, Some(x))),
765 AssocItemKind::Fn(ref sig, None) => {
766 let names = self.lower_fn_params_to_names(&sig.decl);
767 let (generics, sig) =
768 self.lower_method_sig(&i.generics, sig, trait_item_def_id, false, None);
769 (generics, hir::TraitItemKind::Method(sig, hir::TraitMethod::Required(names)))
771 AssocItemKind::Fn(ref sig, Some(ref body)) => {
772 let body_id = self.lower_fn_body_block(i.span, &sig.decl, Some(body));
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::Provided(body_id)))
777 AssocItemKind::TyAlias(ref bounds, ref default) => {
778 let ty = default.as_ref().map(|x| self.lower_ty(x, ImplTraitContext::disallowed()));
779 let generics = self.lower_generics(&i.generics, ImplTraitContext::disallowed());
780 let kind = hir::TraitItemKind::Type(
781 self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
787 AssocItemKind::Macro(..) => bug!("macro item shouldn't exist at this point"),
791 hir_id: self.lower_node_id(i.id),
793 attrs: self.lower_attrs(&i.attrs),
800 fn lower_trait_item_ref(&mut self, i: &AssocItem) -> hir::TraitItemRef {
801 let (kind, has_default) = match i.kind {
802 AssocItemKind::Const(_, ref default) => (hir::AssocItemKind::Const, default.is_some()),
803 AssocItemKind::TyAlias(_, ref default) => (hir::AssocItemKind::Type, default.is_some()),
804 AssocItemKind::Fn(ref sig, ref default) => {
805 (hir::AssocItemKind::Method { has_self: sig.decl.has_self() }, default.is_some())
807 AssocItemKind::Macro(..) => unimplemented!(),
810 id: hir::TraitItemId { hir_id: self.lower_node_id(i.id) },
813 defaultness: self.lower_defaultness(Defaultness::Default, has_default),
818 /// Construct `ExprKind::Err` for the given `span`.
819 fn expr_err(&mut self, span: Span) -> hir::Expr<'hir> {
820 self.expr(span, hir::ExprKind::Err, AttrVec::new())
823 fn lower_impl_item(&mut self, i: &AssocItem) -> hir::ImplItem<'hir> {
824 let impl_item_def_id = self.resolver.definitions().local_def_id(i.id);
826 let (generics, kind) = match i.kind {
827 AssocItemKind::Const(ref ty, ref expr) => {
828 let generics = self.lower_generics(&i.generics, ImplTraitContext::disallowed());
829 let ty = self.lower_ty(ty, ImplTraitContext::disallowed());
832 hir::ImplItemKind::Const(ty, self.lower_const_body(i.span, expr.as_deref())),
835 AssocItemKind::Fn(ref sig, ref body) => {
836 self.current_item = Some(i.span);
837 let body_id = self.lower_maybe_async_body(
840 sig.header.asyncness.node,
843 let impl_trait_return_allow = !self.is_in_trait_impl;
844 let (generics, sig) = self.lower_method_sig(
848 impl_trait_return_allow,
849 sig.header.asyncness.node.opt_return_id(),
852 (generics, hir::ImplItemKind::Method(sig, body_id))
854 AssocItemKind::TyAlias(_, ref ty) => {
855 let generics = self.lower_generics(&i.generics, ImplTraitContext::disallowed());
856 let kind = match ty {
858 let ty = self.arena.alloc(self.ty(i.span, hir::TyKind::Err));
859 hir::ImplItemKind::TyAlias(ty)
861 Some(ty) => match ty.kind.opaque_top_hack() {
863 let ty = self.lower_ty(ty, ImplTraitContext::disallowed());
864 hir::ImplItemKind::TyAlias(ty)
867 let bs = self.lower_param_bounds(bs, ImplTraitContext::disallowed());
868 hir::ImplItemKind::OpaqueTy(bs)
874 AssocItemKind::Macro(..) => bug!("`TyMac` should have been expanded by now"),
878 hir_id: self.lower_node_id(i.id),
880 attrs: self.lower_attrs(&i.attrs),
882 vis: self.lower_visibility(&i.vis, None),
883 defaultness: self.lower_defaultness(i.defaultness, true /* [1] */),
888 // [1] since `default impl` is not yet implemented, this is always true in impls
891 fn lower_impl_item_ref(&mut self, i: &AssocItem) -> hir::ImplItemRef<'hir> {
893 id: hir::ImplItemId { hir_id: self.lower_node_id(i.id) },
896 vis: self.lower_visibility(&i.vis, Some(i.id)),
897 defaultness: self.lower_defaultness(i.defaultness, true /* [1] */),
898 kind: match &i.kind {
899 AssocItemKind::Const(..) => hir::AssocItemKind::Const,
900 AssocItemKind::TyAlias(_, ty) => {
901 match ty.as_deref().and_then(|ty| ty.kind.opaque_top_hack()) {
902 None => hir::AssocItemKind::Type,
903 Some(_) => hir::AssocItemKind::OpaqueTy,
906 AssocItemKind::Fn(sig, _) => {
907 hir::AssocItemKind::Method { has_self: sig.decl.has_self() }
909 AssocItemKind::Macro(..) => unimplemented!(),
913 // [1] since `default impl` is not yet implemented, this is always true in impls
916 /// If an `explicit_owner` is given, this method allocates the `HirId` in
917 /// the address space of that item instead of the item currently being
918 /// lowered. This can happen during `lower_impl_item_ref()` where we need to
919 /// lower a `Visibility` value although we haven't lowered the owning
920 /// `ImplItem` in question yet.
924 explicit_owner: Option<NodeId>,
925 ) -> hir::Visibility<'hir> {
926 let node = match v.node {
927 VisibilityKind::Public => hir::VisibilityKind::Public,
928 VisibilityKind::Crate(sugar) => hir::VisibilityKind::Crate(sugar),
929 VisibilityKind::Restricted { ref path, id } => {
930 debug!("lower_visibility: restricted path id = {:?}", id);
931 let lowered_id = if let Some(owner) = explicit_owner {
932 self.lower_node_id_with_owner(id, owner)
934 self.lower_node_id(id)
936 let res = self.expect_full_res(id);
937 let res = self.lower_res(res);
938 hir::VisibilityKind::Restricted {
939 path: self.lower_path_extra(res, path, ParamMode::Explicit, explicit_owner),
943 VisibilityKind::Inherited => hir::VisibilityKind::Inherited,
948 fn lower_defaultness(&self, d: Defaultness, has_value: bool) -> hir::Defaultness {
950 Defaultness::Default => hir::Defaultness::Default { has_value: has_value },
951 Defaultness::Final => {
953 hir::Defaultness::Final
960 params: &'hir [hir::Param<'hir>],
961 value: hir::Expr<'hir>,
963 let body = hir::Body { generator_kind: self.generator_kind, params, value };
965 self.bodies.insert(id, body);
971 f: impl FnOnce(&mut Self) -> (&'hir [hir::Param<'hir>], hir::Expr<'hir>),
973 let prev_gen_kind = self.generator_kind.take();
974 let (parameters, result) = f(self);
975 let body_id = self.record_body(parameters, result);
976 self.generator_kind = prev_gen_kind;
980 fn lower_param(&mut self, param: &Param) -> hir::Param<'hir> {
982 attrs: self.lower_attrs(¶m.attrs),
983 hir_id: self.lower_node_id(param.id),
984 pat: self.lower_pat(¶m.pat),
989 pub(super) fn lower_fn_body(
992 body: impl FnOnce(&mut Self) -> hir::Expr<'hir>,
994 self.lower_body(|this| {
996 this.arena.alloc_from_iter(decl.inputs.iter().map(|x| this.lower_param(x))),
1002 fn lower_fn_body_block(
1006 body: Option<&Block>,
1008 self.lower_fn_body(decl, |this| this.lower_block_expr_opt(span, body))
1011 fn lower_block_expr_opt(&mut self, span: Span, block: Option<&Block>) -> hir::Expr<'hir> {
1013 Some(block) => self.lower_block_expr(block),
1014 None => self.expr_err(span),
1018 pub(super) fn lower_const_body(&mut self, span: Span, expr: Option<&Expr>) -> hir::BodyId {
1019 self.lower_body(|this| {
1023 Some(expr) => this.lower_expr_mut(expr),
1024 None => this.expr_err(span),
1030 fn lower_maybe_async_body(
1035 body: Option<&Block>,
1037 let closure_id = match asyncness {
1038 IsAsync::Async { closure_id, .. } => closure_id,
1039 IsAsync::NotAsync => return self.lower_fn_body_block(span, decl, body),
1042 self.lower_body(|this| {
1043 let mut parameters: Vec<hir::Param<'_>> = Vec::new();
1044 let mut statements: Vec<hir::Stmt<'_>> = Vec::new();
1046 // Async function parameters are lowered into the closure body so that they are
1047 // captured and so that the drop order matches the equivalent non-async functions.
1051 // async fn foo(<pattern>: <ty>, <pattern>: <ty>, <pattern>: <ty>) {
1057 // fn foo(__arg0: <ty>, __arg1: <ty>, __arg2: <ty>) {
1059 // let __arg2 = __arg2;
1060 // let <pattern> = __arg2;
1061 // let __arg1 = __arg1;
1062 // let <pattern> = __arg1;
1063 // let __arg0 = __arg0;
1064 // let <pattern> = __arg0;
1065 // drop-temps { <body> } // see comments later in fn for details
1069 // If `<pattern>` is a simple ident, then it is lowered to a single
1070 // `let <pattern> = <pattern>;` statement as an optimization.
1072 // Note that the body is embedded in `drop-temps`; an
1073 // equivalent desugaring would be `return { <body>
1074 // };`. The key point is that we wish to drop all the
1075 // let-bound variables and temporaries created in the body
1076 // (and its tail expression!) before we drop the
1077 // parameters (c.f. rust-lang/rust#64512).
1078 for (index, parameter) in decl.inputs.iter().enumerate() {
1079 let parameter = this.lower_param(parameter);
1080 let span = parameter.pat.span;
1082 // Check if this is a binding pattern, if so, we can optimize and avoid adding a
1083 // `let <pat> = __argN;` statement. In this case, we do not rename the parameter.
1084 let (ident, is_simple_parameter) = match parameter.pat.kind {
1085 hir::PatKind::Binding(hir::BindingAnnotation::Unannotated, _, ident, _) => {
1089 // Replace the ident for bindings that aren't simple.
1090 let name = format!("__arg{}", index);
1091 let ident = Ident::from_str(&name);
1097 let desugared_span = this.mark_span_with_reason(DesugaringKind::Async, span, None);
1099 // Construct a parameter representing `__argN: <ty>` to replace the parameter of the
1102 // If this is the simple case, this parameter will end up being the same as the
1103 // original parameter, but with a different pattern id.
1104 let mut stmt_attrs = AttrVec::new();
1105 stmt_attrs.extend(parameter.attrs.iter().cloned());
1106 let (new_parameter_pat, new_parameter_id) = this.pat_ident(desugared_span, ident);
1107 let new_parameter = hir::Param {
1108 attrs: parameter.attrs,
1109 hir_id: parameter.hir_id,
1110 pat: new_parameter_pat,
1111 span: parameter.span,
1114 if is_simple_parameter {
1115 // If this is the simple case, then we only insert one statement that is
1116 // `let <pat> = <pat>;`. We re-use the original argument's pattern so that
1117 // `HirId`s are densely assigned.
1118 let expr = this.expr_ident(desugared_span, ident, new_parameter_id);
1119 let stmt = this.stmt_let_pat(
1124 hir::LocalSource::AsyncFn,
1126 statements.push(stmt);
1128 // If this is not the simple case, then we construct two statements:
1131 // let __argN = __argN;
1132 // let <pat> = __argN;
1135 // The first statement moves the parameter into the closure and thus ensures
1136 // that the drop order is correct.
1138 // The second statement creates the bindings that the user wrote.
1140 // Construct the `let mut __argN = __argN;` statement. It must be a mut binding
1141 // because the user may have specified a `ref mut` binding in the next
1143 let (move_pat, move_id) = this.pat_ident_binding_mode(
1146 hir::BindingAnnotation::Mutable,
1148 let move_expr = this.expr_ident(desugared_span, ident, new_parameter_id);
1149 let move_stmt = this.stmt_let_pat(
1154 hir::LocalSource::AsyncFn,
1157 // Construct the `let <pat> = __argN;` statement. We re-use the original
1158 // parameter's pattern so that `HirId`s are densely assigned.
1159 let pattern_expr = this.expr_ident(desugared_span, ident, move_id);
1160 let pattern_stmt = this.stmt_let_pat(
1165 hir::LocalSource::AsyncFn,
1168 statements.push(move_stmt);
1169 statements.push(pattern_stmt);
1172 parameters.push(new_parameter);
1175 let body_span = body.map_or(span, |b| b.span);
1176 let async_expr = this.make_async_expr(
1181 hir::AsyncGeneratorKind::Fn,
1183 // Create a block from the user's function body:
1184 let user_body = this.lower_block_expr_opt(body_span, body);
1186 // Transform into `drop-temps { <user-body> }`, an expression:
1187 let desugared_span =
1188 this.mark_span_with_reason(DesugaringKind::Async, user_body.span, None);
1189 let user_body = this.expr_drop_temps(
1191 this.arena.alloc(user_body),
1195 // As noted above, create the final block like
1199 // let $param_pattern = $raw_param;
1201 // drop-temps { <user-body> }
1204 let body = this.block_all(
1206 this.arena.alloc_from_iter(statements),
1210 this.expr_block(body, AttrVec::new())
1215 this.arena.alloc_from_iter(parameters),
1216 this.expr(body_span, async_expr, AttrVec::new()),
1221 fn lower_method_sig(
1223 generics: &Generics,
1226 impl_trait_return_allow: bool,
1227 is_async: Option<NodeId>,
1228 ) -> (hir::Generics<'hir>, hir::FnSig<'hir>) {
1229 let header = self.lower_fn_header(sig.header);
1230 let (generics, decl) = self.add_in_band_defs(
1233 AnonymousLifetimeMode::PassThrough,
1237 Some((fn_def_id, idty)),
1238 impl_trait_return_allow,
1243 (generics, hir::FnSig { header, decl })
1246 fn lower_fn_header(&mut self, h: FnHeader) -> hir::FnHeader {
1248 unsafety: h.unsafety,
1249 asyncness: self.lower_asyncness(h.asyncness.node),
1250 constness: h.constness.node,
1251 abi: self.lower_extern(h.ext),
1255 pub(super) fn lower_abi(&mut self, abi: StrLit) -> abi::Abi {
1256 abi::lookup(&abi.symbol_unescaped.as_str()).unwrap_or_else(|| {
1257 self.error_on_invalid_abi(abi);
1262 pub(super) fn lower_extern(&mut self, ext: Extern) -> abi::Abi {
1264 Extern::None => abi::Abi::Rust,
1265 Extern::Implicit => abi::Abi::C,
1266 Extern::Explicit(abi) => self.lower_abi(abi),
1270 fn error_on_invalid_abi(&self, abi: StrLit) {
1271 struct_span_err!(self.sess, abi.span, E0703, "invalid ABI: found `{}`", abi.symbol)
1272 .span_label(abi.span, "invalid ABI")
1273 .help(&format!("valid ABIs: {}", abi::all_names().join(", ")))
1277 fn lower_asyncness(&mut self, a: IsAsync) -> hir::IsAsync {
1279 IsAsync::Async { .. } => hir::IsAsync::Async,
1280 IsAsync::NotAsync => hir::IsAsync::NotAsync,
1284 pub(super) fn lower_generics_mut(
1286 generics: &Generics,
1287 itctx: ImplTraitContext<'_, 'hir>,
1288 ) -> GenericsCtor<'hir> {
1289 // Collect `?Trait` bounds in where clause and move them to parameter definitions.
1290 // FIXME: this could probably be done with less rightward drift. It also looks like two
1291 // control paths where `report_error` is called are the only paths that advance to after the
1292 // match statement, so the error reporting could probably just be moved there.
1293 let mut add_bounds: NodeMap<Vec<_>> = Default::default();
1294 for pred in &generics.where_clause.predicates {
1295 if let WherePredicate::BoundPredicate(ref bound_pred) = *pred {
1296 'next_bound: for bound in &bound_pred.bounds {
1297 if let GenericBound::Trait(_, TraitBoundModifier::Maybe) = *bound {
1298 let report_error = |this: &mut Self| {
1299 this.diagnostic().span_err(
1300 bound_pred.bounded_ty.span,
1301 "`?Trait` bounds are only permitted at the \
1302 point where a type parameter is declared",
1305 // Check if the where clause type is a plain type parameter.
1306 match bound_pred.bounded_ty.kind {
1307 TyKind::Path(None, ref path)
1308 if path.segments.len() == 1
1309 && bound_pred.bound_generic_params.is_empty() =>
1311 if let Some(Res::Def(DefKind::TyParam, def_id)) = self
1313 .get_partial_res(bound_pred.bounded_ty.id)
1314 .map(|d| d.base_res())
1316 if let Some(node_id) =
1317 self.resolver.definitions().as_local_node_id(def_id)
1319 for param in &generics.params {
1321 GenericParamKind::Type { .. } => {
1322 if node_id == param.id {
1326 .push(bound.clone());
1327 continue 'next_bound;
1337 _ => report_error(self),
1345 params: self.lower_generic_params_mut(&generics.params, &add_bounds, itctx).collect(),
1346 where_clause: self.lower_where_clause(&generics.where_clause),
1347 span: generics.span,
1351 pub(super) fn lower_generics(
1353 generics: &Generics,
1354 itctx: ImplTraitContext<'_, 'hir>,
1355 ) -> hir::Generics<'hir> {
1356 let generics_ctor = self.lower_generics_mut(generics, itctx);
1357 generics_ctor.into_generics(self.arena)
1360 fn lower_where_clause(&mut self, wc: &WhereClause) -> hir::WhereClause<'hir> {
1361 self.with_anonymous_lifetime_mode(AnonymousLifetimeMode::ReportError, |this| {
1363 predicates: this.arena.alloc_from_iter(
1364 wc.predicates.iter().map(|predicate| this.lower_where_predicate(predicate)),
1371 fn lower_where_predicate(&mut self, pred: &WherePredicate) -> hir::WherePredicate<'hir> {
1373 WherePredicate::BoundPredicate(WhereBoundPredicate {
1374 ref bound_generic_params,
1379 self.with_in_scope_lifetime_defs(&bound_generic_params, |this| {
1380 hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
1381 bound_generic_params: this.lower_generic_params(
1382 bound_generic_params,
1383 &NodeMap::default(),
1384 ImplTraitContext::disallowed(),
1386 bounded_ty: this.lower_ty(bounded_ty, ImplTraitContext::disallowed()),
1387 bounds: this.arena.alloc_from_iter(bounds.iter().filter_map(|bound| {
1389 // Ignore `?Trait` bounds.
1390 // They were copied into type parameters already.
1391 GenericBound::Trait(_, TraitBoundModifier::Maybe) => None,
1393 this.lower_param_bound(bound, ImplTraitContext::disallowed()),
1401 WherePredicate::RegionPredicate(WhereRegionPredicate {
1405 }) => hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate {
1407 lifetime: self.lower_lifetime(lifetime),
1408 bounds: self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
1410 WherePredicate::EqPredicate(WhereEqPredicate { id, ref lhs_ty, ref rhs_ty, span }) => {
1411 hir::WherePredicate::EqPredicate(hir::WhereEqPredicate {
1412 hir_id: self.lower_node_id(id),
1413 lhs_ty: self.lower_ty(lhs_ty, ImplTraitContext::disallowed()),
1414 rhs_ty: self.lower_ty(rhs_ty, ImplTraitContext::disallowed()),
1422 /// Helper struct for delayed construction of Generics.
1423 pub(super) struct GenericsCtor<'hir> {
1424 pub(super) params: SmallVec<[hir::GenericParam<'hir>; 4]>,
1425 where_clause: hir::WhereClause<'hir>,
1429 impl<'hir> GenericsCtor<'hir> {
1430 pub(super) fn into_generics(self, arena: &'hir Arena<'hir>) -> hir::Generics<'hir> {
1432 params: arena.alloc_from_iter(self.params),
1433 where_clause: self.where_clause,