1 //! Lowers the AST to the HIR.
3 //! Since the AST and HIR are fairly similar, this is mostly a simple procedure,
4 //! much like a fold. Where lowering involves a bit more work things get more
5 //! interesting and there are some invariants you should know about. These mostly
6 //! concern spans and IDs.
8 //! Spans are assigned to AST nodes during parsing and then are modified during
9 //! expansion to indicate the origin of a node and the process it went through
10 //! being expanded. IDs are assigned to AST nodes just before lowering.
12 //! For the simpler lowering steps, IDs and spans should be preserved. Unlike
13 //! expansion we do not preserve the process of lowering in the spans, so spans
14 //! should not be modified here. When creating a new node (as opposed to
15 //! 'folding' an existing one), then you create a new ID using `next_id()`.
17 //! You must ensure that IDs are unique. That means that you should only use the
18 //! ID from an AST node in a single HIR node (you can assume that AST node IDs
19 //! are unique). Every new node must have a unique ID. Avoid cloning HIR nodes.
20 //! If you do, you must then set the new node's ID to a fresh one.
22 //! Spans are used for error messages and for tools to map semantics back to
23 //! source code. It is therefore not as important with spans as IDs to be strict
24 //! about use (you can't break the compiler by screwing up a span). Obviously, a
25 //! HIR node can only have a single span. But multiple nodes can have the same
26 //! span and spans don't need to be kept in order, etc. Where code is preserved
27 //! by lowering, it should have the same span as in the AST. Where HIR nodes are
28 //! new it is probably best to give a span for the whole AST node being lowered.
29 //! All nodes should have real spans, don't use dummy spans. Tools are likely to
30 //! get confused if the spans from leaf AST nodes occur in multiple places
31 //! in the HIR, especially for multiple identifiers.
33 use crate::dep_graph::DepGraph;
34 use crate::hir::{self, ParamName};
35 use crate::hir::HirVec;
36 use crate::hir::map::{DefKey, DefPathData, Definitions};
37 use crate::hir::def_id::{DefId, DefIndex, DefIndexAddressSpace, CRATE_DEF_INDEX};
38 use crate::hir::def::{Def, PathResolution, PerNS};
39 use crate::hir::{GenericArg, ConstArg};
40 use crate::lint::builtin::{self, PARENTHESIZED_PARAMS_IN_TYPES_AND_MODULES,
41 ELIDED_LIFETIMES_IN_PATHS};
42 use crate::middle::cstore::CrateStore;
43 use crate::session::Session;
44 use crate::session::config::nightly_options;
45 use crate::util::common::FN_OUTPUT_NAME;
46 use crate::util::nodemap::{DefIdMap, NodeMap};
47 use errors::Applicability;
48 use rustc_data_structures::fx::FxHashSet;
49 use rustc_data_structures::indexed_vec::IndexVec;
50 use rustc_data_structures::thin_vec::ThinVec;
51 use rustc_data_structures::sync::Lrc;
53 use std::collections::{BTreeSet, BTreeMap};
56 use smallvec::SmallVec;
61 use syntax::ext::hygiene::{Mark, SyntaxContext};
62 use syntax::print::pprust;
64 use syntax::source_map::{self, respan, CompilerDesugaringKind, Spanned};
65 use syntax::std_inject;
66 use syntax::symbol::{keywords, Symbol};
67 use syntax::tokenstream::{TokenStream, TokenTree};
68 use syntax::parse::token::Token;
69 use syntax::visit::{self, Visitor};
70 use syntax_pos::{Span, MultiSpan};
72 const HIR_ID_COUNTER_LOCKED: u32 = 0xFFFFFFFF;
74 pub struct LoweringContext<'a> {
75 crate_root: Option<&'static str>,
77 /// Used to assign ids to HIR nodes that do not directly correspond to an AST node.
80 cstore: &'a dyn CrateStore,
82 resolver: &'a mut dyn Resolver,
84 /// The items being lowered are collected here.
85 items: BTreeMap<NodeId, hir::Item>,
87 trait_items: BTreeMap<hir::TraitItemId, hir::TraitItem>,
88 impl_items: BTreeMap<hir::ImplItemId, hir::ImplItem>,
89 bodies: BTreeMap<hir::BodyId, hir::Body>,
90 exported_macros: Vec<hir::MacroDef>,
92 trait_impls: BTreeMap<DefId, Vec<NodeId>>,
93 trait_auto_impl: BTreeMap<DefId, NodeId>,
95 modules: BTreeMap<NodeId, hir::ModuleItems>,
99 catch_scopes: Vec<NodeId>,
100 loop_scopes: Vec<NodeId>,
101 is_in_loop_condition: bool,
102 is_in_trait_impl: bool,
104 /// What to do when we encounter either an "anonymous lifetime
105 /// reference". The term "anonymous" is meant to encompass both
106 /// `'_` lifetimes as well as fully elided cases where nothing is
107 /// written at all (e.g., `&T` or `std::cell::Ref<T>`).
108 anonymous_lifetime_mode: AnonymousLifetimeMode,
110 /// Used to create lifetime definitions from in-band lifetime usages.
111 /// e.g., `fn foo(x: &'x u8) -> &'x u8` to `fn foo<'x>(x: &'x u8) -> &'x u8`
112 /// When a named lifetime is encountered in a function or impl header and
113 /// has not been defined
114 /// (i.e., it doesn't appear in the in_scope_lifetimes list), it is added
115 /// to this list. The results of this list are then added to the list of
116 /// lifetime definitions in the corresponding impl or function generics.
117 lifetimes_to_define: Vec<(Span, ParamName)>,
119 /// Whether or not in-band lifetimes are being collected. This is used to
120 /// indicate whether or not we're in a place where new lifetimes will result
121 /// in in-band lifetime definitions, such a function or an impl header,
122 /// including implicit lifetimes from `impl_header_lifetime_elision`.
123 is_collecting_in_band_lifetimes: bool,
125 /// Currently in-scope lifetimes defined in impl headers, fn headers, or HRTB.
126 /// When `is_collectin_in_band_lifetimes` is true, each lifetime is checked
127 /// against this list to see if it is already in-scope, or if a definition
128 /// needs to be created for it.
129 in_scope_lifetimes: Vec<Ident>,
131 current_module: NodeId,
133 type_def_lifetime_params: DefIdMap<usize>,
135 current_hir_id_owner: Vec<(DefIndex, u32)>,
136 item_local_id_counters: NodeMap<u32>,
137 node_id_to_hir_id: IndexVec<NodeId, hir::HirId>,
141 /// Resolve a path generated by the lowerer when expanding `for`, `if let`, etc.
148 /// Obtain the resolution for a `NodeId`.
149 fn get_resolution(&mut self, id: NodeId) -> Option<PathResolution>;
151 /// Obtain the possible resolutions for the given `use` statement.
152 fn get_import(&mut self, id: NodeId) -> PerNS<Option<PathResolution>>;
154 /// We must keep the set of definitions up to date as we add nodes that weren't in the AST.
155 /// This should only return `None` during testing.
156 fn definitions(&mut self) -> &mut Definitions;
158 /// Given suffix `["b", "c", "d"]`, creates a HIR path for `[::crate_root]::b::c::d` and
159 /// resolves it based on `is_value`.
163 crate_root: Option<&str>,
170 enum ImplTraitContext<'a> {
171 /// Treat `impl Trait` as shorthand for a new universal generic parameter.
172 /// Example: `fn foo(x: impl Debug)`, where `impl Debug` is conceptually
173 /// equivalent to a fresh universal parameter like `fn foo<T: Debug>(x: T)`.
175 /// Newly generated parameters should be inserted into the given `Vec`.
176 Universal(&'a mut Vec<hir::GenericParam>),
178 /// Treat `impl Trait` as shorthand for a new existential parameter.
179 /// Example: `fn foo() -> impl Debug`, where `impl Debug` is conceptually
180 /// equivalent to a fresh existential parameter like `existential type T; fn foo() -> T`.
182 /// We optionally store a `DefId` for the parent item here so we can look up necessary
183 /// information later. It is `None` when no information about the context should be stored,
184 /// e.g., for consts and statics.
185 Existential(Option<DefId>),
187 /// `impl Trait` is not accepted in this position.
188 Disallowed(ImplTraitPosition),
191 /// Position in which `impl Trait` is disallowed. Used for error reporting.
192 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
193 enum ImplTraitPosition {
198 impl<'a> ImplTraitContext<'a> {
200 fn disallowed() -> Self {
201 ImplTraitContext::Disallowed(ImplTraitPosition::Other)
204 fn reborrow(&'b mut self) -> ImplTraitContext<'b> {
205 use self::ImplTraitContext::*;
207 Universal(params) => Universal(params),
208 Existential(did) => Existential(*did),
209 Disallowed(pos) => Disallowed(*pos),
216 cstore: &dyn CrateStore,
217 dep_graph: &DepGraph,
219 resolver: &mut dyn Resolver,
221 // We're constructing the HIR here; we don't care what we will
222 // read, since we haven't even constructed the *input* to
224 dep_graph.assert_ignored();
227 crate_root: std_inject::injected_crate_name(),
231 items: BTreeMap::new(),
232 trait_items: BTreeMap::new(),
233 impl_items: BTreeMap::new(),
234 bodies: BTreeMap::new(),
235 trait_impls: BTreeMap::new(),
236 trait_auto_impl: BTreeMap::new(),
237 modules: BTreeMap::new(),
238 exported_macros: Vec::new(),
239 catch_scopes: Vec::new(),
240 loop_scopes: Vec::new(),
241 is_in_loop_condition: false,
242 anonymous_lifetime_mode: AnonymousLifetimeMode::PassThrough,
243 type_def_lifetime_params: Default::default(),
244 current_module: CRATE_NODE_ID,
245 current_hir_id_owner: vec![(CRATE_DEF_INDEX, 0)],
246 item_local_id_counters: Default::default(),
247 node_id_to_hir_id: IndexVec::new(),
249 is_in_trait_impl: false,
250 lifetimes_to_define: Vec::new(),
251 is_collecting_in_band_lifetimes: false,
252 in_scope_lifetimes: Vec::new(),
256 #[derive(Copy, Clone, PartialEq)]
258 /// Any path in a type context.
260 /// The `module::Type` in `module::Type::method` in an expression.
265 struct LoweredNodeId {
270 enum ParenthesizedGenericArgs {
276 /// What to do when we encounter an **anonymous** lifetime
277 /// reference. Anonymous lifetime references come in two flavors. You
278 /// have implicit, or fully elided, references to lifetimes, like the
279 /// one in `&T` or `Ref<T>`, and you have `'_` lifetimes, like `&'_ T`
280 /// or `Ref<'_, T>`. These often behave the same, but not always:
282 /// - certain usages of implicit references are deprecated, like
283 /// `Ref<T>`, and we sometimes just give hard errors in those cases
285 /// - for object bounds there is a difference: `Box<dyn Foo>` is not
286 /// the same as `Box<dyn Foo + '_>`.
288 /// We describe the effects of the various modes in terms of three cases:
290 /// - **Modern** -- includes all uses of `'_`, but also the lifetime arg
291 /// of a `&` (e.g., the missing lifetime in something like `&T`)
292 /// - **Dyn Bound** -- if you have something like `Box<dyn Foo>`,
293 /// there is an elided lifetime bound (`Box<dyn Foo + 'X>`). These
294 /// elided bounds follow special rules. Note that this only covers
295 /// cases where *nothing* is written; the `'_` in `Box<dyn Foo +
296 /// '_>` is a case of "modern" elision.
297 /// - **Deprecated** -- this coverse cases like `Ref<T>`, where the lifetime
298 /// parameter to ref is completely elided. `Ref<'_, T>` would be the modern,
299 /// non-deprecated equivalent.
301 /// Currently, the handling of lifetime elision is somewhat spread out
302 /// between HIR lowering and -- as described below -- the
303 /// `resolve_lifetime` module. Often we "fallthrough" to that code by generating
304 /// an "elided" or "underscore" lifetime name. In the future, we probably want to move
305 /// everything into HIR lowering.
306 #[derive(Copy, Clone)]
307 enum AnonymousLifetimeMode {
308 /// For **Modern** cases, create a new anonymous region parameter
309 /// and reference that.
311 /// For **Dyn Bound** cases, pass responsibility to
312 /// `resolve_lifetime` code.
314 /// For **Deprecated** cases, report an error.
317 /// Give a hard error when either `&` or `'_` is written. Used to
318 /// rule out things like `where T: Foo<'_>`. Does not imply an
319 /// error on default object bounds (e.g., `Box<dyn Foo>`).
322 /// Pass responsibility to `resolve_lifetime` code for all cases.
326 struct ImplTraitTypeIdVisitor<'a> { ids: &'a mut SmallVec<[hir::ItemId; 1]> }
328 impl<'a, 'b> Visitor<'a> for ImplTraitTypeIdVisitor<'b> {
329 fn visit_ty(&mut self, ty: &'a Ty) {
335 TyKind::ImplTrait(id, _) => self.ids.push(hir::ItemId { id }),
338 visit::walk_ty(self, ty);
341 fn visit_path_segment(
344 path_segment: &'v PathSegment,
346 if let Some(ref p) = path_segment.args {
347 if let GenericArgs::Parenthesized(_) = **p {
351 visit::walk_path_segment(self, path_span, path_segment)
355 impl<'a> LoweringContext<'a> {
356 fn lower_crate(mut self, c: &Crate) -> hir::Crate {
357 /// Full-crate AST visitor that inserts into a fresh
358 /// `LoweringContext` any information that may be
359 /// needed from arbitrary locations in the crate,
360 /// e.g., the number of lifetime generic parameters
361 /// declared for every type and trait definition.
362 struct MiscCollector<'lcx, 'interner: 'lcx> {
363 lctx: &'lcx mut LoweringContext<'interner>,
366 impl<'lcx, 'interner> Visitor<'lcx> for MiscCollector<'lcx, 'interner> {
367 fn visit_item(&mut self, item: &'lcx Item) {
368 self.lctx.allocate_hir_id_counter(item.id, item);
371 ItemKind::Struct(_, ref generics)
372 | ItemKind::Union(_, ref generics)
373 | ItemKind::Enum(_, ref generics)
374 | ItemKind::Ty(_, ref generics)
375 | ItemKind::Existential(_, ref generics)
376 | ItemKind::Trait(_, _, ref generics, ..) => {
377 let def_id = self.lctx.resolver.definitions().local_def_id(item.id);
381 .filter(|param| match param.kind {
382 ast::GenericParamKind::Lifetime { .. } => true,
386 self.lctx.type_def_lifetime_params.insert(def_id, count);
390 visit::walk_item(self, item);
393 fn visit_trait_item(&mut self, item: &'lcx TraitItem) {
394 self.lctx.allocate_hir_id_counter(item.id, item);
395 visit::walk_trait_item(self, item);
398 fn visit_impl_item(&mut self, item: &'lcx ImplItem) {
399 self.lctx.allocate_hir_id_counter(item.id, item);
400 visit::walk_impl_item(self, item);
404 struct ItemLowerer<'lcx, 'interner: 'lcx> {
405 lctx: &'lcx mut LoweringContext<'interner>,
408 impl<'lcx, 'interner> ItemLowerer<'lcx, 'interner> {
409 fn with_trait_impl_ref<F>(&mut self, trait_impl_ref: &Option<TraitRef>, f: F)
411 F: FnOnce(&mut Self),
413 let old = self.lctx.is_in_trait_impl;
414 self.lctx.is_in_trait_impl = if let &None = trait_impl_ref {
420 self.lctx.is_in_trait_impl = old;
424 impl<'lcx, 'interner> Visitor<'lcx> for ItemLowerer<'lcx, 'interner> {
425 fn visit_mod(&mut self, m: &'lcx Mod, _s: Span, _attrs: &[Attribute], n: NodeId) {
426 self.lctx.modules.insert(n, hir::ModuleItems {
427 items: BTreeSet::new(),
428 trait_items: BTreeSet::new(),
429 impl_items: BTreeSet::new(),
432 let old = self.lctx.current_module;
433 self.lctx.current_module = n;
434 visit::walk_mod(self, m);
435 self.lctx.current_module = old;
438 fn visit_item(&mut self, item: &'lcx Item) {
439 let mut item_lowered = true;
440 self.lctx.with_hir_id_owner(item.id, |lctx| {
441 if let Some(hir_item) = lctx.lower_item(item) {
442 lctx.insert_item(item.id, hir_item);
444 item_lowered = false;
449 let item_generics = match self.lctx.items.get(&item.id).unwrap().node {
450 hir::ItemKind::Impl(_, _, _, ref generics, ..)
451 | hir::ItemKind::Trait(_, _, ref generics, ..) => {
452 generics.params.clone()
457 self.lctx.with_parent_impl_lifetime_defs(&item_generics, |this| {
458 let this = &mut ItemLowerer { lctx: this };
459 if let ItemKind::Impl(.., ref opt_trait_ref, _, _) = item.node {
460 this.with_trait_impl_ref(opt_trait_ref, |this| {
461 visit::walk_item(this, item)
464 visit::walk_item(this, item);
470 fn visit_trait_item(&mut self, item: &'lcx TraitItem) {
471 self.lctx.with_hir_id_owner(item.id, |lctx| {
472 let id = hir::TraitItemId { node_id: item.id };
473 let hir_item = lctx.lower_trait_item(item);
474 lctx.trait_items.insert(id, hir_item);
475 lctx.modules.get_mut(&lctx.current_module).unwrap().trait_items.insert(id);
478 visit::walk_trait_item(self, item);
481 fn visit_impl_item(&mut self, item: &'lcx ImplItem) {
482 self.lctx.with_hir_id_owner(item.id, |lctx| {
483 let id = hir::ImplItemId { node_id: item.id };
484 let hir_item = lctx.lower_impl_item(item);
485 lctx.impl_items.insert(id, hir_item);
486 lctx.modules.get_mut(&lctx.current_module).unwrap().impl_items.insert(id);
488 visit::walk_impl_item(self, item);
492 self.lower_node_id(CRATE_NODE_ID);
493 debug_assert!(self.node_id_to_hir_id[CRATE_NODE_ID] == hir::CRATE_HIR_ID);
495 visit::walk_crate(&mut MiscCollector { lctx: &mut self }, c);
496 visit::walk_crate(&mut ItemLowerer { lctx: &mut self }, c);
498 let module = self.lower_mod(&c.module);
499 let attrs = self.lower_attrs(&c.attrs);
500 let body_ids = body_ids(&self.bodies);
504 .init_node_id_to_hir_id_mapping(self.node_id_to_hir_id);
510 exported_macros: hir::HirVec::from(self.exported_macros),
512 trait_items: self.trait_items,
513 impl_items: self.impl_items,
516 trait_impls: self.trait_impls,
517 trait_auto_impl: self.trait_auto_impl,
518 modules: self.modules,
522 fn insert_item(&mut self, id: NodeId, item: hir::Item) {
523 self.items.insert(id, item);
524 self.modules.get_mut(&self.current_module).unwrap().items.insert(id);
527 fn allocate_hir_id_counter<T: Debug>(&mut self, owner: NodeId, debug: &T) -> LoweredNodeId {
528 if self.item_local_id_counters.insert(owner, 0).is_some() {
530 "Tried to allocate item_local_id_counter for {:?} twice",
534 // Always allocate the first `HirId` for the owner itself.
535 self.lower_node_id_with_owner(owner, owner)
538 fn lower_node_id_generic<F>(&mut self, ast_node_id: NodeId, alloc_hir_id: F) -> LoweredNodeId
540 F: FnOnce(&mut Self) -> hir::HirId,
542 if ast_node_id == DUMMY_NODE_ID {
543 return LoweredNodeId {
544 node_id: DUMMY_NODE_ID,
545 hir_id: hir::DUMMY_HIR_ID,
549 let min_size = ast_node_id.as_usize() + 1;
551 if min_size > self.node_id_to_hir_id.len() {
552 self.node_id_to_hir_id.resize(min_size, hir::DUMMY_HIR_ID);
555 let existing_hir_id = self.node_id_to_hir_id[ast_node_id];
557 if existing_hir_id == hir::DUMMY_HIR_ID {
558 // Generate a new `HirId`.
559 let hir_id = alloc_hir_id(self);
560 self.node_id_to_hir_id[ast_node_id] = hir_id;
562 node_id: ast_node_id,
567 node_id: ast_node_id,
568 hir_id: existing_hir_id,
573 fn with_hir_id_owner<F, T>(&mut self, owner: NodeId, f: F) -> T
575 F: FnOnce(&mut Self) -> T,
577 let counter = self.item_local_id_counters
578 .insert(owner, HIR_ID_COUNTER_LOCKED)
579 .unwrap_or_else(|| panic!("No item_local_id_counters entry for {:?}", owner));
580 let def_index = self.resolver.definitions().opt_def_index(owner).unwrap();
581 self.current_hir_id_owner.push((def_index, counter));
583 let (new_def_index, new_counter) = self.current_hir_id_owner.pop().unwrap();
585 debug_assert!(def_index == new_def_index);
586 debug_assert!(new_counter >= counter);
588 let prev = self.item_local_id_counters
589 .insert(owner, new_counter)
591 debug_assert!(prev == HIR_ID_COUNTER_LOCKED);
595 /// This method allocates a new `HirId` for the given `NodeId` and stores it in
596 /// the `LoweringContext`'s `NodeId => HirId` map.
597 /// Take care not to call this method if the resulting `HirId` is then not
598 /// actually used in the HIR, as that would trigger an assertion in the
599 /// `HirIdValidator` later on, which makes sure that all `NodeId`s got mapped
600 /// properly. Calling the method twice with the same `NodeId` is fine though.
601 fn lower_node_id(&mut self, ast_node_id: NodeId) -> LoweredNodeId {
602 self.lower_node_id_generic(ast_node_id, |this| {
603 let &mut (def_index, ref mut local_id_counter) =
604 this.current_hir_id_owner.last_mut().unwrap();
605 let local_id = *local_id_counter;
606 *local_id_counter += 1;
609 local_id: hir::ItemLocalId::from_u32(local_id),
614 fn lower_node_id_with_owner(&mut self, ast_node_id: NodeId, owner: NodeId) -> LoweredNodeId {
615 self.lower_node_id_generic(ast_node_id, |this| {
616 let local_id_counter = this
617 .item_local_id_counters
619 .expect("called lower_node_id_with_owner before allocate_hir_id_counter");
620 let local_id = *local_id_counter;
622 // We want to be sure not to modify the counter in the map while it
623 // is also on the stack. Otherwise we'll get lost updates when writing
624 // back from the stack to the map.
625 debug_assert!(local_id != HIR_ID_COUNTER_LOCKED);
627 *local_id_counter += 1;
631 .opt_def_index(owner)
632 .expect("You forgot to call `create_def_with_parent` or are lowering node ids \
633 that do not belong to the current owner");
637 local_id: hir::ItemLocalId::from_u32(local_id),
642 fn record_body(&mut self, value: hir::Expr, decl: Option<&FnDecl>) -> hir::BodyId {
643 let body = hir::Body {
644 arguments: decl.map_or(hir_vec![], |decl| {
645 decl.inputs.iter().map(|x| self.lower_arg(x)).collect()
647 is_generator: self.is_generator,
651 self.bodies.insert(id, body);
655 fn next_id(&mut self) -> LoweredNodeId {
656 self.lower_node_id(self.sess.next_node_id())
659 fn expect_full_def(&mut self, id: NodeId) -> Def {
660 self.resolver.get_resolution(id).map_or(Def::Err, |pr| {
661 if pr.unresolved_segments() != 0 {
662 bug!("path not fully resolved: {:?}", pr);
668 fn expect_full_def_from_use(&mut self, id: NodeId) -> impl Iterator<Item = Def> {
669 self.resolver.get_import(id).present_items().map(|pr| {
670 if pr.unresolved_segments() != 0 {
671 bug!("path not fully resolved: {:?}", pr);
677 fn diagnostic(&self) -> &errors::Handler {
678 self.sess.diagnostic()
681 fn str_to_ident(&self, s: &'static str) -> Ident {
682 Ident::with_empty_ctxt(Symbol::gensym(s))
685 /// Reuses the span but adds information like the kind of the desugaring and features that are
686 /// allowed inside this span.
687 fn mark_span_with_reason(
689 reason: CompilerDesugaringKind,
691 allow_internal_unstable: Option<Lrc<[Symbol]>>,
693 let mark = Mark::fresh(Mark::root());
694 mark.set_expn_info(source_map::ExpnInfo {
696 def_site: Some(span),
697 format: source_map::CompilerDesugaring(reason),
698 allow_internal_unstable,
699 allow_internal_unsafe: false,
700 local_inner_macros: false,
701 edition: source_map::hygiene::default_edition(),
703 span.with_ctxt(SyntaxContext::empty().apply_mark(mark))
706 fn with_anonymous_lifetime_mode<R>(
708 anonymous_lifetime_mode: AnonymousLifetimeMode,
709 op: impl FnOnce(&mut Self) -> R,
711 let old_anonymous_lifetime_mode = self.anonymous_lifetime_mode;
712 self.anonymous_lifetime_mode = anonymous_lifetime_mode;
713 let result = op(self);
714 self.anonymous_lifetime_mode = old_anonymous_lifetime_mode;
718 /// Creates a new hir::GenericParam for every new lifetime and
719 /// type parameter encountered while evaluating `f`. Definitions
720 /// are created with the parent provided. If no `parent_id` is
721 /// provided, no definitions will be returned.
723 /// Presuming that in-band lifetimes are enabled, then
724 /// `self.anonymous_lifetime_mode` will be updated to match the
725 /// argument while `f` is running (and restored afterwards).
726 fn collect_in_band_defs<T, F>(
729 anonymous_lifetime_mode: AnonymousLifetimeMode,
731 ) -> (Vec<hir::GenericParam>, T)
733 F: FnOnce(&mut LoweringContext<'_>) -> (Vec<hir::GenericParam>, T),
735 assert!(!self.is_collecting_in_band_lifetimes);
736 assert!(self.lifetimes_to_define.is_empty());
737 let old_anonymous_lifetime_mode = self.anonymous_lifetime_mode;
739 self.anonymous_lifetime_mode = anonymous_lifetime_mode;
740 self.is_collecting_in_band_lifetimes = true;
742 let (in_band_ty_params, res) = f(self);
744 self.is_collecting_in_band_lifetimes = false;
745 self.anonymous_lifetime_mode = old_anonymous_lifetime_mode;
747 let lifetimes_to_define = self.lifetimes_to_define.split_off(0);
749 let params = lifetimes_to_define
751 .map(|(span, hir_name)| {
752 let LoweredNodeId { node_id, hir_id } = self.next_id();
754 // Get the name we'll use to make the def-path. Note
755 // that collisions are ok here and this shouldn't
756 // really show up for end-user.
757 let (str_name, kind) = match hir_name {
758 ParamName::Plain(ident) => (
759 ident.as_interned_str(),
760 hir::LifetimeParamKind::InBand,
762 ParamName::Fresh(_) => (
763 keywords::UnderscoreLifetime.name().as_interned_str(),
764 hir::LifetimeParamKind::Elided,
766 ParamName::Error => (
767 keywords::UnderscoreLifetime.name().as_interned_str(),
768 hir::LifetimeParamKind::Error,
772 // Add a definition for the in-band lifetime def.
773 self.resolver.definitions().create_def_with_parent(
776 DefPathData::LifetimeParam(str_name),
777 DefIndexAddressSpace::High,
788 pure_wrt_drop: false,
789 kind: hir::GenericParamKind::Lifetime { kind }
792 .chain(in_band_ty_params.into_iter())
798 /// When there is a reference to some lifetime `'a`, and in-band
799 /// lifetimes are enabled, then we want to push that lifetime into
800 /// the vector of names to define later. In that case, it will get
801 /// added to the appropriate generics.
802 fn maybe_collect_in_band_lifetime(&mut self, ident: Ident) {
803 if !self.is_collecting_in_band_lifetimes {
807 if !self.sess.features_untracked().in_band_lifetimes {
811 if self.in_scope_lifetimes.contains(&ident.modern()) {
815 let hir_name = ParamName::Plain(ident);
817 if self.lifetimes_to_define.iter()
818 .any(|(_, lt_name)| lt_name.modern() == hir_name.modern()) {
822 self.lifetimes_to_define.push((ident.span, hir_name));
825 /// When we have either an elided or `'_` lifetime in an impl
826 /// header, we convert it to an in-band lifetime.
827 fn collect_fresh_in_band_lifetime(&mut self, span: Span) -> ParamName {
828 assert!(self.is_collecting_in_band_lifetimes);
829 let index = self.lifetimes_to_define.len();
830 let hir_name = ParamName::Fresh(index);
831 self.lifetimes_to_define.push((span, hir_name));
835 // Evaluates `f` with the lifetimes in `params` in-scope.
836 // This is used to track which lifetimes have already been defined, and
837 // which are new in-band lifetimes that need to have a definition created
839 fn with_in_scope_lifetime_defs<T, F>(&mut self, params: &[GenericParam], f: F) -> T
841 F: FnOnce(&mut LoweringContext<'_>) -> T,
843 let old_len = self.in_scope_lifetimes.len();
844 let lt_def_names = params.iter().filter_map(|param| match param.kind {
845 GenericParamKind::Lifetime { .. } => Some(param.ident.modern()),
848 self.in_scope_lifetimes.extend(lt_def_names);
852 self.in_scope_lifetimes.truncate(old_len);
856 // Same as the method above, but accepts `hir::GenericParam`s
857 // instead of `ast::GenericParam`s.
858 // This should only be used with generics that have already had their
859 // in-band lifetimes added. In practice, this means that this function is
860 // only used when lowering a child item of a trait or impl.
861 fn with_parent_impl_lifetime_defs<T, F>(&mut self,
862 params: &HirVec<hir::GenericParam>,
865 F: FnOnce(&mut LoweringContext<'_>) -> T,
867 let old_len = self.in_scope_lifetimes.len();
868 let lt_def_names = params.iter().filter_map(|param| match param.kind {
869 hir::GenericParamKind::Lifetime { .. } => Some(param.name.ident().modern()),
872 self.in_scope_lifetimes.extend(lt_def_names);
876 self.in_scope_lifetimes.truncate(old_len);
880 /// Appends in-band lifetime defs and argument-position `impl
881 /// Trait` defs to the existing set of generics.
883 /// Presuming that in-band lifetimes are enabled, then
884 /// `self.anonymous_lifetime_mode` will be updated to match the
885 /// argument while `f` is running (and restored afterwards).
886 fn add_in_band_defs<F, T>(
890 anonymous_lifetime_mode: AnonymousLifetimeMode,
892 ) -> (hir::Generics, T)
894 F: FnOnce(&mut LoweringContext<'_>, &mut Vec<hir::GenericParam>) -> T,
896 let (in_band_defs, (mut lowered_generics, res)) = self.with_in_scope_lifetime_defs(
899 this.collect_in_band_defs(parent_id, anonymous_lifetime_mode, |this| {
900 let mut params = Vec::new();
901 let generics = this.lower_generics(
903 ImplTraitContext::Universal(&mut params),
905 let res = f(this, &mut params);
906 (params, (generics, res))
911 lowered_generics.params = lowered_generics
918 (lowered_generics, res)
921 fn with_catch_scope<T, F>(&mut self, catch_id: NodeId, f: F) -> T
923 F: FnOnce(&mut LoweringContext<'_>) -> T,
925 let len = self.catch_scopes.len();
926 self.catch_scopes.push(catch_id);
928 let result = f(self);
931 self.catch_scopes.len(),
932 "catch scopes should be added and removed in stack order"
935 self.catch_scopes.pop().unwrap();
942 capture_clause: CaptureBy,
943 closure_node_id: NodeId,
945 body: impl FnOnce(&mut LoweringContext<'_>) -> hir::Expr,
947 let prev_is_generator = mem::replace(&mut self.is_generator, true);
948 let body_expr = body(self);
949 let span = body_expr.span;
950 let output = match ret_ty {
951 Some(ty) => FunctionRetTy::Ty(P(ty.clone())),
952 None => FunctionRetTy::Default(span),
959 let body_id = self.record_body(body_expr, Some(&decl));
960 self.is_generator = prev_is_generator;
962 let capture_clause = self.lower_capture_clause(capture_clause);
963 let closure_hir_id = self.lower_node_id(closure_node_id).hir_id;
964 let decl = self.lower_fn_decl(&decl, None, /* impl trait allowed */ false, None);
965 let generator = hir::Expr {
966 hir_id: closure_hir_id,
967 node: hir::ExprKind::Closure(capture_clause, decl, body_id, span,
968 Some(hir::GeneratorMovability::Static)),
970 attrs: ThinVec::new(),
973 let unstable_span = self.mark_span_with_reason(
974 CompilerDesugaringKind::Async,
977 Symbol::intern("gen_future"),
980 let gen_future = self.expr_std_path(
981 unstable_span, &["future", "from_generator"], None, ThinVec::new());
982 hir::ExprKind::Call(P(gen_future), hir_vec![generator])
985 fn lower_body<F>(&mut self, decl: Option<&FnDecl>, f: F) -> hir::BodyId
987 F: FnOnce(&mut LoweringContext<'_>) -> hir::Expr,
989 let prev = mem::replace(&mut self.is_generator, false);
990 let result = f(self);
991 let r = self.record_body(result, decl);
992 self.is_generator = prev;
996 fn with_loop_scope<T, F>(&mut self, loop_id: NodeId, f: F) -> T
998 F: FnOnce(&mut LoweringContext<'_>) -> T,
1000 // We're no longer in the base loop's condition; we're in another loop.
1001 let was_in_loop_condition = self.is_in_loop_condition;
1002 self.is_in_loop_condition = false;
1004 let len = self.loop_scopes.len();
1005 self.loop_scopes.push(loop_id);
1007 let result = f(self);
1010 self.loop_scopes.len(),
1011 "Loop scopes should be added and removed in stack order"
1014 self.loop_scopes.pop().unwrap();
1016 self.is_in_loop_condition = was_in_loop_condition;
1021 fn with_loop_condition_scope<T, F>(&mut self, f: F) -> T
1023 F: FnOnce(&mut LoweringContext<'_>) -> T,
1025 let was_in_loop_condition = self.is_in_loop_condition;
1026 self.is_in_loop_condition = true;
1028 let result = f(self);
1030 self.is_in_loop_condition = was_in_loop_condition;
1035 fn with_new_scopes<T, F>(&mut self, f: F) -> T
1037 F: FnOnce(&mut LoweringContext<'_>) -> T,
1039 let was_in_loop_condition = self.is_in_loop_condition;
1040 self.is_in_loop_condition = false;
1042 let catch_scopes = mem::replace(&mut self.catch_scopes, Vec::new());
1043 let loop_scopes = mem::replace(&mut self.loop_scopes, Vec::new());
1045 self.catch_scopes = catch_scopes;
1046 self.loop_scopes = loop_scopes;
1048 self.is_in_loop_condition = was_in_loop_condition;
1053 fn def_key(&mut self, id: DefId) -> DefKey {
1055 self.resolver.definitions().def_key(id.index)
1057 self.cstore.def_key(id)
1061 fn lower_label(&mut self, label: Option<Label>) -> Option<hir::Label> {
1062 label.map(|label| hir::Label {
1067 fn lower_loop_destination(&mut self, destination: Option<(NodeId, Label)>) -> hir::Destination {
1068 let target_id = match destination {
1070 if let Def::Label(loop_id) = self.expect_full_def(id) {
1071 Ok(self.lower_node_id(loop_id).node_id)
1073 Err(hir::LoopIdError::UnresolvedLabel)
1080 .map(|id| Ok(self.lower_node_id(id).node_id))
1081 .unwrap_or(Err(hir::LoopIdError::OutsideLoopScope))
1086 label: self.lower_label(destination.map(|(_, label)| label)),
1091 fn lower_attrs(&mut self, attrs: &[Attribute]) -> hir::HirVec<Attribute> {
1094 .map(|a| self.lower_attr(a))
1098 fn lower_attr(&mut self, attr: &Attribute) -> Attribute {
1099 // Note that we explicitly do not walk the path. Since we don't really
1100 // lower attributes (we use the AST version) there is nowhere to keep
1101 // the `HirId`s. We don't actually need HIR version of attributes anyway.
1105 path: attr.path.clone(),
1106 tokens: self.lower_token_stream(attr.tokens.clone()),
1107 is_sugared_doc: attr.is_sugared_doc,
1112 fn lower_token_stream(&mut self, tokens: TokenStream) -> TokenStream {
1115 .flat_map(|tree| self.lower_token_tree(tree).into_trees())
1119 fn lower_token_tree(&mut self, tree: TokenTree) -> TokenStream {
1121 TokenTree::Token(span, token) => self.lower_token(token, span),
1122 TokenTree::Delimited(span, delim, tts) => TokenTree::Delimited(
1125 self.lower_token_stream(tts),
1130 fn lower_token(&mut self, token: Token, span: Span) -> TokenStream {
1132 Token::Interpolated(nt) => {
1133 let tts = nt.to_tokenstream(&self.sess.parse_sess, span);
1134 self.lower_token_stream(tts)
1136 other => TokenTree::Token(span, other).into(),
1140 fn lower_arm(&mut self, arm: &Arm) -> hir::Arm {
1142 attrs: self.lower_attrs(&arm.attrs),
1143 pats: arm.pats.iter().map(|x| self.lower_pat(x)).collect(),
1144 guard: match arm.guard {
1145 Some(Guard::If(ref x)) => Some(hir::Guard::If(P(self.lower_expr(x)))),
1148 body: P(self.lower_expr(&arm.body)),
1152 fn lower_ty_binding(&mut self, b: &TypeBinding,
1153 itctx: ImplTraitContext<'_>) -> hir::TypeBinding {
1154 let LoweredNodeId { node_id, hir_id } = self.lower_node_id(b.id);
1160 ty: self.lower_ty(&b.ty, itctx),
1165 fn lower_generic_arg(&mut self,
1166 arg: &ast::GenericArg,
1167 itctx: ImplTraitContext<'_>)
1168 -> hir::GenericArg {
1170 ast::GenericArg::Lifetime(lt) => GenericArg::Lifetime(self.lower_lifetime(<)),
1171 ast::GenericArg::Type(ty) => GenericArg::Type(self.lower_ty_direct(&ty, itctx)),
1172 ast::GenericArg::Const(ct) => {
1173 GenericArg::Const(ConstArg {
1174 value: self.lower_anon_const(&ct),
1175 span: ct.value.span,
1181 fn lower_ty(&mut self, t: &Ty, itctx: ImplTraitContext<'_>) -> P<hir::Ty> {
1182 P(self.lower_ty_direct(t, itctx))
1185 fn lower_ty_direct(&mut self, t: &Ty, mut itctx: ImplTraitContext<'_>) -> hir::Ty {
1186 let kind = match t.node {
1187 TyKind::Infer => hir::TyKind::Infer,
1188 TyKind::Err => hir::TyKind::Err,
1189 TyKind::Slice(ref ty) => hir::TyKind::Slice(self.lower_ty(ty, itctx)),
1190 TyKind::Ptr(ref mt) => hir::TyKind::Ptr(self.lower_mt(mt, itctx)),
1191 TyKind::Rptr(ref region, ref mt) => {
1192 let span = self.sess.source_map().next_point(t.span.shrink_to_lo());
1193 let lifetime = match *region {
1194 Some(ref lt) => self.lower_lifetime(lt),
1195 None => self.elided_ref_lifetime(span),
1197 hir::TyKind::Rptr(lifetime, self.lower_mt(mt, itctx))
1199 TyKind::BareFn(ref f) => self.with_in_scope_lifetime_defs(
1202 this.with_anonymous_lifetime_mode(
1203 AnonymousLifetimeMode::PassThrough,
1205 hir::TyKind::BareFn(P(hir::BareFnTy {
1206 generic_params: this.lower_generic_params(
1208 &NodeMap::default(),
1209 ImplTraitContext::disallowed(),
1211 unsafety: this.lower_unsafety(f.unsafety),
1213 decl: this.lower_fn_decl(&f.decl, None, false, None),
1214 arg_names: this.lower_fn_args_to_names(&f.decl),
1220 TyKind::Never => hir::TyKind::Never,
1221 TyKind::Tup(ref tys) => {
1222 hir::TyKind::Tup(tys.iter().map(|ty| {
1223 self.lower_ty_direct(ty, itctx.reborrow())
1226 TyKind::Paren(ref ty) => {
1227 return self.lower_ty_direct(ty, itctx);
1229 TyKind::Path(ref qself, ref path) => {
1230 let id = self.lower_node_id(t.id);
1231 let qpath = self.lower_qpath(t.id, qself, path, ParamMode::Explicit, itctx);
1232 let ty = self.ty_path(id, t.span, qpath);
1233 if let hir::TyKind::TraitObject(..) = ty.node {
1234 self.maybe_lint_bare_trait(t.span, t.id, qself.is_none() && path.is_global());
1238 TyKind::ImplicitSelf => hir::TyKind::Path(hir::QPath::Resolved(
1241 def: self.expect_full_def(t.id),
1242 segments: hir_vec![hir::PathSegment::from_ident(keywords::SelfUpper.ident())],
1246 TyKind::Array(ref ty, ref length) => {
1247 hir::TyKind::Array(self.lower_ty(ty, itctx), self.lower_anon_const(length))
1249 TyKind::Typeof(ref expr) => {
1250 hir::TyKind::Typeof(self.lower_anon_const(expr))
1252 TyKind::TraitObject(ref bounds, kind) => {
1253 let mut lifetime_bound = None;
1256 .filter_map(|bound| match *bound {
1257 GenericBound::Trait(ref ty, TraitBoundModifier::None) => {
1258 Some(self.lower_poly_trait_ref(ty, itctx.reborrow()))
1260 GenericBound::Trait(_, TraitBoundModifier::Maybe) => None,
1261 GenericBound::Outlives(ref lifetime) => {
1262 if lifetime_bound.is_none() {
1263 lifetime_bound = Some(self.lower_lifetime(lifetime));
1269 let lifetime_bound =
1270 lifetime_bound.unwrap_or_else(|| self.elided_dyn_bound(t.span));
1271 if kind != TraitObjectSyntax::Dyn {
1272 self.maybe_lint_bare_trait(t.span, t.id, false);
1274 hir::TyKind::TraitObject(bounds, lifetime_bound)
1276 TyKind::ImplTrait(def_node_id, ref bounds) => {
1279 ImplTraitContext::Existential(fn_def_id) => {
1280 self.lower_existential_impl_trait(
1281 span, fn_def_id, def_node_id,
1282 |this| this.lower_param_bounds(bounds, itctx),
1285 ImplTraitContext::Universal(in_band_ty_params) => {
1286 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(def_node_id);
1287 // Add a definition for the in-band `Param`.
1288 let def_index = self
1291 .opt_def_index(def_node_id)
1294 let hir_bounds = self.lower_param_bounds(
1296 ImplTraitContext::Universal(in_band_ty_params),
1298 // Set the name to `impl Bound1 + Bound2`.
1299 let ident = Ident::from_str(&pprust::ty_to_string(t)).with_span_pos(span);
1300 in_band_ty_params.push(hir::GenericParam {
1302 name: ParamName::Plain(ident),
1303 pure_wrt_drop: false,
1307 kind: hir::GenericParamKind::Type {
1309 synthetic: Some(hir::SyntheticTyParamKind::ImplTrait),
1313 hir::TyKind::Path(hir::QPath::Resolved(
1317 def: Def::TyParam(DefId::local(def_index)),
1318 segments: hir_vec![hir::PathSegment::from_ident(ident)],
1322 ImplTraitContext::Disallowed(pos) => {
1323 let allowed_in = if self.sess.features_untracked()
1324 .impl_trait_in_bindings {
1325 "bindings or function and inherent method return types"
1327 "function and inherent method return types"
1329 let mut err = struct_span_err!(
1333 "`impl Trait` not allowed outside of {}",
1336 if pos == ImplTraitPosition::Binding &&
1337 nightly_options::is_nightly_build() {
1339 "add #![feature(impl_trait_in_bindings)] to the crate attributes \
1347 TyKind::Mac(_) => panic!("TyMac should have been expanded by now."),
1348 TyKind::CVarArgs => {
1349 // Create the implicit lifetime of the "spoofed" `VaList`.
1350 let span = self.sess.source_map().next_point(t.span.shrink_to_lo());
1351 let lt = self.new_implicit_lifetime(span);
1352 hir::TyKind::CVarArgs(lt)
1356 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(t.id);
1364 fn lower_existential_impl_trait(
1367 fn_def_id: Option<DefId>,
1368 exist_ty_node_id: NodeId,
1369 lower_bounds: impl FnOnce(&mut LoweringContext<'_>) -> hir::GenericBounds,
1371 // Make sure we know that some funky desugaring has been going on here.
1372 // This is a first: there is code in other places like for loop
1373 // desugaring that explicitly states that we don't want to track that.
1374 // Not tracking it makes lints in rustc and clippy very fragile as
1375 // frequently opened issues show.
1376 let exist_ty_span = self.mark_span_with_reason(
1377 CompilerDesugaringKind::ExistentialReturnType,
1382 let exist_ty_def_index = self
1385 .opt_def_index(exist_ty_node_id)
1388 self.allocate_hir_id_counter(exist_ty_node_id, &"existential impl trait");
1390 let hir_bounds = self.with_hir_id_owner(exist_ty_node_id, lower_bounds);
1392 let (lifetimes, lifetime_defs) = self.lifetimes_from_impl_trait_bounds(
1398 self.with_hir_id_owner(exist_ty_node_id, |lctx| {
1399 let LoweredNodeId { node_id: _, hir_id } = lctx.next_id();
1400 let exist_ty_item_kind = hir::ItemKind::Existential(hir::ExistTy {
1401 generics: hir::Generics {
1402 params: lifetime_defs,
1403 where_clause: hir::WhereClause {
1405 predicates: Vec::new().into(),
1410 impl_trait_fn: fn_def_id,
1412 let exist_ty_id = lctx.lower_node_id(exist_ty_node_id);
1413 // Generate an `existential type Foo: Trait;` declaration.
1414 trace!("creating existential type with id {:#?}", exist_ty_id);
1416 trace!("exist ty def index: {:#?}", exist_ty_def_index);
1417 let exist_ty_item = hir::Item {
1418 id: exist_ty_id.node_id,
1419 hir_id: exist_ty_id.hir_id,
1420 ident: keywords::Invalid.ident(),
1421 attrs: Default::default(),
1422 node: exist_ty_item_kind,
1423 vis: respan(span.shrink_to_lo(), hir::VisibilityKind::Inherited),
1424 span: exist_ty_span,
1427 // Insert the item into the global list. This usually happens
1428 // automatically for all AST items. But this existential type item
1429 // does not actually exist in the AST.
1430 lctx.insert_item(exist_ty_id.node_id, exist_ty_item);
1432 // `impl Trait` now just becomes `Foo<'a, 'b, ..>`.
1433 hir::TyKind::Def(hir::ItemId { id: exist_ty_id.node_id }, lifetimes)
1437 fn lifetimes_from_impl_trait_bounds(
1439 exist_ty_id: NodeId,
1440 parent_index: DefIndex,
1441 bounds: &hir::GenericBounds,
1442 ) -> (HirVec<hir::GenericArg>, HirVec<hir::GenericParam>) {
1443 // This visitor walks over impl trait bounds and creates defs for all lifetimes which
1444 // appear in the bounds, excluding lifetimes that are created within the bounds.
1445 // E.g., `'a`, `'b`, but not `'c` in `impl for<'c> SomeTrait<'a, 'b, 'c>`.
1446 struct ImplTraitLifetimeCollector<'r, 'a: 'r> {
1447 context: &'r mut LoweringContext<'a>,
1449 exist_ty_id: NodeId,
1450 collect_elided_lifetimes: bool,
1451 currently_bound_lifetimes: Vec<hir::LifetimeName>,
1452 already_defined_lifetimes: FxHashSet<hir::LifetimeName>,
1453 output_lifetimes: Vec<hir::GenericArg>,
1454 output_lifetime_params: Vec<hir::GenericParam>,
1457 impl<'r, 'a: 'r, 'v> hir::intravisit::Visitor<'v> for ImplTraitLifetimeCollector<'r, 'a> {
1458 fn nested_visit_map<'this>(
1460 ) -> hir::intravisit::NestedVisitorMap<'this, 'v> {
1461 hir::intravisit::NestedVisitorMap::None
1464 fn visit_generic_args(&mut self, span: Span, parameters: &'v hir::GenericArgs) {
1465 // Don't collect elided lifetimes used inside of `Fn()` syntax.
1466 if parameters.parenthesized {
1467 let old_collect_elided_lifetimes = self.collect_elided_lifetimes;
1468 self.collect_elided_lifetimes = false;
1469 hir::intravisit::walk_generic_args(self, span, parameters);
1470 self.collect_elided_lifetimes = old_collect_elided_lifetimes;
1472 hir::intravisit::walk_generic_args(self, span, parameters);
1476 fn visit_ty(&mut self, t: &'v hir::Ty) {
1477 // Don't collect elided lifetimes used inside of `fn()` syntax.
1478 if let hir::TyKind::BareFn(_) = t.node {
1479 let old_collect_elided_lifetimes = self.collect_elided_lifetimes;
1480 self.collect_elided_lifetimes = false;
1482 // Record the "stack height" of `for<'a>` lifetime bindings
1483 // to be able to later fully undo their introduction.
1484 let old_len = self.currently_bound_lifetimes.len();
1485 hir::intravisit::walk_ty(self, t);
1486 self.currently_bound_lifetimes.truncate(old_len);
1488 self.collect_elided_lifetimes = old_collect_elided_lifetimes;
1490 hir::intravisit::walk_ty(self, t)
1494 fn visit_poly_trait_ref(
1496 trait_ref: &'v hir::PolyTraitRef,
1497 modifier: hir::TraitBoundModifier,
1499 // Record the "stack height" of `for<'a>` lifetime bindings
1500 // to be able to later fully undo their introduction.
1501 let old_len = self.currently_bound_lifetimes.len();
1502 hir::intravisit::walk_poly_trait_ref(self, trait_ref, modifier);
1503 self.currently_bound_lifetimes.truncate(old_len);
1506 fn visit_generic_param(&mut self, param: &'v hir::GenericParam) {
1507 // Record the introduction of 'a in `for<'a> ...`.
1508 if let hir::GenericParamKind::Lifetime { .. } = param.kind {
1509 // Introduce lifetimes one at a time so that we can handle
1510 // cases like `fn foo<'d>() -> impl for<'a, 'b: 'a, 'c: 'b + 'd>`.
1511 let lt_name = hir::LifetimeName::Param(param.name);
1512 self.currently_bound_lifetimes.push(lt_name);
1515 hir::intravisit::walk_generic_param(self, param);
1518 fn visit_lifetime(&mut self, lifetime: &'v hir::Lifetime) {
1519 let name = match lifetime.name {
1520 hir::LifetimeName::Implicit | hir::LifetimeName::Underscore => {
1521 if self.collect_elided_lifetimes {
1522 // Use `'_` for both implicit and underscore lifetimes in
1523 // `abstract type Foo<'_>: SomeTrait<'_>;`.
1524 hir::LifetimeName::Underscore
1529 hir::LifetimeName::Param(_) => lifetime.name,
1530 hir::LifetimeName::Error | hir::LifetimeName::Static => return,
1533 if !self.currently_bound_lifetimes.contains(&name)
1534 && !self.already_defined_lifetimes.contains(&name) {
1535 self.already_defined_lifetimes.insert(name);
1537 let LoweredNodeId { node_id: _, hir_id } = self.context.next_id();
1538 self.output_lifetimes.push(hir::GenericArg::Lifetime(hir::Lifetime {
1540 span: lifetime.span,
1544 // We need to manually create the ids here, because the
1545 // definitions will go into the explicit `existential type`
1546 // declaration and thus need to have their owner set to that item
1547 let def_node_id = self.context.sess.next_node_id();
1548 let LoweredNodeId { node_id: _, hir_id } =
1549 self.context.lower_node_id_with_owner(def_node_id, self.exist_ty_id);
1550 self.context.resolver.definitions().create_def_with_parent(
1553 DefPathData::LifetimeParam(name.ident().as_interned_str()),
1554 DefIndexAddressSpace::High,
1559 let (name, kind) = match name {
1560 hir::LifetimeName::Underscore => (
1561 hir::ParamName::Plain(keywords::UnderscoreLifetime.ident()),
1562 hir::LifetimeParamKind::Elided,
1564 hir::LifetimeName::Param(param_name) => (
1566 hir::LifetimeParamKind::Explicit,
1568 _ => bug!("expected LifetimeName::Param or ParamName::Plain"),
1571 self.output_lifetime_params.push(hir::GenericParam {
1574 span: lifetime.span,
1575 pure_wrt_drop: false,
1578 kind: hir::GenericParamKind::Lifetime { kind }
1584 let mut lifetime_collector = ImplTraitLifetimeCollector {
1586 parent: parent_index,
1588 collect_elided_lifetimes: true,
1589 currently_bound_lifetimes: Vec::new(),
1590 already_defined_lifetimes: FxHashSet::default(),
1591 output_lifetimes: Vec::new(),
1592 output_lifetime_params: Vec::new(),
1595 for bound in bounds {
1596 hir::intravisit::walk_param_bound(&mut lifetime_collector, &bound);
1600 lifetime_collector.output_lifetimes.into(),
1601 lifetime_collector.output_lifetime_params.into(),
1605 fn lower_foreign_mod(&mut self, fm: &ForeignMod) -> hir::ForeignMod {
1610 .map(|x| self.lower_foreign_item(x))
1615 fn lower_global_asm(&mut self, ga: &GlobalAsm) -> P<hir::GlobalAsm> {
1622 fn lower_variant(&mut self, v: &Variant) -> hir::Variant {
1624 node: hir::VariantKind {
1625 ident: v.node.ident,
1626 attrs: self.lower_attrs(&v.node.attrs),
1627 data: self.lower_variant_data(&v.node.data),
1628 disr_expr: v.node.disr_expr.as_ref().map(|e| self.lower_anon_const(e)),
1637 qself: &Option<QSelf>,
1639 param_mode: ParamMode,
1640 mut itctx: ImplTraitContext<'_>,
1642 let qself_position = qself.as_ref().map(|q| q.position);
1643 let qself = qself.as_ref().map(|q| self.lower_ty(&q.ty, itctx.reborrow()));
1645 let resolution = self.resolver
1647 .unwrap_or_else(|| PathResolution::new(Def::Err));
1649 let proj_start = p.segments.len() - resolution.unresolved_segments();
1650 let path = P(hir::Path {
1651 def: resolution.base_def(),
1652 segments: p.segments[..proj_start]
1655 .map(|(i, segment)| {
1656 let param_mode = match (qself_position, param_mode) {
1657 (Some(j), ParamMode::Optional) if i < j => {
1658 // This segment is part of the trait path in a
1659 // qualified path - one of `a`, `b` or `Trait`
1660 // in `<X as a::b::Trait>::T::U::method`.
1666 // Figure out if this is a type/trait segment,
1667 // which may need lifetime elision performed.
1668 let parent_def_id = |this: &mut Self, def_id: DefId| DefId {
1669 krate: def_id.krate,
1670 index: this.def_key(def_id).parent.expect("missing parent"),
1672 let type_def_id = match resolution.base_def() {
1673 Def::AssociatedTy(def_id) if i + 2 == proj_start => {
1674 Some(parent_def_id(self, def_id))
1676 Def::Variant(def_id) if i + 1 == proj_start => {
1677 Some(parent_def_id(self, def_id))
1680 | Def::Union(def_id)
1682 | Def::TyAlias(def_id)
1683 | Def::Trait(def_id) if i + 1 == proj_start =>
1689 let parenthesized_generic_args = match resolution.base_def() {
1690 // `a::b::Trait(Args)`
1691 Def::Trait(..) if i + 1 == proj_start => ParenthesizedGenericArgs::Ok,
1692 // `a::b::Trait(Args)::TraitItem`
1693 Def::Method(..) | Def::AssociatedConst(..) | Def::AssociatedTy(..)
1694 if i + 2 == proj_start =>
1696 ParenthesizedGenericArgs::Ok
1698 // Avoid duplicated errors.
1699 Def::Err => ParenthesizedGenericArgs::Ok,
1705 | Def::Variant(..) if i + 1 == proj_start =>
1707 ParenthesizedGenericArgs::Err
1709 // A warning for now, for compatibility reasons
1710 _ => ParenthesizedGenericArgs::Warn,
1713 let num_lifetimes = type_def_id.map_or(0, |def_id| {
1714 if let Some(&n) = self.type_def_lifetime_params.get(&def_id) {
1717 assert!(!def_id.is_local());
1719 self.cstore.item_generics_cloned_untracked(def_id, self.sess);
1720 let n = item_generics.own_counts().lifetimes;
1721 self.type_def_lifetime_params.insert(def_id, n);
1724 self.lower_path_segment(
1729 parenthesized_generic_args,
1738 // Simple case, either no projections, or only fully-qualified.
1739 // E.g., `std::mem::size_of` or `<I as Iterator>::Item`.
1740 if resolution.unresolved_segments() == 0 {
1741 return hir::QPath::Resolved(qself, path);
1744 // Create the innermost type that we're projecting from.
1745 let mut ty = if path.segments.is_empty() {
1746 // If the base path is empty that means there exists a
1747 // syntactical `Self`, e.g., `&i32` in `<&i32>::clone`.
1748 qself.expect("missing QSelf for <T>::...")
1750 // Otherwise, the base path is an implicit `Self` type path,
1751 // e.g., `Vec` in `Vec::new` or `<I as Iterator>::Item` in
1752 // `<I as Iterator>::Item::default`.
1753 let new_id = self.next_id();
1754 P(self.ty_path(new_id, p.span, hir::QPath::Resolved(qself, path)))
1757 // Anything after the base path are associated "extensions",
1758 // out of which all but the last one are associated types,
1759 // e.g., for `std::vec::Vec::<T>::IntoIter::Item::clone`:
1760 // * base path is `std::vec::Vec<T>`
1761 // * "extensions" are `IntoIter`, `Item` and `clone`
1762 // * type nodes are:
1763 // 1. `std::vec::Vec<T>` (created above)
1764 // 2. `<std::vec::Vec<T>>::IntoIter`
1765 // 3. `<<std::vec::Vec<T>>::IntoIter>::Item`
1766 // * final path is `<<<std::vec::Vec<T>>::IntoIter>::Item>::clone`
1767 for (i, segment) in p.segments.iter().enumerate().skip(proj_start) {
1768 let segment = P(self.lower_path_segment(
1773 ParenthesizedGenericArgs::Warn,
1777 let qpath = hir::QPath::TypeRelative(ty, segment);
1779 // It's finished, return the extension of the right node type.
1780 if i == p.segments.len() - 1 {
1784 // Wrap the associated extension in another type node.
1785 let new_id = self.next_id();
1786 ty = P(self.ty_path(new_id, p.span, qpath));
1789 // We should've returned in the for loop above.
1792 "lower_qpath: no final extension segment in {}..{}",
1798 fn lower_path_extra(
1802 param_mode: ParamMode,
1803 explicit_owner: Option<NodeId>,
1807 segments: p.segments
1810 self.lower_path_segment(
1815 ParenthesizedGenericArgs::Err,
1816 ImplTraitContext::disallowed(),
1825 fn lower_path(&mut self, id: NodeId, p: &Path, param_mode: ParamMode) -> hir::Path {
1826 let def = self.expect_full_def(id);
1827 self.lower_path_extra(def, p, param_mode, None)
1830 fn lower_path_segment(
1833 segment: &PathSegment,
1834 param_mode: ParamMode,
1835 expected_lifetimes: usize,
1836 parenthesized_generic_args: ParenthesizedGenericArgs,
1837 itctx: ImplTraitContext<'_>,
1838 explicit_owner: Option<NodeId>,
1839 ) -> hir::PathSegment {
1840 let (mut generic_args, infer_types) = if let Some(ref generic_args) = segment.args {
1841 let msg = "parenthesized type parameters may only be used with a `Fn` trait";
1842 match **generic_args {
1843 GenericArgs::AngleBracketed(ref data) => {
1844 self.lower_angle_bracketed_parameter_data(data, param_mode, itctx)
1846 GenericArgs::Parenthesized(ref data) => match parenthesized_generic_args {
1847 ParenthesizedGenericArgs::Ok => self.lower_parenthesized_parameter_data(data),
1848 ParenthesizedGenericArgs::Warn => {
1849 self.sess.buffer_lint(
1850 PARENTHESIZED_PARAMS_IN_TYPES_AND_MODULES,
1855 (hir::GenericArgs::none(), true)
1857 ParenthesizedGenericArgs::Err => {
1858 let mut err = struct_span_err!(self.sess, data.span, E0214, "{}", msg);
1859 err.span_label(data.span, "only `Fn` traits may use parentheses");
1860 if let Ok(snippet) = self.sess.source_map().span_to_snippet(data.span) {
1861 // Do not suggest going from `Trait()` to `Trait<>`
1862 if data.inputs.len() > 0 {
1863 err.span_suggestion(
1865 "use angle brackets instead",
1866 format!("<{}>", &snippet[1..snippet.len() - 1]),
1867 Applicability::MaybeIncorrect,
1872 (self.lower_angle_bracketed_parameter_data(
1873 &data.as_angle_bracketed_args(),
1881 self.lower_angle_bracketed_parameter_data(&Default::default(), param_mode, itctx)
1884 let has_lifetimes = generic_args.args.iter().any(|arg| match arg {
1885 GenericArg::Lifetime(_) => true,
1888 let first_generic_span = generic_args.args.iter().map(|a| a.span())
1889 .chain(generic_args.bindings.iter().map(|b| b.span)).next();
1890 if !generic_args.parenthesized && !has_lifetimes {
1892 self.elided_path_lifetimes(path_span, expected_lifetimes)
1894 .map(|lt| GenericArg::Lifetime(lt))
1895 .chain(generic_args.args.into_iter())
1897 if expected_lifetimes > 0 && param_mode == ParamMode::Explicit {
1898 let anon_lt_suggestion = vec!["'_"; expected_lifetimes].join(", ");
1899 let no_ty_args = generic_args.args.len() == expected_lifetimes;
1900 let no_bindings = generic_args.bindings.is_empty();
1901 let (incl_angl_brckt, insertion_span, suggestion) = if no_ty_args && no_bindings {
1902 // If there are no (non-implicit) generic args or associated-type
1903 // bindings, our suggestion includes the angle brackets.
1904 (true, path_span.shrink_to_hi(), format!("<{}>", anon_lt_suggestion))
1906 // Otherwise—sorry, this is kind of gross—we need to infer the
1907 // place to splice in the `'_, ` from the generics that do exist.
1908 let first_generic_span = first_generic_span
1909 .expect("already checked that type args or bindings exist");
1910 (false, first_generic_span.shrink_to_lo(), format!("{}, ", anon_lt_suggestion))
1912 self.sess.buffer_lint_with_diagnostic(
1913 ELIDED_LIFETIMES_IN_PATHS,
1916 "hidden lifetime parameters in types are deprecated",
1917 builtin::BuiltinLintDiagnostics::ElidedLifetimesInPaths(
1918 expected_lifetimes, path_span, incl_angl_brckt, insertion_span, suggestion
1924 let def = self.expect_full_def(segment.id);
1925 let id = if let Some(owner) = explicit_owner {
1926 self.lower_node_id_with_owner(segment.id, owner)
1928 self.lower_node_id(segment.id)
1931 "lower_path_segment: ident={:?} original-id={:?} new-id={:?}",
1932 segment.ident, segment.id, id,
1935 hir::PathSegment::new(
1945 fn lower_angle_bracketed_parameter_data(
1947 data: &AngleBracketedArgs,
1948 param_mode: ParamMode,
1949 mut itctx: ImplTraitContext<'_>,
1950 ) -> (hir::GenericArgs, bool) {
1951 let &AngleBracketedArgs { ref args, ref bindings, .. } = data;
1952 let has_types = args.iter().any(|arg| match arg {
1953 ast::GenericArg::Type(_) => true,
1957 args: args.iter().map(|a| self.lower_generic_arg(a, itctx.reborrow())).collect(),
1958 bindings: bindings.iter().map(|b| self.lower_ty_binding(b, itctx.reborrow())).collect(),
1959 parenthesized: false,
1961 !has_types && param_mode == ParamMode::Optional)
1964 fn lower_parenthesized_parameter_data(
1966 data: &ParenthesizedArgs,
1967 ) -> (hir::GenericArgs, bool) {
1968 // Switch to `PassThrough` mode for anonymous lifetimes: this
1969 // means that we permit things like `&Ref<T>`, where `Ref` has
1970 // a hidden lifetime parameter. This is needed for backwards
1971 // compatibility, even in contexts like an impl header where
1972 // we generally don't permit such things (see #51008).
1973 self.with_anonymous_lifetime_mode(
1974 AnonymousLifetimeMode::PassThrough,
1976 let &ParenthesizedArgs { ref inputs, ref output, span } = data;
1979 .map(|ty| this.lower_ty_direct(ty, ImplTraitContext::disallowed()))
1981 let mk_tup = |this: &mut Self, tys, span| {
1982 let LoweredNodeId { node_id: _, hir_id } = this.next_id();
1983 hir::Ty { node: hir::TyKind::Tup(tys), hir_id, span }
1985 let LoweredNodeId { node_id, hir_id } = this.next_id();
1989 args: hir_vec![GenericArg::Type(mk_tup(this, inputs, span))],
1994 ident: Ident::from_str(FN_OUTPUT_NAME),
1997 .map(|ty| this.lower_ty(&ty, ImplTraitContext::disallowed()))
1998 .unwrap_or_else(|| P(mk_tup(this, hir::HirVec::new(), span))),
1999 span: output.as_ref().map_or(span, |ty| ty.span),
2002 parenthesized: true,
2010 fn lower_local(&mut self, l: &Local) -> (hir::Local, SmallVec<[hir::ItemId; 1]>) {
2011 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(l.id);
2012 let mut ids = SmallVec::<[hir::ItemId; 1]>::new();
2013 if self.sess.features_untracked().impl_trait_in_bindings {
2014 if let Some(ref ty) = l.ty {
2015 let mut visitor = ImplTraitTypeIdVisitor { ids: &mut ids };
2016 visitor.visit_ty(ty);
2019 let parent_def_id = DefId::local(self.current_hir_id_owner.last().unwrap().0);
2024 .map(|t| self.lower_ty(t,
2025 if self.sess.features_untracked().impl_trait_in_bindings {
2026 ImplTraitContext::Existential(Some(parent_def_id))
2028 ImplTraitContext::Disallowed(ImplTraitPosition::Binding)
2031 pat: self.lower_pat(&l.pat),
2032 init: l.init.as_ref().map(|e| P(self.lower_expr(e))),
2034 attrs: l.attrs.clone(),
2035 source: hir::LocalSource::Normal,
2039 fn lower_mutability(&mut self, m: Mutability) -> hir::Mutability {
2041 Mutability::Mutable => hir::MutMutable,
2042 Mutability::Immutable => hir::MutImmutable,
2046 fn lower_arg(&mut self, arg: &Arg) -> hir::Arg {
2047 let LoweredNodeId { node_id, hir_id } = self.lower_node_id(arg.id);
2051 pat: self.lower_pat(&arg.pat),
2055 fn lower_fn_args_to_names(&mut self, decl: &FnDecl) -> hir::HirVec<Ident> {
2058 .map(|arg| match arg.pat.node {
2059 PatKind::Ident(_, ident, _) => ident,
2060 _ => Ident::new(keywords::Invalid.name(), arg.pat.span),
2065 // Lowers a function declaration.
2067 // decl: the unlowered (ast) function declaration.
2068 // fn_def_id: if `Some`, impl Trait arguments are lowered into generic parameters on the
2069 // given DefId, otherwise impl Trait is disallowed. Must be `Some` if
2070 // make_ret_async is also `Some`.
2071 // impl_trait_return_allow: determines whether impl Trait can be used in return position.
2072 // This guards against trait declarations and implementations where impl Trait is
2074 // make_ret_async: if `Some`, converts `-> T` into `-> impl Future<Output = T>` in the
2075 // return type. This is used for `async fn` declarations. The `NodeId` is the id of the
2076 // return type impl Trait item.
2080 mut in_band_ty_params: Option<(DefId, &mut Vec<hir::GenericParam>)>,
2081 impl_trait_return_allow: bool,
2082 make_ret_async: Option<NodeId>,
2083 ) -> P<hir::FnDecl> {
2084 let inputs = decl.inputs
2087 if let Some((_, ref mut ibty)) = in_band_ty_params {
2088 self.lower_ty_direct(&arg.ty, ImplTraitContext::Universal(ibty))
2090 self.lower_ty_direct(&arg.ty, ImplTraitContext::disallowed())
2093 .collect::<HirVec<_>>();
2095 let output = if let Some(ret_id) = make_ret_async {
2096 self.lower_async_fn_ret_ty(
2099 in_band_ty_params.expect("make_ret_async but no fn_def_id").0,
2104 FunctionRetTy::Ty(ref ty) => match in_band_ty_params {
2105 Some((def_id, _)) if impl_trait_return_allow => {
2106 hir::Return(self.lower_ty(ty,
2107 ImplTraitContext::Existential(Some(def_id))))
2110 hir::Return(self.lower_ty(ty, ImplTraitContext::disallowed()))
2113 FunctionRetTy::Default(span) => hir::DefaultReturn(span),
2120 c_variadic: decl.c_variadic,
2121 implicit_self: decl.inputs.get(0).map_or(
2122 hir::ImplicitSelfKind::None,
2124 let is_mutable_pat = match arg.pat.node {
2125 PatKind::Ident(BindingMode::ByValue(mt), _, _) |
2126 PatKind::Ident(BindingMode::ByRef(mt), _, _) =>
2127 mt == Mutability::Mutable,
2132 TyKind::ImplicitSelf if is_mutable_pat => hir::ImplicitSelfKind::Mut,
2133 TyKind::ImplicitSelf => hir::ImplicitSelfKind::Imm,
2134 // Given we are only considering `ImplicitSelf` types, we needn't consider
2135 // the case where we have a mutable pattern to a reference as that would
2136 // no longer be an `ImplicitSelf`.
2137 TyKind::Rptr(_, ref mt) if mt.ty.node.is_implicit_self() &&
2138 mt.mutbl == ast::Mutability::Mutable =>
2139 hir::ImplicitSelfKind::MutRef,
2140 TyKind::Rptr(_, ref mt) if mt.ty.node.is_implicit_self() =>
2141 hir::ImplicitSelfKind::ImmRef,
2142 _ => hir::ImplicitSelfKind::None,
2149 // Transform `-> T` into `-> impl Future<Output = T>` for `async fn`
2151 // fn_span: the span of the async function declaration. Used for error reporting.
2152 // inputs: lowered types of arguments to the function. Used to collect lifetimes.
2153 // output: unlowered output type (`T` in `-> T`)
2154 // fn_def_id: DefId of the parent function. Used to create child impl trait definition.
2155 fn lower_async_fn_ret_ty(
2158 output: &FunctionRetTy,
2160 return_impl_trait_id: NodeId,
2161 ) -> hir::FunctionRetTy {
2162 // Get lifetimes used in the input arguments to the function. Our output type must also
2163 // have the same lifetime.
2164 // FIXME(cramertj): multiple different lifetimes are not allowed because
2165 // `impl Trait + 'a + 'b` doesn't allow for capture `'a` and `'b` where neither is a subset
2166 // of the other. We really want some new lifetime that is a subset of all input lifetimes,
2167 // but that doesn't exist at the moment.
2169 struct AsyncFnLifetimeCollector<'r, 'a: 'r> {
2170 context: &'r mut LoweringContext<'a>,
2171 // Lifetimes bound by HRTB.
2172 currently_bound_lifetimes: Vec<hir::LifetimeName>,
2173 // Whether to count elided lifetimes.
2174 // Disabled inside of `Fn` or `fn` syntax.
2175 collect_elided_lifetimes: bool,
2176 // The lifetime found.
2177 // Multiple different or elided lifetimes cannot appear in async fn for now.
2178 output_lifetime: Option<(hir::LifetimeName, Span)>,
2181 impl<'r, 'a: 'r, 'v> hir::intravisit::Visitor<'v> for AsyncFnLifetimeCollector<'r, 'a> {
2182 fn nested_visit_map<'this>(
2184 ) -> hir::intravisit::NestedVisitorMap<'this, 'v> {
2185 hir::intravisit::NestedVisitorMap::None
2188 fn visit_generic_args(&mut self, span: Span, parameters: &'v hir::GenericArgs) {
2189 // Don't collect elided lifetimes used inside of `Fn()` syntax.
2190 if parameters.parenthesized {
2191 let old_collect_elided_lifetimes = self.collect_elided_lifetimes;
2192 self.collect_elided_lifetimes = false;
2193 hir::intravisit::walk_generic_args(self, span, parameters);
2194 self.collect_elided_lifetimes = old_collect_elided_lifetimes;
2196 hir::intravisit::walk_generic_args(self, span, parameters);
2200 fn visit_ty(&mut self, t: &'v hir::Ty) {
2201 // Don't collect elided lifetimes used inside of `fn()` syntax.
2202 if let &hir::TyKind::BareFn(_) = &t.node {
2203 let old_collect_elided_lifetimes = self.collect_elided_lifetimes;
2204 self.collect_elided_lifetimes = false;
2206 // Record the "stack height" of `for<'a>` lifetime bindings
2207 // to be able to later fully undo their introduction.
2208 let old_len = self.currently_bound_lifetimes.len();
2209 hir::intravisit::walk_ty(self, t);
2210 self.currently_bound_lifetimes.truncate(old_len);
2212 self.collect_elided_lifetimes = old_collect_elided_lifetimes;
2214 hir::intravisit::walk_ty(self, t);
2218 fn visit_poly_trait_ref(
2220 trait_ref: &'v hir::PolyTraitRef,
2221 modifier: hir::TraitBoundModifier,
2223 // Record the "stack height" of `for<'a>` lifetime bindings
2224 // to be able to later fully undo their introduction.
2225 let old_len = self.currently_bound_lifetimes.len();
2226 hir::intravisit::walk_poly_trait_ref(self, trait_ref, modifier);
2227 self.currently_bound_lifetimes.truncate(old_len);
2230 fn visit_generic_param(&mut self, param: &'v hir::GenericParam) {
2231 // Record the introduction of 'a in `for<'a> ...`
2232 if let hir::GenericParamKind::Lifetime { .. } = param.kind {
2233 // Introduce lifetimes one at a time so that we can handle
2234 // cases like `fn foo<'d>() -> impl for<'a, 'b: 'a, 'c: 'b + 'd>`
2235 let lt_name = hir::LifetimeName::Param(param.name);
2236 self.currently_bound_lifetimes.push(lt_name);
2239 hir::intravisit::walk_generic_param(self, param);
2242 fn visit_lifetime(&mut self, lifetime: &'v hir::Lifetime) {
2243 let name = match lifetime.name {
2244 hir::LifetimeName::Implicit | hir::LifetimeName::Underscore => {
2245 if self.collect_elided_lifetimes {
2246 // Use `'_` for both implicit and underscore lifetimes in
2247 // `abstract type Foo<'_>: SomeTrait<'_>;`
2248 hir::LifetimeName::Underscore
2253 hir::LifetimeName::Param(_) => lifetime.name,
2254 hir::LifetimeName::Error | hir::LifetimeName::Static => return,
2257 if !self.currently_bound_lifetimes.contains(&name) {
2258 if let Some((current_lt_name, current_lt_span)) = self.output_lifetime {
2259 // We don't currently have a reliable way to desugar `async fn` with
2260 // multiple potentially unrelated input lifetimes into
2261 // `-> impl Trait + 'lt`, so we report an error in this case.
2262 if current_lt_name != name {
2265 MultiSpan::from_spans(vec![current_lt_span, lifetime.span]),
2267 "multiple different lifetimes used in arguments of `async fn`",
2269 .span_label(current_lt_span, "first lifetime here")
2270 .span_label(lifetime.span, "different lifetime here")
2271 .help("`async fn` can only accept borrowed values \
2272 with identical lifetimes")
2274 } else if current_lt_name.is_elided() && name.is_elided() {
2277 MultiSpan::from_spans(vec![current_lt_span, lifetime.span]),
2279 "multiple elided lifetimes used in arguments of `async fn`",
2281 .span_label(current_lt_span, "first lifetime here")
2282 .span_label(lifetime.span, "different lifetime here")
2283 .help("consider giving these arguments named lifetimes")
2287 self.output_lifetime = Some((name, lifetime.span));
2293 let bound_lifetime = {
2294 let mut lifetime_collector = AsyncFnLifetimeCollector {
2296 currently_bound_lifetimes: Vec::new(),
2297 collect_elided_lifetimes: true,
2298 output_lifetime: None,
2302 hir::intravisit::walk_ty(&mut lifetime_collector, arg);
2304 lifetime_collector.output_lifetime
2307 let span = match output {
2308 FunctionRetTy::Ty(ty) => ty.span,
2309 FunctionRetTy::Default(span) => *span,
2312 let impl_trait_ty = self.lower_existential_impl_trait(
2313 span, Some(fn_def_id), return_impl_trait_id, |this| {
2314 let output_ty = match output {
2315 FunctionRetTy::Ty(ty) => {
2316 this.lower_ty(ty, ImplTraitContext::Existential(Some(fn_def_id)))
2318 FunctionRetTy::Default(span) => {
2319 let LoweredNodeId { node_id: _, hir_id } = this.next_id();
2322 node: hir::TyKind::Tup(hir_vec![]),
2329 let LoweredNodeId { node_id, hir_id } = this.next_id();
2330 let future_params = P(hir::GenericArgs {
2332 bindings: hir_vec![hir::TypeBinding {
2333 ident: Ident::from_str(FN_OUTPUT_NAME),
2339 parenthesized: false,
2343 this.std_path(span, &["future", "Future"], Some(future_params), false);
2345 let LoweredNodeId { node_id, hir_id } = this.next_id();
2346 let mut bounds = vec![
2347 hir::GenericBound::Trait(
2349 trait_ref: hir::TraitRef {
2354 bound_generic_params: hir_vec![],
2357 hir::TraitBoundModifier::None
2361 if let Some((name, span)) = bound_lifetime {
2362 let LoweredNodeId { node_id: _, hir_id } = this.next_id();
2363 bounds.push(hir::GenericBound::Outlives(
2364 hir::Lifetime { hir_id, name, span }));
2367 hir::HirVec::from(bounds)
2370 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
2371 let impl_trait_ty = P(hir::Ty {
2372 node: impl_trait_ty,
2377 hir::FunctionRetTy::Return(impl_trait_ty)
2380 fn lower_param_bound(
2383 itctx: ImplTraitContext<'_>,
2384 ) -> hir::GenericBound {
2386 GenericBound::Trait(ref ty, modifier) => {
2387 hir::GenericBound::Trait(
2388 self.lower_poly_trait_ref(ty, itctx),
2389 self.lower_trait_bound_modifier(modifier),
2392 GenericBound::Outlives(ref lifetime) => {
2393 hir::GenericBound::Outlives(self.lower_lifetime(lifetime))
2398 fn lower_lifetime(&mut self, l: &Lifetime) -> hir::Lifetime {
2399 let span = l.ident.span;
2401 ident if ident.name == keywords::StaticLifetime.name() =>
2402 self.new_named_lifetime(l.id, span, hir::LifetimeName::Static),
2403 ident if ident.name == keywords::UnderscoreLifetime.name() =>
2404 match self.anonymous_lifetime_mode {
2405 AnonymousLifetimeMode::CreateParameter => {
2406 let fresh_name = self.collect_fresh_in_band_lifetime(span);
2407 self.new_named_lifetime(l.id, span, hir::LifetimeName::Param(fresh_name))
2410 AnonymousLifetimeMode::PassThrough => {
2411 self.new_named_lifetime(l.id, span, hir::LifetimeName::Underscore)
2414 AnonymousLifetimeMode::ReportError => self.new_error_lifetime(Some(l.id), span),
2417 self.maybe_collect_in_band_lifetime(ident);
2418 let param_name = ParamName::Plain(ident);
2419 self.new_named_lifetime(l.id, span, hir::LifetimeName::Param(param_name))
2424 fn new_named_lifetime(
2428 name: hir::LifetimeName,
2429 ) -> hir::Lifetime {
2430 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(id);
2439 fn lower_generic_params(
2441 params: &[GenericParam],
2442 add_bounds: &NodeMap<Vec<GenericBound>>,
2443 mut itctx: ImplTraitContext<'_>,
2444 ) -> hir::HirVec<hir::GenericParam> {
2445 params.iter().map(|param| {
2446 self.lower_generic_param(param, add_bounds, itctx.reborrow())
2450 fn lower_generic_param(&mut self,
2451 param: &GenericParam,
2452 add_bounds: &NodeMap<Vec<GenericBound>>,
2453 mut itctx: ImplTraitContext<'_>)
2454 -> hir::GenericParam {
2455 let mut bounds = self.with_anonymous_lifetime_mode(
2456 AnonymousLifetimeMode::ReportError,
2457 |this| this.lower_param_bounds(¶m.bounds, itctx.reborrow()),
2460 let (name, kind) = match param.kind {
2461 GenericParamKind::Lifetime => {
2462 let was_collecting_in_band = self.is_collecting_in_band_lifetimes;
2463 self.is_collecting_in_band_lifetimes = false;
2465 let lt = self.with_anonymous_lifetime_mode(
2466 AnonymousLifetimeMode::ReportError,
2467 |this| this.lower_lifetime(&Lifetime { id: param.id, ident: param.ident }),
2469 let param_name = match lt.name {
2470 hir::LifetimeName::Param(param_name) => param_name,
2471 hir::LifetimeName::Implicit
2472 | hir::LifetimeName::Underscore
2473 | hir::LifetimeName::Static => hir::ParamName::Plain(lt.name.ident()),
2474 hir::LifetimeName::Error => ParamName::Error,
2477 let kind = hir::GenericParamKind::Lifetime {
2478 kind: hir::LifetimeParamKind::Explicit
2481 self.is_collecting_in_band_lifetimes = was_collecting_in_band;
2485 GenericParamKind::Type { ref default, .. } => {
2486 // Don't expose `Self` (recovered "keyword used as ident" parse error).
2487 // `rustc::ty` expects `Self` to be only used for a trait's `Self`.
2488 // Instead, use `gensym("Self")` to create a distinct name that looks the same.
2489 let ident = if param.ident.name == keywords::SelfUpper.name() {
2490 param.ident.gensym()
2495 let add_bounds = add_bounds.get(¶m.id).map_or(&[][..], |x| &x);
2496 if !add_bounds.is_empty() {
2497 let params = self.lower_param_bounds(add_bounds, itctx.reborrow()).into_iter();
2498 bounds = bounds.into_iter()
2503 let kind = hir::GenericParamKind::Type {
2504 default: default.as_ref().map(|x| {
2505 self.lower_ty(x, ImplTraitContext::disallowed())
2507 synthetic: param.attrs.iter()
2508 .filter(|attr| attr.check_name("rustc_synthetic"))
2509 .map(|_| hir::SyntheticTyParamKind::ImplTrait)
2513 (hir::ParamName::Plain(ident), kind)
2515 GenericParamKind::Const { ref ty } => {
2516 (hir::ParamName::Plain(param.ident), hir::GenericParamKind::Const {
2517 ty: self.lower_ty(&ty, ImplTraitContext::disallowed()),
2522 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(param.id);
2527 span: param.ident.span,
2528 pure_wrt_drop: attr::contains_name(¶m.attrs, "may_dangle"),
2529 attrs: self.lower_attrs(¶m.attrs),
2537 generics: &Generics,
2538 itctx: ImplTraitContext<'_>)
2541 // Collect `?Trait` bounds in where clause and move them to parameter definitions.
2542 // FIXME: this could probably be done with less rightward drift. Also looks like two control
2543 // paths where report_error is called are also the only paths that advance to after
2544 // the match statement, so the error reporting could probably just be moved there.
2545 let mut add_bounds: NodeMap<Vec<_>> = Default::default();
2546 for pred in &generics.where_clause.predicates {
2547 if let WherePredicate::BoundPredicate(ref bound_pred) = *pred {
2548 'next_bound: for bound in &bound_pred.bounds {
2549 if let GenericBound::Trait(_, TraitBoundModifier::Maybe) = *bound {
2550 let report_error = |this: &mut Self| {
2551 this.diagnostic().span_err(
2552 bound_pred.bounded_ty.span,
2553 "`?Trait` bounds are only permitted at the \
2554 point where a type parameter is declared",
2557 // Check if the where clause type is a plain type parameter.
2558 match bound_pred.bounded_ty.node {
2559 TyKind::Path(None, ref path)
2560 if path.segments.len() == 1
2561 && bound_pred.bound_generic_params.is_empty() =>
2563 if let Some(Def::TyParam(def_id)) = self.resolver
2564 .get_resolution(bound_pred.bounded_ty.id)
2565 .map(|d| d.base_def())
2567 if let Some(node_id) =
2568 self.resolver.definitions().as_local_node_id(def_id)
2570 for param in &generics.params {
2572 GenericParamKind::Type { .. } => {
2573 if node_id == param.id {
2574 add_bounds.entry(param.id)
2576 .push(bound.clone());
2577 continue 'next_bound;
2587 _ => report_error(self),
2595 params: self.lower_generic_params(&generics.params, &add_bounds, itctx),
2596 where_clause: self.lower_where_clause(&generics.where_clause),
2597 span: generics.span,
2601 fn lower_where_clause(&mut self, wc: &WhereClause) -> hir::WhereClause {
2602 self.with_anonymous_lifetime_mode(
2603 AnonymousLifetimeMode::ReportError,
2605 let LoweredNodeId { node_id: _, hir_id } = this.lower_node_id(wc.id);
2609 predicates: wc.predicates
2611 .map(|predicate| this.lower_where_predicate(predicate))
2618 fn lower_where_predicate(&mut self, pred: &WherePredicate) -> hir::WherePredicate {
2620 WherePredicate::BoundPredicate(WhereBoundPredicate {
2621 ref bound_generic_params,
2626 self.with_in_scope_lifetime_defs(
2627 &bound_generic_params,
2629 hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
2630 bound_generic_params: this.lower_generic_params(
2631 bound_generic_params,
2632 &NodeMap::default(),
2633 ImplTraitContext::disallowed(),
2635 bounded_ty: this.lower_ty(bounded_ty, ImplTraitContext::disallowed()),
2638 .filter_map(|bound| match *bound {
2639 // Ignore `?Trait` bounds.
2640 // They were copied into type parameters already.
2641 GenericBound::Trait(_, TraitBoundModifier::Maybe) => None,
2642 _ => Some(this.lower_param_bound(
2644 ImplTraitContext::disallowed(),
2653 WherePredicate::RegionPredicate(WhereRegionPredicate {
2657 }) => hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate {
2659 lifetime: self.lower_lifetime(lifetime),
2660 bounds: self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
2662 WherePredicate::EqPredicate(WhereEqPredicate {
2668 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(id);
2670 hir::WherePredicate::EqPredicate(hir::WhereEqPredicate {
2672 lhs_ty: self.lower_ty(lhs_ty, ImplTraitContext::disallowed()),
2673 rhs_ty: self.lower_ty(rhs_ty, ImplTraitContext::disallowed()),
2680 fn lower_variant_data(&mut self, vdata: &VariantData) -> hir::VariantData {
2682 VariantData::Struct(ref fields, id) => {
2683 let LoweredNodeId { node_id, hir_id } = self.lower_node_id(id);
2685 hir::VariantData::Struct(
2689 .map(|f| self.lower_struct_field(f))
2695 VariantData::Tuple(ref fields, id) => {
2696 let LoweredNodeId { node_id, hir_id } = self.lower_node_id(id);
2698 hir::VariantData::Tuple(
2702 .map(|f| self.lower_struct_field(f))
2708 VariantData::Unit(id) => {
2709 let LoweredNodeId { node_id, hir_id } = self.lower_node_id(id);
2711 hir::VariantData::Unit(node_id, hir_id)
2716 fn lower_trait_ref(&mut self, p: &TraitRef, itctx: ImplTraitContext<'_>) -> hir::TraitRef {
2717 let path = match self.lower_qpath(p.ref_id, &None, &p.path, ParamMode::Explicit, itctx) {
2718 hir::QPath::Resolved(None, path) => path.and_then(|path| path),
2719 qpath => bug!("lower_trait_ref: unexpected QPath `{:?}`", qpath),
2721 let LoweredNodeId { node_id, hir_id } = self.lower_node_id(p.ref_id);
2729 fn lower_poly_trait_ref(
2732 mut itctx: ImplTraitContext<'_>,
2733 ) -> hir::PolyTraitRef {
2734 let bound_generic_params = self.lower_generic_params(
2735 &p.bound_generic_params,
2736 &NodeMap::default(),
2739 let trait_ref = self.with_parent_impl_lifetime_defs(
2740 &bound_generic_params,
2741 |this| this.lower_trait_ref(&p.trait_ref, itctx),
2745 bound_generic_params,
2751 fn lower_struct_field(&mut self, (index, f): (usize, &StructField)) -> hir::StructField {
2752 let LoweredNodeId { node_id, hir_id } = self.lower_node_id(f.id);
2758 ident: match f.ident {
2759 Some(ident) => ident,
2760 // FIXME(jseyfried): positional field hygiene
2761 None => Ident::new(Symbol::intern(&index.to_string()), f.span),
2763 vis: self.lower_visibility(&f.vis, None),
2764 ty: self.lower_ty(&f.ty, ImplTraitContext::disallowed()),
2765 attrs: self.lower_attrs(&f.attrs),
2769 fn lower_field(&mut self, f: &Field) -> hir::Field {
2770 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
2775 expr: P(self.lower_expr(&f.expr)),
2777 is_shorthand: f.is_shorthand,
2781 fn lower_mt(&mut self, mt: &MutTy, itctx: ImplTraitContext<'_>) -> hir::MutTy {
2783 ty: self.lower_ty(&mt.ty, itctx),
2784 mutbl: self.lower_mutability(mt.mutbl),
2788 fn lower_param_bounds(&mut self, bounds: &[GenericBound], mut itctx: ImplTraitContext<'_>)
2789 -> hir::GenericBounds {
2790 bounds.iter().map(|bound| self.lower_param_bound(bound, itctx.reborrow())).collect()
2793 fn lower_block(&mut self, b: &Block, targeted_by_break: bool) -> P<hir::Block> {
2794 let mut expr = None;
2796 let mut stmts = vec![];
2798 for (index, stmt) in b.stmts.iter().enumerate() {
2799 if index == b.stmts.len() - 1 {
2800 if let StmtKind::Expr(ref e) = stmt.node {
2801 expr = Some(P(self.lower_expr(e)));
2803 stmts.extend(self.lower_stmt(stmt));
2806 stmts.extend(self.lower_stmt(stmt));
2810 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(b.id);
2814 stmts: stmts.into(),
2816 rules: self.lower_block_check_mode(&b.rules),
2822 fn lower_async_body(
2828 self.lower_body(Some(decl), |this| {
2829 if let IsAsync::Async { closure_id, .. } = asyncness {
2830 let async_expr = this.make_async_expr(
2831 CaptureBy::Value, closure_id, None,
2833 let body = this.lower_block(body, false);
2834 this.expr_block(body, ThinVec::new())
2836 this.expr(body.span, async_expr, ThinVec::new())
2838 let body = this.lower_block(body, false);
2839 this.expr_block(body, ThinVec::new())
2848 attrs: &hir::HirVec<Attribute>,
2849 vis: &mut hir::Visibility,
2851 ) -> hir::ItemKind {
2853 ItemKind::ExternCrate(orig_name) => hir::ItemKind::ExternCrate(orig_name),
2854 ItemKind::Use(ref use_tree) => {
2855 // Start with an empty prefix
2858 span: use_tree.span,
2861 self.lower_use_tree(use_tree, &prefix, id, vis, ident, attrs)
2863 ItemKind::Static(ref t, m, ref e) => {
2864 let value = self.lower_body(None, |this| this.lower_expr(e));
2865 hir::ItemKind::Static(
2868 if self.sess.features_untracked().impl_trait_in_bindings {
2869 ImplTraitContext::Existential(None)
2871 ImplTraitContext::Disallowed(ImplTraitPosition::Binding)
2874 self.lower_mutability(m),
2878 ItemKind::Const(ref t, ref e) => {
2879 let value = self.lower_body(None, |this| this.lower_expr(e));
2880 hir::ItemKind::Const(
2883 if self.sess.features_untracked().impl_trait_in_bindings {
2884 ImplTraitContext::Existential(None)
2886 ImplTraitContext::Disallowed(ImplTraitPosition::Binding)
2892 ItemKind::Fn(ref decl, header, ref generics, ref body) => {
2893 let fn_def_id = self.resolver.definitions().local_def_id(id);
2894 self.with_new_scopes(|this| {
2895 // Note: we don't need to change the return type from `T` to
2896 // `impl Future<Output = T>` here because lower_body
2897 // only cares about the input argument patterns in the function
2898 // declaration (decl), not the return types.
2899 let body_id = this.lower_async_body(decl, header.asyncness.node, body);
2901 let (generics, fn_decl) = this.add_in_band_defs(
2904 AnonymousLifetimeMode::PassThrough,
2905 |this, idty| this.lower_fn_decl(
2907 Some((fn_def_id, idty)),
2909 header.asyncness.node.opt_return_id()
2915 this.lower_fn_header(header),
2921 ItemKind::Mod(ref m) => hir::ItemKind::Mod(self.lower_mod(m)),
2922 ItemKind::ForeignMod(ref nm) => hir::ItemKind::ForeignMod(self.lower_foreign_mod(nm)),
2923 ItemKind::GlobalAsm(ref ga) => hir::ItemKind::GlobalAsm(self.lower_global_asm(ga)),
2924 ItemKind::Ty(ref t, ref generics) => hir::ItemKind::Ty(
2925 self.lower_ty(t, ImplTraitContext::disallowed()),
2926 self.lower_generics(generics, ImplTraitContext::disallowed()),
2928 ItemKind::Existential(ref b, ref generics) => hir::ItemKind::Existential(hir::ExistTy {
2929 generics: self.lower_generics(generics, ImplTraitContext::disallowed()),
2930 bounds: self.lower_param_bounds(b, ImplTraitContext::disallowed()),
2931 impl_trait_fn: None,
2933 ItemKind::Enum(ref enum_definition, ref generics) => hir::ItemKind::Enum(
2935 variants: enum_definition
2938 .map(|x| self.lower_variant(x))
2941 self.lower_generics(generics, ImplTraitContext::disallowed()),
2943 ItemKind::Struct(ref struct_def, ref generics) => {
2944 let struct_def = self.lower_variant_data(struct_def);
2945 hir::ItemKind::Struct(
2947 self.lower_generics(generics, ImplTraitContext::disallowed()),
2950 ItemKind::Union(ref vdata, ref generics) => {
2951 let vdata = self.lower_variant_data(vdata);
2952 hir::ItemKind::Union(
2954 self.lower_generics(generics, ImplTraitContext::disallowed()),
2966 let def_id = self.resolver.definitions().local_def_id(id);
2968 // Lower the "impl header" first. This ordering is important
2969 // for in-band lifetimes! Consider `'a` here:
2971 // impl Foo<'a> for u32 {
2972 // fn method(&'a self) { .. }
2975 // Because we start by lowering the `Foo<'a> for u32`
2976 // part, we will add `'a` to the list of generics on
2977 // the impl. When we then encounter it later in the
2978 // method, it will not be considered an in-band
2979 // lifetime to be added, but rather a reference to a
2981 let (generics, (trait_ref, lowered_ty)) = self.add_in_band_defs(
2984 AnonymousLifetimeMode::CreateParameter,
2986 let trait_ref = trait_ref.as_ref().map(|trait_ref| {
2987 this.lower_trait_ref(trait_ref, ImplTraitContext::disallowed())
2990 if let Some(ref trait_ref) = trait_ref {
2991 if let Def::Trait(def_id) = trait_ref.path.def {
2992 this.trait_impls.entry(def_id).or_default().push(id);
2996 let lowered_ty = this.lower_ty(ty, ImplTraitContext::disallowed());
2998 (trait_ref, lowered_ty)
3002 let new_impl_items = self.with_in_scope_lifetime_defs(
3003 &ast_generics.params,
3007 .map(|item| this.lower_impl_item_ref(item))
3012 hir::ItemKind::Impl(
3013 self.lower_unsafety(unsafety),
3014 self.lower_impl_polarity(polarity),
3015 self.lower_defaultness(defaultness, true /* [1] */),
3022 ItemKind::Trait(is_auto, unsafety, ref generics, ref bounds, ref items) => {
3023 let bounds = self.lower_param_bounds(bounds, ImplTraitContext::disallowed());
3026 .map(|item| self.lower_trait_item_ref(item))
3028 hir::ItemKind::Trait(
3029 self.lower_is_auto(is_auto),
3030 self.lower_unsafety(unsafety),
3031 self.lower_generics(generics, ImplTraitContext::disallowed()),
3036 ItemKind::TraitAlias(ref generics, ref bounds) => hir::ItemKind::TraitAlias(
3037 self.lower_generics(generics, ImplTraitContext::disallowed()),
3038 self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
3040 ItemKind::MacroDef(..) | ItemKind::Mac(..) => panic!("Shouldn't still be around"),
3043 // [1] `defaultness.has_value()` is never called for an `impl`, always `true` in order to
3044 // not cause an assertion failure inside the `lower_defaultness` function.
3052 vis: &mut hir::Visibility,
3054 attrs: &hir::HirVec<Attribute>,
3055 ) -> hir::ItemKind {
3056 debug!("lower_use_tree(tree={:?})", tree);
3057 debug!("lower_use_tree: vis = {:?}", vis);
3059 let path = &tree.prefix;
3060 let segments = prefix
3063 .chain(path.segments.iter())
3068 UseTreeKind::Simple(rename, id1, id2) => {
3069 *ident = tree.ident();
3071 // First, apply the prefix to the path.
3072 let mut path = Path {
3077 // Correctly resolve `self` imports.
3078 if path.segments.len() > 1
3079 && path.segments.last().unwrap().ident.name == keywords::SelfLower.name()
3081 let _ = path.segments.pop();
3082 if rename.is_none() {
3083 *ident = path.segments.last().unwrap().ident;
3087 let parent_def_index = self.current_hir_id_owner.last().unwrap().0;
3088 let mut defs = self.expect_full_def_from_use(id);
3089 // We want to return *something* from this function, so hold onto the first item
3091 let ret_def = defs.next().unwrap_or(Def::Err);
3093 // Here, we are looping over namespaces, if they exist for the definition
3094 // being imported. We only handle type and value namespaces because we
3095 // won't be dealing with macros in the rest of the compiler.
3096 // Essentially a single `use` which imports two names is desugared into
3098 for (def, &new_node_id) in defs.zip([id1, id2].iter()) {
3099 let vis = vis.clone();
3100 let ident = ident.clone();
3101 let mut path = path.clone();
3102 for seg in &mut path.segments {
3103 seg.id = self.sess.next_node_id();
3105 let span = path.span;
3106 self.resolver.definitions().create_def_with_parent(
3110 DefIndexAddressSpace::High,
3113 self.allocate_hir_id_counter(new_node_id, &path);
3115 self.with_hir_id_owner(new_node_id, |this| {
3116 let new_id = this.lower_node_id(new_node_id);
3118 this.lower_path_extra(def, &path, ParamMode::Explicit, None);
3119 let item = hir::ItemKind::Use(P(path), hir::UseKind::Single);
3120 let vis_kind = match vis.node {
3121 hir::VisibilityKind::Public => hir::VisibilityKind::Public,
3122 hir::VisibilityKind::Crate(sugar) => hir::VisibilityKind::Crate(sugar),
3123 hir::VisibilityKind::Inherited => hir::VisibilityKind::Inherited,
3124 hir::VisibilityKind::Restricted { ref path, id: _, hir_id: _ } => {
3125 let id = this.next_id();
3126 let path = this.renumber_segment_ids(path);
3127 hir::VisibilityKind::Restricted {
3134 let vis = respan(vis.span, vis_kind);
3140 hir_id: new_id.hir_id,
3142 attrs: attrs.clone(),
3152 P(self.lower_path_extra(ret_def, &path, ParamMode::Explicit, None));
3153 hir::ItemKind::Use(path, hir::UseKind::Single)
3155 UseTreeKind::Glob => {
3156 let path = P(self.lower_path(
3162 ParamMode::Explicit,
3164 hir::ItemKind::Use(path, hir::UseKind::Glob)
3166 UseTreeKind::Nested(ref trees) => {
3167 // Nested imports are desugared into simple imports.
3168 // So, if we start with
3171 // pub(x) use foo::{a, b};
3174 // we will create three items:
3177 // pub(x) use foo::a;
3178 // pub(x) use foo::b;
3179 // pub(x) use foo::{}; // <-- this is called the `ListStem`
3182 // The first two are produced by recursively invoking
3183 // `lower_use_tree` (and indeed there may be things
3184 // like `use foo::{a::{b, c}}` and so forth). They
3185 // wind up being directly added to
3186 // `self.items`. However, the structure of this
3187 // function also requires us to return one item, and
3188 // for that we return the `{}` import (called the
3193 span: prefix.span.to(path.span),
3196 // Add all the nested `PathListItem`s to the HIR.
3197 for &(ref use_tree, id) in trees {
3198 self.allocate_hir_id_counter(id, &use_tree);
3203 } = self.lower_node_id(id);
3205 let mut vis = vis.clone();
3206 let mut ident = ident.clone();
3207 let mut prefix = prefix.clone();
3209 // Give the segments new node-ids since they are being cloned.
3210 for seg in &mut prefix.segments {
3211 seg.id = self.sess.next_node_id();
3214 // Each `use` import is an item and thus are owners of the
3215 // names in the path. Up to this point the nested import is
3216 // the current owner, since we want each desugared import to
3217 // own its own names, we have to adjust the owner before
3218 // lowering the rest of the import.
3219 self.with_hir_id_owner(new_id, |this| {
3220 let item = this.lower_use_tree(use_tree,
3227 let vis_kind = match vis.node {
3228 hir::VisibilityKind::Public => hir::VisibilityKind::Public,
3229 hir::VisibilityKind::Crate(sugar) => hir::VisibilityKind::Crate(sugar),
3230 hir::VisibilityKind::Inherited => hir::VisibilityKind::Inherited,
3231 hir::VisibilityKind::Restricted { ref path, id: _, hir_id: _ } => {
3232 let id = this.next_id();
3233 let path = this.renumber_segment_ids(path);
3234 hir::VisibilityKind::Restricted {
3241 let vis = respan(vis.span, vis_kind);
3249 attrs: attrs.clone(),
3252 span: use_tree.span,
3258 // Subtle and a bit hacky: we lower the privacy level
3259 // of the list stem to "private" most of the time, but
3260 // not for "restricted" paths. The key thing is that
3261 // we don't want it to stay as `pub` (with no caveats)
3262 // because that affects rustdoc and also the lints
3263 // about `pub` items. But we can't *always* make it
3264 // private -- particularly not for restricted paths --
3265 // because it contains node-ids that would then be
3266 // unused, failing the check that HirIds are "densely
3269 hir::VisibilityKind::Public |
3270 hir::VisibilityKind::Crate(_) |
3271 hir::VisibilityKind::Inherited => {
3272 *vis = respan(prefix.span.shrink_to_lo(), hir::VisibilityKind::Inherited);
3274 hir::VisibilityKind::Restricted { .. } => {
3275 // Do nothing here, as described in the comment on the match.
3279 let def = self.expect_full_def_from_use(id).next().unwrap_or(Def::Err);
3280 let path = P(self.lower_path_extra(def, &prefix, ParamMode::Explicit, None));
3281 hir::ItemKind::Use(path, hir::UseKind::ListStem)
3286 /// Paths like the visibility path in `pub(super) use foo::{bar, baz}` are repeated
3287 /// many times in the HIR tree; for each occurrence, we need to assign distinct
3288 /// `NodeId`s. (See, e.g., #56128.)
3289 fn renumber_segment_ids(&mut self, path: &P<hir::Path>) -> P<hir::Path> {
3290 debug!("renumber_segment_ids(path = {:?})", path);
3291 let mut path = path.clone();
3292 for seg in path.segments.iter_mut() {
3293 if seg.id.is_some() {
3294 let next_id = self.next_id();
3295 seg.id = Some(next_id.node_id);
3296 seg.hir_id = Some(next_id.hir_id);
3302 fn lower_trait_item(&mut self, i: &TraitItem) -> hir::TraitItem {
3303 let LoweredNodeId { node_id, hir_id } = self.lower_node_id(i.id);
3304 let trait_item_def_id = self.resolver.definitions().local_def_id(node_id);
3306 let (generics, node) = match i.node {
3307 TraitItemKind::Const(ref ty, ref default) => (
3308 self.lower_generics(&i.generics, ImplTraitContext::disallowed()),
3309 hir::TraitItemKind::Const(
3310 self.lower_ty(ty, ImplTraitContext::disallowed()),
3313 .map(|x| self.lower_body(None, |this| this.lower_expr(x))),
3316 TraitItemKind::Method(ref sig, None) => {
3317 let names = self.lower_fn_args_to_names(&sig.decl);
3318 let (generics, sig) = self.lower_method_sig(
3325 (generics, hir::TraitItemKind::Method(sig, hir::TraitMethod::Required(names)))
3327 TraitItemKind::Method(ref sig, Some(ref body)) => {
3328 let body_id = self.lower_body(Some(&sig.decl), |this| {
3329 let body = this.lower_block(body, false);
3330 this.expr_block(body, ThinVec::new())
3332 let (generics, sig) = self.lower_method_sig(
3339 (generics, hir::TraitItemKind::Method(sig, hir::TraitMethod::Provided(body_id)))
3341 TraitItemKind::Type(ref bounds, ref default) => (
3342 self.lower_generics(&i.generics, ImplTraitContext::disallowed()),
3343 hir::TraitItemKind::Type(
3344 self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
3347 .map(|x| self.lower_ty(x, ImplTraitContext::disallowed())),
3350 TraitItemKind::Macro(..) => panic!("Shouldn't exist any more"),
3357 attrs: self.lower_attrs(&i.attrs),
3364 fn lower_trait_item_ref(&mut self, i: &TraitItem) -> hir::TraitItemRef {
3365 let (kind, has_default) = match i.node {
3366 TraitItemKind::Const(_, ref default) => {
3367 (hir::AssociatedItemKind::Const, default.is_some())
3369 TraitItemKind::Type(_, ref default) => {
3370 (hir::AssociatedItemKind::Type, default.is_some())
3372 TraitItemKind::Method(ref sig, ref default) => (
3373 hir::AssociatedItemKind::Method {
3374 has_self: sig.decl.has_self(),
3378 TraitItemKind::Macro(..) => unimplemented!(),
3381 id: hir::TraitItemId { node_id: i.id },
3384 defaultness: self.lower_defaultness(Defaultness::Default, has_default),
3389 fn lower_impl_item(&mut self, i: &ImplItem) -> hir::ImplItem {
3390 let LoweredNodeId { node_id, hir_id } = self.lower_node_id(i.id);
3391 let impl_item_def_id = self.resolver.definitions().local_def_id(node_id);
3393 let (generics, node) = match i.node {
3394 ImplItemKind::Const(ref ty, ref expr) => {
3395 let body_id = self.lower_body(None, |this| this.lower_expr(expr));
3397 self.lower_generics(&i.generics, ImplTraitContext::disallowed()),
3398 hir::ImplItemKind::Const(
3399 self.lower_ty(ty, ImplTraitContext::disallowed()),
3404 ImplItemKind::Method(ref sig, ref body) => {
3405 let body_id = self.lower_async_body(&sig.decl, sig.header.asyncness.node, body);
3406 let impl_trait_return_allow = !self.is_in_trait_impl;
3407 let (generics, sig) = self.lower_method_sig(
3411 impl_trait_return_allow,
3412 sig.header.asyncness.node.opt_return_id(),
3414 (generics, hir::ImplItemKind::Method(sig, body_id))
3416 ImplItemKind::Type(ref ty) => (
3417 self.lower_generics(&i.generics, ImplTraitContext::disallowed()),
3418 hir::ImplItemKind::Type(self.lower_ty(ty, ImplTraitContext::disallowed())),
3420 ImplItemKind::Existential(ref bounds) => (
3421 self.lower_generics(&i.generics, ImplTraitContext::disallowed()),
3422 hir::ImplItemKind::Existential(
3423 self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
3426 ImplItemKind::Macro(..) => panic!("Shouldn't exist any more"),
3433 attrs: self.lower_attrs(&i.attrs),
3435 vis: self.lower_visibility(&i.vis, None),
3436 defaultness: self.lower_defaultness(i.defaultness, true /* [1] */),
3441 // [1] since `default impl` is not yet implemented, this is always true in impls
3444 fn lower_impl_item_ref(&mut self, i: &ImplItem) -> hir::ImplItemRef {
3446 id: hir::ImplItemId { node_id: i.id },
3449 vis: self.lower_visibility(&i.vis, Some(i.id)),
3450 defaultness: self.lower_defaultness(i.defaultness, true /* [1] */),
3451 kind: match i.node {
3452 ImplItemKind::Const(..) => hir::AssociatedItemKind::Const,
3453 ImplItemKind::Type(..) => hir::AssociatedItemKind::Type,
3454 ImplItemKind::Existential(..) => hir::AssociatedItemKind::Existential,
3455 ImplItemKind::Method(ref sig, _) => hir::AssociatedItemKind::Method {
3456 has_self: sig.decl.has_self(),
3458 ImplItemKind::Macro(..) => unimplemented!(),
3462 // [1] since `default impl` is not yet implemented, this is always true in impls
3465 fn lower_mod(&mut self, m: &Mod) -> hir::Mod {
3468 item_ids: m.items.iter().flat_map(|x| self.lower_item_id(x)).collect(),
3472 fn lower_item_id(&mut self, i: &Item) -> SmallVec<[hir::ItemId; 1]> {
3474 ItemKind::Use(ref use_tree) => {
3475 let mut vec = smallvec![hir::ItemId { id: i.id }];
3476 self.lower_item_id_use_tree(use_tree, i.id, &mut vec);
3479 ItemKind::MacroDef(..) => SmallVec::new(),
3481 ItemKind::Impl(.., None, _, _) => smallvec![hir::ItemId { id: i.id }],
3482 ItemKind::Static(ref ty, ..) => {
3483 let mut ids = smallvec![hir::ItemId { id: i.id }];
3484 if self.sess.features_untracked().impl_trait_in_bindings {
3485 let mut visitor = ImplTraitTypeIdVisitor { ids: &mut ids };
3486 visitor.visit_ty(ty);
3490 ItemKind::Const(ref ty, ..) => {
3491 let mut ids = smallvec![hir::ItemId { id: i.id }];
3492 if self.sess.features_untracked().impl_trait_in_bindings {
3493 let mut visitor = ImplTraitTypeIdVisitor { ids: &mut ids };
3494 visitor.visit_ty(ty);
3498 _ => smallvec![hir::ItemId { id: i.id }],
3502 fn lower_item_id_use_tree(&mut self,
3505 vec: &mut SmallVec<[hir::ItemId; 1]>)
3508 UseTreeKind::Nested(ref nested_vec) => for &(ref nested, id) in nested_vec {
3509 vec.push(hir::ItemId { id });
3510 self.lower_item_id_use_tree(nested, id, vec);
3512 UseTreeKind::Glob => {}
3513 UseTreeKind::Simple(_, id1, id2) => {
3514 for (_, &id) in self.expect_full_def_from_use(base_id)
3516 .zip([id1, id2].iter())
3518 vec.push(hir::ItemId { id });
3524 pub fn lower_item(&mut self, i: &Item) -> Option<hir::Item> {
3525 let mut ident = i.ident;
3526 let mut vis = self.lower_visibility(&i.vis, None);
3527 let attrs = self.lower_attrs(&i.attrs);
3528 if let ItemKind::MacroDef(ref def) = i.node {
3529 if !def.legacy || attr::contains_name(&i.attrs, "macro_export") ||
3530 attr::contains_name(&i.attrs, "rustc_doc_only_macro") {
3531 let body = self.lower_token_stream(def.stream());
3532 let hir_id = self.lower_node_id(i.id).hir_id;
3533 self.exported_macros.push(hir::MacroDef {
3546 let node = self.lower_item_kind(i.id, &mut ident, &attrs, &mut vis, &i.node);
3548 let LoweredNodeId { node_id, hir_id } = self.lower_node_id(i.id);
3561 fn lower_foreign_item(&mut self, i: &ForeignItem) -> hir::ForeignItem {
3562 let LoweredNodeId { node_id, hir_id } = self.lower_node_id(i.id);
3563 let def_id = self.resolver.definitions().local_def_id(node_id);
3568 attrs: self.lower_attrs(&i.attrs),
3569 node: match i.node {
3570 ForeignItemKind::Fn(ref fdec, ref generics) => {
3571 let (generics, (fn_dec, fn_args)) = self.add_in_band_defs(
3574 AnonymousLifetimeMode::PassThrough,
3577 // Disallow impl Trait in foreign items
3578 this.lower_fn_decl(fdec, None, false, None),
3579 this.lower_fn_args_to_names(fdec),
3584 hir::ForeignItemKind::Fn(fn_dec, fn_args, generics)
3586 ForeignItemKind::Static(ref t, m) => {
3587 hir::ForeignItemKind::Static(
3588 self.lower_ty(t, ImplTraitContext::disallowed()), m)
3590 ForeignItemKind::Ty => hir::ForeignItemKind::Type,
3591 ForeignItemKind::Macro(_) => panic!("shouldn't exist here"),
3593 vis: self.lower_visibility(&i.vis, None),
3598 fn lower_method_sig(
3600 generics: &Generics,
3603 impl_trait_return_allow: bool,
3604 is_async: Option<NodeId>,
3605 ) -> (hir::Generics, hir::MethodSig) {
3606 let header = self.lower_fn_header(sig.header);
3607 let (generics, decl) = self.add_in_band_defs(
3610 AnonymousLifetimeMode::PassThrough,
3611 |this, idty| this.lower_fn_decl(
3613 Some((fn_def_id, idty)),
3614 impl_trait_return_allow,
3618 (generics, hir::MethodSig { header, decl })
3621 fn lower_is_auto(&mut self, a: IsAuto) -> hir::IsAuto {
3623 IsAuto::Yes => hir::IsAuto::Yes,
3624 IsAuto::No => hir::IsAuto::No,
3628 fn lower_fn_header(&mut self, h: FnHeader) -> hir::FnHeader {
3630 unsafety: self.lower_unsafety(h.unsafety),
3631 asyncness: self.lower_asyncness(h.asyncness.node),
3632 constness: self.lower_constness(h.constness),
3637 fn lower_unsafety(&mut self, u: Unsafety) -> hir::Unsafety {
3639 Unsafety::Unsafe => hir::Unsafety::Unsafe,
3640 Unsafety::Normal => hir::Unsafety::Normal,
3644 fn lower_constness(&mut self, c: Spanned<Constness>) -> hir::Constness {
3646 Constness::Const => hir::Constness::Const,
3647 Constness::NotConst => hir::Constness::NotConst,
3651 fn lower_asyncness(&mut self, a: IsAsync) -> hir::IsAsync {
3653 IsAsync::Async { .. } => hir::IsAsync::Async,
3654 IsAsync::NotAsync => hir::IsAsync::NotAsync,
3658 fn lower_unop(&mut self, u: UnOp) -> hir::UnOp {
3660 UnOp::Deref => hir::UnDeref,
3661 UnOp::Not => hir::UnNot,
3662 UnOp::Neg => hir::UnNeg,
3666 fn lower_binop(&mut self, b: BinOp) -> hir::BinOp {
3668 node: match b.node {
3669 BinOpKind::Add => hir::BinOpKind::Add,
3670 BinOpKind::Sub => hir::BinOpKind::Sub,
3671 BinOpKind::Mul => hir::BinOpKind::Mul,
3672 BinOpKind::Div => hir::BinOpKind::Div,
3673 BinOpKind::Rem => hir::BinOpKind::Rem,
3674 BinOpKind::And => hir::BinOpKind::And,
3675 BinOpKind::Or => hir::BinOpKind::Or,
3676 BinOpKind::BitXor => hir::BinOpKind::BitXor,
3677 BinOpKind::BitAnd => hir::BinOpKind::BitAnd,
3678 BinOpKind::BitOr => hir::BinOpKind::BitOr,
3679 BinOpKind::Shl => hir::BinOpKind::Shl,
3680 BinOpKind::Shr => hir::BinOpKind::Shr,
3681 BinOpKind::Eq => hir::BinOpKind::Eq,
3682 BinOpKind::Lt => hir::BinOpKind::Lt,
3683 BinOpKind::Le => hir::BinOpKind::Le,
3684 BinOpKind::Ne => hir::BinOpKind::Ne,
3685 BinOpKind::Ge => hir::BinOpKind::Ge,
3686 BinOpKind::Gt => hir::BinOpKind::Gt,
3692 fn lower_pat(&mut self, p: &Pat) -> P<hir::Pat> {
3693 let node = match p.node {
3694 PatKind::Wild => hir::PatKind::Wild,
3695 PatKind::Ident(ref binding_mode, ident, ref sub) => {
3696 match self.resolver.get_resolution(p.id).map(|d| d.base_def()) {
3697 // `None` can occur in body-less function signatures
3698 def @ None | def @ Some(Def::Local(_)) => {
3699 let canonical_id = match def {
3700 Some(Def::Local(id)) => id,
3703 let hir_id = self.lower_node_id(canonical_id).hir_id;
3704 hir::PatKind::Binding(
3705 self.lower_binding_mode(binding_mode),
3709 sub.as_ref().map(|x| self.lower_pat(x)),
3712 Some(def) => hir::PatKind::Path(hir::QPath::Resolved(
3717 segments: hir_vec![hir::PathSegment::from_ident(ident)],
3722 PatKind::Lit(ref e) => hir::PatKind::Lit(P(self.lower_expr(e))),
3723 PatKind::TupleStruct(ref path, ref pats, ddpos) => {
3724 let qpath = self.lower_qpath(
3728 ParamMode::Optional,
3729 ImplTraitContext::disallowed(),
3731 hir::PatKind::TupleStruct(
3733 pats.iter().map(|x| self.lower_pat(x)).collect(),
3737 PatKind::Path(ref qself, ref path) => {
3738 let qpath = self.lower_qpath(
3742 ParamMode::Optional,
3743 ImplTraitContext::disallowed(),
3745 hir::PatKind::Path(qpath)
3747 PatKind::Struct(ref path, ref fields, etc) => {
3748 let qpath = self.lower_qpath(
3752 ParamMode::Optional,
3753 ImplTraitContext::disallowed(),
3759 let LoweredNodeId { node_id, hir_id } = self.next_id();
3763 node: hir::FieldPat {
3766 ident: f.node.ident,
3767 pat: self.lower_pat(&f.node.pat),
3768 is_shorthand: f.node.is_shorthand,
3773 hir::PatKind::Struct(qpath, fs, etc)
3775 PatKind::Tuple(ref elts, ddpos) => {
3776 hir::PatKind::Tuple(elts.iter().map(|x| self.lower_pat(x)).collect(), ddpos)
3778 PatKind::Box(ref inner) => hir::PatKind::Box(self.lower_pat(inner)),
3779 PatKind::Ref(ref inner, mutbl) => {
3780 hir::PatKind::Ref(self.lower_pat(inner), self.lower_mutability(mutbl))
3782 PatKind::Range(ref e1, ref e2, Spanned { node: ref end, .. }) => hir::PatKind::Range(
3783 P(self.lower_expr(e1)),
3784 P(self.lower_expr(e2)),
3785 self.lower_range_end(end),
3787 PatKind::Slice(ref before, ref slice, ref after) => hir::PatKind::Slice(
3788 before.iter().map(|x| self.lower_pat(x)).collect(),
3789 slice.as_ref().map(|x| self.lower_pat(x)),
3790 after.iter().map(|x| self.lower_pat(x)).collect(),
3792 PatKind::Paren(ref inner) => return self.lower_pat(inner),
3793 PatKind::Mac(_) => panic!("Shouldn't exist here"),
3796 let LoweredNodeId { node_id, hir_id } = self.lower_node_id(p.id);
3805 fn lower_range_end(&mut self, e: &RangeEnd) -> hir::RangeEnd {
3807 RangeEnd::Included(_) => hir::RangeEnd::Included,
3808 RangeEnd::Excluded => hir::RangeEnd::Excluded,
3812 fn lower_anon_const(&mut self, c: &AnonConst) -> hir::AnonConst {
3813 self.with_new_scopes(|this| {
3814 let LoweredNodeId { node_id: _, hir_id } = this.lower_node_id(c.id);
3817 body: this.lower_body(None, |this| this.lower_expr(&c.value)),
3822 fn lower_expr(&mut self, e: &Expr) -> hir::Expr {
3823 let kind = match e.node {
3824 ExprKind::Box(ref inner) => hir::ExprKind::Box(P(self.lower_expr(inner))),
3825 ExprKind::ObsoleteInPlace(..) => {
3826 self.sess.abort_if_errors();
3827 span_bug!(e.span, "encountered ObsoleteInPlace expr during lowering");
3829 ExprKind::Array(ref exprs) => {
3830 hir::ExprKind::Array(exprs.iter().map(|x| self.lower_expr(x)).collect())
3832 ExprKind::Repeat(ref expr, ref count) => {
3833 let expr = P(self.lower_expr(expr));
3834 let count = self.lower_anon_const(count);
3835 hir::ExprKind::Repeat(expr, count)
3837 ExprKind::Tup(ref elts) => {
3838 hir::ExprKind::Tup(elts.iter().map(|x| self.lower_expr(x)).collect())
3840 ExprKind::Call(ref f, ref args) => {
3841 let f = P(self.lower_expr(f));
3842 hir::ExprKind::Call(f, args.iter().map(|x| self.lower_expr(x)).collect())
3844 ExprKind::MethodCall(ref seg, ref args) => {
3845 let hir_seg = P(self.lower_path_segment(
3848 ParamMode::Optional,
3850 ParenthesizedGenericArgs::Err,
3851 ImplTraitContext::disallowed(),
3854 let args = args.iter().map(|x| self.lower_expr(x)).collect();
3855 hir::ExprKind::MethodCall(hir_seg, seg.ident.span, args)
3857 ExprKind::Binary(binop, ref lhs, ref rhs) => {
3858 let binop = self.lower_binop(binop);
3859 let lhs = P(self.lower_expr(lhs));
3860 let rhs = P(self.lower_expr(rhs));
3861 hir::ExprKind::Binary(binop, lhs, rhs)
3863 ExprKind::Unary(op, ref ohs) => {
3864 let op = self.lower_unop(op);
3865 let ohs = P(self.lower_expr(ohs));
3866 hir::ExprKind::Unary(op, ohs)
3868 ExprKind::Lit(ref l) => hir::ExprKind::Lit((*l).clone()),
3869 ExprKind::Cast(ref expr, ref ty) => {
3870 let expr = P(self.lower_expr(expr));
3871 hir::ExprKind::Cast(expr, self.lower_ty(ty, ImplTraitContext::disallowed()))
3873 ExprKind::Type(ref expr, ref ty) => {
3874 let expr = P(self.lower_expr(expr));
3875 hir::ExprKind::Type(expr, self.lower_ty(ty, ImplTraitContext::disallowed()))
3877 ExprKind::AddrOf(m, ref ohs) => {
3878 let m = self.lower_mutability(m);
3879 let ohs = P(self.lower_expr(ohs));
3880 hir::ExprKind::AddrOf(m, ohs)
3882 // More complicated than you might expect because the else branch
3883 // might be `if let`.
3884 ExprKind::If(ref cond, ref blk, ref else_opt) => {
3885 let else_opt = else_opt.as_ref().map(|els| {
3887 ExprKind::IfLet(..) => {
3888 // Wrap the `if let` expr in a block.
3889 let span = els.span;
3890 let els = P(self.lower_expr(els));
3891 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
3892 let blk = P(hir::Block {
3896 rules: hir::DefaultBlock,
3898 targeted_by_break: false,
3900 P(self.expr_block(blk, ThinVec::new()))
3902 _ => P(self.lower_expr(els)),
3906 let then_blk = self.lower_block(blk, false);
3907 let then_expr = self.expr_block(then_blk, ThinVec::new());
3909 hir::ExprKind::If(P(self.lower_expr(cond)), P(then_expr), else_opt)
3911 ExprKind::While(ref cond, ref body, opt_label) => self.with_loop_scope(e.id, |this| {
3912 hir::ExprKind::While(
3913 this.with_loop_condition_scope(|this| P(this.lower_expr(cond))),
3914 this.lower_block(body, false),
3915 this.lower_label(opt_label),
3918 ExprKind::Loop(ref body, opt_label) => self.with_loop_scope(e.id, |this| {
3919 hir::ExprKind::Loop(
3920 this.lower_block(body, false),
3921 this.lower_label(opt_label),
3922 hir::LoopSource::Loop,
3925 ExprKind::TryBlock(ref body) => {
3926 self.with_catch_scope(body.id, |this| {
3927 let unstable_span = this.mark_span_with_reason(
3928 CompilerDesugaringKind::TryBlock,
3931 Symbol::intern("try_trait"),
3934 let mut block = this.lower_block(body, true).into_inner();
3935 let tail = block.expr.take().map_or_else(
3937 let LoweredNodeId { node_id: _, hir_id } = this.next_id();
3938 let span = this.sess.source_map().end_point(unstable_span);
3941 node: hir::ExprKind::Tup(hir_vec![]),
3942 attrs: ThinVec::new(),
3946 |x: P<hir::Expr>| x.into_inner(),
3948 block.expr = Some(this.wrap_in_try_constructor(
3949 "from_ok", tail, unstable_span));
3950 hir::ExprKind::Block(P(block), None)
3953 ExprKind::Match(ref expr, ref arms) => hir::ExprKind::Match(
3954 P(self.lower_expr(expr)),
3955 arms.iter().map(|x| self.lower_arm(x)).collect(),
3956 hir::MatchSource::Normal,
3958 ExprKind::Async(capture_clause, closure_node_id, ref block) => {
3959 self.make_async_expr(capture_clause, closure_node_id, None, |this| {
3960 this.with_new_scopes(|this| {
3961 let block = this.lower_block(block, false);
3962 this.expr_block(block, ThinVec::new())
3967 capture_clause, asyncness, movability, ref decl, ref body, fn_decl_span
3969 if let IsAsync::Async { closure_id, .. } = asyncness {
3970 let outer_decl = FnDecl {
3971 inputs: decl.inputs.clone(),
3972 output: FunctionRetTy::Default(fn_decl_span),
3975 // We need to lower the declaration outside the new scope, because we
3976 // have to conserve the state of being inside a loop condition for the
3977 // closure argument types.
3978 let fn_decl = self.lower_fn_decl(&outer_decl, None, false, None);
3980 self.with_new_scopes(|this| {
3981 // FIXME(cramertj): allow `async` non-`move` closures with arguments.
3982 if capture_clause == CaptureBy::Ref &&
3983 !decl.inputs.is_empty()
3989 "`async` non-`move` closures with arguments \
3990 are not currently supported",
3992 .help("consider using `let` statements to manually capture \
3993 variables by reference before entering an \
3994 `async move` closure")
3998 // Transform `async |x: u8| -> X { ... }` into
3999 // `|x: u8| future_from_generator(|| -> X { ... })`.
4000 let body_id = this.lower_body(Some(&outer_decl), |this| {
4001 let async_ret_ty = if let FunctionRetTy::Ty(ty) = &decl.output {
4004 let async_body = this.make_async_expr(
4005 capture_clause, closure_id, async_ret_ty,
4007 this.with_new_scopes(|this| this.lower_expr(body))
4009 this.expr(fn_decl_span, async_body, ThinVec::new())
4011 hir::ExprKind::Closure(
4012 this.lower_capture_clause(capture_clause),
4020 // Lower outside new scope to preserve `is_in_loop_condition`.
4021 let fn_decl = self.lower_fn_decl(decl, None, false, None);
4023 self.with_new_scopes(|this| {
4024 let mut is_generator = false;
4025 let body_id = this.lower_body(Some(decl), |this| {
4026 let e = this.lower_expr(body);
4027 is_generator = this.is_generator;
4030 let generator_option = if is_generator {
4031 if !decl.inputs.is_empty() {
4036 "generators cannot have explicit arguments"
4038 this.sess.abort_if_errors();
4040 Some(match movability {
4041 Movability::Movable => hir::GeneratorMovability::Movable,
4042 Movability::Static => hir::GeneratorMovability::Static,
4045 if movability == Movability::Static {
4050 "closures cannot be static"
4055 hir::ExprKind::Closure(
4056 this.lower_capture_clause(capture_clause),
4065 ExprKind::Block(ref blk, opt_label) => {
4066 hir::ExprKind::Block(self.lower_block(blk,
4067 opt_label.is_some()),
4068 self.lower_label(opt_label))
4070 ExprKind::Assign(ref el, ref er) => {
4071 hir::ExprKind::Assign(P(self.lower_expr(el)), P(self.lower_expr(er)))
4073 ExprKind::AssignOp(op, ref el, ref er) => hir::ExprKind::AssignOp(
4074 self.lower_binop(op),
4075 P(self.lower_expr(el)),
4076 P(self.lower_expr(er)),
4078 ExprKind::Field(ref el, ident) => hir::ExprKind::Field(P(self.lower_expr(el)), ident),
4079 ExprKind::Index(ref el, ref er) => {
4080 hir::ExprKind::Index(P(self.lower_expr(el)), P(self.lower_expr(er)))
4082 // Desugar `<start>..=<end>` into `std::ops::RangeInclusive::new(<start>, <end>)`.
4083 ExprKind::Range(Some(ref e1), Some(ref e2), RangeLimits::Closed) => {
4084 let id = self.next_id();
4085 let e1 = self.lower_expr(e1);
4086 let e2 = self.lower_expr(e2);
4087 let ty_path = P(self.std_path(e.span, &["ops", "RangeInclusive"], None, false));
4088 let ty = P(self.ty_path(id, e.span, hir::QPath::Resolved(None, ty_path)));
4089 let new_seg = P(hir::PathSegment::from_ident(Ident::from_str("new")));
4090 let new_path = hir::QPath::TypeRelative(ty, new_seg);
4091 let new = P(self.expr(e.span, hir::ExprKind::Path(new_path), ThinVec::new()));
4092 hir::ExprKind::Call(new, hir_vec![e1, e2])
4094 ExprKind::Range(ref e1, ref e2, lims) => {
4095 use syntax::ast::RangeLimits::*;
4097 let path = match (e1, e2, lims) {
4098 (&None, &None, HalfOpen) => "RangeFull",
4099 (&Some(..), &None, HalfOpen) => "RangeFrom",
4100 (&None, &Some(..), HalfOpen) => "RangeTo",
4101 (&Some(..), &Some(..), HalfOpen) => "Range",
4102 (&None, &Some(..), Closed) => "RangeToInclusive",
4103 (&Some(..), &Some(..), Closed) => unreachable!(),
4104 (_, &None, Closed) => self.diagnostic()
4105 .span_fatal(e.span, "inclusive range with no end")
4109 let fields = e1.iter()
4110 .map(|e| ("start", e))
4111 .chain(e2.iter().map(|e| ("end", e)))
4113 let expr = P(self.lower_expr(&e));
4114 let ident = Ident::new(Symbol::intern(s), e.span);
4115 self.field(ident, expr, e.span)
4117 .collect::<P<[hir::Field]>>();
4119 let is_unit = fields.is_empty();
4120 let struct_path = ["ops", path];
4121 let struct_path = self.std_path(e.span, &struct_path, None, is_unit);
4122 let struct_path = hir::QPath::Resolved(None, P(struct_path));
4124 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(e.id);
4129 hir::ExprKind::Path(struct_path)
4131 hir::ExprKind::Struct(P(struct_path), fields, None)
4134 attrs: e.attrs.clone(),
4137 ExprKind::Path(ref qself, ref path) => {
4138 let qpath = self.lower_qpath(
4142 ParamMode::Optional,
4143 ImplTraitContext::disallowed(),
4145 hir::ExprKind::Path(qpath)
4147 ExprKind::Break(opt_label, ref opt_expr) => {
4148 let destination = if self.is_in_loop_condition && opt_label.is_none() {
4151 target_id: Err(hir::LoopIdError::UnlabeledCfInWhileCondition).into(),
4154 self.lower_loop_destination(opt_label.map(|label| (e.id, label)))
4156 hir::ExprKind::Break(
4158 opt_expr.as_ref().map(|x| P(self.lower_expr(x))),
4161 ExprKind::Continue(opt_label) => {
4162 hir::ExprKind::Continue(if self.is_in_loop_condition && opt_label.is_none() {
4165 target_id: Err(hir::LoopIdError::UnlabeledCfInWhileCondition).into(),
4168 self.lower_loop_destination(opt_label.map(|label| (e.id, label)))
4171 ExprKind::Ret(ref e) => hir::ExprKind::Ret(e.as_ref().map(|x| P(self.lower_expr(x)))),
4172 ExprKind::InlineAsm(ref asm) => {
4173 let hir_asm = hir::InlineAsm {
4174 inputs: asm.inputs.iter().map(|&(ref c, _)| c.clone()).collect(),
4175 outputs: asm.outputs
4177 .map(|out| hir::InlineAsmOutput {
4178 constraint: out.constraint.clone(),
4180 is_indirect: out.is_indirect,
4181 span: out.expr.span,
4184 asm: asm.asm.clone(),
4185 asm_str_style: asm.asm_str_style,
4186 clobbers: asm.clobbers.clone().into(),
4187 volatile: asm.volatile,
4188 alignstack: asm.alignstack,
4189 dialect: asm.dialect,
4192 let outputs = asm.outputs
4194 .map(|out| self.lower_expr(&out.expr))
4196 let inputs = asm.inputs
4198 .map(|&(_, ref input)| self.lower_expr(input))
4200 hir::ExprKind::InlineAsm(P(hir_asm), outputs, inputs)
4202 ExprKind::Struct(ref path, ref fields, ref maybe_expr) => hir::ExprKind::Struct(
4207 ParamMode::Optional,
4208 ImplTraitContext::disallowed(),
4210 fields.iter().map(|x| self.lower_field(x)).collect(),
4211 maybe_expr.as_ref().map(|x| P(self.lower_expr(x))),
4213 ExprKind::Paren(ref ex) => {
4214 let mut ex = self.lower_expr(ex);
4215 // Include parens in span, but only if it is a super-span.
4216 if e.span.contains(ex.span) {
4219 // Merge attributes into the inner expression.
4220 let mut attrs = e.attrs.clone();
4221 attrs.extend::<Vec<_>>(ex.attrs.into());
4226 ExprKind::Yield(ref opt_expr) => {
4227 self.is_generator = true;
4230 .map(|x| self.lower_expr(x))
4232 self.expr(e.span, hir::ExprKind::Tup(hir_vec![]), ThinVec::new())
4234 hir::ExprKind::Yield(P(expr))
4237 ExprKind::Err => hir::ExprKind::Err,
4239 // Desugar `ExprIfLet`
4240 // from: `if let <pat> = <sub_expr> <body> [<else_opt>]`
4241 ExprKind::IfLet(ref pats, ref sub_expr, ref body, ref else_opt) => {
4244 // match <sub_expr> {
4246 // _ => [<else_opt> | ()]
4249 let mut arms = vec![];
4251 // `<pat> => <body>`
4253 let body = self.lower_block(body, false);
4254 let body_expr = P(self.expr_block(body, ThinVec::new()));
4255 let pats = pats.iter().map(|pat| self.lower_pat(pat)).collect();
4256 arms.push(self.arm(pats, body_expr));
4259 // _ => [<else_opt>|()]
4261 let wildcard_arm: Option<&Expr> = else_opt.as_ref().map(|p| &**p);
4262 let wildcard_pattern = self.pat_wild(e.span);
4263 let body = if let Some(else_expr) = wildcard_arm {
4264 P(self.lower_expr(else_expr))
4266 self.expr_tuple(e.span, hir_vec![])
4268 arms.push(self.arm(hir_vec![wildcard_pattern], body));
4271 let contains_else_clause = else_opt.is_some();
4273 let sub_expr = P(self.lower_expr(sub_expr));
4275 hir::ExprKind::Match(
4278 hir::MatchSource::IfLetDesugar {
4279 contains_else_clause,
4284 // Desugar `ExprWhileLet`
4285 // from: `[opt_ident]: while let <pat> = <sub_expr> <body>`
4286 ExprKind::WhileLet(ref pats, ref sub_expr, ref body, opt_label) => {
4289 // [opt_ident]: loop {
4290 // match <sub_expr> {
4296 // Note that the block AND the condition are evaluated in the loop scope.
4297 // This is done to allow `break` from inside the condition of the loop.
4298 let (body, break_expr, sub_expr) = self.with_loop_scope(e.id, |this| {
4300 this.lower_block(body, false),
4301 this.expr_break(e.span, ThinVec::new()),
4302 this.with_loop_condition_scope(|this| P(this.lower_expr(sub_expr))),
4306 // `<pat> => <body>`
4308 let body_expr = P(self.expr_block(body, ThinVec::new()));
4309 let pats = pats.iter().map(|pat| self.lower_pat(pat)).collect();
4310 self.arm(pats, body_expr)
4315 let pat_under = self.pat_wild(e.span);
4316 self.arm(hir_vec![pat_under], break_expr)
4319 // `match <sub_expr> { ... }`
4320 let arms = hir_vec![pat_arm, break_arm];
4321 let match_expr = self.expr(
4323 hir::ExprKind::Match(sub_expr, arms, hir::MatchSource::WhileLetDesugar),
4327 // `[opt_ident]: loop { ... }`
4328 let loop_block = P(self.block_expr(P(match_expr)));
4329 let loop_expr = hir::ExprKind::Loop(
4331 self.lower_label(opt_label),
4332 hir::LoopSource::WhileLet,
4334 // Add attributes to the outer returned expr node.
4338 // Desugar `ExprForLoop`
4339 // from: `[opt_ident]: for <pat> in <head> <body>`
4340 ExprKind::ForLoop(ref pat, ref head, ref body, opt_label) => {
4344 // let result = match ::std::iter::IntoIterator::into_iter(<head>) {
4346 // [opt_ident]: loop {
4348 // match ::std::iter::Iterator::next(&mut iter) {
4349 // ::std::option::Option::Some(val) => __next = val,
4350 // ::std::option::Option::None => break
4352 // let <pat> = __next;
4353 // StmtKind::Expr(<body>);
4361 let head = self.lower_expr(head);
4362 let head_sp = head.span;
4363 let desugared_span = self.mark_span_with_reason(
4364 CompilerDesugaringKind::ForLoop,
4369 let iter = self.str_to_ident("iter");
4371 let next_ident = self.str_to_ident("__next");
4372 let next_pat = self.pat_ident_binding_mode(
4375 hir::BindingAnnotation::Mutable,
4378 // `::std::option::Option::Some(val) => next = val`
4380 let val_ident = self.str_to_ident("val");
4381 let val_pat = self.pat_ident(pat.span, val_ident);
4382 let val_expr = P(self.expr_ident(pat.span, val_ident, val_pat.id));
4383 let next_expr = P(self.expr_ident(pat.span, next_ident, next_pat.id));
4384 let assign = P(self.expr(
4386 hir::ExprKind::Assign(next_expr, val_expr),
4389 let some_pat = self.pat_some(pat.span, val_pat);
4390 self.arm(hir_vec![some_pat], assign)
4393 // `::std::option::Option::None => break`
4396 self.with_loop_scope(e.id, |this| this.expr_break(e.span, ThinVec::new()));
4397 let pat = self.pat_none(e.span);
4398 self.arm(hir_vec![pat], break_expr)
4402 let iter_pat = self.pat_ident_binding_mode(
4405 hir::BindingAnnotation::Mutable
4408 // `match ::std::iter::Iterator::next(&mut iter) { ... }`
4410 let iter = P(self.expr_ident(head_sp, iter, iter_pat.id));
4411 let ref_mut_iter = self.expr_mut_addr_of(head_sp, iter);
4412 let next_path = &["iter", "Iterator", "next"];
4413 let next_path = P(self.expr_std_path(head_sp, next_path, None, ThinVec::new()));
4414 let next_expr = P(self.expr_call(head_sp, next_path, hir_vec![ref_mut_iter]));
4415 let arms = hir_vec![pat_arm, break_arm];
4419 hir::ExprKind::Match(
4422 hir::MatchSource::ForLoopDesugar
4427 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
4428 let match_stmt = hir::Stmt {
4430 node: hir::StmtKind::Expr(match_expr),
4434 let next_expr = P(self.expr_ident(head_sp, next_ident, next_pat.id));
4437 let next_let = self.stmt_let_pat(
4441 hir::LocalSource::ForLoopDesugar,
4444 // `let <pat> = __next`
4445 let pat = self.lower_pat(pat);
4446 let pat_let = self.stmt_let_pat(
4450 hir::LocalSource::ForLoopDesugar,
4453 let body_block = self.with_loop_scope(e.id, |this| this.lower_block(body, false));
4454 let body_expr = P(self.expr_block(body_block, ThinVec::new()));
4455 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
4456 let body_stmt = hir::Stmt {
4458 node: hir::StmtKind::Expr(body_expr),
4462 let loop_block = P(self.block_all(
4464 hir_vec![next_let, match_stmt, pat_let, body_stmt],
4468 // `[opt_ident]: loop { ... }`
4469 let loop_expr = hir::ExprKind::Loop(
4471 self.lower_label(opt_label),
4472 hir::LoopSource::ForLoop,
4474 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(e.id);
4475 let loop_expr = P(hir::Expr {
4479 attrs: ThinVec::new(),
4482 // `mut iter => { ... }`
4483 let iter_arm = self.arm(hir_vec![iter_pat], loop_expr);
4485 // `match ::std::iter::IntoIterator::into_iter(<head>) { ... }`
4486 let into_iter_expr = {
4487 let into_iter_path = &["iter", "IntoIterator", "into_iter"];
4488 let into_iter = P(self.expr_std_path(
4489 head_sp, into_iter_path, None, ThinVec::new()));
4490 P(self.expr_call(head_sp, into_iter, hir_vec![head]))
4493 let match_expr = P(self.expr_match(
4497 hir::MatchSource::ForLoopDesugar,
4500 // `{ let _result = ...; _result }`
4501 // Underscore prevents an `unused_variables` lint if the head diverges.
4502 let result_ident = self.str_to_ident("_result");
4503 let (let_stmt, let_stmt_binding) =
4504 self.stmt_let(e.span, false, result_ident, match_expr);
4506 let result = P(self.expr_ident(e.span, result_ident, let_stmt_binding));
4507 let block = P(self.block_all(e.span, hir_vec![let_stmt], Some(result)));
4508 // Add the attributes to the outer returned expr node.
4509 return self.expr_block(block, e.attrs.clone());
4512 // Desugar `ExprKind::Try`
4514 ExprKind::Try(ref sub_expr) => {
4517 // match Try::into_result(<expr>) {
4518 // Ok(val) => #[allow(unreachable_code)] val,
4519 // Err(err) => #[allow(unreachable_code)]
4520 // // If there is an enclosing `catch {...}`
4521 // break 'catch_target Try::from_error(From::from(err)),
4523 // return Try::from_error(From::from(err)),
4526 let unstable_span = self.mark_span_with_reason(
4527 CompilerDesugaringKind::QuestionMark,
4530 Symbol::intern("try_trait")
4534 // `Try::into_result(<expr>)`
4537 let sub_expr = self.lower_expr(sub_expr);
4539 let path = &["ops", "Try", "into_result"];
4540 let path = P(self.expr_std_path(
4541 unstable_span, path, None, ThinVec::new()));
4542 P(self.expr_call(e.span, path, hir_vec![sub_expr]))
4545 // `#[allow(unreachable_code)]`
4547 // `allow(unreachable_code)`
4549 let allow_ident = Ident::from_str("allow").with_span_pos(e.span);
4550 let uc_ident = Ident::from_str("unreachable_code").with_span_pos(e.span);
4551 let uc_nested = attr::mk_nested_word_item(uc_ident);
4552 attr::mk_list_item(e.span, allow_ident, vec![uc_nested])
4554 attr::mk_spanned_attr_outer(e.span, attr::mk_attr_id(), allow)
4556 let attrs = vec![attr];
4558 // `Ok(val) => #[allow(unreachable_code)] val,`
4560 let val_ident = self.str_to_ident("val");
4561 let val_pat = self.pat_ident(e.span, val_ident);
4562 let val_expr = P(self.expr_ident_with_attrs(
4566 ThinVec::from(attrs.clone()),
4568 let ok_pat = self.pat_ok(e.span, val_pat);
4570 self.arm(hir_vec![ok_pat], val_expr)
4573 // `Err(err) => #[allow(unreachable_code)]
4574 // return Try::from_error(From::from(err)),`
4576 let err_ident = self.str_to_ident("err");
4577 let err_local = self.pat_ident(e.span, err_ident);
4579 let path = &["convert", "From", "from"];
4580 let from = P(self.expr_std_path(
4581 e.span, path, None, ThinVec::new()));
4582 let err_expr = self.expr_ident(e.span, err_ident, err_local.id);
4584 self.expr_call(e.span, from, hir_vec![err_expr])
4587 self.wrap_in_try_constructor("from_error", from_expr, unstable_span);
4588 let thin_attrs = ThinVec::from(attrs);
4589 let catch_scope = self.catch_scopes.last().map(|x| *x);
4590 let ret_expr = if let Some(catch_node) = catch_scope {
4593 hir::ExprKind::Break(
4596 target_id: Ok(catch_node),
4598 Some(from_err_expr),
4603 P(self.expr(e.span, hir::ExprKind::Ret(Some(from_err_expr)), thin_attrs))
4606 let err_pat = self.pat_err(e.span, err_local);
4607 self.arm(hir_vec![err_pat], ret_expr)
4610 hir::ExprKind::Match(
4612 hir_vec![err_arm, ok_arm],
4613 hir::MatchSource::TryDesugar,
4617 ExprKind::Mac(_) => panic!("Shouldn't exist here"),
4620 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(e.id);
4626 attrs: e.attrs.clone(),
4630 fn lower_stmt(&mut self, s: &Stmt) -> SmallVec<[hir::Stmt; 1]> {
4631 smallvec![match s.node {
4632 StmtKind::Local(ref l) => {
4633 let (l, item_ids) = self.lower_local(l);
4634 let mut ids: SmallVec<[hir::Stmt; 1]> = item_ids
4637 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
4641 node: hir::StmtKind::Item(item_id),
4647 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(s.id);
4651 node: hir::StmtKind::Local(P(l)),
4657 StmtKind::Item(ref it) => {
4658 // Can only use the ID once.
4659 let mut id = Some(s.id);
4660 return self.lower_item_id(it)
4663 let LoweredNodeId { node_id: _, hir_id } = id.take()
4664 .map(|id| self.lower_node_id(id))
4665 .unwrap_or_else(|| self.next_id());
4669 node: hir::StmtKind::Item(item_id),
4675 StmtKind::Expr(ref e) => {
4676 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(s.id);
4680 node: hir::StmtKind::Expr(P(self.lower_expr(e))),
4684 StmtKind::Semi(ref e) => {
4685 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(s.id);
4689 node: hir::StmtKind::Semi(P(self.lower_expr(e))),
4693 StmtKind::Mac(..) => panic!("Shouldn't exist here"),
4697 fn lower_capture_clause(&mut self, c: CaptureBy) -> hir::CaptureClause {
4699 CaptureBy::Value => hir::CaptureByValue,
4700 CaptureBy::Ref => hir::CaptureByRef,
4704 /// If an `explicit_owner` is given, this method allocates the `HirId` in
4705 /// the address space of that item instead of the item currently being
4706 /// lowered. This can happen during `lower_impl_item_ref()` where we need to
4707 /// lower a `Visibility` value although we haven't lowered the owning
4708 /// `ImplItem` in question yet.
4709 fn lower_visibility(
4712 explicit_owner: Option<NodeId>,
4713 ) -> hir::Visibility {
4714 let node = match v.node {
4715 VisibilityKind::Public => hir::VisibilityKind::Public,
4716 VisibilityKind::Crate(sugar) => hir::VisibilityKind::Crate(sugar),
4717 VisibilityKind::Restricted { ref path, id } => {
4718 debug!("lower_visibility: restricted path id = {:?}", id);
4719 let lowered_id = if let Some(owner) = explicit_owner {
4720 self.lower_node_id_with_owner(id, owner)
4722 self.lower_node_id(id)
4724 let def = self.expect_full_def(id);
4725 hir::VisibilityKind::Restricted {
4726 path: P(self.lower_path_extra(
4729 ParamMode::Explicit,
4732 id: lowered_id.node_id,
4733 hir_id: lowered_id.hir_id,
4736 VisibilityKind::Inherited => hir::VisibilityKind::Inherited,
4738 respan(v.span, node)
4741 fn lower_defaultness(&self, d: Defaultness, has_value: bool) -> hir::Defaultness {
4743 Defaultness::Default => hir::Defaultness::Default {
4744 has_value: has_value,
4746 Defaultness::Final => {
4748 hir::Defaultness::Final
4753 fn lower_block_check_mode(&mut self, b: &BlockCheckMode) -> hir::BlockCheckMode {
4755 BlockCheckMode::Default => hir::DefaultBlock,
4756 BlockCheckMode::Unsafe(u) => hir::UnsafeBlock(self.lower_unsafe_source(u)),
4760 fn lower_binding_mode(&mut self, b: &BindingMode) -> hir::BindingAnnotation {
4762 BindingMode::ByValue(Mutability::Immutable) => hir::BindingAnnotation::Unannotated,
4763 BindingMode::ByRef(Mutability::Immutable) => hir::BindingAnnotation::Ref,
4764 BindingMode::ByValue(Mutability::Mutable) => hir::BindingAnnotation::Mutable,
4765 BindingMode::ByRef(Mutability::Mutable) => hir::BindingAnnotation::RefMut,
4769 fn lower_unsafe_source(&mut self, u: UnsafeSource) -> hir::UnsafeSource {
4771 CompilerGenerated => hir::CompilerGenerated,
4772 UserProvided => hir::UserProvided,
4776 fn lower_impl_polarity(&mut self, i: ImplPolarity) -> hir::ImplPolarity {
4778 ImplPolarity::Positive => hir::ImplPolarity::Positive,
4779 ImplPolarity::Negative => hir::ImplPolarity::Negative,
4783 fn lower_trait_bound_modifier(&mut self, f: TraitBoundModifier) -> hir::TraitBoundModifier {
4785 TraitBoundModifier::None => hir::TraitBoundModifier::None,
4786 TraitBoundModifier::Maybe => hir::TraitBoundModifier::Maybe,
4790 // Helper methods for building HIR.
4792 fn arm(&mut self, pats: hir::HirVec<P<hir::Pat>>, expr: P<hir::Expr>) -> hir::Arm {
4801 fn field(&mut self, ident: Ident, expr: P<hir::Expr>, span: Span) -> hir::Field {
4802 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
4809 is_shorthand: false,
4813 fn expr_break(&mut self, span: Span, attrs: ThinVec<Attribute>) -> P<hir::Expr> {
4814 let expr_break = hir::ExprKind::Break(self.lower_loop_destination(None), None);
4815 P(self.expr(span, expr_break, attrs))
4822 args: hir::HirVec<hir::Expr>,
4824 self.expr(span, hir::ExprKind::Call(e, args), ThinVec::new())
4827 fn expr_ident(&mut self, span: Span, ident: Ident, binding: NodeId) -> hir::Expr {
4828 self.expr_ident_with_attrs(span, ident, binding, ThinVec::new())
4831 fn expr_ident_with_attrs(
4836 attrs: ThinVec<Attribute>,
4838 let expr_path = hir::ExprKind::Path(hir::QPath::Resolved(
4842 def: Def::Local(binding),
4843 segments: hir_vec![hir::PathSegment::from_ident(ident)],
4847 self.expr(span, expr_path, attrs)
4850 fn expr_mut_addr_of(&mut self, span: Span, e: P<hir::Expr>) -> hir::Expr {
4851 self.expr(span, hir::ExprKind::AddrOf(hir::MutMutable, e), ThinVec::new())
4857 components: &[&str],
4858 params: Option<P<hir::GenericArgs>>,
4859 attrs: ThinVec<Attribute>,
4861 let path = self.std_path(span, components, params, true);
4864 hir::ExprKind::Path(hir::QPath::Resolved(None, P(path))),
4873 arms: hir::HirVec<hir::Arm>,
4874 source: hir::MatchSource,
4876 self.expr(span, hir::ExprKind::Match(arg, arms, source), ThinVec::new())
4879 fn expr_block(&mut self, b: P<hir::Block>, attrs: ThinVec<Attribute>) -> hir::Expr {
4880 self.expr(b.span, hir::ExprKind::Block(b, None), attrs)
4883 fn expr_tuple(&mut self, sp: Span, exprs: hir::HirVec<hir::Expr>) -> P<hir::Expr> {
4884 P(self.expr(sp, hir::ExprKind::Tup(exprs), ThinVec::new()))
4887 fn expr(&mut self, span: Span, node: hir::ExprKind, attrs: ThinVec<Attribute>) -> hir::Expr {
4888 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
4900 ex: Option<P<hir::Expr>>,
4902 source: hir::LocalSource,
4904 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
4906 let local = hir::Local {
4912 attrs: ThinVec::new(),
4916 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
4919 node: hir::StmtKind::Local(P(local)),
4930 ) -> (hir::Stmt, NodeId) {
4931 let pat = if mutbl {
4932 self.pat_ident_binding_mode(sp, ident, hir::BindingAnnotation::Mutable)
4934 self.pat_ident(sp, ident)
4936 let pat_id = pat.id;
4938 self.stmt_let_pat(sp, Some(ex), pat, hir::LocalSource::Normal),
4943 fn block_expr(&mut self, expr: P<hir::Expr>) -> hir::Block {
4944 self.block_all(expr.span, hir::HirVec::new(), Some(expr))
4950 stmts: hir::HirVec<hir::Stmt>,
4951 expr: Option<P<hir::Expr>>,
4953 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
4959 rules: hir::DefaultBlock,
4961 targeted_by_break: false,
4965 fn pat_ok(&mut self, span: Span, pat: P<hir::Pat>) -> P<hir::Pat> {
4966 self.pat_std_enum(span, &["result", "Result", "Ok"], hir_vec![pat])
4969 fn pat_err(&mut self, span: Span, pat: P<hir::Pat>) -> P<hir::Pat> {
4970 self.pat_std_enum(span, &["result", "Result", "Err"], hir_vec![pat])
4973 fn pat_some(&mut self, span: Span, pat: P<hir::Pat>) -> P<hir::Pat> {
4974 self.pat_std_enum(span, &["option", "Option", "Some"], hir_vec![pat])
4977 fn pat_none(&mut self, span: Span) -> P<hir::Pat> {
4978 self.pat_std_enum(span, &["option", "Option", "None"], hir_vec![])
4984 components: &[&str],
4985 subpats: hir::HirVec<P<hir::Pat>>,
4987 let path = self.std_path(span, components, None, true);
4988 let qpath = hir::QPath::Resolved(None, P(path));
4989 let pt = if subpats.is_empty() {
4990 hir::PatKind::Path(qpath)
4992 hir::PatKind::TupleStruct(qpath, subpats, None)
4997 fn pat_ident(&mut self, span: Span, ident: Ident) -> P<hir::Pat> {
4998 self.pat_ident_binding_mode(span, ident, hir::BindingAnnotation::Unannotated)
5001 fn pat_ident_binding_mode(
5005 bm: hir::BindingAnnotation,
5007 let LoweredNodeId { node_id, hir_id } = self.next_id();
5012 node: hir::PatKind::Binding(bm, node_id, hir_id, ident.with_span_pos(span), None),
5017 fn pat_wild(&mut self, span: Span) -> P<hir::Pat> {
5018 self.pat(span, hir::PatKind::Wild)
5021 fn pat(&mut self, span: Span, pat: hir::PatKind) -> P<hir::Pat> {
5022 let LoweredNodeId { node_id, hir_id } = self.next_id();
5031 /// Given suffix ["b","c","d"], returns path `::std::b::c::d` when
5032 /// `fld.cx.use_std`, and `::core::b::c::d` otherwise.
5033 /// The path is also resolved according to `is_value`.
5037 components: &[&str],
5038 params: Option<P<hir::GenericArgs>>,
5041 let mut path = self.resolver
5042 .resolve_str_path(span, self.crate_root, components, is_value);
5043 path.segments.last_mut().unwrap().args = params;
5046 for seg in path.segments.iter_mut() {
5047 if let Some(id) = seg.id {
5048 seg.id = Some(self.lower_node_id(id).node_id);
5054 fn ty_path(&mut self, id: LoweredNodeId, span: Span, qpath: hir::QPath) -> hir::Ty {
5056 let node = match qpath {
5057 hir::QPath::Resolved(None, path) => {
5058 // Turn trait object paths into `TyKind::TraitObject` instead.
5060 Def::Trait(_) | Def::TraitAlias(_) => {
5061 let principal = hir::PolyTraitRef {
5062 bound_generic_params: hir::HirVec::new(),
5063 trait_ref: hir::TraitRef {
5064 path: path.and_then(|path| path),
5066 hir_ref_id: id.hir_id,
5071 // The original ID is taken by the `PolyTraitRef`,
5072 // so the `Ty` itself needs a different one.
5073 id = self.next_id();
5074 hir::TyKind::TraitObject(hir_vec![principal], self.elided_dyn_bound(span))
5076 _ => hir::TyKind::Path(hir::QPath::Resolved(None, path)),
5079 _ => hir::TyKind::Path(qpath),
5088 /// Invoked to create the lifetime argument for a type `&T`
5089 /// with no explicit lifetime.
5090 fn elided_ref_lifetime(&mut self, span: Span) -> hir::Lifetime {
5091 match self.anonymous_lifetime_mode {
5092 // Intercept when we are in an impl header and introduce an in-band lifetime.
5093 // Hence `impl Foo for &u32` becomes `impl<'f> Foo for &'f u32` for some fresh
5095 AnonymousLifetimeMode::CreateParameter => {
5096 let fresh_name = self.collect_fresh_in_band_lifetime(span);
5097 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
5101 name: hir::LifetimeName::Param(fresh_name),
5105 AnonymousLifetimeMode::ReportError => self.new_error_lifetime(None, span),
5107 AnonymousLifetimeMode::PassThrough => self.new_implicit_lifetime(span),
5111 /// Report an error on illegal use of `'_` or a `&T` with no explicit lifetime;
5112 /// return a "error lifetime".
5113 fn new_error_lifetime(&mut self, id: Option<NodeId>, span: Span) -> hir::Lifetime {
5114 let (id, msg, label) = match id {
5115 Some(id) => (id, "`'_` cannot be used here", "`'_` is a reserved lifetime name"),
5118 self.next_id().node_id,
5119 "`&` without an explicit lifetime name cannot be used here",
5120 "explicit lifetime name needed here",
5124 let mut err = struct_span_err!(
5131 err.span_label(span, label);
5134 self.new_named_lifetime(id, span, hir::LifetimeName::Error)
5137 /// Invoked to create the lifetime argument(s) for a path like
5138 /// `std::cell::Ref<T>`; note that implicit lifetimes in these
5139 /// sorts of cases are deprecated. This may therefore report a warning or an
5140 /// error, depending on the mode.
5141 fn elided_path_lifetimes(&mut self, span: Span, count: usize) -> P<[hir::Lifetime]> {
5142 match self.anonymous_lifetime_mode {
5143 // N.B., We intentionally ignore the create-parameter mode here
5144 // and instead "pass through" to resolve-lifetimes, which will then
5145 // report an error. This is because we don't want to support
5146 // impl elision for deprecated forms like
5148 // impl Foo for std::cell::Ref<u32> // note lack of '_
5149 AnonymousLifetimeMode::CreateParameter => {}
5151 AnonymousLifetimeMode::ReportError => {
5153 .map(|_| self.new_error_lifetime(None, span))
5157 // This is the normal case.
5158 AnonymousLifetimeMode::PassThrough => {}
5162 .map(|_| self.new_implicit_lifetime(span))
5166 /// Invoked to create the lifetime argument(s) for an elided trait object
5167 /// bound, like the bound in `Box<dyn Debug>`. This method is not invoked
5168 /// when the bound is written, even if it is written with `'_` like in
5169 /// `Box<dyn Debug + '_>`. In those cases, `lower_lifetime` is invoked.
5170 fn elided_dyn_bound(&mut self, span: Span) -> hir::Lifetime {
5171 match self.anonymous_lifetime_mode {
5172 // NB. We intentionally ignore the create-parameter mode here.
5173 // and instead "pass through" to resolve-lifetimes, which will apply
5174 // the object-lifetime-defaulting rules. Elided object lifetime defaults
5175 // do not act like other elided lifetimes. In other words, given this:
5177 // impl Foo for Box<dyn Debug>
5179 // we do not introduce a fresh `'_` to serve as the bound, but instead
5180 // ultimately translate to the equivalent of:
5182 // impl Foo for Box<dyn Debug + 'static>
5184 // `resolve_lifetime` has the code to make that happen.
5185 AnonymousLifetimeMode::CreateParameter => {}
5187 AnonymousLifetimeMode::ReportError => {
5188 // ReportError applies to explicit use of `'_`.
5191 // This is the normal case.
5192 AnonymousLifetimeMode::PassThrough => {}
5195 self.new_implicit_lifetime(span)
5198 fn new_implicit_lifetime(&mut self, span: Span) -> hir::Lifetime {
5199 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
5204 name: hir::LifetimeName::Implicit,
5208 fn maybe_lint_bare_trait(&self, span: Span, id: NodeId, is_global: bool) {
5209 self.sess.buffer_lint_with_diagnostic(
5210 builtin::BARE_TRAIT_OBJECTS,
5213 "trait objects without an explicit `dyn` are deprecated",
5214 builtin::BuiltinLintDiagnostics::BareTraitObject(span, is_global),
5218 fn wrap_in_try_constructor(
5220 method: &'static str,
5222 unstable_span: Span,
5224 let path = &["ops", "Try", method];
5225 let from_err = P(self.expr_std_path(unstable_span, path, None,
5227 P(self.expr_call(e.span, from_err, hir_vec![e]))
5231 fn body_ids(bodies: &BTreeMap<hir::BodyId, hir::Body>) -> Vec<hir::BodyId> {
5232 // Sorting by span ensures that we get things in order within a
5233 // file, and also puts the files in a sensible order.
5234 let mut body_ids: Vec<_> = bodies.keys().cloned().collect();
5235 body_ids.sort_by_key(|b| bodies[b].value.span);