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.
139 in_scope_lifetimes: Vec<ParamName>,
141 current_module: NodeId,
143 type_def_lifetime_params: DefIdMap<usize>,
145 current_hir_id_owner: Vec<(DefIndex, u32)>,
146 item_local_id_counters: NodeMap<u32>,
147 node_id_to_hir_id: IndexVec<NodeId, hir::HirId>,
149 allow_try_trait: Option<Lrc<[Symbol]>>,
150 allow_gen_future: Option<Lrc<[Symbol]>>,
154 /// Obtain resolution for a `NodeId` with a single resolution.
155 fn get_partial_res(&mut self, id: NodeId) -> Option<PartialRes>;
157 /// Obtain per-namespace resolutions for `use` statement with the given `NoedId`.
158 fn get_import_res(&mut self, id: NodeId) -> PerNS<Option<Res<NodeId>>>;
160 /// Obtain resolution for a label with the given `NodeId`.
161 fn get_label_res(&mut self, id: NodeId) -> Option<NodeId>;
163 /// We must keep the set of definitions up to date as we add nodes that weren't in the AST.
164 /// This should only return `None` during testing.
165 fn definitions(&mut self) -> &mut Definitions;
167 /// Given suffix `["b", "c", "d"]`, creates an AST path for `[::crate_root]::b::c::d` and
168 /// resolves it based on `is_value`.
172 crate_root: Option<Symbol>,
173 components: &[Symbol],
175 ) -> (ast::Path, Res<NodeId>);
177 fn has_derives(&self, node_id: NodeId, derives: SpecialDerives) -> bool;
180 /// Context of `impl Trait` in code, which determines whether it is allowed in an HIR subtree,
181 /// and if so, what meaning it has.
183 enum ImplTraitContext<'a> {
184 /// Treat `impl Trait` as shorthand for a new universal generic parameter.
185 /// Example: `fn foo(x: impl Debug)`, where `impl Debug` is conceptually
186 /// equivalent to a fresh universal parameter like `fn foo<T: Debug>(x: T)`.
188 /// Newly generated parameters should be inserted into the given `Vec`.
189 Universal(&'a mut Vec<hir::GenericParam>),
191 /// Treat `impl Trait` as shorthand for a new opaque type.
192 /// Example: `fn foo() -> impl Debug`, where `impl Debug` is conceptually
193 /// equivalent to a new opaque type like `type T = impl Debug; fn foo() -> T`.
195 /// We optionally store a `DefId` for the parent item here so we can look up necessary
196 /// information later. It is `None` when no information about the context should be stored
197 /// (e.g., for consts and statics).
198 OpaqueTy(Option<DefId> /* fn def-ID */),
200 /// `impl Trait` is not accepted in this position.
201 Disallowed(ImplTraitPosition),
204 /// Position in which `impl Trait` is disallowed.
205 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
206 enum ImplTraitPosition {
207 /// Disallowed in `let` / `const` / `static` bindings.
210 /// All other posiitons.
214 impl<'a> ImplTraitContext<'a> {
216 fn disallowed() -> Self {
217 ImplTraitContext::Disallowed(ImplTraitPosition::Other)
220 fn reborrow(&'b mut self) -> ImplTraitContext<'b> {
221 use self::ImplTraitContext::*;
223 Universal(params) => Universal(params),
224 OpaqueTy(fn_def_id) => OpaqueTy(*fn_def_id),
225 Disallowed(pos) => Disallowed(*pos),
232 cstore: &dyn CrateStore,
233 dep_graph: &DepGraph,
235 resolver: &mut dyn Resolver,
237 // We're constructing the HIR here; we don't care what we will
238 // read, since we haven't even constructed the *input* to
240 dep_graph.assert_ignored();
243 crate_root: sess.parse_sess.injected_crate_name.try_get().copied(),
247 items: BTreeMap::new(),
248 trait_items: BTreeMap::new(),
249 impl_items: BTreeMap::new(),
250 bodies: BTreeMap::new(),
251 trait_impls: BTreeMap::new(),
252 modules: BTreeMap::new(),
253 exported_macros: Vec::new(),
254 non_exported_macro_attrs: Vec::new(),
255 catch_scopes: Vec::new(),
256 loop_scopes: Vec::new(),
257 is_in_loop_condition: false,
258 is_in_trait_impl: false,
259 is_in_dyn_type: false,
260 anonymous_lifetime_mode: AnonymousLifetimeMode::PassThrough,
261 type_def_lifetime_params: Default::default(),
262 current_module: CRATE_NODE_ID,
263 current_hir_id_owner: vec![(CRATE_DEF_INDEX, 0)],
264 item_local_id_counters: Default::default(),
265 node_id_to_hir_id: IndexVec::new(),
266 generator_kind: None,
268 lifetimes_to_define: Vec::new(),
269 is_collecting_in_band_lifetimes: false,
270 in_scope_lifetimes: Vec::new(),
271 allow_try_trait: Some([sym::try_trait][..].into()),
272 allow_gen_future: Some([sym::gen_future][..].into()),
276 #[derive(Copy, Clone, PartialEq)]
278 /// Any path in a type context.
280 /// Path in a type definition, where the anonymous lifetime `'_` is not allowed.
282 /// The `module::Type` in `module::Type::method` in an expression.
286 enum ParenthesizedGenericArgs {
292 /// What to do when we encounter an **anonymous** lifetime
293 /// reference. Anonymous lifetime references come in two flavors. You
294 /// have implicit, or fully elided, references to lifetimes, like the
295 /// one in `&T` or `Ref<T>`, and you have `'_` lifetimes, like `&'_ T`
296 /// or `Ref<'_, T>`. These often behave the same, but not always:
298 /// - certain usages of implicit references are deprecated, like
299 /// `Ref<T>`, and we sometimes just give hard errors in those cases
301 /// - for object bounds there is a difference: `Box<dyn Foo>` is not
302 /// the same as `Box<dyn Foo + '_>`.
304 /// We describe the effects of the various modes in terms of three cases:
306 /// - **Modern** -- includes all uses of `'_`, but also the lifetime arg
307 /// of a `&` (e.g., the missing lifetime in something like `&T`)
308 /// - **Dyn Bound** -- if you have something like `Box<dyn Foo>`,
309 /// there is an elided lifetime bound (`Box<dyn Foo + 'X>`). These
310 /// elided bounds follow special rules. Note that this only covers
311 /// cases where *nothing* is written; the `'_` in `Box<dyn Foo +
312 /// '_>` is a case of "modern" elision.
313 /// - **Deprecated** -- this coverse cases like `Ref<T>`, where the lifetime
314 /// parameter to ref is completely elided. `Ref<'_, T>` would be the modern,
315 /// non-deprecated equivalent.
317 /// Currently, the handling of lifetime elision is somewhat spread out
318 /// between HIR lowering and -- as described below -- the
319 /// `resolve_lifetime` module. Often we "fallthrough" to that code by generating
320 /// an "elided" or "underscore" lifetime name. In the future, we probably want to move
321 /// everything into HIR lowering.
322 #[derive(Copy, Clone)]
323 enum AnonymousLifetimeMode {
324 /// For **Modern** cases, create a new anonymous region parameter
325 /// and reference that.
327 /// For **Dyn Bound** cases, pass responsibility to
328 /// `resolve_lifetime` code.
330 /// For **Deprecated** cases, report an error.
333 /// Give a hard error when either `&` or `'_` is written. Used to
334 /// rule out things like `where T: Foo<'_>`. Does not imply an
335 /// error on default object bounds (e.g., `Box<dyn Foo>`).
338 /// Pass responsibility to `resolve_lifetime` code for all cases.
341 /// Used in the return types of `async fn` where there exists
342 /// exactly one argument-position elided lifetime.
344 /// In `async fn`, we lower the arguments types using the `CreateParameter`
345 /// mode, meaning that non-`dyn` elided lifetimes are assigned a fresh name.
346 /// If any corresponding elided lifetimes appear in the output, we need to
347 /// replace them with references to the fresh name assigned to the corresponding
348 /// elided lifetime in the arguments.
350 /// For **Modern cases**, replace the anonymous parameter with a
351 /// reference to a specific freshly-named lifetime that was
352 /// introduced in argument
354 /// For **Dyn Bound** cases, pass responsibility to
355 /// `resole_lifetime` code.
356 Replace(LtReplacement),
359 /// The type of elided lifetime replacement to perform on `async fn` return types.
360 #[derive(Copy, Clone)]
362 /// Fresh name introduced by the single non-dyn elided lifetime
363 /// in the arguments of the async fn.
366 /// There is no single non-dyn elided lifetime because no lifetimes
367 /// appeared in the arguments.
370 /// There is no single non-dyn elided lifetime because multiple
371 /// lifetimes appeared in the arguments.
375 /// Calculates the `LtReplacement` to use for elided lifetimes in the return
376 /// type based on the fresh elided lifetimes introduced in argument position.
377 fn get_elided_lt_replacement(arg_position_lifetimes: &[(Span, ParamName)]) -> LtReplacement {
378 match arg_position_lifetimes {
379 [] => LtReplacement::NoLifetimes,
380 [(_span, param)] => LtReplacement::Some(*param),
381 _ => LtReplacement::MultipleLifetimes,
385 struct ImplTraitTypeIdVisitor<'a> { ids: &'a mut SmallVec<[NodeId; 1]> }
387 impl<'a, 'b> Visitor<'a> for ImplTraitTypeIdVisitor<'b> {
388 fn visit_ty(&mut self, ty: &'a Ty) {
394 TyKind::ImplTrait(id, _) => self.ids.push(id),
397 visit::walk_ty(self, ty);
400 fn visit_path_segment(
403 path_segment: &'v PathSegment,
405 if let Some(ref p) = path_segment.args {
406 if let GenericArgs::Parenthesized(_) = **p {
410 visit::walk_path_segment(self, path_span, path_segment)
414 impl<'a> LoweringContext<'a> {
415 fn lower_crate(mut self, c: &Crate) -> hir::Crate {
416 /// Full-crate AST visitor that inserts into a fresh
417 /// `LoweringContext` any information that may be
418 /// needed from arbitrary locations in the crate,
419 /// e.g., the number of lifetime generic parameters
420 /// declared for every type and trait definition.
421 struct MiscCollector<'tcx, 'interner> {
422 lctx: &'tcx mut LoweringContext<'interner>,
423 hir_id_owner: Option<NodeId>,
426 impl MiscCollector<'_, '_> {
427 fn allocate_use_tree_hir_id_counters(
433 UseTreeKind::Simple(_, id1, id2) => {
434 for &id in &[id1, id2] {
435 self.lctx.resolver.definitions().create_def_with_parent(
442 self.lctx.allocate_hir_id_counter(id);
445 UseTreeKind::Glob => (),
446 UseTreeKind::Nested(ref trees) => {
447 for &(ref use_tree, id) in trees {
448 let hir_id = self.lctx.allocate_hir_id_counter(id);
449 self.allocate_use_tree_hir_id_counters(use_tree, hir_id.owner);
455 fn with_hir_id_owner<F, T>(&mut self, owner: Option<NodeId>, f: F) -> T
457 F: FnOnce(&mut Self) -> T,
459 let old = mem::replace(&mut self.hir_id_owner, owner);
461 self.hir_id_owner = old;
466 impl<'tcx, 'interner> Visitor<'tcx> for MiscCollector<'tcx, 'interner> {
467 fn visit_pat(&mut self, p: &'tcx Pat) {
469 // Doesn't generate a HIR node
470 PatKind::Paren(..) | PatKind::Rest => {},
472 if let Some(owner) = self.hir_id_owner {
473 self.lctx.lower_node_id_with_owner(p.id, owner);
478 visit::walk_pat(self, p)
481 fn visit_item(&mut self, item: &'tcx Item) {
482 let hir_id = self.lctx.allocate_hir_id_counter(item.id);
485 ItemKind::Struct(_, ref generics)
486 | ItemKind::Union(_, ref generics)
487 | ItemKind::Enum(_, ref generics)
488 | ItemKind::TyAlias(_, ref generics)
489 | ItemKind::OpaqueTy(_, ref generics)
490 | ItemKind::Trait(_, _, ref generics, ..) => {
491 let def_id = self.lctx.resolver.definitions().local_def_id(item.id);
495 .filter(|param| match param.kind {
496 ast::GenericParamKind::Lifetime { .. } => true,
500 self.lctx.type_def_lifetime_params.insert(def_id, count);
502 ItemKind::Use(ref use_tree) => {
503 self.allocate_use_tree_hir_id_counters(use_tree, hir_id.owner);
508 self.with_hir_id_owner(Some(item.id), |this| {
509 visit::walk_item(this, item);
513 fn visit_trait_item(&mut self, item: &'tcx TraitItem) {
514 self.lctx.allocate_hir_id_counter(item.id);
517 TraitItemKind::Method(_, None) => {
518 // Ignore patterns in trait methods without bodies
519 self.with_hir_id_owner(None, |this| {
520 visit::walk_trait_item(this, item)
523 _ => self.with_hir_id_owner(Some(item.id), |this| {
524 visit::walk_trait_item(this, item);
529 fn visit_impl_item(&mut self, item: &'tcx ImplItem) {
530 self.lctx.allocate_hir_id_counter(item.id);
531 self.with_hir_id_owner(Some(item.id), |this| {
532 visit::walk_impl_item(this, item);
536 fn visit_foreign_item(&mut self, i: &'tcx ForeignItem) {
537 // Ignore patterns in foreign items
538 self.with_hir_id_owner(None, |this| {
539 visit::walk_foreign_item(this, i)
543 fn visit_ty(&mut self, t: &'tcx Ty) {
545 // Mirrors the case in visit::walk_ty
546 TyKind::BareFn(ref f) => {
552 // Mirrors visit::walk_fn_decl
553 for argument in &f.decl.inputs {
554 // We don't lower the ids of argument patterns
555 self.with_hir_id_owner(None, |this| {
556 this.visit_pat(&argument.pat);
558 self.visit_ty(&argument.ty)
560 self.visit_fn_ret_ty(&f.decl.output)
562 _ => visit::walk_ty(self, t),
567 self.lower_node_id(CRATE_NODE_ID);
568 debug_assert!(self.node_id_to_hir_id[CRATE_NODE_ID] == hir::CRATE_HIR_ID);
570 visit::walk_crate(&mut MiscCollector { lctx: &mut self, hir_id_owner: None }, c);
571 visit::walk_crate(&mut item::ItemLowerer { lctx: &mut self }, c);
573 let module = self.lower_mod(&c.module);
574 let attrs = self.lower_attrs(&c.attrs);
575 let body_ids = body_ids(&self.bodies);
579 .init_node_id_to_hir_id_mapping(self.node_id_to_hir_id);
585 exported_macros: hir::HirVec::from(self.exported_macros),
586 non_exported_macro_attrs: hir::HirVec::from(self.non_exported_macro_attrs),
588 trait_items: self.trait_items,
589 impl_items: self.impl_items,
592 trait_impls: self.trait_impls,
593 modules: self.modules,
597 fn insert_item(&mut self, item: hir::Item) {
598 let id = item.hir_id;
599 // FIXME: Use `debug_asset-rt`.
600 assert_eq!(id.local_id, hir::ItemLocalId::from_u32(0));
601 self.items.insert(id, item);
602 self.modules.get_mut(&self.current_module).unwrap().items.insert(id);
605 fn allocate_hir_id_counter(&mut self, owner: NodeId) -> hir::HirId {
606 // Set up the counter if needed.
607 self.item_local_id_counters.entry(owner).or_insert(0);
608 // Always allocate the first `HirId` for the owner itself.
609 let lowered = self.lower_node_id_with_owner(owner, owner);
610 debug_assert_eq!(lowered.local_id.as_u32(), 0);
614 fn lower_node_id_generic<F>(&mut self, ast_node_id: NodeId, alloc_hir_id: F) -> hir::HirId
616 F: FnOnce(&mut Self) -> hir::HirId,
618 if ast_node_id == DUMMY_NODE_ID {
619 return hir::DUMMY_HIR_ID;
622 let min_size = ast_node_id.as_usize() + 1;
624 if min_size > self.node_id_to_hir_id.len() {
625 self.node_id_to_hir_id.resize(min_size, hir::DUMMY_HIR_ID);
628 let existing_hir_id = self.node_id_to_hir_id[ast_node_id];
630 if existing_hir_id == hir::DUMMY_HIR_ID {
631 // Generate a new `HirId`.
632 let hir_id = alloc_hir_id(self);
633 self.node_id_to_hir_id[ast_node_id] = hir_id;
641 fn with_hir_id_owner<F, T>(&mut self, owner: NodeId, f: F) -> T
643 F: FnOnce(&mut Self) -> T,
645 let counter = self.item_local_id_counters
646 .insert(owner, HIR_ID_COUNTER_LOCKED)
647 .unwrap_or_else(|| panic!("no `item_local_id_counters` entry for {:?}", owner));
648 let def_index = self.resolver.definitions().opt_def_index(owner).unwrap();
649 self.current_hir_id_owner.push((def_index, counter));
651 let (new_def_index, new_counter) = self.current_hir_id_owner.pop().unwrap();
653 debug_assert!(def_index == new_def_index);
654 debug_assert!(new_counter >= counter);
656 let prev = self.item_local_id_counters
657 .insert(owner, new_counter)
659 debug_assert!(prev == HIR_ID_COUNTER_LOCKED);
663 /// This method allocates a new `HirId` for the given `NodeId` and stores it in
664 /// the `LoweringContext`'s `NodeId => HirId` map.
665 /// Take care not to call this method if the resulting `HirId` is then not
666 /// actually used in the HIR, as that would trigger an assertion in the
667 /// `HirIdValidator` later on, which makes sure that all `NodeId`s got mapped
668 /// properly. Calling the method twice with the same `NodeId` is fine though.
669 fn lower_node_id(&mut self, ast_node_id: NodeId) -> hir::HirId {
670 self.lower_node_id_generic(ast_node_id, |this| {
671 let &mut (def_index, ref mut local_id_counter) =
672 this.current_hir_id_owner.last_mut().unwrap();
673 let local_id = *local_id_counter;
674 *local_id_counter += 1;
677 local_id: hir::ItemLocalId::from_u32(local_id),
682 fn lower_node_id_with_owner(&mut self, ast_node_id: NodeId, owner: NodeId) -> hir::HirId {
683 self.lower_node_id_generic(ast_node_id, |this| {
684 let local_id_counter = this
685 .item_local_id_counters
687 .expect("called `lower_node_id_with_owner` before `allocate_hir_id_counter`");
688 let local_id = *local_id_counter;
690 // We want to be sure not to modify the counter in the map while it
691 // is also on the stack. Otherwise we'll get lost updates when writing
692 // back from the stack to the map.
693 debug_assert!(local_id != HIR_ID_COUNTER_LOCKED);
695 *local_id_counter += 1;
699 .opt_def_index(owner)
700 .expect("you forgot to call `create_def_with_parent` or are lowering node-IDs \
701 that do not belong to the current owner");
705 local_id: hir::ItemLocalId::from_u32(local_id),
710 fn next_id(&mut self) -> hir::HirId {
711 self.lower_node_id(self.sess.next_node_id())
714 fn lower_res(&mut self, res: Res<NodeId>) -> Res {
716 self.lower_node_id_generic(id, |_| {
717 panic!("expected node_id to be lowered already for res {:#?}", res)
722 fn expect_full_res(&mut self, id: NodeId) -> Res<NodeId> {
723 self.resolver.get_partial_res(id).map_or(Res::Err, |pr| {
724 if pr.unresolved_segments() != 0 {
725 bug!("path not fully resolved: {:?}", pr);
731 fn expect_full_res_from_use(&mut self, id: NodeId) -> impl Iterator<Item = Res<NodeId>> {
732 self.resolver.get_import_res(id).present_items()
735 fn diagnostic(&self) -> &errors::Handler {
736 self.sess.diagnostic()
739 /// Reuses the span but adds information like the kind of the desugaring and features that are
740 /// allowed inside this span.
741 fn mark_span_with_reason(
743 reason: DesugaringKind,
745 allow_internal_unstable: Option<Lrc<[Symbol]>>,
747 span.fresh_expansion(ExpnId::root(), ExpnInfo {
749 allow_internal_unstable,
750 ..ExpnInfo::default(ExpnKind::Desugaring(reason), span, self.sess.edition())
754 fn with_anonymous_lifetime_mode<R>(
756 anonymous_lifetime_mode: AnonymousLifetimeMode,
757 op: impl FnOnce(&mut Self) -> R,
759 let old_anonymous_lifetime_mode = self.anonymous_lifetime_mode;
760 self.anonymous_lifetime_mode = anonymous_lifetime_mode;
761 let result = op(self);
762 self.anonymous_lifetime_mode = old_anonymous_lifetime_mode;
766 /// Creates a new `hir::GenericParam` for every new lifetime and
767 /// type parameter encountered while evaluating `f`. Definitions
768 /// are created with the parent provided. If no `parent_id` is
769 /// provided, no definitions will be returned.
771 /// Presuming that in-band lifetimes are enabled, then
772 /// `self.anonymous_lifetime_mode` will be updated to match the
773 /// argument while `f` is running (and restored afterwards).
774 fn collect_in_band_defs<T, F>(
777 anonymous_lifetime_mode: AnonymousLifetimeMode,
779 ) -> (Vec<hir::GenericParam>, T)
781 F: FnOnce(&mut LoweringContext<'_>) -> (Vec<hir::GenericParam>, T),
783 assert!(!self.is_collecting_in_band_lifetimes);
784 assert!(self.lifetimes_to_define.is_empty());
785 let old_anonymous_lifetime_mode = self.anonymous_lifetime_mode;
787 self.anonymous_lifetime_mode = anonymous_lifetime_mode;
788 self.is_collecting_in_band_lifetimes = true;
790 let (in_band_ty_params, res) = f(self);
792 self.is_collecting_in_band_lifetimes = false;
793 self.anonymous_lifetime_mode = old_anonymous_lifetime_mode;
795 let lifetimes_to_define = self.lifetimes_to_define.split_off(0);
797 let params = lifetimes_to_define
799 .map(|(span, hir_name)| self.lifetime_to_generic_param(
800 span, hir_name, parent_id.index,
802 .chain(in_band_ty_params.into_iter())
808 /// Converts a lifetime into a new generic parameter.
809 fn lifetime_to_generic_param(
813 parent_index: DefIndex,
814 ) -> hir::GenericParam {
815 let node_id = self.sess.next_node_id();
817 // Get the name we'll use to make the def-path. Note
818 // that collisions are ok here and this shouldn't
819 // really show up for end-user.
820 let (str_name, kind) = match hir_name {
821 ParamName::Plain(ident) => (
822 ident.as_interned_str(),
823 hir::LifetimeParamKind::InBand,
825 ParamName::Fresh(_) => (
826 kw::UnderscoreLifetime.as_interned_str(),
827 hir::LifetimeParamKind::Elided,
829 ParamName::Error => (
830 kw::UnderscoreLifetime.as_interned_str(),
831 hir::LifetimeParamKind::Error,
835 // Add a definition for the in-band lifetime def.
836 self.resolver.definitions().create_def_with_parent(
839 DefPathData::LifetimeNs(str_name),
845 hir_id: self.lower_node_id(node_id),
850 pure_wrt_drop: false,
851 kind: hir::GenericParamKind::Lifetime { kind }
855 /// When there is a reference to some lifetime `'a`, and in-band
856 /// lifetimes are enabled, then we want to push that lifetime into
857 /// the vector of names to define later. In that case, it will get
858 /// added to the appropriate generics.
859 fn maybe_collect_in_band_lifetime(&mut self, ident: Ident) {
860 if !self.is_collecting_in_band_lifetimes {
864 if !self.sess.features_untracked().in_band_lifetimes {
868 if self.in_scope_lifetimes.contains(&ParamName::Plain(ident.modern())) {
872 let hir_name = ParamName::Plain(ident);
874 if self.lifetimes_to_define.iter()
875 .any(|(_, lt_name)| lt_name.modern() == hir_name.modern()) {
879 self.lifetimes_to_define.push((ident.span, hir_name));
882 /// When we have either an elided or `'_` lifetime in an impl
883 /// header, we convert it to an in-band lifetime.
884 fn collect_fresh_in_band_lifetime(&mut self, span: Span) -> ParamName {
885 assert!(self.is_collecting_in_band_lifetimes);
886 let index = self.lifetimes_to_define.len();
887 let hir_name = ParamName::Fresh(index);
888 self.lifetimes_to_define.push((span, hir_name));
892 // Evaluates `f` with the lifetimes in `params` in-scope.
893 // This is used to track which lifetimes have already been defined, and
894 // which are new in-band lifetimes that need to have a definition created
896 fn with_in_scope_lifetime_defs<T, F>(&mut self, params: &[GenericParam], f: F) -> T
898 F: FnOnce(&mut LoweringContext<'_>) -> T,
900 let old_len = self.in_scope_lifetimes.len();
901 let lt_def_names = params.iter().filter_map(|param| match param.kind {
902 GenericParamKind::Lifetime { .. } => Some(ParamName::Plain(param.ident.modern())),
905 self.in_scope_lifetimes.extend(lt_def_names);
909 self.in_scope_lifetimes.truncate(old_len);
913 /// Appends in-band lifetime defs and argument-position `impl
914 /// Trait` defs to the existing set of generics.
916 /// Presuming that in-band lifetimes are enabled, then
917 /// `self.anonymous_lifetime_mode` will be updated to match the
918 /// argument while `f` is running (and restored afterwards).
919 fn add_in_band_defs<F, T>(
923 anonymous_lifetime_mode: AnonymousLifetimeMode,
925 ) -> (hir::Generics, T)
927 F: FnOnce(&mut LoweringContext<'_>, &mut Vec<hir::GenericParam>) -> T,
929 let (in_band_defs, (mut lowered_generics, res)) = self.with_in_scope_lifetime_defs(
932 this.collect_in_band_defs(parent_id, anonymous_lifetime_mode, |this| {
933 let mut params = Vec::new();
934 // Note: it is necessary to lower generics *before* calling `f`.
935 // When lowering `async fn`, there's a final step when lowering
936 // the return type that assumes that all in-scope lifetimes have
937 // already been added to either `in_scope_lifetimes` or
938 // `lifetimes_to_define`. If we swapped the order of these two,
939 // in-band-lifetimes introduced by generics or where-clauses
940 // wouldn't have been added yet.
941 let generics = this.lower_generics(
943 ImplTraitContext::Universal(&mut params),
945 let res = f(this, &mut params);
946 (params, (generics, res))
951 let mut lowered_params: Vec<_> = lowered_generics
957 // FIXME(const_generics): the compiler doesn't always cope with
958 // unsorted generic parameters at the moment, so we make sure
959 // that they're ordered correctly here for now. (When we chain
960 // the `in_band_defs`, we might make the order unsorted.)
961 lowered_params.sort_by_key(|param| {
963 hir::GenericParamKind::Lifetime { .. } => ParamKindOrd::Lifetime,
964 hir::GenericParamKind::Type { .. } => ParamKindOrd::Type,
965 hir::GenericParamKind::Const { .. } => ParamKindOrd::Const,
969 lowered_generics.params = lowered_params.into();
971 (lowered_generics, res)
974 fn with_dyn_type_scope<T, F>(&mut self, in_scope: bool, f: F) -> T
976 F: FnOnce(&mut LoweringContext<'_>) -> T,
978 let was_in_dyn_type = self.is_in_dyn_type;
979 self.is_in_dyn_type = in_scope;
981 let result = f(self);
983 self.is_in_dyn_type = was_in_dyn_type;
988 fn with_new_scopes<T, F>(&mut self, f: F) -> T
990 F: FnOnce(&mut LoweringContext<'_>) -> T,
992 let was_in_loop_condition = self.is_in_loop_condition;
993 self.is_in_loop_condition = false;
995 let catch_scopes = mem::take(&mut self.catch_scopes);
996 let loop_scopes = mem::take(&mut self.loop_scopes);
998 self.catch_scopes = catch_scopes;
999 self.loop_scopes = loop_scopes;
1001 self.is_in_loop_condition = was_in_loop_condition;
1006 fn def_key(&mut self, id: DefId) -> DefKey {
1008 self.resolver.definitions().def_key(id.index)
1010 self.cstore.def_key(id)
1014 fn lower_attrs_extendable(&mut self, attrs: &[Attribute]) -> Vec<Attribute> {
1017 .map(|a| self.lower_attr(a))
1021 fn lower_attrs(&mut self, attrs: &[Attribute]) -> hir::HirVec<Attribute> {
1022 self.lower_attrs_extendable(attrs).into()
1025 fn lower_attr(&mut self, attr: &Attribute) -> Attribute {
1026 // Note that we explicitly do not walk the path. Since we don't really
1027 // lower attributes (we use the AST version) there is nowhere to keep
1028 // the `HirId`s. We don't actually need HIR version of attributes anyway.
1032 path: attr.path.clone(),
1033 tokens: self.lower_token_stream(attr.tokens.clone()),
1034 is_sugared_doc: attr.is_sugared_doc,
1039 fn lower_token_stream(&mut self, tokens: TokenStream) -> TokenStream {
1042 .flat_map(|tree| self.lower_token_tree(tree).into_trees())
1046 fn lower_token_tree(&mut self, tree: TokenTree) -> TokenStream {
1048 TokenTree::Token(token) => self.lower_token(token),
1049 TokenTree::Delimited(span, delim, tts) => TokenTree::Delimited(
1052 self.lower_token_stream(tts),
1057 fn lower_token(&mut self, token: Token) -> TokenStream {
1059 token::Interpolated(nt) => {
1060 let tts = nt.to_tokenstream(&self.sess.parse_sess, token.span);
1061 self.lower_token_stream(tts)
1063 _ => TokenTree::Token(token).into(),
1067 /// Given an associated type constraint like one of these:
1070 /// T: Iterator<Item: Debug>
1072 /// T: Iterator<Item = Debug>
1076 /// returns a `hir::TypeBinding` representing `Item`.
1077 fn lower_assoc_ty_constraint(&mut self,
1078 c: &AssocTyConstraint,
1079 itctx: ImplTraitContext<'_>)
1080 -> hir::TypeBinding {
1081 debug!("lower_assoc_ty_constraint(constraint={:?}, itctx={:?})", c, itctx);
1083 let kind = match c.kind {
1084 AssocTyConstraintKind::Equality { ref ty } => hir::TypeBindingKind::Equality {
1085 ty: self.lower_ty(ty, itctx)
1087 AssocTyConstraintKind::Bound { ref bounds } => {
1088 // Piggy-back on the `impl Trait` context to figure out the correct behavior.
1089 let (desugar_to_impl_trait, itctx) = match itctx {
1090 // We are in the return position:
1092 // fn foo() -> impl Iterator<Item: Debug>
1096 // fn foo() -> impl Iterator<Item = impl Debug>
1097 ImplTraitContext::OpaqueTy(_) => (true, itctx),
1099 // We are in the argument position, but within a dyn type:
1101 // fn foo(x: dyn Iterator<Item: Debug>)
1105 // fn foo(x: dyn Iterator<Item = impl Debug>)
1106 ImplTraitContext::Universal(_) if self.is_in_dyn_type => (true, itctx),
1108 // In `type Foo = dyn Iterator<Item: Debug>` we desugar to
1109 // `type Foo = dyn Iterator<Item = impl Debug>` but we have to override the
1110 // "impl trait context" to permit `impl Debug` in this position (it desugars
1111 // then to an opaque type).
1113 // FIXME: this is only needed until `impl Trait` is allowed in type aliases.
1114 ImplTraitContext::Disallowed(_) if self.is_in_dyn_type =>
1115 (true, ImplTraitContext::OpaqueTy(None)),
1117 // We are in the argument position, but not within a dyn type:
1119 // fn foo(x: impl Iterator<Item: Debug>)
1121 // so we leave it as is and this gets expanded in astconv to a bound like
1122 // `<T as Iterator>::Item: Debug` where `T` is the type parameter for the
1124 _ => (false, itctx),
1127 if desugar_to_impl_trait {
1128 // Desugar `AssocTy: Bounds` into `AssocTy = impl Bounds`. We do this by
1129 // constructing the HIR for `impl bounds...` and then lowering that.
1131 let impl_trait_node_id = self.sess.next_node_id();
1132 let parent_def_index = self.current_hir_id_owner.last().unwrap().0;
1133 self.resolver.definitions().create_def_with_parent(
1136 DefPathData::ImplTrait,
1141 self.with_dyn_type_scope(false, |this| {
1142 let ty = this.lower_ty(
1144 id: this.sess.next_node_id(),
1145 node: TyKind::ImplTrait(impl_trait_node_id, bounds.clone()),
1151 hir::TypeBindingKind::Equality {
1156 // Desugar `AssocTy: Bounds` into a type binding where the
1157 // later desugars into a trait predicate.
1158 let bounds = self.lower_param_bounds(bounds, itctx);
1160 hir::TypeBindingKind::Constraint {
1168 hir_id: self.lower_node_id(c.id),
1175 fn lower_generic_arg(&mut self,
1176 arg: &ast::GenericArg,
1177 itctx: ImplTraitContext<'_>)
1178 -> hir::GenericArg {
1180 ast::GenericArg::Lifetime(lt) => GenericArg::Lifetime(self.lower_lifetime(<)),
1181 ast::GenericArg::Type(ty) => GenericArg::Type(self.lower_ty_direct(&ty, itctx)),
1182 ast::GenericArg::Const(ct) => {
1183 GenericArg::Const(ConstArg {
1184 value: self.lower_anon_const(&ct),
1185 span: ct.value.span,
1191 fn lower_ty(&mut self, t: &Ty, itctx: ImplTraitContext<'_>) -> P<hir::Ty> {
1192 P(self.lower_ty_direct(t, itctx))
1198 qself: &Option<QSelf>,
1200 param_mode: ParamMode,
1201 itctx: ImplTraitContext<'_>
1203 let id = self.lower_node_id(t.id);
1204 let qpath = self.lower_qpath(t.id, qself, path, param_mode, itctx);
1205 let ty = self.ty_path(id, t.span, qpath);
1206 if let hir::TyKind::TraitObject(..) = ty.node {
1207 self.maybe_lint_bare_trait(t.span, t.id, qself.is_none() && path.is_global());
1212 fn lower_ty_direct(&mut self, t: &Ty, mut itctx: ImplTraitContext<'_>) -> hir::Ty {
1213 let kind = match t.node {
1214 TyKind::Infer => hir::TyKind::Infer,
1215 TyKind::Err => hir::TyKind::Err,
1216 TyKind::Slice(ref ty) => hir::TyKind::Slice(self.lower_ty(ty, itctx)),
1217 TyKind::Ptr(ref mt) => hir::TyKind::Ptr(self.lower_mt(mt, itctx)),
1218 TyKind::Rptr(ref region, ref mt) => {
1219 let span = self.sess.source_map().next_point(t.span.shrink_to_lo());
1220 let lifetime = match *region {
1221 Some(ref lt) => self.lower_lifetime(lt),
1222 None => self.elided_ref_lifetime(span),
1224 hir::TyKind::Rptr(lifetime, self.lower_mt(mt, itctx))
1226 TyKind::BareFn(ref f) => self.with_in_scope_lifetime_defs(
1229 this.with_anonymous_lifetime_mode(
1230 AnonymousLifetimeMode::PassThrough,
1232 hir::TyKind::BareFn(P(hir::BareFnTy {
1233 generic_params: this.lower_generic_params(
1235 &NodeMap::default(),
1236 ImplTraitContext::disallowed(),
1238 unsafety: this.lower_unsafety(f.unsafety),
1240 decl: this.lower_fn_decl(&f.decl, None, false, None),
1241 arg_names: this.lower_fn_args_to_names(&f.decl),
1247 TyKind::Never => hir::TyKind::Never,
1248 TyKind::Tup(ref tys) => {
1249 hir::TyKind::Tup(tys.iter().map(|ty| {
1250 self.lower_ty_direct(ty, itctx.reborrow())
1253 TyKind::Paren(ref ty) => {
1254 return self.lower_ty_direct(ty, itctx);
1256 TyKind::Path(ref qself, ref path) => {
1257 return self.lower_path_ty(t, qself, path, ParamMode::Explicit, itctx);
1259 TyKind::ImplicitSelf => {
1260 let res = self.expect_full_res(t.id);
1261 let res = self.lower_res(res);
1262 hir::TyKind::Path(hir::QPath::Resolved(
1266 segments: hir_vec![hir::PathSegment::from_ident(
1267 Ident::with_empty_ctxt(kw::SelfUpper)
1273 TyKind::Array(ref ty, ref length) => {
1274 hir::TyKind::Array(self.lower_ty(ty, itctx), self.lower_anon_const(length))
1276 TyKind::Typeof(ref expr) => {
1277 hir::TyKind::Typeof(self.lower_anon_const(expr))
1279 TyKind::TraitObject(ref bounds, kind) => {
1280 let mut lifetime_bound = None;
1281 let (bounds, lifetime_bound) = self.with_dyn_type_scope(true, |this| {
1284 .filter_map(|bound| match *bound {
1285 GenericBound::Trait(ref ty, TraitBoundModifier::None) => {
1286 Some(this.lower_poly_trait_ref(ty, itctx.reborrow()))
1288 GenericBound::Trait(_, TraitBoundModifier::Maybe) => None,
1289 GenericBound::Outlives(ref lifetime) => {
1290 if lifetime_bound.is_none() {
1291 lifetime_bound = Some(this.lower_lifetime(lifetime));
1297 let lifetime_bound =
1298 lifetime_bound.unwrap_or_else(|| this.elided_dyn_bound(t.span));
1299 (bounds, lifetime_bound)
1301 if kind != TraitObjectSyntax::Dyn {
1302 self.maybe_lint_bare_trait(t.span, t.id, false);
1304 hir::TyKind::TraitObject(bounds, lifetime_bound)
1306 TyKind::ImplTrait(def_node_id, ref bounds) => {
1309 ImplTraitContext::OpaqueTy(fn_def_id) => {
1310 self.lower_opaque_impl_trait(
1311 span, fn_def_id, def_node_id,
1312 |this| this.lower_param_bounds(bounds, itctx),
1315 ImplTraitContext::Universal(in_band_ty_params) => {
1316 // Add a definition for the in-band `Param`.
1317 let def_index = self
1320 .opt_def_index(def_node_id)
1323 let hir_bounds = self.lower_param_bounds(
1325 ImplTraitContext::Universal(in_band_ty_params),
1327 // Set the name to `impl Bound1 + Bound2`.
1328 let ident = Ident::from_str(&pprust::ty_to_string(t)).with_span_pos(span);
1329 in_band_ty_params.push(hir::GenericParam {
1330 hir_id: self.lower_node_id(def_node_id),
1331 name: ParamName::Plain(ident),
1332 pure_wrt_drop: false,
1336 kind: hir::GenericParamKind::Type {
1338 synthetic: Some(hir::SyntheticTyParamKind::ImplTrait),
1342 hir::TyKind::Path(hir::QPath::Resolved(
1346 res: Res::Def(DefKind::TyParam, DefId::local(def_index)),
1347 segments: hir_vec![hir::PathSegment::from_ident(ident)],
1351 ImplTraitContext::Disallowed(pos) => {
1352 let allowed_in = if self.sess.features_untracked()
1353 .impl_trait_in_bindings {
1354 "bindings or function and inherent method return types"
1356 "function and inherent method return types"
1358 let mut err = struct_span_err!(
1362 "`impl Trait` not allowed outside of {}",
1365 if pos == ImplTraitPosition::Binding &&
1366 nightly_options::is_nightly_build() {
1368 "add `#![feature(impl_trait_in_bindings)]` to the crate \
1369 attributes to enable");
1376 TyKind::Mac(_) => bug!("`TyMac` should have been expanded by now."),
1377 TyKind::CVarArgs => {
1378 // Create the implicit lifetime of the "spoofed" `VaListImpl`.
1379 let span = self.sess.source_map().next_point(t.span.shrink_to_lo());
1380 let lt = self.new_implicit_lifetime(span);
1381 hir::TyKind::CVarArgs(lt)
1388 hir_id: self.lower_node_id(t.id),
1392 fn lower_opaque_impl_trait(
1395 fn_def_id: Option<DefId>,
1396 opaque_ty_node_id: NodeId,
1397 lower_bounds: impl FnOnce(&mut LoweringContext<'_>) -> hir::GenericBounds,
1399 // Make sure we know that some funky desugaring has been going on here.
1400 // This is a first: there is code in other places like for loop
1401 // desugaring that explicitly states that we don't want to track that.
1402 // Not tracking it makes lints in rustc and clippy very fragile, as
1403 // frequently opened issues show.
1404 let opaque_ty_span = self.mark_span_with_reason(
1405 DesugaringKind::OpaqueTy,
1410 let opaque_ty_def_index = self
1413 .opt_def_index(opaque_ty_node_id)
1416 self.allocate_hir_id_counter(opaque_ty_node_id);
1418 let hir_bounds = self.with_hir_id_owner(opaque_ty_node_id, lower_bounds);
1420 let (lifetimes, lifetime_defs) = self.lifetimes_from_impl_trait_bounds(
1422 opaque_ty_def_index,
1426 self.with_hir_id_owner(opaque_ty_node_id, |lctx| {
1427 let opaque_ty_item = hir::OpaqueTy {
1428 generics: hir::Generics {
1429 params: lifetime_defs,
1430 where_clause: hir::WhereClause {
1431 predicates: hir_vec![],
1437 impl_trait_fn: fn_def_id,
1438 origin: hir::OpaqueTyOrigin::FnReturn,
1441 trace!("exist ty from impl trait def-index: {:#?}", opaque_ty_def_index);
1442 let opaque_ty_id = lctx.generate_opaque_type(
1449 // `impl Trait` now just becomes `Foo<'a, 'b, ..>`.
1450 hir::TyKind::Def(hir::ItemId { id: opaque_ty_id }, lifetimes)
1454 /// Registers a new opaque type with the proper `NodeId`s and
1455 /// returns the lowered node-ID for the opaque type.
1456 fn generate_opaque_type(
1458 opaque_ty_node_id: NodeId,
1459 opaque_ty_item: hir::OpaqueTy,
1461 opaque_ty_span: Span,
1463 let opaque_ty_item_kind = hir::ItemKind::OpaqueTy(opaque_ty_item);
1464 let opaque_ty_id = self.lower_node_id(opaque_ty_node_id);
1465 // Generate an `type Foo = impl Trait;` declaration.
1466 trace!("registering opaque type with id {:#?}", opaque_ty_id);
1467 let opaque_ty_item = hir::Item {
1468 hir_id: opaque_ty_id,
1469 ident: Ident::invalid(),
1470 attrs: Default::default(),
1471 node: opaque_ty_item_kind,
1472 vis: respan(span.shrink_to_lo(), hir::VisibilityKind::Inherited),
1473 span: opaque_ty_span,
1476 // Insert the item into the global item list. This usually happens
1477 // automatically for all AST items. But this opaque type item
1478 // does not actually exist in the AST.
1479 self.insert_item(opaque_ty_item);
1483 fn lifetimes_from_impl_trait_bounds(
1485 opaque_ty_id: NodeId,
1486 parent_index: DefIndex,
1487 bounds: &hir::GenericBounds,
1488 ) -> (HirVec<hir::GenericArg>, HirVec<hir::GenericParam>) {
1489 // This visitor walks over `impl Trait` bounds and creates defs for all lifetimes that
1490 // appear in the bounds, excluding lifetimes that are created within the bounds.
1491 // E.g., `'a`, `'b`, but not `'c` in `impl for<'c> SomeTrait<'a, 'b, 'c>`.
1492 struct ImplTraitLifetimeCollector<'r, 'a> {
1493 context: &'r mut LoweringContext<'a>,
1495 opaque_ty_id: NodeId,
1496 collect_elided_lifetimes: bool,
1497 currently_bound_lifetimes: Vec<hir::LifetimeName>,
1498 already_defined_lifetimes: FxHashSet<hir::LifetimeName>,
1499 output_lifetimes: Vec<hir::GenericArg>,
1500 output_lifetime_params: Vec<hir::GenericParam>,
1503 impl<'r, 'a, 'v> hir::intravisit::Visitor<'v> for ImplTraitLifetimeCollector<'r, 'a> {
1504 fn nested_visit_map<'this>(
1506 ) -> hir::intravisit::NestedVisitorMap<'this, 'v> {
1507 hir::intravisit::NestedVisitorMap::None
1510 fn visit_generic_args(&mut self, span: Span, parameters: &'v hir::GenericArgs) {
1511 // Don't collect elided lifetimes used inside of `Fn()` syntax.
1512 if parameters.parenthesized {
1513 let old_collect_elided_lifetimes = self.collect_elided_lifetimes;
1514 self.collect_elided_lifetimes = false;
1515 hir::intravisit::walk_generic_args(self, span, parameters);
1516 self.collect_elided_lifetimes = old_collect_elided_lifetimes;
1518 hir::intravisit::walk_generic_args(self, span, parameters);
1522 fn visit_ty(&mut self, t: &'v hir::Ty) {
1523 // Don't collect elided lifetimes used inside of `fn()` syntax.
1524 if let hir::TyKind::BareFn(_) = t.node {
1525 let old_collect_elided_lifetimes = self.collect_elided_lifetimes;
1526 self.collect_elided_lifetimes = false;
1528 // Record the "stack height" of `for<'a>` lifetime bindings
1529 // to be able to later fully undo their introduction.
1530 let old_len = self.currently_bound_lifetimes.len();
1531 hir::intravisit::walk_ty(self, t);
1532 self.currently_bound_lifetimes.truncate(old_len);
1534 self.collect_elided_lifetimes = old_collect_elided_lifetimes;
1536 hir::intravisit::walk_ty(self, t)
1540 fn visit_poly_trait_ref(
1542 trait_ref: &'v hir::PolyTraitRef,
1543 modifier: hir::TraitBoundModifier,
1545 // Record the "stack height" of `for<'a>` lifetime bindings
1546 // to be able to later fully undo their introduction.
1547 let old_len = self.currently_bound_lifetimes.len();
1548 hir::intravisit::walk_poly_trait_ref(self, trait_ref, modifier);
1549 self.currently_bound_lifetimes.truncate(old_len);
1552 fn visit_generic_param(&mut self, param: &'v hir::GenericParam) {
1553 // Record the introduction of 'a in `for<'a> ...`.
1554 if let hir::GenericParamKind::Lifetime { .. } = param.kind {
1555 // Introduce lifetimes one at a time so that we can handle
1556 // cases like `fn foo<'d>() -> impl for<'a, 'b: 'a, 'c: 'b + 'd>`.
1557 let lt_name = hir::LifetimeName::Param(param.name);
1558 self.currently_bound_lifetimes.push(lt_name);
1561 hir::intravisit::walk_generic_param(self, param);
1564 fn visit_lifetime(&mut self, lifetime: &'v hir::Lifetime) {
1565 let name = match lifetime.name {
1566 hir::LifetimeName::Implicit | hir::LifetimeName::Underscore => {
1567 if self.collect_elided_lifetimes {
1568 // Use `'_` for both implicit and underscore lifetimes in
1569 // `type Foo<'_> = impl SomeTrait<'_>;`.
1570 hir::LifetimeName::Underscore
1575 hir::LifetimeName::Param(_) => lifetime.name,
1576 hir::LifetimeName::Error | hir::LifetimeName::Static => return,
1579 if !self.currently_bound_lifetimes.contains(&name)
1580 && !self.already_defined_lifetimes.contains(&name) {
1581 self.already_defined_lifetimes.insert(name);
1583 self.output_lifetimes.push(hir::GenericArg::Lifetime(hir::Lifetime {
1584 hir_id: self.context.next_id(),
1585 span: lifetime.span,
1589 let def_node_id = self.context.sess.next_node_id();
1591 self.context.lower_node_id_with_owner(def_node_id, self.opaque_ty_id);
1592 self.context.resolver.definitions().create_def_with_parent(
1595 DefPathData::LifetimeNs(name.ident().as_interned_str()),
1599 let (name, kind) = match name {
1600 hir::LifetimeName::Underscore => (
1601 hir::ParamName::Plain(Ident::with_empty_ctxt(kw::UnderscoreLifetime)),
1602 hir::LifetimeParamKind::Elided,
1604 hir::LifetimeName::Param(param_name) => (
1606 hir::LifetimeParamKind::Explicit,
1608 _ => bug!("expected `LifetimeName::Param` or `ParamName::Plain`"),
1611 self.output_lifetime_params.push(hir::GenericParam {
1614 span: lifetime.span,
1615 pure_wrt_drop: false,
1618 kind: hir::GenericParamKind::Lifetime { kind }
1624 let mut lifetime_collector = ImplTraitLifetimeCollector {
1626 parent: parent_index,
1628 collect_elided_lifetimes: true,
1629 currently_bound_lifetimes: Vec::new(),
1630 already_defined_lifetimes: FxHashSet::default(),
1631 output_lifetimes: Vec::new(),
1632 output_lifetime_params: Vec::new(),
1635 for bound in bounds {
1636 hir::intravisit::walk_param_bound(&mut lifetime_collector, &bound);
1640 lifetime_collector.output_lifetimes.into(),
1641 lifetime_collector.output_lifetime_params.into(),
1648 qself: &Option<QSelf>,
1650 param_mode: ParamMode,
1651 mut itctx: ImplTraitContext<'_>,
1653 let qself_position = qself.as_ref().map(|q| q.position);
1654 let qself = qself.as_ref().map(|q| self.lower_ty(&q.ty, itctx.reborrow()));
1656 let partial_res = self.resolver
1657 .get_partial_res(id)
1658 .unwrap_or_else(|| PartialRes::new(Res::Err));
1660 let proj_start = p.segments.len() - partial_res.unresolved_segments();
1661 let path = P(hir::Path {
1662 res: self.lower_res(partial_res.base_res()),
1663 segments: p.segments[..proj_start]
1666 .map(|(i, segment)| {
1667 let param_mode = match (qself_position, param_mode) {
1668 (Some(j), ParamMode::Optional) if i < j => {
1669 // This segment is part of the trait path in a
1670 // qualified path - one of `a`, `b` or `Trait`
1671 // in `<X as a::b::Trait>::T::U::method`.
1677 // Figure out if this is a type/trait segment,
1678 // which may need lifetime elision performed.
1679 let parent_def_id = |this: &mut Self, def_id: DefId| DefId {
1680 krate: def_id.krate,
1681 index: this.def_key(def_id).parent.expect("missing parent"),
1683 let type_def_id = match partial_res.base_res() {
1684 Res::Def(DefKind::AssocTy, def_id) if i + 2 == proj_start => {
1685 Some(parent_def_id(self, def_id))
1687 Res::Def(DefKind::Variant, def_id) if i + 1 == proj_start => {
1688 Some(parent_def_id(self, def_id))
1690 Res::Def(DefKind::Struct, def_id)
1691 | Res::Def(DefKind::Union, def_id)
1692 | Res::Def(DefKind::Enum, def_id)
1693 | Res::Def(DefKind::TyAlias, def_id)
1694 | Res::Def(DefKind::Trait, def_id) if i + 1 == proj_start =>
1700 let parenthesized_generic_args = match partial_res.base_res() {
1701 // `a::b::Trait(Args)`
1702 Res::Def(DefKind::Trait, _)
1703 if i + 1 == proj_start => ParenthesizedGenericArgs::Ok,
1704 // `a::b::Trait(Args)::TraitItem`
1705 Res::Def(DefKind::Method, _)
1706 | Res::Def(DefKind::AssocConst, _)
1707 | Res::Def(DefKind::AssocTy, _)
1708 if i + 2 == proj_start =>
1710 ParenthesizedGenericArgs::Ok
1712 // Avoid duplicated errors.
1713 Res::Err => ParenthesizedGenericArgs::Ok,
1715 Res::Def(DefKind::Struct, _)
1716 | Res::Def(DefKind::Enum, _)
1717 | Res::Def(DefKind::Union, _)
1718 | Res::Def(DefKind::TyAlias, _)
1719 | Res::Def(DefKind::Variant, _) if i + 1 == proj_start =>
1721 ParenthesizedGenericArgs::Err
1723 // A warning for now, for compatibility reasons.
1724 _ => ParenthesizedGenericArgs::Warn,
1727 let num_lifetimes = type_def_id.map_or(0, |def_id| {
1728 if let Some(&n) = self.type_def_lifetime_params.get(&def_id) {
1731 assert!(!def_id.is_local());
1733 self.cstore.item_generics_cloned_untracked(def_id, self.sess);
1734 let n = item_generics.own_counts().lifetimes;
1735 self.type_def_lifetime_params.insert(def_id, n);
1738 self.lower_path_segment(
1743 parenthesized_generic_args,
1752 // Simple case, either no projections, or only fully-qualified.
1753 // E.g., `std::mem::size_of` or `<I as Iterator>::Item`.
1754 if partial_res.unresolved_segments() == 0 {
1755 return hir::QPath::Resolved(qself, path);
1758 // Create the innermost type that we're projecting from.
1759 let mut ty = if path.segments.is_empty() {
1760 // If the base path is empty that means there exists a
1761 // syntactical `Self`, e.g., `&i32` in `<&i32>::clone`.
1762 qself.expect("missing QSelf for <T>::...")
1764 // Otherwise, the base path is an implicit `Self` type path,
1765 // e.g., `Vec` in `Vec::new` or `<I as Iterator>::Item` in
1766 // `<I as Iterator>::Item::default`.
1767 let new_id = self.next_id();
1768 P(self.ty_path(new_id, p.span, hir::QPath::Resolved(qself, path)))
1771 // Anything after the base path are associated "extensions",
1772 // out of which all but the last one are associated types,
1773 // e.g., for `std::vec::Vec::<T>::IntoIter::Item::clone`:
1774 // * base path is `std::vec::Vec<T>`
1775 // * "extensions" are `IntoIter`, `Item` and `clone`
1776 // * type nodes are:
1777 // 1. `std::vec::Vec<T>` (created above)
1778 // 2. `<std::vec::Vec<T>>::IntoIter`
1779 // 3. `<<std::vec::Vec<T>>::IntoIter>::Item`
1780 // * final path is `<<<std::vec::Vec<T>>::IntoIter>::Item>::clone`
1781 for (i, segment) in p.segments.iter().enumerate().skip(proj_start) {
1782 let segment = P(self.lower_path_segment(
1787 ParenthesizedGenericArgs::Warn,
1791 let qpath = hir::QPath::TypeRelative(ty, segment);
1793 // It's finished, return the extension of the right node type.
1794 if i == p.segments.len() - 1 {
1798 // Wrap the associated extension in another type node.
1799 let new_id = self.next_id();
1800 ty = P(self.ty_path(new_id, p.span, qpath));
1803 // We should've returned in the for loop above.
1806 "lower_qpath: no final extension segment in {}..{}",
1812 fn lower_path_extra(
1816 param_mode: ParamMode,
1817 explicit_owner: Option<NodeId>,
1821 segments: p.segments
1824 self.lower_path_segment(
1829 ParenthesizedGenericArgs::Err,
1830 ImplTraitContext::disallowed(),
1839 fn lower_path(&mut self, id: NodeId, p: &Path, param_mode: ParamMode) -> hir::Path {
1840 let res = self.expect_full_res(id);
1841 let res = self.lower_res(res);
1842 self.lower_path_extra(res, p, param_mode, None)
1845 fn lower_path_segment(
1848 segment: &PathSegment,
1849 param_mode: ParamMode,
1850 expected_lifetimes: usize,
1851 parenthesized_generic_args: ParenthesizedGenericArgs,
1852 itctx: ImplTraitContext<'_>,
1853 explicit_owner: Option<NodeId>,
1854 ) -> hir::PathSegment {
1855 let (mut generic_args, infer_args) = if let Some(ref generic_args) = segment.args {
1856 let msg = "parenthesized type parameters may only be used with a `Fn` trait";
1857 match **generic_args {
1858 GenericArgs::AngleBracketed(ref data) => {
1859 self.lower_angle_bracketed_parameter_data(data, param_mode, itctx)
1861 GenericArgs::Parenthesized(ref data) => match parenthesized_generic_args {
1862 ParenthesizedGenericArgs::Ok => self.lower_parenthesized_parameter_data(data),
1863 ParenthesizedGenericArgs::Warn => {
1864 self.sess.buffer_lint(
1865 PARENTHESIZED_PARAMS_IN_TYPES_AND_MODULES,
1870 (hir::GenericArgs::none(), true)
1872 ParenthesizedGenericArgs::Err => {
1873 let mut err = struct_span_err!(self.sess, data.span, E0214, "{}", msg);
1874 err.span_label(data.span, "only `Fn` traits may use parentheses");
1875 if let Ok(snippet) = self.sess.source_map().span_to_snippet(data.span) {
1876 // Do not suggest going from `Trait()` to `Trait<>`
1877 if data.inputs.len() > 0 {
1878 err.span_suggestion(
1880 "use angle brackets instead",
1881 format!("<{}>", &snippet[1..snippet.len() - 1]),
1882 Applicability::MaybeIncorrect,
1888 self.lower_angle_bracketed_parameter_data(
1889 &data.as_angle_bracketed_args(),
1899 self.lower_angle_bracketed_parameter_data(&Default::default(), param_mode, itctx)
1902 let has_lifetimes = generic_args.args.iter().any(|arg| match arg {
1903 GenericArg::Lifetime(_) => true,
1906 let first_generic_span = generic_args.args.iter().map(|a| a.span())
1907 .chain(generic_args.bindings.iter().map(|b| b.span)).next();
1908 if !generic_args.parenthesized && !has_lifetimes {
1910 self.elided_path_lifetimes(path_span, expected_lifetimes)
1912 .map(|lt| GenericArg::Lifetime(lt))
1913 .chain(generic_args.args.into_iter())
1915 if expected_lifetimes > 0 && param_mode == ParamMode::Explicit {
1916 let anon_lt_suggestion = vec!["'_"; expected_lifetimes].join(", ");
1917 let no_non_lt_args = generic_args.args.len() == expected_lifetimes;
1918 let no_bindings = generic_args.bindings.is_empty();
1919 let (incl_angl_brckt, insertion_sp, suggestion) = if no_non_lt_args && no_bindings {
1920 // If there are no (non-implicit) generic args or associated type
1921 // bindings, our suggestion includes the angle brackets.
1922 (true, path_span.shrink_to_hi(), format!("<{}>", anon_lt_suggestion))
1924 // Otherwise (sorry, this is kind of gross) we need to infer the
1925 // place to splice in the `'_, ` from the generics that do exist.
1926 let first_generic_span = first_generic_span
1927 .expect("already checked that non-lifetime args or bindings exist");
1928 (false, first_generic_span.shrink_to_lo(), format!("{}, ", anon_lt_suggestion))
1930 match self.anonymous_lifetime_mode {
1931 // In create-parameter mode we error here because we don't want to support
1932 // deprecated impl elision in new features like impl elision and `async fn`,
1933 // both of which work using the `CreateParameter` mode:
1935 // impl Foo for std::cell::Ref<u32> // note lack of '_
1936 // async fn foo(_: std::cell::Ref<u32>) { ... }
1937 AnonymousLifetimeMode::CreateParameter => {
1938 let mut err = struct_span_err!(
1942 "implicit elided lifetime not allowed here"
1944 crate::lint::builtin::add_elided_lifetime_in_path_suggestion(
1955 AnonymousLifetimeMode::PassThrough |
1956 AnonymousLifetimeMode::ReportError |
1957 AnonymousLifetimeMode::Replace(_) => {
1958 self.sess.buffer_lint_with_diagnostic(
1959 ELIDED_LIFETIMES_IN_PATHS,
1962 "hidden lifetime parameters in types are deprecated",
1963 builtin::BuiltinLintDiagnostics::ElidedLifetimesInPaths(
1976 let res = self.expect_full_res(segment.id);
1977 let id = if let Some(owner) = explicit_owner {
1978 self.lower_node_id_with_owner(segment.id, owner)
1980 self.lower_node_id(segment.id)
1983 "lower_path_segment: ident={:?} original-id={:?} new-id={:?}",
1984 segment.ident, segment.id, id,
1987 hir::PathSegment::new(
1990 Some(self.lower_res(res)),
1996 fn lower_angle_bracketed_parameter_data(
1998 data: &AngleBracketedArgs,
1999 param_mode: ParamMode,
2000 mut itctx: ImplTraitContext<'_>,
2001 ) -> (hir::GenericArgs, bool) {
2002 let &AngleBracketedArgs { ref args, ref constraints, .. } = data;
2003 let has_non_lt_args = args.iter().any(|arg| match arg {
2004 ast::GenericArg::Lifetime(_) => false,
2005 ast::GenericArg::Type(_) => true,
2006 ast::GenericArg::Const(_) => true,
2010 args: args.iter().map(|a| self.lower_generic_arg(a, itctx.reborrow())).collect(),
2011 bindings: constraints.iter()
2012 .map(|b| self.lower_assoc_ty_constraint(b, itctx.reborrow()))
2014 parenthesized: false,
2016 !has_non_lt_args && param_mode == ParamMode::Optional
2020 fn lower_parenthesized_parameter_data(
2022 data: &ParenthesizedArgs,
2023 ) -> (hir::GenericArgs, bool) {
2024 // Switch to `PassThrough` mode for anonymous lifetimes; this
2025 // means that we permit things like `&Ref<T>`, where `Ref` has
2026 // a hidden lifetime parameter. This is needed for backwards
2027 // compatibility, even in contexts like an impl header where
2028 // we generally don't permit such things (see #51008).
2029 self.with_anonymous_lifetime_mode(
2030 AnonymousLifetimeMode::PassThrough,
2032 let &ParenthesizedArgs { ref inputs, ref output, span } = data;
2035 .map(|ty| this.lower_ty_direct(ty, ImplTraitContext::disallowed()))
2037 let mk_tup = |this: &mut Self, tys, span| {
2038 hir::Ty { node: hir::TyKind::Tup(tys), hir_id: this.next_id(), span }
2042 args: hir_vec![GenericArg::Type(mk_tup(this, inputs, span))],
2045 hir_id: this.next_id(),
2046 ident: Ident::with_empty_ctxt(FN_OUTPUT_NAME),
2047 kind: hir::TypeBindingKind::Equality {
2050 .map(|ty| this.lower_ty(
2052 ImplTraitContext::disallowed()
2055 P(mk_tup(this, hir::HirVec::new(), span))
2058 span: output.as_ref().map_or(span, |ty| ty.span),
2061 parenthesized: true,
2069 fn lower_local(&mut self, l: &Local) -> (hir::Local, SmallVec<[NodeId; 1]>) {
2070 let mut ids = SmallVec::<[NodeId; 1]>::new();
2071 if self.sess.features_untracked().impl_trait_in_bindings {
2072 if let Some(ref ty) = l.ty {
2073 let mut visitor = ImplTraitTypeIdVisitor { ids: &mut ids };
2074 visitor.visit_ty(ty);
2077 let parent_def_id = DefId::local(self.current_hir_id_owner.last().unwrap().0);
2079 hir_id: self.lower_node_id(l.id),
2082 .map(|t| self.lower_ty(t,
2083 if self.sess.features_untracked().impl_trait_in_bindings {
2084 ImplTraitContext::OpaqueTy(Some(parent_def_id))
2086 ImplTraitContext::Disallowed(ImplTraitPosition::Binding)
2089 pat: self.lower_pat(&l.pat),
2090 init: l.init.as_ref().map(|e| P(self.lower_expr(e))),
2092 attrs: l.attrs.clone(),
2093 source: hir::LocalSource::Normal,
2097 fn lower_mutability(&mut self, m: Mutability) -> hir::Mutability {
2099 Mutability::Mutable => hir::MutMutable,
2100 Mutability::Immutable => hir::MutImmutable,
2104 fn lower_fn_args_to_names(&mut self, decl: &FnDecl) -> hir::HirVec<Ident> {
2107 .map(|arg| match arg.pat.node {
2108 PatKind::Ident(_, ident, _) => ident,
2109 _ => Ident::new(kw::Invalid, arg.pat.span),
2114 // Lowers a function declaration.
2116 // `decl`: the unlowered (AST) function declaration.
2117 // `fn_def_id`: if `Some`, impl Trait arguments are lowered into generic parameters on the
2118 // given DefId, otherwise impl Trait is disallowed. Must be `Some` if
2119 // `make_ret_async` is also `Some`.
2120 // `impl_trait_return_allow`: determines whether `impl Trait` can be used in return position.
2121 // This guards against trait declarations and implementations where `impl Trait` is
2123 // `make_ret_async`: if `Some`, converts `-> T` into `-> impl Future<Output = T>` in the
2124 // return type. This is used for `async fn` declarations. The `NodeId` is the ID of the
2125 // return type `impl Trait` item.
2129 mut in_band_ty_params: Option<(DefId, &mut Vec<hir::GenericParam>)>,
2130 impl_trait_return_allow: bool,
2131 make_ret_async: Option<NodeId>,
2132 ) -> P<hir::FnDecl> {
2133 let lt_mode = if make_ret_async.is_some() {
2134 // In `async fn`, argument-position elided lifetimes
2135 // must be transformed into fresh generic parameters so that
2136 // they can be applied to the opaque `impl Trait` return type.
2137 AnonymousLifetimeMode::CreateParameter
2139 self.anonymous_lifetime_mode
2142 // Remember how many lifetimes were already around so that we can
2143 // only look at the lifetime parameters introduced by the arguments.
2144 let lifetime_count_before_args = self.lifetimes_to_define.len();
2145 let inputs = self.with_anonymous_lifetime_mode(lt_mode, |this| {
2149 if let Some((_, ibty)) = &mut in_band_ty_params {
2150 this.lower_ty_direct(&arg.ty, ImplTraitContext::Universal(ibty))
2152 this.lower_ty_direct(&arg.ty, ImplTraitContext::disallowed())
2155 .collect::<HirVec<_>>()
2158 let output = if let Some(ret_id) = make_ret_async {
2159 // Calculate the `LtReplacement` to use for any return-position elided
2160 // lifetimes based on the elided lifetime parameters introduced in the args.
2161 let lt_replacement = get_elided_lt_replacement(
2162 &self.lifetimes_to_define[lifetime_count_before_args..]
2164 self.lower_async_fn_ret_ty(
2166 in_band_ty_params.expect("`make_ret_async` but no `fn_def_id`").0,
2172 FunctionRetTy::Ty(ref ty) => match in_band_ty_params {
2173 Some((def_id, _)) if impl_trait_return_allow => {
2174 hir::Return(self.lower_ty(ty,
2175 ImplTraitContext::OpaqueTy(Some(def_id))
2179 hir::Return(self.lower_ty(ty, ImplTraitContext::disallowed()))
2182 FunctionRetTy::Default(span) => hir::DefaultReturn(span),
2189 c_variadic: decl.c_variadic,
2190 implicit_self: decl.inputs.get(0).map_or(
2191 hir::ImplicitSelfKind::None,
2193 let is_mutable_pat = match arg.pat.node {
2194 PatKind::Ident(BindingMode::ByValue(mt), _, _) |
2195 PatKind::Ident(BindingMode::ByRef(mt), _, _) =>
2196 mt == Mutability::Mutable,
2201 TyKind::ImplicitSelf if is_mutable_pat => hir::ImplicitSelfKind::Mut,
2202 TyKind::ImplicitSelf => hir::ImplicitSelfKind::Imm,
2203 // Given we are only considering `ImplicitSelf` types, we needn't consider
2204 // the case where we have a mutable pattern to a reference as that would
2205 // no longer be an `ImplicitSelf`.
2206 TyKind::Rptr(_, ref mt) if mt.ty.node.is_implicit_self() &&
2207 mt.mutbl == ast::Mutability::Mutable =>
2208 hir::ImplicitSelfKind::MutRef,
2209 TyKind::Rptr(_, ref mt) if mt.ty.node.is_implicit_self() =>
2210 hir::ImplicitSelfKind::ImmRef,
2211 _ => hir::ImplicitSelfKind::None,
2218 // Transforms `-> T` for `async fn` into `-> OpaqueTy { .. }`
2219 // combined with the following definition of `OpaqueTy`:
2221 // type OpaqueTy<generics_from_parent_fn> = impl Future<Output = T>;
2223 // `inputs`: lowered types of arguments to the function (used to collect lifetimes)
2224 // `output`: unlowered output type (`T` in `-> T`)
2225 // `fn_def_id`: `DefId` of the parent function (used to create child impl trait definition)
2226 // `opaque_ty_node_id`: `NodeId` of the opaque `impl Trait` type that should be created
2227 // `elided_lt_replacement`: replacement for elided lifetimes in the return type
2228 fn lower_async_fn_ret_ty(
2230 output: &FunctionRetTy,
2232 opaque_ty_node_id: NodeId,
2233 elided_lt_replacement: LtReplacement,
2234 ) -> hir::FunctionRetTy {
2235 let span = output.span();
2237 let opaque_ty_span = self.mark_span_with_reason(
2238 DesugaringKind::Async,
2243 let opaque_ty_def_index = self
2246 .opt_def_index(opaque_ty_node_id)
2249 self.allocate_hir_id_counter(opaque_ty_node_id);
2251 let (opaque_ty_id, lifetime_params) = self.with_hir_id_owner(opaque_ty_node_id, |this| {
2252 let future_bound = this.with_anonymous_lifetime_mode(
2253 AnonymousLifetimeMode::Replace(elided_lt_replacement),
2254 |this| this.lower_async_fn_output_type_to_future_bound(
2261 // Calculate all the lifetimes that should be captured
2262 // by the opaque type. This should include all in-scope
2263 // lifetime parameters, including those defined in-band.
2265 // Note: this must be done after lowering the output type,
2266 // as the output type may introduce new in-band lifetimes.
2267 let lifetime_params: Vec<(Span, ParamName)> =
2268 this.in_scope_lifetimes
2270 .map(|name| (name.ident().span, name))
2271 .chain(this.lifetimes_to_define.iter().cloned())
2274 debug!("lower_async_fn_ret_ty: in_scope_lifetimes={:#?}", this.in_scope_lifetimes);
2275 debug!("lower_async_fn_ret_ty: lifetimes_to_define={:#?}", this.lifetimes_to_define);
2276 debug!("lower_async_fn_ret_ty: lifetime_params={:#?}", lifetime_params);
2278 let generic_params =
2281 .map(|(span, hir_name)| {
2282 this.lifetime_to_generic_param(span, hir_name, opaque_ty_def_index)
2286 let opaque_ty_item = hir::OpaqueTy {
2287 generics: hir::Generics {
2288 params: generic_params,
2289 where_clause: hir::WhereClause {
2290 predicates: hir_vec![],
2295 bounds: hir_vec![future_bound],
2296 impl_trait_fn: Some(fn_def_id),
2297 origin: hir::OpaqueTyOrigin::AsyncFn,
2300 trace!("exist ty from async fn def index: {:#?}", opaque_ty_def_index);
2301 let opaque_ty_id = this.generate_opaque_type(
2308 (opaque_ty_id, lifetime_params)
2314 .map(|(span, hir_name)| {
2315 GenericArg::Lifetime(hir::Lifetime {
2316 hir_id: self.next_id(),
2318 name: hir::LifetimeName::Param(hir_name),
2323 let opaque_ty_ref = hir::TyKind::Def(hir::ItemId { id: opaque_ty_id }, generic_args);
2325 hir::FunctionRetTy::Return(P(hir::Ty {
2326 node: opaque_ty_ref,
2328 hir_id: self.next_id(),
2332 /// Transforms `-> T` into `Future<Output = T>`
2333 fn lower_async_fn_output_type_to_future_bound(
2335 output: &FunctionRetTy,
2338 ) -> hir::GenericBound {
2339 // Compute the `T` in `Future<Output = T>` from the return type.
2340 let output_ty = match output {
2341 FunctionRetTy::Ty(ty) => {
2342 self.lower_ty(ty, ImplTraitContext::OpaqueTy(Some(fn_def_id)))
2344 FunctionRetTy::Default(ret_ty_span) => {
2346 hir_id: self.next_id(),
2347 node: hir::TyKind::Tup(hir_vec![]),
2354 let future_params = P(hir::GenericArgs {
2356 bindings: hir_vec![hir::TypeBinding {
2357 ident: Ident::with_empty_ctxt(FN_OUTPUT_NAME),
2358 kind: hir::TypeBindingKind::Equality {
2361 hir_id: self.next_id(),
2364 parenthesized: false,
2367 // ::std::future::Future<future_params>
2369 P(self.std_path(span, &[sym::future, sym::Future], Some(future_params), false));
2371 hir::GenericBound::Trait(
2373 trait_ref: hir::TraitRef {
2375 hir_ref_id: self.next_id(),
2377 bound_generic_params: hir_vec![],
2380 hir::TraitBoundModifier::None,
2384 fn lower_param_bound(
2387 itctx: ImplTraitContext<'_>,
2388 ) -> hir::GenericBound {
2390 GenericBound::Trait(ref ty, modifier) => {
2391 hir::GenericBound::Trait(
2392 self.lower_poly_trait_ref(ty, itctx),
2393 self.lower_trait_bound_modifier(modifier),
2396 GenericBound::Outlives(ref lifetime) => {
2397 hir::GenericBound::Outlives(self.lower_lifetime(lifetime))
2402 fn lower_lifetime(&mut self, l: &Lifetime) -> hir::Lifetime {
2403 let span = l.ident.span;
2405 ident if ident.name == kw::StaticLifetime =>
2406 self.new_named_lifetime(l.id, span, hir::LifetimeName::Static),
2407 ident if ident.name == kw::UnderscoreLifetime =>
2408 match self.anonymous_lifetime_mode {
2409 AnonymousLifetimeMode::CreateParameter => {
2410 let fresh_name = self.collect_fresh_in_band_lifetime(span);
2411 self.new_named_lifetime(l.id, span, hir::LifetimeName::Param(fresh_name))
2414 AnonymousLifetimeMode::PassThrough => {
2415 self.new_named_lifetime(l.id, span, hir::LifetimeName::Underscore)
2418 AnonymousLifetimeMode::ReportError => self.new_error_lifetime(Some(l.id), span),
2420 AnonymousLifetimeMode::Replace(replacement) => {
2421 let hir_id = self.lower_node_id(l.id);
2422 self.replace_elided_lifetime(hir_id, span, replacement)
2426 self.maybe_collect_in_band_lifetime(ident);
2427 let param_name = ParamName::Plain(ident);
2428 self.new_named_lifetime(l.id, span, hir::LifetimeName::Param(param_name))
2433 fn new_named_lifetime(
2437 name: hir::LifetimeName,
2438 ) -> hir::Lifetime {
2440 hir_id: self.lower_node_id(id),
2446 /// Replace a return-position elided lifetime with the elided lifetime
2447 /// from the arguments.
2448 fn replace_elided_lifetime(
2452 replacement: LtReplacement,
2453 ) -> hir::Lifetime {
2454 let multiple_or_none = match replacement {
2455 LtReplacement::Some(name) => {
2456 return hir::Lifetime {
2459 name: hir::LifetimeName::Param(name),
2462 LtReplacement::MultipleLifetimes => "multiple",
2463 LtReplacement::NoLifetimes => "none",
2466 let mut err = crate::middle::resolve_lifetime::report_missing_lifetime_specifiers(
2472 "return-position elided lifetimes require exactly one \
2473 input-position elided lifetime, found {}.", multiple_or_none));
2476 hir::Lifetime { hir_id, span, name: hir::LifetimeName::Error }
2479 fn lower_generic_params(
2481 params: &[GenericParam],
2482 add_bounds: &NodeMap<Vec<GenericBound>>,
2483 mut itctx: ImplTraitContext<'_>,
2484 ) -> hir::HirVec<hir::GenericParam> {
2485 params.iter().map(|param| {
2486 self.lower_generic_param(param, add_bounds, itctx.reborrow())
2490 fn lower_generic_param(&mut self,
2491 param: &GenericParam,
2492 add_bounds: &NodeMap<Vec<GenericBound>>,
2493 mut itctx: ImplTraitContext<'_>)
2494 -> hir::GenericParam {
2495 let mut bounds = self.with_anonymous_lifetime_mode(
2496 AnonymousLifetimeMode::ReportError,
2497 |this| this.lower_param_bounds(¶m.bounds, itctx.reborrow()),
2500 let (name, kind) = match param.kind {
2501 GenericParamKind::Lifetime => {
2502 let was_collecting_in_band = self.is_collecting_in_band_lifetimes;
2503 self.is_collecting_in_band_lifetimes = false;
2505 let lt = self.with_anonymous_lifetime_mode(
2506 AnonymousLifetimeMode::ReportError,
2507 |this| this.lower_lifetime(&Lifetime { id: param.id, ident: param.ident }),
2509 let param_name = match lt.name {
2510 hir::LifetimeName::Param(param_name) => param_name,
2511 hir::LifetimeName::Implicit
2512 | hir::LifetimeName::Underscore
2513 | hir::LifetimeName::Static => hir::ParamName::Plain(lt.name.ident()),
2514 hir::LifetimeName::Error => ParamName::Error,
2517 let kind = hir::GenericParamKind::Lifetime {
2518 kind: hir::LifetimeParamKind::Explicit
2521 self.is_collecting_in_band_lifetimes = was_collecting_in_band;
2525 GenericParamKind::Type { ref default, .. } => {
2526 // Don't expose `Self` (recovered "keyword used as ident" parse error).
2527 // `rustc::ty` expects `Self` to be only used for a trait's `Self`.
2528 // Instead, use `gensym("Self")` to create a distinct name that looks the same.
2529 let ident = if param.ident.name == kw::SelfUpper {
2530 param.ident.gensym()
2535 let add_bounds = add_bounds.get(¶m.id).map_or(&[][..], |x| &x);
2536 if !add_bounds.is_empty() {
2537 let params = self.lower_param_bounds(add_bounds, itctx.reborrow()).into_iter();
2538 bounds = bounds.into_iter()
2543 let kind = hir::GenericParamKind::Type {
2544 default: default.as_ref().map(|x| {
2545 self.lower_ty(x, ImplTraitContext::OpaqueTy(None))
2547 synthetic: param.attrs.iter()
2548 .filter(|attr| attr.check_name(sym::rustc_synthetic))
2549 .map(|_| hir::SyntheticTyParamKind::ImplTrait)
2553 (hir::ParamName::Plain(ident), kind)
2555 GenericParamKind::Const { ref ty } => {
2556 (hir::ParamName::Plain(param.ident), hir::GenericParamKind::Const {
2557 ty: self.lower_ty(&ty, ImplTraitContext::disallowed()),
2563 hir_id: self.lower_node_id(param.id),
2565 span: param.ident.span,
2566 pure_wrt_drop: attr::contains_name(¶m.attrs, sym::may_dangle),
2567 attrs: self.lower_attrs(¶m.attrs),
2573 fn lower_trait_ref(&mut self, p: &TraitRef, itctx: ImplTraitContext<'_>) -> hir::TraitRef {
2574 let path = match self.lower_qpath(p.ref_id, &None, &p.path, ParamMode::Explicit, itctx) {
2575 hir::QPath::Resolved(None, path) => path,
2576 qpath => bug!("lower_trait_ref: unexpected QPath `{:?}`", qpath),
2580 hir_ref_id: self.lower_node_id(p.ref_id),
2584 fn lower_poly_trait_ref(
2587 mut itctx: ImplTraitContext<'_>,
2588 ) -> hir::PolyTraitRef {
2589 let bound_generic_params = self.lower_generic_params(
2590 &p.bound_generic_params,
2591 &NodeMap::default(),
2594 let trait_ref = self.with_in_scope_lifetime_defs(
2595 &p.bound_generic_params,
2596 |this| this.lower_trait_ref(&p.trait_ref, itctx),
2600 bound_generic_params,
2606 fn lower_mt(&mut self, mt: &MutTy, itctx: ImplTraitContext<'_>) -> hir::MutTy {
2608 ty: self.lower_ty(&mt.ty, itctx),
2609 mutbl: self.lower_mutability(mt.mutbl),
2613 fn lower_param_bounds(&mut self, bounds: &[GenericBound], mut itctx: ImplTraitContext<'_>)
2614 -> hir::GenericBounds {
2615 bounds.iter().map(|bound| self.lower_param_bound(bound, itctx.reborrow())).collect()
2618 fn lower_block_with_stmts(
2621 targeted_by_break: bool,
2622 mut stmts: Vec<hir::Stmt>,
2623 ) -> P<hir::Block> {
2624 let mut expr = None;
2626 for (index, stmt) in b.stmts.iter().enumerate() {
2627 if index == b.stmts.len() - 1 {
2628 if let StmtKind::Expr(ref e) = stmt.node {
2629 expr = Some(P(self.lower_expr(e)));
2631 stmts.extend(self.lower_stmt(stmt));
2634 stmts.extend(self.lower_stmt(stmt));
2639 hir_id: self.lower_node_id(b.id),
2640 stmts: stmts.into(),
2642 rules: self.lower_block_check_mode(&b.rules),
2648 fn lower_block(&mut self, b: &Block, targeted_by_break: bool) -> P<hir::Block> {
2649 self.lower_block_with_stmts(b, targeted_by_break, vec![])
2652 fn lower_pat(&mut self, p: &Pat) -> P<hir::Pat> {
2653 let node = match p.node {
2654 PatKind::Wild => hir::PatKind::Wild,
2655 PatKind::Ident(ref binding_mode, ident, ref sub) => {
2656 let lower_sub = |this: &mut Self| sub.as_ref().map(|x| this.lower_pat(x));
2657 self.lower_pat_ident(p, binding_mode, ident, lower_sub)
2659 PatKind::Lit(ref e) => hir::PatKind::Lit(P(self.lower_expr(e))),
2660 PatKind::TupleStruct(ref path, ref pats) => {
2661 let qpath = self.lower_qpath(
2665 ParamMode::Optional,
2666 ImplTraitContext::disallowed(),
2668 let (pats, ddpos) = self.lower_pat_tuple(pats, "tuple struct");
2669 hir::PatKind::TupleStruct(qpath, pats, ddpos)
2671 PatKind::Path(ref qself, ref path) => {
2672 let qpath = self.lower_qpath(
2676 ParamMode::Optional,
2677 ImplTraitContext::disallowed(),
2679 hir::PatKind::Path(qpath)
2681 PatKind::Struct(ref path, ref fields, etc) => {
2682 let qpath = self.lower_qpath(
2686 ParamMode::Optional,
2687 ImplTraitContext::disallowed(),
2695 node: hir::FieldPat {
2696 hir_id: self.next_id(),
2697 ident: f.node.ident,
2698 pat: self.lower_pat(&f.node.pat),
2699 is_shorthand: f.node.is_shorthand,
2704 hir::PatKind::Struct(qpath, fs, etc)
2706 PatKind::Tuple(ref pats) => {
2707 let (pats, ddpos) = self.lower_pat_tuple(pats, "tuple");
2708 hir::PatKind::Tuple(pats, ddpos)
2710 PatKind::Box(ref inner) => hir::PatKind::Box(self.lower_pat(inner)),
2711 PatKind::Ref(ref inner, mutbl) => {
2712 hir::PatKind::Ref(self.lower_pat(inner), self.lower_mutability(mutbl))
2714 PatKind::Range(ref e1, ref e2, Spanned { node: ref end, .. }) => hir::PatKind::Range(
2715 P(self.lower_expr(e1)),
2716 P(self.lower_expr(e2)),
2717 self.lower_range_end(end),
2719 PatKind::Slice(ref pats) => self.lower_pat_slice(pats),
2721 // If we reach here the `..` pattern is not semantically allowed.
2722 self.ban_illegal_rest_pat(p.span)
2724 PatKind::Paren(ref inner) => return self.lower_pat(inner),
2725 PatKind::Mac(_) => panic!("Shouldn't exist here"),
2728 self.pat_with_node_id_of(p, node)
2735 ) -> (HirVec<P<hir::Pat>>, Option<usize>) {
2736 let mut elems = Vec::with_capacity(pats.len());
2737 let mut rest = None;
2739 let mut iter = pats.iter().enumerate();
2740 while let Some((idx, pat)) = iter.next() {
2741 // Interpret the first `..` pattern as a subtuple pattern.
2743 rest = Some((idx, pat.span));
2746 // It was not a subslice pattern so lower it normally.
2747 elems.push(self.lower_pat(pat));
2750 while let Some((_, pat)) = iter.next() {
2751 // There was a previous subtuple pattern; make sure we don't allow more.
2753 self.ban_extra_rest_pat(pat.span, rest.unwrap().1, ctx);
2755 elems.push(self.lower_pat(pat));
2759 (elems.into(), rest.map(|(ddpos, _)| ddpos))
2762 fn lower_pat_slice(&mut self, pats: &[AstP<Pat>]) -> hir::PatKind {
2763 let mut before = Vec::new();
2764 let mut after = Vec::new();
2765 let mut slice = None;
2766 let mut prev_rest_span = None;
2768 let mut iter = pats.iter();
2769 while let Some(pat) = iter.next() {
2770 // Interpret the first `((ref mut?)? x @)? ..` pattern as a subslice pattern.
2773 prev_rest_span = Some(pat.span);
2774 slice = Some(self.pat_wild_with_node_id_of(pat));
2777 PatKind::Ident(ref bm, ident, Some(ref sub)) if sub.is_rest() => {
2778 prev_rest_span = Some(sub.span);
2779 let lower_sub = |this: &mut Self| Some(this.pat_wild_with_node_id_of(sub));
2780 let node = self.lower_pat_ident(pat, bm, ident, lower_sub);
2781 slice = Some(self.pat_with_node_id_of(pat, node));
2787 // It was not a subslice pattern so lower it normally.
2788 before.push(self.lower_pat(pat));
2791 while let Some(pat) = iter.next() {
2792 // There was a previous subslice pattern; make sure we don't allow more.
2793 let rest_span = match pat.node {
2794 PatKind::Rest => Some(pat.span),
2795 PatKind::Ident(.., Some(ref sub)) if sub.is_rest() => {
2796 // The `HirValidator` is merciless; add a `_` pattern to avoid ICEs.
2797 after.push(self.pat_wild_with_node_id_of(pat));
2802 if let Some(rest_span) = rest_span {
2803 self.ban_extra_rest_pat(rest_span, prev_rest_span.unwrap(), "slice");
2805 after.push(self.lower_pat(pat));
2809 hir::PatKind::Slice(before.into(), slice, after.into())
2815 binding_mode: &BindingMode,
2817 lower_sub: impl FnOnce(&mut Self) -> Option<P<hir::Pat>>,
2819 match self.resolver.get_partial_res(p.id).map(|d| d.base_res()) {
2820 // `None` can occur in body-less function signatures
2821 res @ None | res @ Some(Res::Local(_)) => {
2822 let canonical_id = match res {
2823 Some(Res::Local(id)) => id,
2827 hir::PatKind::Binding(
2828 self.lower_binding_mode(binding_mode),
2829 self.lower_node_id(canonical_id),
2834 Some(res) => hir::PatKind::Path(hir::QPath::Resolved(
2838 res: self.lower_res(res),
2839 segments: hir_vec![hir::PathSegment::from_ident(ident)],
2845 fn pat_wild_with_node_id_of(&mut self, p: &Pat) -> P<hir::Pat> {
2846 self.pat_with_node_id_of(p, hir::PatKind::Wild)
2849 /// Construct a `Pat` with the `HirId` of `p.id` lowered.
2850 fn pat_with_node_id_of(&mut self, p: &Pat, node: hir::PatKind) -> P<hir::Pat> {
2852 hir_id: self.lower_node_id(p.id),
2858 /// Emit a friendly error for extra `..` patterns in a tuple/tuple struct/slice pattern.
2859 fn ban_extra_rest_pat(&self, sp: Span, prev_sp: Span, ctx: &str) {
2861 .struct_span_err(sp, &format!("`..` can only be used once per {} pattern", ctx))
2862 .span_label(sp, &format!("can only be used once per {} pattern", ctx))
2863 .span_label(prev_sp, "previously used here")
2867 /// Used to ban the `..` pattern in places it shouldn't be semantically.
2868 fn ban_illegal_rest_pat(&self, sp: Span) -> hir::PatKind {
2870 .struct_span_err(sp, "`..` patterns are not allowed here")
2871 .note("only allowed in tuple, tuple struct, and slice patterns")
2874 // We're not in a list context so `..` can be reasonably treated
2875 // as `_` because it should always be valid and roughly matches the
2876 // intent of `..` (notice that the rest of a single slot is that slot).
2880 fn lower_range_end(&mut self, e: &RangeEnd) -> hir::RangeEnd {
2882 RangeEnd::Included(_) => hir::RangeEnd::Included,
2883 RangeEnd::Excluded => hir::RangeEnd::Excluded,
2887 fn lower_anon_const(&mut self, c: &AnonConst) -> hir::AnonConst {
2888 self.with_new_scopes(|this| {
2890 hir_id: this.lower_node_id(c.id),
2891 body: this.lower_const_body(&c.value),
2896 fn lower_stmt(&mut self, s: &Stmt) -> SmallVec<[hir::Stmt; 1]> {
2897 let node = match s.node {
2898 StmtKind::Local(ref l) => {
2899 let (l, item_ids) = self.lower_local(l);
2900 let mut ids: SmallVec<[hir::Stmt; 1]> = item_ids
2903 let item_id = hir::ItemId { id: self.lower_node_id(item_id) };
2904 self.stmt(s.span, hir::StmtKind::Item(item_id))
2909 hir_id: self.lower_node_id(s.id),
2910 node: hir::StmtKind::Local(P(l)),
2916 StmtKind::Item(ref it) => {
2917 // Can only use the ID once.
2918 let mut id = Some(s.id);
2919 return self.lower_item_id(it)
2922 let hir_id = id.take()
2923 .map(|id| self.lower_node_id(id))
2924 .unwrap_or_else(|| self.next_id());
2928 node: hir::StmtKind::Item(item_id),
2934 StmtKind::Expr(ref e) => hir::StmtKind::Expr(P(self.lower_expr(e))),
2935 StmtKind::Semi(ref e) => hir::StmtKind::Semi(P(self.lower_expr(e))),
2936 StmtKind::Mac(..) => panic!("Shouldn't exist here"),
2938 smallvec![hir::Stmt {
2939 hir_id: self.lower_node_id(s.id),
2945 fn lower_block_check_mode(&mut self, b: &BlockCheckMode) -> hir::BlockCheckMode {
2947 BlockCheckMode::Default => hir::DefaultBlock,
2948 BlockCheckMode::Unsafe(u) => hir::UnsafeBlock(self.lower_unsafe_source(u)),
2952 fn lower_binding_mode(&mut self, b: &BindingMode) -> hir::BindingAnnotation {
2954 BindingMode::ByValue(Mutability::Immutable) => hir::BindingAnnotation::Unannotated,
2955 BindingMode::ByRef(Mutability::Immutable) => hir::BindingAnnotation::Ref,
2956 BindingMode::ByValue(Mutability::Mutable) => hir::BindingAnnotation::Mutable,
2957 BindingMode::ByRef(Mutability::Mutable) => hir::BindingAnnotation::RefMut,
2961 fn lower_unsafe_source(&mut self, u: UnsafeSource) -> hir::UnsafeSource {
2963 CompilerGenerated => hir::CompilerGenerated,
2964 UserProvided => hir::UserProvided,
2968 fn lower_trait_bound_modifier(&mut self, f: TraitBoundModifier) -> hir::TraitBoundModifier {
2970 TraitBoundModifier::None => hir::TraitBoundModifier::None,
2971 TraitBoundModifier::Maybe => hir::TraitBoundModifier::Maybe,
2975 // Helper methods for building HIR.
2977 fn stmt(&mut self, span: Span, node: hir::StmtKind) -> hir::Stmt {
2978 hir::Stmt { span, node, hir_id: self.next_id() }
2981 fn stmt_expr(&mut self, span: Span, expr: hir::Expr) -> hir::Stmt {
2982 self.stmt(span, hir::StmtKind::Expr(P(expr)))
2987 attrs: ThinVec<Attribute>,
2989 init: Option<P<hir::Expr>>,
2991 source: hir::LocalSource,
2993 let local = hir::Local {
2995 hir_id: self.next_id(),
3002 self.stmt(span, hir::StmtKind::Local(P(local)))
3005 fn block_expr(&mut self, expr: P<hir::Expr>) -> hir::Block {
3006 self.block_all(expr.span, hir::HirVec::new(), Some(expr))
3012 stmts: hir::HirVec<hir::Stmt>,
3013 expr: Option<P<hir::Expr>>,
3018 hir_id: self.next_id(),
3019 rules: hir::DefaultBlock,
3021 targeted_by_break: false,
3025 /// Constructs a `true` or `false` literal pattern.
3026 fn pat_bool(&mut self, span: Span, val: bool) -> P<hir::Pat> {
3027 let expr = self.expr_bool(span, val);
3028 self.pat(span, hir::PatKind::Lit(P(expr)))
3031 fn pat_ok(&mut self, span: Span, pat: P<hir::Pat>) -> P<hir::Pat> {
3032 self.pat_std_enum(span, &[sym::result, sym::Result, sym::Ok], hir_vec![pat])
3035 fn pat_err(&mut self, span: Span, pat: P<hir::Pat>) -> P<hir::Pat> {
3036 self.pat_std_enum(span, &[sym::result, sym::Result, sym::Err], hir_vec![pat])
3039 fn pat_some(&mut self, span: Span, pat: P<hir::Pat>) -> P<hir::Pat> {
3040 self.pat_std_enum(span, &[sym::option, sym::Option, sym::Some], hir_vec![pat])
3043 fn pat_none(&mut self, span: Span) -> P<hir::Pat> {
3044 self.pat_std_enum(span, &[sym::option, sym::Option, sym::None], hir_vec![])
3050 components: &[Symbol],
3051 subpats: hir::HirVec<P<hir::Pat>>,
3053 let path = self.std_path(span, components, None, true);
3054 let qpath = hir::QPath::Resolved(None, P(path));
3055 let pt = if subpats.is_empty() {
3056 hir::PatKind::Path(qpath)
3058 hir::PatKind::TupleStruct(qpath, subpats, None)
3063 fn pat_ident(&mut self, span: Span, ident: Ident) -> (P<hir::Pat>, hir::HirId) {
3064 self.pat_ident_binding_mode(span, ident, hir::BindingAnnotation::Unannotated)
3067 fn pat_ident_binding_mode(
3071 bm: hir::BindingAnnotation,
3072 ) -> (P<hir::Pat>, hir::HirId) {
3073 let hir_id = self.next_id();
3078 node: hir::PatKind::Binding(bm, hir_id, ident.with_span_pos(span), None),
3085 fn pat_wild(&mut self, span: Span) -> P<hir::Pat> {
3086 self.pat(span, hir::PatKind::Wild)
3089 fn pat(&mut self, span: Span, pat: hir::PatKind) -> P<hir::Pat> {
3091 hir_id: self.next_id(),
3097 /// Given a suffix `["b", "c", "d"]`, returns path `::std::b::c::d` when
3098 /// `fld.cx.use_std`, and `::core::b::c::d` otherwise.
3099 /// The path is also resolved according to `is_value`.
3103 components: &[Symbol],
3104 params: Option<P<hir::GenericArgs>>,
3107 let ns = if is_value { Namespace::ValueNS } else { Namespace::TypeNS };
3108 let (path, res) = self.resolver.resolve_str_path(span, self.crate_root, components, ns);
3110 let mut segments: Vec<_> = path.segments.iter().map(|segment| {
3111 let res = self.expect_full_res(segment.id);
3113 ident: segment.ident,
3114 hir_id: Some(self.lower_node_id(segment.id)),
3115 res: Some(self.lower_res(res)),
3120 segments.last_mut().unwrap().args = params;
3124 res: res.map_id(|_| panic!("unexpected node_id")),
3125 segments: segments.into(),
3129 fn ty_path(&mut self, mut hir_id: hir::HirId, span: Span, qpath: hir::QPath) -> hir::Ty {
3130 let node = match qpath {
3131 hir::QPath::Resolved(None, path) => {
3132 // Turn trait object paths into `TyKind::TraitObject` instead.
3134 Res::Def(DefKind::Trait, _) | Res::Def(DefKind::TraitAlias, _) => {
3135 let principal = hir::PolyTraitRef {
3136 bound_generic_params: hir::HirVec::new(),
3137 trait_ref: hir::TraitRef {
3144 // The original ID is taken by the `PolyTraitRef`,
3145 // so the `Ty` itself needs a different one.
3146 hir_id = self.next_id();
3147 hir::TyKind::TraitObject(hir_vec![principal], self.elided_dyn_bound(span))
3149 _ => hir::TyKind::Path(hir::QPath::Resolved(None, path)),
3152 _ => hir::TyKind::Path(qpath),
3161 /// Invoked to create the lifetime argument for a type `&T`
3162 /// with no explicit lifetime.
3163 fn elided_ref_lifetime(&mut self, span: Span) -> hir::Lifetime {
3164 match self.anonymous_lifetime_mode {
3165 // Intercept when we are in an impl header or async fn and introduce an in-band
3167 // Hence `impl Foo for &u32` becomes `impl<'f> Foo for &'f u32` for some fresh
3169 AnonymousLifetimeMode::CreateParameter => {
3170 let fresh_name = self.collect_fresh_in_band_lifetime(span);
3172 hir_id: self.next_id(),
3174 name: hir::LifetimeName::Param(fresh_name),
3178 AnonymousLifetimeMode::ReportError => self.new_error_lifetime(None, span),
3180 AnonymousLifetimeMode::PassThrough => self.new_implicit_lifetime(span),
3182 AnonymousLifetimeMode::Replace(replacement) => {
3183 self.new_replacement_lifetime(replacement, span)
3188 /// Report an error on illegal use of `'_` or a `&T` with no explicit lifetime;
3189 /// return a "error lifetime".
3190 fn new_error_lifetime(&mut self, id: Option<NodeId>, span: Span) -> hir::Lifetime {
3191 let (id, msg, label) = match id {
3192 Some(id) => (id, "`'_` cannot be used here", "`'_` is a reserved lifetime name"),
3195 self.sess.next_node_id(),
3196 "`&` without an explicit lifetime name cannot be used here",
3197 "explicit lifetime name needed here",
3201 let mut err = struct_span_err!(
3208 err.span_label(span, label);
3211 self.new_named_lifetime(id, span, hir::LifetimeName::Error)
3214 /// Invoked to create the lifetime argument(s) for a path like
3215 /// `std::cell::Ref<T>`; note that implicit lifetimes in these
3216 /// sorts of cases are deprecated. This may therefore report a warning or an
3217 /// error, depending on the mode.
3218 fn elided_path_lifetimes(&mut self, span: Span, count: usize) -> P<[hir::Lifetime]> {
3220 .map(|_| self.elided_path_lifetime(span))
3224 fn elided_path_lifetime(&mut self, span: Span) -> hir::Lifetime {
3225 match self.anonymous_lifetime_mode {
3226 AnonymousLifetimeMode::CreateParameter => {
3227 // We should have emitted E0726 when processing this path above
3228 self.sess.delay_span_bug(
3230 "expected 'implicit elided lifetime not allowed' error",
3232 let id = self.sess.next_node_id();
3233 self.new_named_lifetime(id, span, hir::LifetimeName::Error)
3235 // This is the normal case.
3236 AnonymousLifetimeMode::PassThrough => self.new_implicit_lifetime(span),
3238 AnonymousLifetimeMode::Replace(replacement) => {
3239 self.new_replacement_lifetime(replacement, span)
3242 AnonymousLifetimeMode::ReportError => self.new_error_lifetime(None, span),
3246 /// Invoked to create the lifetime argument(s) for an elided trait object
3247 /// bound, like the bound in `Box<dyn Debug>`. This method is not invoked
3248 /// when the bound is written, even if it is written with `'_` like in
3249 /// `Box<dyn Debug + '_>`. In those cases, `lower_lifetime` is invoked.
3250 fn elided_dyn_bound(&mut self, span: Span) -> hir::Lifetime {
3251 match self.anonymous_lifetime_mode {
3252 // NB. We intentionally ignore the create-parameter mode here.
3253 // and instead "pass through" to resolve-lifetimes, which will apply
3254 // the object-lifetime-defaulting rules. Elided object lifetime defaults
3255 // do not act like other elided lifetimes. In other words, given this:
3257 // impl Foo for Box<dyn Debug>
3259 // we do not introduce a fresh `'_` to serve as the bound, but instead
3260 // ultimately translate to the equivalent of:
3262 // impl Foo for Box<dyn Debug + 'static>
3264 // `resolve_lifetime` has the code to make that happen.
3265 AnonymousLifetimeMode::CreateParameter => {}
3267 AnonymousLifetimeMode::ReportError => {
3268 // ReportError applies to explicit use of `'_`.
3271 // This is the normal case.
3272 AnonymousLifetimeMode::PassThrough => {}
3274 // We don't need to do any replacement here as this lifetime
3275 // doesn't refer to an elided lifetime elsewhere in the function
3277 AnonymousLifetimeMode::Replace(_) => {}
3280 self.new_implicit_lifetime(span)
3283 fn new_replacement_lifetime(
3285 replacement: LtReplacement,
3287 ) -> hir::Lifetime {
3288 let hir_id = self.next_id();
3289 self.replace_elided_lifetime(hir_id, span, replacement)
3292 fn new_implicit_lifetime(&mut self, span: Span) -> hir::Lifetime {
3294 hir_id: self.next_id(),
3296 name: hir::LifetimeName::Implicit,
3300 fn maybe_lint_bare_trait(&self, span: Span, id: NodeId, is_global: bool) {
3301 // FIXME(davidtwco): This is a hack to detect macros which produce spans of the
3302 // call site which do not have a macro backtrace. See #61963.
3303 let is_macro_callsite = self.sess.source_map()
3304 .span_to_snippet(span)
3305 .map(|snippet| snippet.starts_with("#["))
3307 if !is_macro_callsite {
3308 self.sess.buffer_lint_with_diagnostic(
3309 builtin::BARE_TRAIT_OBJECTS,
3312 "trait objects without an explicit `dyn` are deprecated",
3313 builtin::BuiltinLintDiagnostics::BareTraitObject(span, is_global),
3319 fn body_ids(bodies: &BTreeMap<hir::BodyId, hir::Body>) -> Vec<hir::BodyId> {
3320 // Sorting by span ensures that we get things in order within a
3321 // file, and also puts the files in a sensible order.
3322 let mut body_ids: Vec<_> = bodies.keys().cloned().collect();
3323 body_ids.sort_by_key(|b| bodies[b].value.span);
3327 /// Checks if the specified expression is a built-in range literal.
3328 /// (See: `LoweringContext::lower_expr()`).
3329 pub fn is_range_literal(sess: &Session, expr: &hir::Expr) -> bool {
3330 use hir::{Path, QPath, ExprKind, TyKind};
3332 // Returns whether the given path represents a (desugared) range,
3333 // either in std or core, i.e. has either a `::std::ops::Range` or
3334 // `::core::ops::Range` prefix.
3335 fn is_range_path(path: &Path) -> bool {
3336 let segs: Vec<_> = path.segments.iter().map(|seg| seg.ident.as_str().to_string()).collect();
3337 let segs: Vec<_> = segs.iter().map(|seg| &**seg).collect();
3339 // "{{root}}" is the equivalent of `::` prefix in `Path`.
3340 if let ["{{root}}", std_core, "ops", range] = segs.as_slice() {
3341 (*std_core == "std" || *std_core == "core") && range.starts_with("Range")
3347 // Check whether a span corresponding to a range expression is a
3348 // range literal, rather than an explicit struct or `new()` call.
3349 fn is_lit(sess: &Session, span: &Span) -> bool {
3350 let source_map = sess.source_map();
3351 let end_point = source_map.end_point(*span);
3353 if let Ok(end_string) = source_map.span_to_snippet(end_point) {
3354 !(end_string.ends_with("}") || end_string.ends_with(")"))
3361 // All built-in range literals but `..=` and `..` desugar to `Struct`s.
3362 ExprKind::Struct(ref qpath, _, _) => {
3363 if let QPath::Resolved(None, ref path) = **qpath {
3364 return is_range_path(&path) && is_lit(sess, &expr.span);
3368 // `..` desugars to its struct path.
3369 ExprKind::Path(QPath::Resolved(None, ref path)) => {
3370 return is_range_path(&path) && is_lit(sess, &expr.span);
3373 // `..=` desugars into `::std::ops::RangeInclusive::new(...)`.
3374 ExprKind::Call(ref func, _) => {
3375 if let ExprKind::Path(QPath::TypeRelative(ref ty, ref segment)) = func.node {
3376 if let TyKind::Path(QPath::Resolved(None, ref path)) = ty.node {
3377 let new_call = segment.ident.as_str() == "new";
3378 return is_range_path(&path) && is_lit(sess, &expr.span) && new_call;