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), 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(crate_visibility_modifier)]
34 #![feature(box_patterns)]
36 #![recursion_limit = "256"]
38 use rustc_ast::node_id::NodeMap;
39 use rustc_ast::token::{self, Token};
40 use rustc_ast::tokenstream::{CanSynthesizeMissingTokens, 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::{FxHashMap, FxHashSet};
47 use rustc_data_structures::sync::Lrc;
48 use rustc_errors::{struct_span_err, Applicability};
50 use rustc_hir::def::{DefKind, Namespace, PartialRes, PerNS, Res};
51 use rustc_hir::def_id::{DefId, DefIdMap, DefPathHash, LocalDefId, CRATE_DEF_ID};
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::lint::builtin::{BARE_TRAIT_OBJECTS, MISSING_ABI};
57 use rustc_session::lint::{BuiltinLintDiagnostics, LintBuffer};
58 use rustc_session::utils::{FlattenNonterminals, NtToTokenstream};
59 use rustc_session::Session;
60 use rustc_span::edition::Edition;
61 use rustc_span::hygiene::ExpnId;
62 use rustc_span::source_map::{respan, CachingSourceMapView, DesugaringKind};
63 use rustc_span::symbol::{kw, sym, Ident, Symbol};
64 use rustc_span::{Span, DUMMY_SP};
65 use rustc_target::spec::abi::Abi;
67 use smallvec::{smallvec, SmallVec};
68 use std::collections::BTreeMap;
70 use tracing::{debug, trace};
72 macro_rules! arena_vec {
73 ($this:expr; $($x:expr),*) => ({
75 $this.arena.alloc_from_iter(std::array::IntoIter::new(a))
85 const HIR_ID_COUNTER_LOCKED: u32 = 0xFFFFFFFF;
87 rustc_hir::arena_types!(rustc_arena::declare_arena, [], 'tcx);
89 struct LoweringContext<'a, 'hir: 'a> {
90 /// Used to assign IDs to HIR nodes that do not directly correspond to AST nodes.
93 resolver: &'a mut dyn ResolverAstLowering,
95 /// HACK(Centril): there is a cyclic dependency between the parser and lowering
96 /// if we don't have this function pointer. To avoid that dependency so that
97 /// `rustc_middle` is independent of the parser, we use dynamic dispatch here.
98 nt_to_tokenstream: NtToTokenstream,
100 /// Used to allocate HIR nodes.
101 arena: &'hir Arena<'hir>,
103 /// The items being lowered are collected here.
104 items: BTreeMap<hir::ItemId, hir::Item<'hir>>,
106 trait_items: BTreeMap<hir::TraitItemId, hir::TraitItem<'hir>>,
107 impl_items: BTreeMap<hir::ImplItemId, hir::ImplItem<'hir>>,
108 foreign_items: BTreeMap<hir::ForeignItemId, hir::ForeignItem<'hir>>,
109 bodies: BTreeMap<hir::BodyId, hir::Body<'hir>>,
110 exported_macros: Vec<hir::MacroDef<'hir>>,
111 non_exported_macro_attrs: Vec<ast::Attribute>,
113 trait_impls: BTreeMap<DefId, Vec<LocalDefId>>,
115 modules: BTreeMap<LocalDefId, hir::ModuleItems>,
117 generator_kind: Option<hir::GeneratorKind>,
119 attrs: BTreeMap<hir::HirId, &'hir [Attribute]>,
121 /// When inside an `async` context, this is the `HirId` of the
122 /// `task_context` local bound to the resume argument of the generator.
123 task_context: Option<hir::HirId>,
125 /// Used to get the current `fn`'s def span to point to when using `await`
126 /// outside of an `async fn`.
127 current_item: Option<Span>,
129 catch_scopes: Vec<NodeId>,
130 loop_scopes: Vec<NodeId>,
131 is_in_loop_condition: bool,
132 is_in_trait_impl: bool,
133 is_in_dyn_type: bool,
135 /// What to do when we encounter an "anonymous lifetime
136 /// reference". The term "anonymous" is meant to encompass both
137 /// `'_` lifetimes as well as fully elided cases where nothing is
138 /// written at all (e.g., `&T` or `std::cell::Ref<T>`).
139 anonymous_lifetime_mode: AnonymousLifetimeMode,
141 /// Used to create lifetime definitions from in-band lifetime usages.
142 /// e.g., `fn foo(x: &'x u8) -> &'x u8` to `fn foo<'x>(x: &'x u8) -> &'x u8`
143 /// When a named lifetime is encountered in a function or impl header and
144 /// has not been defined
145 /// (i.e., it doesn't appear in the in_scope_lifetimes list), it is added
146 /// to this list. The results of this list are then added to the list of
147 /// lifetime definitions in the corresponding impl or function generics.
148 lifetimes_to_define: Vec<(Span, ParamName)>,
150 /// `true` if in-band lifetimes are being collected. This is used to
151 /// indicate whether or not we're in a place where new lifetimes will result
152 /// in in-band lifetime definitions, such a function or an impl header,
153 /// including implicit lifetimes from `impl_header_lifetime_elision`.
154 is_collecting_in_band_lifetimes: bool,
156 /// Currently in-scope lifetimes defined in impl headers, fn headers, or HRTB.
157 /// When `is_collecting_in_band_lifetimes` is true, each lifetime is checked
158 /// against this list to see if it is already in-scope, or if a definition
159 /// needs to be created for it.
161 /// We always store a `normalize_to_macros_2_0()` version of the param-name in this
163 in_scope_lifetimes: Vec<ParamName>,
165 current_module: LocalDefId,
167 type_def_lifetime_params: DefIdMap<usize>,
169 current_hir_id_owner: (LocalDefId, u32),
170 item_local_id_counters: NodeMap<u32>,
171 node_id_to_hir_id: IndexVec<NodeId, Option<hir::HirId>>,
173 allow_try_trait: Option<Lrc<[Symbol]>>,
174 allow_gen_future: Option<Lrc<[Symbol]>>,
177 pub trait ResolverAstLowering {
178 fn def_key(&mut self, id: DefId) -> DefKey;
180 fn item_generics_num_lifetimes(&self, def: DefId, sess: &Session) -> usize;
182 fn legacy_const_generic_args(&mut self, expr: &Expr) -> Option<Vec<usize>>;
184 /// Obtains resolution for a `NodeId` with a single resolution.
185 fn get_partial_res(&mut self, id: NodeId) -> Option<PartialRes>;
187 /// Obtains per-namespace resolutions for `use` statement with the given `NodeId`.
188 fn get_import_res(&mut self, id: NodeId) -> PerNS<Option<Res<NodeId>>>;
190 /// Obtains resolution for a label with the given `NodeId`.
191 fn get_label_res(&mut self, id: NodeId) -> Option<NodeId>;
193 /// We must keep the set of definitions up to date as we add nodes that weren't in the AST.
194 /// This should only return `None` during testing.
195 fn definitions(&mut self) -> &mut Definitions;
197 fn lint_buffer(&mut self) -> &mut LintBuffer;
199 fn next_node_id(&mut self) -> NodeId;
201 fn take_trait_map(&mut self) -> NodeMap<Vec<hir::TraitCandidate>>;
203 fn opt_local_def_id(&self, node: NodeId) -> Option<LocalDefId>;
205 fn local_def_id(&self, node: NodeId) -> LocalDefId;
207 fn def_path_hash(&self, def_id: DefId) -> DefPathHash;
212 node_id: ast::NodeId,
219 struct LoweringHasher<'a> {
220 source_map: CachingSourceMapView<'a>,
221 resolver: &'a dyn ResolverAstLowering,
224 impl<'a> rustc_span::HashStableContext for LoweringHasher<'a> {
226 fn hash_spans(&self) -> bool {
231 fn def_path_hash(&self, def_id: DefId) -> DefPathHash {
232 self.resolver.def_path_hash(def_id)
236 fn span_data_to_lines_and_cols(
238 span: &rustc_span::SpanData,
239 ) -> Option<(Lrc<rustc_span::SourceFile>, usize, rustc_span::BytePos, usize, rustc_span::BytePos)>
241 self.source_map.span_data_to_lines_and_cols(span)
245 /// Context of `impl Trait` in code, which determines whether it is allowed in an HIR subtree,
246 /// and if so, what meaning it has.
248 enum ImplTraitContext<'b, 'a> {
249 /// Treat `impl Trait` as shorthand for a new universal generic parameter.
250 /// Example: `fn foo(x: impl Debug)`, where `impl Debug` is conceptually
251 /// equivalent to a fresh universal parameter like `fn foo<T: Debug>(x: T)`.
253 /// Newly generated parameters should be inserted into the given `Vec`.
254 Universal(&'b mut Vec<hir::GenericParam<'a>>, LocalDefId),
256 /// Treat `impl Trait` as shorthand for a new opaque type.
257 /// Example: `fn foo() -> impl Debug`, where `impl Debug` is conceptually
258 /// equivalent to a new opaque type like `type T = impl Debug; fn foo() -> T`.
260 ReturnPositionOpaqueTy {
261 /// `DefId` for the parent function, used to look up necessary
262 /// information later.
264 /// Origin: Either OpaqueTyOrigin::FnReturn or OpaqueTyOrigin::AsyncFn,
265 origin: hir::OpaqueTyOrigin,
267 /// Impl trait in type aliases.
268 TypeAliasesOpaqueTy {
269 /// Set of lifetimes that this opaque type can capture, if it uses
270 /// them. This includes lifetimes bound since we entered this context.
274 /// type A<'b> = impl for<'a> Trait<'a, Out = impl Sized + 'a>;
277 /// Here the inner opaque type captures `'a` because it uses it. It doesn't
278 /// need to capture `'b` because it already inherits the lifetime
279 /// parameter from `A`.
280 // FIXME(impl_trait): but `required_region_bounds` will ICE later
282 capturable_lifetimes: &'b mut FxHashSet<hir::LifetimeName>,
284 /// `impl Trait` is not accepted in this position.
285 Disallowed(ImplTraitPosition),
288 /// Position in which `impl Trait` is disallowed.
289 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
290 enum ImplTraitPosition {
291 /// Disallowed in `let` / `const` / `static` bindings.
294 /// All other positions.
298 impl<'a> ImplTraitContext<'_, 'a> {
300 fn disallowed() -> Self {
301 ImplTraitContext::Disallowed(ImplTraitPosition::Other)
304 fn reborrow<'this>(&'this mut self) -> ImplTraitContext<'this, 'a> {
305 use self::ImplTraitContext::*;
307 Universal(params, parent) => Universal(params, *parent),
308 ReturnPositionOpaqueTy { fn_def_id, origin } => {
309 ReturnPositionOpaqueTy { fn_def_id: *fn_def_id, origin: *origin }
311 TypeAliasesOpaqueTy { capturable_lifetimes } => {
312 TypeAliasesOpaqueTy { capturable_lifetimes }
314 Disallowed(pos) => Disallowed(*pos),
319 pub fn lower_crate<'a, 'hir>(
322 resolver: &'a mut dyn ResolverAstLowering,
323 nt_to_tokenstream: NtToTokenstream,
324 arena: &'hir Arena<'hir>,
325 ) -> &'hir hir::Crate<'hir> {
326 let _prof_timer = sess.prof.verbose_generic_activity("hir_lowering");
333 items: BTreeMap::new(),
334 trait_items: BTreeMap::new(),
335 impl_items: BTreeMap::new(),
336 foreign_items: BTreeMap::new(),
337 bodies: BTreeMap::new(),
338 trait_impls: BTreeMap::new(),
339 modules: BTreeMap::new(),
340 attrs: BTreeMap::default(),
341 exported_macros: Vec::new(),
342 non_exported_macro_attrs: Vec::new(),
343 catch_scopes: Vec::new(),
344 loop_scopes: Vec::new(),
345 is_in_loop_condition: false,
346 is_in_trait_impl: false,
347 is_in_dyn_type: false,
348 anonymous_lifetime_mode: AnonymousLifetimeMode::PassThrough,
349 type_def_lifetime_params: Default::default(),
350 current_module: CRATE_DEF_ID,
351 current_hir_id_owner: (CRATE_DEF_ID, 0),
352 item_local_id_counters: Default::default(),
353 node_id_to_hir_id: IndexVec::new(),
354 generator_kind: None,
357 lifetimes_to_define: Vec::new(),
358 is_collecting_in_band_lifetimes: false,
359 in_scope_lifetimes: Vec::new(),
360 allow_try_trait: Some([sym::try_trait_v2][..].into()),
361 allow_gen_future: Some([sym::gen_future][..].into()),
366 #[derive(Copy, Clone, PartialEq)]
368 /// Any path in a type context.
370 /// Path in a type definition, where the anonymous lifetime `'_` is not allowed.
372 /// The `module::Type` in `module::Type::method` in an expression.
376 enum ParenthesizedGenericArgs {
381 /// What to do when we encounter an **anonymous** lifetime
382 /// reference. Anonymous lifetime references come in two flavors. You
383 /// have implicit, or fully elided, references to lifetimes, like the
384 /// one in `&T` or `Ref<T>`, and you have `'_` lifetimes, like `&'_ T`
385 /// or `Ref<'_, T>`. These often behave the same, but not always:
387 /// - certain usages of implicit references are deprecated, like
388 /// `Ref<T>`, and we sometimes just give hard errors in those cases
390 /// - for object bounds there is a difference: `Box<dyn Foo>` is not
391 /// the same as `Box<dyn Foo + '_>`.
393 /// We describe the effects of the various modes in terms of three cases:
395 /// - **Modern** -- includes all uses of `'_`, but also the lifetime arg
396 /// of a `&` (e.g., the missing lifetime in something like `&T`)
397 /// - **Dyn Bound** -- if you have something like `Box<dyn Foo>`,
398 /// there is an elided lifetime bound (`Box<dyn Foo + 'X>`). These
399 /// elided bounds follow special rules. Note that this only covers
400 /// cases where *nothing* is written; the `'_` in `Box<dyn Foo +
401 /// '_>` is a case of "modern" elision.
402 /// - **Deprecated** -- this covers cases like `Ref<T>`, where the lifetime
403 /// parameter to ref is completely elided. `Ref<'_, T>` would be the modern,
404 /// non-deprecated equivalent.
406 /// Currently, the handling of lifetime elision is somewhat spread out
407 /// between HIR lowering and -- as described below -- the
408 /// `resolve_lifetime` module. Often we "fallthrough" to that code by generating
409 /// an "elided" or "underscore" lifetime name. In the future, we probably want to move
410 /// everything into HIR lowering.
411 #[derive(Copy, Clone, Debug)]
412 enum AnonymousLifetimeMode {
413 /// For **Modern** cases, create a new anonymous region parameter
414 /// and reference that.
416 /// For **Dyn Bound** cases, pass responsibility to
417 /// `resolve_lifetime` code.
419 /// For **Deprecated** cases, report an error.
422 /// Give a hard error when either `&` or `'_` is written. Used to
423 /// rule out things like `where T: Foo<'_>`. Does not imply an
424 /// error on default object bounds (e.g., `Box<dyn Foo>`).
427 /// Pass responsibility to `resolve_lifetime` code for all cases.
431 impl<'a, 'hir> LoweringContext<'a, 'hir> {
432 fn lower_crate(mut self, c: &Crate) -> &'hir hir::Crate<'hir> {
433 /// Full-crate AST visitor that inserts into a fresh
434 /// `LoweringContext` any information that may be
435 /// needed from arbitrary locations in the crate,
436 /// e.g., the number of lifetime generic parameters
437 /// declared for every type and trait definition.
438 struct MiscCollector<'tcx, 'lowering, 'hir> {
439 lctx: &'tcx mut LoweringContext<'lowering, 'hir>,
442 impl MiscCollector<'_, '_, '_> {
443 fn allocate_use_tree_hir_id_counters(&mut self, tree: &UseTree) {
445 UseTreeKind::Simple(_, id1, id2) => {
446 for id in [id1, id2] {
447 self.lctx.allocate_hir_id_counter(id);
450 UseTreeKind::Glob => (),
451 UseTreeKind::Nested(ref trees) => {
452 for &(ref use_tree, id) in trees {
453 self.lctx.allocate_hir_id_counter(id);
454 self.allocate_use_tree_hir_id_counters(use_tree);
461 impl<'tcx> Visitor<'tcx> for MiscCollector<'tcx, '_, '_> {
462 fn visit_item(&mut self, item: &'tcx Item) {
463 self.lctx.allocate_hir_id_counter(item.id);
466 ItemKind::Struct(_, ref generics)
467 | ItemKind::Union(_, ref generics)
468 | ItemKind::Enum(_, ref generics)
469 | ItemKind::TyAlias(box TyAliasKind(_, ref generics, ..))
470 | ItemKind::Trait(box TraitKind(_, _, ref generics, ..)) => {
471 let def_id = self.lctx.resolver.local_def_id(item.id);
476 matches!(param.kind, ast::GenericParamKind::Lifetime { .. })
479 self.lctx.type_def_lifetime_params.insert(def_id.to_def_id(), count);
481 ItemKind::Use(ref use_tree) => {
482 self.allocate_use_tree_hir_id_counters(use_tree);
487 visit::walk_item(self, item);
490 fn visit_assoc_item(&mut self, item: &'tcx AssocItem, ctxt: AssocCtxt) {
491 self.lctx.allocate_hir_id_counter(item.id);
492 visit::walk_assoc_item(self, item, ctxt);
495 fn visit_foreign_item(&mut self, item: &'tcx ForeignItem) {
496 self.lctx.allocate_hir_id_counter(item.id);
497 visit::walk_foreign_item(self, item);
500 fn visit_ty(&mut self, t: &'tcx Ty) {
502 // Mirrors the case in visit::walk_ty
503 TyKind::BareFn(ref f) => {
504 walk_list!(self, visit_generic_param, &f.generic_params);
505 // Mirrors visit::walk_fn_decl
506 for parameter in &f.decl.inputs {
507 // We don't lower the ids of argument patterns
508 self.visit_pat(¶meter.pat);
509 self.visit_ty(¶meter.ty)
511 self.visit_fn_ret_ty(&f.decl.output)
513 _ => visit::walk_ty(self, t),
518 self.lower_node_id(CRATE_NODE_ID);
519 debug_assert!(self.node_id_to_hir_id[CRATE_NODE_ID] == Some(hir::CRATE_HIR_ID));
521 visit::walk_crate(&mut MiscCollector { lctx: &mut self }, c);
522 visit::walk_crate(&mut item::ItemLowerer { lctx: &mut self }, c);
524 let module = self.lower_mod(&c.items, c.span);
525 self.lower_attrs(hir::CRATE_HIR_ID, &c.attrs);
526 let body_ids = body_ids(&self.bodies);
528 c.proc_macros.iter().map(|id| self.node_id_to_hir_id[*id].unwrap()).collect();
530 let mut trait_map: FxHashMap<_, FxHashMap<_, _>> = FxHashMap::default();
531 for (k, v) in self.resolver.take_trait_map().into_iter() {
532 if let Some(Some(hir_id)) = self.node_id_to_hir_id.get(k) {
533 let map = trait_map.entry(hir_id.owner).or_default();
534 map.insert(hir_id.local_id, v.into_boxed_slice());
538 let mut def_id_to_hir_id = IndexVec::default();
540 for (node_id, hir_id) in self.node_id_to_hir_id.into_iter_enumerated() {
541 if let Some(def_id) = self.resolver.opt_local_def_id(node_id) {
542 if def_id_to_hir_id.len() <= def_id.index() {
543 def_id_to_hir_id.resize(def_id.index() + 1, None);
545 def_id_to_hir_id[def_id] = hir_id;
549 self.resolver.definitions().init_def_id_to_hir_id_mapping(def_id_to_hir_id);
551 #[cfg(debug_assertions)]
552 for (&id, attrs) in self.attrs.iter() {
553 // Verify that we do not store empty slices in the map.
554 if attrs.is_empty() {
555 panic!("Stored empty attributes for {:?}", id);
559 let krate = hir::Crate {
561 exported_macros: self.arena.alloc_from_iter(self.exported_macros),
562 non_exported_macro_attrs: self.arena.alloc_from_iter(self.non_exported_macro_attrs),
564 trait_items: self.trait_items,
565 impl_items: self.impl_items,
566 foreign_items: self.foreign_items,
569 trait_impls: self.trait_impls,
570 modules: self.modules,
575 self.arena.alloc(krate)
578 fn insert_item(&mut self, item: hir::Item<'hir>) -> hir::ItemId {
579 let id = hir::ItemId { def_id: item.def_id };
580 self.items.insert(id, item);
581 self.modules.entry(self.current_module).or_default().items.insert(id);
585 fn allocate_hir_id_counter(&mut self, owner: NodeId) -> hir::HirId {
586 // Set up the counter if needed.
587 self.item_local_id_counters.entry(owner).or_insert(0);
588 // Always allocate the first `HirId` for the owner itself.
589 let lowered = self.lower_node_id_with_owner(owner, owner);
590 debug_assert_eq!(lowered.local_id.as_u32(), 0);
594 fn create_stable_hashing_context(&self) -> LoweringHasher<'_> {
596 source_map: CachingSourceMapView::new(self.sess.source_map()),
597 resolver: self.resolver,
601 fn lower_node_id_generic(
604 alloc_hir_id: impl FnOnce(&mut Self) -> hir::HirId,
606 assert_ne!(ast_node_id, DUMMY_NODE_ID);
608 let min_size = ast_node_id.as_usize() + 1;
610 if min_size > self.node_id_to_hir_id.len() {
611 self.node_id_to_hir_id.resize(min_size, None);
614 if let Some(existing_hir_id) = self.node_id_to_hir_id[ast_node_id] {
617 // Generate a new `HirId`.
618 let hir_id = alloc_hir_id(self);
619 self.node_id_to_hir_id[ast_node_id] = Some(hir_id);
625 fn with_hir_id_owner<T>(&mut self, owner: NodeId, f: impl FnOnce(&mut Self) -> T) -> T {
627 .item_local_id_counters
628 .insert(owner, HIR_ID_COUNTER_LOCKED)
629 .unwrap_or_else(|| panic!("no `item_local_id_counters` entry for {:?}", owner));
630 let def_id = self.resolver.local_def_id(owner);
631 let old_owner = std::mem::replace(&mut self.current_hir_id_owner, (def_id, counter));
633 let (new_def_id, new_counter) =
634 std::mem::replace(&mut self.current_hir_id_owner, old_owner);
636 debug_assert!(def_id == new_def_id);
637 debug_assert!(new_counter >= counter);
639 let prev = self.item_local_id_counters.insert(owner, new_counter).unwrap();
640 debug_assert!(prev == HIR_ID_COUNTER_LOCKED);
644 /// This method allocates a new `HirId` for the given `NodeId` and stores it in
645 /// the `LoweringContext`'s `NodeId => HirId` map.
646 /// Take care not to call this method if the resulting `HirId` is then not
647 /// actually used in the HIR, as that would trigger an assertion in the
648 /// `HirIdValidator` later on, which makes sure that all `NodeId`s got mapped
649 /// properly. Calling the method twice with the same `NodeId` is fine though.
650 fn lower_node_id(&mut self, ast_node_id: NodeId) -> hir::HirId {
651 self.lower_node_id_generic(ast_node_id, |this| {
652 let &mut (owner, ref mut local_id_counter) = &mut this.current_hir_id_owner;
653 let local_id = *local_id_counter;
654 *local_id_counter += 1;
655 hir::HirId { owner, local_id: hir::ItemLocalId::from_u32(local_id) }
659 fn lower_node_id_with_owner(&mut self, ast_node_id: NodeId, owner: NodeId) -> hir::HirId {
660 self.lower_node_id_generic(ast_node_id, |this| {
661 let local_id_counter = this
662 .item_local_id_counters
664 .expect("called `lower_node_id_with_owner` before `allocate_hir_id_counter`");
665 let local_id = *local_id_counter;
667 // We want to be sure not to modify the counter in the map while it
668 // is also on the stack. Otherwise we'll get lost updates when writing
669 // back from the stack to the map.
670 debug_assert!(local_id != HIR_ID_COUNTER_LOCKED);
672 *local_id_counter += 1;
673 let owner = this.resolver.opt_local_def_id(owner).expect(
674 "you forgot to call `create_def` or are lowering node-IDs \
675 that do not belong to the current owner",
678 hir::HirId { owner, local_id: hir::ItemLocalId::from_u32(local_id) }
682 fn next_id(&mut self) -> hir::HirId {
683 let node_id = self.resolver.next_node_id();
684 self.lower_node_id(node_id)
687 fn lower_res(&mut self, res: Res<NodeId>) -> Res {
689 self.lower_node_id_generic(id, |_| {
690 panic!("expected `NodeId` to be lowered already for res {:#?}", res);
695 fn expect_full_res(&mut self, id: NodeId) -> Res<NodeId> {
696 self.resolver.get_partial_res(id).map_or(Res::Err, |pr| {
697 if pr.unresolved_segments() != 0 {
698 panic!("path not fully resolved: {:?}", pr);
704 fn expect_full_res_from_use(&mut self, id: NodeId) -> impl Iterator<Item = Res<NodeId>> {
705 self.resolver.get_import_res(id).present_items()
708 fn diagnostic(&self) -> &rustc_errors::Handler {
709 self.sess.diagnostic()
712 /// Reuses the span but adds information like the kind of the desugaring and features that are
713 /// allowed inside this span.
714 fn mark_span_with_reason(
716 reason: DesugaringKind,
718 allow_internal_unstable: Option<Lrc<[Symbol]>>,
720 span.mark_with_reason(
721 allow_internal_unstable,
724 self.create_stable_hashing_context(),
728 fn with_anonymous_lifetime_mode<R>(
730 anonymous_lifetime_mode: AnonymousLifetimeMode,
731 op: impl FnOnce(&mut Self) -> R,
734 "with_anonymous_lifetime_mode(anonymous_lifetime_mode={:?})",
735 anonymous_lifetime_mode,
737 let old_anonymous_lifetime_mode = self.anonymous_lifetime_mode;
738 self.anonymous_lifetime_mode = anonymous_lifetime_mode;
739 let result = op(self);
740 self.anonymous_lifetime_mode = old_anonymous_lifetime_mode;
742 "with_anonymous_lifetime_mode: restoring anonymous_lifetime_mode={:?}",
743 old_anonymous_lifetime_mode
748 /// Creates a new `hir::GenericParam` for every new lifetime and
749 /// type parameter encountered while evaluating `f`. Definitions
750 /// are created with the parent provided. If no `parent_id` is
751 /// provided, no definitions will be returned.
753 /// Presuming that in-band lifetimes are enabled, then
754 /// `self.anonymous_lifetime_mode` will be updated to match the
755 /// parameter while `f` is running (and restored afterwards).
756 fn collect_in_band_defs<T>(
758 parent_def_id: LocalDefId,
759 anonymous_lifetime_mode: AnonymousLifetimeMode,
760 f: impl FnOnce(&mut Self) -> (Vec<hir::GenericParam<'hir>>, T),
761 ) -> (Vec<hir::GenericParam<'hir>>, T) {
762 assert!(!self.is_collecting_in_band_lifetimes);
763 assert!(self.lifetimes_to_define.is_empty());
764 let old_anonymous_lifetime_mode = self.anonymous_lifetime_mode;
766 self.anonymous_lifetime_mode = anonymous_lifetime_mode;
767 self.is_collecting_in_band_lifetimes = true;
769 let (in_band_ty_params, res) = f(self);
771 self.is_collecting_in_band_lifetimes = false;
772 self.anonymous_lifetime_mode = old_anonymous_lifetime_mode;
774 let lifetimes_to_define = self.lifetimes_to_define.split_off(0);
776 let params = lifetimes_to_define
778 .map(|(span, hir_name)| self.lifetime_to_generic_param(span, hir_name, parent_def_id))
779 .chain(in_band_ty_params.into_iter())
785 /// Converts a lifetime into a new generic parameter.
786 fn lifetime_to_generic_param(
790 parent_def_id: LocalDefId,
791 ) -> hir::GenericParam<'hir> {
792 let node_id = self.resolver.next_node_id();
794 // Get the name we'll use to make the def-path. Note
795 // that collisions are ok here and this shouldn't
796 // really show up for end-user.
797 let (str_name, kind) = match hir_name {
798 ParamName::Plain(ident) => (ident.name, hir::LifetimeParamKind::InBand),
799 ParamName::Fresh(_) => (kw::UnderscoreLifetime, hir::LifetimeParamKind::Elided),
800 ParamName::Error => (kw::UnderscoreLifetime, hir::LifetimeParamKind::Error),
803 // Add a definition for the in-band lifetime def.
804 self.resolver.create_def(
807 DefPathData::LifetimeNs(str_name),
813 hir_id: self.lower_node_id(node_id),
817 pure_wrt_drop: false,
818 kind: hir::GenericParamKind::Lifetime { kind },
822 /// When there is a reference to some lifetime `'a`, and in-band
823 /// lifetimes are enabled, then we want to push that lifetime into
824 /// the vector of names to define later. In that case, it will get
825 /// added to the appropriate generics.
826 fn maybe_collect_in_band_lifetime(&mut self, ident: Ident) {
827 if !self.is_collecting_in_band_lifetimes {
831 if !self.sess.features_untracked().in_band_lifetimes {
835 if self.in_scope_lifetimes.contains(&ParamName::Plain(ident.normalize_to_macros_2_0())) {
839 let hir_name = ParamName::Plain(ident);
841 if self.lifetimes_to_define.iter().any(|(_, lt_name)| {
842 lt_name.normalize_to_macros_2_0() == hir_name.normalize_to_macros_2_0()
847 self.lifetimes_to_define.push((ident.span, hir_name));
850 /// When we have either an elided or `'_` lifetime in an impl
851 /// header, we convert it to an in-band lifetime.
852 fn collect_fresh_in_band_lifetime(&mut self, span: Span) -> ParamName {
853 assert!(self.is_collecting_in_band_lifetimes);
854 let index = self.lifetimes_to_define.len() + self.in_scope_lifetimes.len();
855 let hir_name = ParamName::Fresh(index);
856 self.lifetimes_to_define.push((span, hir_name));
860 // Evaluates `f` with the lifetimes in `params` in-scope.
861 // This is used to track which lifetimes have already been defined, and
862 // which are new in-band lifetimes that need to have a definition created
864 fn with_in_scope_lifetime_defs<T>(
866 params: &[GenericParam],
867 f: impl FnOnce(&mut Self) -> T,
869 let old_len = self.in_scope_lifetimes.len();
870 let lt_def_names = params.iter().filter_map(|param| match param.kind {
871 GenericParamKind::Lifetime { .. } => {
872 Some(ParamName::Plain(param.ident.normalize_to_macros_2_0()))
876 self.in_scope_lifetimes.extend(lt_def_names);
880 self.in_scope_lifetimes.truncate(old_len);
884 /// Appends in-band lifetime defs and argument-position `impl
885 /// Trait` defs to the existing set of generics.
887 /// Presuming that in-band lifetimes are enabled, then
888 /// `self.anonymous_lifetime_mode` will be updated to match the
889 /// parameter while `f` is running (and restored afterwards).
890 fn add_in_band_defs<T>(
893 parent_def_id: LocalDefId,
894 anonymous_lifetime_mode: AnonymousLifetimeMode,
895 f: impl FnOnce(&mut Self, &mut Vec<hir::GenericParam<'hir>>) -> T,
896 ) -> (hir::Generics<'hir>, T) {
897 let (in_band_defs, (mut lowered_generics, res)) =
898 self.with_in_scope_lifetime_defs(&generics.params, |this| {
899 this.collect_in_band_defs(parent_def_id, anonymous_lifetime_mode, |this| {
900 let mut params = Vec::new();
901 // Note: it is necessary to lower generics *before* calling `f`.
902 // When lowering `async fn`, there's a final step when lowering
903 // the return type that assumes that all in-scope lifetimes have
904 // already been added to either `in_scope_lifetimes` or
905 // `lifetimes_to_define`. If we swapped the order of these two,
906 // in-band-lifetimes introduced by generics or where-clauses
907 // wouldn't have been added yet.
908 let generics = this.lower_generics_mut(
910 ImplTraitContext::Universal(&mut params, this.current_hir_id_owner.0),
912 let res = f(this, &mut params);
913 (params, (generics, res))
917 lowered_generics.params.extend(in_band_defs);
919 let lowered_generics = lowered_generics.into_generics(self.arena);
920 (lowered_generics, res)
923 fn with_dyn_type_scope<T>(&mut self, in_scope: bool, f: impl FnOnce(&mut Self) -> T) -> T {
924 let was_in_dyn_type = self.is_in_dyn_type;
925 self.is_in_dyn_type = in_scope;
927 let result = f(self);
929 self.is_in_dyn_type = was_in_dyn_type;
934 fn with_new_scopes<T>(&mut self, f: impl FnOnce(&mut Self) -> T) -> T {
935 let was_in_loop_condition = self.is_in_loop_condition;
936 self.is_in_loop_condition = false;
938 let catch_scopes = mem::take(&mut self.catch_scopes);
939 let loop_scopes = mem::take(&mut self.loop_scopes);
941 self.catch_scopes = catch_scopes;
942 self.loop_scopes = loop_scopes;
944 self.is_in_loop_condition = was_in_loop_condition;
949 fn lower_attrs(&mut self, id: hir::HirId, attrs: &[Attribute]) -> Option<&'hir [Attribute]> {
950 if attrs.is_empty() {
953 let ret = self.arena.alloc_from_iter(attrs.iter().map(|a| self.lower_attr(a)));
954 debug_assert!(!ret.is_empty());
955 self.attrs.insert(id, ret);
960 fn lower_attr(&self, attr: &Attribute) -> Attribute {
961 // Note that we explicitly do not walk the path. Since we don't really
962 // lower attributes (we use the AST version) there is nowhere to keep
963 // the `HirId`s. We don't actually need HIR version of attributes anyway.
964 // Tokens are also not needed after macro expansion and parsing.
965 let kind = match attr.kind {
966 AttrKind::Normal(ref item, _) => AttrKind::Normal(
968 path: item.path.clone(),
969 args: self.lower_mac_args(&item.args),
974 AttrKind::DocComment(comment_kind, data) => AttrKind::DocComment(comment_kind, data),
977 Attribute { kind, id: attr.id, style: attr.style, span: attr.span }
980 fn alias_attrs(&mut self, id: hir::HirId, target_id: hir::HirId) {
981 if let Some(&a) = self.attrs.get(&target_id) {
982 debug_assert!(!a.is_empty());
983 self.attrs.insert(id, a);
987 fn lower_mac_args(&self, args: &MacArgs) -> MacArgs {
989 MacArgs::Empty => MacArgs::Empty,
990 MacArgs::Delimited(dspan, delim, ref tokens) => {
991 // This is either a non-key-value attribute, or a `macro_rules!` body.
992 // We either not have any nonterminals present (in the case of an attribute),
993 // or have tokens available for all nonterminals in the case of a nested
994 // `macro_rules`: e.g:
997 // macro_rules! outer {
999 // macro_rules! inner {
1006 // In both cases, we don't want to synthesize any tokens
1010 self.lower_token_stream(tokens.clone(), CanSynthesizeMissingTokens::No),
1013 // This is an inert key-value attribute - it will never be visible to macros
1014 // after it gets lowered to HIR. Therefore, we can synthesize tokens with fake
1015 // spans to handle nonterminals in `#[doc]` (e.g. `#[doc = $e]`).
1016 MacArgs::Eq(eq_span, ref token) => {
1017 // In valid code the value is always representable as a single literal token.
1018 fn unwrap_single_token(sess: &Session, tokens: TokenStream, span: Span) -> Token {
1019 if tokens.len() != 1 {
1021 .delay_span_bug(span, "multiple tokens in key-value attribute's value");
1023 match tokens.into_trees().next() {
1024 Some(TokenTree::Token(token)) => token,
1025 Some(TokenTree::Delimited(_, delim, tokens)) => {
1026 if delim != token::NoDelim {
1027 sess.diagnostic().delay_span_bug(
1029 "unexpected delimiter in key-value attribute's value",
1032 unwrap_single_token(sess, tokens, span)
1034 None => Token::dummy(),
1038 let tokens = FlattenNonterminals {
1039 parse_sess: &self.sess.parse_sess,
1040 synthesize_tokens: CanSynthesizeMissingTokens::Yes,
1041 nt_to_tokenstream: self.nt_to_tokenstream,
1043 .process_token(token.clone());
1044 MacArgs::Eq(eq_span, unwrap_single_token(self.sess, tokens, token.span))
1049 fn lower_token_stream(
1051 tokens: TokenStream,
1052 synthesize_tokens: CanSynthesizeMissingTokens,
1054 FlattenNonterminals {
1055 parse_sess: &self.sess.parse_sess,
1057 nt_to_tokenstream: self.nt_to_tokenstream,
1059 .process_token_stream(tokens)
1062 /// Given an associated type constraint like one of these:
1065 /// T: Iterator<Item: Debug>
1067 /// T: Iterator<Item = Debug>
1071 /// returns a `hir::TypeBinding` representing `Item`.
1072 fn lower_assoc_ty_constraint(
1074 constraint: &AssocTyConstraint,
1075 mut itctx: ImplTraitContext<'_, 'hir>,
1076 ) -> hir::TypeBinding<'hir> {
1077 debug!("lower_assoc_ty_constraint(constraint={:?}, itctx={:?})", constraint, itctx);
1079 // lower generic arguments of identifier in constraint
1080 let gen_args = if let Some(ref gen_args) = constraint.gen_args {
1081 let gen_args_ctor = match gen_args {
1082 GenericArgs::AngleBracketed(ref data) => {
1083 self.lower_angle_bracketed_parameter_data(
1085 ParamMode::Explicit,
1090 GenericArgs::Parenthesized(ref data) => {
1091 let mut err = self.sess.struct_span_err(
1093 "parenthesized generic arguments cannot be used in associated type constraints"
1095 // FIXME: try to write a suggestion here
1097 self.lower_angle_bracketed_parameter_data(
1098 &data.as_angle_bracketed_args(),
1099 ParamMode::Explicit,
1105 self.arena.alloc(gen_args_ctor.into_generic_args(&self.arena))
1107 self.arena.alloc(hir::GenericArgs::none())
1110 let kind = match constraint.kind {
1111 AssocTyConstraintKind::Equality { ref ty } => {
1112 hir::TypeBindingKind::Equality { ty: self.lower_ty(ty, itctx) }
1114 AssocTyConstraintKind::Bound { ref bounds } => {
1115 let mut capturable_lifetimes;
1116 let mut parent_def_id = self.current_hir_id_owner.0;
1117 // Piggy-back on the `impl Trait` context to figure out the correct behavior.
1118 let (desugar_to_impl_trait, itctx) = match itctx {
1119 // We are in the return position:
1121 // fn foo() -> impl Iterator<Item: Debug>
1125 // fn foo() -> impl Iterator<Item = impl Debug>
1126 ImplTraitContext::ReturnPositionOpaqueTy { .. }
1127 | ImplTraitContext::TypeAliasesOpaqueTy { .. } => (true, itctx),
1129 // We are in the argument position, but within a dyn type:
1131 // fn foo(x: dyn Iterator<Item: Debug>)
1135 // fn foo(x: dyn Iterator<Item = impl Debug>)
1136 ImplTraitContext::Universal(_, parent) if self.is_in_dyn_type => {
1137 parent_def_id = parent;
1141 // In `type Foo = dyn Iterator<Item: Debug>` we desugar to
1142 // `type Foo = dyn Iterator<Item = impl Debug>` but we have to override the
1143 // "impl trait context" to permit `impl Debug` in this position (it desugars
1144 // then to an opaque type).
1146 // FIXME: this is only needed until `impl Trait` is allowed in type aliases.
1147 ImplTraitContext::Disallowed(_) if self.is_in_dyn_type => {
1148 capturable_lifetimes = FxHashSet::default();
1151 ImplTraitContext::TypeAliasesOpaqueTy {
1152 capturable_lifetimes: &mut capturable_lifetimes,
1157 // We are in the parameter position, but not within a dyn type:
1159 // fn foo(x: impl Iterator<Item: Debug>)
1161 // so we leave it as is and this gets expanded in astconv to a bound like
1162 // `<T as Iterator>::Item: Debug` where `T` is the type parameter for the
1164 _ => (false, itctx),
1167 if desugar_to_impl_trait {
1168 // Desugar `AssocTy: Bounds` into `AssocTy = impl Bounds`. We do this by
1169 // constructing the HIR for `impl bounds...` and then lowering that.
1171 let impl_trait_node_id = self.resolver.next_node_id();
1172 self.resolver.create_def(
1175 DefPathData::ImplTrait,
1180 self.with_dyn_type_scope(false, |this| {
1181 let node_id = this.resolver.next_node_id();
1182 let ty = this.lower_ty(
1185 kind: TyKind::ImplTrait(impl_trait_node_id, bounds.clone()),
1186 span: constraint.span,
1192 hir::TypeBindingKind::Equality { ty }
1195 // Desugar `AssocTy: Bounds` into a type binding where the
1196 // later desugars into a trait predicate.
1197 let bounds = self.lower_param_bounds(bounds, itctx);
1199 hir::TypeBindingKind::Constraint { bounds }
1205 hir_id: self.lower_node_id(constraint.id),
1206 ident: constraint.ident,
1209 span: constraint.span,
1213 fn lower_generic_arg(
1215 arg: &ast::GenericArg,
1216 itctx: ImplTraitContext<'_, 'hir>,
1217 ) -> hir::GenericArg<'hir> {
1219 ast::GenericArg::Lifetime(lt) => GenericArg::Lifetime(self.lower_lifetime(<)),
1220 ast::GenericArg::Type(ty) => {
1223 let hir_id = self.lower_node_id(ty.id);
1224 return GenericArg::Infer(hir::InferArg { hir_id, span: ty.span });
1226 // We parse const arguments as path types as we cannot distinguish them during
1227 // parsing. We try to resolve that ambiguity by attempting resolution in both the
1228 // type and value namespaces. If we resolved the path in the value namespace, we
1229 // transform it into a generic const argument.
1230 TyKind::Path(ref qself, ref path) => {
1231 if let Some(partial_res) = self.resolver.get_partial_res(ty.id) {
1232 let res = partial_res.base_res();
1233 if !res.matches_ns(Namespace::TypeNS) {
1235 "lower_generic_arg: Lowering type argument as const argument: {:?}",
1239 // Construct a AnonConst where the expr is the "ty"'s path.
1241 let parent_def_id = self.current_hir_id_owner.0;
1242 let node_id = self.resolver.next_node_id();
1244 // Add a definition for the in-band const def.
1245 self.resolver.create_def(
1248 DefPathData::AnonConst,
1253 let path_expr = Expr {
1255 kind: ExprKind::Path(qself.clone(), path.clone()),
1257 attrs: AttrVec::new(),
1261 let ct = self.with_new_scopes(|this| hir::AnonConst {
1262 hir_id: this.lower_node_id(node_id),
1263 body: this.lower_const_body(path_expr.span, Some(&path_expr)),
1265 return GenericArg::Const(ConstArg { value: ct, span: ty.span });
1271 GenericArg::Type(self.lower_ty_direct(&ty, itctx))
1273 ast::GenericArg::Const(ct) => GenericArg::Const(ConstArg {
1274 value: self.lower_anon_const(&ct),
1275 span: ct.value.span,
1280 fn lower_ty(&mut self, t: &Ty, itctx: ImplTraitContext<'_, 'hir>) -> &'hir hir::Ty<'hir> {
1281 self.arena.alloc(self.lower_ty_direct(t, itctx))
1287 qself: &Option<QSelf>,
1289 param_mode: ParamMode,
1290 itctx: ImplTraitContext<'_, 'hir>,
1291 ) -> hir::Ty<'hir> {
1292 let id = self.lower_node_id(t.id);
1293 let qpath = self.lower_qpath(t.id, qself, path, param_mode, itctx);
1294 let ty = self.ty_path(id, t.span, qpath);
1295 if let hir::TyKind::TraitObject(..) = ty.kind {
1296 self.maybe_lint_bare_trait(t.span, t.id, qself.is_none() && path.is_global());
1301 fn ty(&mut self, span: Span, kind: hir::TyKind<'hir>) -> hir::Ty<'hir> {
1302 hir::Ty { hir_id: self.next_id(), kind, span }
1305 fn ty_tup(&mut self, span: Span, tys: &'hir [hir::Ty<'hir>]) -> hir::Ty<'hir> {
1306 self.ty(span, hir::TyKind::Tup(tys))
1309 fn lower_ty_direct(&mut self, t: &Ty, mut itctx: ImplTraitContext<'_, 'hir>) -> hir::Ty<'hir> {
1310 let kind = match t.kind {
1311 TyKind::Infer => hir::TyKind::Infer,
1312 TyKind::Err => hir::TyKind::Err,
1313 // FIXME(unnamed_fields): IMPLEMENTATION IN PROGRESS
1314 TyKind::AnonymousStruct(ref _fields, _recovered) => {
1315 self.sess.struct_span_err(t.span, "anonymous structs are unimplemented").emit();
1318 TyKind::AnonymousUnion(ref _fields, _recovered) => {
1319 self.sess.struct_span_err(t.span, "anonymous unions are unimplemented").emit();
1322 TyKind::Slice(ref ty) => hir::TyKind::Slice(self.lower_ty(ty, itctx)),
1323 TyKind::Ptr(ref mt) => hir::TyKind::Ptr(self.lower_mt(mt, itctx)),
1324 TyKind::Rptr(ref region, ref mt) => {
1325 let span = self.sess.source_map().next_point(t.span.shrink_to_lo());
1326 let lifetime = match *region {
1327 Some(ref lt) => self.lower_lifetime(lt),
1328 None => self.elided_ref_lifetime(span),
1330 hir::TyKind::Rptr(lifetime, self.lower_mt(mt, itctx))
1332 TyKind::BareFn(ref f) => self.with_in_scope_lifetime_defs(&f.generic_params, |this| {
1333 this.with_anonymous_lifetime_mode(AnonymousLifetimeMode::PassThrough, |this| {
1334 let span = this.sess.source_map().next_point(t.span.shrink_to_lo());
1335 hir::TyKind::BareFn(this.arena.alloc(hir::BareFnTy {
1336 generic_params: this.lower_generic_params(
1338 &NodeMap::default(),
1339 ImplTraitContext::disallowed(),
1341 unsafety: this.lower_unsafety(f.unsafety),
1342 abi: this.lower_extern(f.ext, span, t.id),
1343 decl: this.lower_fn_decl(&f.decl, None, false, None),
1344 param_names: this.lower_fn_params_to_names(&f.decl),
1348 TyKind::Never => hir::TyKind::Never,
1349 TyKind::Tup(ref tys) => {
1350 hir::TyKind::Tup(self.arena.alloc_from_iter(
1351 tys.iter().map(|ty| self.lower_ty_direct(ty, itctx.reborrow())),
1354 TyKind::Paren(ref ty) => {
1355 return self.lower_ty_direct(ty, itctx);
1357 TyKind::Path(ref qself, ref path) => {
1358 return self.lower_path_ty(t, qself, path, ParamMode::Explicit, itctx);
1360 TyKind::ImplicitSelf => {
1361 let res = self.expect_full_res(t.id);
1362 let res = self.lower_res(res);
1363 hir::TyKind::Path(hir::QPath::Resolved(
1365 self.arena.alloc(hir::Path {
1367 segments: arena_vec![self; hir::PathSegment::from_ident(
1368 Ident::with_dummy_span(kw::SelfUpper)
1374 TyKind::Array(ref ty, ref length) => {
1375 hir::TyKind::Array(self.lower_ty(ty, itctx), self.lower_anon_const(length))
1377 TyKind::Typeof(ref expr) => hir::TyKind::Typeof(self.lower_anon_const(expr)),
1378 TyKind::TraitObject(ref bounds, kind) => {
1379 let mut lifetime_bound = None;
1380 let (bounds, lifetime_bound) = self.with_dyn_type_scope(true, |this| {
1382 this.arena.alloc_from_iter(bounds.iter().filter_map(
1383 |bound| match *bound {
1384 GenericBound::Trait(
1386 TraitBoundModifier::None | TraitBoundModifier::MaybeConst,
1387 ) => Some(this.lower_poly_trait_ref(ty, itctx.reborrow())),
1388 // `?const ?Bound` will cause an error during AST validation
1389 // anyways, so treat it like `?Bound` as compilation proceeds.
1390 GenericBound::Trait(
1392 TraitBoundModifier::Maybe | TraitBoundModifier::MaybeConstMaybe,
1394 GenericBound::Outlives(ref lifetime) => {
1395 if lifetime_bound.is_none() {
1396 lifetime_bound = Some(this.lower_lifetime(lifetime));
1402 let lifetime_bound =
1403 lifetime_bound.unwrap_or_else(|| this.elided_dyn_bound(t.span));
1404 (bounds, lifetime_bound)
1406 if kind != TraitObjectSyntax::Dyn {
1407 self.maybe_lint_bare_trait(t.span, t.id, false);
1409 hir::TyKind::TraitObject(bounds, lifetime_bound, kind)
1411 TyKind::ImplTrait(def_node_id, ref bounds) => {
1414 ImplTraitContext::ReturnPositionOpaqueTy { fn_def_id, origin } => self
1415 .lower_opaque_impl_trait(
1421 |this| this.lower_param_bounds(bounds, itctx),
1423 ImplTraitContext::TypeAliasesOpaqueTy { ref capturable_lifetimes } => {
1424 // Reset capturable lifetimes, any nested impl trait
1425 // types will inherit lifetimes from this opaque type,
1426 // so don't need to capture them again.
1427 let nested_itctx = ImplTraitContext::TypeAliasesOpaqueTy {
1428 capturable_lifetimes: &mut FxHashSet::default(),
1430 self.lower_opaque_impl_trait(
1433 hir::OpaqueTyOrigin::TyAlias,
1435 Some(capturable_lifetimes),
1436 |this| this.lower_param_bounds(bounds, nested_itctx),
1439 ImplTraitContext::Universal(in_band_ty_params, parent_def_id) => {
1440 // Add a definition for the in-band `Param`.
1441 let def_id = self.resolver.local_def_id(def_node_id);
1443 let hir_bounds = self.lower_param_bounds(
1445 ImplTraitContext::Universal(in_band_ty_params, parent_def_id),
1447 // Set the name to `impl Bound1 + Bound2`.
1448 let ident = Ident::from_str_and_span(&pprust::ty_to_string(t), span);
1449 in_band_ty_params.push(hir::GenericParam {
1450 hir_id: self.lower_node_id(def_node_id),
1451 name: ParamName::Plain(ident),
1452 pure_wrt_drop: false,
1455 kind: hir::GenericParamKind::Type {
1457 synthetic: Some(hir::SyntheticTyParamKind::ImplTrait),
1461 hir::TyKind::Path(hir::QPath::Resolved(
1463 self.arena.alloc(hir::Path {
1465 res: Res::Def(DefKind::TyParam, def_id.to_def_id()),
1466 segments: arena_vec![self; hir::PathSegment::from_ident(ident)],
1470 ImplTraitContext::Disallowed(_) => {
1471 let mut err = struct_span_err!(
1475 "`impl Trait` not allowed outside of {}",
1476 "function and method return types",
1483 TyKind::MacCall(_) => panic!("`TyKind::MacCall` should have been expanded by now"),
1484 TyKind::CVarArgs => {
1485 self.sess.delay_span_bug(
1487 "`TyKind::CVarArgs` should have been handled elsewhere",
1493 hir::Ty { kind, span: t.span, hir_id: self.lower_node_id(t.id) }
1496 fn lower_opaque_impl_trait(
1499 fn_def_id: Option<DefId>,
1500 origin: hir::OpaqueTyOrigin,
1501 opaque_ty_node_id: NodeId,
1502 capturable_lifetimes: Option<&FxHashSet<hir::LifetimeName>>,
1503 lower_bounds: impl FnOnce(&mut Self) -> hir::GenericBounds<'hir>,
1504 ) -> hir::TyKind<'hir> {
1506 "lower_opaque_impl_trait(fn_def_id={:?}, opaque_ty_node_id={:?}, span={:?})",
1507 fn_def_id, opaque_ty_node_id, span,
1510 // Make sure we know that some funky desugaring has been going on here.
1511 // This is a first: there is code in other places like for loop
1512 // desugaring that explicitly states that we don't want to track that.
1513 // Not tracking it makes lints in rustc and clippy very fragile, as
1514 // frequently opened issues show.
1515 let opaque_ty_span = self.mark_span_with_reason(DesugaringKind::OpaqueTy, span, None);
1517 let opaque_ty_def_id = self.resolver.local_def_id(opaque_ty_node_id);
1519 self.allocate_hir_id_counter(opaque_ty_node_id);
1521 let hir_bounds = self.with_hir_id_owner(opaque_ty_node_id, lower_bounds);
1523 let (lifetimes, lifetime_defs) = self.lifetimes_from_impl_trait_bounds(
1527 capturable_lifetimes,
1530 debug!("lower_opaque_impl_trait: lifetimes={:#?}", lifetimes);
1532 debug!("lower_opaque_impl_trait: lifetime_defs={:#?}", lifetime_defs);
1534 self.with_hir_id_owner(opaque_ty_node_id, move |lctx| {
1535 let opaque_ty_item = hir::OpaqueTy {
1536 generics: hir::Generics {
1537 params: lifetime_defs,
1538 where_clause: hir::WhereClause { predicates: &[], span },
1542 impl_trait_fn: fn_def_id,
1546 trace!("lower_opaque_impl_trait: {:#?}", opaque_ty_def_id);
1547 lctx.generate_opaque_type(opaque_ty_def_id, opaque_ty_item, span, opaque_ty_span);
1549 // `impl Trait` now just becomes `Foo<'a, 'b, ..>`.
1550 hir::TyKind::OpaqueDef(hir::ItemId { def_id: opaque_ty_def_id }, lifetimes)
1554 /// Registers a new opaque type with the proper `NodeId`s and
1555 /// returns the lowered node-ID for the opaque type.
1556 fn generate_opaque_type(
1558 opaque_ty_id: LocalDefId,
1559 opaque_ty_item: hir::OpaqueTy<'hir>,
1561 opaque_ty_span: Span,
1563 let opaque_ty_item_kind = hir::ItemKind::OpaqueTy(opaque_ty_item);
1564 // Generate an `type Foo = impl Trait;` declaration.
1565 trace!("registering opaque type with id {:#?}", opaque_ty_id);
1566 let opaque_ty_item = hir::Item {
1567 def_id: opaque_ty_id,
1568 ident: Ident::invalid(),
1569 kind: opaque_ty_item_kind,
1570 vis: respan(span.shrink_to_lo(), hir::VisibilityKind::Inherited),
1571 span: opaque_ty_span,
1574 // Insert the item into the global item list. This usually happens
1575 // automatically for all AST items. But this opaque type item
1576 // does not actually exist in the AST.
1577 self.insert_item(opaque_ty_item);
1580 fn lifetimes_from_impl_trait_bounds(
1582 opaque_ty_id: NodeId,
1583 parent_def_id: LocalDefId,
1584 bounds: hir::GenericBounds<'hir>,
1585 lifetimes_to_include: Option<&FxHashSet<hir::LifetimeName>>,
1586 ) -> (&'hir [hir::GenericArg<'hir>], &'hir [hir::GenericParam<'hir>]) {
1588 "lifetimes_from_impl_trait_bounds(opaque_ty_id={:?}, \
1589 parent_def_id={:?}, \
1591 opaque_ty_id, parent_def_id, bounds,
1594 // This visitor walks over `impl Trait` bounds and creates defs for all lifetimes that
1595 // appear in the bounds, excluding lifetimes that are created within the bounds.
1596 // E.g., `'a`, `'b`, but not `'c` in `impl for<'c> SomeTrait<'a, 'b, 'c>`.
1597 struct ImplTraitLifetimeCollector<'r, 'a, 'hir> {
1598 context: &'r mut LoweringContext<'a, 'hir>,
1600 opaque_ty_id: NodeId,
1601 collect_elided_lifetimes: bool,
1602 currently_bound_lifetimes: Vec<hir::LifetimeName>,
1603 already_defined_lifetimes: FxHashSet<hir::LifetimeName>,
1604 output_lifetimes: Vec<hir::GenericArg<'hir>>,
1605 output_lifetime_params: Vec<hir::GenericParam<'hir>>,
1606 lifetimes_to_include: Option<&'r FxHashSet<hir::LifetimeName>>,
1609 impl<'r, 'a, 'v, 'hir> intravisit::Visitor<'v> for ImplTraitLifetimeCollector<'r, 'a, 'hir> {
1610 type Map = intravisit::ErasedMap<'v>;
1612 fn nested_visit_map(&mut self) -> intravisit::NestedVisitorMap<Self::Map> {
1613 intravisit::NestedVisitorMap::None
1616 fn visit_generic_args(&mut self, span: Span, parameters: &'v hir::GenericArgs<'v>) {
1617 // Don't collect elided lifetimes used inside of `Fn()` syntax.
1618 if parameters.parenthesized {
1619 let old_collect_elided_lifetimes = self.collect_elided_lifetimes;
1620 self.collect_elided_lifetimes = false;
1621 intravisit::walk_generic_args(self, span, parameters);
1622 self.collect_elided_lifetimes = old_collect_elided_lifetimes;
1624 intravisit::walk_generic_args(self, span, parameters);
1628 fn visit_ty(&mut self, t: &'v hir::Ty<'v>) {
1629 // Don't collect elided lifetimes used inside of `fn()` syntax.
1630 if let hir::TyKind::BareFn(_) = t.kind {
1631 let old_collect_elided_lifetimes = self.collect_elided_lifetimes;
1632 self.collect_elided_lifetimes = false;
1634 // Record the "stack height" of `for<'a>` lifetime bindings
1635 // to be able to later fully undo their introduction.
1636 let old_len = self.currently_bound_lifetimes.len();
1637 intravisit::walk_ty(self, t);
1638 self.currently_bound_lifetimes.truncate(old_len);
1640 self.collect_elided_lifetimes = old_collect_elided_lifetimes;
1642 intravisit::walk_ty(self, t)
1646 fn visit_poly_trait_ref(
1648 trait_ref: &'v hir::PolyTraitRef<'v>,
1649 modifier: hir::TraitBoundModifier,
1651 // Record the "stack height" of `for<'a>` lifetime bindings
1652 // to be able to later fully undo their introduction.
1653 let old_len = self.currently_bound_lifetimes.len();
1654 intravisit::walk_poly_trait_ref(self, trait_ref, modifier);
1655 self.currently_bound_lifetimes.truncate(old_len);
1658 fn visit_generic_param(&mut self, param: &'v hir::GenericParam<'v>) {
1659 // Record the introduction of 'a in `for<'a> ...`.
1660 if let hir::GenericParamKind::Lifetime { .. } = param.kind {
1661 // Introduce lifetimes one at a time so that we can handle
1662 // cases like `fn foo<'d>() -> impl for<'a, 'b: 'a, 'c: 'b + 'd>`.
1663 let lt_name = hir::LifetimeName::Param(param.name);
1664 self.currently_bound_lifetimes.push(lt_name);
1667 intravisit::walk_generic_param(self, param);
1670 fn visit_lifetime(&mut self, lifetime: &'v hir::Lifetime) {
1671 let name = match lifetime.name {
1672 hir::LifetimeName::Implicit | hir::LifetimeName::Underscore => {
1673 if self.collect_elided_lifetimes {
1674 // Use `'_` for both implicit and underscore lifetimes in
1675 // `type Foo<'_> = impl SomeTrait<'_>;`.
1676 hir::LifetimeName::Underscore
1681 hir::LifetimeName::Param(_) => lifetime.name,
1683 // Refers to some other lifetime that is "in
1684 // scope" within the type.
1685 hir::LifetimeName::ImplicitObjectLifetimeDefault => return,
1687 hir::LifetimeName::Error | hir::LifetimeName::Static => return,
1690 if !self.currently_bound_lifetimes.contains(&name)
1691 && !self.already_defined_lifetimes.contains(&name)
1692 && self.lifetimes_to_include.map_or(true, |lifetimes| lifetimes.contains(&name))
1694 self.already_defined_lifetimes.insert(name);
1696 self.output_lifetimes.push(hir::GenericArg::Lifetime(hir::Lifetime {
1697 hir_id: self.context.next_id(),
1698 span: lifetime.span,
1702 let def_node_id = self.context.resolver.next_node_id();
1704 self.context.lower_node_id_with_owner(def_node_id, self.opaque_ty_id);
1705 self.context.resolver.create_def(
1708 DefPathData::LifetimeNs(name.ident().name),
1713 let (name, kind) = match name {
1714 hir::LifetimeName::Underscore => (
1715 hir::ParamName::Plain(Ident::with_dummy_span(kw::UnderscoreLifetime)),
1716 hir::LifetimeParamKind::Elided,
1718 hir::LifetimeName::Param(param_name) => {
1719 (param_name, hir::LifetimeParamKind::Explicit)
1721 _ => panic!("expected `LifetimeName::Param` or `ParamName::Plain`"),
1724 self.output_lifetime_params.push(hir::GenericParam {
1727 span: lifetime.span,
1728 pure_wrt_drop: false,
1730 kind: hir::GenericParamKind::Lifetime { kind },
1736 let mut lifetime_collector = ImplTraitLifetimeCollector {
1738 parent: parent_def_id,
1740 collect_elided_lifetimes: true,
1741 currently_bound_lifetimes: Vec::new(),
1742 already_defined_lifetimes: FxHashSet::default(),
1743 output_lifetimes: Vec::new(),
1744 output_lifetime_params: Vec::new(),
1745 lifetimes_to_include,
1748 for bound in bounds {
1749 intravisit::walk_param_bound(&mut lifetime_collector, &bound);
1752 let ImplTraitLifetimeCollector { output_lifetimes, output_lifetime_params, .. } =
1756 self.arena.alloc_from_iter(output_lifetimes),
1757 self.arena.alloc_from_iter(output_lifetime_params),
1761 fn lower_local(&mut self, l: &Local) -> hir::Local<'hir> {
1765 .map(|t| self.lower_ty(t, ImplTraitContext::Disallowed(ImplTraitPosition::Binding)));
1766 let init = l.init.as_ref().map(|e| self.lower_expr(e));
1767 let hir_id = self.lower_node_id(l.id);
1768 self.lower_attrs(hir_id, &l.attrs);
1772 pat: self.lower_pat(&l.pat),
1775 source: hir::LocalSource::Normal,
1779 fn lower_fn_params_to_names(&mut self, decl: &FnDecl) -> &'hir [Ident] {
1780 // Skip the `...` (`CVarArgs`) trailing arguments from the AST,
1781 // as they are not explicit in HIR/Ty function signatures.
1782 // (instead, the `c_variadic` flag is set to `true`)
1783 let mut inputs = &decl.inputs[..];
1784 if decl.c_variadic() {
1785 inputs = &inputs[..inputs.len() - 1];
1787 self.arena.alloc_from_iter(inputs.iter().map(|param| match param.pat.kind {
1788 PatKind::Ident(_, ident, _) => ident,
1789 _ => Ident::new(kw::Empty, param.pat.span),
1793 // Lowers a function declaration.
1795 // `decl`: the unlowered (AST) function declaration.
1796 // `fn_def_id`: if `Some`, impl Trait arguments are lowered into generic parameters on the
1797 // given DefId, otherwise impl Trait is disallowed. Must be `Some` if
1798 // `make_ret_async` is also `Some`.
1799 // `impl_trait_return_allow`: determines whether `impl Trait` can be used in return position.
1800 // This guards against trait declarations and implementations where `impl Trait` is
1802 // `make_ret_async`: if `Some`, converts `-> T` into `-> impl Future<Output = T>` in the
1803 // return type. This is used for `async fn` declarations. The `NodeId` is the ID of the
1804 // return type `impl Trait` item.
1808 mut in_band_ty_params: Option<(DefId, &mut Vec<hir::GenericParam<'hir>>)>,
1809 impl_trait_return_allow: bool,
1810 make_ret_async: Option<NodeId>,
1811 ) -> &'hir hir::FnDecl<'hir> {
1815 in_band_ty_params: {:?}, \
1816 impl_trait_return_allow: {}, \
1817 make_ret_async: {:?})",
1818 decl, in_band_ty_params, impl_trait_return_allow, make_ret_async,
1820 let lt_mode = if make_ret_async.is_some() {
1821 // In `async fn`, argument-position elided lifetimes
1822 // must be transformed into fresh generic parameters so that
1823 // they can be applied to the opaque `impl Trait` return type.
1824 AnonymousLifetimeMode::CreateParameter
1826 self.anonymous_lifetime_mode
1829 let c_variadic = decl.c_variadic();
1831 // Remember how many lifetimes were already around so that we can
1832 // only look at the lifetime parameters introduced by the arguments.
1833 let inputs = self.with_anonymous_lifetime_mode(lt_mode, |this| {
1834 // Skip the `...` (`CVarArgs`) trailing arguments from the AST,
1835 // as they are not explicit in HIR/Ty function signatures.
1836 // (instead, the `c_variadic` flag is set to `true`)
1837 let mut inputs = &decl.inputs[..];
1839 inputs = &inputs[..inputs.len() - 1];
1841 this.arena.alloc_from_iter(inputs.iter().map(|param| {
1842 if let Some((_, ibty)) = &mut in_band_ty_params {
1843 this.lower_ty_direct(
1845 ImplTraitContext::Universal(ibty, this.current_hir_id_owner.0),
1848 this.lower_ty_direct(¶m.ty, ImplTraitContext::disallowed())
1853 let output = if let Some(ret_id) = make_ret_async {
1854 self.lower_async_fn_ret_ty(
1856 in_band_ty_params.expect("`make_ret_async` but no `fn_def_id`").0,
1861 FnRetTy::Ty(ref ty) => {
1862 let context = match in_band_ty_params {
1863 Some((def_id, _)) if impl_trait_return_allow => {
1864 ImplTraitContext::ReturnPositionOpaqueTy {
1866 origin: hir::OpaqueTyOrigin::FnReturn,
1869 _ => ImplTraitContext::disallowed(),
1871 hir::FnRetTy::Return(self.lower_ty(ty, context))
1873 FnRetTy::Default(span) => hir::FnRetTy::DefaultReturn(span),
1877 self.arena.alloc(hir::FnDecl {
1881 implicit_self: decl.inputs.get(0).map_or(hir::ImplicitSelfKind::None, |arg| {
1882 use BindingMode::{ByRef, ByValue};
1883 let is_mutable_pat = matches!(
1885 PatKind::Ident(ByValue(Mutability::Mut) | ByRef(Mutability::Mut), ..)
1889 TyKind::ImplicitSelf if is_mutable_pat => hir::ImplicitSelfKind::Mut,
1890 TyKind::ImplicitSelf => hir::ImplicitSelfKind::Imm,
1891 // Given we are only considering `ImplicitSelf` types, we needn't consider
1892 // the case where we have a mutable pattern to a reference as that would
1893 // no longer be an `ImplicitSelf`.
1894 TyKind::Rptr(_, ref mt)
1895 if mt.ty.kind.is_implicit_self() && mt.mutbl == ast::Mutability::Mut =>
1897 hir::ImplicitSelfKind::MutRef
1899 TyKind::Rptr(_, ref mt) if mt.ty.kind.is_implicit_self() => {
1900 hir::ImplicitSelfKind::ImmRef
1902 _ => hir::ImplicitSelfKind::None,
1908 // Transforms `-> T` for `async fn` into `-> OpaqueTy { .. }`
1909 // combined with the following definition of `OpaqueTy`:
1911 // type OpaqueTy<generics_from_parent_fn> = impl Future<Output = T>;
1913 // `inputs`: lowered types of parameters to the function (used to collect lifetimes)
1914 // `output`: unlowered output type (`T` in `-> T`)
1915 // `fn_def_id`: `DefId` of the parent function (used to create child impl trait definition)
1916 // `opaque_ty_node_id`: `NodeId` of the opaque `impl Trait` type that should be created
1917 // `elided_lt_replacement`: replacement for elided lifetimes in the return type
1918 fn lower_async_fn_ret_ty(
1922 opaque_ty_node_id: NodeId,
1923 ) -> hir::FnRetTy<'hir> {
1925 "lower_async_fn_ret_ty(\
1928 opaque_ty_node_id={:?})",
1929 output, fn_def_id, opaque_ty_node_id,
1932 let span = output.span();
1934 let opaque_ty_span = self.mark_span_with_reason(DesugaringKind::Async, span, None);
1936 let opaque_ty_def_id = self.resolver.local_def_id(opaque_ty_node_id);
1938 self.allocate_hir_id_counter(opaque_ty_node_id);
1940 // When we create the opaque type for this async fn, it is going to have
1941 // to capture all the lifetimes involved in the signature (including in the
1942 // return type). This is done by introducing lifetime parameters for:
1944 // - all the explicitly declared lifetimes from the impl and function itself;
1945 // - all the elided lifetimes in the fn arguments;
1946 // - all the elided lifetimes in the return type.
1948 // So for example in this snippet:
1951 // impl<'a> Foo<'a> {
1952 // async fn bar<'b>(&self, x: &'b Vec<f64>, y: &str) -> &u32 {
1953 // // ^ '0 ^ '1 ^ '2
1954 // // elided lifetimes used below
1959 // we would create an opaque type like:
1962 // type Bar<'a, 'b, '0, '1, '2> = impl Future<Output = &'2 u32>;
1965 // and we would then desugar `bar` to the equivalent of:
1968 // impl<'a> Foo<'a> {
1969 // fn bar<'b, '0, '1>(&'0 self, x: &'b Vec<f64>, y: &'1 str) -> Bar<'a, 'b, '0, '1, '_>
1973 // Note that the final parameter to `Bar` is `'_`, not `'2` --
1974 // this is because the elided lifetimes from the return type
1975 // should be figured out using the ordinary elision rules, and
1976 // this desugaring achieves that.
1978 // The variable `input_lifetimes_count` tracks the number of
1979 // lifetime parameters to the opaque type *not counting* those
1980 // lifetimes elided in the return type. This includes those
1981 // that are explicitly declared (`in_scope_lifetimes`) and
1982 // those elided lifetimes we found in the arguments (current
1983 // content of `lifetimes_to_define`). Next, we will process
1984 // the return type, which will cause `lifetimes_to_define` to
1986 let input_lifetimes_count = self.in_scope_lifetimes.len() + self.lifetimes_to_define.len();
1988 let lifetime_params = self.with_hir_id_owner(opaque_ty_node_id, |this| {
1989 // We have to be careful to get elision right here. The
1990 // idea is that we create a lifetime parameter for each
1991 // lifetime in the return type. So, given a return type
1992 // like `async fn foo(..) -> &[&u32]`, we lower to `impl
1993 // Future<Output = &'1 [ &'2 u32 ]>`.
1995 // Then, we will create `fn foo(..) -> Foo<'_, '_>`, and
1996 // hence the elision takes place at the fn site.
1997 let future_bound = this
1998 .with_anonymous_lifetime_mode(AnonymousLifetimeMode::CreateParameter, |this| {
1999 this.lower_async_fn_output_type_to_future_bound(output, fn_def_id, span)
2002 debug!("lower_async_fn_ret_ty: future_bound={:#?}", future_bound);
2004 // Calculate all the lifetimes that should be captured
2005 // by the opaque type. This should include all in-scope
2006 // lifetime parameters, including those defined in-band.
2008 // Note: this must be done after lowering the output type,
2009 // as the output type may introduce new in-band lifetimes.
2010 let lifetime_params: Vec<(Span, ParamName)> = this
2014 .map(|name| (name.ident().span, name))
2015 .chain(this.lifetimes_to_define.iter().cloned())
2018 debug!("lower_async_fn_ret_ty: in_scope_lifetimes={:#?}", this.in_scope_lifetimes);
2019 debug!("lower_async_fn_ret_ty: lifetimes_to_define={:#?}", this.lifetimes_to_define);
2020 debug!("lower_async_fn_ret_ty: lifetime_params={:#?}", lifetime_params);
2022 let generic_params =
2023 this.arena.alloc_from_iter(lifetime_params.iter().map(|(span, hir_name)| {
2024 this.lifetime_to_generic_param(*span, *hir_name, opaque_ty_def_id)
2027 let opaque_ty_item = hir::OpaqueTy {
2028 generics: hir::Generics {
2029 params: generic_params,
2030 where_clause: hir::WhereClause { predicates: &[], span },
2033 bounds: arena_vec![this; future_bound],
2034 impl_trait_fn: Some(fn_def_id),
2035 origin: hir::OpaqueTyOrigin::AsyncFn,
2038 trace!("exist ty from async fn def id: {:#?}", opaque_ty_def_id);
2039 this.generate_opaque_type(opaque_ty_def_id, opaque_ty_item, span, opaque_ty_span);
2044 // As documented above on the variable
2045 // `input_lifetimes_count`, we need to create the lifetime
2046 // arguments to our opaque type. Continuing with our example,
2047 // we're creating the type arguments for the return type:
2050 // Bar<'a, 'b, '0, '1, '_>
2053 // For the "input" lifetime parameters, we wish to create
2054 // references to the parameters themselves, including the
2055 // "implicit" ones created from parameter types (`'a`, `'b`,
2058 // For the "output" lifetime parameters, we just want to
2060 let mut generic_args = Vec::with_capacity(lifetime_params.len());
2061 generic_args.extend(lifetime_params[..input_lifetimes_count].iter().map(
2062 |&(span, hir_name)| {
2063 // Input lifetime like `'a` or `'1`:
2064 GenericArg::Lifetime(hir::Lifetime {
2065 hir_id: self.next_id(),
2067 name: hir::LifetimeName::Param(hir_name),
2071 generic_args.extend(lifetime_params[input_lifetimes_count..].iter().map(|&(span, _)|
2072 // Output lifetime like `'_`.
2073 GenericArg::Lifetime(hir::Lifetime {
2074 hir_id: self.next_id(),
2076 name: hir::LifetimeName::Implicit,
2078 let generic_args = self.arena.alloc_from_iter(generic_args);
2080 // Create the `Foo<...>` reference itself. Note that the `type
2081 // Foo = impl Trait` is, internally, created as a child of the
2082 // async fn, so the *type parameters* are inherited. It's
2083 // only the lifetime parameters that we must supply.
2085 hir::TyKind::OpaqueDef(hir::ItemId { def_id: opaque_ty_def_id }, generic_args);
2086 let opaque_ty = self.ty(opaque_ty_span, opaque_ty_ref);
2087 hir::FnRetTy::Return(self.arena.alloc(opaque_ty))
2090 /// Transforms `-> T` into `Future<Output = T>`.
2091 fn lower_async_fn_output_type_to_future_bound(
2096 ) -> hir::GenericBound<'hir> {
2097 // Compute the `T` in `Future<Output = T>` from the return type.
2098 let output_ty = match output {
2099 FnRetTy::Ty(ty) => {
2100 // Not `OpaqueTyOrigin::AsyncFn`: that's only used for the
2101 // `impl Future` opaque type that `async fn` implicitly
2103 let context = ImplTraitContext::ReturnPositionOpaqueTy {
2105 origin: hir::OpaqueTyOrigin::FnReturn,
2107 self.lower_ty(ty, context)
2109 FnRetTy::Default(ret_ty_span) => self.arena.alloc(self.ty_tup(*ret_ty_span, &[])),
2113 let future_args = self.arena.alloc(hir::GenericArgs {
2115 bindings: arena_vec![self; self.output_ty_binding(span, output_ty)],
2116 parenthesized: false,
2120 hir::GenericBound::LangItemTrait(
2121 // ::std::future::Future<future_params>
2122 hir::LangItem::Future,
2129 fn lower_param_bound(
2132 itctx: ImplTraitContext<'_, 'hir>,
2133 ) -> hir::GenericBound<'hir> {
2135 GenericBound::Trait(ref ty, modifier) => hir::GenericBound::Trait(
2136 self.lower_poly_trait_ref(ty, itctx),
2137 self.lower_trait_bound_modifier(modifier),
2139 GenericBound::Outlives(ref lifetime) => {
2140 hir::GenericBound::Outlives(self.lower_lifetime(lifetime))
2145 fn lower_lifetime(&mut self, l: &Lifetime) -> hir::Lifetime {
2146 let span = l.ident.span;
2148 ident if ident.name == kw::StaticLifetime => {
2149 self.new_named_lifetime(l.id, span, hir::LifetimeName::Static)
2151 ident if ident.name == kw::UnderscoreLifetime => match self.anonymous_lifetime_mode {
2152 AnonymousLifetimeMode::CreateParameter => {
2153 let fresh_name = self.collect_fresh_in_band_lifetime(span);
2154 self.new_named_lifetime(l.id, span, hir::LifetimeName::Param(fresh_name))
2157 AnonymousLifetimeMode::PassThrough => {
2158 self.new_named_lifetime(l.id, span, hir::LifetimeName::Underscore)
2161 AnonymousLifetimeMode::ReportError => self.new_error_lifetime(Some(l.id), span),
2164 self.maybe_collect_in_band_lifetime(ident);
2165 let param_name = ParamName::Plain(ident);
2166 self.new_named_lifetime(l.id, span, hir::LifetimeName::Param(param_name))
2171 fn new_named_lifetime(
2175 name: hir::LifetimeName,
2176 ) -> hir::Lifetime {
2177 hir::Lifetime { hir_id: self.lower_node_id(id), span, name }
2180 fn lower_generic_params_mut<'s>(
2182 params: &'s [GenericParam],
2183 add_bounds: &'s NodeMap<Vec<GenericBound>>,
2184 mut itctx: ImplTraitContext<'s, 'hir>,
2185 ) -> impl Iterator<Item = hir::GenericParam<'hir>> + Captures<'a> + Captures<'s> {
2188 .map(move |param| self.lower_generic_param(param, add_bounds, itctx.reborrow()))
2191 fn lower_generic_params(
2193 params: &[GenericParam],
2194 add_bounds: &NodeMap<Vec<GenericBound>>,
2195 itctx: ImplTraitContext<'_, 'hir>,
2196 ) -> &'hir [hir::GenericParam<'hir>] {
2197 self.arena.alloc_from_iter(self.lower_generic_params_mut(params, add_bounds, itctx))
2200 fn lower_generic_param(
2202 param: &GenericParam,
2203 add_bounds: &NodeMap<Vec<GenericBound>>,
2204 mut itctx: ImplTraitContext<'_, 'hir>,
2205 ) -> hir::GenericParam<'hir> {
2206 let mut bounds: Vec<_> = self
2207 .with_anonymous_lifetime_mode(AnonymousLifetimeMode::ReportError, |this| {
2208 this.lower_param_bounds_mut(¶m.bounds, itctx.reborrow()).collect()
2211 let (name, kind) = match param.kind {
2212 GenericParamKind::Lifetime => {
2213 let was_collecting_in_band = self.is_collecting_in_band_lifetimes;
2214 self.is_collecting_in_band_lifetimes = false;
2217 .with_anonymous_lifetime_mode(AnonymousLifetimeMode::ReportError, |this| {
2218 this.lower_lifetime(&Lifetime { id: param.id, ident: param.ident })
2220 let param_name = match lt.name {
2221 hir::LifetimeName::Param(param_name) => param_name,
2222 hir::LifetimeName::Implicit
2223 | hir::LifetimeName::Underscore
2224 | hir::LifetimeName::Static => hir::ParamName::Plain(lt.name.ident()),
2225 hir::LifetimeName::ImplicitObjectLifetimeDefault => {
2226 self.sess.diagnostic().span_bug(
2228 "object-lifetime-default should not occur here",
2231 hir::LifetimeName::Error => ParamName::Error,
2235 hir::GenericParamKind::Lifetime { kind: hir::LifetimeParamKind::Explicit };
2237 self.is_collecting_in_band_lifetimes = was_collecting_in_band;
2241 GenericParamKind::Type { ref default, .. } => {
2242 let add_bounds = add_bounds.get(¶m.id).map_or(&[][..], |x| &x);
2243 if !add_bounds.is_empty() {
2244 let params = self.lower_param_bounds_mut(add_bounds, itctx.reborrow());
2245 bounds.extend(params);
2248 let kind = hir::GenericParamKind::Type {
2249 default: default.as_ref().map(|x| {
2250 self.lower_ty(x, ImplTraitContext::Disallowed(ImplTraitPosition::Other))
2255 .filter(|attr| self.sess.check_name(attr, sym::rustc_synthetic))
2256 .map(|_| hir::SyntheticTyParamKind::FromAttr)
2260 (hir::ParamName::Plain(param.ident), kind)
2262 GenericParamKind::Const { ref ty, kw_span: _, ref default } => {
2264 .with_anonymous_lifetime_mode(AnonymousLifetimeMode::ReportError, |this| {
2265 this.lower_ty(&ty, ImplTraitContext::disallowed())
2267 let default = default.as_ref().map(|def| self.lower_anon_const(def));
2268 (hir::ParamName::Plain(param.ident), hir::GenericParamKind::Const { ty, default })
2272 let hir_id = self.lower_node_id(param.id);
2273 self.lower_attrs(hir_id, ¶m.attrs);
2277 span: param.ident.span,
2278 pure_wrt_drop: self.sess.contains_name(¶m.attrs, sym::may_dangle),
2279 bounds: self.arena.alloc_from_iter(bounds),
2287 itctx: ImplTraitContext<'_, 'hir>,
2288 ) -> hir::TraitRef<'hir> {
2289 let path = match self.lower_qpath(p.ref_id, &None, &p.path, ParamMode::Explicit, itctx) {
2290 hir::QPath::Resolved(None, path) => path,
2291 qpath => panic!("lower_trait_ref: unexpected QPath `{:?}`", qpath),
2293 hir::TraitRef { path, hir_ref_id: self.lower_node_id(p.ref_id) }
2296 fn lower_poly_trait_ref(
2299 mut itctx: ImplTraitContext<'_, 'hir>,
2300 ) -> hir::PolyTraitRef<'hir> {
2301 let bound_generic_params = self.lower_generic_params(
2302 &p.bound_generic_params,
2303 &NodeMap::default(),
2307 let trait_ref = self.with_in_scope_lifetime_defs(&p.bound_generic_params, |this| {
2308 // Any impl Trait types defined within this scope can capture
2309 // lifetimes bound on this predicate.
2310 let lt_def_names = p.bound_generic_params.iter().filter_map(|param| match param.kind {
2311 GenericParamKind::Lifetime { .. } => Some(hir::LifetimeName::Param(
2312 ParamName::Plain(param.ident.normalize_to_macros_2_0()),
2316 if let ImplTraitContext::TypeAliasesOpaqueTy { ref mut capturable_lifetimes, .. } =
2319 capturable_lifetimes.extend(lt_def_names.clone());
2322 let res = this.lower_trait_ref(&p.trait_ref, itctx.reborrow());
2324 if let ImplTraitContext::TypeAliasesOpaqueTy { ref mut capturable_lifetimes, .. } =
2327 for param in lt_def_names {
2328 capturable_lifetimes.remove(¶m);
2334 hir::PolyTraitRef { bound_generic_params, trait_ref, span: p.span }
2337 fn lower_mt(&mut self, mt: &MutTy, itctx: ImplTraitContext<'_, 'hir>) -> hir::MutTy<'hir> {
2338 hir::MutTy { ty: self.lower_ty(&mt.ty, itctx), mutbl: mt.mutbl }
2341 fn lower_param_bounds(
2343 bounds: &[GenericBound],
2344 itctx: ImplTraitContext<'_, 'hir>,
2345 ) -> hir::GenericBounds<'hir> {
2346 self.arena.alloc_from_iter(self.lower_param_bounds_mut(bounds, itctx))
2349 fn lower_param_bounds_mut<'s>(
2351 bounds: &'s [GenericBound],
2352 mut itctx: ImplTraitContext<'s, 'hir>,
2353 ) -> impl Iterator<Item = hir::GenericBound<'hir>> + Captures<'s> + Captures<'a> {
2354 bounds.iter().map(move |bound| self.lower_param_bound(bound, itctx.reborrow()))
2357 fn lower_block(&mut self, b: &Block, targeted_by_break: bool) -> &'hir hir::Block<'hir> {
2358 self.arena.alloc(self.lower_block_noalloc(b, targeted_by_break))
2361 fn lower_block_noalloc(&mut self, b: &Block, targeted_by_break: bool) -> hir::Block<'hir> {
2362 let (stmts, expr) = match &*b.stmts {
2363 [stmts @ .., Stmt { kind: StmtKind::Expr(e), .. }] => (stmts, Some(&*e)),
2364 stmts => (stmts, None),
2366 let stmts = self.arena.alloc_from_iter(stmts.iter().flat_map(|stmt| self.lower_stmt(stmt)));
2367 let expr = expr.map(|e| self.lower_expr(e));
2368 let rules = self.lower_block_check_mode(&b.rules);
2369 let hir_id = self.lower_node_id(b.id);
2371 hir::Block { hir_id, stmts, expr, rules, span: b.span, targeted_by_break }
2374 /// Lowers a block directly to an expression, presuming that it
2375 /// has no attributes and is not targeted by a `break`.
2376 fn lower_block_expr(&mut self, b: &Block) -> hir::Expr<'hir> {
2377 let block = self.lower_block(b, false);
2378 self.expr_block(block, AttrVec::new())
2381 fn lower_anon_const(&mut self, c: &AnonConst) -> hir::AnonConst {
2382 self.with_new_scopes(|this| hir::AnonConst {
2383 hir_id: this.lower_node_id(c.id),
2384 body: this.lower_const_body(c.value.span, Some(&c.value)),
2388 fn lower_stmt(&mut self, s: &Stmt) -> SmallVec<[hir::Stmt<'hir>; 1]> {
2389 let (hir_id, kind) = match s.kind {
2390 StmtKind::Local(ref l) => {
2391 let l = self.lower_local(l);
2392 let hir_id = self.lower_node_id(s.id);
2393 self.alias_attrs(hir_id, l.hir_id);
2394 return smallvec![hir::Stmt {
2396 kind: hir::StmtKind::Local(self.arena.alloc(l)),
2400 StmtKind::Item(ref it) => {
2401 // Can only use the ID once.
2402 let mut id = Some(s.id);
2409 .map(|id| self.lower_node_id(id))
2410 .unwrap_or_else(|| self.next_id());
2412 hir::Stmt { hir_id, kind: hir::StmtKind::Item(item_id), span: s.span }
2416 StmtKind::Expr(ref e) => {
2417 let e = self.lower_expr(e);
2418 let hir_id = self.lower_node_id(s.id);
2419 self.alias_attrs(hir_id, e.hir_id);
2420 (hir_id, hir::StmtKind::Expr(e))
2422 StmtKind::Semi(ref e) => {
2423 let e = self.lower_expr(e);
2424 let hir_id = self.lower_node_id(s.id);
2425 self.alias_attrs(hir_id, e.hir_id);
2426 (hir_id, hir::StmtKind::Semi(e))
2428 StmtKind::Empty => return smallvec![],
2429 StmtKind::MacCall(..) => panic!("shouldn't exist here"),
2431 smallvec![hir::Stmt { hir_id, kind, span: s.span }]
2434 fn lower_block_check_mode(&mut self, b: &BlockCheckMode) -> hir::BlockCheckMode {
2436 BlockCheckMode::Default => hir::BlockCheckMode::DefaultBlock,
2437 BlockCheckMode::Unsafe(u) => {
2438 hir::BlockCheckMode::UnsafeBlock(self.lower_unsafe_source(u))
2443 fn lower_unsafe_source(&mut self, u: UnsafeSource) -> hir::UnsafeSource {
2445 CompilerGenerated => hir::UnsafeSource::CompilerGenerated,
2446 UserProvided => hir::UnsafeSource::UserProvided,
2450 fn lower_trait_bound_modifier(&mut self, f: TraitBoundModifier) -> hir::TraitBoundModifier {
2452 TraitBoundModifier::None => hir::TraitBoundModifier::None,
2453 TraitBoundModifier::MaybeConst => hir::TraitBoundModifier::MaybeConst,
2455 // `MaybeConstMaybe` will cause an error during AST validation, but we need to pick a
2456 // placeholder for compilation to proceed.
2457 TraitBoundModifier::MaybeConstMaybe | TraitBoundModifier::Maybe => {
2458 hir::TraitBoundModifier::Maybe
2463 // Helper methods for building HIR.
2465 fn stmt(&mut self, span: Span, kind: hir::StmtKind<'hir>) -> hir::Stmt<'hir> {
2466 hir::Stmt { span, kind, hir_id: self.next_id() }
2469 fn stmt_expr(&mut self, span: Span, expr: hir::Expr<'hir>) -> hir::Stmt<'hir> {
2470 self.stmt(span, hir::StmtKind::Expr(self.arena.alloc(expr)))
2475 attrs: Option<&'hir [Attribute]>,
2477 init: Option<&'hir hir::Expr<'hir>>,
2478 pat: &'hir hir::Pat<'hir>,
2479 source: hir::LocalSource,
2480 ) -> hir::Stmt<'hir> {
2481 let hir_id = self.next_id();
2482 if let Some(a) = attrs {
2483 debug_assert!(!a.is_empty());
2484 self.attrs.insert(hir_id, a);
2486 let local = hir::Local { hir_id, init, pat, source, span, ty: None };
2487 self.stmt(span, hir::StmtKind::Local(self.arena.alloc(local)))
2490 fn block_expr(&mut self, expr: &'hir hir::Expr<'hir>) -> &'hir hir::Block<'hir> {
2491 self.block_all(expr.span, &[], Some(expr))
2497 stmts: &'hir [hir::Stmt<'hir>],
2498 expr: Option<&'hir hir::Expr<'hir>>,
2499 ) -> &'hir hir::Block<'hir> {
2500 let blk = hir::Block {
2503 hir_id: self.next_id(),
2504 rules: hir::BlockCheckMode::DefaultBlock,
2506 targeted_by_break: false,
2508 self.arena.alloc(blk)
2511 /// Constructs a `true` or `false` literal pattern.
2512 fn pat_bool(&mut self, span: Span, val: bool) -> &'hir hir::Pat<'hir> {
2513 let expr = self.expr_bool(span, val);
2514 self.pat(span, hir::PatKind::Lit(expr))
2517 fn pat_cf_continue(&mut self, span: Span, pat: &'hir hir::Pat<'hir>) -> &'hir hir::Pat<'hir> {
2518 let field = self.single_pat_field(span, pat);
2519 self.pat_lang_item_variant(span, hir::LangItem::ControlFlowContinue, field)
2522 fn pat_cf_break(&mut self, span: Span, pat: &'hir hir::Pat<'hir>) -> &'hir hir::Pat<'hir> {
2523 let field = self.single_pat_field(span, pat);
2524 self.pat_lang_item_variant(span, hir::LangItem::ControlFlowBreak, field)
2527 fn pat_some(&mut self, span: Span, pat: &'hir hir::Pat<'hir>) -> &'hir hir::Pat<'hir> {
2528 let field = self.single_pat_field(span, pat);
2529 self.pat_lang_item_variant(span, hir::LangItem::OptionSome, field)
2532 fn pat_none(&mut self, span: Span) -> &'hir hir::Pat<'hir> {
2533 self.pat_lang_item_variant(span, hir::LangItem::OptionNone, &[])
2536 fn single_pat_field(
2539 pat: &'hir hir::Pat<'hir>,
2540 ) -> &'hir [hir::PatField<'hir>] {
2541 let field = hir::PatField {
2542 hir_id: self.next_id(),
2543 ident: Ident::new(sym::integer(0), span),
2544 is_shorthand: false,
2548 arena_vec![self; field]
2551 fn pat_lang_item_variant(
2554 lang_item: hir::LangItem,
2555 fields: &'hir [hir::PatField<'hir>],
2556 ) -> &'hir hir::Pat<'hir> {
2557 let qpath = hir::QPath::LangItem(lang_item, span);
2558 self.pat(span, hir::PatKind::Struct(qpath, fields, false))
2561 fn pat_ident(&mut self, span: Span, ident: Ident) -> (&'hir hir::Pat<'hir>, hir::HirId) {
2562 self.pat_ident_binding_mode(span, ident, hir::BindingAnnotation::Unannotated)
2565 fn pat_ident_mut(&mut self, span: Span, ident: Ident) -> (hir::Pat<'hir>, hir::HirId) {
2566 self.pat_ident_binding_mode_mut(span, ident, hir::BindingAnnotation::Unannotated)
2569 fn pat_ident_binding_mode(
2573 bm: hir::BindingAnnotation,
2574 ) -> (&'hir hir::Pat<'hir>, hir::HirId) {
2575 let (pat, hir_id) = self.pat_ident_binding_mode_mut(span, ident, bm);
2576 (self.arena.alloc(pat), hir_id)
2579 fn pat_ident_binding_mode_mut(
2583 bm: hir::BindingAnnotation,
2584 ) -> (hir::Pat<'hir>, hir::HirId) {
2585 let hir_id = self.next_id();
2590 kind: hir::PatKind::Binding(bm, hir_id, ident.with_span_pos(span), None),
2592 default_binding_modes: true,
2598 fn pat_wild(&mut self, span: Span) -> &'hir hir::Pat<'hir> {
2599 self.pat(span, hir::PatKind::Wild)
2602 fn pat(&mut self, span: Span, kind: hir::PatKind<'hir>) -> &'hir hir::Pat<'hir> {
2603 self.arena.alloc(hir::Pat {
2604 hir_id: self.next_id(),
2607 default_binding_modes: true,
2611 fn pat_without_dbm(&mut self, span: Span, kind: hir::PatKind<'hir>) -> hir::Pat<'hir> {
2612 hir::Pat { hir_id: self.next_id(), kind, span, default_binding_modes: false }
2617 mut hir_id: hir::HirId,
2619 qpath: hir::QPath<'hir>,
2620 ) -> hir::Ty<'hir> {
2621 let kind = match qpath {
2622 hir::QPath::Resolved(None, path) => {
2623 // Turn trait object paths into `TyKind::TraitObject` instead.
2625 Res::Def(DefKind::Trait | DefKind::TraitAlias, _) => {
2626 let principal = hir::PolyTraitRef {
2627 bound_generic_params: &[],
2628 trait_ref: hir::TraitRef { path, hir_ref_id: hir_id },
2632 // The original ID is taken by the `PolyTraitRef`,
2633 // so the `Ty` itself needs a different one.
2634 hir_id = self.next_id();
2635 hir::TyKind::TraitObject(
2636 arena_vec![self; principal],
2637 self.elided_dyn_bound(span),
2638 TraitObjectSyntax::None,
2641 _ => hir::TyKind::Path(hir::QPath::Resolved(None, path)),
2644 _ => hir::TyKind::Path(qpath),
2647 hir::Ty { hir_id, kind, span }
2650 /// Invoked to create the lifetime argument for a type `&T`
2651 /// with no explicit lifetime.
2652 fn elided_ref_lifetime(&mut self, span: Span) -> hir::Lifetime {
2653 match self.anonymous_lifetime_mode {
2654 // Intercept when we are in an impl header or async fn and introduce an in-band
2656 // Hence `impl Foo for &u32` becomes `impl<'f> Foo for &'f u32` for some fresh
2658 AnonymousLifetimeMode::CreateParameter => {
2659 let fresh_name = self.collect_fresh_in_band_lifetime(span);
2661 hir_id: self.next_id(),
2663 name: hir::LifetimeName::Param(fresh_name),
2667 AnonymousLifetimeMode::ReportError => self.new_error_lifetime(None, span),
2669 AnonymousLifetimeMode::PassThrough => self.new_implicit_lifetime(span),
2673 /// Report an error on illegal use of `'_` or a `&T` with no explicit lifetime;
2674 /// return a "error lifetime".
2675 fn new_error_lifetime(&mut self, id: Option<NodeId>, span: Span) -> hir::Lifetime {
2676 let (id, msg, label) = match id {
2677 Some(id) => (id, "`'_` cannot be used here", "`'_` is a reserved lifetime name"),
2680 self.resolver.next_node_id(),
2681 "`&` without an explicit lifetime name cannot be used here",
2682 "explicit lifetime name needed here",
2686 let mut err = struct_span_err!(self.sess, span, E0637, "{}", msg,);
2687 err.span_label(span, label);
2690 self.new_named_lifetime(id, span, hir::LifetimeName::Error)
2693 /// Invoked to create the lifetime argument(s) for a path like
2694 /// `std::cell::Ref<T>`; note that implicit lifetimes in these
2695 /// sorts of cases are deprecated. This may therefore report a warning or an
2696 /// error, depending on the mode.
2697 fn elided_path_lifetimes<'s>(
2701 ) -> impl Iterator<Item = hir::Lifetime> + Captures<'a> + Captures<'s> + Captures<'hir> {
2702 (0..count).map(move |_| self.elided_path_lifetime(span))
2705 fn elided_path_lifetime(&mut self, span: Span) -> hir::Lifetime {
2706 match self.anonymous_lifetime_mode {
2707 AnonymousLifetimeMode::CreateParameter => {
2708 // We should have emitted E0726 when processing this path above
2710 .delay_span_bug(span, "expected 'implicit elided lifetime not allowed' error");
2711 let id = self.resolver.next_node_id();
2712 self.new_named_lifetime(id, span, hir::LifetimeName::Error)
2714 // `PassThrough` is the normal case.
2715 // `new_error_lifetime`, which would usually be used in the case of `ReportError`,
2716 // is unsuitable here, as these can occur from missing lifetime parameters in a
2717 // `PathSegment`, for which there is no associated `'_` or `&T` with no explicit
2718 // lifetime. Instead, we simply create an implicit lifetime, which will be checked
2719 // later, at which point a suitable error will be emitted.
2720 AnonymousLifetimeMode::PassThrough | AnonymousLifetimeMode::ReportError => {
2721 self.new_implicit_lifetime(span)
2726 /// Invoked to create the lifetime argument(s) for an elided trait object
2727 /// bound, like the bound in `Box<dyn Debug>`. This method is not invoked
2728 /// when the bound is written, even if it is written with `'_` like in
2729 /// `Box<dyn Debug + '_>`. In those cases, `lower_lifetime` is invoked.
2730 fn elided_dyn_bound(&mut self, span: Span) -> hir::Lifetime {
2731 match self.anonymous_lifetime_mode {
2732 // NB. We intentionally ignore the create-parameter mode here.
2733 // and instead "pass through" to resolve-lifetimes, which will apply
2734 // the object-lifetime-defaulting rules. Elided object lifetime defaults
2735 // do not act like other elided lifetimes. In other words, given this:
2737 // impl Foo for Box<dyn Debug>
2739 // we do not introduce a fresh `'_` to serve as the bound, but instead
2740 // ultimately translate to the equivalent of:
2742 // impl Foo for Box<dyn Debug + 'static>
2744 // `resolve_lifetime` has the code to make that happen.
2745 AnonymousLifetimeMode::CreateParameter => {}
2747 AnonymousLifetimeMode::ReportError => {
2748 // ReportError applies to explicit use of `'_`.
2751 // This is the normal case.
2752 AnonymousLifetimeMode::PassThrough => {}
2755 let r = hir::Lifetime {
2756 hir_id: self.next_id(),
2758 name: hir::LifetimeName::ImplicitObjectLifetimeDefault,
2760 debug!("elided_dyn_bound: r={:?}", r);
2764 fn new_implicit_lifetime(&mut self, span: Span) -> hir::Lifetime {
2765 hir::Lifetime { hir_id: self.next_id(), span, name: hir::LifetimeName::Implicit }
2768 fn maybe_lint_bare_trait(&mut self, span: Span, id: NodeId, is_global: bool) {
2769 // FIXME(davidtwco): This is a hack to detect macros which produce spans of the
2770 // call site which do not have a macro backtrace. See #61963.
2771 let is_macro_callsite = self
2774 .span_to_snippet(span)
2775 .map(|snippet| snippet.starts_with("#["))
2777 if !is_macro_callsite {
2778 if span.edition() < Edition::Edition2021 {
2779 self.resolver.lint_buffer().buffer_lint_with_diagnostic(
2783 "trait objects without an explicit `dyn` are deprecated",
2784 BuiltinLintDiagnostics::BareTraitObject(span, is_global),
2787 let msg = "trait objects must include the `dyn` keyword";
2788 let label = "add `dyn` keyword before this trait";
2789 let mut err = struct_span_err!(self.sess, span, E0782, "{}", msg,);
2790 err.span_suggestion_verbose(
2791 span.shrink_to_lo(),
2793 String::from("dyn "),
2794 Applicability::MachineApplicable,
2801 fn maybe_lint_missing_abi(&mut self, span: Span, id: NodeId, default: Abi) {
2802 // FIXME(davidtwco): This is a hack to detect macros which produce spans of the
2803 // call site which do not have a macro backtrace. See #61963.
2804 let is_macro_callsite = self
2807 .span_to_snippet(span)
2808 .map(|snippet| snippet.starts_with("#["))
2810 if !is_macro_callsite {
2811 self.resolver.lint_buffer().buffer_lint_with_diagnostic(
2815 "extern declarations without an explicit ABI are deprecated",
2816 BuiltinLintDiagnostics::MissingAbi(span, default),
2822 fn body_ids(bodies: &BTreeMap<hir::BodyId, hir::Body<'_>>) -> Vec<hir::BodyId> {
2823 // Sorting by span ensures that we get things in order within a
2824 // file, and also puts the files in a sensible order.
2825 let mut body_ids: Vec<_> = bodies.keys().cloned().collect();
2826 body_ids.sort_by_key(|b| bodies[b].value.span);
2830 /// Helper struct for delayed construction of GenericArgs.
2831 struct GenericArgsCtor<'hir> {
2832 args: SmallVec<[hir::GenericArg<'hir>; 4]>,
2833 bindings: &'hir [hir::TypeBinding<'hir>],
2834 parenthesized: bool,
2838 impl<'hir> GenericArgsCtor<'hir> {
2839 fn is_empty(&self) -> bool {
2840 self.args.is_empty() && self.bindings.is_empty() && !self.parenthesized
2843 fn into_generic_args(self, arena: &'hir Arena<'hir>) -> hir::GenericArgs<'hir> {
2845 args: arena.alloc_from_iter(self.args),
2846 bindings: self.bindings,
2847 parenthesized: self.parenthesized,
2848 span_ext: self.span,