1 // ignore-tidy-filelength
3 //! Lowers the AST to the HIR.
5 //! Since the AST and HIR are fairly similar, this is mostly a simple procedure,
6 //! much like a fold. Where lowering involves a bit more work things get more
7 //! interesting and there are some invariants you should know about. These mostly
8 //! concern spans and IDs.
10 //! Spans are assigned to AST nodes during parsing and then are modified during
11 //! expansion to indicate the origin of a node and the process it went through
12 //! being expanded. IDs are assigned to AST nodes just before lowering.
14 //! For the simpler lowering steps, IDs and spans should be preserved. Unlike
15 //! expansion we do not preserve the process of lowering in the spans, so spans
16 //! should not be modified here. When creating a new node (as opposed to
17 //! 'folding' an existing one), then you create a new ID using `next_id()`.
19 //! You must ensure that IDs are unique. That means that you should only use the
20 //! ID from an AST node in a single HIR node (you can assume that AST node-IDs
21 //! are unique). Every new node must have a unique ID. Avoid cloning HIR nodes.
22 //! If you do, you must then set the new node's ID to a fresh one.
24 //! Spans are used for error messages and for tools to map semantics back to
25 //! source code. It is therefore not as important with spans as IDs to be strict
26 //! about use (you can't break the compiler by screwing up a span). Obviously, a
27 //! HIR node can only have a single span. But multiple nodes can have the same
28 //! span and spans don't need to be kept in order, etc. Where code is preserved
29 //! by lowering, it should have the same span as in the AST. Where HIR nodes are
30 //! new it is probably best to give a span for the whole AST node being lowered.
31 //! All nodes should have real spans, don't use dummy spans. Tools are likely to
32 //! get confused if the spans from leaf AST nodes occur in multiple places
33 //! in the HIR, especially for multiple identifiers.
38 use crate::dep_graph::DepGraph;
39 use crate::hir::{self, ParamName};
40 use crate::hir::HirVec;
41 use crate::hir::map::{DefKey, DefPathData, Definitions};
42 use crate::hir::def_id::{DefId, DefIndex, CRATE_DEF_INDEX};
43 use crate::hir::def::{Namespace, Res, DefKind, PartialRes, PerNS};
44 use crate::hir::{GenericArg, ConstArg};
45 use crate::hir::ptr::P;
46 use crate::lint::builtin::{self, PARENTHESIZED_PARAMS_IN_TYPES_AND_MODULES,
47 ELIDED_LIFETIMES_IN_PATHS};
48 use crate::middle::cstore::CrateStore;
49 use crate::session::Session;
50 use crate::session::config::nightly_options;
51 use crate::util::common::FN_OUTPUT_NAME;
52 use crate::util::nodemap::{DefIdMap, NodeMap};
53 use errors::Applicability;
54 use rustc_data_structures::fx::FxHashSet;
55 use rustc_data_structures::indexed_vec::IndexVec;
56 use rustc_data_structures::thin_vec::ThinVec;
57 use rustc_data_structures::sync::Lrc;
59 use std::collections::BTreeMap;
61 use smallvec::SmallVec;
64 use syntax::ptr::P as AstP;
67 use syntax::ext::base::SpecialDerives;
68 use syntax::ext::hygiene::ExpnId;
69 use syntax::print::pprust;
70 use syntax::source_map::{respan, ExpnInfo, ExpnKind, DesugaringKind, Spanned};
71 use syntax::symbol::{kw, sym, Symbol};
72 use syntax::tokenstream::{TokenStream, TokenTree};
73 use syntax::parse::token::{self, Token};
74 use syntax::visit::{self, Visitor};
75 use syntax_pos::{DUMMY_SP, Span};
77 const HIR_ID_COUNTER_LOCKED: u32 = 0xFFFFFFFF;
79 pub struct LoweringContext<'a> {
80 crate_root: Option<Symbol>,
82 /// Used to assign ids to HIR nodes that do not directly correspond to an AST node.
85 cstore: &'a dyn CrateStore,
87 resolver: &'a mut dyn Resolver,
89 /// The items being lowered are collected here.
90 items: BTreeMap<hir::HirId, hir::Item>,
92 trait_items: BTreeMap<hir::TraitItemId, hir::TraitItem>,
93 impl_items: BTreeMap<hir::ImplItemId, hir::ImplItem>,
94 bodies: BTreeMap<hir::BodyId, hir::Body>,
95 exported_macros: Vec<hir::MacroDef>,
96 non_exported_macro_attrs: Vec<ast::Attribute>,
98 trait_impls: BTreeMap<DefId, Vec<hir::HirId>>,
100 modules: BTreeMap<NodeId, hir::ModuleItems>,
102 generator_kind: Option<hir::GeneratorKind>,
104 /// Used to get the current `fn`'s def span to point to when using `await`
105 /// outside of an `async fn`.
106 current_item: Option<Span>,
108 catch_scopes: Vec<NodeId>,
109 loop_scopes: Vec<NodeId>,
110 is_in_loop_condition: bool,
111 is_in_trait_impl: bool,
112 is_in_dyn_type: bool,
114 /// What to do when we encounter either an "anonymous lifetime
115 /// reference". The term "anonymous" is meant to encompass both
116 /// `'_` lifetimes as well as fully elided cases where nothing is
117 /// written at all (e.g., `&T` or `std::cell::Ref<T>`).
118 anonymous_lifetime_mode: AnonymousLifetimeMode,
120 /// Used to create lifetime definitions from in-band lifetime usages.
121 /// e.g., `fn foo(x: &'x u8) -> &'x u8` to `fn foo<'x>(x: &'x u8) -> &'x u8`
122 /// When a named lifetime is encountered in a function or impl header and
123 /// has not been defined
124 /// (i.e., it doesn't appear in the in_scope_lifetimes list), it is added
125 /// to this list. The results of this list are then added to the list of
126 /// lifetime definitions in the corresponding impl or function generics.
127 lifetimes_to_define: Vec<(Span, ParamName)>,
129 /// Whether or not in-band lifetimes are being collected. This is used to
130 /// indicate whether or not we're in a place where new lifetimes will result
131 /// in in-band lifetime definitions, such a function or an impl header,
132 /// including implicit lifetimes from `impl_header_lifetime_elision`.
133 is_collecting_in_band_lifetimes: bool,
135 /// Currently in-scope lifetimes defined in impl headers, fn headers, or HRTB.
136 /// When `is_collectin_in_band_lifetimes` is true, each lifetime is checked
137 /// against this list to see if it is already in-scope, or if a definition
138 /// needs to be created for it.
140 /// We always store a `modern()` version of the param-name in this
142 in_scope_lifetimes: Vec<ParamName>,
144 current_module: NodeId,
146 type_def_lifetime_params: DefIdMap<usize>,
148 current_hir_id_owner: Vec<(DefIndex, u32)>,
149 item_local_id_counters: NodeMap<u32>,
150 node_id_to_hir_id: IndexVec<NodeId, hir::HirId>,
152 allow_try_trait: Option<Lrc<[Symbol]>>,
153 allow_gen_future: Option<Lrc<[Symbol]>>,
157 /// Obtain resolution for a `NodeId` with a single resolution.
158 fn get_partial_res(&mut self, id: NodeId) -> Option<PartialRes>;
160 /// Obtain per-namespace resolutions for `use` statement with the given `NoedId`.
161 fn get_import_res(&mut self, id: NodeId) -> PerNS<Option<Res<NodeId>>>;
163 /// Obtain resolution for a label with the given `NodeId`.
164 fn get_label_res(&mut self, id: NodeId) -> Option<NodeId>;
166 /// We must keep the set of definitions up to date as we add nodes that weren't in the AST.
167 /// This should only return `None` during testing.
168 fn definitions(&mut self) -> &mut Definitions;
170 /// Given suffix `["b", "c", "d"]`, creates an AST path for `[::crate_root]::b::c::d` and
171 /// resolves it based on `is_value`.
175 crate_root: Option<Symbol>,
176 components: &[Symbol],
178 ) -> (ast::Path, Res<NodeId>);
180 fn has_derives(&self, node_id: NodeId, derives: SpecialDerives) -> bool;
183 /// Context of `impl Trait` in code, which determines whether it is allowed in an HIR subtree,
184 /// and if so, what meaning it has.
186 enum ImplTraitContext<'a> {
187 /// Treat `impl Trait` as shorthand for a new universal generic parameter.
188 /// Example: `fn foo(x: impl Debug)`, where `impl Debug` is conceptually
189 /// equivalent to a fresh universal parameter like `fn foo<T: Debug>(x: T)`.
191 /// Newly generated parameters should be inserted into the given `Vec`.
192 Universal(&'a mut Vec<hir::GenericParam>),
194 /// Treat `impl Trait` as shorthand for a new opaque type.
195 /// Example: `fn foo() -> impl Debug`, where `impl Debug` is conceptually
196 /// equivalent to a new opaque type like `type T = impl Debug; fn foo() -> T`.
198 /// We optionally store a `DefId` for the parent item here so we can look up necessary
199 /// information later. It is `None` when no information about the context should be stored
200 /// (e.g., for consts and statics).
201 OpaqueTy(Option<DefId> /* fn def-ID */),
203 /// `impl Trait` is not accepted in this position.
204 Disallowed(ImplTraitPosition),
207 /// Position in which `impl Trait` is disallowed.
208 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
209 enum ImplTraitPosition {
210 /// Disallowed in `let` / `const` / `static` bindings.
213 /// All other posiitons.
217 impl<'a> ImplTraitContext<'a> {
219 fn disallowed() -> Self {
220 ImplTraitContext::Disallowed(ImplTraitPosition::Other)
223 fn reborrow(&'b mut self) -> ImplTraitContext<'b> {
224 use self::ImplTraitContext::*;
226 Universal(params) => Universal(params),
227 OpaqueTy(fn_def_id) => OpaqueTy(*fn_def_id),
228 Disallowed(pos) => Disallowed(*pos),
235 cstore: &dyn CrateStore,
236 dep_graph: &DepGraph,
238 resolver: &mut dyn Resolver,
240 // We're constructing the HIR here; we don't care what we will
241 // read, since we haven't even constructed the *input* to
243 dep_graph.assert_ignored();
246 crate_root: sess.parse_sess.injected_crate_name.try_get().copied(),
250 items: BTreeMap::new(),
251 trait_items: BTreeMap::new(),
252 impl_items: BTreeMap::new(),
253 bodies: BTreeMap::new(),
254 trait_impls: BTreeMap::new(),
255 modules: BTreeMap::new(),
256 exported_macros: Vec::new(),
257 non_exported_macro_attrs: Vec::new(),
258 catch_scopes: Vec::new(),
259 loop_scopes: Vec::new(),
260 is_in_loop_condition: false,
261 is_in_trait_impl: false,
262 is_in_dyn_type: false,
263 anonymous_lifetime_mode: AnonymousLifetimeMode::PassThrough,
264 type_def_lifetime_params: Default::default(),
265 current_module: CRATE_NODE_ID,
266 current_hir_id_owner: vec![(CRATE_DEF_INDEX, 0)],
267 item_local_id_counters: Default::default(),
268 node_id_to_hir_id: IndexVec::new(),
269 generator_kind: None,
271 lifetimes_to_define: Vec::new(),
272 is_collecting_in_band_lifetimes: false,
273 in_scope_lifetimes: Vec::new(),
274 allow_try_trait: Some([sym::try_trait][..].into()),
275 allow_gen_future: Some([sym::gen_future][..].into()),
279 #[derive(Copy, Clone, PartialEq)]
281 /// Any path in a type context.
283 /// Path in a type definition, where the anonymous lifetime `'_` is not allowed.
285 /// The `module::Type` in `module::Type::method` in an expression.
289 enum ParenthesizedGenericArgs {
295 /// What to do when we encounter an **anonymous** lifetime
296 /// reference. Anonymous lifetime references come in two flavors. You
297 /// have implicit, or fully elided, references to lifetimes, like the
298 /// one in `&T` or `Ref<T>`, and you have `'_` lifetimes, like `&'_ T`
299 /// or `Ref<'_, T>`. These often behave the same, but not always:
301 /// - certain usages of implicit references are deprecated, like
302 /// `Ref<T>`, and we sometimes just give hard errors in those cases
304 /// - for object bounds there is a difference: `Box<dyn Foo>` is not
305 /// the same as `Box<dyn Foo + '_>`.
307 /// We describe the effects of the various modes in terms of three cases:
309 /// - **Modern** -- includes all uses of `'_`, but also the lifetime arg
310 /// of a `&` (e.g., the missing lifetime in something like `&T`)
311 /// - **Dyn Bound** -- if you have something like `Box<dyn Foo>`,
312 /// there is an elided lifetime bound (`Box<dyn Foo + 'X>`). These
313 /// elided bounds follow special rules. Note that this only covers
314 /// cases where *nothing* is written; the `'_` in `Box<dyn Foo +
315 /// '_>` is a case of "modern" elision.
316 /// - **Deprecated** -- this coverse cases like `Ref<T>`, where the lifetime
317 /// parameter to ref is completely elided. `Ref<'_, T>` would be the modern,
318 /// non-deprecated equivalent.
320 /// Currently, the handling of lifetime elision is somewhat spread out
321 /// between HIR lowering and -- as described below -- the
322 /// `resolve_lifetime` module. Often we "fallthrough" to that code by generating
323 /// an "elided" or "underscore" lifetime name. In the future, we probably want to move
324 /// everything into HIR lowering.
325 #[derive(Copy, Clone)]
326 enum AnonymousLifetimeMode {
327 /// For **Modern** cases, create a new anonymous region parameter
328 /// and reference that.
330 /// For **Dyn Bound** cases, pass responsibility to
331 /// `resolve_lifetime` code.
333 /// For **Deprecated** cases, report an error.
336 /// Give a hard error when either `&` or `'_` is written. Used to
337 /// rule out things like `where T: Foo<'_>`. Does not imply an
338 /// error on default object bounds (e.g., `Box<dyn Foo>`).
341 /// Pass responsibility to `resolve_lifetime` code for all cases.
344 /// Used in the return types of `async fn` where there exists
345 /// exactly one argument-position elided lifetime.
347 /// In `async fn`, we lower the arguments types using the `CreateParameter`
348 /// mode, meaning that non-`dyn` elided lifetimes are assigned a fresh name.
349 /// If any corresponding elided lifetimes appear in the output, we need to
350 /// replace them with references to the fresh name assigned to the corresponding
351 /// elided lifetime in the arguments.
353 /// For **Modern cases**, replace the anonymous parameter with a
354 /// reference to a specific freshly-named lifetime that was
355 /// introduced in argument
357 /// For **Dyn Bound** cases, pass responsibility to
358 /// `resole_lifetime` code.
359 Replace(LtReplacement),
362 /// The type of elided lifetime replacement to perform on `async fn` return types.
363 #[derive(Copy, Clone)]
365 /// Fresh name introduced by the single non-dyn elided lifetime
366 /// in the arguments of the async fn.
369 /// There is no single non-dyn elided lifetime because no lifetimes
370 /// appeared in the arguments.
373 /// There is no single non-dyn elided lifetime because multiple
374 /// lifetimes appeared in the arguments.
378 /// Calculates the `LtReplacement` to use for elided lifetimes in the return
379 /// type based on the fresh elided lifetimes introduced in argument position.
380 fn get_elided_lt_replacement(arg_position_lifetimes: &[(Span, ParamName)]) -> LtReplacement {
381 match arg_position_lifetimes {
382 [] => LtReplacement::NoLifetimes,
383 [(_span, param)] => LtReplacement::Some(*param),
384 _ => LtReplacement::MultipleLifetimes,
388 struct ImplTraitTypeIdVisitor<'a> { ids: &'a mut SmallVec<[NodeId; 1]> }
390 impl<'a, 'b> Visitor<'a> for ImplTraitTypeIdVisitor<'b> {
391 fn visit_ty(&mut self, ty: &'a Ty) {
397 TyKind::ImplTrait(id, _) => self.ids.push(id),
400 visit::walk_ty(self, ty);
403 fn visit_path_segment(
406 path_segment: &'v PathSegment,
408 if let Some(ref p) = path_segment.args {
409 if let GenericArgs::Parenthesized(_) = **p {
413 visit::walk_path_segment(self, path_span, path_segment)
417 impl<'a> LoweringContext<'a> {
418 fn lower_crate(mut self, c: &Crate) -> hir::Crate {
419 /// Full-crate AST visitor that inserts into a fresh
420 /// `LoweringContext` any information that may be
421 /// needed from arbitrary locations in the crate,
422 /// e.g., the number of lifetime generic parameters
423 /// declared for every type and trait definition.
424 struct MiscCollector<'tcx, 'interner> {
425 lctx: &'tcx mut LoweringContext<'interner>,
426 hir_id_owner: Option<NodeId>,
429 impl MiscCollector<'_, '_> {
430 fn allocate_use_tree_hir_id_counters(
436 UseTreeKind::Simple(_, id1, id2) => {
437 for &id in &[id1, id2] {
438 self.lctx.resolver.definitions().create_def_with_parent(
445 self.lctx.allocate_hir_id_counter(id);
448 UseTreeKind::Glob => (),
449 UseTreeKind::Nested(ref trees) => {
450 for &(ref use_tree, id) in trees {
451 let hir_id = self.lctx.allocate_hir_id_counter(id);
452 self.allocate_use_tree_hir_id_counters(use_tree, hir_id.owner);
458 fn with_hir_id_owner<F, T>(&mut self, owner: Option<NodeId>, f: F) -> T
460 F: FnOnce(&mut Self) -> T,
462 let old = mem::replace(&mut self.hir_id_owner, owner);
464 self.hir_id_owner = old;
469 impl<'tcx, 'interner> Visitor<'tcx> for MiscCollector<'tcx, 'interner> {
470 fn visit_pat(&mut self, p: &'tcx Pat) {
472 // Doesn't generate a HIR node
473 PatKind::Paren(..) | PatKind::Rest => {},
475 if let Some(owner) = self.hir_id_owner {
476 self.lctx.lower_node_id_with_owner(p.id, owner);
481 visit::walk_pat(self, p)
484 fn visit_item(&mut self, item: &'tcx Item) {
485 let hir_id = self.lctx.allocate_hir_id_counter(item.id);
488 ItemKind::Struct(_, ref generics)
489 | ItemKind::Union(_, ref generics)
490 | ItemKind::Enum(_, ref generics)
491 | ItemKind::TyAlias(_, ref generics)
492 | ItemKind::OpaqueTy(_, ref generics)
493 | ItemKind::Trait(_, _, ref generics, ..) => {
494 let def_id = self.lctx.resolver.definitions().local_def_id(item.id);
498 .filter(|param| match param.kind {
499 ast::GenericParamKind::Lifetime { .. } => true,
503 self.lctx.type_def_lifetime_params.insert(def_id, count);
505 ItemKind::Use(ref use_tree) => {
506 self.allocate_use_tree_hir_id_counters(use_tree, hir_id.owner);
511 self.with_hir_id_owner(Some(item.id), |this| {
512 visit::walk_item(this, item);
516 fn visit_trait_item(&mut self, item: &'tcx TraitItem) {
517 self.lctx.allocate_hir_id_counter(item.id);
520 TraitItemKind::Method(_, None) => {
521 // Ignore patterns in trait methods without bodies
522 self.with_hir_id_owner(None, |this| {
523 visit::walk_trait_item(this, item)
526 _ => self.with_hir_id_owner(Some(item.id), |this| {
527 visit::walk_trait_item(this, item);
532 fn visit_impl_item(&mut self, item: &'tcx ImplItem) {
533 self.lctx.allocate_hir_id_counter(item.id);
534 self.with_hir_id_owner(Some(item.id), |this| {
535 visit::walk_impl_item(this, item);
539 fn visit_foreign_item(&mut self, i: &'tcx ForeignItem) {
540 // Ignore patterns in foreign items
541 self.with_hir_id_owner(None, |this| {
542 visit::walk_foreign_item(this, i)
546 fn visit_ty(&mut self, t: &'tcx Ty) {
548 // Mirrors the case in visit::walk_ty
549 TyKind::BareFn(ref f) => {
555 // Mirrors visit::walk_fn_decl
556 for argument in &f.decl.inputs {
557 // We don't lower the ids of argument patterns
558 self.with_hir_id_owner(None, |this| {
559 this.visit_pat(&argument.pat);
561 self.visit_ty(&argument.ty)
563 self.visit_fn_ret_ty(&f.decl.output)
565 _ => visit::walk_ty(self, t),
570 self.lower_node_id(CRATE_NODE_ID);
571 debug_assert!(self.node_id_to_hir_id[CRATE_NODE_ID] == hir::CRATE_HIR_ID);
573 visit::walk_crate(&mut MiscCollector { lctx: &mut self, hir_id_owner: None }, c);
574 visit::walk_crate(&mut item::ItemLowerer { lctx: &mut self }, c);
576 let module = self.lower_mod(&c.module);
577 let attrs = self.lower_attrs(&c.attrs);
578 let body_ids = body_ids(&self.bodies);
582 .init_node_id_to_hir_id_mapping(self.node_id_to_hir_id);
588 exported_macros: hir::HirVec::from(self.exported_macros),
589 non_exported_macro_attrs: hir::HirVec::from(self.non_exported_macro_attrs),
591 trait_items: self.trait_items,
592 impl_items: self.impl_items,
595 trait_impls: self.trait_impls,
596 modules: self.modules,
600 fn insert_item(&mut self, item: hir::Item) {
601 let id = item.hir_id;
602 // FIXME: Use `debug_asset-rt`.
603 assert_eq!(id.local_id, hir::ItemLocalId::from_u32(0));
604 self.items.insert(id, item);
605 self.modules.get_mut(&self.current_module).unwrap().items.insert(id);
608 fn allocate_hir_id_counter(&mut self, owner: NodeId) -> hir::HirId {
609 // Set up the counter if needed.
610 self.item_local_id_counters.entry(owner).or_insert(0);
611 // Always allocate the first `HirId` for the owner itself.
612 let lowered = self.lower_node_id_with_owner(owner, owner);
613 debug_assert_eq!(lowered.local_id.as_u32(), 0);
617 fn lower_node_id_generic<F>(&mut self, ast_node_id: NodeId, alloc_hir_id: F) -> hir::HirId
619 F: FnOnce(&mut Self) -> hir::HirId,
621 if ast_node_id == DUMMY_NODE_ID {
622 return hir::DUMMY_HIR_ID;
625 let min_size = ast_node_id.as_usize() + 1;
627 if min_size > self.node_id_to_hir_id.len() {
628 self.node_id_to_hir_id.resize(min_size, hir::DUMMY_HIR_ID);
631 let existing_hir_id = self.node_id_to_hir_id[ast_node_id];
633 if existing_hir_id == hir::DUMMY_HIR_ID {
634 // Generate a new `HirId`.
635 let hir_id = alloc_hir_id(self);
636 self.node_id_to_hir_id[ast_node_id] = hir_id;
644 fn with_hir_id_owner<F, T>(&mut self, owner: NodeId, f: F) -> T
646 F: FnOnce(&mut Self) -> T,
648 let counter = self.item_local_id_counters
649 .insert(owner, HIR_ID_COUNTER_LOCKED)
650 .unwrap_or_else(|| panic!("no `item_local_id_counters` entry for {:?}", owner));
651 let def_index = self.resolver.definitions().opt_def_index(owner).unwrap();
652 self.current_hir_id_owner.push((def_index, counter));
654 let (new_def_index, new_counter) = self.current_hir_id_owner.pop().unwrap();
656 debug_assert!(def_index == new_def_index);
657 debug_assert!(new_counter >= counter);
659 let prev = self.item_local_id_counters
660 .insert(owner, new_counter)
662 debug_assert!(prev == HIR_ID_COUNTER_LOCKED);
666 /// This method allocates a new `HirId` for the given `NodeId` and stores it in
667 /// the `LoweringContext`'s `NodeId => HirId` map.
668 /// Take care not to call this method if the resulting `HirId` is then not
669 /// actually used in the HIR, as that would trigger an assertion in the
670 /// `HirIdValidator` later on, which makes sure that all `NodeId`s got mapped
671 /// properly. Calling the method twice with the same `NodeId` is fine though.
672 fn lower_node_id(&mut self, ast_node_id: NodeId) -> hir::HirId {
673 self.lower_node_id_generic(ast_node_id, |this| {
674 let &mut (def_index, ref mut local_id_counter) =
675 this.current_hir_id_owner.last_mut().unwrap();
676 let local_id = *local_id_counter;
677 *local_id_counter += 1;
680 local_id: hir::ItemLocalId::from_u32(local_id),
685 fn lower_node_id_with_owner(&mut self, ast_node_id: NodeId, owner: NodeId) -> hir::HirId {
686 self.lower_node_id_generic(ast_node_id, |this| {
687 let local_id_counter = this
688 .item_local_id_counters
690 .expect("called `lower_node_id_with_owner` before `allocate_hir_id_counter`");
691 let local_id = *local_id_counter;
693 // We want to be sure not to modify the counter in the map while it
694 // is also on the stack. Otherwise we'll get lost updates when writing
695 // back from the stack to the map.
696 debug_assert!(local_id != HIR_ID_COUNTER_LOCKED);
698 *local_id_counter += 1;
702 .opt_def_index(owner)
703 .expect("you forgot to call `create_def_with_parent` or are lowering node-IDs \
704 that do not belong to the current owner");
708 local_id: hir::ItemLocalId::from_u32(local_id),
713 fn next_id(&mut self) -> hir::HirId {
714 self.lower_node_id(self.sess.next_node_id())
717 fn lower_res(&mut self, res: Res<NodeId>) -> Res {
719 self.lower_node_id_generic(id, |_| {
720 panic!("expected node_id to be lowered already for res {:#?}", res)
725 fn expect_full_res(&mut self, id: NodeId) -> Res<NodeId> {
726 self.resolver.get_partial_res(id).map_or(Res::Err, |pr| {
727 if pr.unresolved_segments() != 0 {
728 bug!("path not fully resolved: {:?}", pr);
734 fn expect_full_res_from_use(&mut self, id: NodeId) -> impl Iterator<Item = Res<NodeId>> {
735 self.resolver.get_import_res(id).present_items()
738 fn diagnostic(&self) -> &errors::Handler {
739 self.sess.diagnostic()
742 /// Reuses the span but adds information like the kind of the desugaring and features that are
743 /// allowed inside this span.
744 fn mark_span_with_reason(
746 reason: DesugaringKind,
748 allow_internal_unstable: Option<Lrc<[Symbol]>>,
750 span.fresh_expansion(ExpnId::root(), ExpnInfo {
752 allow_internal_unstable,
753 ..ExpnInfo::default(ExpnKind::Desugaring(reason), span, self.sess.edition())
757 fn with_anonymous_lifetime_mode<R>(
759 anonymous_lifetime_mode: AnonymousLifetimeMode,
760 op: impl FnOnce(&mut Self) -> R,
762 let old_anonymous_lifetime_mode = self.anonymous_lifetime_mode;
763 self.anonymous_lifetime_mode = anonymous_lifetime_mode;
764 let result = op(self);
765 self.anonymous_lifetime_mode = old_anonymous_lifetime_mode;
769 /// Creates a new `hir::GenericParam` for every new lifetime and
770 /// type parameter encountered while evaluating `f`. Definitions
771 /// are created with the parent provided. If no `parent_id` is
772 /// provided, no definitions will be returned.
774 /// Presuming that in-band lifetimes are enabled, then
775 /// `self.anonymous_lifetime_mode` will be updated to match the
776 /// argument while `f` is running (and restored afterwards).
777 fn collect_in_band_defs<T, F>(
780 anonymous_lifetime_mode: AnonymousLifetimeMode,
782 ) -> (Vec<hir::GenericParam>, T)
784 F: FnOnce(&mut LoweringContext<'_>) -> (Vec<hir::GenericParam>, T),
786 assert!(!self.is_collecting_in_band_lifetimes);
787 assert!(self.lifetimes_to_define.is_empty());
788 let old_anonymous_lifetime_mode = self.anonymous_lifetime_mode;
790 self.anonymous_lifetime_mode = anonymous_lifetime_mode;
791 self.is_collecting_in_band_lifetimes = true;
793 let (in_band_ty_params, res) = f(self);
795 self.is_collecting_in_band_lifetimes = false;
796 self.anonymous_lifetime_mode = old_anonymous_lifetime_mode;
798 let lifetimes_to_define = self.lifetimes_to_define.split_off(0);
800 let params = lifetimes_to_define
802 .map(|(span, hir_name)| self.lifetime_to_generic_param(
803 span, hir_name, parent_id.index,
805 .chain(in_band_ty_params.into_iter())
811 /// Converts a lifetime into a new generic parameter.
812 fn lifetime_to_generic_param(
816 parent_index: DefIndex,
817 ) -> hir::GenericParam {
818 let node_id = self.sess.next_node_id();
820 // Get the name we'll use to make the def-path. Note
821 // that collisions are ok here and this shouldn't
822 // really show up for end-user.
823 let (str_name, kind) = match hir_name {
824 ParamName::Plain(ident) => (
825 ident.as_interned_str(),
826 hir::LifetimeParamKind::InBand,
828 ParamName::Fresh(_) => (
829 kw::UnderscoreLifetime.as_interned_str(),
830 hir::LifetimeParamKind::Elided,
832 ParamName::Error => (
833 kw::UnderscoreLifetime.as_interned_str(),
834 hir::LifetimeParamKind::Error,
838 // Add a definition for the in-band lifetime def.
839 self.resolver.definitions().create_def_with_parent(
842 DefPathData::LifetimeNs(str_name),
848 hir_id: self.lower_node_id(node_id),
853 pure_wrt_drop: false,
854 kind: hir::GenericParamKind::Lifetime { kind }
858 /// When there is a reference to some lifetime `'a`, and in-band
859 /// lifetimes are enabled, then we want to push that lifetime into
860 /// the vector of names to define later. In that case, it will get
861 /// added to the appropriate generics.
862 fn maybe_collect_in_band_lifetime(&mut self, ident: Ident) {
863 if !self.is_collecting_in_band_lifetimes {
867 if !self.sess.features_untracked().in_band_lifetimes {
871 if self.in_scope_lifetimes.contains(&ParamName::Plain(ident.modern())) {
875 let hir_name = ParamName::Plain(ident);
877 if self.lifetimes_to_define.iter()
878 .any(|(_, lt_name)| lt_name.modern() == hir_name.modern()) {
882 self.lifetimes_to_define.push((ident.span, hir_name));
885 /// When we have either an elided or `'_` lifetime in an impl
886 /// header, we convert it to an in-band lifetime.
887 fn collect_fresh_in_band_lifetime(&mut self, span: Span) -> ParamName {
888 assert!(self.is_collecting_in_band_lifetimes);
889 let index = self.lifetimes_to_define.len();
890 let hir_name = ParamName::Fresh(index);
891 self.lifetimes_to_define.push((span, hir_name));
895 // Evaluates `f` with the lifetimes in `params` in-scope.
896 // This is used to track which lifetimes have already been defined, and
897 // which are new in-band lifetimes that need to have a definition created
899 fn with_in_scope_lifetime_defs<T, F>(&mut self, params: &[GenericParam], f: F) -> T
901 F: FnOnce(&mut LoweringContext<'_>) -> T,
903 let old_len = self.in_scope_lifetimes.len();
904 let lt_def_names = params.iter().filter_map(|param| match param.kind {
905 GenericParamKind::Lifetime { .. } => Some(ParamName::Plain(param.ident.modern())),
908 self.in_scope_lifetimes.extend(lt_def_names);
912 self.in_scope_lifetimes.truncate(old_len);
916 /// Appends in-band lifetime defs and argument-position `impl
917 /// Trait` defs to the existing set of generics.
919 /// Presuming that in-band lifetimes are enabled, then
920 /// `self.anonymous_lifetime_mode` will be updated to match the
921 /// argument while `f` is running (and restored afterwards).
922 fn add_in_band_defs<F, T>(
926 anonymous_lifetime_mode: AnonymousLifetimeMode,
928 ) -> (hir::Generics, T)
930 F: FnOnce(&mut LoweringContext<'_>, &mut Vec<hir::GenericParam>) -> T,
932 let (in_band_defs, (mut lowered_generics, res)) = self.with_in_scope_lifetime_defs(
935 this.collect_in_band_defs(parent_id, anonymous_lifetime_mode, |this| {
936 let mut params = Vec::new();
937 // Note: it is necessary to lower generics *before* calling `f`.
938 // When lowering `async fn`, there's a final step when lowering
939 // the return type that assumes that all in-scope lifetimes have
940 // already been added to either `in_scope_lifetimes` or
941 // `lifetimes_to_define`. If we swapped the order of these two,
942 // in-band-lifetimes introduced by generics or where-clauses
943 // wouldn't have been added yet.
944 let generics = this.lower_generics(
946 ImplTraitContext::Universal(&mut params),
948 let res = f(this, &mut params);
949 (params, (generics, res))
954 let mut lowered_params: Vec<_> = lowered_generics
960 // FIXME(const_generics): the compiler doesn't always cope with
961 // unsorted generic parameters at the moment, so we make sure
962 // that they're ordered correctly here for now. (When we chain
963 // the `in_band_defs`, we might make the order unsorted.)
964 lowered_params.sort_by_key(|param| {
966 hir::GenericParamKind::Lifetime { .. } => ParamKindOrd::Lifetime,
967 hir::GenericParamKind::Type { .. } => ParamKindOrd::Type,
968 hir::GenericParamKind::Const { .. } => ParamKindOrd::Const,
972 lowered_generics.params = lowered_params.into();
974 (lowered_generics, res)
977 fn with_dyn_type_scope<T, F>(&mut self, in_scope: bool, f: F) -> T
979 F: FnOnce(&mut LoweringContext<'_>) -> T,
981 let was_in_dyn_type = self.is_in_dyn_type;
982 self.is_in_dyn_type = in_scope;
984 let result = f(self);
986 self.is_in_dyn_type = was_in_dyn_type;
991 fn with_new_scopes<T, F>(&mut self, f: F) -> T
993 F: FnOnce(&mut LoweringContext<'_>) -> T,
995 let was_in_loop_condition = self.is_in_loop_condition;
996 self.is_in_loop_condition = false;
998 let catch_scopes = mem::take(&mut self.catch_scopes);
999 let loop_scopes = mem::take(&mut self.loop_scopes);
1001 self.catch_scopes = catch_scopes;
1002 self.loop_scopes = loop_scopes;
1004 self.is_in_loop_condition = was_in_loop_condition;
1009 fn def_key(&mut self, id: DefId) -> DefKey {
1011 self.resolver.definitions().def_key(id.index)
1013 self.cstore.def_key(id)
1017 fn lower_attrs_extendable(&mut self, attrs: &[Attribute]) -> Vec<Attribute> {
1020 .map(|a| self.lower_attr(a))
1024 fn lower_attrs(&mut self, attrs: &[Attribute]) -> hir::HirVec<Attribute> {
1025 self.lower_attrs_extendable(attrs).into()
1028 fn lower_attr(&mut self, attr: &Attribute) -> Attribute {
1029 // Note that we explicitly do not walk the path. Since we don't really
1030 // lower attributes (we use the AST version) there is nowhere to keep
1031 // the `HirId`s. We don't actually need HIR version of attributes anyway.
1035 path: attr.path.clone(),
1036 tokens: self.lower_token_stream(attr.tokens.clone()),
1037 is_sugared_doc: attr.is_sugared_doc,
1042 fn lower_token_stream(&mut self, tokens: TokenStream) -> TokenStream {
1045 .flat_map(|tree| self.lower_token_tree(tree).into_trees())
1049 fn lower_token_tree(&mut self, tree: TokenTree) -> TokenStream {
1051 TokenTree::Token(token) => self.lower_token(token),
1052 TokenTree::Delimited(span, delim, tts) => TokenTree::Delimited(
1055 self.lower_token_stream(tts),
1060 fn lower_token(&mut self, token: Token) -> TokenStream {
1062 token::Interpolated(nt) => {
1063 let tts = nt.to_tokenstream(&self.sess.parse_sess, token.span);
1064 self.lower_token_stream(tts)
1066 _ => TokenTree::Token(token).into(),
1070 /// Given an associated type constraint like one of these:
1073 /// T: Iterator<Item: Debug>
1075 /// T: Iterator<Item = Debug>
1079 /// returns a `hir::TypeBinding` representing `Item`.
1080 fn lower_assoc_ty_constraint(&mut self,
1081 c: &AssocTyConstraint,
1082 itctx: ImplTraitContext<'_>)
1083 -> hir::TypeBinding {
1084 debug!("lower_assoc_ty_constraint(constraint={:?}, itctx={:?})", c, itctx);
1086 let kind = match c.kind {
1087 AssocTyConstraintKind::Equality { ref ty } => hir::TypeBindingKind::Equality {
1088 ty: self.lower_ty(ty, itctx)
1090 AssocTyConstraintKind::Bound { ref bounds } => {
1091 // Piggy-back on the `impl Trait` context to figure out the correct behavior.
1092 let (desugar_to_impl_trait, itctx) = match itctx {
1093 // We are in the return position:
1095 // fn foo() -> impl Iterator<Item: Debug>
1099 // fn foo() -> impl Iterator<Item = impl Debug>
1100 ImplTraitContext::OpaqueTy(_) => (true, itctx),
1102 // We are in the argument position, but within a dyn type:
1104 // fn foo(x: dyn Iterator<Item: Debug>)
1108 // fn foo(x: dyn Iterator<Item = impl Debug>)
1109 ImplTraitContext::Universal(_) if self.is_in_dyn_type => (true, itctx),
1111 // In `type Foo = dyn Iterator<Item: Debug>` we desugar to
1112 // `type Foo = dyn Iterator<Item = impl Debug>` but we have to override the
1113 // "impl trait context" to permit `impl Debug` in this position (it desugars
1114 // then to an opaque type).
1116 // FIXME: this is only needed until `impl Trait` is allowed in type aliases.
1117 ImplTraitContext::Disallowed(_) if self.is_in_dyn_type =>
1118 (true, ImplTraitContext::OpaqueTy(None)),
1120 // We are in the argument position, but not within a dyn type:
1122 // fn foo(x: impl Iterator<Item: Debug>)
1124 // so we leave it as is and this gets expanded in astconv to a bound like
1125 // `<T as Iterator>::Item: Debug` where `T` is the type parameter for the
1127 _ => (false, itctx),
1130 if desugar_to_impl_trait {
1131 // Desugar `AssocTy: Bounds` into `AssocTy = impl Bounds`. We do this by
1132 // constructing the HIR for `impl bounds...` and then lowering that.
1134 let impl_trait_node_id = self.sess.next_node_id();
1135 let parent_def_index = self.current_hir_id_owner.last().unwrap().0;
1136 self.resolver.definitions().create_def_with_parent(
1139 DefPathData::ImplTrait,
1144 self.with_dyn_type_scope(false, |this| {
1145 let ty = this.lower_ty(
1147 id: this.sess.next_node_id(),
1148 node: TyKind::ImplTrait(impl_trait_node_id, bounds.clone()),
1154 hir::TypeBindingKind::Equality {
1159 // Desugar `AssocTy: Bounds` into a type binding where the
1160 // later desugars into a trait predicate.
1161 let bounds = self.lower_param_bounds(bounds, itctx);
1163 hir::TypeBindingKind::Constraint {
1171 hir_id: self.lower_node_id(c.id),
1178 fn lower_generic_arg(&mut self,
1179 arg: &ast::GenericArg,
1180 itctx: ImplTraitContext<'_>)
1181 -> hir::GenericArg {
1183 ast::GenericArg::Lifetime(lt) => GenericArg::Lifetime(self.lower_lifetime(<)),
1184 ast::GenericArg::Type(ty) => GenericArg::Type(self.lower_ty_direct(&ty, itctx)),
1185 ast::GenericArg::Const(ct) => {
1186 GenericArg::Const(ConstArg {
1187 value: self.lower_anon_const(&ct),
1188 span: ct.value.span,
1194 fn lower_ty(&mut self, t: &Ty, itctx: ImplTraitContext<'_>) -> P<hir::Ty> {
1195 P(self.lower_ty_direct(t, itctx))
1201 qself: &Option<QSelf>,
1203 param_mode: ParamMode,
1204 itctx: ImplTraitContext<'_>
1206 let id = self.lower_node_id(t.id);
1207 let qpath = self.lower_qpath(t.id, qself, path, param_mode, itctx);
1208 let ty = self.ty_path(id, t.span, qpath);
1209 if let hir::TyKind::TraitObject(..) = ty.node {
1210 self.maybe_lint_bare_trait(t.span, t.id, qself.is_none() && path.is_global());
1215 fn lower_ty_direct(&mut self, t: &Ty, mut itctx: ImplTraitContext<'_>) -> hir::Ty {
1216 let kind = match t.node {
1217 TyKind::Infer => hir::TyKind::Infer,
1218 TyKind::Err => hir::TyKind::Err,
1219 TyKind::Slice(ref ty) => hir::TyKind::Slice(self.lower_ty(ty, itctx)),
1220 TyKind::Ptr(ref mt) => hir::TyKind::Ptr(self.lower_mt(mt, itctx)),
1221 TyKind::Rptr(ref region, ref mt) => {
1222 let span = self.sess.source_map().next_point(t.span.shrink_to_lo());
1223 let lifetime = match *region {
1224 Some(ref lt) => self.lower_lifetime(lt),
1225 None => self.elided_ref_lifetime(span),
1227 hir::TyKind::Rptr(lifetime, self.lower_mt(mt, itctx))
1229 TyKind::BareFn(ref f) => self.with_in_scope_lifetime_defs(
1232 this.with_anonymous_lifetime_mode(
1233 AnonymousLifetimeMode::PassThrough,
1235 hir::TyKind::BareFn(P(hir::BareFnTy {
1236 generic_params: this.lower_generic_params(
1238 &NodeMap::default(),
1239 ImplTraitContext::disallowed(),
1241 unsafety: this.lower_unsafety(f.unsafety),
1243 decl: this.lower_fn_decl(&f.decl, None, false, None),
1244 arg_names: this.lower_fn_args_to_names(&f.decl),
1250 TyKind::Never => hir::TyKind::Never,
1251 TyKind::Tup(ref tys) => {
1252 hir::TyKind::Tup(tys.iter().map(|ty| {
1253 self.lower_ty_direct(ty, itctx.reborrow())
1256 TyKind::Paren(ref ty) => {
1257 return self.lower_ty_direct(ty, itctx);
1259 TyKind::Path(ref qself, ref path) => {
1260 return self.lower_path_ty(t, qself, path, ParamMode::Explicit, itctx);
1262 TyKind::ImplicitSelf => {
1263 let res = self.expect_full_res(t.id);
1264 let res = self.lower_res(res);
1265 hir::TyKind::Path(hir::QPath::Resolved(
1269 segments: hir_vec![hir::PathSegment::from_ident(
1270 Ident::with_empty_ctxt(kw::SelfUpper)
1276 TyKind::Array(ref ty, ref length) => {
1277 hir::TyKind::Array(self.lower_ty(ty, itctx), self.lower_anon_const(length))
1279 TyKind::Typeof(ref expr) => {
1280 hir::TyKind::Typeof(self.lower_anon_const(expr))
1282 TyKind::TraitObject(ref bounds, kind) => {
1283 let mut lifetime_bound = None;
1284 let (bounds, lifetime_bound) = self.with_dyn_type_scope(true, |this| {
1287 .filter_map(|bound| match *bound {
1288 GenericBound::Trait(ref ty, TraitBoundModifier::None) => {
1289 Some(this.lower_poly_trait_ref(ty, itctx.reborrow()))
1291 GenericBound::Trait(_, TraitBoundModifier::Maybe) => None,
1292 GenericBound::Outlives(ref lifetime) => {
1293 if lifetime_bound.is_none() {
1294 lifetime_bound = Some(this.lower_lifetime(lifetime));
1300 let lifetime_bound =
1301 lifetime_bound.unwrap_or_else(|| this.elided_dyn_bound(t.span));
1302 (bounds, lifetime_bound)
1304 if kind != TraitObjectSyntax::Dyn {
1305 self.maybe_lint_bare_trait(t.span, t.id, false);
1307 hir::TyKind::TraitObject(bounds, lifetime_bound)
1309 TyKind::ImplTrait(def_node_id, ref bounds) => {
1312 ImplTraitContext::OpaqueTy(fn_def_id) => {
1313 self.lower_opaque_impl_trait(
1314 span, fn_def_id, def_node_id,
1315 |this| this.lower_param_bounds(bounds, itctx),
1318 ImplTraitContext::Universal(in_band_ty_params) => {
1319 // Add a definition for the in-band `Param`.
1320 let def_index = self
1323 .opt_def_index(def_node_id)
1326 let hir_bounds = self.lower_param_bounds(
1328 ImplTraitContext::Universal(in_band_ty_params),
1330 // Set the name to `impl Bound1 + Bound2`.
1331 let ident = Ident::from_str(&pprust::ty_to_string(t)).with_span_pos(span);
1332 in_band_ty_params.push(hir::GenericParam {
1333 hir_id: self.lower_node_id(def_node_id),
1334 name: ParamName::Plain(ident),
1335 pure_wrt_drop: false,
1339 kind: hir::GenericParamKind::Type {
1341 synthetic: Some(hir::SyntheticTyParamKind::ImplTrait),
1345 hir::TyKind::Path(hir::QPath::Resolved(
1349 res: Res::Def(DefKind::TyParam, DefId::local(def_index)),
1350 segments: hir_vec![hir::PathSegment::from_ident(ident)],
1354 ImplTraitContext::Disallowed(pos) => {
1355 let allowed_in = if self.sess.features_untracked()
1356 .impl_trait_in_bindings {
1357 "bindings or function and inherent method return types"
1359 "function and inherent method return types"
1361 let mut err = struct_span_err!(
1365 "`impl Trait` not allowed outside of {}",
1368 if pos == ImplTraitPosition::Binding &&
1369 nightly_options::is_nightly_build() {
1371 "add `#![feature(impl_trait_in_bindings)]` to the crate \
1372 attributes to enable");
1379 TyKind::Mac(_) => bug!("`TyMac` should have been expanded by now."),
1380 TyKind::CVarArgs => {
1381 // Create the implicit lifetime of the "spoofed" `VaListImpl`.
1382 let span = self.sess.source_map().next_point(t.span.shrink_to_lo());
1383 let lt = self.new_implicit_lifetime(span);
1384 hir::TyKind::CVarArgs(lt)
1391 hir_id: self.lower_node_id(t.id),
1395 fn lower_opaque_impl_trait(
1398 fn_def_id: Option<DefId>,
1399 opaque_ty_node_id: NodeId,
1400 lower_bounds: impl FnOnce(&mut LoweringContext<'_>) -> hir::GenericBounds,
1402 // Make sure we know that some funky desugaring has been going on here.
1403 // This is a first: there is code in other places like for loop
1404 // desugaring that explicitly states that we don't want to track that.
1405 // Not tracking it makes lints in rustc and clippy very fragile, as
1406 // frequently opened issues show.
1407 let opaque_ty_span = self.mark_span_with_reason(
1408 DesugaringKind::OpaqueTy,
1413 let opaque_ty_def_index = self
1416 .opt_def_index(opaque_ty_node_id)
1419 self.allocate_hir_id_counter(opaque_ty_node_id);
1421 let hir_bounds = self.with_hir_id_owner(opaque_ty_node_id, lower_bounds);
1423 let (lifetimes, lifetime_defs) = self.lifetimes_from_impl_trait_bounds(
1425 opaque_ty_def_index,
1429 self.with_hir_id_owner(opaque_ty_node_id, |lctx| {
1430 let opaque_ty_item = hir::OpaqueTy {
1431 generics: hir::Generics {
1432 params: lifetime_defs,
1433 where_clause: hir::WhereClause {
1434 predicates: hir_vec![],
1440 impl_trait_fn: fn_def_id,
1441 origin: hir::OpaqueTyOrigin::FnReturn,
1444 trace!("exist ty from impl trait def-index: {:#?}", opaque_ty_def_index);
1445 let opaque_ty_id = lctx.generate_opaque_type(
1452 // `impl Trait` now just becomes `Foo<'a, 'b, ..>`.
1453 hir::TyKind::Def(hir::ItemId { id: opaque_ty_id }, lifetimes)
1457 /// Registers a new opaque type with the proper `NodeId`s and
1458 /// returns the lowered node-ID for the opaque type.
1459 fn generate_opaque_type(
1461 opaque_ty_node_id: NodeId,
1462 opaque_ty_item: hir::OpaqueTy,
1464 opaque_ty_span: Span,
1466 let opaque_ty_item_kind = hir::ItemKind::OpaqueTy(opaque_ty_item);
1467 let opaque_ty_id = self.lower_node_id(opaque_ty_node_id);
1468 // Generate an `type Foo = impl Trait;` declaration.
1469 trace!("registering opaque type with id {:#?}", opaque_ty_id);
1470 let opaque_ty_item = hir::Item {
1471 hir_id: opaque_ty_id,
1472 ident: Ident::invalid(),
1473 attrs: Default::default(),
1474 node: opaque_ty_item_kind,
1475 vis: respan(span.shrink_to_lo(), hir::VisibilityKind::Inherited),
1476 span: opaque_ty_span,
1479 // Insert the item into the global item list. This usually happens
1480 // automatically for all AST items. But this opaque type item
1481 // does not actually exist in the AST.
1482 self.insert_item(opaque_ty_item);
1486 fn lifetimes_from_impl_trait_bounds(
1488 opaque_ty_id: NodeId,
1489 parent_index: DefIndex,
1490 bounds: &hir::GenericBounds,
1491 ) -> (HirVec<hir::GenericArg>, HirVec<hir::GenericParam>) {
1492 // This visitor walks over `impl Trait` bounds and creates defs for all lifetimes that
1493 // appear in the bounds, excluding lifetimes that are created within the bounds.
1494 // E.g., `'a`, `'b`, but not `'c` in `impl for<'c> SomeTrait<'a, 'b, 'c>`.
1495 struct ImplTraitLifetimeCollector<'r, 'a> {
1496 context: &'r mut LoweringContext<'a>,
1498 opaque_ty_id: NodeId,
1499 collect_elided_lifetimes: bool,
1500 currently_bound_lifetimes: Vec<hir::LifetimeName>,
1501 already_defined_lifetimes: FxHashSet<hir::LifetimeName>,
1502 output_lifetimes: Vec<hir::GenericArg>,
1503 output_lifetime_params: Vec<hir::GenericParam>,
1506 impl<'r, 'a, 'v> hir::intravisit::Visitor<'v> for ImplTraitLifetimeCollector<'r, 'a> {
1507 fn nested_visit_map<'this>(
1509 ) -> hir::intravisit::NestedVisitorMap<'this, 'v> {
1510 hir::intravisit::NestedVisitorMap::None
1513 fn visit_generic_args(&mut self, span: Span, parameters: &'v hir::GenericArgs) {
1514 // Don't collect elided lifetimes used inside of `Fn()` syntax.
1515 if parameters.parenthesized {
1516 let old_collect_elided_lifetimes = self.collect_elided_lifetimes;
1517 self.collect_elided_lifetimes = false;
1518 hir::intravisit::walk_generic_args(self, span, parameters);
1519 self.collect_elided_lifetimes = old_collect_elided_lifetimes;
1521 hir::intravisit::walk_generic_args(self, span, parameters);
1525 fn visit_ty(&mut self, t: &'v hir::Ty) {
1526 // Don't collect elided lifetimes used inside of `fn()` syntax.
1527 if let hir::TyKind::BareFn(_) = t.node {
1528 let old_collect_elided_lifetimes = self.collect_elided_lifetimes;
1529 self.collect_elided_lifetimes = false;
1531 // Record the "stack height" of `for<'a>` lifetime bindings
1532 // to be able to later fully undo their introduction.
1533 let old_len = self.currently_bound_lifetimes.len();
1534 hir::intravisit::walk_ty(self, t);
1535 self.currently_bound_lifetimes.truncate(old_len);
1537 self.collect_elided_lifetimes = old_collect_elided_lifetimes;
1539 hir::intravisit::walk_ty(self, t)
1543 fn visit_poly_trait_ref(
1545 trait_ref: &'v hir::PolyTraitRef,
1546 modifier: hir::TraitBoundModifier,
1548 // Record the "stack height" of `for<'a>` lifetime bindings
1549 // to be able to later fully undo their introduction.
1550 let old_len = self.currently_bound_lifetimes.len();
1551 hir::intravisit::walk_poly_trait_ref(self, trait_ref, modifier);
1552 self.currently_bound_lifetimes.truncate(old_len);
1555 fn visit_generic_param(&mut self, param: &'v hir::GenericParam) {
1556 // Record the introduction of 'a in `for<'a> ...`.
1557 if let hir::GenericParamKind::Lifetime { .. } = param.kind {
1558 // Introduce lifetimes one at a time so that we can handle
1559 // cases like `fn foo<'d>() -> impl for<'a, 'b: 'a, 'c: 'b + 'd>`.
1560 let lt_name = hir::LifetimeName::Param(param.name);
1561 self.currently_bound_lifetimes.push(lt_name);
1564 hir::intravisit::walk_generic_param(self, param);
1567 fn visit_lifetime(&mut self, lifetime: &'v hir::Lifetime) {
1568 let name = match lifetime.name {
1569 hir::LifetimeName::Implicit | hir::LifetimeName::Underscore => {
1570 if self.collect_elided_lifetimes {
1571 // Use `'_` for both implicit and underscore lifetimes in
1572 // `type Foo<'_> = impl SomeTrait<'_>;`.
1573 hir::LifetimeName::Underscore
1578 hir::LifetimeName::Param(_) => lifetime.name,
1579 hir::LifetimeName::Error | hir::LifetimeName::Static => return,
1582 if !self.currently_bound_lifetimes.contains(&name)
1583 && !self.already_defined_lifetimes.contains(&name) {
1584 self.already_defined_lifetimes.insert(name);
1586 self.output_lifetimes.push(hir::GenericArg::Lifetime(hir::Lifetime {
1587 hir_id: self.context.next_id(),
1588 span: lifetime.span,
1592 let def_node_id = self.context.sess.next_node_id();
1594 self.context.lower_node_id_with_owner(def_node_id, self.opaque_ty_id);
1595 self.context.resolver.definitions().create_def_with_parent(
1598 DefPathData::LifetimeNs(name.ident().as_interned_str()),
1602 let (name, kind) = match name {
1603 hir::LifetimeName::Underscore => (
1604 hir::ParamName::Plain(Ident::with_empty_ctxt(kw::UnderscoreLifetime)),
1605 hir::LifetimeParamKind::Elided,
1607 hir::LifetimeName::Param(param_name) => (
1609 hir::LifetimeParamKind::Explicit,
1611 _ => bug!("expected `LifetimeName::Param` or `ParamName::Plain`"),
1614 self.output_lifetime_params.push(hir::GenericParam {
1617 span: lifetime.span,
1618 pure_wrt_drop: false,
1621 kind: hir::GenericParamKind::Lifetime { kind }
1627 let mut lifetime_collector = ImplTraitLifetimeCollector {
1629 parent: parent_index,
1631 collect_elided_lifetimes: true,
1632 currently_bound_lifetimes: Vec::new(),
1633 already_defined_lifetimes: FxHashSet::default(),
1634 output_lifetimes: Vec::new(),
1635 output_lifetime_params: Vec::new(),
1638 for bound in bounds {
1639 hir::intravisit::walk_param_bound(&mut lifetime_collector, &bound);
1643 lifetime_collector.output_lifetimes.into(),
1644 lifetime_collector.output_lifetime_params.into(),
1651 qself: &Option<QSelf>,
1653 param_mode: ParamMode,
1654 mut itctx: ImplTraitContext<'_>,
1656 let qself_position = qself.as_ref().map(|q| q.position);
1657 let qself = qself.as_ref().map(|q| self.lower_ty(&q.ty, itctx.reborrow()));
1659 let partial_res = self.resolver
1660 .get_partial_res(id)
1661 .unwrap_or_else(|| PartialRes::new(Res::Err));
1663 let proj_start = p.segments.len() - partial_res.unresolved_segments();
1664 let path = P(hir::Path {
1665 res: self.lower_res(partial_res.base_res()),
1666 segments: p.segments[..proj_start]
1669 .map(|(i, segment)| {
1670 let param_mode = match (qself_position, param_mode) {
1671 (Some(j), ParamMode::Optional) if i < j => {
1672 // This segment is part of the trait path in a
1673 // qualified path - one of `a`, `b` or `Trait`
1674 // in `<X as a::b::Trait>::T::U::method`.
1680 // Figure out if this is a type/trait segment,
1681 // which may need lifetime elision performed.
1682 let parent_def_id = |this: &mut Self, def_id: DefId| DefId {
1683 krate: def_id.krate,
1684 index: this.def_key(def_id).parent.expect("missing parent"),
1686 let type_def_id = match partial_res.base_res() {
1687 Res::Def(DefKind::AssocTy, def_id) if i + 2 == proj_start => {
1688 Some(parent_def_id(self, def_id))
1690 Res::Def(DefKind::Variant, def_id) if i + 1 == proj_start => {
1691 Some(parent_def_id(self, def_id))
1693 Res::Def(DefKind::Struct, def_id)
1694 | Res::Def(DefKind::Union, def_id)
1695 | Res::Def(DefKind::Enum, def_id)
1696 | Res::Def(DefKind::TyAlias, def_id)
1697 | Res::Def(DefKind::Trait, def_id) if i + 1 == proj_start =>
1703 let parenthesized_generic_args = match partial_res.base_res() {
1704 // `a::b::Trait(Args)`
1705 Res::Def(DefKind::Trait, _)
1706 if i + 1 == proj_start => ParenthesizedGenericArgs::Ok,
1707 // `a::b::Trait(Args)::TraitItem`
1708 Res::Def(DefKind::Method, _)
1709 | Res::Def(DefKind::AssocConst, _)
1710 | Res::Def(DefKind::AssocTy, _)
1711 if i + 2 == proj_start =>
1713 ParenthesizedGenericArgs::Ok
1715 // Avoid duplicated errors.
1716 Res::Err => ParenthesizedGenericArgs::Ok,
1718 Res::Def(DefKind::Struct, _)
1719 | Res::Def(DefKind::Enum, _)
1720 | Res::Def(DefKind::Union, _)
1721 | Res::Def(DefKind::TyAlias, _)
1722 | Res::Def(DefKind::Variant, _) if i + 1 == proj_start =>
1724 ParenthesizedGenericArgs::Err
1726 // A warning for now, for compatibility reasons.
1727 _ => ParenthesizedGenericArgs::Warn,
1730 let num_lifetimes = type_def_id.map_or(0, |def_id| {
1731 if let Some(&n) = self.type_def_lifetime_params.get(&def_id) {
1734 assert!(!def_id.is_local());
1736 self.cstore.item_generics_cloned_untracked(def_id, self.sess);
1737 let n = item_generics.own_counts().lifetimes;
1738 self.type_def_lifetime_params.insert(def_id, n);
1741 self.lower_path_segment(
1746 parenthesized_generic_args,
1755 // Simple case, either no projections, or only fully-qualified.
1756 // E.g., `std::mem::size_of` or `<I as Iterator>::Item`.
1757 if partial_res.unresolved_segments() == 0 {
1758 return hir::QPath::Resolved(qself, path);
1761 // Create the innermost type that we're projecting from.
1762 let mut ty = if path.segments.is_empty() {
1763 // If the base path is empty that means there exists a
1764 // syntactical `Self`, e.g., `&i32` in `<&i32>::clone`.
1765 qself.expect("missing QSelf for <T>::...")
1767 // Otherwise, the base path is an implicit `Self` type path,
1768 // e.g., `Vec` in `Vec::new` or `<I as Iterator>::Item` in
1769 // `<I as Iterator>::Item::default`.
1770 let new_id = self.next_id();
1771 P(self.ty_path(new_id, p.span, hir::QPath::Resolved(qself, path)))
1774 // Anything after the base path are associated "extensions",
1775 // out of which all but the last one are associated types,
1776 // e.g., for `std::vec::Vec::<T>::IntoIter::Item::clone`:
1777 // * base path is `std::vec::Vec<T>`
1778 // * "extensions" are `IntoIter`, `Item` and `clone`
1779 // * type nodes are:
1780 // 1. `std::vec::Vec<T>` (created above)
1781 // 2. `<std::vec::Vec<T>>::IntoIter`
1782 // 3. `<<std::vec::Vec<T>>::IntoIter>::Item`
1783 // * final path is `<<<std::vec::Vec<T>>::IntoIter>::Item>::clone`
1784 for (i, segment) in p.segments.iter().enumerate().skip(proj_start) {
1785 let segment = P(self.lower_path_segment(
1790 ParenthesizedGenericArgs::Warn,
1794 let qpath = hir::QPath::TypeRelative(ty, segment);
1796 // It's finished, return the extension of the right node type.
1797 if i == p.segments.len() - 1 {
1801 // Wrap the associated extension in another type node.
1802 let new_id = self.next_id();
1803 ty = P(self.ty_path(new_id, p.span, qpath));
1806 // We should've returned in the for loop above.
1809 "lower_qpath: no final extension segment in {}..{}",
1815 fn lower_path_extra(
1819 param_mode: ParamMode,
1820 explicit_owner: Option<NodeId>,
1824 segments: p.segments
1827 self.lower_path_segment(
1832 ParenthesizedGenericArgs::Err,
1833 ImplTraitContext::disallowed(),
1842 fn lower_path(&mut self, id: NodeId, p: &Path, param_mode: ParamMode) -> hir::Path {
1843 let res = self.expect_full_res(id);
1844 let res = self.lower_res(res);
1845 self.lower_path_extra(res, p, param_mode, None)
1848 fn lower_path_segment(
1851 segment: &PathSegment,
1852 param_mode: ParamMode,
1853 expected_lifetimes: usize,
1854 parenthesized_generic_args: ParenthesizedGenericArgs,
1855 itctx: ImplTraitContext<'_>,
1856 explicit_owner: Option<NodeId>,
1857 ) -> hir::PathSegment {
1858 let (mut generic_args, infer_args) = if let Some(ref generic_args) = segment.args {
1859 let msg = "parenthesized type parameters may only be used with a `Fn` trait";
1860 match **generic_args {
1861 GenericArgs::AngleBracketed(ref data) => {
1862 self.lower_angle_bracketed_parameter_data(data, param_mode, itctx)
1864 GenericArgs::Parenthesized(ref data) => match parenthesized_generic_args {
1865 ParenthesizedGenericArgs::Ok => self.lower_parenthesized_parameter_data(data),
1866 ParenthesizedGenericArgs::Warn => {
1867 self.sess.buffer_lint(
1868 PARENTHESIZED_PARAMS_IN_TYPES_AND_MODULES,
1873 (hir::GenericArgs::none(), true)
1875 ParenthesizedGenericArgs::Err => {
1876 let mut err = struct_span_err!(self.sess, data.span, E0214, "{}", msg);
1877 err.span_label(data.span, "only `Fn` traits may use parentheses");
1878 if let Ok(snippet) = self.sess.source_map().span_to_snippet(data.span) {
1879 // Do not suggest going from `Trait()` to `Trait<>`
1880 if data.inputs.len() > 0 {
1881 err.span_suggestion(
1883 "use angle brackets instead",
1884 format!("<{}>", &snippet[1..snippet.len() - 1]),
1885 Applicability::MaybeIncorrect,
1891 self.lower_angle_bracketed_parameter_data(
1892 &data.as_angle_bracketed_args(),
1902 self.lower_angle_bracketed_parameter_data(&Default::default(), param_mode, itctx)
1905 let has_lifetimes = generic_args.args.iter().any(|arg| match arg {
1906 GenericArg::Lifetime(_) => true,
1909 let first_generic_span = generic_args.args.iter().map(|a| a.span())
1910 .chain(generic_args.bindings.iter().map(|b| b.span)).next();
1911 if !generic_args.parenthesized && !has_lifetimes {
1913 self.elided_path_lifetimes(path_span, expected_lifetimes)
1915 .map(|lt| GenericArg::Lifetime(lt))
1916 .chain(generic_args.args.into_iter())
1918 if expected_lifetimes > 0 && param_mode == ParamMode::Explicit {
1919 let anon_lt_suggestion = vec!["'_"; expected_lifetimes].join(", ");
1920 let no_non_lt_args = generic_args.args.len() == expected_lifetimes;
1921 let no_bindings = generic_args.bindings.is_empty();
1922 let (incl_angl_brckt, insertion_sp, suggestion) = if no_non_lt_args && no_bindings {
1923 // If there are no (non-implicit) generic args or associated type
1924 // bindings, our suggestion includes the angle brackets.
1925 (true, path_span.shrink_to_hi(), format!("<{}>", anon_lt_suggestion))
1927 // Otherwise (sorry, this is kind of gross) we need to infer the
1928 // place to splice in the `'_, ` from the generics that do exist.
1929 let first_generic_span = first_generic_span
1930 .expect("already checked that non-lifetime args or bindings exist");
1931 (false, first_generic_span.shrink_to_lo(), format!("{}, ", anon_lt_suggestion))
1933 match self.anonymous_lifetime_mode {
1934 // In create-parameter mode we error here because we don't want to support
1935 // deprecated impl elision in new features like impl elision and `async fn`,
1936 // both of which work using the `CreateParameter` mode:
1938 // impl Foo for std::cell::Ref<u32> // note lack of '_
1939 // async fn foo(_: std::cell::Ref<u32>) { ... }
1940 AnonymousLifetimeMode::CreateParameter => {
1941 let mut err = struct_span_err!(
1945 "implicit elided lifetime not allowed here"
1947 crate::lint::builtin::add_elided_lifetime_in_path_suggestion(
1958 AnonymousLifetimeMode::PassThrough |
1959 AnonymousLifetimeMode::ReportError |
1960 AnonymousLifetimeMode::Replace(_) => {
1961 self.sess.buffer_lint_with_diagnostic(
1962 ELIDED_LIFETIMES_IN_PATHS,
1965 "hidden lifetime parameters in types are deprecated",
1966 builtin::BuiltinLintDiagnostics::ElidedLifetimesInPaths(
1979 let res = self.expect_full_res(segment.id);
1980 let id = if let Some(owner) = explicit_owner {
1981 self.lower_node_id_with_owner(segment.id, owner)
1983 self.lower_node_id(segment.id)
1986 "lower_path_segment: ident={:?} original-id={:?} new-id={:?}",
1987 segment.ident, segment.id, id,
1990 hir::PathSegment::new(
1993 Some(self.lower_res(res)),
1999 fn lower_angle_bracketed_parameter_data(
2001 data: &AngleBracketedArgs,
2002 param_mode: ParamMode,
2003 mut itctx: ImplTraitContext<'_>,
2004 ) -> (hir::GenericArgs, bool) {
2005 let &AngleBracketedArgs { ref args, ref constraints, .. } = data;
2006 let has_non_lt_args = args.iter().any(|arg| match arg {
2007 ast::GenericArg::Lifetime(_) => false,
2008 ast::GenericArg::Type(_) => true,
2009 ast::GenericArg::Const(_) => true,
2013 args: args.iter().map(|a| self.lower_generic_arg(a, itctx.reborrow())).collect(),
2014 bindings: constraints.iter()
2015 .map(|b| self.lower_assoc_ty_constraint(b, itctx.reborrow()))
2017 parenthesized: false,
2019 !has_non_lt_args && param_mode == ParamMode::Optional
2023 fn lower_parenthesized_parameter_data(
2025 data: &ParenthesizedArgs,
2026 ) -> (hir::GenericArgs, bool) {
2027 // Switch to `PassThrough` mode for anonymous lifetimes; this
2028 // means that we permit things like `&Ref<T>`, where `Ref` has
2029 // a hidden lifetime parameter. This is needed for backwards
2030 // compatibility, even in contexts like an impl header where
2031 // we generally don't permit such things (see #51008).
2032 self.with_anonymous_lifetime_mode(
2033 AnonymousLifetimeMode::PassThrough,
2035 let &ParenthesizedArgs { ref inputs, ref output, span } = data;
2038 .map(|ty| this.lower_ty_direct(ty, ImplTraitContext::disallowed()))
2040 let mk_tup = |this: &mut Self, tys, span| {
2041 hir::Ty { node: hir::TyKind::Tup(tys), hir_id: this.next_id(), span }
2045 args: hir_vec![GenericArg::Type(mk_tup(this, inputs, span))],
2048 hir_id: this.next_id(),
2049 ident: Ident::with_empty_ctxt(FN_OUTPUT_NAME),
2050 kind: hir::TypeBindingKind::Equality {
2053 .map(|ty| this.lower_ty(
2055 ImplTraitContext::disallowed()
2058 P(mk_tup(this, hir::HirVec::new(), span))
2061 span: output.as_ref().map_or(span, |ty| ty.span),
2064 parenthesized: true,
2072 fn lower_local(&mut self, l: &Local) -> (hir::Local, SmallVec<[NodeId; 1]>) {
2073 let mut ids = SmallVec::<[NodeId; 1]>::new();
2074 if self.sess.features_untracked().impl_trait_in_bindings {
2075 if let Some(ref ty) = l.ty {
2076 let mut visitor = ImplTraitTypeIdVisitor { ids: &mut ids };
2077 visitor.visit_ty(ty);
2080 let parent_def_id = DefId::local(self.current_hir_id_owner.last().unwrap().0);
2082 hir_id: self.lower_node_id(l.id),
2085 .map(|t| self.lower_ty(t,
2086 if self.sess.features_untracked().impl_trait_in_bindings {
2087 ImplTraitContext::OpaqueTy(Some(parent_def_id))
2089 ImplTraitContext::Disallowed(ImplTraitPosition::Binding)
2092 pat: self.lower_pat(&l.pat),
2093 init: l.init.as_ref().map(|e| P(self.lower_expr(e))),
2095 attrs: l.attrs.clone(),
2096 source: hir::LocalSource::Normal,
2100 fn lower_mutability(&mut self, m: Mutability) -> hir::Mutability {
2102 Mutability::Mutable => hir::MutMutable,
2103 Mutability::Immutable => hir::MutImmutable,
2107 fn lower_fn_args_to_names(&mut self, decl: &FnDecl) -> hir::HirVec<Ident> {
2110 .map(|arg| match arg.pat.node {
2111 PatKind::Ident(_, ident, _) => ident,
2112 _ => Ident::new(kw::Invalid, arg.pat.span),
2117 // Lowers a function declaration.
2119 // `decl`: the unlowered (AST) function declaration.
2120 // `fn_def_id`: if `Some`, impl Trait arguments are lowered into generic parameters on the
2121 // given DefId, otherwise impl Trait is disallowed. Must be `Some` if
2122 // `make_ret_async` is also `Some`.
2123 // `impl_trait_return_allow`: determines whether `impl Trait` can be used in return position.
2124 // This guards against trait declarations and implementations where `impl Trait` is
2126 // `make_ret_async`: if `Some`, converts `-> T` into `-> impl Future<Output = T>` in the
2127 // return type. This is used for `async fn` declarations. The `NodeId` is the ID of the
2128 // return type `impl Trait` item.
2132 mut in_band_ty_params: Option<(DefId, &mut Vec<hir::GenericParam>)>,
2133 impl_trait_return_allow: bool,
2134 make_ret_async: Option<NodeId>,
2135 ) -> P<hir::FnDecl> {
2136 let lt_mode = if make_ret_async.is_some() {
2137 // In `async fn`, argument-position elided lifetimes
2138 // must be transformed into fresh generic parameters so that
2139 // they can be applied to the opaque `impl Trait` return type.
2140 AnonymousLifetimeMode::CreateParameter
2142 self.anonymous_lifetime_mode
2145 // Remember how many lifetimes were already around so that we can
2146 // only look at the lifetime parameters introduced by the arguments.
2147 let lifetime_count_before_args = self.lifetimes_to_define.len();
2148 let inputs = self.with_anonymous_lifetime_mode(lt_mode, |this| {
2152 if let Some((_, ibty)) = &mut in_band_ty_params {
2153 this.lower_ty_direct(&arg.ty, ImplTraitContext::Universal(ibty))
2155 this.lower_ty_direct(&arg.ty, ImplTraitContext::disallowed())
2158 .collect::<HirVec<_>>()
2161 let output = if let Some(ret_id) = make_ret_async {
2162 // Calculate the `LtReplacement` to use for any return-position elided
2163 // lifetimes based on the elided lifetime parameters introduced in the args.
2164 let lt_replacement = get_elided_lt_replacement(
2165 &self.lifetimes_to_define[lifetime_count_before_args..]
2167 self.lower_async_fn_ret_ty(
2169 in_band_ty_params.expect("`make_ret_async` but no `fn_def_id`").0,
2175 FunctionRetTy::Ty(ref ty) => match in_band_ty_params {
2176 Some((def_id, _)) if impl_trait_return_allow => {
2177 hir::Return(self.lower_ty(ty,
2178 ImplTraitContext::OpaqueTy(Some(def_id))
2182 hir::Return(self.lower_ty(ty, ImplTraitContext::disallowed()))
2185 FunctionRetTy::Default(span) => hir::DefaultReturn(span),
2192 c_variadic: decl.c_variadic,
2193 implicit_self: decl.inputs.get(0).map_or(
2194 hir::ImplicitSelfKind::None,
2196 let is_mutable_pat = match arg.pat.node {
2197 PatKind::Ident(BindingMode::ByValue(mt), _, _) |
2198 PatKind::Ident(BindingMode::ByRef(mt), _, _) =>
2199 mt == Mutability::Mutable,
2204 TyKind::ImplicitSelf if is_mutable_pat => hir::ImplicitSelfKind::Mut,
2205 TyKind::ImplicitSelf => hir::ImplicitSelfKind::Imm,
2206 // Given we are only considering `ImplicitSelf` types, we needn't consider
2207 // the case where we have a mutable pattern to a reference as that would
2208 // no longer be an `ImplicitSelf`.
2209 TyKind::Rptr(_, ref mt) if mt.ty.node.is_implicit_self() &&
2210 mt.mutbl == ast::Mutability::Mutable =>
2211 hir::ImplicitSelfKind::MutRef,
2212 TyKind::Rptr(_, ref mt) if mt.ty.node.is_implicit_self() =>
2213 hir::ImplicitSelfKind::ImmRef,
2214 _ => hir::ImplicitSelfKind::None,
2221 // Transforms `-> T` for `async fn` into `-> OpaqueTy { .. }`
2222 // combined with the following definition of `OpaqueTy`:
2224 // type OpaqueTy<generics_from_parent_fn> = impl Future<Output = T>;
2226 // `inputs`: lowered types of arguments to the function (used to collect lifetimes)
2227 // `output`: unlowered output type (`T` in `-> T`)
2228 // `fn_def_id`: `DefId` of the parent function (used to create child impl trait definition)
2229 // `opaque_ty_node_id`: `NodeId` of the opaque `impl Trait` type that should be created
2230 // `elided_lt_replacement`: replacement for elided lifetimes in the return type
2231 fn lower_async_fn_ret_ty(
2233 output: &FunctionRetTy,
2235 opaque_ty_node_id: NodeId,
2236 elided_lt_replacement: LtReplacement,
2237 ) -> hir::FunctionRetTy {
2238 let span = output.span();
2240 let opaque_ty_span = self.mark_span_with_reason(
2241 DesugaringKind::Async,
2246 let opaque_ty_def_index = self
2249 .opt_def_index(opaque_ty_node_id)
2252 self.allocate_hir_id_counter(opaque_ty_node_id);
2254 let (opaque_ty_id, lifetime_params) = self.with_hir_id_owner(opaque_ty_node_id, |this| {
2255 let future_bound = this.with_anonymous_lifetime_mode(
2256 AnonymousLifetimeMode::Replace(elided_lt_replacement),
2257 |this| this.lower_async_fn_output_type_to_future_bound(
2264 // Calculate all the lifetimes that should be captured
2265 // by the opaque type. This should include all in-scope
2266 // lifetime parameters, including those defined in-band.
2268 // Note: this must be done after lowering the output type,
2269 // as the output type may introduce new in-band lifetimes.
2270 let lifetime_params: Vec<(Span, ParamName)> =
2271 this.in_scope_lifetimes
2273 .map(|name| (name.ident().span, name))
2274 .chain(this.lifetimes_to_define.iter().cloned())
2277 debug!("lower_async_fn_ret_ty: in_scope_lifetimes={:#?}", this.in_scope_lifetimes);
2278 debug!("lower_async_fn_ret_ty: lifetimes_to_define={:#?}", this.lifetimes_to_define);
2279 debug!("lower_async_fn_ret_ty: lifetime_params={:#?}", lifetime_params);
2281 let generic_params =
2284 .map(|(span, hir_name)| {
2285 this.lifetime_to_generic_param(span, hir_name, opaque_ty_def_index)
2289 let opaque_ty_item = hir::OpaqueTy {
2290 generics: hir::Generics {
2291 params: generic_params,
2292 where_clause: hir::WhereClause {
2293 predicates: hir_vec![],
2298 bounds: hir_vec![future_bound],
2299 impl_trait_fn: Some(fn_def_id),
2300 origin: hir::OpaqueTyOrigin::AsyncFn,
2303 trace!("exist ty from async fn def index: {:#?}", opaque_ty_def_index);
2304 let opaque_ty_id = this.generate_opaque_type(
2311 (opaque_ty_id, lifetime_params)
2317 .map(|(span, hir_name)| {
2318 GenericArg::Lifetime(hir::Lifetime {
2319 hir_id: self.next_id(),
2321 name: hir::LifetimeName::Param(hir_name),
2326 let opaque_ty_ref = hir::TyKind::Def(hir::ItemId { id: opaque_ty_id }, generic_args);
2328 hir::FunctionRetTy::Return(P(hir::Ty {
2329 node: opaque_ty_ref,
2331 hir_id: self.next_id(),
2335 /// Transforms `-> T` into `Future<Output = T>`
2336 fn lower_async_fn_output_type_to_future_bound(
2338 output: &FunctionRetTy,
2341 ) -> hir::GenericBound {
2342 // Compute the `T` in `Future<Output = T>` from the return type.
2343 let output_ty = match output {
2344 FunctionRetTy::Ty(ty) => {
2345 self.lower_ty(ty, ImplTraitContext::OpaqueTy(Some(fn_def_id)))
2347 FunctionRetTy::Default(ret_ty_span) => {
2349 hir_id: self.next_id(),
2350 node: hir::TyKind::Tup(hir_vec![]),
2357 let future_params = P(hir::GenericArgs {
2359 bindings: hir_vec![hir::TypeBinding {
2360 ident: Ident::with_empty_ctxt(FN_OUTPUT_NAME),
2361 kind: hir::TypeBindingKind::Equality {
2364 hir_id: self.next_id(),
2367 parenthesized: false,
2370 // ::std::future::Future<future_params>
2372 P(self.std_path(span, &[sym::future, sym::Future], Some(future_params), false));
2374 hir::GenericBound::Trait(
2376 trait_ref: hir::TraitRef {
2378 hir_ref_id: self.next_id(),
2380 bound_generic_params: hir_vec![],
2383 hir::TraitBoundModifier::None,
2387 fn lower_param_bound(
2390 itctx: ImplTraitContext<'_>,
2391 ) -> hir::GenericBound {
2393 GenericBound::Trait(ref ty, modifier) => {
2394 hir::GenericBound::Trait(
2395 self.lower_poly_trait_ref(ty, itctx),
2396 self.lower_trait_bound_modifier(modifier),
2399 GenericBound::Outlives(ref lifetime) => {
2400 hir::GenericBound::Outlives(self.lower_lifetime(lifetime))
2405 fn lower_lifetime(&mut self, l: &Lifetime) -> hir::Lifetime {
2406 let span = l.ident.span;
2408 ident if ident.name == kw::StaticLifetime =>
2409 self.new_named_lifetime(l.id, span, hir::LifetimeName::Static),
2410 ident if ident.name == kw::UnderscoreLifetime =>
2411 match self.anonymous_lifetime_mode {
2412 AnonymousLifetimeMode::CreateParameter => {
2413 let fresh_name = self.collect_fresh_in_band_lifetime(span);
2414 self.new_named_lifetime(l.id, span, hir::LifetimeName::Param(fresh_name))
2417 AnonymousLifetimeMode::PassThrough => {
2418 self.new_named_lifetime(l.id, span, hir::LifetimeName::Underscore)
2421 AnonymousLifetimeMode::ReportError => self.new_error_lifetime(Some(l.id), span),
2423 AnonymousLifetimeMode::Replace(replacement) => {
2424 let hir_id = self.lower_node_id(l.id);
2425 self.replace_elided_lifetime(hir_id, span, replacement)
2429 self.maybe_collect_in_band_lifetime(ident);
2430 let param_name = ParamName::Plain(ident);
2431 self.new_named_lifetime(l.id, span, hir::LifetimeName::Param(param_name))
2436 fn new_named_lifetime(
2440 name: hir::LifetimeName,
2441 ) -> hir::Lifetime {
2443 hir_id: self.lower_node_id(id),
2449 /// Replace a return-position elided lifetime with the elided lifetime
2450 /// from the arguments.
2451 fn replace_elided_lifetime(
2455 replacement: LtReplacement,
2456 ) -> hir::Lifetime {
2457 let multiple_or_none = match replacement {
2458 LtReplacement::Some(name) => {
2459 return hir::Lifetime {
2462 name: hir::LifetimeName::Param(name),
2465 LtReplacement::MultipleLifetimes => "multiple",
2466 LtReplacement::NoLifetimes => "none",
2469 let mut err = crate::middle::resolve_lifetime::report_missing_lifetime_specifiers(
2475 "return-position elided lifetimes require exactly one \
2476 input-position elided lifetime, found {}.", multiple_or_none));
2479 hir::Lifetime { hir_id, span, name: hir::LifetimeName::Error }
2482 fn lower_generic_params(
2484 params: &[GenericParam],
2485 add_bounds: &NodeMap<Vec<GenericBound>>,
2486 mut itctx: ImplTraitContext<'_>,
2487 ) -> hir::HirVec<hir::GenericParam> {
2488 params.iter().map(|param| {
2489 self.lower_generic_param(param, add_bounds, itctx.reborrow())
2493 fn lower_generic_param(&mut self,
2494 param: &GenericParam,
2495 add_bounds: &NodeMap<Vec<GenericBound>>,
2496 mut itctx: ImplTraitContext<'_>)
2497 -> hir::GenericParam {
2498 let mut bounds = self.with_anonymous_lifetime_mode(
2499 AnonymousLifetimeMode::ReportError,
2500 |this| this.lower_param_bounds(¶m.bounds, itctx.reborrow()),
2503 let (name, kind) = match param.kind {
2504 GenericParamKind::Lifetime => {
2505 let was_collecting_in_band = self.is_collecting_in_band_lifetimes;
2506 self.is_collecting_in_band_lifetimes = false;
2508 let lt = self.with_anonymous_lifetime_mode(
2509 AnonymousLifetimeMode::ReportError,
2510 |this| this.lower_lifetime(&Lifetime { id: param.id, ident: param.ident }),
2512 let param_name = match lt.name {
2513 hir::LifetimeName::Param(param_name) => param_name,
2514 hir::LifetimeName::Implicit
2515 | hir::LifetimeName::Underscore
2516 | hir::LifetimeName::Static => hir::ParamName::Plain(lt.name.ident()),
2517 hir::LifetimeName::Error => ParamName::Error,
2520 let kind = hir::GenericParamKind::Lifetime {
2521 kind: hir::LifetimeParamKind::Explicit
2524 self.is_collecting_in_band_lifetimes = was_collecting_in_band;
2528 GenericParamKind::Type { ref default, .. } => {
2529 // Don't expose `Self` (recovered "keyword used as ident" parse error).
2530 // `rustc::ty` expects `Self` to be only used for a trait's `Self`.
2531 // Instead, use `gensym("Self")` to create a distinct name that looks the same.
2532 let ident = if param.ident.name == kw::SelfUpper {
2533 param.ident.gensym()
2538 let add_bounds = add_bounds.get(¶m.id).map_or(&[][..], |x| &x);
2539 if !add_bounds.is_empty() {
2540 let params = self.lower_param_bounds(add_bounds, itctx.reborrow()).into_iter();
2541 bounds = bounds.into_iter()
2546 let kind = hir::GenericParamKind::Type {
2547 default: default.as_ref().map(|x| {
2548 self.lower_ty(x, ImplTraitContext::OpaqueTy(None))
2550 synthetic: param.attrs.iter()
2551 .filter(|attr| attr.check_name(sym::rustc_synthetic))
2552 .map(|_| hir::SyntheticTyParamKind::ImplTrait)
2556 (hir::ParamName::Plain(ident), kind)
2558 GenericParamKind::Const { ref ty } => {
2559 (hir::ParamName::Plain(param.ident), hir::GenericParamKind::Const {
2560 ty: self.lower_ty(&ty, ImplTraitContext::disallowed()),
2566 hir_id: self.lower_node_id(param.id),
2568 span: param.ident.span,
2569 pure_wrt_drop: attr::contains_name(¶m.attrs, sym::may_dangle),
2570 attrs: self.lower_attrs(¶m.attrs),
2576 fn lower_trait_ref(&mut self, p: &TraitRef, itctx: ImplTraitContext<'_>) -> hir::TraitRef {
2577 let path = match self.lower_qpath(p.ref_id, &None, &p.path, ParamMode::Explicit, itctx) {
2578 hir::QPath::Resolved(None, path) => path,
2579 qpath => bug!("lower_trait_ref: unexpected QPath `{:?}`", qpath),
2583 hir_ref_id: self.lower_node_id(p.ref_id),
2587 fn lower_poly_trait_ref(
2590 mut itctx: ImplTraitContext<'_>,
2591 ) -> hir::PolyTraitRef {
2592 let bound_generic_params = self.lower_generic_params(
2593 &p.bound_generic_params,
2594 &NodeMap::default(),
2597 let trait_ref = self.with_in_scope_lifetime_defs(
2598 &p.bound_generic_params,
2599 |this| this.lower_trait_ref(&p.trait_ref, itctx),
2603 bound_generic_params,
2609 fn lower_mt(&mut self, mt: &MutTy, itctx: ImplTraitContext<'_>) -> hir::MutTy {
2611 ty: self.lower_ty(&mt.ty, itctx),
2612 mutbl: self.lower_mutability(mt.mutbl),
2616 fn lower_param_bounds(&mut self, bounds: &[GenericBound], mut itctx: ImplTraitContext<'_>)
2617 -> hir::GenericBounds {
2618 bounds.iter().map(|bound| self.lower_param_bound(bound, itctx.reborrow())).collect()
2621 fn lower_block_with_stmts(
2624 targeted_by_break: bool,
2625 mut stmts: Vec<hir::Stmt>,
2626 ) -> P<hir::Block> {
2627 let mut expr = None;
2629 for (index, stmt) in b.stmts.iter().enumerate() {
2630 if index == b.stmts.len() - 1 {
2631 if let StmtKind::Expr(ref e) = stmt.node {
2632 expr = Some(P(self.lower_expr(e)));
2634 stmts.extend(self.lower_stmt(stmt));
2637 stmts.extend(self.lower_stmt(stmt));
2642 hir_id: self.lower_node_id(b.id),
2643 stmts: stmts.into(),
2645 rules: self.lower_block_check_mode(&b.rules),
2651 fn lower_block(&mut self, b: &Block, targeted_by_break: bool) -> P<hir::Block> {
2652 self.lower_block_with_stmts(b, targeted_by_break, vec![])
2655 fn lower_pat(&mut self, p: &Pat) -> P<hir::Pat> {
2656 let node = match p.node {
2657 PatKind::Wild => hir::PatKind::Wild,
2658 PatKind::Ident(ref binding_mode, ident, ref sub) => {
2659 let lower_sub = |this: &mut Self| sub.as_ref().map(|x| this.lower_pat(x));
2660 self.lower_pat_ident(p, binding_mode, ident, lower_sub)
2662 PatKind::Lit(ref e) => hir::PatKind::Lit(P(self.lower_expr(e))),
2663 PatKind::TupleStruct(ref path, ref pats) => {
2664 let qpath = self.lower_qpath(
2668 ParamMode::Optional,
2669 ImplTraitContext::disallowed(),
2671 let (pats, ddpos) = self.lower_pat_tuple(pats, "tuple struct");
2672 hir::PatKind::TupleStruct(qpath, pats, ddpos)
2674 PatKind::Path(ref qself, ref path) => {
2675 let qpath = self.lower_qpath(
2679 ParamMode::Optional,
2680 ImplTraitContext::disallowed(),
2682 hir::PatKind::Path(qpath)
2684 PatKind::Struct(ref path, ref fields, etc) => {
2685 let qpath = self.lower_qpath(
2689 ParamMode::Optional,
2690 ImplTraitContext::disallowed(),
2698 node: hir::FieldPat {
2699 hir_id: self.next_id(),
2700 ident: f.node.ident,
2701 pat: self.lower_pat(&f.node.pat),
2702 is_shorthand: f.node.is_shorthand,
2707 hir::PatKind::Struct(qpath, fs, etc)
2709 PatKind::Tuple(ref pats) => {
2710 let (pats, ddpos) = self.lower_pat_tuple(pats, "tuple");
2711 hir::PatKind::Tuple(pats, ddpos)
2713 PatKind::Box(ref inner) => hir::PatKind::Box(self.lower_pat(inner)),
2714 PatKind::Ref(ref inner, mutbl) => {
2715 hir::PatKind::Ref(self.lower_pat(inner), self.lower_mutability(mutbl))
2717 PatKind::Range(ref e1, ref e2, Spanned { node: ref end, .. }) => hir::PatKind::Range(
2718 P(self.lower_expr(e1)),
2719 P(self.lower_expr(e2)),
2720 self.lower_range_end(end),
2722 PatKind::Slice(ref pats) => self.lower_pat_slice(pats),
2724 // If we reach here the `..` pattern is not semantically allowed.
2725 self.ban_illegal_rest_pat(p.span)
2727 PatKind::Paren(ref inner) => return self.lower_pat(inner),
2728 PatKind::Mac(_) => panic!("Shouldn't exist here"),
2731 self.pat_with_node_id_of(p, node)
2738 ) -> (HirVec<P<hir::Pat>>, Option<usize>) {
2739 let mut elems = Vec::with_capacity(pats.len());
2740 let mut rest = None;
2742 let mut iter = pats.iter().enumerate();
2743 while let Some((idx, pat)) = iter.next() {
2744 // Interpret the first `..` pattern as a subtuple pattern.
2746 rest = Some((idx, pat.span));
2749 // It was not a subslice pattern so lower it normally.
2750 elems.push(self.lower_pat(pat));
2753 while let Some((_, pat)) = iter.next() {
2754 // There was a previous subtuple pattern; make sure we don't allow more.
2756 self.ban_extra_rest_pat(pat.span, rest.unwrap().1, ctx);
2758 elems.push(self.lower_pat(pat));
2762 (elems.into(), rest.map(|(ddpos, _)| ddpos))
2765 fn lower_pat_slice(&mut self, pats: &[AstP<Pat>]) -> hir::PatKind {
2766 let mut before = Vec::new();
2767 let mut after = Vec::new();
2768 let mut slice = None;
2769 let mut prev_rest_span = None;
2771 let mut iter = pats.iter();
2772 while let Some(pat) = iter.next() {
2773 // Interpret the first `((ref mut?)? x @)? ..` pattern as a subslice pattern.
2776 prev_rest_span = Some(pat.span);
2777 slice = Some(self.pat_wild_with_node_id_of(pat));
2780 PatKind::Ident(ref bm, ident, Some(ref sub)) if sub.is_rest() => {
2781 prev_rest_span = Some(sub.span);
2782 let lower_sub = |this: &mut Self| Some(this.pat_wild_with_node_id_of(sub));
2783 let node = self.lower_pat_ident(pat, bm, ident, lower_sub);
2784 slice = Some(self.pat_with_node_id_of(pat, node));
2790 // It was not a subslice pattern so lower it normally.
2791 before.push(self.lower_pat(pat));
2794 while let Some(pat) = iter.next() {
2795 // There was a previous subslice pattern; make sure we don't allow more.
2796 let rest_span = match pat.node {
2797 PatKind::Rest => Some(pat.span),
2798 PatKind::Ident(.., Some(ref sub)) if sub.is_rest() => {
2799 // The `HirValidator` is merciless; add a `_` pattern to avoid ICEs.
2800 after.push(self.pat_wild_with_node_id_of(pat));
2805 if let Some(rest_span) = rest_span {
2806 self.ban_extra_rest_pat(rest_span, prev_rest_span.unwrap(), "slice");
2808 after.push(self.lower_pat(pat));
2812 hir::PatKind::Slice(before.into(), slice, after.into())
2818 binding_mode: &BindingMode,
2820 lower_sub: impl FnOnce(&mut Self) -> Option<P<hir::Pat>>,
2822 match self.resolver.get_partial_res(p.id).map(|d| d.base_res()) {
2823 // `None` can occur in body-less function signatures
2824 res @ None | res @ Some(Res::Local(_)) => {
2825 let canonical_id = match res {
2826 Some(Res::Local(id)) => id,
2830 hir::PatKind::Binding(
2831 self.lower_binding_mode(binding_mode),
2832 self.lower_node_id(canonical_id),
2837 Some(res) => hir::PatKind::Path(hir::QPath::Resolved(
2841 res: self.lower_res(res),
2842 segments: hir_vec![hir::PathSegment::from_ident(ident)],
2848 fn pat_wild_with_node_id_of(&mut self, p: &Pat) -> P<hir::Pat> {
2849 self.pat_with_node_id_of(p, hir::PatKind::Wild)
2852 /// Construct a `Pat` with the `HirId` of `p.id` lowered.
2853 fn pat_with_node_id_of(&mut self, p: &Pat, node: hir::PatKind) -> P<hir::Pat> {
2855 hir_id: self.lower_node_id(p.id),
2861 /// Emit a friendly error for extra `..` patterns in a tuple/tuple struct/slice pattern.
2862 fn ban_extra_rest_pat(&self, sp: Span, prev_sp: Span, ctx: &str) {
2864 .struct_span_err(sp, &format!("`..` can only be used once per {} pattern", ctx))
2865 .span_label(sp, &format!("can only be used once per {} pattern", ctx))
2866 .span_label(prev_sp, "previously used here")
2870 /// Used to ban the `..` pattern in places it shouldn't be semantically.
2871 fn ban_illegal_rest_pat(&self, sp: Span) -> hir::PatKind {
2873 .struct_span_err(sp, "`..` patterns are not allowed here")
2874 .note("only allowed in tuple, tuple struct, and slice patterns")
2877 // We're not in a list context so `..` can be reasonably treated
2878 // as `_` because it should always be valid and roughly matches the
2879 // intent of `..` (notice that the rest of a single slot is that slot).
2883 fn lower_range_end(&mut self, e: &RangeEnd) -> hir::RangeEnd {
2885 RangeEnd::Included(_) => hir::RangeEnd::Included,
2886 RangeEnd::Excluded => hir::RangeEnd::Excluded,
2890 fn lower_anon_const(&mut self, c: &AnonConst) -> hir::AnonConst {
2891 self.with_new_scopes(|this| {
2893 hir_id: this.lower_node_id(c.id),
2894 body: this.lower_const_body(&c.value),
2899 fn lower_stmt(&mut self, s: &Stmt) -> SmallVec<[hir::Stmt; 1]> {
2900 let node = match s.node {
2901 StmtKind::Local(ref l) => {
2902 let (l, item_ids) = self.lower_local(l);
2903 let mut ids: SmallVec<[hir::Stmt; 1]> = item_ids
2906 let item_id = hir::ItemId { id: self.lower_node_id(item_id) };
2907 self.stmt(s.span, hir::StmtKind::Item(item_id))
2912 hir_id: self.lower_node_id(s.id),
2913 node: hir::StmtKind::Local(P(l)),
2919 StmtKind::Item(ref it) => {
2920 // Can only use the ID once.
2921 let mut id = Some(s.id);
2922 return self.lower_item_id(it)
2925 let hir_id = id.take()
2926 .map(|id| self.lower_node_id(id))
2927 .unwrap_or_else(|| self.next_id());
2931 node: hir::StmtKind::Item(item_id),
2937 StmtKind::Expr(ref e) => hir::StmtKind::Expr(P(self.lower_expr(e))),
2938 StmtKind::Semi(ref e) => hir::StmtKind::Semi(P(self.lower_expr(e))),
2939 StmtKind::Mac(..) => panic!("Shouldn't exist here"),
2941 smallvec![hir::Stmt {
2942 hir_id: self.lower_node_id(s.id),
2948 fn lower_block_check_mode(&mut self, b: &BlockCheckMode) -> hir::BlockCheckMode {
2950 BlockCheckMode::Default => hir::DefaultBlock,
2951 BlockCheckMode::Unsafe(u) => hir::UnsafeBlock(self.lower_unsafe_source(u)),
2955 fn lower_binding_mode(&mut self, b: &BindingMode) -> hir::BindingAnnotation {
2957 BindingMode::ByValue(Mutability::Immutable) => hir::BindingAnnotation::Unannotated,
2958 BindingMode::ByRef(Mutability::Immutable) => hir::BindingAnnotation::Ref,
2959 BindingMode::ByValue(Mutability::Mutable) => hir::BindingAnnotation::Mutable,
2960 BindingMode::ByRef(Mutability::Mutable) => hir::BindingAnnotation::RefMut,
2964 fn lower_unsafe_source(&mut self, u: UnsafeSource) -> hir::UnsafeSource {
2966 CompilerGenerated => hir::CompilerGenerated,
2967 UserProvided => hir::UserProvided,
2971 fn lower_trait_bound_modifier(&mut self, f: TraitBoundModifier) -> hir::TraitBoundModifier {
2973 TraitBoundModifier::None => hir::TraitBoundModifier::None,
2974 TraitBoundModifier::Maybe => hir::TraitBoundModifier::Maybe,
2978 // Helper methods for building HIR.
2980 fn stmt(&mut self, span: Span, node: hir::StmtKind) -> hir::Stmt {
2981 hir::Stmt { span, node, hir_id: self.next_id() }
2984 fn stmt_expr(&mut self, span: Span, expr: hir::Expr) -> hir::Stmt {
2985 self.stmt(span, hir::StmtKind::Expr(P(expr)))
2990 attrs: ThinVec<Attribute>,
2992 init: Option<P<hir::Expr>>,
2994 source: hir::LocalSource,
2996 let local = hir::Local {
2998 hir_id: self.next_id(),
3005 self.stmt(span, hir::StmtKind::Local(P(local)))
3008 fn block_expr(&mut self, expr: P<hir::Expr>) -> hir::Block {
3009 self.block_all(expr.span, hir::HirVec::new(), Some(expr))
3015 stmts: hir::HirVec<hir::Stmt>,
3016 expr: Option<P<hir::Expr>>,
3021 hir_id: self.next_id(),
3022 rules: hir::DefaultBlock,
3024 targeted_by_break: false,
3028 /// Constructs a `true` or `false` literal pattern.
3029 fn pat_bool(&mut self, span: Span, val: bool) -> P<hir::Pat> {
3030 let expr = self.expr_bool(span, val);
3031 self.pat(span, hir::PatKind::Lit(P(expr)))
3034 fn pat_ok(&mut self, span: Span, pat: P<hir::Pat>) -> P<hir::Pat> {
3035 self.pat_std_enum(span, &[sym::result, sym::Result, sym::Ok], hir_vec![pat])
3038 fn pat_err(&mut self, span: Span, pat: P<hir::Pat>) -> P<hir::Pat> {
3039 self.pat_std_enum(span, &[sym::result, sym::Result, sym::Err], hir_vec![pat])
3042 fn pat_some(&mut self, span: Span, pat: P<hir::Pat>) -> P<hir::Pat> {
3043 self.pat_std_enum(span, &[sym::option, sym::Option, sym::Some], hir_vec![pat])
3046 fn pat_none(&mut self, span: Span) -> P<hir::Pat> {
3047 self.pat_std_enum(span, &[sym::option, sym::Option, sym::None], hir_vec![])
3053 components: &[Symbol],
3054 subpats: hir::HirVec<P<hir::Pat>>,
3056 let path = self.std_path(span, components, None, true);
3057 let qpath = hir::QPath::Resolved(None, P(path));
3058 let pt = if subpats.is_empty() {
3059 hir::PatKind::Path(qpath)
3061 hir::PatKind::TupleStruct(qpath, subpats, None)
3066 fn pat_ident(&mut self, span: Span, ident: Ident) -> (P<hir::Pat>, hir::HirId) {
3067 self.pat_ident_binding_mode(span, ident, hir::BindingAnnotation::Unannotated)
3070 fn pat_ident_binding_mode(
3074 bm: hir::BindingAnnotation,
3075 ) -> (P<hir::Pat>, hir::HirId) {
3076 let hir_id = self.next_id();
3081 node: hir::PatKind::Binding(bm, hir_id, ident.with_span_pos(span), None),
3088 fn pat_wild(&mut self, span: Span) -> P<hir::Pat> {
3089 self.pat(span, hir::PatKind::Wild)
3092 fn pat(&mut self, span: Span, pat: hir::PatKind) -> P<hir::Pat> {
3094 hir_id: self.next_id(),
3100 /// Given a suffix `["b", "c", "d"]`, returns path `::std::b::c::d` when
3101 /// `fld.cx.use_std`, and `::core::b::c::d` otherwise.
3102 /// The path is also resolved according to `is_value`.
3106 components: &[Symbol],
3107 params: Option<P<hir::GenericArgs>>,
3110 let ns = if is_value { Namespace::ValueNS } else { Namespace::TypeNS };
3111 let (path, res) = self.resolver.resolve_str_path(span, self.crate_root, components, ns);
3113 let mut segments: Vec<_> = path.segments.iter().map(|segment| {
3114 let res = self.expect_full_res(segment.id);
3116 ident: segment.ident,
3117 hir_id: Some(self.lower_node_id(segment.id)),
3118 res: Some(self.lower_res(res)),
3123 segments.last_mut().unwrap().args = params;
3127 res: res.map_id(|_| panic!("unexpected node_id")),
3128 segments: segments.into(),
3132 fn ty_path(&mut self, mut hir_id: hir::HirId, span: Span, qpath: hir::QPath) -> hir::Ty {
3133 let node = match qpath {
3134 hir::QPath::Resolved(None, path) => {
3135 // Turn trait object paths into `TyKind::TraitObject` instead.
3137 Res::Def(DefKind::Trait, _) | Res::Def(DefKind::TraitAlias, _) => {
3138 let principal = hir::PolyTraitRef {
3139 bound_generic_params: hir::HirVec::new(),
3140 trait_ref: hir::TraitRef {
3147 // The original ID is taken by the `PolyTraitRef`,
3148 // so the `Ty` itself needs a different one.
3149 hir_id = self.next_id();
3150 hir::TyKind::TraitObject(hir_vec![principal], self.elided_dyn_bound(span))
3152 _ => hir::TyKind::Path(hir::QPath::Resolved(None, path)),
3155 _ => hir::TyKind::Path(qpath),
3164 /// Invoked to create the lifetime argument for a type `&T`
3165 /// with no explicit lifetime.
3166 fn elided_ref_lifetime(&mut self, span: Span) -> hir::Lifetime {
3167 match self.anonymous_lifetime_mode {
3168 // Intercept when we are in an impl header or async fn and introduce an in-band
3170 // Hence `impl Foo for &u32` becomes `impl<'f> Foo for &'f u32` for some fresh
3172 AnonymousLifetimeMode::CreateParameter => {
3173 let fresh_name = self.collect_fresh_in_band_lifetime(span);
3175 hir_id: self.next_id(),
3177 name: hir::LifetimeName::Param(fresh_name),
3181 AnonymousLifetimeMode::ReportError => self.new_error_lifetime(None, span),
3183 AnonymousLifetimeMode::PassThrough => self.new_implicit_lifetime(span),
3185 AnonymousLifetimeMode::Replace(replacement) => {
3186 self.new_replacement_lifetime(replacement, span)
3191 /// Report an error on illegal use of `'_` or a `&T` with no explicit lifetime;
3192 /// return a "error lifetime".
3193 fn new_error_lifetime(&mut self, id: Option<NodeId>, span: Span) -> hir::Lifetime {
3194 let (id, msg, label) = match id {
3195 Some(id) => (id, "`'_` cannot be used here", "`'_` is a reserved lifetime name"),
3198 self.sess.next_node_id(),
3199 "`&` without an explicit lifetime name cannot be used here",
3200 "explicit lifetime name needed here",
3204 let mut err = struct_span_err!(
3211 err.span_label(span, label);
3214 self.new_named_lifetime(id, span, hir::LifetimeName::Error)
3217 /// Invoked to create the lifetime argument(s) for a path like
3218 /// `std::cell::Ref<T>`; note that implicit lifetimes in these
3219 /// sorts of cases are deprecated. This may therefore report a warning or an
3220 /// error, depending on the mode.
3221 fn elided_path_lifetimes(&mut self, span: Span, count: usize) -> P<[hir::Lifetime]> {
3223 .map(|_| self.elided_path_lifetime(span))
3227 fn elided_path_lifetime(&mut self, span: Span) -> hir::Lifetime {
3228 match self.anonymous_lifetime_mode {
3229 AnonymousLifetimeMode::CreateParameter => {
3230 // We should have emitted E0726 when processing this path above
3231 self.sess.delay_span_bug(
3233 "expected 'implicit elided lifetime not allowed' error",
3235 let id = self.sess.next_node_id();
3236 self.new_named_lifetime(id, span, hir::LifetimeName::Error)
3238 // This is the normal case.
3239 AnonymousLifetimeMode::PassThrough => self.new_implicit_lifetime(span),
3241 AnonymousLifetimeMode::Replace(replacement) => {
3242 self.new_replacement_lifetime(replacement, span)
3245 AnonymousLifetimeMode::ReportError => self.new_error_lifetime(None, span),
3249 /// Invoked to create the lifetime argument(s) for an elided trait object
3250 /// bound, like the bound in `Box<dyn Debug>`. This method is not invoked
3251 /// when the bound is written, even if it is written with `'_` like in
3252 /// `Box<dyn Debug + '_>`. In those cases, `lower_lifetime` is invoked.
3253 fn elided_dyn_bound(&mut self, span: Span) -> hir::Lifetime {
3254 match self.anonymous_lifetime_mode {
3255 // NB. We intentionally ignore the create-parameter mode here.
3256 // and instead "pass through" to resolve-lifetimes, which will apply
3257 // the object-lifetime-defaulting rules. Elided object lifetime defaults
3258 // do not act like other elided lifetimes. In other words, given this:
3260 // impl Foo for Box<dyn Debug>
3262 // we do not introduce a fresh `'_` to serve as the bound, but instead
3263 // ultimately translate to the equivalent of:
3265 // impl Foo for Box<dyn Debug + 'static>
3267 // `resolve_lifetime` has the code to make that happen.
3268 AnonymousLifetimeMode::CreateParameter => {}
3270 AnonymousLifetimeMode::ReportError => {
3271 // ReportError applies to explicit use of `'_`.
3274 // This is the normal case.
3275 AnonymousLifetimeMode::PassThrough => {}
3277 // We don't need to do any replacement here as this lifetime
3278 // doesn't refer to an elided lifetime elsewhere in the function
3280 AnonymousLifetimeMode::Replace(_) => {}
3283 self.new_implicit_lifetime(span)
3286 fn new_replacement_lifetime(
3288 replacement: LtReplacement,
3290 ) -> hir::Lifetime {
3291 let hir_id = self.next_id();
3292 self.replace_elided_lifetime(hir_id, span, replacement)
3295 fn new_implicit_lifetime(&mut self, span: Span) -> hir::Lifetime {
3297 hir_id: self.next_id(),
3299 name: hir::LifetimeName::Implicit,
3303 fn maybe_lint_bare_trait(&self, span: Span, id: NodeId, is_global: bool) {
3304 // FIXME(davidtwco): This is a hack to detect macros which produce spans of the
3305 // call site which do not have a macro backtrace. See #61963.
3306 let is_macro_callsite = self.sess.source_map()
3307 .span_to_snippet(span)
3308 .map(|snippet| snippet.starts_with("#["))
3310 if !is_macro_callsite {
3311 self.sess.buffer_lint_with_diagnostic(
3312 builtin::BARE_TRAIT_OBJECTS,
3315 "trait objects without an explicit `dyn` are deprecated",
3316 builtin::BuiltinLintDiagnostics::BareTraitObject(span, is_global),
3322 fn body_ids(bodies: &BTreeMap<hir::BodyId, hir::Body>) -> Vec<hir::BodyId> {
3323 // Sorting by span ensures that we get things in order within a
3324 // file, and also puts the files in a sensible order.
3325 let mut body_ids: Vec<_> = bodies.keys().cloned().collect();
3326 body_ids.sort_by_key(|b| bodies[b].value.span);
3330 /// Checks if the specified expression is a built-in range literal.
3331 /// (See: `LoweringContext::lower_expr()`).
3332 pub fn is_range_literal(sess: &Session, expr: &hir::Expr) -> bool {
3333 use hir::{Path, QPath, ExprKind, TyKind};
3335 // Returns whether the given path represents a (desugared) range,
3336 // either in std or core, i.e. has either a `::std::ops::Range` or
3337 // `::core::ops::Range` prefix.
3338 fn is_range_path(path: &Path) -> bool {
3339 let segs: Vec<_> = path.segments.iter().map(|seg| seg.ident.as_str().to_string()).collect();
3340 let segs: Vec<_> = segs.iter().map(|seg| &**seg).collect();
3342 // "{{root}}" is the equivalent of `::` prefix in `Path`.
3343 if let ["{{root}}", std_core, "ops", range] = segs.as_slice() {
3344 (*std_core == "std" || *std_core == "core") && range.starts_with("Range")
3350 // Check whether a span corresponding to a range expression is a
3351 // range literal, rather than an explicit struct or `new()` call.
3352 fn is_lit(sess: &Session, span: &Span) -> bool {
3353 let source_map = sess.source_map();
3354 let end_point = source_map.end_point(*span);
3356 if let Ok(end_string) = source_map.span_to_snippet(end_point) {
3357 !(end_string.ends_with("}") || end_string.ends_with(")"))
3364 // All built-in range literals but `..=` and `..` desugar to `Struct`s.
3365 ExprKind::Struct(ref qpath, _, _) => {
3366 if let QPath::Resolved(None, ref path) = **qpath {
3367 return is_range_path(&path) && is_lit(sess, &expr.span);
3371 // `..` desugars to its struct path.
3372 ExprKind::Path(QPath::Resolved(None, ref path)) => {
3373 return is_range_path(&path) && is_lit(sess, &expr.span);
3376 // `..=` desugars into `::std::ops::RangeInclusive::new(...)`.
3377 ExprKind::Call(ref func, _) => {
3378 if let ExprKind::Path(QPath::TypeRelative(ref ty, ref segment)) = func.node {
3379 if let TyKind::Path(QPath::Resolved(None, ref path)) = ty.node {
3380 let new_call = segment.ident.as_str() == "new";
3381 return is_range_path(&path) && is_lit(sess, &expr.span) && new_call;