1 use super::{AnonymousLifetimeMode, LoweringContext, ParamMode};
2 use super::{ImplTraitContext, ImplTraitPosition};
5 use rustc_ast::node_id::NodeMap;
7 use rustc_ast::visit::{self, AssocCtxt, FnCtxt, FnKind, Visitor};
9 use rustc_data_structures::fx::FxHashSet;
10 use rustc_errors::struct_span_err;
12 use rustc_hir::def::{DefKind, Res};
13 use rustc_hir::def_id::LocalDefId;
14 use rustc_span::source_map::{respan, DesugaringKind};
15 use rustc_span::symbol::{kw, sym, Ident};
17 use rustc_target::spec::abi;
18 use smallvec::{smallvec, SmallVec};
24 pub(super) struct ItemLowerer<'a, 'lowering, 'hir> {
25 pub(super) lctx: &'a mut LoweringContext<'lowering, 'hir>,
28 impl ItemLowerer<'_, '_, '_> {
29 fn with_trait_impl_ref<T>(
31 impl_ref: &Option<TraitRef>,
32 f: impl FnOnce(&mut Self) -> T,
34 let old = self.lctx.is_in_trait_impl;
35 self.lctx.is_in_trait_impl = impl_ref.is_some();
37 self.lctx.is_in_trait_impl = old;
42 impl<'a> Visitor<'a> for ItemLowerer<'a, '_, '_> {
43 fn visit_item(&mut self, item: &'a Item) {
44 let hir_id = self.lctx.with_hir_id_owner(item.id, |lctx| {
45 lctx.without_in_scope_lifetime_defs(|lctx| {
46 let hir_item = lctx.lower_item(item);
47 lctx.insert_item(hir_item)
51 self.lctx.with_parent_item_lifetime_defs(hir_id, |this| {
52 let this = &mut ItemLowerer { lctx: this };
54 ItemKind::Mod(..) => {
55 let def_id = this.lctx.lower_node_id(item.id).expect_owner();
56 let old_current_module = mem::replace(&mut this.lctx.current_module, def_id);
57 visit::walk_item(this, item);
58 this.lctx.current_module = old_current_module;
60 ItemKind::Impl(box ImplKind { ref of_trait, .. }) => {
61 this.with_trait_impl_ref(of_trait, |this| visit::walk_item(this, item));
63 _ => visit::walk_item(this, item),
68 fn visit_fn(&mut self, fk: FnKind<'a>, sp: Span, _: NodeId) {
70 FnKind::Fn(FnCtxt::Foreign, _, sig, _, _) => {
71 self.visit_fn_header(&sig.header);
72 visit::walk_fn_decl(self, &sig.decl);
73 // Don't visit the foreign function body even if it has one, since lowering the
74 // body would have no meaning and will have already been caught as a parse error.
76 _ => visit::walk_fn(self, fk, sp),
80 fn visit_assoc_item(&mut self, item: &'a AssocItem, ctxt: AssocCtxt) {
81 self.lctx.with_hir_id_owner(item.id, |lctx| match ctxt {
83 let hir_item = lctx.lower_trait_item(item);
84 lctx.insert_trait_item(hir_item);
87 let hir_item = lctx.lower_impl_item(item);
88 lctx.insert_impl_item(hir_item);
92 visit::walk_assoc_item(self, item, ctxt);
95 fn visit_foreign_item(&mut self, item: &'a ForeignItem) {
96 self.lctx.allocate_hir_id_counter(item.id);
97 self.lctx.with_hir_id_owner(item.id, |lctx| {
98 let hir_item = lctx.lower_foreign_item(item);
99 lctx.insert_foreign_item(hir_item);
102 visit::walk_foreign_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::ItemId,
115 f: impl FnOnce(&mut Self) -> T,
117 let old_len = self.in_scope_lifetimes.len();
119 let parent_generics = match self.owners[parent_hir_id.def_id].unwrap().expect_item().kind {
120 hir::ItemKind::Impl(hir::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.normalize_to_macros_2_0()),
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>(&mut self, f: impl FnOnce(&mut Self) -> T) -> T {
140 let old_in_scope_lifetimes = mem::replace(&mut self.in_scope_lifetimes, vec![]);
142 // this vector is only used when walking over impl headers,
143 // input types, and the like, and should not be non-empty in
145 assert!(self.lifetimes_to_define.is_empty());
149 assert!(self.in_scope_lifetimes.is_empty());
150 self.in_scope_lifetimes = old_in_scope_lifetimes;
155 pub(super) fn lower_mod(&mut self, items: &[P<Item>], inner: Span) -> hir::Mod<'hir> {
157 inner: self.lower_span(inner),
158 item_ids: self.arena.alloc_from_iter(items.iter().flat_map(|x| self.lower_item_id(x))),
162 pub(super) fn lower_item_id(&mut self, i: &Item) -> SmallVec<[hir::ItemId; 1]> {
163 let node_ids = match i.kind {
164 ItemKind::Use(ref use_tree) => {
165 let mut vec = smallvec![i.id];
166 self.lower_item_id_use_tree(use_tree, i.id, &mut vec);
169 ItemKind::Fn(..) | ItemKind::Impl(box ImplKind { of_trait: None, .. }) => {
172 _ => smallvec![i.id],
177 .map(|node_id| hir::ItemId {
178 def_id: self.allocate_hir_id_counter(node_id).expect_owner(),
183 fn lower_item_id_use_tree(
187 vec: &mut SmallVec<[NodeId; 1]>,
190 UseTreeKind::Nested(ref nested_vec) => {
191 for &(ref nested, id) in nested_vec {
193 self.lower_item_id_use_tree(nested, id, vec);
196 UseTreeKind::Glob => {}
197 UseTreeKind::Simple(_, id1, id2) => {
199 iter::zip(self.expect_full_res_from_use(base_id).skip(1), &[id1, id2])
207 pub fn lower_item(&mut self, i: &Item) -> hir::Item<'hir> {
208 let mut ident = i.ident;
209 let mut vis = self.lower_visibility(&i.vis, None);
210 let hir_id = self.lower_node_id(i.id);
211 let attrs = self.lower_attrs(hir_id, &i.attrs);
212 let kind = self.lower_item_kind(i.span, i.id, hir_id, &mut ident, attrs, &mut vis, &i.kind);
214 def_id: hir_id.expect_owner(),
215 ident: self.lower_ident(ident),
218 span: self.lower_span(i.span),
228 attrs: Option<&'hir [Attribute]>,
229 vis: &mut hir::Visibility<'hir>,
231 ) -> hir::ItemKind<'hir> {
233 ItemKind::ExternCrate(orig_name) => hir::ItemKind::ExternCrate(orig_name),
234 ItemKind::Use(ref use_tree) => {
235 // Start with an empty prefix.
236 let prefix = Path { segments: vec![], span: use_tree.span, tokens: None };
238 self.lower_use_tree(use_tree, &prefix, id, vis, ident, attrs)
240 ItemKind::Static(ref t, m, ref e) => {
241 let (ty, body_id) = self.lower_const_item(t, span, e.as_deref());
242 hir::ItemKind::Static(ty, m, body_id)
244 ItemKind::Const(_, ref t, ref e) => {
245 let (ty, body_id) = self.lower_const_item(t, span, e.as_deref());
246 hir::ItemKind::Const(ty, body_id)
248 ItemKind::Fn(box FnKind(
250 FnSig { ref decl, header, span: fn_sig_span },
254 let fn_def_id = self.resolver.local_def_id(id);
255 self.with_new_scopes(|this| {
256 this.current_item = Some(ident.span);
258 // Note: we don't need to change the return type from `T` to
259 // `impl Future<Output = T>` here because lower_body
260 // only cares about the input argument patterns in the function
261 // declaration (decl), not the return types.
262 let asyncness = header.asyncness;
264 this.lower_maybe_async_body(span, &decl, asyncness, body.as_deref());
266 let (generics, decl) = this.add_in_band_defs(
269 AnonymousLifetimeMode::PassThrough,
271 let ret_id = asyncness.opt_return_id();
274 Some((fn_def_id.to_def_id(), idty)),
280 let sig = hir::FnSig {
282 header: this.lower_fn_header(header, fn_sig_span, id),
283 span: this.lower_span(fn_sig_span),
285 hir::ItemKind::Fn(sig, generics, body_id)
288 ItemKind::Mod(_, ref mod_kind) => match mod_kind {
289 ModKind::Loaded(items, _, inner_span) => {
290 hir::ItemKind::Mod(self.lower_mod(items, *inner_span))
292 ModKind::Unloaded => panic!("`mod` items should have been loaded by now"),
294 ItemKind::ForeignMod(ref fm) => {
295 if fm.abi.is_none() {
296 self.maybe_lint_missing_abi(span, id, abi::Abi::C { unwind: false });
298 hir::ItemKind::ForeignMod {
299 abi: fm.abi.map_or(abi::Abi::C { unwind: false }, |abi| self.lower_abi(abi)),
302 .alloc_from_iter(fm.items.iter().map(|x| self.lower_foreign_item_ref(x))),
305 ItemKind::GlobalAsm(ref asm) => {
306 hir::ItemKind::GlobalAsm(self.lower_inline_asm(span, asm))
308 ItemKind::TyAlias(box TyAliasKind(_, ref gen, _, Some(ref ty))) => {
311 // type Foo = impl Trait
316 // opaque type Foo1: Trait
317 let ty = self.lower_ty(
319 ImplTraitContext::TypeAliasesOpaqueTy {
320 capturable_lifetimes: &mut FxHashSet::default(),
323 let generics = self.lower_generics(gen, ImplTraitContext::disallowed());
324 hir::ItemKind::TyAlias(ty, generics)
326 ItemKind::TyAlias(box TyAliasKind(_, ref generics, _, None)) => {
327 let ty = self.arena.alloc(self.ty(span, hir::TyKind::Err));
328 let generics = self.lower_generics(generics, ImplTraitContext::disallowed());
329 hir::ItemKind::TyAlias(ty, generics)
331 ItemKind::Enum(ref enum_definition, ref generics) => hir::ItemKind::Enum(
333 variants: self.arena.alloc_from_iter(
334 enum_definition.variants.iter().map(|x| self.lower_variant(x)),
337 self.lower_generics(generics, ImplTraitContext::disallowed()),
339 ItemKind::Struct(ref struct_def, ref generics) => {
340 let struct_def = self.lower_variant_data(hir_id, struct_def);
341 hir::ItemKind::Struct(
343 self.lower_generics(generics, ImplTraitContext::disallowed()),
346 ItemKind::Union(ref vdata, ref generics) => {
347 let vdata = self.lower_variant_data(hir_id, vdata);
348 hir::ItemKind::Union(
350 self.lower_generics(generics, ImplTraitContext::disallowed()),
353 ItemKind::Impl(box ImplKind {
358 generics: ref ast_generics,
359 of_trait: ref trait_ref,
361 items: ref impl_items,
363 // Lower the "impl header" first. This ordering is important
364 // for in-band lifetimes! Consider `'a` here:
366 // impl Foo<'a> for u32 {
367 // fn method(&'a self) { .. }
370 // Because we start by lowering the `Foo<'a> for u32`
371 // part, we will add `'a` to the list of generics on
372 // the impl. When we then encounter it later in the
373 // method, it will not be considered an in-band
374 // lifetime to be added, but rather a reference to a
376 let lowered_trait_def_id = self.lower_node_id(id).expect_owner();
377 let (generics, (trait_ref, lowered_ty)) = self.add_in_band_defs(
379 lowered_trait_def_id,
380 AnonymousLifetimeMode::CreateParameter,
382 let trait_ref = trait_ref.as_ref().map(|trait_ref| {
383 this.lower_trait_ref(trait_ref, ImplTraitContext::disallowed())
386 if let Some(ref trait_ref) = trait_ref {
387 if let Res::Def(DefKind::Trait, def_id) = trait_ref.path.res {
391 .push(lowered_trait_def_id);
395 let lowered_ty = this.lower_ty(ty, ImplTraitContext::disallowed());
397 (trait_ref, lowered_ty)
402 self.with_in_scope_lifetime_defs(&ast_generics.params, |this| {
403 this.arena.alloc_from_iter(
404 impl_items.iter().map(|item| this.lower_impl_item_ref(item)),
408 // `defaultness.has_value()` is never called for an `impl`, always `true` in order
409 // to not cause an assertion failure inside the `lower_defaultness` function.
411 let (defaultness, defaultness_span) = self.lower_defaultness(defaultness, has_val);
412 let polarity = match polarity {
413 ImplPolarity::Positive => ImplPolarity::Positive,
414 ImplPolarity::Negative(s) => ImplPolarity::Negative(self.lower_span(s)),
416 hir::ItemKind::Impl(hir::Impl {
417 unsafety: self.lower_unsafety(unsafety),
421 constness: self.lower_constness(constness),
425 items: new_impl_items,
428 ItemKind::Trait(box TraitKind(
435 let bounds = self.lower_param_bounds(bounds, ImplTraitContext::disallowed());
438 .alloc_from_iter(items.iter().map(|item| self.lower_trait_item_ref(item)));
439 hir::ItemKind::Trait(
441 self.lower_unsafety(unsafety),
442 self.lower_generics(generics, ImplTraitContext::disallowed()),
447 ItemKind::TraitAlias(ref generics, ref bounds) => hir::ItemKind::TraitAlias(
448 self.lower_generics(generics, ImplTraitContext::disallowed()),
449 self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
451 ItemKind::MacroDef(MacroDef { ref body, macro_rules }) => {
452 let body = P(self.lower_mac_args(body));
454 hir::ItemKind::Macro(ast::MacroDef { body, macro_rules })
456 ItemKind::MacCall(..) => {
457 panic!("`TyMac` should have been expanded by now")
467 ) -> (&'hir hir::Ty<'hir>, hir::BodyId) {
468 let ty = self.lower_ty(ty, ImplTraitContext::Disallowed(ImplTraitPosition::Binding));
469 (ty, self.lower_const_body(span, body))
477 vis: &mut hir::Visibility<'hir>,
479 attrs: Option<&'hir [Attribute]>,
480 ) -> hir::ItemKind<'hir> {
481 debug!("lower_use_tree(tree={:?})", tree);
482 debug!("lower_use_tree: vis = {:?}", vis);
484 let path = &tree.prefix;
485 let segments = prefix.segments.iter().chain(path.segments.iter()).cloned().collect();
488 UseTreeKind::Simple(rename, id1, id2) => {
489 *ident = tree.ident();
491 // First, apply the prefix to the path.
492 let mut path = Path { segments, span: path.span, tokens: None };
494 // Correctly resolve `self` imports.
495 if path.segments.len() > 1
496 && path.segments.last().unwrap().ident.name == kw::SelfLower
498 let _ = path.segments.pop();
499 if rename.is_none() {
500 *ident = path.segments.last().unwrap().ident;
504 let mut resolutions = self.expect_full_res_from_use(id);
505 // We want to return *something* from this function, so hold onto the first item
507 let ret_res = self.lower_res(resolutions.next().unwrap_or(Res::Err));
509 // Here, we are looping over namespaces, if they exist for the definition
510 // being imported. We only handle type and value namespaces because we
511 // won't be dealing with macros in the rest of the compiler.
512 // Essentially a single `use` which imports two names is desugared into
514 for (res, &new_node_id) in iter::zip(resolutions, &[id1, id2]) {
516 let mut path = path.clone();
517 for seg in &mut path.segments {
518 seg.id = self.resolver.next_node_id();
520 let span = path.span;
522 self.with_hir_id_owner(new_node_id, |this| {
523 let new_id = this.lower_node_id(new_node_id);
524 let res = this.lower_res(res);
525 let path = this.lower_path_extra(res, &path, ParamMode::Explicit, None);
526 let kind = hir::ItemKind::Use(path, hir::UseKind::Single);
527 let vis = this.rebuild_vis(&vis);
528 if let Some(attrs) = attrs {
529 this.attrs.insert(new_id, attrs);
532 this.insert_item(hir::Item {
533 def_id: new_id.expect_owner(),
534 ident: this.lower_ident(ident),
537 span: this.lower_span(span),
542 let path = self.lower_path_extra(ret_res, &path, ParamMode::Explicit, None);
543 hir::ItemKind::Use(path, hir::UseKind::Single)
545 UseTreeKind::Glob => {
546 let path = self.lower_path(
548 &Path { segments, span: path.span, tokens: None },
551 hir::ItemKind::Use(path, hir::UseKind::Glob)
553 UseTreeKind::Nested(ref trees) => {
554 // Nested imports are desugared into simple imports.
555 // So, if we start with
558 // pub(x) use foo::{a, b};
561 // we will create three items:
564 // pub(x) use foo::a;
565 // pub(x) use foo::b;
566 // pub(x) use foo::{}; // <-- this is called the `ListStem`
569 // The first two are produced by recursively invoking
570 // `lower_use_tree` (and indeed there may be things
571 // like `use foo::{a::{b, c}}` and so forth). They
572 // wind up being directly added to
573 // `self.items`. However, the structure of this
574 // function also requires us to return one item, and
575 // for that we return the `{}` import (called the
578 let prefix = Path { segments, span: prefix.span.to(path.span), tokens: None };
580 // Add all the nested `PathListItem`s to the HIR.
581 for &(ref use_tree, id) in trees {
582 let new_hir_id = self.lower_node_id(id);
584 let mut prefix = prefix.clone();
586 // Give the segments new node-ids since they are being cloned.
587 for seg in &mut prefix.segments {
588 seg.id = self.resolver.next_node_id();
591 // Each `use` import is an item and thus are owners of the
592 // names in the path. Up to this point the nested import is
593 // the current owner, since we want each desugared import to
594 // own its own names, we have to adjust the owner before
595 // lowering the rest of the import.
596 self.with_hir_id_owner(id, |this| {
597 let mut vis = this.rebuild_vis(&vis);
598 let mut ident = *ident;
601 this.lower_use_tree(use_tree, &prefix, id, &mut vis, &mut ident, attrs);
602 if let Some(attrs) = attrs {
603 this.attrs.insert(new_hir_id, attrs);
606 this.insert_item(hir::Item {
607 def_id: new_hir_id.expect_owner(),
608 ident: this.lower_ident(ident),
611 span: this.lower_span(use_tree.span),
616 // Subtle and a bit hacky: we lower the privacy level
617 // of the list stem to "private" most of the time, but
618 // not for "restricted" paths. The key thing is that
619 // we don't want it to stay as `pub` (with no caveats)
620 // because that affects rustdoc and also the lints
621 // about `pub` items. But we can't *always* make it
622 // private -- particularly not for restricted paths --
623 // because it contains node-ids that would then be
624 // unused, failing the check that HirIds are "densely
627 hir::VisibilityKind::Public
628 | hir::VisibilityKind::Crate(_)
629 | hir::VisibilityKind::Inherited => {
631 self.lower_span(prefix.span.shrink_to_lo()),
632 hir::VisibilityKind::Inherited,
635 hir::VisibilityKind::Restricted { .. } => {
636 // Do nothing here, as described in the comment on the match.
640 let res = self.expect_full_res_from_use(id).next().unwrap_or(Res::Err);
641 let res = self.lower_res(res);
642 let path = self.lower_path_extra(res, &prefix, ParamMode::Explicit, None);
643 hir::ItemKind::Use(path, hir::UseKind::ListStem)
648 /// Paths like the visibility path in `pub(super) use foo::{bar, baz}` are repeated
649 /// many times in the HIR tree; for each occurrence, we need to assign distinct
650 /// `NodeId`s. (See, e.g., #56128.)
651 fn rebuild_use_path(&mut self, path: &hir::Path<'hir>) -> &'hir hir::Path<'hir> {
652 debug!("rebuild_use_path(path = {:?})", path);
654 self.arena.alloc_from_iter(path.segments.iter().map(|seg| hir::PathSegment {
656 hir_id: seg.hir_id.map(|_| self.next_id()),
659 infer_args: seg.infer_args,
661 self.arena.alloc(hir::Path { span: path.span, res: path.res, segments })
664 fn rebuild_vis(&mut self, vis: &hir::Visibility<'hir>) -> hir::Visibility<'hir> {
665 let vis_kind = match vis.node {
666 hir::VisibilityKind::Public => hir::VisibilityKind::Public,
667 hir::VisibilityKind::Crate(sugar) => hir::VisibilityKind::Crate(sugar),
668 hir::VisibilityKind::Inherited => hir::VisibilityKind::Inherited,
669 hir::VisibilityKind::Restricted { ref path, hir_id: _ } => {
670 hir::VisibilityKind::Restricted {
671 path: self.rebuild_use_path(path),
672 hir_id: self.next_id(),
676 respan(self.lower_span(vis.span), vis_kind)
679 fn lower_foreign_item(&mut self, i: &ForeignItem) -> hir::ForeignItem<'hir> {
680 let hir_id = self.lower_node_id(i.id);
681 let def_id = hir_id.expect_owner();
682 self.lower_attrs(hir_id, &i.attrs);
685 ident: self.lower_ident(i.ident),
687 ForeignItemKind::Fn(box FnKind(_, ref sig, ref generics, _)) => {
688 let fdec = &sig.decl;
689 let (generics, (fn_dec, fn_args)) = self.add_in_band_defs(
692 AnonymousLifetimeMode::PassThrough,
695 // Disallow `impl Trait` in foreign items.
696 this.lower_fn_decl(fdec, None, false, None),
697 this.lower_fn_params_to_names(fdec),
702 hir::ForeignItemKind::Fn(fn_dec, fn_args, generics)
704 ForeignItemKind::Static(ref t, m, _) => {
705 let ty = self.lower_ty(t, ImplTraitContext::disallowed());
706 hir::ForeignItemKind::Static(ty, m)
708 ForeignItemKind::TyAlias(..) => hir::ForeignItemKind::Type,
709 ForeignItemKind::MacCall(_) => panic!("macro shouldn't exist here"),
711 vis: self.lower_visibility(&i.vis, None),
712 span: self.lower_span(i.span),
716 fn lower_foreign_item_ref(&mut self, i: &ForeignItem) -> hir::ForeignItemRef<'hir> {
717 hir::ForeignItemRef {
718 id: hir::ForeignItemId { def_id: self.lower_node_id(i.id).expect_owner() },
719 ident: self.lower_ident(i.ident),
720 span: self.lower_span(i.span),
721 vis: self.lower_visibility(&i.vis, Some(i.id)),
725 fn lower_variant(&mut self, v: &Variant) -> hir::Variant<'hir> {
726 let id = self.lower_node_id(v.id);
727 self.lower_attrs(id, &v.attrs);
730 data: self.lower_variant_data(id, &v.data),
731 disr_expr: v.disr_expr.as_ref().map(|e| self.lower_anon_const(e)),
732 ident: self.lower_ident(v.ident),
733 span: self.lower_span(v.span),
737 fn lower_variant_data(
739 parent_id: hir::HirId,
741 ) -> hir::VariantData<'hir> {
743 VariantData::Struct(ref fields, recovered) => hir::VariantData::Struct(
745 .alloc_from_iter(fields.iter().enumerate().map(|f| self.lower_field_def(f))),
748 VariantData::Tuple(ref fields, id) => {
749 let ctor_id = self.lower_node_id(id);
750 self.alias_attrs(ctor_id, parent_id);
751 hir::VariantData::Tuple(
752 self.arena.alloc_from_iter(
753 fields.iter().enumerate().map(|f| self.lower_field_def(f)),
758 VariantData::Unit(id) => {
759 let ctor_id = self.lower_node_id(id);
760 self.alias_attrs(ctor_id, parent_id);
761 hir::VariantData::Unit(ctor_id)
766 pub(super) fn lower_field_def(
768 (index, f): (usize, &FieldDef),
769 ) -> hir::FieldDef<'hir> {
770 let ty = if let TyKind::Path(ref qself, ref path) = f.ty.kind {
771 let t = self.lower_path_ty(
775 ParamMode::ExplicitNamed, // no `'_` in declarations (Issue #61124)
776 ImplTraitContext::disallowed(),
780 self.lower_ty(&f.ty, ImplTraitContext::disallowed())
782 let hir_id = self.lower_node_id(f.id);
783 self.lower_attrs(hir_id, &f.attrs);
785 span: self.lower_span(f.span),
787 ident: match f.ident {
788 Some(ident) => self.lower_ident(ident),
789 // FIXME(jseyfried): positional field hygiene.
790 None => Ident::new(sym::integer(index), self.lower_span(f.span)),
792 vis: self.lower_visibility(&f.vis, None),
797 fn lower_trait_item(&mut self, i: &AssocItem) -> hir::TraitItem<'hir> {
798 let hir_id = self.lower_node_id(i.id);
799 let trait_item_def_id = hir_id.expect_owner();
801 let (generics, kind) = match i.kind {
802 AssocItemKind::Const(_, ref ty, ref default) => {
803 let ty = self.lower_ty(ty, ImplTraitContext::disallowed());
804 let body = default.as_ref().map(|x| self.lower_const_body(i.span, Some(x)));
805 (hir::Generics::empty(), hir::TraitItemKind::Const(ty, body))
807 AssocItemKind::Fn(box FnKind(_, ref sig, ref generics, None)) => {
808 let names = self.lower_fn_params_to_names(&sig.decl);
809 let (generics, sig) =
810 self.lower_method_sig(generics, sig, trait_item_def_id, false, None, i.id);
811 (generics, hir::TraitItemKind::Fn(sig, hir::TraitFn::Required(names)))
813 AssocItemKind::Fn(box FnKind(_, ref sig, ref generics, Some(ref body))) => {
814 let asyncness = sig.header.asyncness;
816 self.lower_maybe_async_body(i.span, &sig.decl, asyncness, Some(&body));
817 let (generics, sig) = self.lower_method_sig(
822 asyncness.opt_return_id(),
825 (generics, hir::TraitItemKind::Fn(sig, hir::TraitFn::Provided(body_id)))
827 AssocItemKind::TyAlias(box TyAliasKind(_, ref generics, ref bounds, ref default)) => {
828 let ty = default.as_ref().map(|x| self.lower_ty(x, ImplTraitContext::disallowed()));
829 let generics = self.lower_generics(generics, ImplTraitContext::disallowed());
830 let kind = hir::TraitItemKind::Type(
831 self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
837 AssocItemKind::MacCall(..) => panic!("macro item shouldn't exist at this point"),
840 self.lower_attrs(hir_id, &i.attrs);
842 def_id: trait_item_def_id,
843 ident: self.lower_ident(i.ident),
846 span: self.lower_span(i.span),
850 fn lower_trait_item_ref(&mut self, i: &AssocItem) -> hir::TraitItemRef {
851 let (kind, has_default) = match &i.kind {
852 AssocItemKind::Const(_, _, default) => (hir::AssocItemKind::Const, default.is_some()),
853 AssocItemKind::TyAlias(box TyAliasKind(_, _, _, default)) => {
854 (hir::AssocItemKind::Type, default.is_some())
856 AssocItemKind::Fn(box FnKind(_, sig, _, default)) => {
857 (hir::AssocItemKind::Fn { has_self: sig.decl.has_self() }, default.is_some())
859 AssocItemKind::MacCall(..) => unimplemented!(),
861 let id = hir::TraitItemId { def_id: self.lower_node_id(i.id).expect_owner() };
862 let defaultness = hir::Defaultness::Default { has_value: has_default };
865 ident: self.lower_ident(i.ident),
866 span: self.lower_span(i.span),
872 /// Construct `ExprKind::Err` for the given `span`.
873 crate fn expr_err(&mut self, span: Span) -> hir::Expr<'hir> {
874 self.expr(span, hir::ExprKind::Err, AttrVec::new())
877 fn lower_impl_item(&mut self, i: &AssocItem) -> hir::ImplItem<'hir> {
878 let impl_item_def_id = self.resolver.local_def_id(i.id);
880 let (generics, kind) = match &i.kind {
881 AssocItemKind::Const(_, ty, expr) => {
882 let ty = self.lower_ty(ty, ImplTraitContext::disallowed());
884 hir::Generics::empty(),
885 hir::ImplItemKind::Const(ty, self.lower_const_body(i.span, expr.as_deref())),
888 AssocItemKind::Fn(box FnKind(_, sig, generics, body)) => {
889 self.current_item = Some(i.span);
890 let asyncness = sig.header.asyncness;
892 self.lower_maybe_async_body(i.span, &sig.decl, asyncness, body.as_deref());
893 let impl_trait_return_allow = !self.is_in_trait_impl;
894 let (generics, sig) = self.lower_method_sig(
898 impl_trait_return_allow,
899 asyncness.opt_return_id(),
903 (generics, hir::ImplItemKind::Fn(sig, body_id))
905 AssocItemKind::TyAlias(box TyAliasKind(_, generics, _, ty)) => {
906 let generics = self.lower_generics(generics, ImplTraitContext::disallowed());
907 let kind = match ty {
909 let ty = self.arena.alloc(self.ty(i.span, hir::TyKind::Err));
910 hir::ImplItemKind::TyAlias(ty)
913 let ty = self.lower_ty(
915 ImplTraitContext::TypeAliasesOpaqueTy {
916 capturable_lifetimes: &mut FxHashSet::default(),
919 hir::ImplItemKind::TyAlias(ty)
924 AssocItemKind::MacCall(..) => panic!("`TyMac` should have been expanded by now"),
927 // Since `default impl` is not yet implemented, this is always true in impls.
928 let has_value = true;
929 let (defaultness, _) = self.lower_defaultness(i.kind.defaultness(), has_value);
930 let hir_id = self.lower_node_id(i.id);
931 self.lower_attrs(hir_id, &i.attrs);
933 def_id: hir_id.expect_owner(),
934 ident: self.lower_ident(i.ident),
936 vis: self.lower_visibility(&i.vis, None),
939 span: self.lower_span(i.span),
943 fn lower_impl_item_ref(&mut self, i: &AssocItem) -> hir::ImplItemRef<'hir> {
944 // Since `default impl` is not yet implemented, this is always true in impls.
945 let has_value = true;
946 let (defaultness, _) = self.lower_defaultness(i.kind.defaultness(), has_value);
948 id: hir::ImplItemId { def_id: self.lower_node_id(i.id).expect_owner() },
949 ident: self.lower_ident(i.ident),
950 span: self.lower_span(i.span),
951 vis: self.lower_visibility(&i.vis, Some(i.id)),
953 kind: match &i.kind {
954 AssocItemKind::Const(..) => hir::AssocItemKind::Const,
955 AssocItemKind::TyAlias(..) => hir::AssocItemKind::Type,
956 AssocItemKind::Fn(box FnKind(_, sig, ..)) => {
957 hir::AssocItemKind::Fn { has_self: sig.decl.has_self() }
959 AssocItemKind::MacCall(..) => unimplemented!(),
964 /// If an `explicit_owner` is given, this method allocates the `HirId` in
965 /// the address space of that item instead of the item currently being
966 /// lowered. This can happen during `lower_impl_item_ref()` where we need to
967 /// lower a `Visibility` value although we haven't lowered the owning
968 /// `ImplItem` in question yet.
972 explicit_owner: Option<NodeId>,
973 ) -> hir::Visibility<'hir> {
974 let node = match v.kind {
975 VisibilityKind::Public => hir::VisibilityKind::Public,
976 VisibilityKind::Crate(sugar) => hir::VisibilityKind::Crate(sugar),
977 VisibilityKind::Restricted { ref path, id } => {
978 debug!("lower_visibility: restricted path id = {:?}", id);
979 let lowered_id = if let Some(owner) = explicit_owner {
980 self.lower_node_id_with_owner(id, owner)
982 self.lower_node_id(id)
984 let res = self.expect_full_res(id);
985 let res = self.lower_res(res);
986 hir::VisibilityKind::Restricted {
987 path: self.lower_path_extra(res, path, ParamMode::Explicit, explicit_owner),
991 VisibilityKind::Inherited => hir::VisibilityKind::Inherited,
993 respan(self.lower_span(v.span), node)
996 fn lower_defaultness(
1000 ) -> (hir::Defaultness, Option<Span>) {
1002 Defaultness::Default(sp) => {
1003 (hir::Defaultness::Default { has_value }, Some(self.lower_span(sp)))
1005 Defaultness::Final => {
1007 (hir::Defaultness::Final, None)
1014 params: &'hir [hir::Param<'hir>],
1015 value: hir::Expr<'hir>,
1017 let body = hir::Body { generator_kind: self.generator_kind, params, value };
1019 self.bodies.insert(id, body);
1023 pub(super) fn lower_body(
1025 f: impl FnOnce(&mut Self) -> (&'hir [hir::Param<'hir>], hir::Expr<'hir>),
1027 let prev_gen_kind = self.generator_kind.take();
1028 let task_context = self.task_context.take();
1029 let (parameters, result) = f(self);
1030 let body_id = self.record_body(parameters, result);
1031 self.task_context = task_context;
1032 self.generator_kind = prev_gen_kind;
1036 fn lower_param(&mut self, param: &Param) -> hir::Param<'hir> {
1037 let hir_id = self.lower_node_id(param.id);
1038 self.lower_attrs(hir_id, ¶m.attrs);
1041 pat: self.lower_pat(¶m.pat),
1042 ty_span: self.lower_span(param.ty.span),
1043 span: self.lower_span(param.span),
1047 pub(super) fn lower_fn_body(
1050 body: impl FnOnce(&mut Self) -> hir::Expr<'hir>,
1052 self.lower_body(|this| {
1054 this.arena.alloc_from_iter(decl.inputs.iter().map(|x| this.lower_param(x))),
1060 fn lower_fn_body_block(
1064 body: Option<&Block>,
1066 self.lower_fn_body(decl, |this| this.lower_block_expr_opt(span, body))
1069 fn lower_block_expr_opt(&mut self, span: Span, block: Option<&Block>) -> hir::Expr<'hir> {
1071 Some(block) => self.lower_block_expr(block),
1072 None => self.expr_err(span),
1076 pub(super) fn lower_const_body(&mut self, span: Span, expr: Option<&Expr>) -> hir::BodyId {
1077 self.lower_body(|this| {
1081 Some(expr) => this.lower_expr_mut(expr),
1082 None => this.expr_err(span),
1088 fn lower_maybe_async_body(
1093 body: Option<&Block>,
1095 let closure_id = match asyncness {
1096 Async::Yes { closure_id, .. } => closure_id,
1097 Async::No => return self.lower_fn_body_block(span, decl, body),
1100 self.lower_body(|this| {
1101 let mut parameters: Vec<hir::Param<'_>> = Vec::new();
1102 let mut statements: Vec<hir::Stmt<'_>> = Vec::new();
1104 // Async function parameters are lowered into the closure body so that they are
1105 // captured and so that the drop order matches the equivalent non-async functions.
1109 // async fn foo(<pattern>: <ty>, <pattern>: <ty>, <pattern>: <ty>) {
1115 // fn foo(__arg0: <ty>, __arg1: <ty>, __arg2: <ty>) {
1117 // let __arg2 = __arg2;
1118 // let <pattern> = __arg2;
1119 // let __arg1 = __arg1;
1120 // let <pattern> = __arg1;
1121 // let __arg0 = __arg0;
1122 // let <pattern> = __arg0;
1123 // drop-temps { <body> } // see comments later in fn for details
1127 // If `<pattern>` is a simple ident, then it is lowered to a single
1128 // `let <pattern> = <pattern>;` statement as an optimization.
1130 // Note that the body is embedded in `drop-temps`; an
1131 // equivalent desugaring would be `return { <body>
1132 // };`. The key point is that we wish to drop all the
1133 // let-bound variables and temporaries created in the body
1134 // (and its tail expression!) before we drop the
1135 // parameters (c.f. rust-lang/rust#64512).
1136 for (index, parameter) in decl.inputs.iter().enumerate() {
1137 let parameter = this.lower_param(parameter);
1138 let span = parameter.pat.span;
1140 // Check if this is a binding pattern, if so, we can optimize and avoid adding a
1141 // `let <pat> = __argN;` statement. In this case, we do not rename the parameter.
1142 let (ident, is_simple_parameter) = match parameter.pat.kind {
1143 hir::PatKind::Binding(
1144 hir::BindingAnnotation::Unannotated | hir::BindingAnnotation::Mutable,
1149 // For `ref mut` or wildcard arguments, we can't reuse the binding, but
1150 // we can keep the same name for the parameter.
1151 // This lets rustdoc render it correctly in documentation.
1152 hir::PatKind::Binding(_, _, ident, _) => (ident, false),
1153 hir::PatKind::Wild => {
1154 (Ident::with_dummy_span(rustc_span::symbol::kw::Underscore), false)
1157 // Replace the ident for bindings that aren't simple.
1158 let name = format!("__arg{}", index);
1159 let ident = Ident::from_str(&name);
1165 let desugared_span = this.mark_span_with_reason(DesugaringKind::Async, span, None);
1167 // Construct a parameter representing `__argN: <ty>` to replace the parameter of the
1170 // If this is the simple case, this parameter will end up being the same as the
1171 // original parameter, but with a different pattern id.
1172 let stmt_attrs = this.attrs.get(¶meter.hir_id).copied();
1173 let (new_parameter_pat, new_parameter_id) = this.pat_ident(desugared_span, ident);
1174 let new_parameter = hir::Param {
1175 hir_id: parameter.hir_id,
1176 pat: new_parameter_pat,
1177 ty_span: this.lower_span(parameter.ty_span),
1178 span: this.lower_span(parameter.span),
1181 if is_simple_parameter {
1182 // If this is the simple case, then we only insert one statement that is
1183 // `let <pat> = <pat>;`. We re-use the original argument's pattern so that
1184 // `HirId`s are densely assigned.
1185 let expr = this.expr_ident(desugared_span, ident, new_parameter_id);
1186 let stmt = this.stmt_let_pat(
1191 hir::LocalSource::AsyncFn,
1193 statements.push(stmt);
1195 // If this is not the simple case, then we construct two statements:
1198 // let __argN = __argN;
1199 // let <pat> = __argN;
1202 // The first statement moves the parameter into the closure and thus ensures
1203 // that the drop order is correct.
1205 // The second statement creates the bindings that the user wrote.
1207 // Construct the `let mut __argN = __argN;` statement. It must be a mut binding
1208 // because the user may have specified a `ref mut` binding in the next
1210 let (move_pat, move_id) = this.pat_ident_binding_mode(
1213 hir::BindingAnnotation::Mutable,
1215 let move_expr = this.expr_ident(desugared_span, ident, new_parameter_id);
1216 let move_stmt = this.stmt_let_pat(
1221 hir::LocalSource::AsyncFn,
1224 // Construct the `let <pat> = __argN;` statement. We re-use the original
1225 // parameter's pattern so that `HirId`s are densely assigned.
1226 let pattern_expr = this.expr_ident(desugared_span, ident, move_id);
1227 let pattern_stmt = this.stmt_let_pat(
1232 hir::LocalSource::AsyncFn,
1235 statements.push(move_stmt);
1236 statements.push(pattern_stmt);
1239 parameters.push(new_parameter);
1242 let body_span = body.map_or(span, |b| b.span);
1243 let async_expr = this.make_async_expr(
1248 hir::AsyncGeneratorKind::Fn,
1250 // Create a block from the user's function body:
1251 let user_body = this.lower_block_expr_opt(body_span, body);
1253 // Transform into `drop-temps { <user-body> }`, an expression:
1254 let desugared_span =
1255 this.mark_span_with_reason(DesugaringKind::Async, user_body.span, None);
1256 let user_body = this.expr_drop_temps(
1258 this.arena.alloc(user_body),
1262 // As noted above, create the final block like
1266 // let $param_pattern = $raw_param;
1268 // drop-temps { <user-body> }
1271 let body = this.block_all(
1273 this.arena.alloc_from_iter(statements),
1277 this.expr_block(body, AttrVec::new())
1282 this.arena.alloc_from_iter(parameters),
1283 this.expr(body_span, async_expr, AttrVec::new()),
1288 fn lower_method_sig(
1290 generics: &Generics,
1292 fn_def_id: LocalDefId,
1293 impl_trait_return_allow: bool,
1294 is_async: Option<NodeId>,
1296 ) -> (hir::Generics<'hir>, hir::FnSig<'hir>) {
1297 let header = self.lower_fn_header(sig.header, sig.span, id);
1298 let (generics, decl) = self.add_in_band_defs(
1301 AnonymousLifetimeMode::PassThrough,
1305 Some((fn_def_id.to_def_id(), idty)),
1306 impl_trait_return_allow,
1311 (generics, hir::FnSig { header, decl, span: self.lower_span(sig.span) })
1314 fn lower_fn_header(&mut self, h: FnHeader, span: Span, id: NodeId) -> hir::FnHeader {
1316 unsafety: self.lower_unsafety(h.unsafety),
1317 asyncness: self.lower_asyncness(h.asyncness),
1318 constness: self.lower_constness(h.constness),
1319 abi: self.lower_extern(h.ext, span, id),
1323 pub(super) fn lower_abi(&mut self, abi: StrLit) -> abi::Abi {
1324 abi::lookup(&abi.symbol_unescaped.as_str()).unwrap_or_else(|| {
1325 self.error_on_invalid_abi(abi);
1330 pub(super) fn lower_extern(&mut self, ext: Extern, span: Span, id: NodeId) -> abi::Abi {
1332 Extern::None => abi::Abi::Rust,
1333 Extern::Implicit => {
1334 self.maybe_lint_missing_abi(span, id, abi::Abi::C { unwind: false });
1335 abi::Abi::C { unwind: false }
1337 Extern::Explicit(abi) => self.lower_abi(abi),
1341 fn error_on_invalid_abi(&self, abi: StrLit) {
1342 struct_span_err!(self.sess, abi.span, E0703, "invalid ABI: found `{}`", abi.symbol)
1343 .span_label(abi.span, "invalid ABI")
1344 .help(&format!("valid ABIs: {}", abi::all_names().join(", ")))
1348 fn lower_asyncness(&mut self, a: Async) -> hir::IsAsync {
1350 Async::Yes { .. } => hir::IsAsync::Async,
1351 Async::No => hir::IsAsync::NotAsync,
1355 fn lower_constness(&mut self, c: Const) -> hir::Constness {
1357 Const::Yes(_) => hir::Constness::Const,
1358 Const::No => hir::Constness::NotConst,
1362 pub(super) fn lower_unsafety(&mut self, u: Unsafe) -> hir::Unsafety {
1364 Unsafe::Yes(_) => hir::Unsafety::Unsafe,
1365 Unsafe::No => hir::Unsafety::Normal,
1369 pub(super) fn lower_generics_mut(
1371 generics: &Generics,
1372 itctx: ImplTraitContext<'_, 'hir>,
1373 ) -> GenericsCtor<'hir> {
1374 // Collect `?Trait` bounds in where clause and move them to parameter definitions.
1375 let mut add_bounds: NodeMap<Vec<_>> = Default::default();
1376 for pred in &generics.where_clause.predicates {
1377 if let WherePredicate::BoundPredicate(ref bound_pred) = *pred {
1378 'next_bound: for bound in &bound_pred.bounds {
1379 if let GenericBound::Trait(_, TraitBoundModifier::Maybe) = *bound {
1380 // Check if the where clause type is a plain type parameter.
1383 .get_partial_res(bound_pred.bounded_ty.id)
1384 .map(|d| (d.base_res(), d.unresolved_segments()))
1386 Some((Res::Def(DefKind::TyParam, def_id), 0))
1387 if bound_pred.bound_generic_params.is_empty() =>
1389 for param in &generics.params {
1390 if def_id == self.resolver.local_def_id(param.id).to_def_id() {
1391 add_bounds.entry(param.id).or_default().push(bound.clone());
1392 continue 'next_bound;
1398 self.diagnostic().span_err(
1399 bound_pred.bounded_ty.span,
1400 "`?Trait` bounds are only permitted at the \
1401 point where a type parameter is declared",
1409 params: self.lower_generic_params_mut(&generics.params, &add_bounds, itctx).collect(),
1410 where_clause: self.lower_where_clause(&generics.where_clause),
1411 span: self.lower_span(generics.span),
1415 pub(super) fn lower_generics(
1417 generics: &Generics,
1418 itctx: ImplTraitContext<'_, 'hir>,
1419 ) -> hir::Generics<'hir> {
1420 let generics_ctor = self.lower_generics_mut(generics, itctx);
1421 generics_ctor.into_generics(self.arena)
1424 fn lower_where_clause(&mut self, wc: &WhereClause) -> hir::WhereClause<'hir> {
1425 self.with_anonymous_lifetime_mode(AnonymousLifetimeMode::ReportError, |this| {
1427 predicates: this.arena.alloc_from_iter(
1428 wc.predicates.iter().map(|predicate| this.lower_where_predicate(predicate)),
1430 span: this.lower_span(wc.span),
1435 fn lower_where_predicate(&mut self, pred: &WherePredicate) -> hir::WherePredicate<'hir> {
1437 WherePredicate::BoundPredicate(WhereBoundPredicate {
1438 ref bound_generic_params,
1443 self.with_in_scope_lifetime_defs(&bound_generic_params, |this| {
1444 hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
1445 bound_generic_params: this.lower_generic_params(
1446 bound_generic_params,
1447 &NodeMap::default(),
1448 ImplTraitContext::disallowed(),
1450 bounded_ty: this.lower_ty(bounded_ty, ImplTraitContext::disallowed()),
1451 bounds: this.arena.alloc_from_iter(bounds.iter().map(
1452 |bound| match bound {
1453 // We used to ignore `?Trait` bounds, as they were copied into type
1454 // parameters already, but we need to keep them around only for
1455 // diagnostics when we suggest removal of `?Sized` bounds. See
1456 // `suggest_constraining_type_param`. This will need to change if
1457 // we ever allow something *other* than `?Sized`.
1458 GenericBound::Trait(p, TraitBoundModifier::Maybe) => {
1459 hir::GenericBound::Unsized(this.lower_span(p.span))
1461 _ => this.lower_param_bound(bound, ImplTraitContext::disallowed()),
1464 span: this.lower_span(span),
1468 WherePredicate::RegionPredicate(WhereRegionPredicate {
1472 }) => hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate {
1473 span: self.lower_span(span),
1474 lifetime: self.lower_lifetime(lifetime),
1475 bounds: self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
1477 WherePredicate::EqPredicate(WhereEqPredicate { id, ref lhs_ty, ref rhs_ty, span }) => {
1478 hir::WherePredicate::EqPredicate(hir::WhereEqPredicate {
1479 hir_id: self.lower_node_id(id),
1480 lhs_ty: self.lower_ty(lhs_ty, ImplTraitContext::disallowed()),
1481 rhs_ty: self.lower_ty(rhs_ty, ImplTraitContext::disallowed()),
1482 span: self.lower_span(span),
1489 /// Helper struct for delayed construction of Generics.
1490 pub(super) struct GenericsCtor<'hir> {
1491 pub(super) params: SmallVec<[hir::GenericParam<'hir>; 4]>,
1492 where_clause: hir::WhereClause<'hir>,
1496 impl<'hir> GenericsCtor<'hir> {
1497 pub(super) fn into_generics(self, arena: &'hir Arena<'hir>) -> hir::Generics<'hir> {
1499 params: arena.alloc_from_iter(self.params),
1500 where_clause: self.where_clause,