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.
35 use crate::arena::Arena;
36 use crate::dep_graph::DepGraph;
37 use crate::hir::def::{DefKind, Namespace, PartialRes, PerNS, Res};
38 use crate::hir::def_id::{DefId, DefIndex, CRATE_DEF_INDEX};
39 use crate::hir::map::{DefKey, DefPathData, Definitions};
40 use crate::hir::ptr::P;
41 use crate::hir::HirVec;
42 use crate::hir::{self, ParamName};
43 use crate::hir::{ConstArg, GenericArg};
45 use crate::lint::builtin::{self, ELIDED_LIFETIMES_IN_PATHS};
46 use crate::middle::cstore::CrateStore;
47 use crate::session::config::nightly_options;
48 use crate::session::Session;
49 use crate::util::captures::Captures;
50 use crate::util::common::FN_OUTPUT_NAME;
51 use crate::util::nodemap::{DefIdMap, NodeMap};
52 use errors::Applicability;
53 use rustc_data_structures::fx::FxHashSet;
54 use rustc_data_structures::sync::Lrc;
55 use rustc_index::vec::IndexVec;
57 use smallvec::SmallVec;
58 use std::collections::BTreeMap;
64 use syntax::print::pprust;
65 use syntax::ptr::P as AstP;
66 use syntax::sess::ParseSess;
67 use syntax::source_map::{respan, DesugaringKind, ExpnData, ExpnKind, Spanned};
68 use syntax::symbol::{kw, sym, Symbol};
69 use syntax::token::{self, Nonterminal, Token};
70 use syntax::tokenstream::{TokenStream, TokenTree};
71 use syntax::visit::{self, Visitor};
72 use syntax_pos::hygiene::ExpnId;
75 use rustc_error_codes::*;
77 macro_rules! arena_vec {
81 ($this:expr; $($x:expr),*) => (
82 $this.arena.alloc_from_iter(vec![$($x),*])
89 const HIR_ID_COUNTER_LOCKED: u32 = 0xFFFFFFFF;
91 pub struct LoweringContext<'a, 'hir: 'a> {
92 crate_root: Option<Symbol>,
94 /// Used to assign IDs to HIR nodes that do not directly correspond to AST nodes.
97 resolver: &'a mut dyn Resolver,
99 /// HACK(Centril): there is a cyclic dependency between the parser and lowering
100 /// if we don't have this function pointer. To avoid that dependency so that
101 /// librustc is independent of the parser, we use dynamic dispatch here.
102 nt_to_tokenstream: NtToTokenstream,
104 /// Used to allocate HIR nodes
105 arena: &'hir Arena<'hir>,
107 /// The items being lowered are collected here.
108 items: BTreeMap<hir::HirId, hir::Item<'hir>>,
110 trait_items: BTreeMap<hir::TraitItemId, hir::TraitItem<'hir>>,
111 impl_items: BTreeMap<hir::ImplItemId, hir::ImplItem<'hir>>,
112 bodies: BTreeMap<hir::BodyId, hir::Body<'hir>>,
113 exported_macros: Vec<hir::MacroDef<'hir>>,
114 non_exported_macro_attrs: Vec<ast::Attribute>,
116 trait_impls: BTreeMap<DefId, Vec<hir::HirId>>,
118 modules: BTreeMap<hir::HirId, hir::ModuleItems>,
120 generator_kind: Option<hir::GeneratorKind>,
122 /// Used to get the current `fn`'s def span to point to when using `await`
123 /// outside of an `async fn`.
124 current_item: Option<Span>,
126 catch_scopes: Vec<NodeId>,
127 loop_scopes: Vec<NodeId>,
128 is_in_loop_condition: bool,
129 is_in_trait_impl: bool,
130 is_in_dyn_type: bool,
132 /// What to do when we encounter either an "anonymous lifetime
133 /// reference". The term "anonymous" is meant to encompass both
134 /// `'_` lifetimes as well as fully elided cases where nothing is
135 /// written at all (e.g., `&T` or `std::cell::Ref<T>`).
136 anonymous_lifetime_mode: AnonymousLifetimeMode,
138 /// Used to create lifetime definitions from in-band lifetime usages.
139 /// e.g., `fn foo(x: &'x u8) -> &'x u8` to `fn foo<'x>(x: &'x u8) -> &'x u8`
140 /// When a named lifetime is encountered in a function or impl header and
141 /// has not been defined
142 /// (i.e., it doesn't appear in the in_scope_lifetimes list), it is added
143 /// to this list. The results of this list are then added to the list of
144 /// lifetime definitions in the corresponding impl or function generics.
145 lifetimes_to_define: Vec<(Span, ParamName)>,
147 /// `true` if in-band lifetimes are being collected. This is used to
148 /// indicate whether or not we're in a place where new lifetimes will result
149 /// in in-band lifetime definitions, such a function or an impl header,
150 /// including implicit lifetimes from `impl_header_lifetime_elision`.
151 is_collecting_in_band_lifetimes: bool,
153 /// Currently in-scope lifetimes defined in impl headers, fn headers, or HRTB.
154 /// When `is_collectin_in_band_lifetimes` is true, each lifetime is checked
155 /// against this list to see if it is already in-scope, or if a definition
156 /// needs to be created for it.
158 /// We always store a `modern()` version of the param-name in this
160 in_scope_lifetimes: Vec<ParamName>,
162 current_module: hir::HirId,
164 type_def_lifetime_params: DefIdMap<usize>,
166 current_hir_id_owner: Vec<(DefIndex, u32)>,
167 item_local_id_counters: NodeMap<u32>,
168 node_id_to_hir_id: IndexVec<NodeId, hir::HirId>,
170 allow_try_trait: Option<Lrc<[Symbol]>>,
171 allow_gen_future: Option<Lrc<[Symbol]>>,
172 allow_into_future: Option<Lrc<[Symbol]>>,
176 fn cstore(&self) -> &dyn CrateStore;
178 /// Obtains resolution for a `NodeId` with a single resolution.
179 fn get_partial_res(&mut self, id: NodeId) -> Option<PartialRes>;
181 /// Obtains per-namespace resolutions for `use` statement with the given `NodeId`.
182 fn get_import_res(&mut self, id: NodeId) -> PerNS<Option<Res<NodeId>>>;
184 /// Obtains resolution for a label with the given `NodeId`.
185 fn get_label_res(&mut self, id: NodeId) -> Option<NodeId>;
187 /// We must keep the set of definitions up to date as we add nodes that weren't in the AST.
188 /// This should only return `None` during testing.
189 fn definitions(&mut self) -> &mut Definitions;
191 /// Given suffix `["b", "c", "d"]`, creates an AST path for `[::crate_root]::b::c::d` and
192 /// resolves it based on `is_value`.
196 crate_root: Option<Symbol>,
197 components: &[Symbol],
199 ) -> (ast::Path, Res<NodeId>);
201 fn lint_buffer(&mut self) -> &mut lint::LintBuffer;
203 fn next_node_id(&mut self) -> NodeId;
206 type NtToTokenstream = fn(&Nonterminal, &ParseSess, Span) -> TokenStream;
208 /// Context of `impl Trait` in code, which determines whether it is allowed in an HIR subtree,
209 /// and if so, what meaning it has.
211 enum ImplTraitContext<'b, 'a> {
212 /// Treat `impl Trait` as shorthand for a new universal generic parameter.
213 /// Example: `fn foo(x: impl Debug)`, where `impl Debug` is conceptually
214 /// equivalent to a fresh universal parameter like `fn foo<T: Debug>(x: T)`.
216 /// Newly generated parameters should be inserted into the given `Vec`.
217 Universal(&'b mut Vec<hir::GenericParam<'a>>),
219 /// Treat `impl Trait` as shorthand for a new opaque type.
220 /// Example: `fn foo() -> impl Debug`, where `impl Debug` is conceptually
221 /// equivalent to a new opaque type like `type T = impl Debug; fn foo() -> T`.
223 /// We optionally store a `DefId` for the parent item here so we can look up necessary
224 /// information later. It is `None` when no information about the context should be stored
225 /// (e.g., for consts and statics).
226 OpaqueTy(Option<DefId> /* fn def-ID */),
228 /// `impl Trait` is not accepted in this position.
229 Disallowed(ImplTraitPosition),
232 /// Position in which `impl Trait` is disallowed.
233 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
234 enum ImplTraitPosition {
235 /// Disallowed in `let` / `const` / `static` bindings.
238 /// All other posiitons.
242 impl<'b, 'a> ImplTraitContext<'b, 'a> {
244 fn disallowed() -> Self {
245 ImplTraitContext::Disallowed(ImplTraitPosition::Other)
248 fn reborrow(&'c mut self) -> ImplTraitContext<'c, 'a> {
249 use self::ImplTraitContext::*;
251 Universal(params) => Universal(params),
252 OpaqueTy(fn_def_id) => OpaqueTy(*fn_def_id),
253 Disallowed(pos) => Disallowed(*pos),
258 pub fn lower_crate<'a, 'hir>(
260 dep_graph: &'a DepGraph,
262 resolver: &'a mut dyn Resolver,
263 nt_to_tokenstream: NtToTokenstream,
264 arena: &'hir Arena<'hir>,
265 ) -> hir::Crate<'hir> {
266 // We're constructing the HIR here; we don't care what we will
267 // read, since we haven't even constructed the *input* to
269 dep_graph.assert_ignored();
271 let _prof_timer = sess.prof.generic_activity("hir_lowering");
274 crate_root: sess.parse_sess.injected_crate_name.try_get().copied(),
279 items: BTreeMap::new(),
280 trait_items: BTreeMap::new(),
281 impl_items: BTreeMap::new(),
282 bodies: BTreeMap::new(),
283 trait_impls: BTreeMap::new(),
284 modules: BTreeMap::new(),
285 exported_macros: Vec::new(),
286 non_exported_macro_attrs: Vec::new(),
287 catch_scopes: Vec::new(),
288 loop_scopes: Vec::new(),
289 is_in_loop_condition: false,
290 is_in_trait_impl: false,
291 is_in_dyn_type: false,
292 anonymous_lifetime_mode: AnonymousLifetimeMode::PassThrough,
293 type_def_lifetime_params: Default::default(),
294 current_module: hir::CRATE_HIR_ID,
295 current_hir_id_owner: vec![(CRATE_DEF_INDEX, 0)],
296 item_local_id_counters: Default::default(),
297 node_id_to_hir_id: IndexVec::new(),
298 generator_kind: None,
300 lifetimes_to_define: Vec::new(),
301 is_collecting_in_band_lifetimes: false,
302 in_scope_lifetimes: Vec::new(),
303 allow_try_trait: Some([sym::try_trait][..].into()),
304 allow_gen_future: Some([sym::gen_future][..].into()),
305 allow_into_future: Some([sym::into_future][..].into()),
310 #[derive(Copy, Clone, PartialEq)]
312 /// Any path in a type context.
314 /// Path in a type definition, where the anonymous lifetime `'_` is not allowed.
316 /// The `module::Type` in `module::Type::method` in an expression.
320 enum ParenthesizedGenericArgs {
325 /// What to do when we encounter an **anonymous** lifetime
326 /// reference. Anonymous lifetime references come in two flavors. You
327 /// have implicit, or fully elided, references to lifetimes, like the
328 /// one in `&T` or `Ref<T>`, and you have `'_` lifetimes, like `&'_ T`
329 /// or `Ref<'_, T>`. These often behave the same, but not always:
331 /// - certain usages of implicit references are deprecated, like
332 /// `Ref<T>`, and we sometimes just give hard errors in those cases
334 /// - for object bounds there is a difference: `Box<dyn Foo>` is not
335 /// the same as `Box<dyn Foo + '_>`.
337 /// We describe the effects of the various modes in terms of three cases:
339 /// - **Modern** -- includes all uses of `'_`, but also the lifetime arg
340 /// of a `&` (e.g., the missing lifetime in something like `&T`)
341 /// - **Dyn Bound** -- if you have something like `Box<dyn Foo>`,
342 /// there is an elided lifetime bound (`Box<dyn Foo + 'X>`). These
343 /// elided bounds follow special rules. Note that this only covers
344 /// cases where *nothing* is written; the `'_` in `Box<dyn Foo +
345 /// '_>` is a case of "modern" elision.
346 /// - **Deprecated** -- this coverse cases like `Ref<T>`, where the lifetime
347 /// parameter to ref is completely elided. `Ref<'_, T>` would be the modern,
348 /// non-deprecated equivalent.
350 /// Currently, the handling of lifetime elision is somewhat spread out
351 /// between HIR lowering and -- as described below -- the
352 /// `resolve_lifetime` module. Often we "fallthrough" to that code by generating
353 /// an "elided" or "underscore" lifetime name. In the future, we probably want to move
354 /// everything into HIR lowering.
355 #[derive(Copy, Clone, Debug)]
356 enum AnonymousLifetimeMode {
357 /// For **Modern** cases, create a new anonymous region parameter
358 /// and reference that.
360 /// For **Dyn Bound** cases, pass responsibility to
361 /// `resolve_lifetime` code.
363 /// For **Deprecated** cases, report an error.
366 /// Give a hard error when either `&` or `'_` is written. Used to
367 /// rule out things like `where T: Foo<'_>`. Does not imply an
368 /// error on default object bounds (e.g., `Box<dyn Foo>`).
371 /// Pass responsibility to `resolve_lifetime` code for all cases.
375 struct ImplTraitTypeIdVisitor<'a> {
376 ids: &'a mut SmallVec<[NodeId; 1]>,
379 impl<'a, 'b> Visitor<'a> for ImplTraitTypeIdVisitor<'b> {
380 fn visit_ty(&mut self, ty: &'a Ty) {
382 TyKind::Typeof(_) | TyKind::BareFn(_) => return,
384 TyKind::ImplTrait(id, _) => self.ids.push(id),
387 visit::walk_ty(self, ty);
390 fn visit_path_segment(&mut self, path_span: Span, path_segment: &'v PathSegment) {
391 if let Some(ref p) = path_segment.args {
392 if let GenericArgs::Parenthesized(_) = **p {
396 visit::walk_path_segment(self, path_span, path_segment)
400 impl<'a, 'hir> LoweringContext<'a, 'hir> {
401 fn lower_crate(mut self, c: &Crate) -> hir::Crate<'hir> {
402 /// Full-crate AST visitor that inserts into a fresh
403 /// `LoweringContext` any information that may be
404 /// needed from arbitrary locations in the crate,
405 /// e.g., the number of lifetime generic parameters
406 /// declared for every type and trait definition.
407 struct MiscCollector<'tcx, 'lowering, 'hir> {
408 lctx: &'tcx mut LoweringContext<'lowering, 'hir>,
409 hir_id_owner: Option<NodeId>,
412 impl MiscCollector<'_, '_, '_> {
413 fn allocate_use_tree_hir_id_counters(&mut self, tree: &UseTree, owner: DefIndex) {
415 UseTreeKind::Simple(_, id1, id2) => {
416 for &id in &[id1, id2] {
417 self.lctx.resolver.definitions().create_def_with_parent(
424 self.lctx.allocate_hir_id_counter(id);
427 UseTreeKind::Glob => (),
428 UseTreeKind::Nested(ref trees) => {
429 for &(ref use_tree, id) in trees {
430 let hir_id = self.lctx.allocate_hir_id_counter(id);
431 self.allocate_use_tree_hir_id_counters(use_tree, hir_id.owner);
437 fn with_hir_id_owner<F, T>(&mut self, owner: Option<NodeId>, f: F) -> T
439 F: FnOnce(&mut Self) -> T,
441 let old = mem::replace(&mut self.hir_id_owner, owner);
443 self.hir_id_owner = old;
448 impl<'tcx, 'lowering, 'hir> Visitor<'tcx> for MiscCollector<'tcx, 'lowering, 'hir> {
449 fn visit_pat(&mut self, p: &'tcx Pat) {
450 if let PatKind::Paren(..) | PatKind::Rest = p.kind {
451 // Doesn't generate a HIR node
452 } else if let Some(owner) = self.hir_id_owner {
453 self.lctx.lower_node_id_with_owner(p.id, owner);
456 visit::walk_pat(self, p)
459 fn visit_item(&mut self, item: &'tcx Item) {
460 let hir_id = self.lctx.allocate_hir_id_counter(item.id);
463 ItemKind::Struct(_, ref generics)
464 | ItemKind::Union(_, ref generics)
465 | ItemKind::Enum(_, ref generics)
466 | ItemKind::TyAlias(_, ref generics)
467 | ItemKind::Trait(_, _, ref generics, ..) => {
468 let def_id = self.lctx.resolver.definitions().local_def_id(item.id);
472 .filter(|param| match param.kind {
473 ast::GenericParamKind::Lifetime { .. } => true,
477 self.lctx.type_def_lifetime_params.insert(def_id, count);
479 ItemKind::Use(ref use_tree) => {
480 self.allocate_use_tree_hir_id_counters(use_tree, hir_id.owner);
485 self.with_hir_id_owner(Some(item.id), |this| {
486 visit::walk_item(this, item);
490 fn visit_trait_item(&mut self, item: &'tcx AssocItem) {
491 self.lctx.allocate_hir_id_counter(item.id);
494 AssocItemKind::Fn(_, None) => {
495 // Ignore patterns in trait methods without bodies
496 self.with_hir_id_owner(None, |this| visit::walk_trait_item(this, item));
498 _ => self.with_hir_id_owner(Some(item.id), |this| {
499 visit::walk_trait_item(this, item);
504 fn visit_impl_item(&mut self, item: &'tcx AssocItem) {
505 self.lctx.allocate_hir_id_counter(item.id);
506 self.with_hir_id_owner(Some(item.id), |this| {
507 visit::walk_impl_item(this, item);
511 fn visit_foreign_item(&mut self, i: &'tcx ForeignItem) {
512 // Ignore patterns in foreign items
513 self.with_hir_id_owner(None, |this| visit::walk_foreign_item(this, i));
516 fn visit_ty(&mut self, t: &'tcx Ty) {
518 // Mirrors the case in visit::walk_ty
519 TyKind::BareFn(ref f) => {
520 walk_list!(self, visit_generic_param, &f.generic_params);
521 // Mirrors visit::walk_fn_decl
522 for parameter in &f.decl.inputs {
523 // We don't lower the ids of argument patterns
524 self.with_hir_id_owner(None, |this| {
525 this.visit_pat(¶meter.pat);
527 self.visit_ty(¶meter.ty)
529 self.visit_fn_ret_ty(&f.decl.output)
531 _ => visit::walk_ty(self, t),
536 self.lower_node_id(CRATE_NODE_ID);
537 debug_assert!(self.node_id_to_hir_id[CRATE_NODE_ID] == hir::CRATE_HIR_ID);
539 visit::walk_crate(&mut MiscCollector { lctx: &mut self, hir_id_owner: None }, c);
540 visit::walk_crate(&mut item::ItemLowerer { lctx: &mut self }, c);
542 let module = self.lower_mod(&c.module);
543 let attrs = self.arena.alloc_from_iter(self.lower_attrs(&c.attrs).into_iter());
544 let body_ids = body_ids(&self.bodies);
546 self.resolver.definitions().init_node_id_to_hir_id_mapping(self.node_id_to_hir_id);
552 exported_macros: self.arena.alloc_from_iter(self.exported_macros),
553 non_exported_macro_attrs: self.arena.alloc_from_iter(self.non_exported_macro_attrs),
555 trait_items: self.trait_items,
556 impl_items: self.impl_items,
559 trait_impls: self.trait_impls,
560 modules: self.modules,
564 fn insert_item(&mut self, item: hir::Item<'hir>) {
565 let id = item.hir_id;
566 // FIXME: Use `debug_asset-rt`.
567 assert_eq!(id.local_id, hir::ItemLocalId::from_u32(0));
568 self.items.insert(id, item);
569 self.modules.get_mut(&self.current_module).unwrap().items.insert(id);
572 fn allocate_hir_id_counter(&mut self, owner: NodeId) -> hir::HirId {
573 // Set up the counter if needed.
574 self.item_local_id_counters.entry(owner).or_insert(0);
575 // Always allocate the first `HirId` for the owner itself.
576 let lowered = self.lower_node_id_with_owner(owner, owner);
577 debug_assert_eq!(lowered.local_id.as_u32(), 0);
581 fn lower_node_id_generic<F>(&mut self, ast_node_id: NodeId, alloc_hir_id: F) -> hir::HirId
583 F: FnOnce(&mut Self) -> hir::HirId,
585 if ast_node_id == DUMMY_NODE_ID {
586 return hir::DUMMY_HIR_ID;
589 let min_size = ast_node_id.as_usize() + 1;
591 if min_size > self.node_id_to_hir_id.len() {
592 self.node_id_to_hir_id.resize(min_size, hir::DUMMY_HIR_ID);
595 let existing_hir_id = self.node_id_to_hir_id[ast_node_id];
597 if existing_hir_id == hir::DUMMY_HIR_ID {
598 // Generate a new `HirId`.
599 let hir_id = alloc_hir_id(self);
600 self.node_id_to_hir_id[ast_node_id] = hir_id;
608 fn with_hir_id_owner<F, T>(&mut self, owner: NodeId, f: F) -> T
610 F: FnOnce(&mut Self) -> T,
613 .item_local_id_counters
614 .insert(owner, HIR_ID_COUNTER_LOCKED)
615 .unwrap_or_else(|| panic!("no `item_local_id_counters` entry for {:?}", owner));
616 let def_index = self.resolver.definitions().opt_def_index(owner).unwrap();
617 self.current_hir_id_owner.push((def_index, counter));
619 let (new_def_index, new_counter) = self.current_hir_id_owner.pop().unwrap();
621 debug_assert!(def_index == new_def_index);
622 debug_assert!(new_counter >= counter);
624 let prev = self.item_local_id_counters.insert(owner, new_counter).unwrap();
625 debug_assert!(prev == HIR_ID_COUNTER_LOCKED);
629 /// This method allocates a new `HirId` for the given `NodeId` and stores it in
630 /// the `LoweringContext`'s `NodeId => HirId` map.
631 /// Take care not to call this method if the resulting `HirId` is then not
632 /// actually used in the HIR, as that would trigger an assertion in the
633 /// `HirIdValidator` later on, which makes sure that all `NodeId`s got mapped
634 /// properly. Calling the method twice with the same `NodeId` is fine though.
635 fn lower_node_id(&mut self, ast_node_id: NodeId) -> hir::HirId {
636 self.lower_node_id_generic(ast_node_id, |this| {
637 let &mut (def_index, ref mut local_id_counter) =
638 this.current_hir_id_owner.last_mut().unwrap();
639 let local_id = *local_id_counter;
640 *local_id_counter += 1;
641 hir::HirId { owner: def_index, local_id: hir::ItemLocalId::from_u32(local_id) }
645 fn lower_node_id_with_owner(&mut self, ast_node_id: NodeId, owner: NodeId) -> hir::HirId {
646 self.lower_node_id_generic(ast_node_id, |this| {
647 let local_id_counter = this
648 .item_local_id_counters
650 .expect("called `lower_node_id_with_owner` before `allocate_hir_id_counter`");
651 let local_id = *local_id_counter;
653 // We want to be sure not to modify the counter in the map while it
654 // is also on the stack. Otherwise we'll get lost updates when writing
655 // back from the stack to the map.
656 debug_assert!(local_id != HIR_ID_COUNTER_LOCKED);
658 *local_id_counter += 1;
659 let def_index = this.resolver.definitions().opt_def_index(owner).expect(
660 "you forgot to call `create_def_with_parent` or are lowering node-IDs \
661 that do not belong to the current owner",
664 hir::HirId { owner: def_index, local_id: hir::ItemLocalId::from_u32(local_id) }
668 fn next_id(&mut self) -> hir::HirId {
669 let node_id = self.resolver.next_node_id();
670 self.lower_node_id(node_id)
673 fn lower_res(&mut self, res: Res<NodeId>) -> Res {
675 self.lower_node_id_generic(id, |_| {
676 panic!("expected `NodeId` to be lowered already for res {:#?}", res);
681 fn expect_full_res(&mut self, id: NodeId) -> Res<NodeId> {
682 self.resolver.get_partial_res(id).map_or(Res::Err, |pr| {
683 if pr.unresolved_segments() != 0 {
684 bug!("path not fully resolved: {:?}", pr);
690 fn expect_full_res_from_use(&mut self, id: NodeId) -> impl Iterator<Item = Res<NodeId>> {
691 self.resolver.get_import_res(id).present_items()
694 fn diagnostic(&self) -> &errors::Handler {
695 self.sess.diagnostic()
698 /// Reuses the span but adds information like the kind of the desugaring and features that are
699 /// allowed inside this span.
700 fn mark_span_with_reason(
702 reason: DesugaringKind,
704 allow_internal_unstable: Option<Lrc<[Symbol]>>,
706 span.fresh_expansion(ExpnData {
707 allow_internal_unstable,
708 ..ExpnData::default(ExpnKind::Desugaring(reason), span, self.sess.edition())
712 fn with_anonymous_lifetime_mode<R>(
714 anonymous_lifetime_mode: AnonymousLifetimeMode,
715 op: impl FnOnce(&mut Self) -> R,
718 "with_anonymous_lifetime_mode(anonymous_lifetime_mode={:?})",
719 anonymous_lifetime_mode,
721 let old_anonymous_lifetime_mode = self.anonymous_lifetime_mode;
722 self.anonymous_lifetime_mode = anonymous_lifetime_mode;
723 let result = op(self);
724 self.anonymous_lifetime_mode = old_anonymous_lifetime_mode;
726 "with_anonymous_lifetime_mode: restoring anonymous_lifetime_mode={:?}",
727 old_anonymous_lifetime_mode
732 /// Creates a new `hir::GenericParam` for every new lifetime and
733 /// type parameter encountered while evaluating `f`. Definitions
734 /// are created with the parent provided. If no `parent_id` is
735 /// provided, no definitions will be returned.
737 /// Presuming that in-band lifetimes are enabled, then
738 /// `self.anonymous_lifetime_mode` will be updated to match the
739 /// parameter while `f` is running (and restored afterwards).
740 fn collect_in_band_defs<T, F>(
743 anonymous_lifetime_mode: AnonymousLifetimeMode,
745 ) -> (Vec<hir::GenericParam<'hir>>, T)
747 F: FnOnce(&mut Self) -> (Vec<hir::GenericParam<'hir>>, T),
749 assert!(!self.is_collecting_in_band_lifetimes);
750 assert!(self.lifetimes_to_define.is_empty());
751 let old_anonymous_lifetime_mode = self.anonymous_lifetime_mode;
753 self.anonymous_lifetime_mode = anonymous_lifetime_mode;
754 self.is_collecting_in_band_lifetimes = true;
756 let (in_band_ty_params, res) = f(self);
758 self.is_collecting_in_band_lifetimes = false;
759 self.anonymous_lifetime_mode = old_anonymous_lifetime_mode;
761 let lifetimes_to_define = self.lifetimes_to_define.split_off(0);
763 let params = lifetimes_to_define
765 .map(|(span, hir_name)| self.lifetime_to_generic_param(span, hir_name, parent_id.index))
766 .chain(in_band_ty_params.into_iter())
772 /// Converts a lifetime into a new generic parameter.
773 fn lifetime_to_generic_param(
777 parent_index: DefIndex,
778 ) -> hir::GenericParam<'hir> {
779 let node_id = self.resolver.next_node_id();
781 // Get the name we'll use to make the def-path. Note
782 // that collisions are ok here and this shouldn't
783 // really show up for end-user.
784 let (str_name, kind) = match hir_name {
785 ParamName::Plain(ident) => (ident.name, hir::LifetimeParamKind::InBand),
786 ParamName::Fresh(_) => (kw::UnderscoreLifetime, hir::LifetimeParamKind::Elided),
787 ParamName::Error => (kw::UnderscoreLifetime, hir::LifetimeParamKind::Error),
790 // Add a definition for the in-band lifetime def.
791 self.resolver.definitions().create_def_with_parent(
794 DefPathData::LifetimeNs(str_name),
800 hir_id: self.lower_node_id(node_id),
805 pure_wrt_drop: false,
806 kind: hir::GenericParamKind::Lifetime { kind },
810 /// When there is a reference to some lifetime `'a`, and in-band
811 /// lifetimes are enabled, then we want to push that lifetime into
812 /// the vector of names to define later. In that case, it will get
813 /// added to the appropriate generics.
814 fn maybe_collect_in_band_lifetime(&mut self, ident: Ident) {
815 if !self.is_collecting_in_band_lifetimes {
819 if !self.sess.features_untracked().in_band_lifetimes {
823 if self.in_scope_lifetimes.contains(&ParamName::Plain(ident.modern())) {
827 let hir_name = ParamName::Plain(ident);
829 if self.lifetimes_to_define.iter().any(|(_, lt_name)| lt_name.modern() == hir_name.modern())
834 self.lifetimes_to_define.push((ident.span, hir_name));
837 /// When we have either an elided or `'_` lifetime in an impl
838 /// header, we convert it to an in-band lifetime.
839 fn collect_fresh_in_band_lifetime(&mut self, span: Span) -> ParamName {
840 assert!(self.is_collecting_in_band_lifetimes);
841 let index = self.lifetimes_to_define.len() + self.in_scope_lifetimes.len();
842 let hir_name = ParamName::Fresh(index);
843 self.lifetimes_to_define.push((span, hir_name));
847 // Evaluates `f` with the lifetimes in `params` in-scope.
848 // This is used to track which lifetimes have already been defined, and
849 // which are new in-band lifetimes that need to have a definition created
851 fn with_in_scope_lifetime_defs<T, F>(&mut self, params: &[GenericParam], f: F) -> T
853 F: FnOnce(&mut Self) -> T,
855 let old_len = self.in_scope_lifetimes.len();
856 let lt_def_names = params.iter().filter_map(|param| match param.kind {
857 GenericParamKind::Lifetime { .. } => Some(ParamName::Plain(param.ident.modern())),
860 self.in_scope_lifetimes.extend(lt_def_names);
864 self.in_scope_lifetimes.truncate(old_len);
868 /// Appends in-band lifetime defs and argument-position `impl
869 /// Trait` defs to the existing set of generics.
871 /// Presuming that in-band lifetimes are enabled, then
872 /// `self.anonymous_lifetime_mode` will be updated to match the
873 /// parameter while `f` is running (and restored afterwards).
874 fn add_in_band_defs<F, T>(
878 anonymous_lifetime_mode: AnonymousLifetimeMode,
880 ) -> (hir::Generics<'hir>, T)
882 F: FnOnce(&mut Self, &mut Vec<hir::GenericParam<'hir>>) -> T,
884 let (in_band_defs, (mut lowered_generics, res)) =
885 self.with_in_scope_lifetime_defs(&generics.params, |this| {
886 this.collect_in_band_defs(parent_id, anonymous_lifetime_mode, |this| {
887 let mut params = Vec::new();
888 // Note: it is necessary to lower generics *before* calling `f`.
889 // When lowering `async fn`, there's a final step when lowering
890 // the return type that assumes that all in-scope lifetimes have
891 // already been added to either `in_scope_lifetimes` or
892 // `lifetimes_to_define`. If we swapped the order of these two,
893 // in-band-lifetimes introduced by generics or where-clauses
894 // wouldn't have been added yet.
896 this.lower_generics_mut(generics, ImplTraitContext::Universal(&mut params));
897 let res = f(this, &mut params);
898 (params, (generics, res))
902 let mut lowered_params: Vec<_> =
903 lowered_generics.params.into_iter().chain(in_band_defs).collect();
905 // FIXME(const_generics): the compiler doesn't always cope with
906 // unsorted generic parameters at the moment, so we make sure
907 // that they're ordered correctly here for now. (When we chain
908 // the `in_band_defs`, we might make the order unsorted.)
909 lowered_params.sort_by_key(|param| match param.kind {
910 hir::GenericParamKind::Lifetime { .. } => ParamKindOrd::Lifetime,
911 hir::GenericParamKind::Type { .. } => ParamKindOrd::Type,
912 hir::GenericParamKind::Const { .. } => ParamKindOrd::Const,
915 lowered_generics.params = lowered_params.into();
917 let lowered_generics = lowered_generics.into_generics(self.arena);
918 (lowered_generics, res)
921 fn with_dyn_type_scope<T, F>(&mut self, in_scope: bool, f: F) -> T
923 F: FnOnce(&mut Self) -> T,
925 let was_in_dyn_type = self.is_in_dyn_type;
926 self.is_in_dyn_type = in_scope;
928 let result = f(self);
930 self.is_in_dyn_type = was_in_dyn_type;
935 fn with_new_scopes<T, F>(&mut self, f: F) -> T
937 F: FnOnce(&mut Self) -> T,
939 let was_in_loop_condition = self.is_in_loop_condition;
940 self.is_in_loop_condition = false;
942 let catch_scopes = mem::take(&mut self.catch_scopes);
943 let loop_scopes = mem::take(&mut self.loop_scopes);
945 self.catch_scopes = catch_scopes;
946 self.loop_scopes = loop_scopes;
948 self.is_in_loop_condition = was_in_loop_condition;
953 fn def_key(&mut self, id: DefId) -> DefKey {
955 self.resolver.definitions().def_key(id.index)
957 self.resolver.cstore().def_key(id)
961 fn lower_attrs_arena(&mut self, attrs: &[Attribute]) -> &'hir [Attribute] {
962 self.arena.alloc_from_iter(attrs.iter().map(|a| self.lower_attr(a)))
965 fn lower_attrs(&mut self, attrs: &[Attribute]) -> hir::HirVec<Attribute> {
966 attrs.iter().map(|a| self.lower_attr(a)).collect::<Vec<_>>().into()
969 fn lower_attr(&mut self, attr: &Attribute) -> Attribute {
970 // Note that we explicitly do not walk the path. Since we don't really
971 // lower attributes (we use the AST version) there is nowhere to keep
972 // the `HirId`s. We don't actually need HIR version of attributes anyway.
973 let kind = match attr.kind {
974 AttrKind::Normal(ref item) => AttrKind::Normal(AttrItem {
975 path: item.path.clone(),
976 args: self.lower_mac_args(&item.args),
978 AttrKind::DocComment(comment) => AttrKind::DocComment(comment),
981 Attribute { kind, id: attr.id, style: attr.style, span: attr.span }
984 fn lower_mac_args(&mut self, args: &MacArgs) -> MacArgs {
986 MacArgs::Empty => MacArgs::Empty,
987 MacArgs::Delimited(dspan, delim, ref tokens) => {
988 MacArgs::Delimited(dspan, delim, self.lower_token_stream(tokens.clone()))
990 MacArgs::Eq(eq_span, ref tokens) => {
991 MacArgs::Eq(eq_span, self.lower_token_stream(tokens.clone()))
996 fn lower_token_stream(&mut self, tokens: TokenStream) -> TokenStream {
997 tokens.into_trees().flat_map(|tree| self.lower_token_tree(tree).into_trees()).collect()
1000 fn lower_token_tree(&mut self, tree: TokenTree) -> TokenStream {
1002 TokenTree::Token(token) => self.lower_token(token),
1003 TokenTree::Delimited(span, delim, tts) => {
1004 TokenTree::Delimited(span, delim, self.lower_token_stream(tts)).into()
1009 fn lower_token(&mut self, token: Token) -> TokenStream {
1011 token::Interpolated(nt) => {
1012 let tts = (self.nt_to_tokenstream)(&nt, &self.sess.parse_sess, token.span);
1013 self.lower_token_stream(tts)
1015 _ => TokenTree::Token(token).into(),
1019 /// Given an associated type constraint like one of these:
1022 /// T: Iterator<Item: Debug>
1024 /// T: Iterator<Item = Debug>
1028 /// returns a `hir::TypeBinding` representing `Item`.
1029 fn lower_assoc_ty_constraint(
1031 constraint: &AssocTyConstraint,
1032 itctx: ImplTraitContext<'_, 'hir>,
1033 ) -> hir::TypeBinding<'hir> {
1034 debug!("lower_assoc_ty_constraint(constraint={:?}, itctx={:?})", constraint, itctx);
1036 let kind = match constraint.kind {
1037 AssocTyConstraintKind::Equality { ref ty } => {
1038 hir::TypeBindingKind::Equality { ty: self.lower_ty(ty, itctx) }
1040 AssocTyConstraintKind::Bound { ref bounds } => {
1041 // Piggy-back on the `impl Trait` context to figure out the correct behavior.
1042 let (desugar_to_impl_trait, itctx) = match itctx {
1043 // We are in the return position:
1045 // fn foo() -> impl Iterator<Item: Debug>
1049 // fn foo() -> impl Iterator<Item = impl Debug>
1050 ImplTraitContext::OpaqueTy(_) => (true, itctx),
1052 // We are in the argument position, but within a dyn type:
1054 // fn foo(x: dyn Iterator<Item: Debug>)
1058 // fn foo(x: dyn Iterator<Item = impl Debug>)
1059 ImplTraitContext::Universal(_) if self.is_in_dyn_type => (true, itctx),
1061 // In `type Foo = dyn Iterator<Item: Debug>` we desugar to
1062 // `type Foo = dyn Iterator<Item = impl Debug>` but we have to override the
1063 // "impl trait context" to permit `impl Debug` in this position (it desugars
1064 // then to an opaque type).
1066 // FIXME: this is only needed until `impl Trait` is allowed in type aliases.
1067 ImplTraitContext::Disallowed(_) if self.is_in_dyn_type => {
1068 (true, ImplTraitContext::OpaqueTy(None))
1071 // We are in the parameter position, but not within a dyn type:
1073 // fn foo(x: impl Iterator<Item: Debug>)
1075 // so we leave it as is and this gets expanded in astconv to a bound like
1076 // `<T as Iterator>::Item: Debug` where `T` is the type parameter for the
1078 _ => (false, itctx),
1081 if desugar_to_impl_trait {
1082 // Desugar `AssocTy: Bounds` into `AssocTy = impl Bounds`. We do this by
1083 // constructing the HIR for `impl bounds...` and then lowering that.
1085 let impl_trait_node_id = self.resolver.next_node_id();
1086 let parent_def_index = self.current_hir_id_owner.last().unwrap().0;
1087 self.resolver.definitions().create_def_with_parent(
1090 DefPathData::ImplTrait,
1095 self.with_dyn_type_scope(false, |this| {
1096 let node_id = this.resolver.next_node_id();
1097 let ty = this.lower_ty(
1100 kind: TyKind::ImplTrait(impl_trait_node_id, bounds.clone()),
1101 span: constraint.span,
1106 hir::TypeBindingKind::Equality { ty }
1109 // Desugar `AssocTy: Bounds` into a type binding where the
1110 // later desugars into a trait predicate.
1111 let bounds = self.lower_param_bounds(bounds, itctx);
1113 hir::TypeBindingKind::Constraint { bounds }
1119 hir_id: self.lower_node_id(constraint.id),
1120 ident: constraint.ident,
1122 span: constraint.span,
1126 fn lower_generic_arg(
1128 arg: &ast::GenericArg,
1129 itctx: ImplTraitContext<'_, 'hir>,
1130 ) -> hir::GenericArg<'hir> {
1132 ast::GenericArg::Lifetime(lt) => GenericArg::Lifetime(self.lower_lifetime(<)),
1133 ast::GenericArg::Type(ty) => {
1134 // We parse const arguments as path types as we cannot distiguish them durring
1135 // parsing. We try to resolve that ambiguity by attempting resolution in both the
1136 // type and value namespaces. If we resolved the path in the value namespace, we
1137 // transform it into a generic const argument.
1138 if let TyKind::Path(ref qself, ref path) = ty.kind {
1139 if let Some(partial_res) = self.resolver.get_partial_res(ty.id) {
1140 let res = partial_res.base_res();
1141 if !res.matches_ns(Namespace::TypeNS) {
1143 "lower_generic_arg: Lowering type argument as const argument: {:?}",
1147 // Construct a AnonConst where the expr is the "ty"'s path.
1149 let parent_def_index = self.current_hir_id_owner.last().unwrap().0;
1150 let node_id = self.resolver.next_node_id();
1152 // Add a definition for the in-band const def.
1153 self.resolver.definitions().create_def_with_parent(
1156 DefPathData::AnonConst,
1161 let path_expr = Expr {
1163 kind: ExprKind::Path(qself.clone(), path.clone()),
1165 attrs: AttrVec::new(),
1168 let ct = self.with_new_scopes(|this| hir::AnonConst {
1169 hir_id: this.lower_node_id(node_id),
1170 body: this.lower_const_body(path_expr.span, Some(&path_expr)),
1172 return GenericArg::Const(ConstArg { value: ct, span: ty.span });
1176 GenericArg::Type(self.lower_ty_direct(&ty, itctx))
1178 ast::GenericArg::Const(ct) => GenericArg::Const(ConstArg {
1179 value: self.lower_anon_const(&ct),
1180 span: ct.value.span,
1185 fn lower_ty(&mut self, t: &Ty, itctx: ImplTraitContext<'_, 'hir>) -> &'hir hir::Ty<'hir> {
1186 self.arena.alloc(self.lower_ty_direct(t, itctx))
1192 qself: &Option<QSelf>,
1194 param_mode: ParamMode,
1195 itctx: ImplTraitContext<'_, 'hir>,
1196 ) -> hir::Ty<'hir> {
1197 let id = self.lower_node_id(t.id);
1198 let qpath = self.lower_qpath(t.id, qself, path, param_mode, itctx);
1199 let ty = self.ty_path(id, t.span, qpath);
1200 if let hir::TyKind::TraitObject(..) = ty.kind {
1201 self.maybe_lint_bare_trait(t.span, t.id, qself.is_none() && path.is_global());
1206 fn ty(&mut self, span: Span, kind: hir::TyKind<'hir>) -> hir::Ty<'hir> {
1207 hir::Ty { hir_id: self.next_id(), kind, span }
1210 fn ty_tup(&mut self, span: Span, tys: &'hir [hir::Ty<'hir>]) -> hir::Ty<'hir> {
1211 self.ty(span, hir::TyKind::Tup(tys))
1214 fn lower_ty_direct(&mut self, t: &Ty, mut itctx: ImplTraitContext<'_, 'hir>) -> hir::Ty<'hir> {
1215 let kind = match t.kind {
1216 TyKind::Infer => hir::TyKind::Infer,
1217 TyKind::Err => hir::TyKind::Err,
1218 TyKind::Slice(ref ty) => hir::TyKind::Slice(self.lower_ty(ty, itctx)),
1219 TyKind::Ptr(ref mt) => hir::TyKind::Ptr(self.lower_mt(mt, itctx)),
1220 TyKind::Rptr(ref region, ref mt) => {
1221 let span = self.sess.source_map().next_point(t.span.shrink_to_lo());
1222 let lifetime = match *region {
1223 Some(ref lt) => self.lower_lifetime(lt),
1224 None => self.elided_ref_lifetime(span),
1226 hir::TyKind::Rptr(lifetime, self.lower_mt(mt, itctx))
1228 TyKind::BareFn(ref f) => {
1229 self.with_in_scope_lifetime_defs(&f.generic_params, |this| {
1230 this.with_anonymous_lifetime_mode(AnonymousLifetimeMode::PassThrough, |this| {
1231 hir::TyKind::BareFn(this.arena.alloc(hir::BareFnTy {
1232 generic_params: this.lower_generic_params(
1234 &NodeMap::default(),
1235 ImplTraitContext::disallowed(),
1237 unsafety: f.unsafety,
1238 abi: this.lower_extern(f.ext),
1239 decl: this.lower_fn_decl(&f.decl, None, false, None),
1240 param_names: this.arena.alloc_from_iter(
1241 this.lower_fn_params_to_names(&f.decl).into_iter(),
1247 TyKind::Never => hir::TyKind::Never,
1248 TyKind::Tup(ref tys) => {
1249 hir::TyKind::Tup(self.arena.alloc_from_iter(
1250 tys.iter().map(|ty| 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(
1264 self.arena.alloc(hir::Path {
1266 segments: arena_vec![self; hir::PathSegment::from_ident(
1267 Ident::with_dummy_span(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) => hir::TyKind::Typeof(self.lower_anon_const(expr)),
1277 TyKind::TraitObject(ref bounds, kind) => {
1278 let mut lifetime_bound = None;
1279 let (bounds, lifetime_bound) = self.with_dyn_type_scope(true, |this| {
1281 this.arena.alloc_from_iter(bounds.iter().filter_map(
1282 |bound| match *bound {
1283 GenericBound::Trait(ref ty, TraitBoundModifier::None) => {
1284 Some(this.lower_poly_trait_ref(ty, itctx.reborrow()))
1286 GenericBound::Trait(_, TraitBoundModifier::Maybe) => None,
1287 GenericBound::Outlives(ref lifetime) => {
1288 if lifetime_bound.is_none() {
1289 lifetime_bound = Some(this.lower_lifetime(lifetime));
1295 let lifetime_bound =
1296 lifetime_bound.unwrap_or_else(|| this.elided_dyn_bound(t.span));
1297 (bounds, lifetime_bound)
1299 if kind != TraitObjectSyntax::Dyn {
1300 self.maybe_lint_bare_trait(t.span, t.id, false);
1302 hir::TyKind::TraitObject(bounds, lifetime_bound)
1304 TyKind::ImplTrait(def_node_id, ref bounds) => {
1307 ImplTraitContext::OpaqueTy(fn_def_id) => {
1308 self.lower_opaque_impl_trait(span, fn_def_id, def_node_id, |this| {
1309 this.lower_param_bounds(bounds, itctx)
1312 ImplTraitContext::Universal(in_band_ty_params) => {
1313 // Add a definition for the in-band `Param`.
1315 self.resolver.definitions().opt_def_index(def_node_id).unwrap();
1317 let hir_bounds = self.lower_param_bounds(
1319 ImplTraitContext::Universal(in_band_ty_params),
1321 // Set the name to `impl Bound1 + Bound2`.
1322 let ident = Ident::from_str_and_span(&pprust::ty_to_string(t), span);
1323 in_band_ty_params.push(hir::GenericParam {
1324 hir_id: self.lower_node_id(def_node_id),
1325 name: ParamName::Plain(ident),
1326 pure_wrt_drop: false,
1330 kind: hir::GenericParamKind::Type {
1332 synthetic: Some(hir::SyntheticTyParamKind::ImplTrait),
1336 hir::TyKind::Path(hir::QPath::Resolved(
1338 self.arena.alloc(hir::Path {
1340 res: Res::Def(DefKind::TyParam, DefId::local(def_index)),
1341 segments: arena_vec![self; hir::PathSegment::from_ident(ident)],
1345 ImplTraitContext::Disallowed(pos) => {
1346 let allowed_in = if self.sess.features_untracked().impl_trait_in_bindings {
1347 "bindings or function and inherent method return types"
1349 "function and inherent method return types"
1351 let mut err = struct_span_err!(
1355 "`impl Trait` not allowed outside of {}",
1358 if pos == ImplTraitPosition::Binding && nightly_options::is_nightly_build()
1362 "add `#![feature(impl_trait_in_bindings)]` to the crate \
1363 attributes to enable"
1371 TyKind::Mac(_) => bug!("`TyKind::Mac` should have been expanded by now"),
1372 TyKind::CVarArgs => {
1373 self.sess.delay_span_bug(
1375 "`TyKind::CVarArgs` should have been handled elsewhere",
1381 hir::Ty { kind, span: t.span, hir_id: self.lower_node_id(t.id) }
1384 fn lower_opaque_impl_trait(
1387 fn_def_id: Option<DefId>,
1388 opaque_ty_node_id: NodeId,
1389 lower_bounds: impl FnOnce(&mut Self) -> hir::GenericBounds<'hir>,
1390 ) -> hir::TyKind<'hir> {
1392 "lower_opaque_impl_trait(fn_def_id={:?}, opaque_ty_node_id={:?}, span={:?})",
1393 fn_def_id, opaque_ty_node_id, span,
1396 // Make sure we know that some funky desugaring has been going on here.
1397 // This is a first: there is code in other places like for loop
1398 // desugaring that explicitly states that we don't want to track that.
1399 // Not tracking it makes lints in rustc and clippy very fragile, as
1400 // frequently opened issues show.
1401 let opaque_ty_span = self.mark_span_with_reason(DesugaringKind::OpaqueTy, span, None);
1403 let opaque_ty_def_index =
1404 self.resolver.definitions().opt_def_index(opaque_ty_node_id).unwrap();
1406 self.allocate_hir_id_counter(opaque_ty_node_id);
1408 let hir_bounds = self.with_hir_id_owner(opaque_ty_node_id, lower_bounds);
1410 let (lifetimes, lifetime_defs) = self.lifetimes_from_impl_trait_bounds(
1412 opaque_ty_def_index,
1415 let lifetime_defs = self.arena.alloc_from_iter(lifetime_defs.into_iter());
1417 debug!("lower_opaque_impl_trait: lifetimes={:#?}", lifetimes,);
1419 debug!("lower_opaque_impl_trait: lifetime_defs={:#?}", lifetime_defs,);
1421 self.with_hir_id_owner(opaque_ty_node_id, move |lctx| {
1422 let opaque_ty_item = hir::OpaqueTy {
1423 generics: hir::Generics {
1424 params: lifetime_defs,
1425 where_clause: hir::WhereClause { predicates: &[], span },
1429 impl_trait_fn: fn_def_id,
1430 origin: hir::OpaqueTyOrigin::FnReturn,
1433 trace!("lower_opaque_impl_trait: {:#?}", opaque_ty_def_index);
1435 lctx.generate_opaque_type(opaque_ty_node_id, opaque_ty_item, span, opaque_ty_span);
1437 // `impl Trait` now just becomes `Foo<'a, 'b, ..>`.
1438 hir::TyKind::Def(hir::ItemId { id: opaque_ty_id }, lifetimes)
1442 /// Registers a new opaque type with the proper `NodeId`s and
1443 /// returns the lowered node-ID for the opaque type.
1444 fn generate_opaque_type(
1446 opaque_ty_node_id: NodeId,
1447 opaque_ty_item: hir::OpaqueTy<'hir>,
1449 opaque_ty_span: Span,
1451 let opaque_ty_item_kind = hir::ItemKind::OpaqueTy(opaque_ty_item);
1452 let opaque_ty_id = self.lower_node_id(opaque_ty_node_id);
1453 // Generate an `type Foo = impl Trait;` declaration.
1454 trace!("registering opaque type with id {:#?}", opaque_ty_id);
1455 let opaque_ty_item = hir::Item {
1456 hir_id: opaque_ty_id,
1457 ident: Ident::invalid(),
1458 attrs: Default::default(),
1459 kind: opaque_ty_item_kind,
1460 vis: respan(span.shrink_to_lo(), hir::VisibilityKind::Inherited),
1461 span: opaque_ty_span,
1464 // Insert the item into the global item list. This usually happens
1465 // automatically for all AST items. But this opaque type item
1466 // does not actually exist in the AST.
1467 self.insert_item(opaque_ty_item);
1471 fn lifetimes_from_impl_trait_bounds(
1473 opaque_ty_id: NodeId,
1474 parent_index: DefIndex,
1475 bounds: hir::GenericBounds<'hir>,
1476 ) -> (&'hir [hir::GenericArg<'hir>], HirVec<hir::GenericParam<'hir>>) {
1478 "lifetimes_from_impl_trait_bounds(opaque_ty_id={:?}, \
1479 parent_index={:?}, \
1481 opaque_ty_id, parent_index, bounds,
1484 // This visitor walks over `impl Trait` bounds and creates defs for all lifetimes that
1485 // appear in the bounds, excluding lifetimes that are created within the bounds.
1486 // E.g., `'a`, `'b`, but not `'c` in `impl for<'c> SomeTrait<'a, 'b, 'c>`.
1487 struct ImplTraitLifetimeCollector<'r, 'a, 'hir> {
1488 context: &'r mut LoweringContext<'a, 'hir>,
1490 opaque_ty_id: NodeId,
1491 collect_elided_lifetimes: bool,
1492 currently_bound_lifetimes: Vec<hir::LifetimeName>,
1493 already_defined_lifetimes: FxHashSet<hir::LifetimeName>,
1494 output_lifetimes: Vec<hir::GenericArg<'hir>>,
1495 output_lifetime_params: Vec<hir::GenericParam<'hir>>,
1498 impl<'r, 'a, 'v, 'hir> hir::intravisit::Visitor<'v> for ImplTraitLifetimeCollector<'r, 'a, 'hir> {
1499 fn nested_visit_map<'this>(
1501 ) -> hir::intravisit::NestedVisitorMap<'this, 'v> {
1502 hir::intravisit::NestedVisitorMap::None
1505 fn visit_generic_args(&mut self, span: Span, parameters: &'v hir::GenericArgs<'v>) {
1506 // Don't collect elided lifetimes used inside of `Fn()` syntax.
1507 if parameters.parenthesized {
1508 let old_collect_elided_lifetimes = self.collect_elided_lifetimes;
1509 self.collect_elided_lifetimes = false;
1510 hir::intravisit::walk_generic_args(self, span, parameters);
1511 self.collect_elided_lifetimes = old_collect_elided_lifetimes;
1513 hir::intravisit::walk_generic_args(self, span, parameters);
1517 fn visit_ty(&mut self, t: &'v hir::Ty<'v>) {
1518 // Don't collect elided lifetimes used inside of `fn()` syntax.
1519 if let hir::TyKind::BareFn(_) = t.kind {
1520 let old_collect_elided_lifetimes = self.collect_elided_lifetimes;
1521 self.collect_elided_lifetimes = false;
1523 // Record the "stack height" of `for<'a>` lifetime bindings
1524 // to be able to later fully undo their introduction.
1525 let old_len = self.currently_bound_lifetimes.len();
1526 hir::intravisit::walk_ty(self, t);
1527 self.currently_bound_lifetimes.truncate(old_len);
1529 self.collect_elided_lifetimes = old_collect_elided_lifetimes;
1531 hir::intravisit::walk_ty(self, t)
1535 fn visit_poly_trait_ref(
1537 trait_ref: &'v hir::PolyTraitRef<'v>,
1538 modifier: hir::TraitBoundModifier,
1540 // Record the "stack height" of `for<'a>` lifetime bindings
1541 // to be able to later fully undo their introduction.
1542 let old_len = self.currently_bound_lifetimes.len();
1543 hir::intravisit::walk_poly_trait_ref(self, trait_ref, modifier);
1544 self.currently_bound_lifetimes.truncate(old_len);
1547 fn visit_generic_param(&mut self, param: &'v hir::GenericParam<'v>) {
1548 // Record the introduction of 'a in `for<'a> ...`.
1549 if let hir::GenericParamKind::Lifetime { .. } = param.kind {
1550 // Introduce lifetimes one at a time so that we can handle
1551 // cases like `fn foo<'d>() -> impl for<'a, 'b: 'a, 'c: 'b + 'd>`.
1552 let lt_name = hir::LifetimeName::Param(param.name);
1553 self.currently_bound_lifetimes.push(lt_name);
1556 hir::intravisit::walk_generic_param(self, param);
1559 fn visit_lifetime(&mut self, lifetime: &'v hir::Lifetime) {
1560 let name = match lifetime.name {
1561 hir::LifetimeName::Implicit | hir::LifetimeName::Underscore => {
1562 if self.collect_elided_lifetimes {
1563 // Use `'_` for both implicit and underscore lifetimes in
1564 // `type Foo<'_> = impl SomeTrait<'_>;`.
1565 hir::LifetimeName::Underscore
1570 hir::LifetimeName::Param(_) => lifetime.name,
1572 // Refers to some other lifetime that is "in
1573 // scope" within the type.
1574 hir::LifetimeName::ImplicitObjectLifetimeDefault => return,
1576 hir::LifetimeName::Error | hir::LifetimeName::Static => return,
1579 if !self.currently_bound_lifetimes.contains(&name)
1580 && !self.already_defined_lifetimes.contains(&name)
1582 self.already_defined_lifetimes.insert(name);
1584 self.output_lifetimes.push(hir::GenericArg::Lifetime(hir::Lifetime {
1585 hir_id: self.context.next_id(),
1586 span: lifetime.span,
1590 let def_node_id = self.context.resolver.next_node_id();
1592 self.context.lower_node_id_with_owner(def_node_id, self.opaque_ty_id);
1593 self.context.resolver.definitions().create_def_with_parent(
1596 DefPathData::LifetimeNs(name.ident().name),
1601 let (name, kind) = match name {
1602 hir::LifetimeName::Underscore => (
1603 hir::ParamName::Plain(Ident::with_dummy_span(kw::UnderscoreLifetime)),
1604 hir::LifetimeParamKind::Elided,
1606 hir::LifetimeName::Param(param_name) => {
1607 (param_name, hir::LifetimeParamKind::Explicit)
1609 _ => bug!("expected `LifetimeName::Param` or `ParamName::Plain`"),
1612 self.output_lifetime_params.push(hir::GenericParam {
1615 span: lifetime.span,
1616 pure_wrt_drop: false,
1619 kind: hir::GenericParamKind::Lifetime { kind },
1625 let mut lifetime_collector = ImplTraitLifetimeCollector {
1627 parent: parent_index,
1629 collect_elided_lifetimes: true,
1630 currently_bound_lifetimes: Vec::new(),
1631 already_defined_lifetimes: FxHashSet::default(),
1632 output_lifetimes: Vec::new(),
1633 output_lifetime_params: Vec::new(),
1636 for bound in bounds {
1637 hir::intravisit::walk_param_bound(&mut lifetime_collector, &bound);
1640 let ImplTraitLifetimeCollector { output_lifetimes, output_lifetime_params, .. } =
1643 (self.arena.alloc_from_iter(output_lifetimes), output_lifetime_params.into())
1649 qself: &Option<QSelf>,
1651 param_mode: ParamMode,
1652 mut itctx: ImplTraitContext<'_, 'hir>,
1653 ) -> hir::QPath<'hir> {
1654 let qself_position = qself.as_ref().map(|q| q.position);
1655 let qself = qself.as_ref().map(|q| self.lower_ty(&q.ty, itctx.reborrow()));
1658 self.resolver.get_partial_res(id).unwrap_or_else(|| PartialRes::new(Res::Err));
1660 let proj_start = p.segments.len() - partial_res.unresolved_segments();
1661 let path = self.arena.alloc(hir::Path {
1662 res: self.lower_res(partial_res.base_res()),
1663 segments: self.arena.alloc_from_iter(p.segments[..proj_start].iter().enumerate().map(
1665 let param_mode = match (qself_position, param_mode) {
1666 (Some(j), ParamMode::Optional) if i < j => {
1667 // This segment is part of the trait path in a
1668 // qualified path - one of `a`, `b` or `Trait`
1669 // in `<X as a::b::Trait>::T::U::method`.
1675 // Figure out if this is a type/trait segment,
1676 // which may need lifetime elision performed.
1677 let parent_def_id = |this: &mut Self, def_id: DefId| DefId {
1678 krate: def_id.krate,
1679 index: this.def_key(def_id).parent.expect("missing parent"),
1681 let type_def_id = match partial_res.base_res() {
1682 Res::Def(DefKind::AssocTy, def_id) if i + 2 == proj_start => {
1683 Some(parent_def_id(self, def_id))
1685 Res::Def(DefKind::Variant, def_id) if i + 1 == proj_start => {
1686 Some(parent_def_id(self, def_id))
1688 Res::Def(DefKind::Struct, def_id)
1689 | Res::Def(DefKind::Union, def_id)
1690 | Res::Def(DefKind::Enum, def_id)
1691 | Res::Def(DefKind::TyAlias, def_id)
1692 | Res::Def(DefKind::Trait, def_id)
1693 if i + 1 == proj_start =>
1699 let parenthesized_generic_args = match partial_res.base_res() {
1700 // `a::b::Trait(Args)`
1701 Res::Def(DefKind::Trait, _) if i + 1 == proj_start => {
1702 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 _ => ParenthesizedGenericArgs::Err,
1718 let num_lifetimes = type_def_id.map_or(0, |def_id| {
1719 if let Some(&n) = self.type_def_lifetime_params.get(&def_id) {
1722 assert!(!def_id.is_local());
1723 let item_generics = self
1726 .item_generics_cloned_untracked(def_id, self.sess);
1727 let n = item_generics.own_counts().lifetimes;
1728 self.type_def_lifetime_params.insert(def_id, n);
1731 self.lower_path_segment(
1736 parenthesized_generic_args,
1745 // Simple case, either no projections, or only fully-qualified.
1746 // E.g., `std::mem::size_of` or `<I as Iterator>::Item`.
1747 if partial_res.unresolved_segments() == 0 {
1748 return hir::QPath::Resolved(qself, path);
1751 // Create the innermost type that we're projecting from.
1752 let mut ty = if path.segments.is_empty() {
1753 // If the base path is empty that means there exists a
1754 // syntactical `Self`, e.g., `&i32` in `<&i32>::clone`.
1755 qself.expect("missing QSelf for <T>::...")
1757 // Otherwise, the base path is an implicit `Self` type path,
1758 // e.g., `Vec` in `Vec::new` or `<I as Iterator>::Item` in
1759 // `<I as Iterator>::Item::default`.
1760 let new_id = self.next_id();
1761 self.arena.alloc(self.ty_path(new_id, p.span, hir::QPath::Resolved(qself, path)))
1764 // Anything after the base path are associated "extensions",
1765 // out of which all but the last one are associated types,
1766 // e.g., for `std::vec::Vec::<T>::IntoIter::Item::clone`:
1767 // * base path is `std::vec::Vec<T>`
1768 // * "extensions" are `IntoIter`, `Item` and `clone`
1769 // * type nodes are:
1770 // 1. `std::vec::Vec<T>` (created above)
1771 // 2. `<std::vec::Vec<T>>::IntoIter`
1772 // 3. `<<std::vec::Vec<T>>::IntoIter>::Item`
1773 // * final path is `<<<std::vec::Vec<T>>::IntoIter>::Item>::clone`
1774 for (i, segment) in p.segments.iter().enumerate().skip(proj_start) {
1775 let segment = self.arena.alloc(self.lower_path_segment(
1780 ParenthesizedGenericArgs::Err,
1784 let qpath = hir::QPath::TypeRelative(ty, segment);
1786 // It's finished, return the extension of the right node type.
1787 if i == p.segments.len() - 1 {
1791 // Wrap the associated extension in another type node.
1792 let new_id = self.next_id();
1793 ty = self.arena.alloc(self.ty_path(new_id, p.span, qpath));
1796 // We should've returned in the for loop above.
1799 "lower_qpath: no final extension segment in {}..{}",
1805 fn lower_path_extra(
1809 param_mode: ParamMode,
1810 explicit_owner: Option<NodeId>,
1811 ) -> hir::Path<'hir> {
1814 segments: self.arena.alloc_from_iter(p.segments.iter().map(|segment| {
1815 self.lower_path_segment(
1820 ParenthesizedGenericArgs::Err,
1821 ImplTraitContext::disallowed(),
1829 fn lower_path(&mut self, id: NodeId, p: &Path, param_mode: ParamMode) -> hir::Path<'hir> {
1830 let res = self.expect_full_res(id);
1831 let res = self.lower_res(res);
1832 self.lower_path_extra(res, p, param_mode, None)
1835 fn lower_path_segment(
1838 segment: &PathSegment,
1839 param_mode: ParamMode,
1840 expected_lifetimes: usize,
1841 parenthesized_generic_args: ParenthesizedGenericArgs,
1842 itctx: ImplTraitContext<'_, 'hir>,
1843 explicit_owner: Option<NodeId>,
1844 ) -> hir::PathSegment<'hir> {
1845 let (mut generic_args, infer_args) = if let Some(ref generic_args) = segment.args {
1846 let msg = "parenthesized type parameters may only be used with a `Fn` trait";
1847 match **generic_args {
1848 GenericArgs::AngleBracketed(ref data) => {
1849 self.lower_angle_bracketed_parameter_data(data, param_mode, itctx)
1851 GenericArgs::Parenthesized(ref data) => match parenthesized_generic_args {
1852 ParenthesizedGenericArgs::Ok => self.lower_parenthesized_parameter_data(data),
1853 ParenthesizedGenericArgs::Err => {
1854 let mut err = struct_span_err!(self.sess, data.span, E0214, "{}", msg);
1855 err.span_label(data.span, "only `Fn` traits may use parentheses");
1856 if let Ok(snippet) = self.sess.source_map().span_to_snippet(data.span) {
1857 // Do not suggest going from `Trait()` to `Trait<>`
1858 if data.inputs.len() > 0 {
1859 if let Some(split) = snippet.find('(') {
1860 let trait_name = &snippet[0..split];
1861 let args = &snippet[split + 1..snippet.len() - 1];
1862 err.span_suggestion(
1864 "use angle brackets instead",
1865 format!("{}<{}>", trait_name, args),
1866 Applicability::MaybeIncorrect,
1873 self.lower_angle_bracketed_parameter_data(
1874 &data.as_angle_bracketed_args(),
1885 self.lower_angle_bracketed_parameter_data(&Default::default(), param_mode, itctx)
1888 let has_lifetimes = generic_args.args.iter().any(|arg| match arg {
1889 GenericArg::Lifetime(_) => true,
1892 let first_generic_span = generic_args
1896 .chain(generic_args.bindings.iter().map(|b| b.span))
1898 if !generic_args.parenthesized && !has_lifetimes {
1899 generic_args.args = self
1900 .elided_path_lifetimes(path_span, expected_lifetimes)
1902 .map(|lt| GenericArg::Lifetime(lt))
1903 .chain(generic_args.args.into_iter())
1905 if expected_lifetimes > 0 && param_mode == ParamMode::Explicit {
1906 let anon_lt_suggestion = vec!["'_"; expected_lifetimes].join(", ");
1907 let no_non_lt_args = generic_args.args.len() == expected_lifetimes;
1908 let no_bindings = generic_args.bindings.is_empty();
1909 let (incl_angl_brckt, insertion_sp, suggestion) = if no_non_lt_args && no_bindings {
1910 // If there are no (non-implicit) generic args or associated type
1911 // bindings, our suggestion includes the angle brackets.
1912 (true, path_span.shrink_to_hi(), format!("<{}>", anon_lt_suggestion))
1914 // Otherwise (sorry, this is kind of gross) we need to infer the
1915 // place to splice in the `'_, ` from the generics that do exist.
1916 let first_generic_span = first_generic_span
1917 .expect("already checked that non-lifetime args or bindings exist");
1918 (false, first_generic_span.shrink_to_lo(), format!("{}, ", anon_lt_suggestion))
1920 match self.anonymous_lifetime_mode {
1921 // In create-parameter mode we error here because we don't want to support
1922 // deprecated impl elision in new features like impl elision and `async fn`,
1923 // both of which work using the `CreateParameter` mode:
1925 // impl Foo for std::cell::Ref<u32> // note lack of '_
1926 // async fn foo(_: std::cell::Ref<u32>) { ... }
1927 AnonymousLifetimeMode::CreateParameter => {
1928 let mut err = struct_span_err!(
1932 "implicit elided lifetime not allowed here"
1934 crate::lint::builtin::add_elided_lifetime_in_path_suggestion(
1945 AnonymousLifetimeMode::PassThrough | AnonymousLifetimeMode::ReportError => {
1946 self.resolver.lint_buffer().buffer_lint_with_diagnostic(
1947 ELIDED_LIFETIMES_IN_PATHS,
1950 "hidden lifetime parameters in types are deprecated",
1951 builtin::BuiltinLintDiagnostics::ElidedLifetimesInPaths(
1964 let res = self.expect_full_res(segment.id);
1965 let id = if let Some(owner) = explicit_owner {
1966 self.lower_node_id_with_owner(segment.id, owner)
1968 self.lower_node_id(segment.id)
1971 "lower_path_segment: ident={:?} original-id={:?} new-id={:?}",
1972 segment.ident, segment.id, id,
1976 ident: segment.ident,
1978 res: Some(self.lower_res(res)),
1980 args: if generic_args.is_empty() {
1983 Some(self.arena.alloc(generic_args.into_generic_args(self.arena)))
1988 fn lower_angle_bracketed_parameter_data(
1990 data: &AngleBracketedArgs,
1991 param_mode: ParamMode,
1992 mut itctx: ImplTraitContext<'_, 'hir>,
1993 ) -> (GenericArgsCtor<'hir>, bool) {
1994 let &AngleBracketedArgs { ref args, ref constraints, .. } = data;
1995 let has_non_lt_args = args.iter().any(|arg| match arg {
1996 ast::GenericArg::Lifetime(_) => false,
1997 ast::GenericArg::Type(_) => true,
1998 ast::GenericArg::Const(_) => true,
2002 args: args.iter().map(|a| self.lower_generic_arg(a, itctx.reborrow())).collect(),
2003 bindings: self.arena.alloc_from_iter(
2004 constraints.iter().map(|b| self.lower_assoc_ty_constraint(b, itctx.reborrow())),
2006 parenthesized: false,
2008 !has_non_lt_args && param_mode == ParamMode::Optional,
2012 fn lower_parenthesized_parameter_data(
2014 data: &ParenthesizedArgs,
2015 ) -> (GenericArgsCtor<'hir>, bool) {
2016 // Switch to `PassThrough` mode for anonymous lifetimes; this
2017 // means that we permit things like `&Ref<T>`, where `Ref` has
2018 // a hidden lifetime parameter. This is needed for backwards
2019 // compatibility, even in contexts like an impl header where
2020 // we generally don't permit such things (see #51008).
2021 self.with_anonymous_lifetime_mode(AnonymousLifetimeMode::PassThrough, |this| {
2022 let &ParenthesizedArgs { ref inputs, ref output, span } = data;
2023 let inputs = this.arena.alloc_from_iter(
2024 inputs.iter().map(|ty| this.lower_ty_direct(ty, ImplTraitContext::disallowed())),
2026 let output_ty = match output {
2027 FunctionRetTy::Ty(ty) => this.lower_ty(&ty, ImplTraitContext::disallowed()),
2028 FunctionRetTy::Default(_) => this.arena.alloc(this.ty_tup(span, &[])),
2030 let args = vec![GenericArg::Type(this.ty_tup(span, inputs))];
2031 let binding = hir::TypeBinding {
2032 hir_id: this.next_id(),
2033 ident: Ident::with_dummy_span(FN_OUTPUT_NAME),
2034 span: output_ty.span,
2035 kind: hir::TypeBindingKind::Equality { ty: output_ty },
2038 GenericArgsCtor { args, bindings: arena_vec![this; binding], parenthesized: true },
2044 fn lower_local(&mut self, l: &Local) -> (hir::Local<'hir>, SmallVec<[NodeId; 1]>) {
2045 let mut ids = SmallVec::<[NodeId; 1]>::new();
2046 if self.sess.features_untracked().impl_trait_in_bindings {
2047 if let Some(ref ty) = l.ty {
2048 let mut visitor = ImplTraitTypeIdVisitor { ids: &mut ids };
2049 visitor.visit_ty(ty);
2052 let parent_def_id = DefId::local(self.current_hir_id_owner.last().unwrap().0);
2053 let ty = l.ty.as_ref().map(|t| {
2056 if self.sess.features_untracked().impl_trait_in_bindings {
2057 ImplTraitContext::OpaqueTy(Some(parent_def_id))
2059 ImplTraitContext::Disallowed(ImplTraitPosition::Binding)
2063 let init = l.init.as_ref().map(|e| self.lower_expr(e));
2066 hir_id: self.lower_node_id(l.id),
2068 pat: self.lower_pat(&l.pat),
2071 attrs: l.attrs.clone(),
2072 source: hir::LocalSource::Normal,
2078 fn lower_fn_params_to_names(&mut self, decl: &FnDecl) -> hir::HirVec<Ident> {
2079 // Skip the `...` (`CVarArgs`) trailing arguments from the AST,
2080 // as they are not explicit in HIR/Ty function signatures.
2081 // (instead, the `c_variadic` flag is set to `true`)
2082 let mut inputs = &decl.inputs[..];
2083 if decl.c_variadic() {
2084 inputs = &inputs[..inputs.len() - 1];
2088 .map(|param| match param.pat.kind {
2089 PatKind::Ident(_, ident, _) => ident,
2090 _ => Ident::new(kw::Invalid, param.pat.span),
2095 // Lowers a function declaration.
2097 // `decl`: the unlowered (AST) function declaration.
2098 // `fn_def_id`: if `Some`, impl Trait arguments are lowered into generic parameters on the
2099 // given DefId, otherwise impl Trait is disallowed. Must be `Some` if
2100 // `make_ret_async` is also `Some`.
2101 // `impl_trait_return_allow`: determines whether `impl Trait` can be used in return position.
2102 // This guards against trait declarations and implementations where `impl Trait` is
2104 // `make_ret_async`: if `Some`, converts `-> T` into `-> impl Future<Output = T>` in the
2105 // return type. This is used for `async fn` declarations. The `NodeId` is the ID of the
2106 // return type `impl Trait` item.
2110 mut in_band_ty_params: Option<(DefId, &mut Vec<hir::GenericParam<'hir>>)>,
2111 impl_trait_return_allow: bool,
2112 make_ret_async: Option<NodeId>,
2113 ) -> &'hir hir::FnDecl<'hir> {
2117 in_band_ty_params: {:?}, \
2118 impl_trait_return_allow: {}, \
2119 make_ret_async: {:?})",
2120 decl, in_band_ty_params, impl_trait_return_allow, make_ret_async,
2122 let lt_mode = if make_ret_async.is_some() {
2123 // In `async fn`, argument-position elided lifetimes
2124 // must be transformed into fresh generic parameters so that
2125 // they can be applied to the opaque `impl Trait` return type.
2126 AnonymousLifetimeMode::CreateParameter
2128 self.anonymous_lifetime_mode
2131 let c_variadic = decl.c_variadic();
2133 // Remember how many lifetimes were already around so that we can
2134 // only look at the lifetime parameters introduced by the arguments.
2135 let inputs = self.with_anonymous_lifetime_mode(lt_mode, |this| {
2136 // Skip the `...` (`CVarArgs`) trailing arguments from the AST,
2137 // as they are not explicit in HIR/Ty function signatures.
2138 // (instead, the `c_variadic` flag is set to `true`)
2139 let mut inputs = &decl.inputs[..];
2141 inputs = &inputs[..inputs.len() - 1];
2143 this.arena.alloc_from_iter(inputs.iter().map(|param| {
2144 if let Some((_, ibty)) = &mut in_band_ty_params {
2145 this.lower_ty_direct(¶m.ty, ImplTraitContext::Universal(ibty))
2147 this.lower_ty_direct(¶m.ty, ImplTraitContext::disallowed())
2152 let output = if let Some(ret_id) = make_ret_async {
2153 self.lower_async_fn_ret_ty(
2155 in_band_ty_params.expect("`make_ret_async` but no `fn_def_id`").0,
2160 FunctionRetTy::Ty(ref ty) => match in_band_ty_params {
2161 Some((def_id, _)) if impl_trait_return_allow => {
2162 hir::Return(self.lower_ty(ty, ImplTraitContext::OpaqueTy(Some(def_id))))
2164 _ => hir::Return(self.lower_ty(ty, ImplTraitContext::disallowed())),
2166 FunctionRetTy::Default(span) => hir::DefaultReturn(span),
2170 self.arena.alloc(hir::FnDecl {
2174 implicit_self: decl.inputs.get(0).map_or(hir::ImplicitSelfKind::None, |arg| {
2175 let is_mutable_pat = match arg.pat.kind {
2176 PatKind::Ident(BindingMode::ByValue(mt), _, _)
2177 | PatKind::Ident(BindingMode::ByRef(mt), _, _) => mt == Mutability::Mut,
2182 TyKind::ImplicitSelf if is_mutable_pat => hir::ImplicitSelfKind::Mut,
2183 TyKind::ImplicitSelf => hir::ImplicitSelfKind::Imm,
2184 // Given we are only considering `ImplicitSelf` types, we needn't consider
2185 // the case where we have a mutable pattern to a reference as that would
2186 // no longer be an `ImplicitSelf`.
2187 TyKind::Rptr(_, ref mt)
2188 if mt.ty.kind.is_implicit_self() && mt.mutbl == ast::Mutability::Mut =>
2190 hir::ImplicitSelfKind::MutRef
2192 TyKind::Rptr(_, ref mt) if mt.ty.kind.is_implicit_self() => {
2193 hir::ImplicitSelfKind::ImmRef
2195 _ => hir::ImplicitSelfKind::None,
2201 // Transforms `-> T` for `async fn` into `-> OpaqueTy { .. }`
2202 // combined with the following definition of `OpaqueTy`:
2204 // type OpaqueTy<generics_from_parent_fn> = impl Future<Output = T>;
2206 // `inputs`: lowered types of parameters to the function (used to collect lifetimes)
2207 // `output`: unlowered output type (`T` in `-> T`)
2208 // `fn_def_id`: `DefId` of the parent function (used to create child impl trait definition)
2209 // `opaque_ty_node_id`: `NodeId` of the opaque `impl Trait` type that should be created
2210 // `elided_lt_replacement`: replacement for elided lifetimes in the return type
2211 fn lower_async_fn_ret_ty(
2213 output: &FunctionRetTy,
2215 opaque_ty_node_id: NodeId,
2216 ) -> hir::FunctionRetTy<'hir> {
2218 "lower_async_fn_ret_ty(\
2221 opaque_ty_node_id={:?})",
2222 output, fn_def_id, opaque_ty_node_id,
2225 let span = output.span();
2227 let opaque_ty_span = self.mark_span_with_reason(DesugaringKind::Async, span, None);
2229 let opaque_ty_def_index =
2230 self.resolver.definitions().opt_def_index(opaque_ty_node_id).unwrap();
2232 self.allocate_hir_id_counter(opaque_ty_node_id);
2234 // When we create the opaque type for this async fn, it is going to have
2235 // to capture all the lifetimes involved in the signature (including in the
2236 // return type). This is done by introducing lifetime parameters for:
2238 // - all the explicitly declared lifetimes from the impl and function itself;
2239 // - all the elided lifetimes in the fn arguments;
2240 // - all the elided lifetimes in the return type.
2242 // So for example in this snippet:
2245 // impl<'a> Foo<'a> {
2246 // async fn bar<'b>(&self, x: &'b Vec<f64>, y: &str) -> &u32 {
2247 // // ^ '0 ^ '1 ^ '2
2248 // // elided lifetimes used below
2253 // we would create an opaque type like:
2256 // type Bar<'a, 'b, '0, '1, '2> = impl Future<Output = &'2 u32>;
2259 // and we would then desugar `bar` to the equivalent of:
2262 // impl<'a> Foo<'a> {
2263 // fn bar<'b, '0, '1>(&'0 self, x: &'b Vec<f64>, y: &'1 str) -> Bar<'a, 'b, '0, '1, '_>
2267 // Note that the final parameter to `Bar` is `'_`, not `'2` --
2268 // this is because the elided lifetimes from the return type
2269 // should be figured out using the ordinary elision rules, and
2270 // this desugaring achieves that.
2272 // The variable `input_lifetimes_count` tracks the number of
2273 // lifetime parameters to the opaque type *not counting* those
2274 // lifetimes elided in the return type. This includes those
2275 // that are explicitly declared (`in_scope_lifetimes`) and
2276 // those elided lifetimes we found in the arguments (current
2277 // content of `lifetimes_to_define`). Next, we will process
2278 // the return type, which will cause `lifetimes_to_define` to
2280 let input_lifetimes_count = self.in_scope_lifetimes.len() + self.lifetimes_to_define.len();
2282 let (opaque_ty_id, lifetime_params) = self.with_hir_id_owner(opaque_ty_node_id, |this| {
2283 // We have to be careful to get elision right here. The
2284 // idea is that we create a lifetime parameter for each
2285 // lifetime in the return type. So, given a return type
2286 // like `async fn foo(..) -> &[&u32]`, we lower to `impl
2287 // Future<Output = &'1 [ &'2 u32 ]>`.
2289 // Then, we will create `fn foo(..) -> Foo<'_, '_>`, and
2290 // hence the elision takes place at the fn site.
2291 let future_bound = this
2292 .with_anonymous_lifetime_mode(AnonymousLifetimeMode::CreateParameter, |this| {
2293 this.lower_async_fn_output_type_to_future_bound(output, fn_def_id, span)
2296 debug!("lower_async_fn_ret_ty: future_bound={:#?}", future_bound);
2298 // Calculate all the lifetimes that should be captured
2299 // by the opaque type. This should include all in-scope
2300 // lifetime parameters, including those defined in-band.
2302 // Note: this must be done after lowering the output type,
2303 // as the output type may introduce new in-band lifetimes.
2304 let lifetime_params: Vec<(Span, ParamName)> = this
2308 .map(|name| (name.ident().span, name))
2309 .chain(this.lifetimes_to_define.iter().cloned())
2312 debug!("lower_async_fn_ret_ty: in_scope_lifetimes={:#?}", this.in_scope_lifetimes);
2313 debug!("lower_async_fn_ret_ty: lifetimes_to_define={:#?}", this.lifetimes_to_define);
2314 debug!("lower_async_fn_ret_ty: lifetime_params={:#?}", lifetime_params);
2316 let generic_params =
2317 this.arena.alloc_from_iter(lifetime_params.iter().map(|(span, hir_name)| {
2318 this.lifetime_to_generic_param(*span, *hir_name, opaque_ty_def_index)
2321 let opaque_ty_item = hir::OpaqueTy {
2322 generics: hir::Generics {
2323 params: generic_params,
2324 where_clause: hir::WhereClause { predicates: &[], span },
2327 bounds: arena_vec![this; future_bound],
2328 impl_trait_fn: Some(fn_def_id),
2329 origin: hir::OpaqueTyOrigin::AsyncFn,
2332 trace!("exist ty from async fn def index: {:#?}", opaque_ty_def_index);
2334 this.generate_opaque_type(opaque_ty_node_id, opaque_ty_item, span, opaque_ty_span);
2336 (opaque_ty_id, lifetime_params)
2339 // As documented above on the variable
2340 // `input_lifetimes_count`, we need to create the lifetime
2341 // arguments to our opaque type. Continuing with our example,
2342 // we're creating the type arguments for the return type:
2345 // Bar<'a, 'b, '0, '1, '_>
2348 // For the "input" lifetime parameters, we wish to create
2349 // references to the parameters themselves, including the
2350 // "implicit" ones created from parameter types (`'a`, `'b`,
2353 // For the "output" lifetime parameters, we just want to
2355 let mut generic_args: Vec<_> = lifetime_params[..input_lifetimes_count]
2357 .map(|&(span, hir_name)| {
2358 // Input lifetime like `'a` or `'1`:
2359 GenericArg::Lifetime(hir::Lifetime {
2360 hir_id: self.next_id(),
2362 name: hir::LifetimeName::Param(hir_name),
2366 generic_args.extend(lifetime_params[input_lifetimes_count..].iter().map(|&(span, _)|
2367 // Output lifetime like `'_`.
2368 GenericArg::Lifetime(hir::Lifetime {
2369 hir_id: self.next_id(),
2371 name: hir::LifetimeName::Implicit,
2373 let generic_args = self.arena.alloc_from_iter(generic_args);
2375 // Create the `Foo<...>` reference itself. Note that the `type
2376 // Foo = impl Trait` is, internally, created as a child of the
2377 // async fn, so the *type parameters* are inherited. It's
2378 // only the lifetime parameters that we must supply.
2379 let opaque_ty_ref = hir::TyKind::Def(hir::ItemId { id: opaque_ty_id }, generic_args);
2380 let opaque_ty = self.ty(opaque_ty_span, opaque_ty_ref);
2381 hir::FunctionRetTy::Return(self.arena.alloc(opaque_ty))
2384 /// Transforms `-> T` into `Future<Output = T>`
2385 fn lower_async_fn_output_type_to_future_bound(
2387 output: &FunctionRetTy,
2390 ) -> hir::GenericBound<'hir> {
2391 // Compute the `T` in `Future<Output = T>` from the return type.
2392 let output_ty = match output {
2393 FunctionRetTy::Ty(ty) => self.lower_ty(ty, ImplTraitContext::OpaqueTy(Some(fn_def_id))),
2394 FunctionRetTy::Default(ret_ty_span) => self.arena.alloc(self.ty_tup(*ret_ty_span, &[])),
2398 let future_params = self.arena.alloc(hir::GenericArgs {
2400 bindings: arena_vec![self; hir::TypeBinding {
2401 ident: Ident::with_dummy_span(FN_OUTPUT_NAME),
2402 kind: hir::TypeBindingKind::Equality { ty: output_ty },
2403 hir_id: self.next_id(),
2406 parenthesized: false,
2409 // ::std::future::Future<future_params>
2410 let future_path = self.arena.alloc(self.std_path(
2412 &[sym::future, sym::Future],
2413 Some(future_params),
2417 hir::GenericBound::Trait(
2419 trait_ref: hir::TraitRef { path: future_path, hir_ref_id: self.next_id() },
2420 bound_generic_params: &[],
2423 hir::TraitBoundModifier::None,
2427 fn lower_param_bound(
2430 itctx: ImplTraitContext<'_, 'hir>,
2431 ) -> hir::GenericBound<'hir> {
2433 GenericBound::Trait(ref ty, modifier) => hir::GenericBound::Trait(
2434 self.lower_poly_trait_ref(ty, itctx),
2435 self.lower_trait_bound_modifier(modifier),
2437 GenericBound::Outlives(ref lifetime) => {
2438 hir::GenericBound::Outlives(self.lower_lifetime(lifetime))
2443 fn lower_lifetime(&mut self, l: &Lifetime) -> hir::Lifetime {
2444 let span = l.ident.span;
2446 ident if ident.name == kw::StaticLifetime => {
2447 self.new_named_lifetime(l.id, span, hir::LifetimeName::Static)
2449 ident if ident.name == kw::UnderscoreLifetime => match self.anonymous_lifetime_mode {
2450 AnonymousLifetimeMode::CreateParameter => {
2451 let fresh_name = self.collect_fresh_in_band_lifetime(span);
2452 self.new_named_lifetime(l.id, span, hir::LifetimeName::Param(fresh_name))
2455 AnonymousLifetimeMode::PassThrough => {
2456 self.new_named_lifetime(l.id, span, hir::LifetimeName::Underscore)
2459 AnonymousLifetimeMode::ReportError => self.new_error_lifetime(Some(l.id), span),
2462 self.maybe_collect_in_band_lifetime(ident);
2463 let param_name = ParamName::Plain(ident);
2464 self.new_named_lifetime(l.id, span, hir::LifetimeName::Param(param_name))
2469 fn new_named_lifetime(
2473 name: hir::LifetimeName,
2474 ) -> hir::Lifetime {
2475 hir::Lifetime { hir_id: self.lower_node_id(id), span, name }
2478 fn lower_generic_params_mut(
2480 params: &[GenericParam],
2481 add_bounds: &NodeMap<Vec<GenericBound>>,
2482 mut itctx: ImplTraitContext<'_, 'hir>,
2483 ) -> Vec<hir::GenericParam<'hir>> {
2486 .map(|param| self.lower_generic_param(param, add_bounds, itctx.reborrow()))
2490 fn lower_generic_params(
2492 params: &[GenericParam],
2493 add_bounds: &NodeMap<Vec<GenericBound>>,
2494 itctx: ImplTraitContext<'_, 'hir>,
2495 ) -> &'hir [hir::GenericParam<'hir>] {
2496 self.arena.alloc_from_iter(self.lower_generic_params_mut(params, add_bounds, itctx))
2499 fn lower_generic_param(
2501 param: &GenericParam,
2502 add_bounds: &NodeMap<Vec<GenericBound>>,
2503 mut itctx: ImplTraitContext<'_, 'hir>,
2504 ) -> hir::GenericParam<'hir> {
2505 let mut bounds: Vec<_> = self
2506 .with_anonymous_lifetime_mode(AnonymousLifetimeMode::ReportError, |this| {
2507 this.lower_param_bounds_mut(¶m.bounds, itctx.reborrow()).collect()
2510 let (name, kind) = match param.kind {
2511 GenericParamKind::Lifetime => {
2512 let was_collecting_in_band = self.is_collecting_in_band_lifetimes;
2513 self.is_collecting_in_band_lifetimes = false;
2516 .with_anonymous_lifetime_mode(AnonymousLifetimeMode::ReportError, |this| {
2517 this.lower_lifetime(&Lifetime { id: param.id, ident: param.ident })
2519 let param_name = match lt.name {
2520 hir::LifetimeName::Param(param_name) => param_name,
2521 hir::LifetimeName::Implicit
2522 | hir::LifetimeName::Underscore
2523 | hir::LifetimeName::Static => hir::ParamName::Plain(lt.name.ident()),
2524 hir::LifetimeName::ImplicitObjectLifetimeDefault => {
2527 "object-lifetime-default should not occur here",
2530 hir::LifetimeName::Error => ParamName::Error,
2534 hir::GenericParamKind::Lifetime { kind: hir::LifetimeParamKind::Explicit };
2536 self.is_collecting_in_band_lifetimes = was_collecting_in_band;
2540 GenericParamKind::Type { ref default, .. } => {
2541 let add_bounds = add_bounds.get(¶m.id).map_or(&[][..], |x| &x);
2542 if !add_bounds.is_empty() {
2543 let params = self.lower_param_bounds_mut(add_bounds, itctx.reborrow());
2544 bounds.extend(params);
2547 let kind = hir::GenericParamKind::Type {
2550 .map(|x| self.lower_ty(x, ImplTraitContext::OpaqueTy(None))),
2554 .filter(|attr| attr.check_name(sym::rustc_synthetic))
2555 .map(|_| hir::SyntheticTyParamKind::ImplTrait)
2559 (hir::ParamName::Plain(param.ident), kind)
2561 GenericParamKind::Const { ref ty } => (
2562 hir::ParamName::Plain(param.ident),
2563 hir::GenericParamKind::Const {
2564 ty: self.lower_ty(&ty, ImplTraitContext::disallowed()),
2570 hir_id: self.lower_node_id(param.id),
2572 span: param.ident.span,
2573 pure_wrt_drop: attr::contains_name(¶m.attrs, sym::may_dangle),
2574 attrs: self.lower_attrs_arena(¶m.attrs),
2575 bounds: self.arena.alloc_from_iter(bounds),
2583 itctx: ImplTraitContext<'_, 'hir>,
2584 ) -> hir::TraitRef<'hir> {
2585 let path = match self.lower_qpath(p.ref_id, &None, &p.path, ParamMode::Explicit, itctx) {
2586 hir::QPath::Resolved(None, path) => path,
2587 qpath => bug!("lower_trait_ref: unexpected QPath `{:?}`", qpath),
2589 hir::TraitRef { path, hir_ref_id: self.lower_node_id(p.ref_id) }
2592 fn lower_poly_trait_ref(
2595 mut itctx: ImplTraitContext<'_, 'hir>,
2596 ) -> hir::PolyTraitRef<'hir> {
2597 let bound_generic_params = self.lower_generic_params(
2598 &p.bound_generic_params,
2599 &NodeMap::default(),
2602 let trait_ref = self.with_in_scope_lifetime_defs(&p.bound_generic_params, |this| {
2603 this.lower_trait_ref(&p.trait_ref, itctx)
2606 hir::PolyTraitRef { bound_generic_params, trait_ref, span: p.span }
2609 fn lower_mt(&mut self, mt: &MutTy, itctx: ImplTraitContext<'_, 'hir>) -> hir::MutTy<'hir> {
2610 hir::MutTy { ty: self.lower_ty(&mt.ty, itctx), mutbl: mt.mutbl }
2613 fn lower_param_bounds(
2615 bounds: &[GenericBound],
2616 itctx: ImplTraitContext<'_, 'hir>,
2617 ) -> hir::GenericBounds<'hir> {
2618 self.arena.alloc_from_iter(self.lower_param_bounds_mut(bounds, itctx))
2621 fn lower_param_bounds_mut<'s>(
2623 bounds: &'s [GenericBound],
2624 mut itctx: ImplTraitContext<'s, 'hir>,
2625 ) -> impl Iterator<Item = hir::GenericBound<'hir>> + Captures<'s> + Captures<'a> {
2626 bounds.iter().map(move |bound| self.lower_param_bound(bound, itctx.reborrow()))
2629 fn lower_block(&mut self, b: &Block, targeted_by_break: bool) -> &'hir hir::Block<'hir> {
2630 self.arena.alloc(self.lower_block_noalloc(b, targeted_by_break))
2633 fn lower_block_noalloc(&mut self, b: &Block, targeted_by_break: bool) -> hir::Block<'hir> {
2634 let mut stmts = vec![];
2635 let mut expr: Option<&'hir _> = None;
2637 for (index, stmt) in b.stmts.iter().enumerate() {
2638 if index == b.stmts.len() - 1 {
2639 if let StmtKind::Expr(ref e) = stmt.kind {
2640 expr = Some(self.lower_expr(e));
2642 stmts.extend(self.lower_stmt(stmt));
2645 stmts.extend(self.lower_stmt(stmt));
2650 hir_id: self.lower_node_id(b.id),
2651 stmts: self.arena.alloc_from_iter(stmts),
2653 rules: self.lower_block_check_mode(&b.rules),
2659 /// Lowers a block directly to an expression, presuming that it
2660 /// has no attributes and is not targeted by a `break`.
2661 fn lower_block_expr(&mut self, b: &Block) -> hir::Expr<'hir> {
2662 let block = self.lower_block(b, false);
2663 self.expr_block(block, AttrVec::new())
2666 fn lower_pat(&mut self, p: &Pat) -> &'hir hir::Pat<'hir> {
2667 let node = match p.kind {
2668 PatKind::Wild => hir::PatKind::Wild,
2669 PatKind::Ident(ref binding_mode, ident, ref sub) => {
2670 let lower_sub = |this: &mut Self| sub.as_ref().map(|s| this.lower_pat(&*s));
2671 let node = self.lower_pat_ident(p, binding_mode, ident, lower_sub);
2674 PatKind::Lit(ref e) => hir::PatKind::Lit(self.lower_expr(e)),
2675 PatKind::TupleStruct(ref path, ref pats) => {
2676 let qpath = self.lower_qpath(
2680 ParamMode::Optional,
2681 ImplTraitContext::disallowed(),
2683 let (pats, ddpos) = self.lower_pat_tuple(pats, "tuple struct");
2684 hir::PatKind::TupleStruct(qpath, pats, ddpos)
2686 PatKind::Or(ref pats) => {
2687 hir::PatKind::Or(self.arena.alloc_from_iter(pats.iter().map(|x| self.lower_pat(x))))
2689 PatKind::Path(ref qself, ref path) => {
2690 let qpath = self.lower_qpath(
2694 ParamMode::Optional,
2695 ImplTraitContext::disallowed(),
2697 hir::PatKind::Path(qpath)
2699 PatKind::Struct(ref path, ref fields, etc) => {
2700 let qpath = self.lower_qpath(
2704 ParamMode::Optional,
2705 ImplTraitContext::disallowed(),
2708 let fs = self.arena.alloc_from_iter(fields.iter().map(|f| hir::FieldPat {
2709 hir_id: self.next_id(),
2711 pat: self.lower_pat(&f.pat),
2712 is_shorthand: f.is_shorthand,
2715 hir::PatKind::Struct(qpath, fs, etc)
2717 PatKind::Tuple(ref pats) => {
2718 let (pats, ddpos) = self.lower_pat_tuple(pats, "tuple");
2719 hir::PatKind::Tuple(pats, ddpos)
2721 PatKind::Box(ref inner) => hir::PatKind::Box(self.lower_pat(inner)),
2722 PatKind::Ref(ref inner, mutbl) => hir::PatKind::Ref(self.lower_pat(inner), mutbl),
2723 PatKind::Range(ref e1, ref e2, Spanned { node: ref end, .. }) => hir::PatKind::Range(
2724 self.lower_expr(e1),
2725 self.lower_expr(e2),
2726 self.lower_range_end(end),
2728 PatKind::Slice(ref pats) => self.lower_pat_slice(pats),
2730 // If we reach here the `..` pattern is not semantically allowed.
2731 self.ban_illegal_rest_pat(p.span)
2733 PatKind::Paren(ref inner) => return self.lower_pat(inner),
2734 PatKind::Mac(_) => panic!("Shouldn't exist here"),
2737 self.pat_with_node_id_of(p, node)
2744 ) -> (&'hir [&'hir hir::Pat<'hir>], Option<usize>) {
2745 let mut elems = Vec::with_capacity(pats.len());
2746 let mut rest = None;
2748 let mut iter = pats.iter().enumerate();
2749 for (idx, pat) in iter.by_ref() {
2750 // Interpret the first `..` pattern as a sub-tuple pattern.
2751 // Note that unlike for slice patterns,
2752 // where `xs @ ..` is a legal sub-slice pattern,
2753 // it is not a legal sub-tuple pattern.
2755 rest = Some((idx, pat.span));
2758 // It was not a sub-tuple pattern so lower it normally.
2759 elems.push(self.lower_pat(pat));
2762 for (_, pat) in iter {
2763 // There was a previous sub-tuple pattern; make sure we don't allow more...
2765 // ...but there was one again, so error.
2766 self.ban_extra_rest_pat(pat.span, rest.unwrap().1, ctx);
2768 elems.push(self.lower_pat(pat));
2772 (self.arena.alloc_from_iter(elems), rest.map(|(ddpos, _)| ddpos))
2775 /// Lower a slice pattern of form `[pat_0, ..., pat_n]` into
2776 /// `hir::PatKind::Slice(before, slice, after)`.
2778 /// When encountering `($binding_mode $ident @)? ..` (`slice`),
2779 /// this is interpreted as a sub-slice pattern semantically.
2780 /// Patterns that follow, which are not like `slice` -- or an error occurs, are in `after`.
2781 fn lower_pat_slice(&mut self, pats: &[AstP<Pat>]) -> hir::PatKind<'hir> {
2782 let mut before = Vec::new();
2783 let mut after = Vec::new();
2784 let mut slice = None;
2785 let mut prev_rest_span = None;
2787 let mut iter = pats.iter();
2788 // Lower all the patterns until the first occurence of a sub-slice pattern.
2789 for pat in iter.by_ref() {
2791 // Found a sub-slice pattern `..`. Record, lower it to `_`, and stop here.
2793 prev_rest_span = Some(pat.span);
2794 slice = Some(self.pat_wild_with_node_id_of(pat));
2797 // Found a sub-slice pattern `$binding_mode $ident @ ..`.
2798 // Record, lower it to `$binding_mode $ident @ _`, and stop here.
2799 PatKind::Ident(ref bm, ident, Some(ref sub)) if sub.is_rest() => {
2800 prev_rest_span = Some(sub.span);
2801 let lower_sub = |this: &mut Self| Some(this.pat_wild_with_node_id_of(sub));
2802 let node = self.lower_pat_ident(pat, bm, ident, lower_sub);
2803 slice = Some(self.pat_with_node_id_of(pat, node));
2806 // It was not a subslice pattern so lower it normally.
2807 _ => before.push(self.lower_pat(pat)),
2811 // Lower all the patterns after the first sub-slice pattern.
2813 // There was a previous subslice pattern; make sure we don't allow more.
2814 let rest_span = match pat.kind {
2815 PatKind::Rest => Some(pat.span),
2816 PatKind::Ident(.., Some(ref sub)) if sub.is_rest() => {
2817 // The `HirValidator` is merciless; add a `_` pattern to avoid ICEs.
2818 after.push(self.pat_wild_with_node_id_of(pat));
2823 if let Some(rest_span) = rest_span {
2824 // We have e.g., `[a, .., b, ..]`. That's no good, error!
2825 self.ban_extra_rest_pat(rest_span, prev_rest_span.unwrap(), "slice");
2827 // Lower the pattern normally.
2828 after.push(self.lower_pat(pat));
2832 hir::PatKind::Slice(
2833 self.arena.alloc_from_iter(before),
2835 self.arena.alloc_from_iter(after),
2842 binding_mode: &BindingMode,
2844 lower_sub: impl FnOnce(&mut Self) -> Option<&'hir hir::Pat<'hir>>,
2845 ) -> hir::PatKind<'hir> {
2846 match self.resolver.get_partial_res(p.id).map(|d| d.base_res()) {
2847 // `None` can occur in body-less function signatures
2848 res @ None | res @ Some(Res::Local(_)) => {
2849 let canonical_id = match res {
2850 Some(Res::Local(id)) => id,
2854 hir::PatKind::Binding(
2855 self.lower_binding_mode(binding_mode),
2856 self.lower_node_id(canonical_id),
2861 Some(res) => hir::PatKind::Path(hir::QPath::Resolved(
2863 self.arena.alloc(hir::Path {
2865 res: self.lower_res(res),
2866 segments: arena_vec![self; hir::PathSegment::from_ident(ident)],
2872 fn pat_wild_with_node_id_of(&mut self, p: &Pat) -> &'hir hir::Pat<'hir> {
2873 self.pat_with_node_id_of(p, hir::PatKind::Wild)
2876 /// Construct a `Pat` with the `HirId` of `p.id` lowered.
2877 fn pat_with_node_id_of(&mut self, p: &Pat, kind: hir::PatKind<'hir>) -> &'hir hir::Pat<'hir> {
2878 self.arena.alloc(hir::Pat { hir_id: self.lower_node_id(p.id), kind, span: p.span })
2881 /// Emit a friendly error for extra `..` patterns in a tuple/tuple struct/slice pattern.
2882 fn ban_extra_rest_pat(&self, sp: Span, prev_sp: Span, ctx: &str) {
2884 .struct_span_err(sp, &format!("`..` can only be used once per {} pattern", ctx))
2885 .span_label(sp, &format!("can only be used once per {} pattern", ctx))
2886 .span_label(prev_sp, "previously used here")
2890 /// Used to ban the `..` pattern in places it shouldn't be semantically.
2891 fn ban_illegal_rest_pat(&self, sp: Span) -> hir::PatKind<'hir> {
2893 .struct_span_err(sp, "`..` patterns are not allowed here")
2894 .note("only allowed in tuple, tuple struct, and slice patterns")
2897 // We're not in a list context so `..` can be reasonably treated
2898 // as `_` because it should always be valid and roughly matches the
2899 // intent of `..` (notice that the rest of a single slot is that slot).
2903 fn lower_range_end(&mut self, e: &RangeEnd) -> hir::RangeEnd {
2905 RangeEnd::Included(_) => hir::RangeEnd::Included,
2906 RangeEnd::Excluded => hir::RangeEnd::Excluded,
2910 fn lower_anon_const(&mut self, c: &AnonConst) -> hir::AnonConst {
2911 self.with_new_scopes(|this| hir::AnonConst {
2912 hir_id: this.lower_node_id(c.id),
2913 body: this.lower_const_body(c.value.span, Some(&c.value)),
2917 fn lower_stmt(&mut self, s: &Stmt) -> SmallVec<[hir::Stmt<'hir>; 1]> {
2918 let kind = match s.kind {
2919 StmtKind::Local(ref l) => {
2920 let (l, item_ids) = self.lower_local(l);
2921 let mut ids: SmallVec<[hir::Stmt<'hir>; 1]> = item_ids
2924 let item_id = hir::ItemId { id: self.lower_node_id(item_id) };
2925 self.stmt(s.span, hir::StmtKind::Item(item_id))
2930 hir_id: self.lower_node_id(s.id),
2931 kind: hir::StmtKind::Local(self.arena.alloc(l)),
2937 StmtKind::Item(ref it) => {
2938 // Can only use the ID once.
2939 let mut id = Some(s.id);
2946 .map(|id| self.lower_node_id(id))
2947 .unwrap_or_else(|| self.next_id());
2949 hir::Stmt { hir_id, kind: hir::StmtKind::Item(item_id), span: s.span }
2953 StmtKind::Expr(ref e) => hir::StmtKind::Expr(self.lower_expr(e)),
2954 StmtKind::Semi(ref e) => hir::StmtKind::Semi(self.lower_expr(e)),
2955 StmtKind::Mac(..) => panic!("shouldn't exist here"),
2957 smallvec![hir::Stmt { hir_id: self.lower_node_id(s.id), kind, span: s.span }]
2960 fn lower_block_check_mode(&mut self, b: &BlockCheckMode) -> hir::BlockCheckMode {
2962 BlockCheckMode::Default => hir::DefaultBlock,
2963 BlockCheckMode::Unsafe(u) => hir::UnsafeBlock(self.lower_unsafe_source(u)),
2967 fn lower_binding_mode(&mut self, b: &BindingMode) -> hir::BindingAnnotation {
2969 BindingMode::ByValue(Mutability::Not) => hir::BindingAnnotation::Unannotated,
2970 BindingMode::ByRef(Mutability::Not) => hir::BindingAnnotation::Ref,
2971 BindingMode::ByValue(Mutability::Mut) => hir::BindingAnnotation::Mutable,
2972 BindingMode::ByRef(Mutability::Mut) => hir::BindingAnnotation::RefMut,
2976 fn lower_unsafe_source(&mut self, u: UnsafeSource) -> hir::UnsafeSource {
2978 CompilerGenerated => hir::CompilerGenerated,
2979 UserProvided => hir::UserProvided,
2983 fn lower_trait_bound_modifier(&mut self, f: TraitBoundModifier) -> hir::TraitBoundModifier {
2985 TraitBoundModifier::None => hir::TraitBoundModifier::None,
2986 TraitBoundModifier::Maybe => hir::TraitBoundModifier::Maybe,
2990 // Helper methods for building HIR.
2992 fn stmt(&mut self, span: Span, kind: hir::StmtKind<'hir>) -> hir::Stmt<'hir> {
2993 hir::Stmt { span, kind, hir_id: self.next_id() }
2996 fn stmt_expr(&mut self, span: Span, expr: hir::Expr<'hir>) -> hir::Stmt<'hir> {
2997 self.stmt(span, hir::StmtKind::Expr(self.arena.alloc(expr)))
3004 init: Option<&'hir hir::Expr<'hir>>,
3005 pat: &'hir hir::Pat<'hir>,
3006 source: hir::LocalSource,
3007 ) -> hir::Stmt<'hir> {
3008 let local = hir::Local { attrs, hir_id: self.next_id(), init, pat, source, span, ty: None };
3009 self.stmt(span, hir::StmtKind::Local(self.arena.alloc(local)))
3012 fn block_expr(&mut self, expr: &'hir hir::Expr<'hir>) -> &'hir hir::Block<'hir> {
3013 self.block_all(expr.span, &[], Some(expr))
3019 stmts: &'hir [hir::Stmt<'hir>],
3020 expr: Option<&'hir hir::Expr<'hir>>,
3021 ) -> &'hir hir::Block<'hir> {
3022 let blk = hir::Block {
3025 hir_id: self.next_id(),
3026 rules: hir::DefaultBlock,
3028 targeted_by_break: false,
3030 self.arena.alloc(blk)
3033 /// Constructs a `true` or `false` literal pattern.
3034 fn pat_bool(&mut self, span: Span, val: bool) -> &'hir hir::Pat<'hir> {
3035 let expr = self.expr_bool(span, val);
3036 self.pat(span, hir::PatKind::Lit(expr))
3039 fn pat_ok(&mut self, span: Span, pat: &'hir hir::Pat<'hir>) -> &'hir hir::Pat<'hir> {
3040 self.pat_std_enum(span, &[sym::result, sym::Result, sym::Ok], arena_vec![self; pat])
3043 fn pat_err(&mut self, span: Span, pat: &'hir hir::Pat<'hir>) -> &'hir hir::Pat<'hir> {
3044 self.pat_std_enum(span, &[sym::result, sym::Result, sym::Err], arena_vec![self; pat])
3047 fn pat_some(&mut self, span: Span, pat: &'hir hir::Pat<'hir>) -> &'hir hir::Pat<'hir> {
3048 self.pat_std_enum(span, &[sym::option, sym::Option, sym::Some], arena_vec![self; pat])
3051 fn pat_none(&mut self, span: Span) -> &'hir hir::Pat<'hir> {
3052 self.pat_std_enum(span, &[sym::option, sym::Option, sym::None], &[])
3058 components: &[Symbol],
3059 subpats: &'hir [&'hir hir::Pat<'hir>],
3060 ) -> &'hir hir::Pat<'hir> {
3061 let path = self.std_path(span, components, None, true);
3062 let qpath = hir::QPath::Resolved(None, self.arena.alloc(path));
3063 let pt = if subpats.is_empty() {
3064 hir::PatKind::Path(qpath)
3066 hir::PatKind::TupleStruct(qpath, subpats, None)
3071 fn pat_ident(&mut self, span: Span, ident: Ident) -> (&'hir hir::Pat<'hir>, hir::HirId) {
3072 self.pat_ident_binding_mode(span, ident, hir::BindingAnnotation::Unannotated)
3075 fn pat_ident_binding_mode(
3079 bm: hir::BindingAnnotation,
3080 ) -> (&'hir hir::Pat<'hir>, hir::HirId) {
3081 let hir_id = self.next_id();
3084 self.arena.alloc(hir::Pat {
3086 kind: hir::PatKind::Binding(bm, hir_id, ident.with_span_pos(span), None),
3093 fn pat_wild(&mut self, span: Span) -> &'hir hir::Pat<'hir> {
3094 self.pat(span, hir::PatKind::Wild)
3097 fn pat(&mut self, span: Span, kind: hir::PatKind<'hir>) -> &'hir hir::Pat<'hir> {
3098 self.arena.alloc(hir::Pat { hir_id: self.next_id(), kind, span })
3101 /// Given a suffix `["b", "c", "d"]`, returns path `::std::b::c::d` when
3102 /// `fld.cx.use_std`, and `::core::b::c::d` otherwise.
3103 /// The path is also resolved according to `is_value`.
3107 components: &[Symbol],
3108 params: Option<&'hir hir::GenericArgs<'hir>>,
3110 ) -> hir::Path<'hir> {
3111 let ns = if is_value { Namespace::ValueNS } else { Namespace::TypeNS };
3112 let (path, res) = self.resolver.resolve_str_path(span, self.crate_root, components, ns);
3114 let mut segments: Vec<_> = path
3118 let res = self.expect_full_res(segment.id);
3120 ident: segment.ident,
3121 hir_id: Some(self.lower_node_id(segment.id)),
3122 res: Some(self.lower_res(res)),
3128 segments.last_mut().unwrap().args = params;
3132 res: res.map_id(|_| panic!("unexpected `NodeId`")),
3133 segments: self.arena.alloc_from_iter(segments),
3139 mut hir_id: hir::HirId,
3141 qpath: hir::QPath<'hir>,
3142 ) -> hir::Ty<'hir> {
3143 let kind = match qpath {
3144 hir::QPath::Resolved(None, path) => {
3145 // Turn trait object paths into `TyKind::TraitObject` instead.
3147 Res::Def(DefKind::Trait, _) | Res::Def(DefKind::TraitAlias, _) => {
3148 let principal = hir::PolyTraitRef {
3149 bound_generic_params: &[],
3150 trait_ref: hir::TraitRef { path, hir_ref_id: hir_id },
3154 // The original ID is taken by the `PolyTraitRef`,
3155 // so the `Ty` itself needs a different one.
3156 hir_id = self.next_id();
3157 hir::TyKind::TraitObject(
3158 arena_vec![self; principal],
3159 self.elided_dyn_bound(span),
3162 _ => hir::TyKind::Path(hir::QPath::Resolved(None, path)),
3165 _ => hir::TyKind::Path(qpath),
3168 hir::Ty { hir_id, kind, span }
3171 /// Invoked to create the lifetime argument for a type `&T`
3172 /// with no explicit lifetime.
3173 fn elided_ref_lifetime(&mut self, span: Span) -> hir::Lifetime {
3174 match self.anonymous_lifetime_mode {
3175 // Intercept when we are in an impl header or async fn and introduce an in-band
3177 // Hence `impl Foo for &u32` becomes `impl<'f> Foo for &'f u32` for some fresh
3179 AnonymousLifetimeMode::CreateParameter => {
3180 let fresh_name = self.collect_fresh_in_band_lifetime(span);
3182 hir_id: self.next_id(),
3184 name: hir::LifetimeName::Param(fresh_name),
3188 AnonymousLifetimeMode::ReportError => self.new_error_lifetime(None, span),
3190 AnonymousLifetimeMode::PassThrough => self.new_implicit_lifetime(span),
3194 /// Report an error on illegal use of `'_` or a `&T` with no explicit lifetime;
3195 /// return a "error lifetime".
3196 fn new_error_lifetime(&mut self, id: Option<NodeId>, span: Span) -> hir::Lifetime {
3197 let (id, msg, label) = match id {
3198 Some(id) => (id, "`'_` cannot be used here", "`'_` is a reserved lifetime name"),
3201 self.resolver.next_node_id(),
3202 "`&` without an explicit lifetime name cannot be used here",
3203 "explicit lifetime name needed here",
3207 let mut err = struct_span_err!(self.sess, span, E0637, "{}", msg,);
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]> {
3219 (0..count).map(|_| self.elided_path_lifetime(span)).collect()
3222 fn elided_path_lifetime(&mut self, span: Span) -> hir::Lifetime {
3223 match self.anonymous_lifetime_mode {
3224 AnonymousLifetimeMode::CreateParameter => {
3225 // We should have emitted E0726 when processing this path above
3227 .delay_span_bug(span, "expected 'implicit elided lifetime not allowed' error");
3228 let id = self.resolver.next_node_id();
3229 self.new_named_lifetime(id, span, hir::LifetimeName::Error)
3231 // `PassThrough` is the normal case.
3232 // `new_error_lifetime`, which would usually be used in the case of `ReportError`,
3233 // is unsuitable here, as these can occur from missing lifetime parameters in a
3234 // `PathSegment`, for which there is no associated `'_` or `&T` with no explicit
3235 // lifetime. Instead, we simply create an implicit lifetime, which will be checked
3236 // later, at which point a suitable error will be emitted.
3237 AnonymousLifetimeMode::PassThrough | AnonymousLifetimeMode::ReportError => {
3238 self.new_implicit_lifetime(span)
3243 /// Invoked to create the lifetime argument(s) for an elided trait object
3244 /// bound, like the bound in `Box<dyn Debug>`. This method is not invoked
3245 /// when the bound is written, even if it is written with `'_` like in
3246 /// `Box<dyn Debug + '_>`. In those cases, `lower_lifetime` is invoked.
3247 fn elided_dyn_bound(&mut self, span: Span) -> hir::Lifetime {
3248 match self.anonymous_lifetime_mode {
3249 // NB. We intentionally ignore the create-parameter mode here.
3250 // and instead "pass through" to resolve-lifetimes, which will apply
3251 // the object-lifetime-defaulting rules. Elided object lifetime defaults
3252 // do not act like other elided lifetimes. In other words, given this:
3254 // impl Foo for Box<dyn Debug>
3256 // we do not introduce a fresh `'_` to serve as the bound, but instead
3257 // ultimately translate to the equivalent of:
3259 // impl Foo for Box<dyn Debug + 'static>
3261 // `resolve_lifetime` has the code to make that happen.
3262 AnonymousLifetimeMode::CreateParameter => {}
3264 AnonymousLifetimeMode::ReportError => {
3265 // ReportError applies to explicit use of `'_`.
3268 // This is the normal case.
3269 AnonymousLifetimeMode::PassThrough => {}
3272 let r = hir::Lifetime {
3273 hir_id: self.next_id(),
3275 name: hir::LifetimeName::ImplicitObjectLifetimeDefault,
3277 debug!("elided_dyn_bound: r={:?}", r);
3281 fn new_implicit_lifetime(&mut self, span: Span) -> hir::Lifetime {
3282 hir::Lifetime { hir_id: self.next_id(), span, name: hir::LifetimeName::Implicit }
3285 fn maybe_lint_bare_trait(&mut self, span: Span, id: NodeId, is_global: bool) {
3286 // FIXME(davidtwco): This is a hack to detect macros which produce spans of the
3287 // call site which do not have a macro backtrace. See #61963.
3288 let is_macro_callsite = self
3291 .span_to_snippet(span)
3292 .map(|snippet| snippet.starts_with("#["))
3294 if !is_macro_callsite {
3295 self.resolver.lint_buffer().buffer_lint_with_diagnostic(
3296 builtin::BARE_TRAIT_OBJECTS,
3299 "trait objects without an explicit `dyn` are deprecated",
3300 builtin::BuiltinLintDiagnostics::BareTraitObject(span, is_global),
3306 fn body_ids(bodies: &BTreeMap<hir::BodyId, hir::Body<'hir>>) -> Vec<hir::BodyId> {
3307 // Sorting by span ensures that we get things in order within a
3308 // file, and also puts the files in a sensible order.
3309 let mut body_ids: Vec<_> = bodies.keys().cloned().collect();
3310 body_ids.sort_by_key(|b| bodies[b].value.span);
3314 /// Helper struct for delayed construction of GenericArgs.
3315 struct GenericArgsCtor<'hir> {
3316 args: Vec<hir::GenericArg<'hir>>,
3317 bindings: &'hir [hir::TypeBinding<'hir>],
3318 parenthesized: bool,
3321 impl GenericArgsCtor<'hir> {
3322 fn is_empty(&self) -> bool {
3323 self.args.is_empty() && self.bindings.is_empty() && !self.parenthesized
3326 fn into_generic_args(self, arena: &'hir Arena<'hir>) -> hir::GenericArgs<'hir> {
3328 args: arena.alloc_from_iter(self.args),
3329 bindings: self.bindings,
3330 parenthesized: self.parenthesized,