1 //! Lowers the AST to the HIR.
3 //! Since the AST and HIR are fairly similar, this is mostly a simple procedure,
4 //! much like a fold. Where lowering involves a bit more work things get more
5 //! interesting and there are some invariants you should know about. These mostly
6 //! concern spans and IDs.
8 //! Spans are assigned to AST nodes during parsing and then are modified during
9 //! expansion to indicate the origin of a node and the process it went through
10 //! being expanded. IDs are assigned to AST nodes just before lowering.
12 //! For the simpler lowering steps, IDs and spans should be preserved. Unlike
13 //! expansion we do not preserve the process of lowering in the spans, so spans
14 //! should not be modified here. When creating a new node (as opposed to
15 //! 'folding' an existing one), then you create a new ID using `next_id()`.
17 //! You must ensure that IDs are unique. That means that you should only use the
18 //! ID from an AST node in a single HIR node (you can assume that AST node-IDs
19 //! are unique). Every new node must have a unique ID. Avoid cloning HIR nodes.
20 //! If you do, you must then set the new node's ID to a fresh one.
22 //! Spans are used for error messages and for tools to map semantics back to
23 //! source code. It is therefore not as important with spans as IDs to be strict
24 //! about use (you can't break the compiler by screwing up a span). Obviously, a
25 //! HIR node can only have a single span. But multiple nodes can have the same
26 //! span and spans don't need to be kept in order, etc. Where code is preserved
27 //! by lowering, it should have the same span as in the AST. Where HIR nodes are
28 //! new it is probably best to give a span for the whole AST node being lowered.
29 //! All nodes should have real spans, don't use dummy spans. Tools are likely to
30 //! get confused if the spans from leaf AST nodes occur in multiple places
31 //! in the HIR, especially for multiple identifiers.
33 #![feature(array_value_iter)]
34 #![feature(crate_visibility_modifier)]
35 #![feature(or_patterns)]
36 #![recursion_limit = "256"]
38 use rustc_ast::node_id::NodeMap;
39 use rustc_ast::token::{self, DelimToken, Nonterminal, Token};
40 use rustc_ast::tokenstream::{DelimSpan, TokenStream, TokenTree};
41 use rustc_ast::visit::{self, AssocCtxt, Visitor};
42 use rustc_ast::walk_list;
43 use rustc_ast::{self as ast, *};
44 use rustc_ast_pretty::pprust;
45 use rustc_data_structures::captures::Captures;
46 use rustc_data_structures::fx::FxHashSet;
47 use rustc_data_structures::sync::Lrc;
48 use rustc_errors::struct_span_err;
50 use rustc_hir::def::{DefKind, Namespace, PartialRes, PerNS, Res};
51 use rustc_hir::def_id::{DefId, DefIdMap, LocalDefId, CRATE_DEF_INDEX};
52 use rustc_hir::definitions::{DefKey, DefPathData, Definitions};
53 use rustc_hir::intravisit;
54 use rustc_hir::{ConstArg, GenericArg, ParamName};
55 use rustc_index::vec::{Idx, IndexVec};
56 use rustc_session::config::nightly_options;
57 use rustc_session::lint::{builtin::BARE_TRAIT_OBJECTS, BuiltinLintDiagnostics, LintBuffer};
58 use rustc_session::parse::ParseSess;
59 use rustc_session::Session;
60 use rustc_span::hygiene::ExpnId;
61 use rustc_span::source_map::{respan, DesugaringKind, ExpnData, ExpnKind};
62 use rustc_span::symbol::{kw, sym, Ident, Symbol};
65 use smallvec::{smallvec, SmallVec};
66 use std::collections::BTreeMap;
68 use tracing::{debug, trace};
70 macro_rules! arena_vec {
71 ($this:expr; $($x:expr),*) => ({
73 $this.arena.alloc_from_iter(std::array::IntoIter::new(a))
82 const HIR_ID_COUNTER_LOCKED: u32 = 0xFFFFFFFF;
84 rustc_hir::arena_types!(rustc_arena::declare_arena, [], 'tcx);
86 struct LoweringContext<'a, 'hir: 'a> {
87 /// Used to assign IDs to HIR nodes that do not directly correspond to AST nodes.
90 resolver: &'a mut dyn ResolverAstLowering,
92 /// HACK(Centril): there is a cyclic dependency between the parser and lowering
93 /// if we don't have this function pointer. To avoid that dependency so that
94 /// librustc_middle is independent of the parser, we use dynamic dispatch here.
95 nt_to_tokenstream: NtToTokenstream,
97 /// Used to allocate HIR nodes
98 arena: &'hir Arena<'hir>,
100 /// The items being lowered are collected here.
101 items: BTreeMap<hir::HirId, hir::Item<'hir>>,
103 trait_items: BTreeMap<hir::TraitItemId, hir::TraitItem<'hir>>,
104 impl_items: BTreeMap<hir::ImplItemId, hir::ImplItem<'hir>>,
105 bodies: BTreeMap<hir::BodyId, hir::Body<'hir>>,
106 exported_macros: Vec<hir::MacroDef<'hir>>,
107 non_exported_macro_attrs: Vec<ast::Attribute>,
109 trait_impls: BTreeMap<DefId, Vec<hir::HirId>>,
111 modules: BTreeMap<hir::HirId, hir::ModuleItems>,
113 generator_kind: Option<hir::GeneratorKind>,
115 /// When inside an `async` context, this is the `HirId` of the
116 /// `task_context` local bound to the resume argument of the generator.
117 task_context: Option<hir::HirId>,
119 /// Used to get the current `fn`'s def span to point to when using `await`
120 /// outside of an `async fn`.
121 current_item: Option<Span>,
123 catch_scopes: Vec<NodeId>,
124 loop_scopes: Vec<NodeId>,
125 is_in_loop_condition: bool,
126 is_in_trait_impl: bool,
127 is_in_dyn_type: bool,
129 /// What to do when we encounter either an "anonymous lifetime
130 /// reference". The term "anonymous" is meant to encompass both
131 /// `'_` lifetimes as well as fully elided cases where nothing is
132 /// written at all (e.g., `&T` or `std::cell::Ref<T>`).
133 anonymous_lifetime_mode: AnonymousLifetimeMode,
135 /// Used to create lifetime definitions from in-band lifetime usages.
136 /// e.g., `fn foo(x: &'x u8) -> &'x u8` to `fn foo<'x>(x: &'x u8) -> &'x u8`
137 /// When a named lifetime is encountered in a function or impl header and
138 /// has not been defined
139 /// (i.e., it doesn't appear in the in_scope_lifetimes list), it is added
140 /// to this list. The results of this list are then added to the list of
141 /// lifetime definitions in the corresponding impl or function generics.
142 lifetimes_to_define: Vec<(Span, ParamName)>,
144 /// `true` if in-band lifetimes are being collected. This is used to
145 /// indicate whether or not we're in a place where new lifetimes will result
146 /// in in-band lifetime definitions, such a function or an impl header,
147 /// including implicit lifetimes from `impl_header_lifetime_elision`.
148 is_collecting_in_band_lifetimes: bool,
150 /// Currently in-scope lifetimes defined in impl headers, fn headers, or HRTB.
151 /// When `is_collectin_in_band_lifetimes` is true, each lifetime is checked
152 /// against this list to see if it is already in-scope, or if a definition
153 /// needs to be created for it.
155 /// We always store a `normalize_to_macros_2_0()` version of the param-name in this
157 in_scope_lifetimes: Vec<ParamName>,
159 current_module: hir::HirId,
161 type_def_lifetime_params: DefIdMap<usize>,
163 current_hir_id_owner: Vec<(LocalDefId, u32)>,
164 item_local_id_counters: NodeMap<u32>,
165 node_id_to_hir_id: IndexVec<NodeId, Option<hir::HirId>>,
167 allow_try_trait: Option<Lrc<[Symbol]>>,
168 allow_gen_future: Option<Lrc<[Symbol]>>,
171 pub trait ResolverAstLowering {
172 fn def_key(&mut self, id: DefId) -> DefKey;
174 fn item_generics_num_lifetimes(&self, def: DefId, sess: &Session) -> usize;
176 /// Obtains resolution for a `NodeId` with a single resolution.
177 fn get_partial_res(&mut self, id: NodeId) -> Option<PartialRes>;
179 /// Obtains per-namespace resolutions for `use` statement with the given `NodeId`.
180 fn get_import_res(&mut self, id: NodeId) -> PerNS<Option<Res<NodeId>>>;
182 /// Obtains resolution for a label with the given `NodeId`.
183 fn get_label_res(&mut self, id: NodeId) -> Option<NodeId>;
185 /// We must keep the set of definitions up to date as we add nodes that weren't in the AST.
186 /// This should only return `None` during testing.
187 fn definitions(&mut self) -> &mut Definitions;
189 fn lint_buffer(&mut self) -> &mut LintBuffer;
191 fn next_node_id(&mut self) -> NodeId;
193 fn trait_map(&self) -> &NodeMap<Vec<hir::TraitCandidate>>;
195 fn opt_local_def_id(&self, node: NodeId) -> Option<LocalDefId>;
197 fn local_def_id(&self, node: NodeId) -> LocalDefId;
202 node_id: ast::NodeId,
209 type NtToTokenstream = fn(&Nonterminal, &ParseSess, Span) -> TokenStream;
211 /// Context of `impl Trait` in code, which determines whether it is allowed in an HIR subtree,
212 /// and if so, what meaning it has.
214 enum ImplTraitContext<'b, 'a> {
215 /// Treat `impl Trait` as shorthand for a new universal generic parameter.
216 /// Example: `fn foo(x: impl Debug)`, where `impl Debug` is conceptually
217 /// equivalent to a fresh universal parameter like `fn foo<T: Debug>(x: T)`.
219 /// Newly generated parameters should be inserted into the given `Vec`.
220 Universal(&'b mut Vec<hir::GenericParam<'a>>),
222 /// Treat `impl Trait` as shorthand for a new opaque type.
223 /// Example: `fn foo() -> impl Debug`, where `impl Debug` is conceptually
224 /// equivalent to a new opaque type like `type T = impl Debug; fn foo() -> T`.
226 ReturnPositionOpaqueTy {
227 /// `DefId` for the parent function, used to look up necessary
228 /// information later.
230 /// Origin: Either OpaqueTyOrigin::FnReturn or OpaqueTyOrigin::AsyncFn,
231 origin: hir::OpaqueTyOrigin,
233 /// Impl trait in type aliases, consts and statics.
235 /// Set of lifetimes that this opaque type can capture, if it uses
236 /// them. This includes lifetimes bound since we entered this context.
239 /// type A<'b> = impl for<'a> Trait<'a, Out = impl Sized + 'a>;
241 /// the inner opaque type captures `'a` because it uses it. It doesn't
242 /// need to capture `'b` because it already inherits the lifetime
243 /// parameter from `A`.
244 // FIXME(impl_trait): but `required_region_bounds` will ICE later
246 capturable_lifetimes: &'b mut FxHashSet<hir::LifetimeName>,
247 /// Origin: Either OpaqueTyOrigin::Misc or OpaqueTyOrigin::Binding,
248 origin: hir::OpaqueTyOrigin,
250 /// `impl Trait` is not accepted in this position.
251 Disallowed(ImplTraitPosition),
254 /// Position in which `impl Trait` is disallowed.
255 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
256 enum ImplTraitPosition {
257 /// Disallowed in `let` / `const` / `static` bindings.
260 /// All other posiitons.
264 impl<'a> ImplTraitContext<'_, 'a> {
266 fn disallowed() -> Self {
267 ImplTraitContext::Disallowed(ImplTraitPosition::Other)
270 fn reborrow<'this>(&'this mut self) -> ImplTraitContext<'this, 'a> {
271 use self::ImplTraitContext::*;
273 Universal(params) => Universal(params),
274 ReturnPositionOpaqueTy { fn_def_id, origin } => {
275 ReturnPositionOpaqueTy { fn_def_id: *fn_def_id, origin: *origin }
277 OtherOpaqueTy { capturable_lifetimes, origin } => {
278 OtherOpaqueTy { capturable_lifetimes, origin: *origin }
280 Disallowed(pos) => Disallowed(*pos),
285 pub fn lower_crate<'a, 'hir>(
288 resolver: &'a mut dyn ResolverAstLowering,
289 nt_to_tokenstream: NtToTokenstream,
290 arena: &'hir Arena<'hir>,
291 ) -> hir::Crate<'hir> {
292 let _prof_timer = sess.prof.verbose_generic_activity("hir_lowering");
299 items: BTreeMap::new(),
300 trait_items: BTreeMap::new(),
301 impl_items: BTreeMap::new(),
302 bodies: BTreeMap::new(),
303 trait_impls: BTreeMap::new(),
304 modules: BTreeMap::new(),
305 exported_macros: Vec::new(),
306 non_exported_macro_attrs: Vec::new(),
307 catch_scopes: Vec::new(),
308 loop_scopes: Vec::new(),
309 is_in_loop_condition: false,
310 is_in_trait_impl: false,
311 is_in_dyn_type: false,
312 anonymous_lifetime_mode: AnonymousLifetimeMode::PassThrough,
313 type_def_lifetime_params: Default::default(),
314 current_module: hir::CRATE_HIR_ID,
315 current_hir_id_owner: vec![(LocalDefId { local_def_index: CRATE_DEF_INDEX }, 0)],
316 item_local_id_counters: Default::default(),
317 node_id_to_hir_id: IndexVec::new(),
318 generator_kind: None,
321 lifetimes_to_define: Vec::new(),
322 is_collecting_in_band_lifetimes: false,
323 in_scope_lifetimes: Vec::new(),
324 allow_try_trait: Some([sym::try_trait][..].into()),
325 allow_gen_future: Some([sym::gen_future][..].into()),
330 #[derive(Copy, Clone, PartialEq)]
332 /// Any path in a type context.
334 /// Path in a type definition, where the anonymous lifetime `'_` is not allowed.
336 /// The `module::Type` in `module::Type::method` in an expression.
340 enum ParenthesizedGenericArgs {
345 /// What to do when we encounter an **anonymous** lifetime
346 /// reference. Anonymous lifetime references come in two flavors. You
347 /// have implicit, or fully elided, references to lifetimes, like the
348 /// one in `&T` or `Ref<T>`, and you have `'_` lifetimes, like `&'_ T`
349 /// or `Ref<'_, T>`. These often behave the same, but not always:
351 /// - certain usages of implicit references are deprecated, like
352 /// `Ref<T>`, and we sometimes just give hard errors in those cases
354 /// - for object bounds there is a difference: `Box<dyn Foo>` is not
355 /// the same as `Box<dyn Foo + '_>`.
357 /// We describe the effects of the various modes in terms of three cases:
359 /// - **Modern** -- includes all uses of `'_`, but also the lifetime arg
360 /// of a `&` (e.g., the missing lifetime in something like `&T`)
361 /// - **Dyn Bound** -- if you have something like `Box<dyn Foo>`,
362 /// there is an elided lifetime bound (`Box<dyn Foo + 'X>`). These
363 /// elided bounds follow special rules. Note that this only covers
364 /// cases where *nothing* is written; the `'_` in `Box<dyn Foo +
365 /// '_>` is a case of "modern" elision.
366 /// - **Deprecated** -- this coverse cases like `Ref<T>`, where the lifetime
367 /// parameter to ref is completely elided. `Ref<'_, T>` would be the modern,
368 /// non-deprecated equivalent.
370 /// Currently, the handling of lifetime elision is somewhat spread out
371 /// between HIR lowering and -- as described below -- the
372 /// `resolve_lifetime` module. Often we "fallthrough" to that code by generating
373 /// an "elided" or "underscore" lifetime name. In the future, we probably want to move
374 /// everything into HIR lowering.
375 #[derive(Copy, Clone, Debug)]
376 enum AnonymousLifetimeMode {
377 /// For **Modern** cases, create a new anonymous region parameter
378 /// and reference that.
380 /// For **Dyn Bound** cases, pass responsibility to
381 /// `resolve_lifetime` code.
383 /// For **Deprecated** cases, report an error.
386 /// Give a hard error when either `&` or `'_` is written. Used to
387 /// rule out things like `where T: Foo<'_>`. Does not imply an
388 /// error on default object bounds (e.g., `Box<dyn Foo>`).
391 /// Pass responsibility to `resolve_lifetime` code for all cases.
395 struct ImplTraitTypeIdVisitor<'a> {
396 ids: &'a mut SmallVec<[NodeId; 1]>,
399 impl Visitor<'_> for ImplTraitTypeIdVisitor<'_> {
400 fn visit_ty(&mut self, ty: &Ty) {
402 TyKind::Typeof(_) | TyKind::BareFn(_) => return,
404 TyKind::ImplTrait(id, _) => self.ids.push(id),
407 visit::walk_ty(self, ty);
410 fn visit_path_segment(&mut self, path_span: Span, path_segment: &PathSegment) {
411 if let Some(ref p) = path_segment.args {
412 if let GenericArgs::Parenthesized(_) = **p {
416 visit::walk_path_segment(self, path_span, path_segment)
420 impl<'a, 'hir> LoweringContext<'a, 'hir> {
421 fn lower_crate(mut self, c: &Crate) -> hir::Crate<'hir> {
422 /// Full-crate AST visitor that inserts into a fresh
423 /// `LoweringContext` any information that may be
424 /// needed from arbitrary locations in the crate,
425 /// e.g., the number of lifetime generic parameters
426 /// declared for every type and trait definition.
427 struct MiscCollector<'tcx, 'lowering, 'hir> {
428 lctx: &'tcx mut LoweringContext<'lowering, 'hir>,
429 hir_id_owner: Option<NodeId>,
432 impl MiscCollector<'_, '_, '_> {
433 fn allocate_use_tree_hir_id_counters(&mut self, tree: &UseTree, owner: LocalDefId) {
435 UseTreeKind::Simple(_, id1, id2) => {
436 for &id in &[id1, id2] {
437 self.lctx.resolver.create_def(
444 self.lctx.allocate_hir_id_counter(id);
447 UseTreeKind::Glob => (),
448 UseTreeKind::Nested(ref trees) => {
449 for &(ref use_tree, id) in trees {
450 let hir_id = self.lctx.allocate_hir_id_counter(id);
451 self.allocate_use_tree_hir_id_counters(use_tree, hir_id.owner);
457 fn with_hir_id_owner<T>(
459 owner: Option<NodeId>,
460 f: impl FnOnce(&mut Self) -> T,
462 let old = mem::replace(&mut self.hir_id_owner, owner);
464 self.hir_id_owner = old;
469 impl<'tcx> Visitor<'tcx> for MiscCollector<'tcx, '_, '_> {
470 fn visit_pat(&mut self, p: &'tcx Pat) {
471 if let PatKind::Paren(..) | PatKind::Rest = p.kind {
472 // Doesn't generate a HIR node
473 } else if let Some(owner) = self.hir_id_owner {
474 self.lctx.lower_node_id_with_owner(p.id, owner);
477 visit::walk_pat(self, p)
480 fn visit_item(&mut self, item: &'tcx Item) {
481 let hir_id = self.lctx.allocate_hir_id_counter(item.id);
484 ItemKind::Struct(_, ref generics)
485 | ItemKind::Union(_, ref generics)
486 | ItemKind::Enum(_, ref generics)
487 | ItemKind::TyAlias(_, ref generics, ..)
488 | ItemKind::Trait(_, _, ref generics, ..) => {
489 let def_id = self.lctx.resolver.local_def_id(item.id);
493 .filter(|param| match param.kind {
494 ast::GenericParamKind::Lifetime { .. } => true,
498 self.lctx.type_def_lifetime_params.insert(def_id.to_def_id(), count);
500 ItemKind::Use(ref use_tree) => {
501 self.allocate_use_tree_hir_id_counters(use_tree, hir_id.owner);
506 self.with_hir_id_owner(Some(item.id), |this| {
507 visit::walk_item(this, item);
511 fn visit_assoc_item(&mut self, item: &'tcx AssocItem, ctxt: AssocCtxt) {
512 self.lctx.allocate_hir_id_counter(item.id);
513 let owner = match (&item.kind, ctxt) {
514 // Ignore patterns in trait methods without bodies.
515 (AssocItemKind::Fn(_, _, _, None), AssocCtxt::Trait) => None,
518 self.with_hir_id_owner(owner, |this| visit::walk_assoc_item(this, item, ctxt));
521 fn visit_foreign_item(&mut self, i: &'tcx ForeignItem) {
522 // Ignore patterns in foreign items
523 self.with_hir_id_owner(None, |this| visit::walk_foreign_item(this, i));
526 fn visit_ty(&mut self, t: &'tcx Ty) {
528 // Mirrors the case in visit::walk_ty
529 TyKind::BareFn(ref f) => {
530 walk_list!(self, visit_generic_param, &f.generic_params);
531 // Mirrors visit::walk_fn_decl
532 for parameter in &f.decl.inputs {
533 // We don't lower the ids of argument patterns
534 self.with_hir_id_owner(None, |this| {
535 this.visit_pat(¶meter.pat);
537 self.visit_ty(¶meter.ty)
539 self.visit_fn_ret_ty(&f.decl.output)
541 _ => visit::walk_ty(self, t),
546 self.lower_node_id(CRATE_NODE_ID);
547 debug_assert!(self.node_id_to_hir_id[CRATE_NODE_ID] == Some(hir::CRATE_HIR_ID));
549 visit::walk_crate(&mut MiscCollector { lctx: &mut self, hir_id_owner: None }, c);
550 visit::walk_crate(&mut item::ItemLowerer { lctx: &mut self }, c);
552 let module = self.lower_mod(&c.module);
553 let attrs = self.lower_attrs(&c.attrs);
554 let body_ids = body_ids(&self.bodies);
556 c.proc_macros.iter().map(|id| self.node_id_to_hir_id[*id].unwrap()).collect();
562 .filter_map(|(&k, v)| {
563 self.node_id_to_hir_id.get(k).and_then(|id| id.as_ref()).map(|id| (*id, v.clone()))
567 let mut def_id_to_hir_id = IndexVec::default();
569 for (node_id, hir_id) in self.node_id_to_hir_id.into_iter_enumerated() {
570 if let Some(def_id) = self.resolver.opt_local_def_id(node_id) {
571 if def_id_to_hir_id.len() <= def_id.index() {
572 def_id_to_hir_id.resize(def_id.index() + 1, None);
574 def_id_to_hir_id[def_id] = hir_id;
578 self.resolver.definitions().init_def_id_to_hir_id_mapping(def_id_to_hir_id);
581 item: hir::CrateItem { module, attrs, span: c.span },
582 exported_macros: self.arena.alloc_from_iter(self.exported_macros),
583 non_exported_macro_attrs: self.arena.alloc_from_iter(self.non_exported_macro_attrs),
585 trait_items: self.trait_items,
586 impl_items: self.impl_items,
589 trait_impls: self.trait_impls,
590 modules: self.modules,
596 fn insert_item(&mut self, item: hir::Item<'hir>) {
597 let id = item.hir_id;
598 // FIXME: Use `debug_asset-rt`.
599 assert_eq!(id.local_id, hir::ItemLocalId::from_u32(0));
600 self.items.insert(id, item);
601 self.modules.get_mut(&self.current_module).unwrap().items.insert(id);
604 fn allocate_hir_id_counter(&mut self, owner: NodeId) -> hir::HirId {
605 // Set up the counter if needed.
606 self.item_local_id_counters.entry(owner).or_insert(0);
607 // Always allocate the first `HirId` for the owner itself.
608 let lowered = self.lower_node_id_with_owner(owner, owner);
609 debug_assert_eq!(lowered.local_id.as_u32(), 0);
613 fn lower_node_id_generic(
616 alloc_hir_id: impl FnOnce(&mut Self) -> hir::HirId,
618 assert_ne!(ast_node_id, DUMMY_NODE_ID);
620 let min_size = ast_node_id.as_usize() + 1;
622 if min_size > self.node_id_to_hir_id.len() {
623 self.node_id_to_hir_id.resize(min_size, None);
626 if let Some(existing_hir_id) = self.node_id_to_hir_id[ast_node_id] {
629 // Generate a new `HirId`.
630 let hir_id = alloc_hir_id(self);
631 self.node_id_to_hir_id[ast_node_id] = Some(hir_id);
637 fn with_hir_id_owner<T>(&mut self, owner: NodeId, f: impl FnOnce(&mut Self) -> T) -> T {
639 .item_local_id_counters
640 .insert(owner, HIR_ID_COUNTER_LOCKED)
641 .unwrap_or_else(|| panic!("no `item_local_id_counters` entry for {:?}", owner));
642 let def_id = self.resolver.local_def_id(owner);
643 self.current_hir_id_owner.push((def_id, counter));
645 let (new_def_id, new_counter) = self.current_hir_id_owner.pop().unwrap();
647 debug_assert!(def_id == new_def_id);
648 debug_assert!(new_counter >= counter);
650 let prev = self.item_local_id_counters.insert(owner, new_counter).unwrap();
651 debug_assert!(prev == HIR_ID_COUNTER_LOCKED);
655 /// This method allocates a new `HirId` for the given `NodeId` and stores it in
656 /// the `LoweringContext`'s `NodeId => HirId` map.
657 /// Take care not to call this method if the resulting `HirId` is then not
658 /// actually used in the HIR, as that would trigger an assertion in the
659 /// `HirIdValidator` later on, which makes sure that all `NodeId`s got mapped
660 /// properly. Calling the method twice with the same `NodeId` is fine though.
661 fn lower_node_id(&mut self, ast_node_id: NodeId) -> hir::HirId {
662 self.lower_node_id_generic(ast_node_id, |this| {
663 let &mut (owner, ref mut local_id_counter) =
664 this.current_hir_id_owner.last_mut().unwrap();
665 let local_id = *local_id_counter;
666 *local_id_counter += 1;
667 hir::HirId { owner, local_id: hir::ItemLocalId::from_u32(local_id) }
671 fn lower_node_id_with_owner(&mut self, ast_node_id: NodeId, owner: NodeId) -> hir::HirId {
672 self.lower_node_id_generic(ast_node_id, |this| {
673 let local_id_counter = this
674 .item_local_id_counters
676 .expect("called `lower_node_id_with_owner` before `allocate_hir_id_counter`");
677 let local_id = *local_id_counter;
679 // We want to be sure not to modify the counter in the map while it
680 // is also on the stack. Otherwise we'll get lost updates when writing
681 // back from the stack to the map.
682 debug_assert!(local_id != HIR_ID_COUNTER_LOCKED);
684 *local_id_counter += 1;
685 let owner = this.resolver.opt_local_def_id(owner).expect(
686 "you forgot to call `create_def` or are lowering node-IDs \
687 that do not belong to the current owner",
690 hir::HirId { owner, local_id: hir::ItemLocalId::from_u32(local_id) }
694 fn next_id(&mut self) -> hir::HirId {
695 let node_id = self.resolver.next_node_id();
696 self.lower_node_id(node_id)
699 fn lower_res(&mut self, res: Res<NodeId>) -> Res {
701 self.lower_node_id_generic(id, |_| {
702 panic!("expected `NodeId` to be lowered already for res {:#?}", res);
707 fn expect_full_res(&mut self, id: NodeId) -> Res<NodeId> {
708 self.resolver.get_partial_res(id).map_or(Res::Err, |pr| {
709 if pr.unresolved_segments() != 0 {
710 panic!("path not fully resolved: {:?}", pr);
716 fn expect_full_res_from_use(&mut self, id: NodeId) -> impl Iterator<Item = Res<NodeId>> {
717 self.resolver.get_import_res(id).present_items()
720 fn diagnostic(&self) -> &rustc_errors::Handler {
721 self.sess.diagnostic()
724 /// Reuses the span but adds information like the kind of the desugaring and features that are
725 /// allowed inside this span.
726 fn mark_span_with_reason(
728 reason: DesugaringKind,
730 allow_internal_unstable: Option<Lrc<[Symbol]>>,
732 span.fresh_expansion(ExpnData {
733 allow_internal_unstable,
734 ..ExpnData::default(ExpnKind::Desugaring(reason), span, self.sess.edition(), None)
738 fn with_anonymous_lifetime_mode<R>(
740 anonymous_lifetime_mode: AnonymousLifetimeMode,
741 op: impl FnOnce(&mut Self) -> R,
744 "with_anonymous_lifetime_mode(anonymous_lifetime_mode={:?})",
745 anonymous_lifetime_mode,
747 let old_anonymous_lifetime_mode = self.anonymous_lifetime_mode;
748 self.anonymous_lifetime_mode = anonymous_lifetime_mode;
749 let result = op(self);
750 self.anonymous_lifetime_mode = old_anonymous_lifetime_mode;
752 "with_anonymous_lifetime_mode: restoring anonymous_lifetime_mode={:?}",
753 old_anonymous_lifetime_mode
758 /// Creates a new `hir::GenericParam` for every new lifetime and
759 /// type parameter encountered while evaluating `f`. Definitions
760 /// are created with the parent provided. If no `parent_id` is
761 /// provided, no definitions will be returned.
763 /// Presuming that in-band lifetimes are enabled, then
764 /// `self.anonymous_lifetime_mode` will be updated to match the
765 /// parameter while `f` is running (and restored afterwards).
766 fn collect_in_band_defs<T>(
768 parent_def_id: LocalDefId,
769 anonymous_lifetime_mode: AnonymousLifetimeMode,
770 f: impl FnOnce(&mut Self) -> (Vec<hir::GenericParam<'hir>>, T),
771 ) -> (Vec<hir::GenericParam<'hir>>, T) {
772 assert!(!self.is_collecting_in_band_lifetimes);
773 assert!(self.lifetimes_to_define.is_empty());
774 let old_anonymous_lifetime_mode = self.anonymous_lifetime_mode;
776 self.anonymous_lifetime_mode = anonymous_lifetime_mode;
777 self.is_collecting_in_band_lifetimes = true;
779 let (in_band_ty_params, res) = f(self);
781 self.is_collecting_in_band_lifetimes = false;
782 self.anonymous_lifetime_mode = old_anonymous_lifetime_mode;
784 let lifetimes_to_define = self.lifetimes_to_define.split_off(0);
786 let params = lifetimes_to_define
788 .map(|(span, hir_name)| self.lifetime_to_generic_param(span, hir_name, parent_def_id))
789 .chain(in_band_ty_params.into_iter())
795 /// Converts a lifetime into a new generic parameter.
796 fn lifetime_to_generic_param(
800 parent_def_id: LocalDefId,
801 ) -> hir::GenericParam<'hir> {
802 let node_id = self.resolver.next_node_id();
804 // Get the name we'll use to make the def-path. Note
805 // that collisions are ok here and this shouldn't
806 // really show up for end-user.
807 let (str_name, kind) = match hir_name {
808 ParamName::Plain(ident) => (ident.name, hir::LifetimeParamKind::InBand),
809 ParamName::Fresh(_) => (kw::UnderscoreLifetime, hir::LifetimeParamKind::Elided),
810 ParamName::Error => (kw::UnderscoreLifetime, hir::LifetimeParamKind::Error),
813 // Add a definition for the in-band lifetime def.
814 self.resolver.create_def(
817 DefPathData::LifetimeNs(str_name),
823 hir_id: self.lower_node_id(node_id),
828 pure_wrt_drop: false,
829 kind: hir::GenericParamKind::Lifetime { kind },
833 /// When there is a reference to some lifetime `'a`, and in-band
834 /// lifetimes are enabled, then we want to push that lifetime into
835 /// the vector of names to define later. In that case, it will get
836 /// added to the appropriate generics.
837 fn maybe_collect_in_band_lifetime(&mut self, ident: Ident) {
838 if !self.is_collecting_in_band_lifetimes {
842 if !self.sess.features_untracked().in_band_lifetimes {
846 if self.in_scope_lifetimes.contains(&ParamName::Plain(ident.normalize_to_macros_2_0())) {
850 let hir_name = ParamName::Plain(ident);
852 if self.lifetimes_to_define.iter().any(|(_, lt_name)| {
853 lt_name.normalize_to_macros_2_0() == hir_name.normalize_to_macros_2_0()
858 self.lifetimes_to_define.push((ident.span, hir_name));
861 /// When we have either an elided or `'_` lifetime in an impl
862 /// header, we convert it to an in-band lifetime.
863 fn collect_fresh_in_band_lifetime(&mut self, span: Span) -> ParamName {
864 assert!(self.is_collecting_in_band_lifetimes);
865 let index = self.lifetimes_to_define.len() + self.in_scope_lifetimes.len();
866 let hir_name = ParamName::Fresh(index);
867 self.lifetimes_to_define.push((span, hir_name));
871 // Evaluates `f` with the lifetimes in `params` in-scope.
872 // This is used to track which lifetimes have already been defined, and
873 // which are new in-band lifetimes that need to have a definition created
875 fn with_in_scope_lifetime_defs<T>(
877 params: &[GenericParam],
878 f: impl FnOnce(&mut Self) -> T,
880 let old_len = self.in_scope_lifetimes.len();
881 let lt_def_names = params.iter().filter_map(|param| match param.kind {
882 GenericParamKind::Lifetime { .. } => {
883 Some(ParamName::Plain(param.ident.normalize_to_macros_2_0()))
887 self.in_scope_lifetimes.extend(lt_def_names);
891 self.in_scope_lifetimes.truncate(old_len);
895 /// Appends in-band lifetime defs and argument-position `impl
896 /// Trait` defs to the existing set of generics.
898 /// Presuming that in-band lifetimes are enabled, then
899 /// `self.anonymous_lifetime_mode` will be updated to match the
900 /// parameter while `f` is running (and restored afterwards).
901 fn add_in_band_defs<T>(
904 parent_def_id: LocalDefId,
905 anonymous_lifetime_mode: AnonymousLifetimeMode,
906 f: impl FnOnce(&mut Self, &mut Vec<hir::GenericParam<'hir>>) -> T,
907 ) -> (hir::Generics<'hir>, T) {
908 let (in_band_defs, (mut lowered_generics, res)) =
909 self.with_in_scope_lifetime_defs(&generics.params, |this| {
910 this.collect_in_band_defs(parent_def_id, anonymous_lifetime_mode, |this| {
911 let mut params = Vec::new();
912 // Note: it is necessary to lower generics *before* calling `f`.
913 // When lowering `async fn`, there's a final step when lowering
914 // the return type that assumes that all in-scope lifetimes have
915 // already been added to either `in_scope_lifetimes` or
916 // `lifetimes_to_define`. If we swapped the order of these two,
917 // in-band-lifetimes introduced by generics or where-clauses
918 // wouldn't have been added yet.
920 this.lower_generics_mut(generics, ImplTraitContext::Universal(&mut params));
921 let res = f(this, &mut params);
922 (params, (generics, res))
926 lowered_generics.params.extend(in_band_defs);
928 let lowered_generics = lowered_generics.into_generics(self.arena);
929 (lowered_generics, res)
932 fn with_dyn_type_scope<T>(&mut self, in_scope: bool, f: impl FnOnce(&mut Self) -> T) -> T {
933 let was_in_dyn_type = self.is_in_dyn_type;
934 self.is_in_dyn_type = in_scope;
936 let result = f(self);
938 self.is_in_dyn_type = was_in_dyn_type;
943 fn with_new_scopes<T>(&mut self, f: impl FnOnce(&mut Self) -> T) -> T {
944 let was_in_loop_condition = self.is_in_loop_condition;
945 self.is_in_loop_condition = false;
947 let catch_scopes = mem::take(&mut self.catch_scopes);
948 let loop_scopes = mem::take(&mut self.loop_scopes);
950 self.catch_scopes = catch_scopes;
951 self.loop_scopes = loop_scopes;
953 self.is_in_loop_condition = was_in_loop_condition;
958 fn lower_attrs(&mut self, attrs: &[Attribute]) -> &'hir [Attribute] {
959 self.arena.alloc_from_iter(attrs.iter().map(|a| self.lower_attr(a)))
962 fn lower_attr(&mut self, attr: &Attribute) -> Attribute {
963 // Note that we explicitly do not walk the path. Since we don't really
964 // lower attributes (we use the AST version) there is nowhere to keep
965 // the `HirId`s. We don't actually need HIR version of attributes anyway.
966 let kind = match attr.kind {
967 AttrKind::Normal(ref item) => AttrKind::Normal(AttrItem {
968 path: item.path.clone(),
969 args: self.lower_mac_args(&item.args),
971 AttrKind::DocComment(comment_kind, data) => AttrKind::DocComment(comment_kind, data),
974 Attribute { kind, id: attr.id, style: attr.style, span: attr.span }
977 fn lower_mac_args(&mut self, args: &MacArgs) -> MacArgs {
979 MacArgs::Empty => MacArgs::Empty,
980 MacArgs::Delimited(dspan, delim, ref tokens) => {
981 MacArgs::Delimited(dspan, delim, self.lower_token_stream(tokens.clone()))
983 MacArgs::Eq(eq_span, ref tokens) => {
984 MacArgs::Eq(eq_span, self.lower_token_stream(tokens.clone()))
989 fn lower_token_stream(&mut self, tokens: TokenStream) -> TokenStream {
990 tokens.into_trees().flat_map(|tree| self.lower_token_tree(tree).into_trees()).collect()
993 fn lower_token_tree(&mut self, tree: TokenTree) -> TokenStream {
995 TokenTree::Token(token) => self.lower_token(token),
996 TokenTree::Delimited(span, delim, tts) => {
997 TokenTree::Delimited(span, delim, self.lower_token_stream(tts)).into()
1002 fn lower_token(&mut self, token: Token) -> TokenStream {
1004 token::Interpolated(nt) => {
1005 let tts = (self.nt_to_tokenstream)(&nt, &self.sess.parse_sess, token.span);
1006 TokenTree::Delimited(
1007 DelimSpan::from_single(token.span),
1008 DelimToken::NoDelim,
1009 self.lower_token_stream(tts),
1013 _ => TokenTree::Token(token).into(),
1017 /// Given an associated type constraint like one of these:
1020 /// T: Iterator<Item: Debug>
1022 /// T: Iterator<Item = Debug>
1026 /// returns a `hir::TypeBinding` representing `Item`.
1027 fn lower_assoc_ty_constraint(
1029 constraint: &AssocTyConstraint,
1030 itctx: ImplTraitContext<'_, 'hir>,
1031 ) -> hir::TypeBinding<'hir> {
1032 debug!("lower_assoc_ty_constraint(constraint={:?}, itctx={:?})", constraint, itctx);
1034 let kind = match constraint.kind {
1035 AssocTyConstraintKind::Equality { ref ty } => {
1036 hir::TypeBindingKind::Equality { ty: self.lower_ty(ty, itctx) }
1038 AssocTyConstraintKind::Bound { ref bounds } => {
1039 let mut capturable_lifetimes;
1040 // Piggy-back on the `impl Trait` context to figure out the correct behavior.
1041 let (desugar_to_impl_trait, itctx) = match itctx {
1042 // We are in the return position:
1044 // fn foo() -> impl Iterator<Item: Debug>
1048 // fn foo() -> impl Iterator<Item = impl Debug>
1049 ImplTraitContext::ReturnPositionOpaqueTy { .. }
1050 | ImplTraitContext::OtherOpaqueTy { .. } => (true, itctx),
1052 // We are in the argument position, but within a dyn type:
1054 // fn foo(x: dyn Iterator<Item: Debug>)
1058 // fn foo(x: dyn Iterator<Item = impl Debug>)
1059 ImplTraitContext::Universal(..) if self.is_in_dyn_type => (true, itctx),
1061 // In `type Foo = dyn Iterator<Item: Debug>` we desugar to
1062 // `type Foo = dyn Iterator<Item = impl Debug>` but we have to override the
1063 // "impl trait context" to permit `impl Debug` in this position (it desugars
1064 // then to an opaque type).
1066 // FIXME: this is only needed until `impl Trait` is allowed in type aliases.
1067 ImplTraitContext::Disallowed(_) if self.is_in_dyn_type => {
1068 capturable_lifetimes = FxHashSet::default();
1071 ImplTraitContext::OtherOpaqueTy {
1072 capturable_lifetimes: &mut capturable_lifetimes,
1073 origin: hir::OpaqueTyOrigin::Misc,
1078 // We are in the parameter position, but not within a dyn type:
1080 // fn foo(x: impl Iterator<Item: Debug>)
1082 // so we leave it as is and this gets expanded in astconv to a bound like
1083 // `<T as Iterator>::Item: Debug` where `T` is the type parameter for the
1085 _ => (false, itctx),
1088 if desugar_to_impl_trait {
1089 // Desugar `AssocTy: Bounds` into `AssocTy = impl Bounds`. We do this by
1090 // constructing the HIR for `impl bounds...` and then lowering that.
1092 let impl_trait_node_id = self.resolver.next_node_id();
1093 let parent_def_id = self.current_hir_id_owner.last().unwrap().0;
1094 self.resolver.create_def(
1097 DefPathData::ImplTrait,
1102 self.with_dyn_type_scope(false, |this| {
1103 let node_id = this.resolver.next_node_id();
1104 let ty = this.lower_ty(
1107 kind: TyKind::ImplTrait(impl_trait_node_id, bounds.clone()),
1108 span: constraint.span,
1113 hir::TypeBindingKind::Equality { ty }
1116 // Desugar `AssocTy: Bounds` into a type binding where the
1117 // later desugars into a trait predicate.
1118 let bounds = self.lower_param_bounds(bounds, itctx);
1120 hir::TypeBindingKind::Constraint { bounds }
1126 hir_id: self.lower_node_id(constraint.id),
1127 ident: constraint.ident,
1129 span: constraint.span,
1133 fn lower_generic_arg(
1135 arg: &ast::GenericArg,
1136 itctx: ImplTraitContext<'_, 'hir>,
1137 ) -> hir::GenericArg<'hir> {
1139 ast::GenericArg::Lifetime(lt) => GenericArg::Lifetime(self.lower_lifetime(<)),
1140 ast::GenericArg::Type(ty) => {
1141 // We parse const arguments as path types as we cannot distinguish them during
1142 // parsing. We try to resolve that ambiguity by attempting resolution in both the
1143 // type and value namespaces. If we resolved the path in the value namespace, we
1144 // transform it into a generic const argument.
1145 if let TyKind::Path(ref qself, ref path) = ty.kind {
1146 if let Some(partial_res) = self.resolver.get_partial_res(ty.id) {
1147 let res = partial_res.base_res();
1148 if !res.matches_ns(Namespace::TypeNS) {
1150 "lower_generic_arg: Lowering type argument as const argument: {:?}",
1154 // Construct a AnonConst where the expr is the "ty"'s path.
1156 let parent_def_id = self.current_hir_id_owner.last().unwrap().0;
1157 let node_id = self.resolver.next_node_id();
1159 // Add a definition for the in-band const def.
1160 self.resolver.create_def(
1163 DefPathData::AnonConst,
1168 let path_expr = Expr {
1170 kind: ExprKind::Path(qself.clone(), path.clone()),
1172 attrs: AttrVec::new(),
1176 let ct = self.with_new_scopes(|this| hir::AnonConst {
1177 hir_id: this.lower_node_id(node_id),
1178 body: this.lower_const_body(path_expr.span, Some(&path_expr)),
1180 return GenericArg::Const(ConstArg { value: ct, span: ty.span });
1184 GenericArg::Type(self.lower_ty_direct(&ty, itctx))
1186 ast::GenericArg::Const(ct) => GenericArg::Const(ConstArg {
1187 value: self.lower_anon_const(&ct),
1188 span: ct.value.span,
1193 fn lower_ty(&mut self, t: &Ty, itctx: ImplTraitContext<'_, 'hir>) -> &'hir hir::Ty<'hir> {
1194 self.arena.alloc(self.lower_ty_direct(t, itctx))
1200 qself: &Option<QSelf>,
1202 param_mode: ParamMode,
1203 itctx: ImplTraitContext<'_, 'hir>,
1204 ) -> hir::Ty<'hir> {
1205 let id = self.lower_node_id(t.id);
1206 let qpath = self.lower_qpath(t.id, qself, path, param_mode, itctx);
1207 let ty = self.ty_path(id, t.span, qpath);
1208 if let hir::TyKind::TraitObject(..) = ty.kind {
1209 self.maybe_lint_bare_trait(t.span, t.id, qself.is_none() && path.is_global());
1214 fn ty(&mut self, span: Span, kind: hir::TyKind<'hir>) -> hir::Ty<'hir> {
1215 hir::Ty { hir_id: self.next_id(), kind, span }
1218 fn ty_tup(&mut self, span: Span, tys: &'hir [hir::Ty<'hir>]) -> hir::Ty<'hir> {
1219 self.ty(span, hir::TyKind::Tup(tys))
1222 fn lower_ty_direct(&mut self, t: &Ty, mut itctx: ImplTraitContext<'_, 'hir>) -> hir::Ty<'hir> {
1223 let kind = match t.kind {
1224 TyKind::Infer => hir::TyKind::Infer,
1225 TyKind::Err => hir::TyKind::Err,
1226 TyKind::Slice(ref ty) => hir::TyKind::Slice(self.lower_ty(ty, itctx)),
1227 TyKind::Ptr(ref mt) => hir::TyKind::Ptr(self.lower_mt(mt, itctx)),
1228 TyKind::Rptr(ref region, ref mt) => {
1229 let span = self.sess.source_map().next_point(t.span.shrink_to_lo());
1230 let lifetime = match *region {
1231 Some(ref lt) => self.lower_lifetime(lt),
1232 None => self.elided_ref_lifetime(span),
1234 hir::TyKind::Rptr(lifetime, self.lower_mt(mt, itctx))
1236 TyKind::BareFn(ref f) => self.with_in_scope_lifetime_defs(&f.generic_params, |this| {
1237 this.with_anonymous_lifetime_mode(AnonymousLifetimeMode::PassThrough, |this| {
1238 hir::TyKind::BareFn(this.arena.alloc(hir::BareFnTy {
1239 generic_params: this.lower_generic_params(
1241 &NodeMap::default(),
1242 ImplTraitContext::disallowed(),
1244 unsafety: this.lower_unsafety(f.unsafety),
1245 abi: this.lower_extern(f.ext),
1246 decl: this.lower_fn_decl(&f.decl, None, false, None),
1247 param_names: this.lower_fn_params_to_names(&f.decl),
1251 TyKind::Never => hir::TyKind::Never,
1252 TyKind::Tup(ref tys) => {
1253 hir::TyKind::Tup(self.arena.alloc_from_iter(
1254 tys.iter().map(|ty| self.lower_ty_direct(ty, itctx.reborrow())),
1257 TyKind::Paren(ref ty) => {
1258 return self.lower_ty_direct(ty, itctx);
1260 TyKind::Path(ref qself, ref path) => {
1261 return self.lower_path_ty(t, qself, path, ParamMode::Explicit, itctx);
1263 TyKind::ImplicitSelf => {
1264 let res = self.expect_full_res(t.id);
1265 let res = self.lower_res(res);
1266 hir::TyKind::Path(hir::QPath::Resolved(
1268 self.arena.alloc(hir::Path {
1270 segments: arena_vec![self; hir::PathSegment::from_ident(
1271 Ident::with_dummy_span(kw::SelfUpper)
1277 TyKind::Array(ref ty, ref length) => {
1278 hir::TyKind::Array(self.lower_ty(ty, itctx), self.lower_anon_const(length))
1280 TyKind::Typeof(ref expr) => hir::TyKind::Typeof(self.lower_anon_const(expr)),
1281 TyKind::TraitObject(ref bounds, kind) => {
1282 let mut lifetime_bound = None;
1283 let (bounds, lifetime_bound) = self.with_dyn_type_scope(true, |this| {
1285 this.arena.alloc_from_iter(bounds.iter().filter_map(
1286 |bound| match *bound {
1287 GenericBound::Trait(
1289 TraitBoundModifier::None | TraitBoundModifier::MaybeConst,
1290 ) => Some(this.lower_poly_trait_ref(ty, itctx.reborrow())),
1291 // `?const ?Bound` will cause an error during AST validation
1292 // anyways, so treat it like `?Bound` as compilation proceeds.
1293 GenericBound::Trait(
1295 TraitBoundModifier::Maybe | TraitBoundModifier::MaybeConstMaybe,
1297 GenericBound::Outlives(ref lifetime) => {
1298 if lifetime_bound.is_none() {
1299 lifetime_bound = Some(this.lower_lifetime(lifetime));
1305 let lifetime_bound =
1306 lifetime_bound.unwrap_or_else(|| this.elided_dyn_bound(t.span));
1307 (bounds, lifetime_bound)
1309 if kind != TraitObjectSyntax::Dyn {
1310 self.maybe_lint_bare_trait(t.span, t.id, false);
1312 hir::TyKind::TraitObject(bounds, lifetime_bound)
1314 TyKind::ImplTrait(def_node_id, ref bounds) => {
1317 ImplTraitContext::ReturnPositionOpaqueTy { fn_def_id, origin } => self
1318 .lower_opaque_impl_trait(
1324 |this| this.lower_param_bounds(bounds, itctx),
1326 ImplTraitContext::OtherOpaqueTy { ref capturable_lifetimes, origin } => {
1327 // Reset capturable lifetimes, any nested impl trait
1328 // types will inherit lifetimes from this opaque type,
1329 // so don't need to capture them again.
1330 let nested_itctx = ImplTraitContext::OtherOpaqueTy {
1331 capturable_lifetimes: &mut FxHashSet::default(),
1334 self.lower_opaque_impl_trait(
1339 Some(capturable_lifetimes),
1340 |this| this.lower_param_bounds(bounds, nested_itctx),
1343 ImplTraitContext::Universal(in_band_ty_params) => {
1344 // Add a definition for the in-band `Param`.
1345 let def_id = self.resolver.local_def_id(def_node_id);
1347 let hir_bounds = self.lower_param_bounds(
1349 ImplTraitContext::Universal(in_band_ty_params),
1351 // Set the name to `impl Bound1 + Bound2`.
1352 let ident = Ident::from_str_and_span(&pprust::ty_to_string(t), span);
1353 in_band_ty_params.push(hir::GenericParam {
1354 hir_id: self.lower_node_id(def_node_id),
1355 name: ParamName::Plain(ident),
1356 pure_wrt_drop: false,
1360 kind: hir::GenericParamKind::Type {
1362 synthetic: Some(hir::SyntheticTyParamKind::ImplTrait),
1366 hir::TyKind::Path(hir::QPath::Resolved(
1368 self.arena.alloc(hir::Path {
1370 res: Res::Def(DefKind::TyParam, def_id.to_def_id()),
1371 segments: arena_vec![self; hir::PathSegment::from_ident(ident)],
1375 ImplTraitContext::Disallowed(pos) => {
1376 let allowed_in = if self.sess.features_untracked().impl_trait_in_bindings {
1377 "bindings or function and inherent method return types"
1379 "function and inherent method return types"
1381 let mut err = struct_span_err!(
1385 "`impl Trait` not allowed outside of {}",
1388 if pos == ImplTraitPosition::Binding && nightly_options::is_nightly_build()
1391 "add `#![feature(impl_trait_in_bindings)]` to the crate \
1392 attributes to enable",
1400 TyKind::MacCall(_) => panic!("`TyKind::MacCall` should have been expanded by now"),
1401 TyKind::CVarArgs => {
1402 self.sess.delay_span_bug(
1404 "`TyKind::CVarArgs` should have been handled elsewhere",
1410 hir::Ty { kind, span: t.span, hir_id: self.lower_node_id(t.id) }
1413 fn lower_opaque_impl_trait(
1416 fn_def_id: Option<DefId>,
1417 origin: hir::OpaqueTyOrigin,
1418 opaque_ty_node_id: NodeId,
1419 capturable_lifetimes: Option<&FxHashSet<hir::LifetimeName>>,
1420 lower_bounds: impl FnOnce(&mut Self) -> hir::GenericBounds<'hir>,
1421 ) -> hir::TyKind<'hir> {
1423 "lower_opaque_impl_trait(fn_def_id={:?}, opaque_ty_node_id={:?}, span={:?})",
1424 fn_def_id, opaque_ty_node_id, span,
1427 // Make sure we know that some funky desugaring has been going on here.
1428 // This is a first: there is code in other places like for loop
1429 // desugaring that explicitly states that we don't want to track that.
1430 // Not tracking it makes lints in rustc and clippy very fragile, as
1431 // frequently opened issues show.
1432 let opaque_ty_span = self.mark_span_with_reason(DesugaringKind::OpaqueTy, span, None);
1434 let opaque_ty_def_id = self.resolver.local_def_id(opaque_ty_node_id);
1436 self.allocate_hir_id_counter(opaque_ty_node_id);
1438 let hir_bounds = self.with_hir_id_owner(opaque_ty_node_id, lower_bounds);
1440 let (lifetimes, lifetime_defs) = self.lifetimes_from_impl_trait_bounds(
1444 capturable_lifetimes,
1447 debug!("lower_opaque_impl_trait: lifetimes={:#?}", lifetimes);
1449 debug!("lower_opaque_impl_trait: lifetime_defs={:#?}", lifetime_defs);
1451 self.with_hir_id_owner(opaque_ty_node_id, move |lctx| {
1452 let opaque_ty_item = hir::OpaqueTy {
1453 generics: hir::Generics {
1454 params: lifetime_defs,
1455 where_clause: hir::WhereClause { predicates: &[], span },
1459 impl_trait_fn: fn_def_id,
1463 trace!("lower_opaque_impl_trait: {:#?}", opaque_ty_def_id);
1465 lctx.generate_opaque_type(opaque_ty_node_id, opaque_ty_item, span, opaque_ty_span);
1467 // `impl Trait` now just becomes `Foo<'a, 'b, ..>`.
1468 hir::TyKind::OpaqueDef(hir::ItemId { id: opaque_ty_id }, lifetimes)
1472 /// Registers a new opaque type with the proper `NodeId`s and
1473 /// returns the lowered node-ID for the opaque type.
1474 fn generate_opaque_type(
1476 opaque_ty_node_id: NodeId,
1477 opaque_ty_item: hir::OpaqueTy<'hir>,
1479 opaque_ty_span: Span,
1481 let opaque_ty_item_kind = hir::ItemKind::OpaqueTy(opaque_ty_item);
1482 let opaque_ty_id = self.lower_node_id(opaque_ty_node_id);
1483 // Generate an `type Foo = impl Trait;` declaration.
1484 trace!("registering opaque type with id {:#?}", opaque_ty_id);
1485 let opaque_ty_item = hir::Item {
1486 hir_id: opaque_ty_id,
1487 ident: Ident::invalid(),
1488 attrs: Default::default(),
1489 kind: opaque_ty_item_kind,
1490 vis: respan(span.shrink_to_lo(), hir::VisibilityKind::Inherited),
1491 span: opaque_ty_span,
1494 // Insert the item into the global item list. This usually happens
1495 // automatically for all AST items. But this opaque type item
1496 // does not actually exist in the AST.
1497 self.insert_item(opaque_ty_item);
1501 fn lifetimes_from_impl_trait_bounds(
1503 opaque_ty_id: NodeId,
1504 parent_def_id: LocalDefId,
1505 bounds: hir::GenericBounds<'hir>,
1506 lifetimes_to_include: Option<&FxHashSet<hir::LifetimeName>>,
1507 ) -> (&'hir [hir::GenericArg<'hir>], &'hir [hir::GenericParam<'hir>]) {
1509 "lifetimes_from_impl_trait_bounds(opaque_ty_id={:?}, \
1510 parent_def_id={:?}, \
1512 opaque_ty_id, parent_def_id, bounds,
1515 // This visitor walks over `impl Trait` bounds and creates defs for all lifetimes that
1516 // appear in the bounds, excluding lifetimes that are created within the bounds.
1517 // E.g., `'a`, `'b`, but not `'c` in `impl for<'c> SomeTrait<'a, 'b, 'c>`.
1518 struct ImplTraitLifetimeCollector<'r, 'a, 'hir> {
1519 context: &'r mut LoweringContext<'a, 'hir>,
1521 opaque_ty_id: NodeId,
1522 collect_elided_lifetimes: bool,
1523 currently_bound_lifetimes: Vec<hir::LifetimeName>,
1524 already_defined_lifetimes: FxHashSet<hir::LifetimeName>,
1525 output_lifetimes: Vec<hir::GenericArg<'hir>>,
1526 output_lifetime_params: Vec<hir::GenericParam<'hir>>,
1527 lifetimes_to_include: Option<&'r FxHashSet<hir::LifetimeName>>,
1530 impl<'r, 'a, 'v, 'hir> intravisit::Visitor<'v> for ImplTraitLifetimeCollector<'r, 'a, 'hir> {
1531 type Map = intravisit::ErasedMap<'v>;
1533 fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
1534 intravisit::NestedVisitorMap::None
1537 fn visit_generic_args(&mut self, span: Span, parameters: &'v hir::GenericArgs<'v>) {
1538 // Don't collect elided lifetimes used inside of `Fn()` syntax.
1539 if parameters.parenthesized {
1540 let old_collect_elided_lifetimes = self.collect_elided_lifetimes;
1541 self.collect_elided_lifetimes = false;
1542 intravisit::walk_generic_args(self, span, parameters);
1543 self.collect_elided_lifetimes = old_collect_elided_lifetimes;
1545 intravisit::walk_generic_args(self, span, parameters);
1549 fn visit_ty(&mut self, t: &'v hir::Ty<'v>) {
1550 // Don't collect elided lifetimes used inside of `fn()` syntax.
1551 if let hir::TyKind::BareFn(_) = t.kind {
1552 let old_collect_elided_lifetimes = self.collect_elided_lifetimes;
1553 self.collect_elided_lifetimes = false;
1555 // Record the "stack height" of `for<'a>` lifetime bindings
1556 // to be able to later fully undo their introduction.
1557 let old_len = self.currently_bound_lifetimes.len();
1558 intravisit::walk_ty(self, t);
1559 self.currently_bound_lifetimes.truncate(old_len);
1561 self.collect_elided_lifetimes = old_collect_elided_lifetimes;
1563 intravisit::walk_ty(self, t)
1567 fn visit_poly_trait_ref(
1569 trait_ref: &'v hir::PolyTraitRef<'v>,
1570 modifier: hir::TraitBoundModifier,
1572 // Record the "stack height" of `for<'a>` lifetime bindings
1573 // to be able to later fully undo their introduction.
1574 let old_len = self.currently_bound_lifetimes.len();
1575 intravisit::walk_poly_trait_ref(self, trait_ref, modifier);
1576 self.currently_bound_lifetimes.truncate(old_len);
1579 fn visit_generic_param(&mut self, param: &'v hir::GenericParam<'v>) {
1580 // Record the introduction of 'a in `for<'a> ...`.
1581 if let hir::GenericParamKind::Lifetime { .. } = param.kind {
1582 // Introduce lifetimes one at a time so that we can handle
1583 // cases like `fn foo<'d>() -> impl for<'a, 'b: 'a, 'c: 'b + 'd>`.
1584 let lt_name = hir::LifetimeName::Param(param.name);
1585 self.currently_bound_lifetimes.push(lt_name);
1588 intravisit::walk_generic_param(self, param);
1591 fn visit_lifetime(&mut self, lifetime: &'v hir::Lifetime) {
1592 let name = match lifetime.name {
1593 hir::LifetimeName::Implicit | hir::LifetimeName::Underscore => {
1594 if self.collect_elided_lifetimes {
1595 // Use `'_` for both implicit and underscore lifetimes in
1596 // `type Foo<'_> = impl SomeTrait<'_>;`.
1597 hir::LifetimeName::Underscore
1602 hir::LifetimeName::Param(_) => lifetime.name,
1604 // Refers to some other lifetime that is "in
1605 // scope" within the type.
1606 hir::LifetimeName::ImplicitObjectLifetimeDefault => return,
1608 hir::LifetimeName::Error | hir::LifetimeName::Static => return,
1611 if !self.currently_bound_lifetimes.contains(&name)
1612 && !self.already_defined_lifetimes.contains(&name)
1613 && self.lifetimes_to_include.map_or(true, |lifetimes| lifetimes.contains(&name))
1615 self.already_defined_lifetimes.insert(name);
1617 self.output_lifetimes.push(hir::GenericArg::Lifetime(hir::Lifetime {
1618 hir_id: self.context.next_id(),
1619 span: lifetime.span,
1623 let def_node_id = self.context.resolver.next_node_id();
1625 self.context.lower_node_id_with_owner(def_node_id, self.opaque_ty_id);
1626 self.context.resolver.create_def(
1629 DefPathData::LifetimeNs(name.ident().name),
1634 let (name, kind) = match name {
1635 hir::LifetimeName::Underscore => (
1636 hir::ParamName::Plain(Ident::with_dummy_span(kw::UnderscoreLifetime)),
1637 hir::LifetimeParamKind::Elided,
1639 hir::LifetimeName::Param(param_name) => {
1640 (param_name, hir::LifetimeParamKind::Explicit)
1642 _ => panic!("expected `LifetimeName::Param` or `ParamName::Plain`"),
1645 self.output_lifetime_params.push(hir::GenericParam {
1648 span: lifetime.span,
1649 pure_wrt_drop: false,
1652 kind: hir::GenericParamKind::Lifetime { kind },
1658 let mut lifetime_collector = ImplTraitLifetimeCollector {
1660 parent: parent_def_id,
1662 collect_elided_lifetimes: true,
1663 currently_bound_lifetimes: Vec::new(),
1664 already_defined_lifetimes: FxHashSet::default(),
1665 output_lifetimes: Vec::new(),
1666 output_lifetime_params: Vec::new(),
1667 lifetimes_to_include,
1670 for bound in bounds {
1671 intravisit::walk_param_bound(&mut lifetime_collector, &bound);
1674 let ImplTraitLifetimeCollector { output_lifetimes, output_lifetime_params, .. } =
1678 self.arena.alloc_from_iter(output_lifetimes),
1679 self.arena.alloc_from_iter(output_lifetime_params),
1683 fn lower_local(&mut self, l: &Local) -> (hir::Local<'hir>, SmallVec<[NodeId; 1]>) {
1684 let mut ids = SmallVec::<[NodeId; 1]>::new();
1685 if self.sess.features_untracked().impl_trait_in_bindings {
1686 if let Some(ref ty) = l.ty {
1687 let mut visitor = ImplTraitTypeIdVisitor { ids: &mut ids };
1688 visitor.visit_ty(ty);
1691 let ty = l.ty.as_ref().map(|t| {
1692 let mut capturable_lifetimes;
1695 if self.sess.features_untracked().impl_trait_in_bindings {
1696 capturable_lifetimes = FxHashSet::default();
1697 ImplTraitContext::OtherOpaqueTy {
1698 capturable_lifetimes: &mut capturable_lifetimes,
1699 origin: hir::OpaqueTyOrigin::Binding,
1702 ImplTraitContext::Disallowed(ImplTraitPosition::Binding)
1706 let init = l.init.as_ref().map(|e| self.lower_expr(e));
1709 hir_id: self.lower_node_id(l.id),
1711 pat: self.lower_pat(&l.pat),
1714 attrs: l.attrs.clone(),
1715 source: hir::LocalSource::Normal,
1721 fn lower_fn_params_to_names(&mut self, decl: &FnDecl) -> &'hir [Ident] {
1722 // Skip the `...` (`CVarArgs`) trailing arguments from the AST,
1723 // as they are not explicit in HIR/Ty function signatures.
1724 // (instead, the `c_variadic` flag is set to `true`)
1725 let mut inputs = &decl.inputs[..];
1726 if decl.c_variadic() {
1727 inputs = &inputs[..inputs.len() - 1];
1729 self.arena.alloc_from_iter(inputs.iter().map(|param| match param.pat.kind {
1730 PatKind::Ident(_, ident, _) => ident,
1731 _ => Ident::new(kw::Invalid, param.pat.span),
1735 // Lowers a function declaration.
1737 // `decl`: the unlowered (AST) function declaration.
1738 // `fn_def_id`: if `Some`, impl Trait arguments are lowered into generic parameters on the
1739 // given DefId, otherwise impl Trait is disallowed. Must be `Some` if
1740 // `make_ret_async` is also `Some`.
1741 // `impl_trait_return_allow`: determines whether `impl Trait` can be used in return position.
1742 // This guards against trait declarations and implementations where `impl Trait` is
1744 // `make_ret_async`: if `Some`, converts `-> T` into `-> impl Future<Output = T>` in the
1745 // return type. This is used for `async fn` declarations. The `NodeId` is the ID of the
1746 // return type `impl Trait` item.
1750 mut in_band_ty_params: Option<(DefId, &mut Vec<hir::GenericParam<'hir>>)>,
1751 impl_trait_return_allow: bool,
1752 make_ret_async: Option<NodeId>,
1753 ) -> &'hir hir::FnDecl<'hir> {
1757 in_band_ty_params: {:?}, \
1758 impl_trait_return_allow: {}, \
1759 make_ret_async: {:?})",
1760 decl, in_band_ty_params, impl_trait_return_allow, make_ret_async,
1762 let lt_mode = if make_ret_async.is_some() {
1763 // In `async fn`, argument-position elided lifetimes
1764 // must be transformed into fresh generic parameters so that
1765 // they can be applied to the opaque `impl Trait` return type.
1766 AnonymousLifetimeMode::CreateParameter
1768 self.anonymous_lifetime_mode
1771 let c_variadic = decl.c_variadic();
1773 // Remember how many lifetimes were already around so that we can
1774 // only look at the lifetime parameters introduced by the arguments.
1775 let inputs = self.with_anonymous_lifetime_mode(lt_mode, |this| {
1776 // Skip the `...` (`CVarArgs`) trailing arguments from the AST,
1777 // as they are not explicit in HIR/Ty function signatures.
1778 // (instead, the `c_variadic` flag is set to `true`)
1779 let mut inputs = &decl.inputs[..];
1781 inputs = &inputs[..inputs.len() - 1];
1783 this.arena.alloc_from_iter(inputs.iter().map(|param| {
1784 if let Some((_, ibty)) = &mut in_band_ty_params {
1785 this.lower_ty_direct(¶m.ty, ImplTraitContext::Universal(ibty))
1787 this.lower_ty_direct(¶m.ty, ImplTraitContext::disallowed())
1792 let output = if let Some(ret_id) = make_ret_async {
1793 self.lower_async_fn_ret_ty(
1795 in_band_ty_params.expect("`make_ret_async` but no `fn_def_id`").0,
1800 FnRetTy::Ty(ref ty) => {
1801 let context = match in_band_ty_params {
1802 Some((def_id, _)) if impl_trait_return_allow => {
1803 ImplTraitContext::ReturnPositionOpaqueTy {
1805 origin: hir::OpaqueTyOrigin::FnReturn,
1808 _ => ImplTraitContext::disallowed(),
1810 hir::FnRetTy::Return(self.lower_ty(ty, context))
1812 FnRetTy::Default(span) => hir::FnRetTy::DefaultReturn(span),
1816 self.arena.alloc(hir::FnDecl {
1820 implicit_self: decl.inputs.get(0).map_or(hir::ImplicitSelfKind::None, |arg| {
1821 let is_mutable_pat = match arg.pat.kind {
1822 PatKind::Ident(BindingMode::ByValue(mt) | BindingMode::ByRef(mt), _, _) => {
1823 mt == Mutability::Mut
1829 TyKind::ImplicitSelf if is_mutable_pat => hir::ImplicitSelfKind::Mut,
1830 TyKind::ImplicitSelf => hir::ImplicitSelfKind::Imm,
1831 // Given we are only considering `ImplicitSelf` types, we needn't consider
1832 // the case where we have a mutable pattern to a reference as that would
1833 // no longer be an `ImplicitSelf`.
1834 TyKind::Rptr(_, ref mt)
1835 if mt.ty.kind.is_implicit_self() && mt.mutbl == ast::Mutability::Mut =>
1837 hir::ImplicitSelfKind::MutRef
1839 TyKind::Rptr(_, ref mt) if mt.ty.kind.is_implicit_self() => {
1840 hir::ImplicitSelfKind::ImmRef
1842 _ => hir::ImplicitSelfKind::None,
1848 // Transforms `-> T` for `async fn` into `-> OpaqueTy { .. }`
1849 // combined with the following definition of `OpaqueTy`:
1851 // type OpaqueTy<generics_from_parent_fn> = impl Future<Output = T>;
1853 // `inputs`: lowered types of parameters to the function (used to collect lifetimes)
1854 // `output`: unlowered output type (`T` in `-> T`)
1855 // `fn_def_id`: `DefId` of the parent function (used to create child impl trait definition)
1856 // `opaque_ty_node_id`: `NodeId` of the opaque `impl Trait` type that should be created
1857 // `elided_lt_replacement`: replacement for elided lifetimes in the return type
1858 fn lower_async_fn_ret_ty(
1862 opaque_ty_node_id: NodeId,
1863 ) -> hir::FnRetTy<'hir> {
1865 "lower_async_fn_ret_ty(\
1868 opaque_ty_node_id={:?})",
1869 output, fn_def_id, opaque_ty_node_id,
1872 let span = output.span();
1874 let opaque_ty_span = self.mark_span_with_reason(DesugaringKind::Async, span, None);
1876 let opaque_ty_def_id = self.resolver.local_def_id(opaque_ty_node_id);
1878 self.allocate_hir_id_counter(opaque_ty_node_id);
1880 // When we create the opaque type for this async fn, it is going to have
1881 // to capture all the lifetimes involved in the signature (including in the
1882 // return type). This is done by introducing lifetime parameters for:
1884 // - all the explicitly declared lifetimes from the impl and function itself;
1885 // - all the elided lifetimes in the fn arguments;
1886 // - all the elided lifetimes in the return type.
1888 // So for example in this snippet:
1891 // impl<'a> Foo<'a> {
1892 // async fn bar<'b>(&self, x: &'b Vec<f64>, y: &str) -> &u32 {
1893 // // ^ '0 ^ '1 ^ '2
1894 // // elided lifetimes used below
1899 // we would create an opaque type like:
1902 // type Bar<'a, 'b, '0, '1, '2> = impl Future<Output = &'2 u32>;
1905 // and we would then desugar `bar` to the equivalent of:
1908 // impl<'a> Foo<'a> {
1909 // fn bar<'b, '0, '1>(&'0 self, x: &'b Vec<f64>, y: &'1 str) -> Bar<'a, 'b, '0, '1, '_>
1913 // Note that the final parameter to `Bar` is `'_`, not `'2` --
1914 // this is because the elided lifetimes from the return type
1915 // should be figured out using the ordinary elision rules, and
1916 // this desugaring achieves that.
1918 // The variable `input_lifetimes_count` tracks the number of
1919 // lifetime parameters to the opaque type *not counting* those
1920 // lifetimes elided in the return type. This includes those
1921 // that are explicitly declared (`in_scope_lifetimes`) and
1922 // those elided lifetimes we found in the arguments (current
1923 // content of `lifetimes_to_define`). Next, we will process
1924 // the return type, which will cause `lifetimes_to_define` to
1926 let input_lifetimes_count = self.in_scope_lifetimes.len() + self.lifetimes_to_define.len();
1928 let (opaque_ty_id, lifetime_params) = self.with_hir_id_owner(opaque_ty_node_id, |this| {
1929 // We have to be careful to get elision right here. The
1930 // idea is that we create a lifetime parameter for each
1931 // lifetime in the return type. So, given a return type
1932 // like `async fn foo(..) -> &[&u32]`, we lower to `impl
1933 // Future<Output = &'1 [ &'2 u32 ]>`.
1935 // Then, we will create `fn foo(..) -> Foo<'_, '_>`, and
1936 // hence the elision takes place at the fn site.
1937 let future_bound = this
1938 .with_anonymous_lifetime_mode(AnonymousLifetimeMode::CreateParameter, |this| {
1939 this.lower_async_fn_output_type_to_future_bound(output, fn_def_id, span)
1942 debug!("lower_async_fn_ret_ty: future_bound={:#?}", future_bound);
1944 // Calculate all the lifetimes that should be captured
1945 // by the opaque type. This should include all in-scope
1946 // lifetime parameters, including those defined in-band.
1948 // Note: this must be done after lowering the output type,
1949 // as the output type may introduce new in-band lifetimes.
1950 let lifetime_params: Vec<(Span, ParamName)> = this
1954 .map(|name| (name.ident().span, name))
1955 .chain(this.lifetimes_to_define.iter().cloned())
1958 debug!("lower_async_fn_ret_ty: in_scope_lifetimes={:#?}", this.in_scope_lifetimes);
1959 debug!("lower_async_fn_ret_ty: lifetimes_to_define={:#?}", this.lifetimes_to_define);
1960 debug!("lower_async_fn_ret_ty: lifetime_params={:#?}", lifetime_params);
1962 let generic_params =
1963 this.arena.alloc_from_iter(lifetime_params.iter().map(|(span, hir_name)| {
1964 this.lifetime_to_generic_param(*span, *hir_name, opaque_ty_def_id)
1967 let opaque_ty_item = hir::OpaqueTy {
1968 generics: hir::Generics {
1969 params: generic_params,
1970 where_clause: hir::WhereClause { predicates: &[], span },
1973 bounds: arena_vec![this; future_bound],
1974 impl_trait_fn: Some(fn_def_id),
1975 origin: hir::OpaqueTyOrigin::AsyncFn,
1978 trace!("exist ty from async fn def id: {:#?}", opaque_ty_def_id);
1980 this.generate_opaque_type(opaque_ty_node_id, opaque_ty_item, span, opaque_ty_span);
1982 (opaque_ty_id, lifetime_params)
1985 // As documented above on the variable
1986 // `input_lifetimes_count`, we need to create the lifetime
1987 // arguments to our opaque type. Continuing with our example,
1988 // we're creating the type arguments for the return type:
1991 // Bar<'a, 'b, '0, '1, '_>
1994 // For the "input" lifetime parameters, we wish to create
1995 // references to the parameters themselves, including the
1996 // "implicit" ones created from parameter types (`'a`, `'b`,
1999 // For the "output" lifetime parameters, we just want to
2001 let mut generic_args: Vec<_> = lifetime_params[..input_lifetimes_count]
2003 .map(|&(span, hir_name)| {
2004 // Input lifetime like `'a` or `'1`:
2005 GenericArg::Lifetime(hir::Lifetime {
2006 hir_id: self.next_id(),
2008 name: hir::LifetimeName::Param(hir_name),
2012 generic_args.extend(lifetime_params[input_lifetimes_count..].iter().map(|&(span, _)|
2013 // Output lifetime like `'_`.
2014 GenericArg::Lifetime(hir::Lifetime {
2015 hir_id: self.next_id(),
2017 name: hir::LifetimeName::Implicit,
2019 let generic_args = self.arena.alloc_from_iter(generic_args);
2021 // Create the `Foo<...>` reference itself. Note that the `type
2022 // Foo = impl Trait` is, internally, created as a child of the
2023 // async fn, so the *type parameters* are inherited. It's
2024 // only the lifetime parameters that we must supply.
2025 let opaque_ty_ref = hir::TyKind::OpaqueDef(hir::ItemId { id: opaque_ty_id }, generic_args);
2026 let opaque_ty = self.ty(opaque_ty_span, opaque_ty_ref);
2027 hir::FnRetTy::Return(self.arena.alloc(opaque_ty))
2030 /// Transforms `-> T` into `Future<Output = T>`
2031 fn lower_async_fn_output_type_to_future_bound(
2036 ) -> hir::GenericBound<'hir> {
2037 // Compute the `T` in `Future<Output = T>` from the return type.
2038 let output_ty = match output {
2039 FnRetTy::Ty(ty) => {
2040 // Not `OpaqueTyOrigin::AsyncFn`: that's only used for the
2041 // `impl Future` opaque type that `async fn` implicitly
2043 let context = ImplTraitContext::ReturnPositionOpaqueTy {
2045 origin: hir::OpaqueTyOrigin::FnReturn,
2047 self.lower_ty(ty, context)
2049 FnRetTy::Default(ret_ty_span) => self.arena.alloc(self.ty_tup(*ret_ty_span, &[])),
2053 let future_args = self.arena.alloc(hir::GenericArgs {
2055 bindings: arena_vec![self; self.output_ty_binding(span, output_ty)],
2056 parenthesized: false,
2059 hir::GenericBound::LangItemTrait(
2060 // ::std::future::Future<future_params>
2061 hir::LangItem::FutureTraitLangItem,
2068 fn lower_param_bound(
2071 itctx: ImplTraitContext<'_, 'hir>,
2072 ) -> hir::GenericBound<'hir> {
2074 GenericBound::Trait(ref ty, modifier) => hir::GenericBound::Trait(
2075 self.lower_poly_trait_ref(ty, itctx),
2076 self.lower_trait_bound_modifier(modifier),
2078 GenericBound::Outlives(ref lifetime) => {
2079 hir::GenericBound::Outlives(self.lower_lifetime(lifetime))
2084 fn lower_lifetime(&mut self, l: &Lifetime) -> hir::Lifetime {
2085 let span = l.ident.span;
2087 ident if ident.name == kw::StaticLifetime => {
2088 self.new_named_lifetime(l.id, span, hir::LifetimeName::Static)
2090 ident if ident.name == kw::UnderscoreLifetime => match self.anonymous_lifetime_mode {
2091 AnonymousLifetimeMode::CreateParameter => {
2092 let fresh_name = self.collect_fresh_in_band_lifetime(span);
2093 self.new_named_lifetime(l.id, span, hir::LifetimeName::Param(fresh_name))
2096 AnonymousLifetimeMode::PassThrough => {
2097 self.new_named_lifetime(l.id, span, hir::LifetimeName::Underscore)
2100 AnonymousLifetimeMode::ReportError => self.new_error_lifetime(Some(l.id), span),
2103 self.maybe_collect_in_band_lifetime(ident);
2104 let param_name = ParamName::Plain(ident);
2105 self.new_named_lifetime(l.id, span, hir::LifetimeName::Param(param_name))
2110 fn new_named_lifetime(
2114 name: hir::LifetimeName,
2115 ) -> hir::Lifetime {
2116 hir::Lifetime { hir_id: self.lower_node_id(id), span, name }
2119 fn lower_generic_params_mut<'s>(
2121 params: &'s [GenericParam],
2122 add_bounds: &'s NodeMap<Vec<GenericBound>>,
2123 mut itctx: ImplTraitContext<'s, 'hir>,
2124 ) -> impl Iterator<Item = hir::GenericParam<'hir>> + Captures<'a> + Captures<'s> {
2127 .map(move |param| self.lower_generic_param(param, add_bounds, itctx.reborrow()))
2130 fn lower_generic_params(
2132 params: &[GenericParam],
2133 add_bounds: &NodeMap<Vec<GenericBound>>,
2134 itctx: ImplTraitContext<'_, 'hir>,
2135 ) -> &'hir [hir::GenericParam<'hir>] {
2136 self.arena.alloc_from_iter(self.lower_generic_params_mut(params, add_bounds, itctx))
2139 fn lower_generic_param(
2141 param: &GenericParam,
2142 add_bounds: &NodeMap<Vec<GenericBound>>,
2143 mut itctx: ImplTraitContext<'_, 'hir>,
2144 ) -> hir::GenericParam<'hir> {
2145 let mut bounds: Vec<_> = self
2146 .with_anonymous_lifetime_mode(AnonymousLifetimeMode::ReportError, |this| {
2147 this.lower_param_bounds_mut(¶m.bounds, itctx.reborrow()).collect()
2150 let (name, kind) = match param.kind {
2151 GenericParamKind::Lifetime => {
2152 let was_collecting_in_band = self.is_collecting_in_band_lifetimes;
2153 self.is_collecting_in_band_lifetimes = false;
2156 .with_anonymous_lifetime_mode(AnonymousLifetimeMode::ReportError, |this| {
2157 this.lower_lifetime(&Lifetime { id: param.id, ident: param.ident })
2159 let param_name = match lt.name {
2160 hir::LifetimeName::Param(param_name) => param_name,
2161 hir::LifetimeName::Implicit
2162 | hir::LifetimeName::Underscore
2163 | hir::LifetimeName::Static => hir::ParamName::Plain(lt.name.ident()),
2164 hir::LifetimeName::ImplicitObjectLifetimeDefault => {
2165 self.sess.diagnostic().span_bug(
2167 "object-lifetime-default should not occur here",
2170 hir::LifetimeName::Error => ParamName::Error,
2174 hir::GenericParamKind::Lifetime { kind: hir::LifetimeParamKind::Explicit };
2176 self.is_collecting_in_band_lifetimes = was_collecting_in_band;
2180 GenericParamKind::Type { ref default, .. } => {
2181 let add_bounds = add_bounds.get(¶m.id).map_or(&[][..], |x| &x);
2182 if !add_bounds.is_empty() {
2183 let params = self.lower_param_bounds_mut(add_bounds, itctx.reborrow());
2184 bounds.extend(params);
2187 let kind = hir::GenericParamKind::Type {
2188 default: default.as_ref().map(|x| {
2191 ImplTraitContext::OtherOpaqueTy {
2192 capturable_lifetimes: &mut FxHashSet::default(),
2193 origin: hir::OpaqueTyOrigin::Misc,
2200 .filter(|attr| self.sess.check_name(attr, sym::rustc_synthetic))
2201 .map(|_| hir::SyntheticTyParamKind::ImplTrait)
2205 (hir::ParamName::Plain(param.ident), kind)
2207 GenericParamKind::Const { ref ty, kw_span: _ } => {
2209 .with_anonymous_lifetime_mode(AnonymousLifetimeMode::ReportError, |this| {
2210 this.lower_ty(&ty, ImplTraitContext::disallowed())
2213 (hir::ParamName::Plain(param.ident), hir::GenericParamKind::Const { ty })
2218 hir_id: self.lower_node_id(param.id),
2220 span: param.ident.span,
2221 pure_wrt_drop: self.sess.contains_name(¶m.attrs, sym::may_dangle),
2222 attrs: self.lower_attrs(¶m.attrs),
2223 bounds: self.arena.alloc_from_iter(bounds),
2231 itctx: ImplTraitContext<'_, 'hir>,
2232 ) -> hir::TraitRef<'hir> {
2233 let path = match self.lower_qpath(p.ref_id, &None, &p.path, ParamMode::Explicit, itctx) {
2234 hir::QPath::Resolved(None, path) => path,
2235 qpath => panic!("lower_trait_ref: unexpected QPath `{:?}`", qpath),
2237 hir::TraitRef { path, hir_ref_id: self.lower_node_id(p.ref_id) }
2240 fn lower_poly_trait_ref(
2243 mut itctx: ImplTraitContext<'_, 'hir>,
2244 ) -> hir::PolyTraitRef<'hir> {
2245 let bound_generic_params = self.lower_generic_params(
2246 &p.bound_generic_params,
2247 &NodeMap::default(),
2251 let trait_ref = self.with_in_scope_lifetime_defs(&p.bound_generic_params, |this| {
2252 // Any impl Trait types defined within this scope can capture
2253 // lifetimes bound on this predicate.
2254 let lt_def_names = p.bound_generic_params.iter().filter_map(|param| match param.kind {
2255 GenericParamKind::Lifetime { .. } => Some(hir::LifetimeName::Param(
2256 ParamName::Plain(param.ident.normalize_to_macros_2_0()),
2260 if let ImplTraitContext::OtherOpaqueTy { ref mut capturable_lifetimes, .. } = itctx {
2261 capturable_lifetimes.extend(lt_def_names.clone());
2264 let res = this.lower_trait_ref(&p.trait_ref, itctx.reborrow());
2266 if let ImplTraitContext::OtherOpaqueTy { ref mut capturable_lifetimes, .. } = itctx {
2267 for param in lt_def_names {
2268 capturable_lifetimes.remove(¶m);
2274 hir::PolyTraitRef { bound_generic_params, trait_ref, span: p.span }
2277 fn lower_mt(&mut self, mt: &MutTy, itctx: ImplTraitContext<'_, 'hir>) -> hir::MutTy<'hir> {
2278 hir::MutTy { ty: self.lower_ty(&mt.ty, itctx), mutbl: mt.mutbl }
2281 fn lower_param_bounds(
2283 bounds: &[GenericBound],
2284 itctx: ImplTraitContext<'_, 'hir>,
2285 ) -> hir::GenericBounds<'hir> {
2286 self.arena.alloc_from_iter(self.lower_param_bounds_mut(bounds, itctx))
2289 fn lower_param_bounds_mut<'s>(
2291 bounds: &'s [GenericBound],
2292 mut itctx: ImplTraitContext<'s, 'hir>,
2293 ) -> impl Iterator<Item = hir::GenericBound<'hir>> + Captures<'s> + Captures<'a> {
2294 bounds.iter().map(move |bound| self.lower_param_bound(bound, itctx.reborrow()))
2297 fn lower_block(&mut self, b: &Block, targeted_by_break: bool) -> &'hir hir::Block<'hir> {
2298 self.arena.alloc(self.lower_block_noalloc(b, targeted_by_break))
2301 fn lower_block_noalloc(&mut self, b: &Block, targeted_by_break: bool) -> hir::Block<'hir> {
2302 let mut stmts = vec![];
2303 let mut expr: Option<&'hir _> = None;
2305 for (index, stmt) in b.stmts.iter().enumerate() {
2306 if index == b.stmts.len() - 1 {
2307 if let StmtKind::Expr(ref e) = stmt.kind {
2308 expr = Some(self.lower_expr(e));
2310 stmts.extend(self.lower_stmt(stmt));
2313 stmts.extend(self.lower_stmt(stmt));
2318 hir_id: self.lower_node_id(b.id),
2319 stmts: self.arena.alloc_from_iter(stmts),
2321 rules: self.lower_block_check_mode(&b.rules),
2327 /// Lowers a block directly to an expression, presuming that it
2328 /// has no attributes and is not targeted by a `break`.
2329 fn lower_block_expr(&mut self, b: &Block) -> hir::Expr<'hir> {
2330 let block = self.lower_block(b, false);
2331 self.expr_block(block, AttrVec::new())
2334 fn lower_anon_const(&mut self, c: &AnonConst) -> hir::AnonConst {
2335 self.with_new_scopes(|this| hir::AnonConst {
2336 hir_id: this.lower_node_id(c.id),
2337 body: this.lower_const_body(c.value.span, Some(&c.value)),
2341 fn lower_stmt(&mut self, s: &Stmt) -> SmallVec<[hir::Stmt<'hir>; 1]> {
2342 let kind = match s.kind {
2343 StmtKind::Local(ref l) => {
2344 let (l, item_ids) = self.lower_local(l);
2345 let mut ids: SmallVec<[hir::Stmt<'hir>; 1]> = item_ids
2348 let item_id = hir::ItemId { id: self.lower_node_id(item_id) };
2349 self.stmt(s.span, hir::StmtKind::Item(item_id))
2354 hir_id: self.lower_node_id(s.id),
2355 kind: hir::StmtKind::Local(self.arena.alloc(l)),
2361 StmtKind::Item(ref it) => {
2362 // Can only use the ID once.
2363 let mut id = Some(s.id);
2370 .map(|id| self.lower_node_id(id))
2371 .unwrap_or_else(|| self.next_id());
2373 hir::Stmt { hir_id, kind: hir::StmtKind::Item(item_id), span: s.span }
2377 StmtKind::Expr(ref e) => hir::StmtKind::Expr(self.lower_expr(e)),
2378 StmtKind::Semi(ref e) => hir::StmtKind::Semi(self.lower_expr(e)),
2379 StmtKind::Empty => return smallvec![],
2380 StmtKind::MacCall(..) => panic!("shouldn't exist here"),
2382 smallvec![hir::Stmt { hir_id: self.lower_node_id(s.id), kind, span: s.span }]
2385 fn lower_block_check_mode(&mut self, b: &BlockCheckMode) -> hir::BlockCheckMode {
2387 BlockCheckMode::Default => hir::BlockCheckMode::DefaultBlock,
2388 BlockCheckMode::Unsafe(u) => {
2389 hir::BlockCheckMode::UnsafeBlock(self.lower_unsafe_source(u))
2394 fn lower_unsafe_source(&mut self, u: UnsafeSource) -> hir::UnsafeSource {
2396 CompilerGenerated => hir::UnsafeSource::CompilerGenerated,
2397 UserProvided => hir::UnsafeSource::UserProvided,
2401 fn lower_trait_bound_modifier(&mut self, f: TraitBoundModifier) -> hir::TraitBoundModifier {
2403 TraitBoundModifier::None => hir::TraitBoundModifier::None,
2404 TraitBoundModifier::MaybeConst => hir::TraitBoundModifier::MaybeConst,
2406 // `MaybeConstMaybe` will cause an error during AST validation, but we need to pick a
2407 // placeholder for compilation to proceed.
2408 TraitBoundModifier::MaybeConstMaybe | TraitBoundModifier::Maybe => {
2409 hir::TraitBoundModifier::Maybe
2414 // Helper methods for building HIR.
2416 fn stmt(&mut self, span: Span, kind: hir::StmtKind<'hir>) -> hir::Stmt<'hir> {
2417 hir::Stmt { span, kind, hir_id: self.next_id() }
2420 fn stmt_expr(&mut self, span: Span, expr: hir::Expr<'hir>) -> hir::Stmt<'hir> {
2421 self.stmt(span, hir::StmtKind::Expr(self.arena.alloc(expr)))
2428 init: Option<&'hir hir::Expr<'hir>>,
2429 pat: &'hir hir::Pat<'hir>,
2430 source: hir::LocalSource,
2431 ) -> hir::Stmt<'hir> {
2432 let local = hir::Local { attrs, hir_id: self.next_id(), init, pat, source, span, ty: None };
2433 self.stmt(span, hir::StmtKind::Local(self.arena.alloc(local)))
2436 fn block_expr(&mut self, expr: &'hir hir::Expr<'hir>) -> &'hir hir::Block<'hir> {
2437 self.block_all(expr.span, &[], Some(expr))
2443 stmts: &'hir [hir::Stmt<'hir>],
2444 expr: Option<&'hir hir::Expr<'hir>>,
2445 ) -> &'hir hir::Block<'hir> {
2446 let blk = hir::Block {
2449 hir_id: self.next_id(),
2450 rules: hir::BlockCheckMode::DefaultBlock,
2452 targeted_by_break: false,
2454 self.arena.alloc(blk)
2457 /// Constructs a `true` or `false` literal pattern.
2458 fn pat_bool(&mut self, span: Span, val: bool) -> &'hir hir::Pat<'hir> {
2459 let expr = self.expr_bool(span, val);
2460 self.pat(span, hir::PatKind::Lit(expr))
2463 fn pat_ok(&mut self, span: Span, pat: &'hir hir::Pat<'hir>) -> &'hir hir::Pat<'hir> {
2464 let field = self.single_pat_field(span, pat);
2465 self.pat_lang_item_variant(span, hir::LangItem::ResultOk, field)
2468 fn pat_err(&mut self, span: Span, pat: &'hir hir::Pat<'hir>) -> &'hir hir::Pat<'hir> {
2469 let field = self.single_pat_field(span, pat);
2470 self.pat_lang_item_variant(span, hir::LangItem::ResultErr, field)
2473 fn pat_some(&mut self, span: Span, pat: &'hir hir::Pat<'hir>) -> &'hir hir::Pat<'hir> {
2474 let field = self.single_pat_field(span, pat);
2475 self.pat_lang_item_variant(span, hir::LangItem::OptionSome, field)
2478 fn pat_none(&mut self, span: Span) -> &'hir hir::Pat<'hir> {
2479 self.pat_lang_item_variant(span, hir::LangItem::OptionNone, &[])
2482 fn single_pat_field(
2485 pat: &'hir hir::Pat<'hir>,
2486 ) -> &'hir [hir::FieldPat<'hir>] {
2487 let field = hir::FieldPat {
2488 hir_id: self.next_id(),
2489 ident: Ident::new(sym::integer(0), span),
2490 is_shorthand: false,
2494 arena_vec![self; field]
2497 fn pat_lang_item_variant(
2500 lang_item: hir::LangItem,
2501 fields: &'hir [hir::FieldPat<'hir>],
2502 ) -> &'hir hir::Pat<'hir> {
2503 let qpath = hir::QPath::LangItem(lang_item, span);
2504 self.pat(span, hir::PatKind::Struct(qpath, fields, false))
2507 fn pat_ident(&mut self, span: Span, ident: Ident) -> (&'hir hir::Pat<'hir>, hir::HirId) {
2508 self.pat_ident_binding_mode(span, ident, hir::BindingAnnotation::Unannotated)
2511 fn pat_ident_binding_mode(
2515 bm: hir::BindingAnnotation,
2516 ) -> (&'hir hir::Pat<'hir>, hir::HirId) {
2517 let hir_id = self.next_id();
2520 self.arena.alloc(hir::Pat {
2522 kind: hir::PatKind::Binding(bm, hir_id, ident.with_span_pos(span), None),
2529 fn pat_wild(&mut self, span: Span) -> &'hir hir::Pat<'hir> {
2530 self.pat(span, hir::PatKind::Wild)
2533 fn pat(&mut self, span: Span, kind: hir::PatKind<'hir>) -> &'hir hir::Pat<'hir> {
2534 self.arena.alloc(hir::Pat { hir_id: self.next_id(), kind, span })
2539 mut hir_id: hir::HirId,
2541 qpath: hir::QPath<'hir>,
2542 ) -> hir::Ty<'hir> {
2543 let kind = match qpath {
2544 hir::QPath::Resolved(None, path) => {
2545 // Turn trait object paths into `TyKind::TraitObject` instead.
2547 Res::Def(DefKind::Trait | DefKind::TraitAlias, _) => {
2548 let principal = hir::PolyTraitRef {
2549 bound_generic_params: &[],
2550 trait_ref: hir::TraitRef { path, hir_ref_id: hir_id },
2554 // The original ID is taken by the `PolyTraitRef`,
2555 // so the `Ty` itself needs a different one.
2556 hir_id = self.next_id();
2557 hir::TyKind::TraitObject(
2558 arena_vec![self; principal],
2559 self.elided_dyn_bound(span),
2562 _ => hir::TyKind::Path(hir::QPath::Resolved(None, path)),
2565 _ => hir::TyKind::Path(qpath),
2568 hir::Ty { hir_id, kind, span }
2571 /// Invoked to create the lifetime argument for a type `&T`
2572 /// with no explicit lifetime.
2573 fn elided_ref_lifetime(&mut self, span: Span) -> hir::Lifetime {
2574 match self.anonymous_lifetime_mode {
2575 // Intercept when we are in an impl header or async fn and introduce an in-band
2577 // Hence `impl Foo for &u32` becomes `impl<'f> Foo for &'f u32` for some fresh
2579 AnonymousLifetimeMode::CreateParameter => {
2580 let fresh_name = self.collect_fresh_in_band_lifetime(span);
2582 hir_id: self.next_id(),
2584 name: hir::LifetimeName::Param(fresh_name),
2588 AnonymousLifetimeMode::ReportError => self.new_error_lifetime(None, span),
2590 AnonymousLifetimeMode::PassThrough => self.new_implicit_lifetime(span),
2594 /// Report an error on illegal use of `'_` or a `&T` with no explicit lifetime;
2595 /// return a "error lifetime".
2596 fn new_error_lifetime(&mut self, id: Option<NodeId>, span: Span) -> hir::Lifetime {
2597 let (id, msg, label) = match id {
2598 Some(id) => (id, "`'_` cannot be used here", "`'_` is a reserved lifetime name"),
2601 self.resolver.next_node_id(),
2602 "`&` without an explicit lifetime name cannot be used here",
2603 "explicit lifetime name needed here",
2607 let mut err = struct_span_err!(self.sess, span, E0637, "{}", msg,);
2608 err.span_label(span, label);
2611 self.new_named_lifetime(id, span, hir::LifetimeName::Error)
2614 /// Invoked to create the lifetime argument(s) for a path like
2615 /// `std::cell::Ref<T>`; note that implicit lifetimes in these
2616 /// sorts of cases are deprecated. This may therefore report a warning or an
2617 /// error, depending on the mode.
2618 fn elided_path_lifetimes<'s>(
2622 ) -> impl Iterator<Item = hir::Lifetime> + Captures<'a> + Captures<'s> + Captures<'hir> {
2623 (0..count).map(move |_| self.elided_path_lifetime(span))
2626 fn elided_path_lifetime(&mut self, span: Span) -> hir::Lifetime {
2627 match self.anonymous_lifetime_mode {
2628 AnonymousLifetimeMode::CreateParameter => {
2629 // We should have emitted E0726 when processing this path above
2631 .delay_span_bug(span, "expected 'implicit elided lifetime not allowed' error");
2632 let id = self.resolver.next_node_id();
2633 self.new_named_lifetime(id, span, hir::LifetimeName::Error)
2635 // `PassThrough` is the normal case.
2636 // `new_error_lifetime`, which would usually be used in the case of `ReportError`,
2637 // is unsuitable here, as these can occur from missing lifetime parameters in a
2638 // `PathSegment`, for which there is no associated `'_` or `&T` with no explicit
2639 // lifetime. Instead, we simply create an implicit lifetime, which will be checked
2640 // later, at which point a suitable error will be emitted.
2641 AnonymousLifetimeMode::PassThrough | AnonymousLifetimeMode::ReportError => {
2642 self.new_implicit_lifetime(span)
2647 /// Invoked to create the lifetime argument(s) for an elided trait object
2648 /// bound, like the bound in `Box<dyn Debug>`. This method is not invoked
2649 /// when the bound is written, even if it is written with `'_` like in
2650 /// `Box<dyn Debug + '_>`. In those cases, `lower_lifetime` is invoked.
2651 fn elided_dyn_bound(&mut self, span: Span) -> hir::Lifetime {
2652 match self.anonymous_lifetime_mode {
2653 // NB. We intentionally ignore the create-parameter mode here.
2654 // and instead "pass through" to resolve-lifetimes, which will apply
2655 // the object-lifetime-defaulting rules. Elided object lifetime defaults
2656 // do not act like other elided lifetimes. In other words, given this:
2658 // impl Foo for Box<dyn Debug>
2660 // we do not introduce a fresh `'_` to serve as the bound, but instead
2661 // ultimately translate to the equivalent of:
2663 // impl Foo for Box<dyn Debug + 'static>
2665 // `resolve_lifetime` has the code to make that happen.
2666 AnonymousLifetimeMode::CreateParameter => {}
2668 AnonymousLifetimeMode::ReportError => {
2669 // ReportError applies to explicit use of `'_`.
2672 // This is the normal case.
2673 AnonymousLifetimeMode::PassThrough => {}
2676 let r = hir::Lifetime {
2677 hir_id: self.next_id(),
2679 name: hir::LifetimeName::ImplicitObjectLifetimeDefault,
2681 debug!("elided_dyn_bound: r={:?}", r);
2685 fn new_implicit_lifetime(&mut self, span: Span) -> hir::Lifetime {
2686 hir::Lifetime { hir_id: self.next_id(), span, name: hir::LifetimeName::Implicit }
2689 fn maybe_lint_bare_trait(&mut self, span: Span, id: NodeId, is_global: bool) {
2690 // FIXME(davidtwco): This is a hack to detect macros which produce spans of the
2691 // call site which do not have a macro backtrace. See #61963.
2692 let is_macro_callsite = self
2695 .span_to_snippet(span)
2696 .map(|snippet| snippet.starts_with("#["))
2698 if !is_macro_callsite {
2699 self.resolver.lint_buffer().buffer_lint_with_diagnostic(
2703 "trait objects without an explicit `dyn` are deprecated",
2704 BuiltinLintDiagnostics::BareTraitObject(span, is_global),
2710 fn body_ids(bodies: &BTreeMap<hir::BodyId, hir::Body<'_>>) -> Vec<hir::BodyId> {
2711 // Sorting by span ensures that we get things in order within a
2712 // file, and also puts the files in a sensible order.
2713 let mut body_ids: Vec<_> = bodies.keys().cloned().collect();
2714 body_ids.sort_by_key(|b| bodies[b].value.span);
2718 /// Helper struct for delayed construction of GenericArgs.
2719 struct GenericArgsCtor<'hir> {
2720 args: SmallVec<[hir::GenericArg<'hir>; 4]>,
2721 bindings: &'hir [hir::TypeBinding<'hir>],
2722 parenthesized: bool,
2725 impl<'hir> GenericArgsCtor<'hir> {
2726 fn is_empty(&self) -> bool {
2727 self.args.is_empty() && self.bindings.is_empty() && !self.parenthesized
2730 fn into_generic_args(self, arena: &'hir Arena<'hir>) -> hir::GenericArgs<'hir> {
2732 args: arena.alloc_from_iter(self.args),
2733 bindings: self.bindings,
2734 parenthesized: self.parenthesized,