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);
1159 ty: self.lower_ty(&b.ty, itctx),
1164 fn lower_generic_arg(&mut self,
1165 arg: &ast::GenericArg,
1166 itctx: ImplTraitContext<'_>)
1167 -> hir::GenericArg {
1169 ast::GenericArg::Lifetime(lt) => GenericArg::Lifetime(self.lower_lifetime(<)),
1170 ast::GenericArg::Type(ty) => GenericArg::Type(self.lower_ty_direct(&ty, itctx)),
1171 ast::GenericArg::Const(ct) => {
1172 GenericArg::Const(ConstArg {
1173 value: self.lower_anon_const(&ct),
1174 span: ct.value.span,
1180 fn lower_ty(&mut self, t: &Ty, itctx: ImplTraitContext<'_>) -> P<hir::Ty> {
1181 P(self.lower_ty_direct(t, itctx))
1184 fn lower_ty_direct(&mut self, t: &Ty, mut itctx: ImplTraitContext<'_>) -> hir::Ty {
1185 let kind = match t.node {
1186 TyKind::Infer => hir::TyKind::Infer,
1187 TyKind::Err => hir::TyKind::Err,
1188 TyKind::Slice(ref ty) => hir::TyKind::Slice(self.lower_ty(ty, itctx)),
1189 TyKind::Ptr(ref mt) => hir::TyKind::Ptr(self.lower_mt(mt, itctx)),
1190 TyKind::Rptr(ref region, ref mt) => {
1191 let span = self.sess.source_map().next_point(t.span.shrink_to_lo());
1192 let lifetime = match *region {
1193 Some(ref lt) => self.lower_lifetime(lt),
1194 None => self.elided_ref_lifetime(span),
1196 hir::TyKind::Rptr(lifetime, self.lower_mt(mt, itctx))
1198 TyKind::BareFn(ref f) => self.with_in_scope_lifetime_defs(
1201 this.with_anonymous_lifetime_mode(
1202 AnonymousLifetimeMode::PassThrough,
1204 hir::TyKind::BareFn(P(hir::BareFnTy {
1205 generic_params: this.lower_generic_params(
1207 &NodeMap::default(),
1208 ImplTraitContext::disallowed(),
1210 unsafety: this.lower_unsafety(f.unsafety),
1212 decl: this.lower_fn_decl(&f.decl, None, false, None),
1213 arg_names: this.lower_fn_args_to_names(&f.decl),
1219 TyKind::Never => hir::TyKind::Never,
1220 TyKind::Tup(ref tys) => {
1221 hir::TyKind::Tup(tys.iter().map(|ty| {
1222 self.lower_ty_direct(ty, itctx.reborrow())
1225 TyKind::Paren(ref ty) => {
1226 return self.lower_ty_direct(ty, itctx);
1228 TyKind::Path(ref qself, ref path) => {
1229 let id = self.lower_node_id(t.id);
1230 let qpath = self.lower_qpath(t.id, qself, path, ParamMode::Explicit, itctx);
1231 let ty = self.ty_path(id, t.span, qpath);
1232 if let hir::TyKind::TraitObject(..) = ty.node {
1233 self.maybe_lint_bare_trait(t.span, t.id, qself.is_none() && path.is_global());
1237 TyKind::ImplicitSelf => hir::TyKind::Path(hir::QPath::Resolved(
1240 def: self.expect_full_def(t.id),
1241 segments: hir_vec![hir::PathSegment::from_ident(keywords::SelfUpper.ident())],
1245 TyKind::Array(ref ty, ref length) => {
1246 hir::TyKind::Array(self.lower_ty(ty, itctx), self.lower_anon_const(length))
1248 TyKind::Typeof(ref expr) => {
1249 hir::TyKind::Typeof(self.lower_anon_const(expr))
1251 TyKind::TraitObject(ref bounds, kind) => {
1252 let mut lifetime_bound = None;
1255 .filter_map(|bound| match *bound {
1256 GenericBound::Trait(ref ty, TraitBoundModifier::None) => {
1257 Some(self.lower_poly_trait_ref(ty, itctx.reborrow()))
1259 GenericBound::Trait(_, TraitBoundModifier::Maybe) => None,
1260 GenericBound::Outlives(ref lifetime) => {
1261 if lifetime_bound.is_none() {
1262 lifetime_bound = Some(self.lower_lifetime(lifetime));
1268 let lifetime_bound =
1269 lifetime_bound.unwrap_or_else(|| self.elided_dyn_bound(t.span));
1270 if kind != TraitObjectSyntax::Dyn {
1271 self.maybe_lint_bare_trait(t.span, t.id, false);
1273 hir::TyKind::TraitObject(bounds, lifetime_bound)
1275 TyKind::ImplTrait(def_node_id, ref bounds) => {
1278 ImplTraitContext::Existential(fn_def_id) => {
1279 self.lower_existential_impl_trait(
1280 span, fn_def_id, def_node_id,
1281 |this| this.lower_param_bounds(bounds, itctx),
1284 ImplTraitContext::Universal(in_band_ty_params) => {
1285 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(def_node_id);
1286 // Add a definition for the in-band `Param`.
1287 let def_index = self
1290 .opt_def_index(def_node_id)
1293 let hir_bounds = self.lower_param_bounds(
1295 ImplTraitContext::Universal(in_band_ty_params),
1297 // Set the name to `impl Bound1 + Bound2`.
1298 let ident = Ident::from_str(&pprust::ty_to_string(t)).with_span_pos(span);
1299 in_band_ty_params.push(hir::GenericParam {
1301 name: ParamName::Plain(ident),
1302 pure_wrt_drop: false,
1306 kind: hir::GenericParamKind::Type {
1308 synthetic: Some(hir::SyntheticTyParamKind::ImplTrait),
1312 hir::TyKind::Path(hir::QPath::Resolved(
1316 def: Def::TyParam(DefId::local(def_index)),
1317 segments: hir_vec![hir::PathSegment::from_ident(ident)],
1321 ImplTraitContext::Disallowed(pos) => {
1322 let allowed_in = if self.sess.features_untracked()
1323 .impl_trait_in_bindings {
1324 "bindings or function and inherent method return types"
1326 "function and inherent method return types"
1328 let mut err = struct_span_err!(
1332 "`impl Trait` not allowed outside of {}",
1335 if pos == ImplTraitPosition::Binding &&
1336 nightly_options::is_nightly_build() {
1338 "add #![feature(impl_trait_in_bindings)] to the crate attributes \
1346 TyKind::Mac(_) => panic!("TyMac should have been expanded by now."),
1347 TyKind::CVarArgs => {
1348 // Create the implicit lifetime of the "spoofed" `VaList`.
1349 let span = self.sess.source_map().next_point(t.span.shrink_to_lo());
1350 let lt = self.new_implicit_lifetime(span);
1351 hir::TyKind::CVarArgs(lt)
1355 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(t.id);
1363 fn lower_existential_impl_trait(
1366 fn_def_id: Option<DefId>,
1367 exist_ty_node_id: NodeId,
1368 lower_bounds: impl FnOnce(&mut LoweringContext<'_>) -> hir::GenericBounds,
1370 // Make sure we know that some funky desugaring has been going on here.
1371 // This is a first: there is code in other places like for loop
1372 // desugaring that explicitly states that we don't want to track that.
1373 // Not tracking it makes lints in rustc and clippy very fragile as
1374 // frequently opened issues show.
1375 let exist_ty_span = self.mark_span_with_reason(
1376 CompilerDesugaringKind::ExistentialReturnType,
1381 let exist_ty_def_index = self
1384 .opt_def_index(exist_ty_node_id)
1387 self.allocate_hir_id_counter(exist_ty_node_id, &"existential impl trait");
1389 let hir_bounds = self.with_hir_id_owner(exist_ty_node_id, lower_bounds);
1391 let (lifetimes, lifetime_defs) = self.lifetimes_from_impl_trait_bounds(
1397 self.with_hir_id_owner(exist_ty_node_id, |lctx| {
1398 let LoweredNodeId { node_id: _, hir_id } = lctx.next_id();
1399 let exist_ty_item_kind = hir::ItemKind::Existential(hir::ExistTy {
1400 generics: hir::Generics {
1401 params: lifetime_defs,
1402 where_clause: hir::WhereClause {
1404 predicates: Vec::new().into(),
1409 impl_trait_fn: fn_def_id,
1411 let exist_ty_id = lctx.lower_node_id(exist_ty_node_id);
1412 // Generate an `existential type Foo: Trait;` declaration.
1413 trace!("creating existential type with id {:#?}", exist_ty_id);
1415 trace!("exist ty def index: {:#?}", exist_ty_def_index);
1416 let exist_ty_item = hir::Item {
1417 id: exist_ty_id.node_id,
1418 hir_id: exist_ty_id.hir_id,
1419 ident: keywords::Invalid.ident(),
1420 attrs: Default::default(),
1421 node: exist_ty_item_kind,
1422 vis: respan(span.shrink_to_lo(), hir::VisibilityKind::Inherited),
1423 span: exist_ty_span,
1426 // Insert the item into the global list. This usually happens
1427 // automatically for all AST items. But this existential type item
1428 // does not actually exist in the AST.
1429 lctx.insert_item(exist_ty_id.node_id, exist_ty_item);
1431 // `impl Trait` now just becomes `Foo<'a, 'b, ..>`.
1432 hir::TyKind::Def(hir::ItemId { id: exist_ty_id.node_id }, lifetimes)
1436 fn lifetimes_from_impl_trait_bounds(
1438 exist_ty_id: NodeId,
1439 parent_index: DefIndex,
1440 bounds: &hir::GenericBounds,
1441 ) -> (HirVec<hir::GenericArg>, HirVec<hir::GenericParam>) {
1442 // This visitor walks over impl trait bounds and creates defs for all lifetimes which
1443 // appear in the bounds, excluding lifetimes that are created within the bounds.
1444 // E.g., `'a`, `'b`, but not `'c` in `impl for<'c> SomeTrait<'a, 'b, 'c>`.
1445 struct ImplTraitLifetimeCollector<'r, 'a: 'r> {
1446 context: &'r mut LoweringContext<'a>,
1448 exist_ty_id: NodeId,
1449 collect_elided_lifetimes: bool,
1450 currently_bound_lifetimes: Vec<hir::LifetimeName>,
1451 already_defined_lifetimes: FxHashSet<hir::LifetimeName>,
1452 output_lifetimes: Vec<hir::GenericArg>,
1453 output_lifetime_params: Vec<hir::GenericParam>,
1456 impl<'r, 'a: 'r, 'v> hir::intravisit::Visitor<'v> for ImplTraitLifetimeCollector<'r, 'a> {
1457 fn nested_visit_map<'this>(
1459 ) -> hir::intravisit::NestedVisitorMap<'this, 'v> {
1460 hir::intravisit::NestedVisitorMap::None
1463 fn visit_generic_args(&mut self, span: Span, parameters: &'v hir::GenericArgs) {
1464 // Don't collect elided lifetimes used inside of `Fn()` syntax.
1465 if parameters.parenthesized {
1466 let old_collect_elided_lifetimes = self.collect_elided_lifetimes;
1467 self.collect_elided_lifetimes = false;
1468 hir::intravisit::walk_generic_args(self, span, parameters);
1469 self.collect_elided_lifetimes = old_collect_elided_lifetimes;
1471 hir::intravisit::walk_generic_args(self, span, parameters);
1475 fn visit_ty(&mut self, t: &'v hir::Ty) {
1476 // Don't collect elided lifetimes used inside of `fn()` syntax.
1477 if let hir::TyKind::BareFn(_) = t.node {
1478 let old_collect_elided_lifetimes = self.collect_elided_lifetimes;
1479 self.collect_elided_lifetimes = false;
1481 // Record the "stack height" of `for<'a>` lifetime bindings
1482 // to be able to later fully undo their introduction.
1483 let old_len = self.currently_bound_lifetimes.len();
1484 hir::intravisit::walk_ty(self, t);
1485 self.currently_bound_lifetimes.truncate(old_len);
1487 self.collect_elided_lifetimes = old_collect_elided_lifetimes;
1489 hir::intravisit::walk_ty(self, t)
1493 fn visit_poly_trait_ref(
1495 trait_ref: &'v hir::PolyTraitRef,
1496 modifier: hir::TraitBoundModifier,
1498 // Record the "stack height" of `for<'a>` lifetime bindings
1499 // to be able to later fully undo their introduction.
1500 let old_len = self.currently_bound_lifetimes.len();
1501 hir::intravisit::walk_poly_trait_ref(self, trait_ref, modifier);
1502 self.currently_bound_lifetimes.truncate(old_len);
1505 fn visit_generic_param(&mut self, param: &'v hir::GenericParam) {
1506 // Record the introduction of 'a in `for<'a> ...`.
1507 if let hir::GenericParamKind::Lifetime { .. } = param.kind {
1508 // Introduce lifetimes one at a time so that we can handle
1509 // cases like `fn foo<'d>() -> impl for<'a, 'b: 'a, 'c: 'b + 'd>`.
1510 let lt_name = hir::LifetimeName::Param(param.name);
1511 self.currently_bound_lifetimes.push(lt_name);
1514 hir::intravisit::walk_generic_param(self, param);
1517 fn visit_lifetime(&mut self, lifetime: &'v hir::Lifetime) {
1518 let name = match lifetime.name {
1519 hir::LifetimeName::Implicit | hir::LifetimeName::Underscore => {
1520 if self.collect_elided_lifetimes {
1521 // Use `'_` for both implicit and underscore lifetimes in
1522 // `abstract type Foo<'_>: SomeTrait<'_>;`.
1523 hir::LifetimeName::Underscore
1528 hir::LifetimeName::Param(_) => lifetime.name,
1529 hir::LifetimeName::Error | hir::LifetimeName::Static => return,
1532 if !self.currently_bound_lifetimes.contains(&name)
1533 && !self.already_defined_lifetimes.contains(&name) {
1534 self.already_defined_lifetimes.insert(name);
1536 let LoweredNodeId { node_id: _, hir_id } = self.context.next_id();
1537 self.output_lifetimes.push(hir::GenericArg::Lifetime(hir::Lifetime {
1539 span: lifetime.span,
1543 // We need to manually create the ids here, because the
1544 // definitions will go into the explicit `existential type`
1545 // declaration and thus need to have their owner set to that item
1546 let def_node_id = self.context.sess.next_node_id();
1547 let LoweredNodeId { node_id: _, hir_id } =
1548 self.context.lower_node_id_with_owner(def_node_id, self.exist_ty_id);
1549 self.context.resolver.definitions().create_def_with_parent(
1552 DefPathData::LifetimeParam(name.ident().as_interned_str()),
1553 DefIndexAddressSpace::High,
1558 let (name, kind) = match name {
1559 hir::LifetimeName::Underscore => (
1560 hir::ParamName::Plain(keywords::UnderscoreLifetime.ident()),
1561 hir::LifetimeParamKind::Elided,
1563 hir::LifetimeName::Param(param_name) => (
1565 hir::LifetimeParamKind::Explicit,
1567 _ => bug!("expected LifetimeName::Param or ParamName::Plain"),
1570 self.output_lifetime_params.push(hir::GenericParam {
1573 span: lifetime.span,
1574 pure_wrt_drop: false,
1577 kind: hir::GenericParamKind::Lifetime { kind }
1583 let mut lifetime_collector = ImplTraitLifetimeCollector {
1585 parent: parent_index,
1587 collect_elided_lifetimes: true,
1588 currently_bound_lifetimes: Vec::new(),
1589 already_defined_lifetimes: FxHashSet::default(),
1590 output_lifetimes: Vec::new(),
1591 output_lifetime_params: Vec::new(),
1594 for bound in bounds {
1595 hir::intravisit::walk_param_bound(&mut lifetime_collector, &bound);
1599 lifetime_collector.output_lifetimes.into(),
1600 lifetime_collector.output_lifetime_params.into(),
1604 fn lower_foreign_mod(&mut self, fm: &ForeignMod) -> hir::ForeignMod {
1609 .map(|x| self.lower_foreign_item(x))
1614 fn lower_global_asm(&mut self, ga: &GlobalAsm) -> P<hir::GlobalAsm> {
1621 fn lower_variant(&mut self, v: &Variant) -> hir::Variant {
1623 node: hir::VariantKind {
1624 ident: v.node.ident,
1625 attrs: self.lower_attrs(&v.node.attrs),
1626 data: self.lower_variant_data(&v.node.data),
1627 disr_expr: v.node.disr_expr.as_ref().map(|e| self.lower_anon_const(e)),
1636 qself: &Option<QSelf>,
1638 param_mode: ParamMode,
1639 mut itctx: ImplTraitContext<'_>,
1641 let qself_position = qself.as_ref().map(|q| q.position);
1642 let qself = qself.as_ref().map(|q| self.lower_ty(&q.ty, itctx.reborrow()));
1644 let resolution = self.resolver
1646 .unwrap_or_else(|| PathResolution::new(Def::Err));
1648 let proj_start = p.segments.len() - resolution.unresolved_segments();
1649 let path = P(hir::Path {
1650 def: resolution.base_def(),
1651 segments: p.segments[..proj_start]
1654 .map(|(i, segment)| {
1655 let param_mode = match (qself_position, param_mode) {
1656 (Some(j), ParamMode::Optional) if i < j => {
1657 // This segment is part of the trait path in a
1658 // qualified path - one of `a`, `b` or `Trait`
1659 // in `<X as a::b::Trait>::T::U::method`.
1665 // Figure out if this is a type/trait segment,
1666 // which may need lifetime elision performed.
1667 let parent_def_id = |this: &mut Self, def_id: DefId| DefId {
1668 krate: def_id.krate,
1669 index: this.def_key(def_id).parent.expect("missing parent"),
1671 let type_def_id = match resolution.base_def() {
1672 Def::AssociatedTy(def_id) if i + 2 == proj_start => {
1673 Some(parent_def_id(self, def_id))
1675 Def::Variant(def_id) if i + 1 == proj_start => {
1676 Some(parent_def_id(self, def_id))
1679 | Def::Union(def_id)
1681 | Def::TyAlias(def_id)
1682 | Def::Trait(def_id) if i + 1 == proj_start =>
1688 let parenthesized_generic_args = match resolution.base_def() {
1689 // `a::b::Trait(Args)`
1690 Def::Trait(..) if i + 1 == proj_start => ParenthesizedGenericArgs::Ok,
1691 // `a::b::Trait(Args)::TraitItem`
1692 Def::Method(..) | Def::AssociatedConst(..) | Def::AssociatedTy(..)
1693 if i + 2 == proj_start =>
1695 ParenthesizedGenericArgs::Ok
1697 // Avoid duplicated errors.
1698 Def::Err => ParenthesizedGenericArgs::Ok,
1704 | Def::Variant(..) if i + 1 == proj_start =>
1706 ParenthesizedGenericArgs::Err
1708 // A warning for now, for compatibility reasons
1709 _ => ParenthesizedGenericArgs::Warn,
1712 let num_lifetimes = type_def_id.map_or(0, |def_id| {
1713 if let Some(&n) = self.type_def_lifetime_params.get(&def_id) {
1716 assert!(!def_id.is_local());
1718 self.cstore.item_generics_cloned_untracked(def_id, self.sess);
1719 let n = item_generics.own_counts().lifetimes;
1720 self.type_def_lifetime_params.insert(def_id, n);
1723 self.lower_path_segment(
1728 parenthesized_generic_args,
1737 // Simple case, either no projections, or only fully-qualified.
1738 // E.g., `std::mem::size_of` or `<I as Iterator>::Item`.
1739 if resolution.unresolved_segments() == 0 {
1740 return hir::QPath::Resolved(qself, path);
1743 // Create the innermost type that we're projecting from.
1744 let mut ty = if path.segments.is_empty() {
1745 // If the base path is empty that means there exists a
1746 // syntactical `Self`, e.g., `&i32` in `<&i32>::clone`.
1747 qself.expect("missing QSelf for <T>::...")
1749 // Otherwise, the base path is an implicit `Self` type path,
1750 // e.g., `Vec` in `Vec::new` or `<I as Iterator>::Item` in
1751 // `<I as Iterator>::Item::default`.
1752 let new_id = self.next_id();
1753 P(self.ty_path(new_id, p.span, hir::QPath::Resolved(qself, path)))
1756 // Anything after the base path are associated "extensions",
1757 // out of which all but the last one are associated types,
1758 // e.g., for `std::vec::Vec::<T>::IntoIter::Item::clone`:
1759 // * base path is `std::vec::Vec<T>`
1760 // * "extensions" are `IntoIter`, `Item` and `clone`
1761 // * type nodes are:
1762 // 1. `std::vec::Vec<T>` (created above)
1763 // 2. `<std::vec::Vec<T>>::IntoIter`
1764 // 3. `<<std::vec::Vec<T>>::IntoIter>::Item`
1765 // * final path is `<<<std::vec::Vec<T>>::IntoIter>::Item>::clone`
1766 for (i, segment) in p.segments.iter().enumerate().skip(proj_start) {
1767 let segment = P(self.lower_path_segment(
1772 ParenthesizedGenericArgs::Warn,
1776 let qpath = hir::QPath::TypeRelative(ty, segment);
1778 // It's finished, return the extension of the right node type.
1779 if i == p.segments.len() - 1 {
1783 // Wrap the associated extension in another type node.
1784 let new_id = self.next_id();
1785 ty = P(self.ty_path(new_id, p.span, qpath));
1788 // We should've returned in the for loop above.
1791 "lower_qpath: no final extension segment in {}..{}",
1797 fn lower_path_extra(
1801 param_mode: ParamMode,
1802 explicit_owner: Option<NodeId>,
1806 segments: p.segments
1809 self.lower_path_segment(
1814 ParenthesizedGenericArgs::Err,
1815 ImplTraitContext::disallowed(),
1824 fn lower_path(&mut self, id: NodeId, p: &Path, param_mode: ParamMode) -> hir::Path {
1825 let def = self.expect_full_def(id);
1826 self.lower_path_extra(def, p, param_mode, None)
1829 fn lower_path_segment(
1832 segment: &PathSegment,
1833 param_mode: ParamMode,
1834 expected_lifetimes: usize,
1835 parenthesized_generic_args: ParenthesizedGenericArgs,
1836 itctx: ImplTraitContext<'_>,
1837 explicit_owner: Option<NodeId>,
1838 ) -> hir::PathSegment {
1839 let (mut generic_args, infer_types) = if let Some(ref generic_args) = segment.args {
1840 let msg = "parenthesized type parameters may only be used with a `Fn` trait";
1841 match **generic_args {
1842 GenericArgs::AngleBracketed(ref data) => {
1843 self.lower_angle_bracketed_parameter_data(data, param_mode, itctx)
1845 GenericArgs::Parenthesized(ref data) => match parenthesized_generic_args {
1846 ParenthesizedGenericArgs::Ok => self.lower_parenthesized_parameter_data(data),
1847 ParenthesizedGenericArgs::Warn => {
1848 self.sess.buffer_lint(
1849 PARENTHESIZED_PARAMS_IN_TYPES_AND_MODULES,
1854 (hir::GenericArgs::none(), true)
1856 ParenthesizedGenericArgs::Err => {
1857 let mut err = struct_span_err!(self.sess, data.span, E0214, "{}", msg);
1858 err.span_label(data.span, "only `Fn` traits may use parentheses");
1859 if let Ok(snippet) = self.sess.source_map().span_to_snippet(data.span) {
1860 // Do not suggest going from `Trait()` to `Trait<>`
1861 if data.inputs.len() > 0 {
1862 err.span_suggestion(
1864 "use angle brackets instead",
1865 format!("<{}>", &snippet[1..snippet.len() - 1]),
1866 Applicability::MaybeIncorrect,
1871 (self.lower_angle_bracketed_parameter_data(
1872 &data.as_angle_bracketed_args(),
1880 self.lower_angle_bracketed_parameter_data(&Default::default(), param_mode, itctx)
1883 let has_lifetimes = generic_args.args.iter().any(|arg| match arg {
1884 GenericArg::Lifetime(_) => true,
1887 let first_generic_span = generic_args.args.iter().map(|a| a.span())
1888 .chain(generic_args.bindings.iter().map(|b| b.span)).next();
1889 if !generic_args.parenthesized && !has_lifetimes {
1891 self.elided_path_lifetimes(path_span, expected_lifetimes)
1893 .map(|lt| GenericArg::Lifetime(lt))
1894 .chain(generic_args.args.into_iter())
1896 if expected_lifetimes > 0 && param_mode == ParamMode::Explicit {
1897 let anon_lt_suggestion = vec!["'_"; expected_lifetimes].join(", ");
1898 let no_ty_args = generic_args.args.len() == expected_lifetimes;
1899 let no_bindings = generic_args.bindings.is_empty();
1900 let (incl_angl_brckt, insertion_span, suggestion) = if no_ty_args && no_bindings {
1901 // If there are no (non-implicit) generic args or associated-type
1902 // bindings, our suggestion includes the angle brackets.
1903 (true, path_span.shrink_to_hi(), format!("<{}>", anon_lt_suggestion))
1905 // Otherwise—sorry, this is kind of gross—we need to infer the
1906 // place to splice in the `'_, ` from the generics that do exist.
1907 let first_generic_span = first_generic_span
1908 .expect("already checked that type args or bindings exist");
1909 (false, first_generic_span.shrink_to_lo(), format!("{}, ", anon_lt_suggestion))
1911 self.sess.buffer_lint_with_diagnostic(
1912 ELIDED_LIFETIMES_IN_PATHS,
1915 "hidden lifetime parameters in types are deprecated",
1916 builtin::BuiltinLintDiagnostics::ElidedLifetimesInPaths(
1917 expected_lifetimes, path_span, incl_angl_brckt, insertion_span, suggestion
1923 let def = self.expect_full_def(segment.id);
1924 let id = if let Some(owner) = explicit_owner {
1925 self.lower_node_id_with_owner(segment.id, owner)
1927 self.lower_node_id(segment.id)
1930 "lower_path_segment: ident={:?} original-id={:?} new-id={:?}",
1931 segment.ident, segment.id, id,
1934 hir::PathSegment::new(
1944 fn lower_angle_bracketed_parameter_data(
1946 data: &AngleBracketedArgs,
1947 param_mode: ParamMode,
1948 mut itctx: ImplTraitContext<'_>,
1949 ) -> (hir::GenericArgs, bool) {
1950 let &AngleBracketedArgs { ref args, ref bindings, .. } = data;
1951 let has_types = args.iter().any(|arg| match arg {
1952 ast::GenericArg::Type(_) => true,
1956 args: args.iter().map(|a| self.lower_generic_arg(a, itctx.reborrow())).collect(),
1957 bindings: bindings.iter().map(|b| self.lower_ty_binding(b, itctx.reborrow())).collect(),
1958 parenthesized: false,
1960 !has_types && param_mode == ParamMode::Optional)
1963 fn lower_parenthesized_parameter_data(
1965 data: &ParenthesizedArgs,
1966 ) -> (hir::GenericArgs, bool) {
1967 // Switch to `PassThrough` mode for anonymous lifetimes: this
1968 // means that we permit things like `&Ref<T>`, where `Ref` has
1969 // a hidden lifetime parameter. This is needed for backwards
1970 // compatibility, even in contexts like an impl header where
1971 // we generally don't permit such things (see #51008).
1972 self.with_anonymous_lifetime_mode(
1973 AnonymousLifetimeMode::PassThrough,
1975 let &ParenthesizedArgs { ref inputs, ref output, span } = data;
1978 .map(|ty| this.lower_ty_direct(ty, ImplTraitContext::disallowed()))
1980 let mk_tup = |this: &mut Self, tys, span| {
1981 let LoweredNodeId { node_id: _, hir_id } = this.next_id();
1982 hir::Ty { node: hir::TyKind::Tup(tys), hir_id, span }
1984 let LoweredNodeId { node_id: _, hir_id } = this.next_id();
1988 args: hir_vec![GenericArg::Type(mk_tup(this, inputs, span))],
1992 ident: Ident::from_str(FN_OUTPUT_NAME),
1995 .map(|ty| this.lower_ty(&ty, ImplTraitContext::disallowed()))
1996 .unwrap_or_else(|| P(mk_tup(this, hir::HirVec::new(), span))),
1997 span: output.as_ref().map_or(span, |ty| ty.span),
2000 parenthesized: true,
2008 fn lower_local(&mut self, l: &Local) -> (hir::Local, SmallVec<[hir::ItemId; 1]>) {
2009 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(l.id);
2010 let mut ids = SmallVec::<[hir::ItemId; 1]>::new();
2011 if self.sess.features_untracked().impl_trait_in_bindings {
2012 if let Some(ref ty) = l.ty {
2013 let mut visitor = ImplTraitTypeIdVisitor { ids: &mut ids };
2014 visitor.visit_ty(ty);
2017 let parent_def_id = DefId::local(self.current_hir_id_owner.last().unwrap().0);
2022 .map(|t| self.lower_ty(t,
2023 if self.sess.features_untracked().impl_trait_in_bindings {
2024 ImplTraitContext::Existential(Some(parent_def_id))
2026 ImplTraitContext::Disallowed(ImplTraitPosition::Binding)
2029 pat: self.lower_pat(&l.pat),
2030 init: l.init.as_ref().map(|e| P(self.lower_expr(e))),
2032 attrs: l.attrs.clone(),
2033 source: hir::LocalSource::Normal,
2037 fn lower_mutability(&mut self, m: Mutability) -> hir::Mutability {
2039 Mutability::Mutable => hir::MutMutable,
2040 Mutability::Immutable => hir::MutImmutable,
2044 fn lower_arg(&mut self, arg: &Arg) -> hir::Arg {
2045 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(arg.id);
2048 pat: self.lower_pat(&arg.pat),
2052 fn lower_fn_args_to_names(&mut self, decl: &FnDecl) -> hir::HirVec<Ident> {
2055 .map(|arg| match arg.pat.node {
2056 PatKind::Ident(_, ident, _) => ident,
2057 _ => Ident::new(keywords::Invalid.name(), arg.pat.span),
2062 // Lowers a function declaration.
2064 // decl: the unlowered (ast) function declaration.
2065 // fn_def_id: if `Some`, impl Trait arguments are lowered into generic parameters on the
2066 // given DefId, otherwise impl Trait is disallowed. Must be `Some` if
2067 // make_ret_async is also `Some`.
2068 // impl_trait_return_allow: determines whether impl Trait can be used in return position.
2069 // This guards against trait declarations and implementations where impl Trait is
2071 // make_ret_async: if `Some`, converts `-> T` into `-> impl Future<Output = T>` in the
2072 // return type. This is used for `async fn` declarations. The `NodeId` is the id of the
2073 // return type impl Trait item.
2077 mut in_band_ty_params: Option<(DefId, &mut Vec<hir::GenericParam>)>,
2078 impl_trait_return_allow: bool,
2079 make_ret_async: Option<NodeId>,
2080 ) -> P<hir::FnDecl> {
2081 let inputs = decl.inputs
2084 if let Some((_, ref mut ibty)) = in_band_ty_params {
2085 self.lower_ty_direct(&arg.ty, ImplTraitContext::Universal(ibty))
2087 self.lower_ty_direct(&arg.ty, ImplTraitContext::disallowed())
2090 .collect::<HirVec<_>>();
2092 let output = if let Some(ret_id) = make_ret_async {
2093 self.lower_async_fn_ret_ty(
2096 in_band_ty_params.expect("make_ret_async but no fn_def_id").0,
2101 FunctionRetTy::Ty(ref ty) => match in_band_ty_params {
2102 Some((def_id, _)) if impl_trait_return_allow => {
2103 hir::Return(self.lower_ty(ty,
2104 ImplTraitContext::Existential(Some(def_id))))
2107 hir::Return(self.lower_ty(ty, ImplTraitContext::disallowed()))
2110 FunctionRetTy::Default(span) => hir::DefaultReturn(span),
2117 c_variadic: decl.c_variadic,
2118 implicit_self: decl.inputs.get(0).map_or(
2119 hir::ImplicitSelfKind::None,
2121 let is_mutable_pat = match arg.pat.node {
2122 PatKind::Ident(BindingMode::ByValue(mt), _, _) |
2123 PatKind::Ident(BindingMode::ByRef(mt), _, _) =>
2124 mt == Mutability::Mutable,
2129 TyKind::ImplicitSelf if is_mutable_pat => hir::ImplicitSelfKind::Mut,
2130 TyKind::ImplicitSelf => hir::ImplicitSelfKind::Imm,
2131 // Given we are only considering `ImplicitSelf` types, we needn't consider
2132 // the case where we have a mutable pattern to a reference as that would
2133 // no longer be an `ImplicitSelf`.
2134 TyKind::Rptr(_, ref mt) if mt.ty.node.is_implicit_self() &&
2135 mt.mutbl == ast::Mutability::Mutable =>
2136 hir::ImplicitSelfKind::MutRef,
2137 TyKind::Rptr(_, ref mt) if mt.ty.node.is_implicit_self() =>
2138 hir::ImplicitSelfKind::ImmRef,
2139 _ => hir::ImplicitSelfKind::None,
2146 // Transform `-> T` into `-> impl Future<Output = T>` for `async fn`
2148 // fn_span: the span of the async function declaration. Used for error reporting.
2149 // inputs: lowered types of arguments to the function. Used to collect lifetimes.
2150 // output: unlowered output type (`T` in `-> T`)
2151 // fn_def_id: DefId of the parent function. Used to create child impl trait definition.
2152 fn lower_async_fn_ret_ty(
2155 output: &FunctionRetTy,
2157 return_impl_trait_id: NodeId,
2158 ) -> hir::FunctionRetTy {
2159 // Get lifetimes used in the input arguments to the function. Our output type must also
2160 // have the same lifetime.
2161 // FIXME(cramertj): multiple different lifetimes are not allowed because
2162 // `impl Trait + 'a + 'b` doesn't allow for capture `'a` and `'b` where neither is a subset
2163 // of the other. We really want some new lifetime that is a subset of all input lifetimes,
2164 // but that doesn't exist at the moment.
2166 struct AsyncFnLifetimeCollector<'r, 'a: 'r> {
2167 context: &'r mut LoweringContext<'a>,
2168 // Lifetimes bound by HRTB.
2169 currently_bound_lifetimes: Vec<hir::LifetimeName>,
2170 // Whether to count elided lifetimes.
2171 // Disabled inside of `Fn` or `fn` syntax.
2172 collect_elided_lifetimes: bool,
2173 // The lifetime found.
2174 // Multiple different or elided lifetimes cannot appear in async fn for now.
2175 output_lifetime: Option<(hir::LifetimeName, Span)>,
2178 impl<'r, 'a: 'r, 'v> hir::intravisit::Visitor<'v> for AsyncFnLifetimeCollector<'r, 'a> {
2179 fn nested_visit_map<'this>(
2181 ) -> hir::intravisit::NestedVisitorMap<'this, 'v> {
2182 hir::intravisit::NestedVisitorMap::None
2185 fn visit_generic_args(&mut self, span: Span, parameters: &'v hir::GenericArgs) {
2186 // Don't collect elided lifetimes used inside of `Fn()` syntax.
2187 if parameters.parenthesized {
2188 let old_collect_elided_lifetimes = self.collect_elided_lifetimes;
2189 self.collect_elided_lifetimes = false;
2190 hir::intravisit::walk_generic_args(self, span, parameters);
2191 self.collect_elided_lifetimes = old_collect_elided_lifetimes;
2193 hir::intravisit::walk_generic_args(self, span, parameters);
2197 fn visit_ty(&mut self, t: &'v hir::Ty) {
2198 // Don't collect elided lifetimes used inside of `fn()` syntax.
2199 if let &hir::TyKind::BareFn(_) = &t.node {
2200 let old_collect_elided_lifetimes = self.collect_elided_lifetimes;
2201 self.collect_elided_lifetimes = false;
2203 // Record the "stack height" of `for<'a>` lifetime bindings
2204 // to be able to later fully undo their introduction.
2205 let old_len = self.currently_bound_lifetimes.len();
2206 hir::intravisit::walk_ty(self, t);
2207 self.currently_bound_lifetimes.truncate(old_len);
2209 self.collect_elided_lifetimes = old_collect_elided_lifetimes;
2211 hir::intravisit::walk_ty(self, t);
2215 fn visit_poly_trait_ref(
2217 trait_ref: &'v hir::PolyTraitRef,
2218 modifier: hir::TraitBoundModifier,
2220 // Record the "stack height" of `for<'a>` lifetime bindings
2221 // to be able to later fully undo their introduction.
2222 let old_len = self.currently_bound_lifetimes.len();
2223 hir::intravisit::walk_poly_trait_ref(self, trait_ref, modifier);
2224 self.currently_bound_lifetimes.truncate(old_len);
2227 fn visit_generic_param(&mut self, param: &'v hir::GenericParam) {
2228 // Record the introduction of 'a in `for<'a> ...`
2229 if let hir::GenericParamKind::Lifetime { .. } = param.kind {
2230 // Introduce lifetimes one at a time so that we can handle
2231 // cases like `fn foo<'d>() -> impl for<'a, 'b: 'a, 'c: 'b + 'd>`
2232 let lt_name = hir::LifetimeName::Param(param.name);
2233 self.currently_bound_lifetimes.push(lt_name);
2236 hir::intravisit::walk_generic_param(self, param);
2239 fn visit_lifetime(&mut self, lifetime: &'v hir::Lifetime) {
2240 let name = match lifetime.name {
2241 hir::LifetimeName::Implicit | hir::LifetimeName::Underscore => {
2242 if self.collect_elided_lifetimes {
2243 // Use `'_` for both implicit and underscore lifetimes in
2244 // `abstract type Foo<'_>: SomeTrait<'_>;`
2245 hir::LifetimeName::Underscore
2250 hir::LifetimeName::Param(_) => lifetime.name,
2251 hir::LifetimeName::Error | hir::LifetimeName::Static => return,
2254 if !self.currently_bound_lifetimes.contains(&name) {
2255 if let Some((current_lt_name, current_lt_span)) = self.output_lifetime {
2256 // We don't currently have a reliable way to desugar `async fn` with
2257 // multiple potentially unrelated input lifetimes into
2258 // `-> impl Trait + 'lt`, so we report an error in this case.
2259 if current_lt_name != name {
2262 MultiSpan::from_spans(vec![current_lt_span, lifetime.span]),
2264 "multiple different lifetimes used in arguments of `async fn`",
2266 .span_label(current_lt_span, "first lifetime here")
2267 .span_label(lifetime.span, "different lifetime here")
2268 .help("`async fn` can only accept borrowed values \
2269 with identical lifetimes")
2271 } else if current_lt_name.is_elided() && name.is_elided() {
2274 MultiSpan::from_spans(vec![current_lt_span, lifetime.span]),
2276 "multiple elided lifetimes used in arguments of `async fn`",
2278 .span_label(current_lt_span, "first lifetime here")
2279 .span_label(lifetime.span, "different lifetime here")
2280 .help("consider giving these arguments named lifetimes")
2284 self.output_lifetime = Some((name, lifetime.span));
2290 let bound_lifetime = {
2291 let mut lifetime_collector = AsyncFnLifetimeCollector {
2293 currently_bound_lifetimes: Vec::new(),
2294 collect_elided_lifetimes: true,
2295 output_lifetime: None,
2299 hir::intravisit::walk_ty(&mut lifetime_collector, arg);
2301 lifetime_collector.output_lifetime
2304 let span = match output {
2305 FunctionRetTy::Ty(ty) => ty.span,
2306 FunctionRetTy::Default(span) => *span,
2309 let impl_trait_ty = self.lower_existential_impl_trait(
2310 span, Some(fn_def_id), return_impl_trait_id, |this| {
2311 let output_ty = match output {
2312 FunctionRetTy::Ty(ty) => {
2313 this.lower_ty(ty, ImplTraitContext::Existential(Some(fn_def_id)))
2315 FunctionRetTy::Default(span) => {
2316 let LoweredNodeId { node_id: _, hir_id } = this.next_id();
2319 node: hir::TyKind::Tup(hir_vec![]),
2326 let LoweredNodeId { node_id: _, hir_id } = this.next_id();
2327 let future_params = P(hir::GenericArgs {
2329 bindings: hir_vec![hir::TypeBinding {
2330 ident: Ident::from_str(FN_OUTPUT_NAME),
2335 parenthesized: false,
2339 this.std_path(span, &["future", "Future"], Some(future_params), false);
2341 let LoweredNodeId { node_id: _, hir_id } = this.next_id();
2342 let mut bounds = vec![
2343 hir::GenericBound::Trait(
2345 trait_ref: hir::TraitRef {
2349 bound_generic_params: hir_vec![],
2352 hir::TraitBoundModifier::None
2356 if let Some((name, span)) = bound_lifetime {
2357 let LoweredNodeId { node_id: _, hir_id } = this.next_id();
2358 bounds.push(hir::GenericBound::Outlives(
2359 hir::Lifetime { hir_id, name, span }));
2362 hir::HirVec::from(bounds)
2365 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
2366 let impl_trait_ty = P(hir::Ty {
2367 node: impl_trait_ty,
2372 hir::FunctionRetTy::Return(impl_trait_ty)
2375 fn lower_param_bound(
2378 itctx: ImplTraitContext<'_>,
2379 ) -> hir::GenericBound {
2381 GenericBound::Trait(ref ty, modifier) => {
2382 hir::GenericBound::Trait(
2383 self.lower_poly_trait_ref(ty, itctx),
2384 self.lower_trait_bound_modifier(modifier),
2387 GenericBound::Outlives(ref lifetime) => {
2388 hir::GenericBound::Outlives(self.lower_lifetime(lifetime))
2393 fn lower_lifetime(&mut self, l: &Lifetime) -> hir::Lifetime {
2394 let span = l.ident.span;
2396 ident if ident.name == keywords::StaticLifetime.name() =>
2397 self.new_named_lifetime(l.id, span, hir::LifetimeName::Static),
2398 ident if ident.name == keywords::UnderscoreLifetime.name() =>
2399 match self.anonymous_lifetime_mode {
2400 AnonymousLifetimeMode::CreateParameter => {
2401 let fresh_name = self.collect_fresh_in_band_lifetime(span);
2402 self.new_named_lifetime(l.id, span, hir::LifetimeName::Param(fresh_name))
2405 AnonymousLifetimeMode::PassThrough => {
2406 self.new_named_lifetime(l.id, span, hir::LifetimeName::Underscore)
2409 AnonymousLifetimeMode::ReportError => self.new_error_lifetime(Some(l.id), span),
2412 self.maybe_collect_in_band_lifetime(ident);
2413 let param_name = ParamName::Plain(ident);
2414 self.new_named_lifetime(l.id, span, hir::LifetimeName::Param(param_name))
2419 fn new_named_lifetime(
2423 name: hir::LifetimeName,
2424 ) -> hir::Lifetime {
2425 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(id);
2434 fn lower_generic_params(
2436 params: &[GenericParam],
2437 add_bounds: &NodeMap<Vec<GenericBound>>,
2438 mut itctx: ImplTraitContext<'_>,
2439 ) -> hir::HirVec<hir::GenericParam> {
2440 params.iter().map(|param| {
2441 self.lower_generic_param(param, add_bounds, itctx.reborrow())
2445 fn lower_generic_param(&mut self,
2446 param: &GenericParam,
2447 add_bounds: &NodeMap<Vec<GenericBound>>,
2448 mut itctx: ImplTraitContext<'_>)
2449 -> hir::GenericParam {
2450 let mut bounds = self.with_anonymous_lifetime_mode(
2451 AnonymousLifetimeMode::ReportError,
2452 |this| this.lower_param_bounds(¶m.bounds, itctx.reborrow()),
2455 let (name, kind) = match param.kind {
2456 GenericParamKind::Lifetime => {
2457 let was_collecting_in_band = self.is_collecting_in_band_lifetimes;
2458 self.is_collecting_in_band_lifetimes = false;
2460 let lt = self.with_anonymous_lifetime_mode(
2461 AnonymousLifetimeMode::ReportError,
2462 |this| this.lower_lifetime(&Lifetime { id: param.id, ident: param.ident }),
2464 let param_name = match lt.name {
2465 hir::LifetimeName::Param(param_name) => param_name,
2466 hir::LifetimeName::Implicit
2467 | hir::LifetimeName::Underscore
2468 | hir::LifetimeName::Static => hir::ParamName::Plain(lt.name.ident()),
2469 hir::LifetimeName::Error => ParamName::Error,
2472 let kind = hir::GenericParamKind::Lifetime {
2473 kind: hir::LifetimeParamKind::Explicit
2476 self.is_collecting_in_band_lifetimes = was_collecting_in_band;
2480 GenericParamKind::Type { ref default, .. } => {
2481 // Don't expose `Self` (recovered "keyword used as ident" parse error).
2482 // `rustc::ty` expects `Self` to be only used for a trait's `Self`.
2483 // Instead, use `gensym("Self")` to create a distinct name that looks the same.
2484 let ident = if param.ident.name == keywords::SelfUpper.name() {
2485 param.ident.gensym()
2490 let add_bounds = add_bounds.get(¶m.id).map_or(&[][..], |x| &x);
2491 if !add_bounds.is_empty() {
2492 let params = self.lower_param_bounds(add_bounds, itctx.reborrow()).into_iter();
2493 bounds = bounds.into_iter()
2498 let kind = hir::GenericParamKind::Type {
2499 default: default.as_ref().map(|x| {
2500 self.lower_ty(x, ImplTraitContext::disallowed())
2502 synthetic: param.attrs.iter()
2503 .filter(|attr| attr.check_name("rustc_synthetic"))
2504 .map(|_| hir::SyntheticTyParamKind::ImplTrait)
2508 (hir::ParamName::Plain(ident), kind)
2510 GenericParamKind::Const { ref ty } => {
2511 (hir::ParamName::Plain(param.ident), hir::GenericParamKind::Const {
2512 ty: self.lower_ty(&ty, ImplTraitContext::disallowed()),
2517 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(param.id);
2522 span: param.ident.span,
2523 pure_wrt_drop: attr::contains_name(¶m.attrs, "may_dangle"),
2524 attrs: self.lower_attrs(¶m.attrs),
2532 generics: &Generics,
2533 itctx: ImplTraitContext<'_>)
2536 // Collect `?Trait` bounds in where clause and move them to parameter definitions.
2537 // FIXME: this could probably be done with less rightward drift. Also looks like two control
2538 // paths where report_error is called are also the only paths that advance to after
2539 // the match statement, so the error reporting could probably just be moved there.
2540 let mut add_bounds: NodeMap<Vec<_>> = Default::default();
2541 for pred in &generics.where_clause.predicates {
2542 if let WherePredicate::BoundPredicate(ref bound_pred) = *pred {
2543 'next_bound: for bound in &bound_pred.bounds {
2544 if let GenericBound::Trait(_, TraitBoundModifier::Maybe) = *bound {
2545 let report_error = |this: &mut Self| {
2546 this.diagnostic().span_err(
2547 bound_pred.bounded_ty.span,
2548 "`?Trait` bounds are only permitted at the \
2549 point where a type parameter is declared",
2552 // Check if the where clause type is a plain type parameter.
2553 match bound_pred.bounded_ty.node {
2554 TyKind::Path(None, ref path)
2555 if path.segments.len() == 1
2556 && bound_pred.bound_generic_params.is_empty() =>
2558 if let Some(Def::TyParam(def_id)) = self.resolver
2559 .get_resolution(bound_pred.bounded_ty.id)
2560 .map(|d| d.base_def())
2562 if let Some(node_id) =
2563 self.resolver.definitions().as_local_node_id(def_id)
2565 for param in &generics.params {
2567 GenericParamKind::Type { .. } => {
2568 if node_id == param.id {
2569 add_bounds.entry(param.id)
2571 .push(bound.clone());
2572 continue 'next_bound;
2582 _ => report_error(self),
2590 params: self.lower_generic_params(&generics.params, &add_bounds, itctx),
2591 where_clause: self.lower_where_clause(&generics.where_clause),
2592 span: generics.span,
2596 fn lower_where_clause(&mut self, wc: &WhereClause) -> hir::WhereClause {
2597 self.with_anonymous_lifetime_mode(
2598 AnonymousLifetimeMode::ReportError,
2600 let LoweredNodeId { node_id: _, hir_id } = this.lower_node_id(wc.id);
2604 predicates: wc.predicates
2606 .map(|predicate| this.lower_where_predicate(predicate))
2613 fn lower_where_predicate(&mut self, pred: &WherePredicate) -> hir::WherePredicate {
2615 WherePredicate::BoundPredicate(WhereBoundPredicate {
2616 ref bound_generic_params,
2621 self.with_in_scope_lifetime_defs(
2622 &bound_generic_params,
2624 hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
2625 bound_generic_params: this.lower_generic_params(
2626 bound_generic_params,
2627 &NodeMap::default(),
2628 ImplTraitContext::disallowed(),
2630 bounded_ty: this.lower_ty(bounded_ty, ImplTraitContext::disallowed()),
2633 .filter_map(|bound| match *bound {
2634 // Ignore `?Trait` bounds.
2635 // They were copied into type parameters already.
2636 GenericBound::Trait(_, TraitBoundModifier::Maybe) => None,
2637 _ => Some(this.lower_param_bound(
2639 ImplTraitContext::disallowed(),
2648 WherePredicate::RegionPredicate(WhereRegionPredicate {
2652 }) => hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate {
2654 lifetime: self.lower_lifetime(lifetime),
2655 bounds: self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
2657 WherePredicate::EqPredicate(WhereEqPredicate {
2663 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(id);
2665 hir::WherePredicate::EqPredicate(hir::WhereEqPredicate {
2667 lhs_ty: self.lower_ty(lhs_ty, ImplTraitContext::disallowed()),
2668 rhs_ty: self.lower_ty(rhs_ty, ImplTraitContext::disallowed()),
2675 fn lower_variant_data(&mut self, vdata: &VariantData) -> hir::VariantData {
2677 VariantData::Struct(ref fields, id) => {
2678 let LoweredNodeId { node_id, hir_id } = self.lower_node_id(id);
2680 hir::VariantData::Struct(
2684 .map(|f| self.lower_struct_field(f))
2690 VariantData::Tuple(ref fields, id) => {
2691 let LoweredNodeId { node_id, hir_id } = self.lower_node_id(id);
2693 hir::VariantData::Tuple(
2697 .map(|f| self.lower_struct_field(f))
2703 VariantData::Unit(id) => {
2704 let LoweredNodeId { node_id, hir_id } = self.lower_node_id(id);
2706 hir::VariantData::Unit(node_id, hir_id)
2711 fn lower_trait_ref(&mut self, p: &TraitRef, itctx: ImplTraitContext<'_>) -> hir::TraitRef {
2712 let path = match self.lower_qpath(p.ref_id, &None, &p.path, ParamMode::Explicit, itctx) {
2713 hir::QPath::Resolved(None, path) => path.and_then(|path| path),
2714 qpath => bug!("lower_trait_ref: unexpected QPath `{:?}`", qpath),
2716 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(p.ref_id);
2723 fn lower_poly_trait_ref(
2726 mut itctx: ImplTraitContext<'_>,
2727 ) -> hir::PolyTraitRef {
2728 let bound_generic_params = self.lower_generic_params(
2729 &p.bound_generic_params,
2730 &NodeMap::default(),
2733 let trait_ref = self.with_parent_impl_lifetime_defs(
2734 &bound_generic_params,
2735 |this| this.lower_trait_ref(&p.trait_ref, itctx),
2739 bound_generic_params,
2745 fn lower_struct_field(&mut self, (index, f): (usize, &StructField)) -> hir::StructField {
2746 let LoweredNodeId { node_id, hir_id } = self.lower_node_id(f.id);
2752 ident: match f.ident {
2753 Some(ident) => ident,
2754 // FIXME(jseyfried): positional field hygiene
2755 None => Ident::new(Symbol::intern(&index.to_string()), f.span),
2757 vis: self.lower_visibility(&f.vis, None),
2758 ty: self.lower_ty(&f.ty, ImplTraitContext::disallowed()),
2759 attrs: self.lower_attrs(&f.attrs),
2763 fn lower_field(&mut self, f: &Field) -> hir::Field {
2764 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
2769 expr: P(self.lower_expr(&f.expr)),
2771 is_shorthand: f.is_shorthand,
2775 fn lower_mt(&mut self, mt: &MutTy, itctx: ImplTraitContext<'_>) -> hir::MutTy {
2777 ty: self.lower_ty(&mt.ty, itctx),
2778 mutbl: self.lower_mutability(mt.mutbl),
2782 fn lower_param_bounds(&mut self, bounds: &[GenericBound], mut itctx: ImplTraitContext<'_>)
2783 -> hir::GenericBounds {
2784 bounds.iter().map(|bound| self.lower_param_bound(bound, itctx.reborrow())).collect()
2787 fn lower_block(&mut self, b: &Block, targeted_by_break: bool) -> P<hir::Block> {
2788 let mut expr = None;
2790 let mut stmts = vec![];
2792 for (index, stmt) in b.stmts.iter().enumerate() {
2793 if index == b.stmts.len() - 1 {
2794 if let StmtKind::Expr(ref e) = stmt.node {
2795 expr = Some(P(self.lower_expr(e)));
2797 stmts.extend(self.lower_stmt(stmt));
2800 stmts.extend(self.lower_stmt(stmt));
2804 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(b.id);
2808 stmts: stmts.into(),
2810 rules: self.lower_block_check_mode(&b.rules),
2816 fn lower_async_body(
2822 self.lower_body(Some(decl), |this| {
2823 if let IsAsync::Async { closure_id, .. } = asyncness {
2824 let async_expr = this.make_async_expr(
2825 CaptureBy::Value, closure_id, None,
2827 let body = this.lower_block(body, false);
2828 this.expr_block(body, ThinVec::new())
2830 this.expr(body.span, async_expr, ThinVec::new())
2832 let body = this.lower_block(body, false);
2833 this.expr_block(body, ThinVec::new())
2842 attrs: &hir::HirVec<Attribute>,
2843 vis: &mut hir::Visibility,
2845 ) -> hir::ItemKind {
2847 ItemKind::ExternCrate(orig_name) => hir::ItemKind::ExternCrate(orig_name),
2848 ItemKind::Use(ref use_tree) => {
2849 // Start with an empty prefix
2852 span: use_tree.span,
2855 self.lower_use_tree(use_tree, &prefix, id, vis, ident, attrs)
2857 ItemKind::Static(ref t, m, ref e) => {
2858 let value = self.lower_body(None, |this| this.lower_expr(e));
2859 hir::ItemKind::Static(
2862 if self.sess.features_untracked().impl_trait_in_bindings {
2863 ImplTraitContext::Existential(None)
2865 ImplTraitContext::Disallowed(ImplTraitPosition::Binding)
2868 self.lower_mutability(m),
2872 ItemKind::Const(ref t, ref e) => {
2873 let value = self.lower_body(None, |this| this.lower_expr(e));
2874 hir::ItemKind::Const(
2877 if self.sess.features_untracked().impl_trait_in_bindings {
2878 ImplTraitContext::Existential(None)
2880 ImplTraitContext::Disallowed(ImplTraitPosition::Binding)
2886 ItemKind::Fn(ref decl, header, ref generics, ref body) => {
2887 let fn_def_id = self.resolver.definitions().local_def_id(id);
2888 self.with_new_scopes(|this| {
2889 // Note: we don't need to change the return type from `T` to
2890 // `impl Future<Output = T>` here because lower_body
2891 // only cares about the input argument patterns in the function
2892 // declaration (decl), not the return types.
2893 let body_id = this.lower_async_body(decl, header.asyncness.node, body);
2895 let (generics, fn_decl) = this.add_in_band_defs(
2898 AnonymousLifetimeMode::PassThrough,
2899 |this, idty| this.lower_fn_decl(
2901 Some((fn_def_id, idty)),
2903 header.asyncness.node.opt_return_id()
2909 this.lower_fn_header(header),
2915 ItemKind::Mod(ref m) => hir::ItemKind::Mod(self.lower_mod(m)),
2916 ItemKind::ForeignMod(ref nm) => hir::ItemKind::ForeignMod(self.lower_foreign_mod(nm)),
2917 ItemKind::GlobalAsm(ref ga) => hir::ItemKind::GlobalAsm(self.lower_global_asm(ga)),
2918 ItemKind::Ty(ref t, ref generics) => hir::ItemKind::Ty(
2919 self.lower_ty(t, ImplTraitContext::disallowed()),
2920 self.lower_generics(generics, ImplTraitContext::disallowed()),
2922 ItemKind::Existential(ref b, ref generics) => hir::ItemKind::Existential(hir::ExistTy {
2923 generics: self.lower_generics(generics, ImplTraitContext::disallowed()),
2924 bounds: self.lower_param_bounds(b, ImplTraitContext::disallowed()),
2925 impl_trait_fn: None,
2927 ItemKind::Enum(ref enum_definition, ref generics) => hir::ItemKind::Enum(
2929 variants: enum_definition
2932 .map(|x| self.lower_variant(x))
2935 self.lower_generics(generics, ImplTraitContext::disallowed()),
2937 ItemKind::Struct(ref struct_def, ref generics) => {
2938 let struct_def = self.lower_variant_data(struct_def);
2939 hir::ItemKind::Struct(
2941 self.lower_generics(generics, ImplTraitContext::disallowed()),
2944 ItemKind::Union(ref vdata, ref generics) => {
2945 let vdata = self.lower_variant_data(vdata);
2946 hir::ItemKind::Union(
2948 self.lower_generics(generics, ImplTraitContext::disallowed()),
2960 let def_id = self.resolver.definitions().local_def_id(id);
2962 // Lower the "impl header" first. This ordering is important
2963 // for in-band lifetimes! Consider `'a` here:
2965 // impl Foo<'a> for u32 {
2966 // fn method(&'a self) { .. }
2969 // Because we start by lowering the `Foo<'a> for u32`
2970 // part, we will add `'a` to the list of generics on
2971 // the impl. When we then encounter it later in the
2972 // method, it will not be considered an in-band
2973 // lifetime to be added, but rather a reference to a
2975 let (generics, (trait_ref, lowered_ty)) = self.add_in_band_defs(
2978 AnonymousLifetimeMode::CreateParameter,
2980 let trait_ref = trait_ref.as_ref().map(|trait_ref| {
2981 this.lower_trait_ref(trait_ref, ImplTraitContext::disallowed())
2984 if let Some(ref trait_ref) = trait_ref {
2985 if let Def::Trait(def_id) = trait_ref.path.def {
2986 this.trait_impls.entry(def_id).or_default().push(id);
2990 let lowered_ty = this.lower_ty(ty, ImplTraitContext::disallowed());
2992 (trait_ref, lowered_ty)
2996 let new_impl_items = self.with_in_scope_lifetime_defs(
2997 &ast_generics.params,
3001 .map(|item| this.lower_impl_item_ref(item))
3006 hir::ItemKind::Impl(
3007 self.lower_unsafety(unsafety),
3008 self.lower_impl_polarity(polarity),
3009 self.lower_defaultness(defaultness, true /* [1] */),
3016 ItemKind::Trait(is_auto, unsafety, ref generics, ref bounds, ref items) => {
3017 let bounds = self.lower_param_bounds(bounds, ImplTraitContext::disallowed());
3020 .map(|item| self.lower_trait_item_ref(item))
3022 hir::ItemKind::Trait(
3023 self.lower_is_auto(is_auto),
3024 self.lower_unsafety(unsafety),
3025 self.lower_generics(generics, ImplTraitContext::disallowed()),
3030 ItemKind::TraitAlias(ref generics, ref bounds) => hir::ItemKind::TraitAlias(
3031 self.lower_generics(generics, ImplTraitContext::disallowed()),
3032 self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
3034 ItemKind::MacroDef(..) | ItemKind::Mac(..) => panic!("Shouldn't still be around"),
3037 // [1] `defaultness.has_value()` is never called for an `impl`, always `true` in order to
3038 // not cause an assertion failure inside the `lower_defaultness` function.
3046 vis: &mut hir::Visibility,
3048 attrs: &hir::HirVec<Attribute>,
3049 ) -> hir::ItemKind {
3050 debug!("lower_use_tree(tree={:?})", tree);
3051 debug!("lower_use_tree: vis = {:?}", vis);
3053 let path = &tree.prefix;
3054 let segments = prefix
3057 .chain(path.segments.iter())
3062 UseTreeKind::Simple(rename, id1, id2) => {
3063 *ident = tree.ident();
3065 // First, apply the prefix to the path.
3066 let mut path = Path {
3071 // Correctly resolve `self` imports.
3072 if path.segments.len() > 1
3073 && path.segments.last().unwrap().ident.name == keywords::SelfLower.name()
3075 let _ = path.segments.pop();
3076 if rename.is_none() {
3077 *ident = path.segments.last().unwrap().ident;
3081 let parent_def_index = self.current_hir_id_owner.last().unwrap().0;
3082 let mut defs = self.expect_full_def_from_use(id);
3083 // We want to return *something* from this function, so hold onto the first item
3085 let ret_def = defs.next().unwrap_or(Def::Err);
3087 // Here, we are looping over namespaces, if they exist for the definition
3088 // being imported. We only handle type and value namespaces because we
3089 // won't be dealing with macros in the rest of the compiler.
3090 // Essentially a single `use` which imports two names is desugared into
3092 for (def, &new_node_id) in defs.zip([id1, id2].iter()) {
3093 let vis = vis.clone();
3094 let ident = ident.clone();
3095 let mut path = path.clone();
3096 for seg in &mut path.segments {
3097 seg.id = self.sess.next_node_id();
3099 let span = path.span;
3100 self.resolver.definitions().create_def_with_parent(
3104 DefIndexAddressSpace::High,
3107 self.allocate_hir_id_counter(new_node_id, &path);
3109 self.with_hir_id_owner(new_node_id, |this| {
3110 let new_id = this.lower_node_id(new_node_id);
3112 this.lower_path_extra(def, &path, ParamMode::Explicit, None);
3113 let item = hir::ItemKind::Use(P(path), hir::UseKind::Single);
3114 let vis_kind = match vis.node {
3115 hir::VisibilityKind::Public => hir::VisibilityKind::Public,
3116 hir::VisibilityKind::Crate(sugar) => hir::VisibilityKind::Crate(sugar),
3117 hir::VisibilityKind::Inherited => hir::VisibilityKind::Inherited,
3118 hir::VisibilityKind::Restricted { ref path, hir_id: _ } => {
3119 let id = this.next_id();
3120 let path = this.renumber_segment_ids(path);
3121 hir::VisibilityKind::Restricted {
3127 let vis = respan(vis.span, vis_kind);
3133 hir_id: new_id.hir_id,
3135 attrs: attrs.clone(),
3145 P(self.lower_path_extra(ret_def, &path, ParamMode::Explicit, None));
3146 hir::ItemKind::Use(path, hir::UseKind::Single)
3148 UseTreeKind::Glob => {
3149 let path = P(self.lower_path(
3155 ParamMode::Explicit,
3157 hir::ItemKind::Use(path, hir::UseKind::Glob)
3159 UseTreeKind::Nested(ref trees) => {
3160 // Nested imports are desugared into simple imports.
3161 // So, if we start with
3164 // pub(x) use foo::{a, b};
3167 // we will create three items:
3170 // pub(x) use foo::a;
3171 // pub(x) use foo::b;
3172 // pub(x) use foo::{}; // <-- this is called the `ListStem`
3175 // The first two are produced by recursively invoking
3176 // `lower_use_tree` (and indeed there may be things
3177 // like `use foo::{a::{b, c}}` and so forth). They
3178 // wind up being directly added to
3179 // `self.items`. However, the structure of this
3180 // function also requires us to return one item, and
3181 // for that we return the `{}` import (called the
3186 span: prefix.span.to(path.span),
3189 // Add all the nested `PathListItem`s to the HIR.
3190 for &(ref use_tree, id) in trees {
3191 self.allocate_hir_id_counter(id, &use_tree);
3196 } = self.lower_node_id(id);
3198 let mut vis = vis.clone();
3199 let mut ident = ident.clone();
3200 let mut prefix = prefix.clone();
3202 // Give the segments new node-ids since they are being cloned.
3203 for seg in &mut prefix.segments {
3204 seg.id = self.sess.next_node_id();
3207 // Each `use` import is an item and thus are owners of the
3208 // names in the path. Up to this point the nested import is
3209 // the current owner, since we want each desugared import to
3210 // own its own names, we have to adjust the owner before
3211 // lowering the rest of the import.
3212 self.with_hir_id_owner(new_id, |this| {
3213 let item = this.lower_use_tree(use_tree,
3220 let vis_kind = match vis.node {
3221 hir::VisibilityKind::Public => hir::VisibilityKind::Public,
3222 hir::VisibilityKind::Crate(sugar) => hir::VisibilityKind::Crate(sugar),
3223 hir::VisibilityKind::Inherited => hir::VisibilityKind::Inherited,
3224 hir::VisibilityKind::Restricted { ref path, hir_id: _ } => {
3225 let id = this.next_id();
3226 let path = this.renumber_segment_ids(path);
3227 hir::VisibilityKind::Restricted {
3233 let vis = respan(vis.span, vis_kind);
3241 attrs: attrs.clone(),
3244 span: use_tree.span,
3250 // Subtle and a bit hacky: we lower the privacy level
3251 // of the list stem to "private" most of the time, but
3252 // not for "restricted" paths. The key thing is that
3253 // we don't want it to stay as `pub` (with no caveats)
3254 // because that affects rustdoc and also the lints
3255 // about `pub` items. But we can't *always* make it
3256 // private -- particularly not for restricted paths --
3257 // because it contains node-ids that would then be
3258 // unused, failing the check that HirIds are "densely
3261 hir::VisibilityKind::Public |
3262 hir::VisibilityKind::Crate(_) |
3263 hir::VisibilityKind::Inherited => {
3264 *vis = respan(prefix.span.shrink_to_lo(), hir::VisibilityKind::Inherited);
3266 hir::VisibilityKind::Restricted { .. } => {
3267 // Do nothing here, as described in the comment on the match.
3271 let def = self.expect_full_def_from_use(id).next().unwrap_or(Def::Err);
3272 let path = P(self.lower_path_extra(def, &prefix, ParamMode::Explicit, None));
3273 hir::ItemKind::Use(path, hir::UseKind::ListStem)
3278 /// Paths like the visibility path in `pub(super) use foo::{bar, baz}` are repeated
3279 /// many times in the HIR tree; for each occurrence, we need to assign distinct
3280 /// `NodeId`s. (See, e.g., #56128.)
3281 fn renumber_segment_ids(&mut self, path: &P<hir::Path>) -> P<hir::Path> {
3282 debug!("renumber_segment_ids(path = {:?})", path);
3283 let mut path = path.clone();
3284 for seg in path.segments.iter_mut() {
3285 if seg.id.is_some() {
3286 let next_id = self.next_id();
3287 seg.id = Some(next_id.node_id);
3288 seg.hir_id = Some(next_id.hir_id);
3294 fn lower_trait_item(&mut self, i: &TraitItem) -> hir::TraitItem {
3295 let LoweredNodeId { node_id, hir_id } = self.lower_node_id(i.id);
3296 let trait_item_def_id = self.resolver.definitions().local_def_id(node_id);
3298 let (generics, node) = match i.node {
3299 TraitItemKind::Const(ref ty, ref default) => (
3300 self.lower_generics(&i.generics, ImplTraitContext::disallowed()),
3301 hir::TraitItemKind::Const(
3302 self.lower_ty(ty, ImplTraitContext::disallowed()),
3305 .map(|x| self.lower_body(None, |this| this.lower_expr(x))),
3308 TraitItemKind::Method(ref sig, None) => {
3309 let names = self.lower_fn_args_to_names(&sig.decl);
3310 let (generics, sig) = self.lower_method_sig(
3317 (generics, hir::TraitItemKind::Method(sig, hir::TraitMethod::Required(names)))
3319 TraitItemKind::Method(ref sig, Some(ref body)) => {
3320 let body_id = self.lower_body(Some(&sig.decl), |this| {
3321 let body = this.lower_block(body, false);
3322 this.expr_block(body, ThinVec::new())
3324 let (generics, sig) = self.lower_method_sig(
3331 (generics, hir::TraitItemKind::Method(sig, hir::TraitMethod::Provided(body_id)))
3333 TraitItemKind::Type(ref bounds, ref default) => (
3334 self.lower_generics(&i.generics, ImplTraitContext::disallowed()),
3335 hir::TraitItemKind::Type(
3336 self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
3339 .map(|x| self.lower_ty(x, ImplTraitContext::disallowed())),
3342 TraitItemKind::Macro(..) => panic!("Shouldn't exist any more"),
3348 attrs: self.lower_attrs(&i.attrs),
3355 fn lower_trait_item_ref(&mut self, i: &TraitItem) -> hir::TraitItemRef {
3356 let (kind, has_default) = match i.node {
3357 TraitItemKind::Const(_, ref default) => {
3358 (hir::AssociatedItemKind::Const, default.is_some())
3360 TraitItemKind::Type(_, ref default) => {
3361 (hir::AssociatedItemKind::Type, default.is_some())
3363 TraitItemKind::Method(ref sig, ref default) => (
3364 hir::AssociatedItemKind::Method {
3365 has_self: sig.decl.has_self(),
3369 TraitItemKind::Macro(..) => unimplemented!(),
3372 id: hir::TraitItemId { node_id: i.id },
3375 defaultness: self.lower_defaultness(Defaultness::Default, has_default),
3380 fn lower_impl_item(&mut self, i: &ImplItem) -> hir::ImplItem {
3381 let LoweredNodeId { node_id, hir_id } = self.lower_node_id(i.id);
3382 let impl_item_def_id = self.resolver.definitions().local_def_id(node_id);
3384 let (generics, node) = match i.node {
3385 ImplItemKind::Const(ref ty, ref expr) => {
3386 let body_id = self.lower_body(None, |this| this.lower_expr(expr));
3388 self.lower_generics(&i.generics, ImplTraitContext::disallowed()),
3389 hir::ImplItemKind::Const(
3390 self.lower_ty(ty, ImplTraitContext::disallowed()),
3395 ImplItemKind::Method(ref sig, ref body) => {
3396 let body_id = self.lower_async_body(&sig.decl, sig.header.asyncness.node, body);
3397 let impl_trait_return_allow = !self.is_in_trait_impl;
3398 let (generics, sig) = self.lower_method_sig(
3402 impl_trait_return_allow,
3403 sig.header.asyncness.node.opt_return_id(),
3405 (generics, hir::ImplItemKind::Method(sig, body_id))
3407 ImplItemKind::Type(ref ty) => (
3408 self.lower_generics(&i.generics, ImplTraitContext::disallowed()),
3409 hir::ImplItemKind::Type(self.lower_ty(ty, ImplTraitContext::disallowed())),
3411 ImplItemKind::Existential(ref bounds) => (
3412 self.lower_generics(&i.generics, ImplTraitContext::disallowed()),
3413 hir::ImplItemKind::Existential(
3414 self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
3417 ImplItemKind::Macro(..) => panic!("Shouldn't exist any more"),
3423 attrs: self.lower_attrs(&i.attrs),
3425 vis: self.lower_visibility(&i.vis, None),
3426 defaultness: self.lower_defaultness(i.defaultness, true /* [1] */),
3431 // [1] since `default impl` is not yet implemented, this is always true in impls
3434 fn lower_impl_item_ref(&mut self, i: &ImplItem) -> hir::ImplItemRef {
3436 id: hir::ImplItemId { node_id: i.id },
3439 vis: self.lower_visibility(&i.vis, Some(i.id)),
3440 defaultness: self.lower_defaultness(i.defaultness, true /* [1] */),
3441 kind: match i.node {
3442 ImplItemKind::Const(..) => hir::AssociatedItemKind::Const,
3443 ImplItemKind::Type(..) => hir::AssociatedItemKind::Type,
3444 ImplItemKind::Existential(..) => hir::AssociatedItemKind::Existential,
3445 ImplItemKind::Method(ref sig, _) => hir::AssociatedItemKind::Method {
3446 has_self: sig.decl.has_self(),
3448 ImplItemKind::Macro(..) => unimplemented!(),
3452 // [1] since `default impl` is not yet implemented, this is always true in impls
3455 fn lower_mod(&mut self, m: &Mod) -> hir::Mod {
3458 item_ids: m.items.iter().flat_map(|x| self.lower_item_id(x)).collect(),
3462 fn lower_item_id(&mut self, i: &Item) -> SmallVec<[hir::ItemId; 1]> {
3464 ItemKind::Use(ref use_tree) => {
3465 let mut vec = smallvec![hir::ItemId { id: i.id }];
3466 self.lower_item_id_use_tree(use_tree, i.id, &mut vec);
3469 ItemKind::MacroDef(..) => SmallVec::new(),
3471 ItemKind::Impl(.., None, _, _) => smallvec![hir::ItemId { id: i.id }],
3472 ItemKind::Static(ref ty, ..) => {
3473 let mut ids = smallvec![hir::ItemId { id: i.id }];
3474 if self.sess.features_untracked().impl_trait_in_bindings {
3475 let mut visitor = ImplTraitTypeIdVisitor { ids: &mut ids };
3476 visitor.visit_ty(ty);
3480 ItemKind::Const(ref ty, ..) => {
3481 let mut ids = smallvec![hir::ItemId { id: i.id }];
3482 if self.sess.features_untracked().impl_trait_in_bindings {
3483 let mut visitor = ImplTraitTypeIdVisitor { ids: &mut ids };
3484 visitor.visit_ty(ty);
3488 _ => smallvec![hir::ItemId { id: i.id }],
3492 fn lower_item_id_use_tree(&mut self,
3495 vec: &mut SmallVec<[hir::ItemId; 1]>)
3498 UseTreeKind::Nested(ref nested_vec) => for &(ref nested, id) in nested_vec {
3499 vec.push(hir::ItemId { id });
3500 self.lower_item_id_use_tree(nested, id, vec);
3502 UseTreeKind::Glob => {}
3503 UseTreeKind::Simple(_, id1, id2) => {
3504 for (_, &id) in self.expect_full_def_from_use(base_id)
3506 .zip([id1, id2].iter())
3508 vec.push(hir::ItemId { id });
3514 pub fn lower_item(&mut self, i: &Item) -> Option<hir::Item> {
3515 let mut ident = i.ident;
3516 let mut vis = self.lower_visibility(&i.vis, None);
3517 let attrs = self.lower_attrs(&i.attrs);
3518 if let ItemKind::MacroDef(ref def) = i.node {
3519 if !def.legacy || attr::contains_name(&i.attrs, "macro_export") ||
3520 attr::contains_name(&i.attrs, "rustc_doc_only_macro") {
3521 let body = self.lower_token_stream(def.stream());
3522 let hir_id = self.lower_node_id(i.id).hir_id;
3523 self.exported_macros.push(hir::MacroDef {
3536 let node = self.lower_item_kind(i.id, &mut ident, &attrs, &mut vis, &i.node);
3538 let LoweredNodeId { node_id, hir_id } = self.lower_node_id(i.id);
3551 fn lower_foreign_item(&mut self, i: &ForeignItem) -> hir::ForeignItem {
3552 let LoweredNodeId { node_id, hir_id } = self.lower_node_id(i.id);
3553 let def_id = self.resolver.definitions().local_def_id(node_id);
3558 attrs: self.lower_attrs(&i.attrs),
3559 node: match i.node {
3560 ForeignItemKind::Fn(ref fdec, ref generics) => {
3561 let (generics, (fn_dec, fn_args)) = self.add_in_band_defs(
3564 AnonymousLifetimeMode::PassThrough,
3567 // Disallow impl Trait in foreign items
3568 this.lower_fn_decl(fdec, None, false, None),
3569 this.lower_fn_args_to_names(fdec),
3574 hir::ForeignItemKind::Fn(fn_dec, fn_args, generics)
3576 ForeignItemKind::Static(ref t, m) => {
3577 hir::ForeignItemKind::Static(
3578 self.lower_ty(t, ImplTraitContext::disallowed()), m)
3580 ForeignItemKind::Ty => hir::ForeignItemKind::Type,
3581 ForeignItemKind::Macro(_) => panic!("shouldn't exist here"),
3583 vis: self.lower_visibility(&i.vis, None),
3588 fn lower_method_sig(
3590 generics: &Generics,
3593 impl_trait_return_allow: bool,
3594 is_async: Option<NodeId>,
3595 ) -> (hir::Generics, hir::MethodSig) {
3596 let header = self.lower_fn_header(sig.header);
3597 let (generics, decl) = self.add_in_band_defs(
3600 AnonymousLifetimeMode::PassThrough,
3601 |this, idty| this.lower_fn_decl(
3603 Some((fn_def_id, idty)),
3604 impl_trait_return_allow,
3608 (generics, hir::MethodSig { header, decl })
3611 fn lower_is_auto(&mut self, a: IsAuto) -> hir::IsAuto {
3613 IsAuto::Yes => hir::IsAuto::Yes,
3614 IsAuto::No => hir::IsAuto::No,
3618 fn lower_fn_header(&mut self, h: FnHeader) -> hir::FnHeader {
3620 unsafety: self.lower_unsafety(h.unsafety),
3621 asyncness: self.lower_asyncness(h.asyncness.node),
3622 constness: self.lower_constness(h.constness),
3627 fn lower_unsafety(&mut self, u: Unsafety) -> hir::Unsafety {
3629 Unsafety::Unsafe => hir::Unsafety::Unsafe,
3630 Unsafety::Normal => hir::Unsafety::Normal,
3634 fn lower_constness(&mut self, c: Spanned<Constness>) -> hir::Constness {
3636 Constness::Const => hir::Constness::Const,
3637 Constness::NotConst => hir::Constness::NotConst,
3641 fn lower_asyncness(&mut self, a: IsAsync) -> hir::IsAsync {
3643 IsAsync::Async { .. } => hir::IsAsync::Async,
3644 IsAsync::NotAsync => hir::IsAsync::NotAsync,
3648 fn lower_unop(&mut self, u: UnOp) -> hir::UnOp {
3650 UnOp::Deref => hir::UnDeref,
3651 UnOp::Not => hir::UnNot,
3652 UnOp::Neg => hir::UnNeg,
3656 fn lower_binop(&mut self, b: BinOp) -> hir::BinOp {
3658 node: match b.node {
3659 BinOpKind::Add => hir::BinOpKind::Add,
3660 BinOpKind::Sub => hir::BinOpKind::Sub,
3661 BinOpKind::Mul => hir::BinOpKind::Mul,
3662 BinOpKind::Div => hir::BinOpKind::Div,
3663 BinOpKind::Rem => hir::BinOpKind::Rem,
3664 BinOpKind::And => hir::BinOpKind::And,
3665 BinOpKind::Or => hir::BinOpKind::Or,
3666 BinOpKind::BitXor => hir::BinOpKind::BitXor,
3667 BinOpKind::BitAnd => hir::BinOpKind::BitAnd,
3668 BinOpKind::BitOr => hir::BinOpKind::BitOr,
3669 BinOpKind::Shl => hir::BinOpKind::Shl,
3670 BinOpKind::Shr => hir::BinOpKind::Shr,
3671 BinOpKind::Eq => hir::BinOpKind::Eq,
3672 BinOpKind::Lt => hir::BinOpKind::Lt,
3673 BinOpKind::Le => hir::BinOpKind::Le,
3674 BinOpKind::Ne => hir::BinOpKind::Ne,
3675 BinOpKind::Ge => hir::BinOpKind::Ge,
3676 BinOpKind::Gt => hir::BinOpKind::Gt,
3682 fn lower_pat(&mut self, p: &Pat) -> P<hir::Pat> {
3683 let node = match p.node {
3684 PatKind::Wild => hir::PatKind::Wild,
3685 PatKind::Ident(ref binding_mode, ident, ref sub) => {
3686 match self.resolver.get_resolution(p.id).map(|d| d.base_def()) {
3687 // `None` can occur in body-less function signatures
3688 def @ None | def @ Some(Def::Local(_)) => {
3689 let canonical_id = match def {
3690 Some(Def::Local(id)) => id,
3693 let hir_id = self.lower_node_id(canonical_id).hir_id;
3694 hir::PatKind::Binding(
3695 self.lower_binding_mode(binding_mode),
3699 sub.as_ref().map(|x| self.lower_pat(x)),
3702 Some(def) => hir::PatKind::Path(hir::QPath::Resolved(
3707 segments: hir_vec![hir::PathSegment::from_ident(ident)],
3712 PatKind::Lit(ref e) => hir::PatKind::Lit(P(self.lower_expr(e))),
3713 PatKind::TupleStruct(ref path, ref pats, ddpos) => {
3714 let qpath = self.lower_qpath(
3718 ParamMode::Optional,
3719 ImplTraitContext::disallowed(),
3721 hir::PatKind::TupleStruct(
3723 pats.iter().map(|x| self.lower_pat(x)).collect(),
3727 PatKind::Path(ref qself, ref path) => {
3728 let qpath = self.lower_qpath(
3732 ParamMode::Optional,
3733 ImplTraitContext::disallowed(),
3735 hir::PatKind::Path(qpath)
3737 PatKind::Struct(ref path, ref fields, etc) => {
3738 let qpath = self.lower_qpath(
3742 ParamMode::Optional,
3743 ImplTraitContext::disallowed(),
3749 let LoweredNodeId { node_id, hir_id } = self.next_id();
3753 node: hir::FieldPat {
3756 ident: f.node.ident,
3757 pat: self.lower_pat(&f.node.pat),
3758 is_shorthand: f.node.is_shorthand,
3763 hir::PatKind::Struct(qpath, fs, etc)
3765 PatKind::Tuple(ref elts, ddpos) => {
3766 hir::PatKind::Tuple(elts.iter().map(|x| self.lower_pat(x)).collect(), ddpos)
3768 PatKind::Box(ref inner) => hir::PatKind::Box(self.lower_pat(inner)),
3769 PatKind::Ref(ref inner, mutbl) => {
3770 hir::PatKind::Ref(self.lower_pat(inner), self.lower_mutability(mutbl))
3772 PatKind::Range(ref e1, ref e2, Spanned { node: ref end, .. }) => hir::PatKind::Range(
3773 P(self.lower_expr(e1)),
3774 P(self.lower_expr(e2)),
3775 self.lower_range_end(end),
3777 PatKind::Slice(ref before, ref slice, ref after) => hir::PatKind::Slice(
3778 before.iter().map(|x| self.lower_pat(x)).collect(),
3779 slice.as_ref().map(|x| self.lower_pat(x)),
3780 after.iter().map(|x| self.lower_pat(x)).collect(),
3782 PatKind::Paren(ref inner) => return self.lower_pat(inner),
3783 PatKind::Mac(_) => panic!("Shouldn't exist here"),
3786 let LoweredNodeId { node_id, hir_id } = self.lower_node_id(p.id);
3795 fn lower_range_end(&mut self, e: &RangeEnd) -> hir::RangeEnd {
3797 RangeEnd::Included(_) => hir::RangeEnd::Included,
3798 RangeEnd::Excluded => hir::RangeEnd::Excluded,
3802 fn lower_anon_const(&mut self, c: &AnonConst) -> hir::AnonConst {
3803 self.with_new_scopes(|this| {
3804 let LoweredNodeId { node_id: _, hir_id } = this.lower_node_id(c.id);
3807 body: this.lower_body(None, |this| this.lower_expr(&c.value)),
3812 fn lower_expr(&mut self, e: &Expr) -> hir::Expr {
3813 let kind = match e.node {
3814 ExprKind::Box(ref inner) => hir::ExprKind::Box(P(self.lower_expr(inner))),
3815 ExprKind::ObsoleteInPlace(..) => {
3816 self.sess.abort_if_errors();
3817 span_bug!(e.span, "encountered ObsoleteInPlace expr during lowering");
3819 ExprKind::Array(ref exprs) => {
3820 hir::ExprKind::Array(exprs.iter().map(|x| self.lower_expr(x)).collect())
3822 ExprKind::Repeat(ref expr, ref count) => {
3823 let expr = P(self.lower_expr(expr));
3824 let count = self.lower_anon_const(count);
3825 hir::ExprKind::Repeat(expr, count)
3827 ExprKind::Tup(ref elts) => {
3828 hir::ExprKind::Tup(elts.iter().map(|x| self.lower_expr(x)).collect())
3830 ExprKind::Call(ref f, ref args) => {
3831 let f = P(self.lower_expr(f));
3832 hir::ExprKind::Call(f, args.iter().map(|x| self.lower_expr(x)).collect())
3834 ExprKind::MethodCall(ref seg, ref args) => {
3835 let hir_seg = P(self.lower_path_segment(
3838 ParamMode::Optional,
3840 ParenthesizedGenericArgs::Err,
3841 ImplTraitContext::disallowed(),
3844 let args = args.iter().map(|x| self.lower_expr(x)).collect();
3845 hir::ExprKind::MethodCall(hir_seg, seg.ident.span, args)
3847 ExprKind::Binary(binop, ref lhs, ref rhs) => {
3848 let binop = self.lower_binop(binop);
3849 let lhs = P(self.lower_expr(lhs));
3850 let rhs = P(self.lower_expr(rhs));
3851 hir::ExprKind::Binary(binop, lhs, rhs)
3853 ExprKind::Unary(op, ref ohs) => {
3854 let op = self.lower_unop(op);
3855 let ohs = P(self.lower_expr(ohs));
3856 hir::ExprKind::Unary(op, ohs)
3858 ExprKind::Lit(ref l) => hir::ExprKind::Lit((*l).clone()),
3859 ExprKind::Cast(ref expr, ref ty) => {
3860 let expr = P(self.lower_expr(expr));
3861 hir::ExprKind::Cast(expr, self.lower_ty(ty, ImplTraitContext::disallowed()))
3863 ExprKind::Type(ref expr, ref ty) => {
3864 let expr = P(self.lower_expr(expr));
3865 hir::ExprKind::Type(expr, self.lower_ty(ty, ImplTraitContext::disallowed()))
3867 ExprKind::AddrOf(m, ref ohs) => {
3868 let m = self.lower_mutability(m);
3869 let ohs = P(self.lower_expr(ohs));
3870 hir::ExprKind::AddrOf(m, ohs)
3872 // More complicated than you might expect because the else branch
3873 // might be `if let`.
3874 ExprKind::If(ref cond, ref blk, ref else_opt) => {
3875 let else_opt = else_opt.as_ref().map(|els| {
3877 ExprKind::IfLet(..) => {
3878 // Wrap the `if let` expr in a block.
3879 let span = els.span;
3880 let els = P(self.lower_expr(els));
3881 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
3882 let blk = P(hir::Block {
3886 rules: hir::DefaultBlock,
3888 targeted_by_break: false,
3890 P(self.expr_block(blk, ThinVec::new()))
3892 _ => P(self.lower_expr(els)),
3896 let then_blk = self.lower_block(blk, false);
3897 let then_expr = self.expr_block(then_blk, ThinVec::new());
3899 hir::ExprKind::If(P(self.lower_expr(cond)), P(then_expr), else_opt)
3901 ExprKind::While(ref cond, ref body, opt_label) => self.with_loop_scope(e.id, |this| {
3902 hir::ExprKind::While(
3903 this.with_loop_condition_scope(|this| P(this.lower_expr(cond))),
3904 this.lower_block(body, false),
3905 this.lower_label(opt_label),
3908 ExprKind::Loop(ref body, opt_label) => self.with_loop_scope(e.id, |this| {
3909 hir::ExprKind::Loop(
3910 this.lower_block(body, false),
3911 this.lower_label(opt_label),
3912 hir::LoopSource::Loop,
3915 ExprKind::TryBlock(ref body) => {
3916 self.with_catch_scope(body.id, |this| {
3917 let unstable_span = this.mark_span_with_reason(
3918 CompilerDesugaringKind::TryBlock,
3921 Symbol::intern("try_trait"),
3924 let mut block = this.lower_block(body, true).into_inner();
3925 let tail = block.expr.take().map_or_else(
3927 let LoweredNodeId { node_id: _, hir_id } = this.next_id();
3928 let span = this.sess.source_map().end_point(unstable_span);
3931 node: hir::ExprKind::Tup(hir_vec![]),
3932 attrs: ThinVec::new(),
3936 |x: P<hir::Expr>| x.into_inner(),
3938 block.expr = Some(this.wrap_in_try_constructor(
3939 "from_ok", tail, unstable_span));
3940 hir::ExprKind::Block(P(block), None)
3943 ExprKind::Match(ref expr, ref arms) => hir::ExprKind::Match(
3944 P(self.lower_expr(expr)),
3945 arms.iter().map(|x| self.lower_arm(x)).collect(),
3946 hir::MatchSource::Normal,
3948 ExprKind::Async(capture_clause, closure_node_id, ref block) => {
3949 self.make_async_expr(capture_clause, closure_node_id, None, |this| {
3950 this.with_new_scopes(|this| {
3951 let block = this.lower_block(block, false);
3952 this.expr_block(block, ThinVec::new())
3957 capture_clause, asyncness, movability, ref decl, ref body, fn_decl_span
3959 if let IsAsync::Async { closure_id, .. } = asyncness {
3960 let outer_decl = FnDecl {
3961 inputs: decl.inputs.clone(),
3962 output: FunctionRetTy::Default(fn_decl_span),
3965 // We need to lower the declaration outside the new scope, because we
3966 // have to conserve the state of being inside a loop condition for the
3967 // closure argument types.
3968 let fn_decl = self.lower_fn_decl(&outer_decl, None, false, None);
3970 self.with_new_scopes(|this| {
3971 // FIXME(cramertj): allow `async` non-`move` closures with arguments.
3972 if capture_clause == CaptureBy::Ref &&
3973 !decl.inputs.is_empty()
3979 "`async` non-`move` closures with arguments \
3980 are not currently supported",
3982 .help("consider using `let` statements to manually capture \
3983 variables by reference before entering an \
3984 `async move` closure")
3988 // Transform `async |x: u8| -> X { ... }` into
3989 // `|x: u8| future_from_generator(|| -> X { ... })`.
3990 let body_id = this.lower_body(Some(&outer_decl), |this| {
3991 let async_ret_ty = if let FunctionRetTy::Ty(ty) = &decl.output {
3994 let async_body = this.make_async_expr(
3995 capture_clause, closure_id, async_ret_ty,
3997 this.with_new_scopes(|this| this.lower_expr(body))
3999 this.expr(fn_decl_span, async_body, ThinVec::new())
4001 hir::ExprKind::Closure(
4002 this.lower_capture_clause(capture_clause),
4010 // Lower outside new scope to preserve `is_in_loop_condition`.
4011 let fn_decl = self.lower_fn_decl(decl, None, false, None);
4013 self.with_new_scopes(|this| {
4014 let mut is_generator = false;
4015 let body_id = this.lower_body(Some(decl), |this| {
4016 let e = this.lower_expr(body);
4017 is_generator = this.is_generator;
4020 let generator_option = if is_generator {
4021 if !decl.inputs.is_empty() {
4026 "generators cannot have explicit arguments"
4028 this.sess.abort_if_errors();
4030 Some(match movability {
4031 Movability::Movable => hir::GeneratorMovability::Movable,
4032 Movability::Static => hir::GeneratorMovability::Static,
4035 if movability == Movability::Static {
4040 "closures cannot be static"
4045 hir::ExprKind::Closure(
4046 this.lower_capture_clause(capture_clause),
4055 ExprKind::Block(ref blk, opt_label) => {
4056 hir::ExprKind::Block(self.lower_block(blk,
4057 opt_label.is_some()),
4058 self.lower_label(opt_label))
4060 ExprKind::Assign(ref el, ref er) => {
4061 hir::ExprKind::Assign(P(self.lower_expr(el)), P(self.lower_expr(er)))
4063 ExprKind::AssignOp(op, ref el, ref er) => hir::ExprKind::AssignOp(
4064 self.lower_binop(op),
4065 P(self.lower_expr(el)),
4066 P(self.lower_expr(er)),
4068 ExprKind::Field(ref el, ident) => hir::ExprKind::Field(P(self.lower_expr(el)), ident),
4069 ExprKind::Index(ref el, ref er) => {
4070 hir::ExprKind::Index(P(self.lower_expr(el)), P(self.lower_expr(er)))
4072 // Desugar `<start>..=<end>` into `std::ops::RangeInclusive::new(<start>, <end>)`.
4073 ExprKind::Range(Some(ref e1), Some(ref e2), RangeLimits::Closed) => {
4074 let id = self.next_id();
4075 let e1 = self.lower_expr(e1);
4076 let e2 = self.lower_expr(e2);
4077 let ty_path = P(self.std_path(e.span, &["ops", "RangeInclusive"], None, false));
4078 let ty = P(self.ty_path(id, e.span, hir::QPath::Resolved(None, ty_path)));
4079 let new_seg = P(hir::PathSegment::from_ident(Ident::from_str("new")));
4080 let new_path = hir::QPath::TypeRelative(ty, new_seg);
4081 let new = P(self.expr(e.span, hir::ExprKind::Path(new_path), ThinVec::new()));
4082 hir::ExprKind::Call(new, hir_vec![e1, e2])
4084 ExprKind::Range(ref e1, ref e2, lims) => {
4085 use syntax::ast::RangeLimits::*;
4087 let path = match (e1, e2, lims) {
4088 (&None, &None, HalfOpen) => "RangeFull",
4089 (&Some(..), &None, HalfOpen) => "RangeFrom",
4090 (&None, &Some(..), HalfOpen) => "RangeTo",
4091 (&Some(..), &Some(..), HalfOpen) => "Range",
4092 (&None, &Some(..), Closed) => "RangeToInclusive",
4093 (&Some(..), &Some(..), Closed) => unreachable!(),
4094 (_, &None, Closed) => self.diagnostic()
4095 .span_fatal(e.span, "inclusive range with no end")
4099 let fields = e1.iter()
4100 .map(|e| ("start", e))
4101 .chain(e2.iter().map(|e| ("end", e)))
4103 let expr = P(self.lower_expr(&e));
4104 let ident = Ident::new(Symbol::intern(s), e.span);
4105 self.field(ident, expr, e.span)
4107 .collect::<P<[hir::Field]>>();
4109 let is_unit = fields.is_empty();
4110 let struct_path = ["ops", path];
4111 let struct_path = self.std_path(e.span, &struct_path, None, is_unit);
4112 let struct_path = hir::QPath::Resolved(None, P(struct_path));
4114 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(e.id);
4119 hir::ExprKind::Path(struct_path)
4121 hir::ExprKind::Struct(P(struct_path), fields, None)
4124 attrs: e.attrs.clone(),
4127 ExprKind::Path(ref qself, ref path) => {
4128 let qpath = self.lower_qpath(
4132 ParamMode::Optional,
4133 ImplTraitContext::disallowed(),
4135 hir::ExprKind::Path(qpath)
4137 ExprKind::Break(opt_label, ref opt_expr) => {
4138 let destination = if self.is_in_loop_condition && opt_label.is_none() {
4141 target_id: Err(hir::LoopIdError::UnlabeledCfInWhileCondition).into(),
4144 self.lower_loop_destination(opt_label.map(|label| (e.id, label)))
4146 hir::ExprKind::Break(
4148 opt_expr.as_ref().map(|x| P(self.lower_expr(x))),
4151 ExprKind::Continue(opt_label) => {
4152 hir::ExprKind::Continue(if self.is_in_loop_condition && opt_label.is_none() {
4155 target_id: Err(hir::LoopIdError::UnlabeledCfInWhileCondition).into(),
4158 self.lower_loop_destination(opt_label.map(|label| (e.id, label)))
4161 ExprKind::Ret(ref e) => hir::ExprKind::Ret(e.as_ref().map(|x| P(self.lower_expr(x)))),
4162 ExprKind::InlineAsm(ref asm) => {
4163 let hir_asm = hir::InlineAsm {
4164 inputs: asm.inputs.iter().map(|&(ref c, _)| c.clone()).collect(),
4165 outputs: asm.outputs
4167 .map(|out| hir::InlineAsmOutput {
4168 constraint: out.constraint.clone(),
4170 is_indirect: out.is_indirect,
4171 span: out.expr.span,
4174 asm: asm.asm.clone(),
4175 asm_str_style: asm.asm_str_style,
4176 clobbers: asm.clobbers.clone().into(),
4177 volatile: asm.volatile,
4178 alignstack: asm.alignstack,
4179 dialect: asm.dialect,
4182 let outputs = asm.outputs
4184 .map(|out| self.lower_expr(&out.expr))
4186 let inputs = asm.inputs
4188 .map(|&(_, ref input)| self.lower_expr(input))
4190 hir::ExprKind::InlineAsm(P(hir_asm), outputs, inputs)
4192 ExprKind::Struct(ref path, ref fields, ref maybe_expr) => hir::ExprKind::Struct(
4197 ParamMode::Optional,
4198 ImplTraitContext::disallowed(),
4200 fields.iter().map(|x| self.lower_field(x)).collect(),
4201 maybe_expr.as_ref().map(|x| P(self.lower_expr(x))),
4203 ExprKind::Paren(ref ex) => {
4204 let mut ex = self.lower_expr(ex);
4205 // Include parens in span, but only if it is a super-span.
4206 if e.span.contains(ex.span) {
4209 // Merge attributes into the inner expression.
4210 let mut attrs = e.attrs.clone();
4211 attrs.extend::<Vec<_>>(ex.attrs.into());
4216 ExprKind::Yield(ref opt_expr) => {
4217 self.is_generator = true;
4220 .map(|x| self.lower_expr(x))
4222 self.expr(e.span, hir::ExprKind::Tup(hir_vec![]), ThinVec::new())
4224 hir::ExprKind::Yield(P(expr))
4227 ExprKind::Err => hir::ExprKind::Err,
4229 // Desugar `ExprIfLet`
4230 // from: `if let <pat> = <sub_expr> <body> [<else_opt>]`
4231 ExprKind::IfLet(ref pats, ref sub_expr, ref body, ref else_opt) => {
4234 // match <sub_expr> {
4236 // _ => [<else_opt> | ()]
4239 let mut arms = vec![];
4241 // `<pat> => <body>`
4243 let body = self.lower_block(body, false);
4244 let body_expr = P(self.expr_block(body, ThinVec::new()));
4245 let pats = pats.iter().map(|pat| self.lower_pat(pat)).collect();
4246 arms.push(self.arm(pats, body_expr));
4249 // _ => [<else_opt>|()]
4251 let wildcard_arm: Option<&Expr> = else_opt.as_ref().map(|p| &**p);
4252 let wildcard_pattern = self.pat_wild(e.span);
4253 let body = if let Some(else_expr) = wildcard_arm {
4254 P(self.lower_expr(else_expr))
4256 self.expr_tuple(e.span, hir_vec![])
4258 arms.push(self.arm(hir_vec![wildcard_pattern], body));
4261 let contains_else_clause = else_opt.is_some();
4263 let sub_expr = P(self.lower_expr(sub_expr));
4265 hir::ExprKind::Match(
4268 hir::MatchSource::IfLetDesugar {
4269 contains_else_clause,
4274 // Desugar `ExprWhileLet`
4275 // from: `[opt_ident]: while let <pat> = <sub_expr> <body>`
4276 ExprKind::WhileLet(ref pats, ref sub_expr, ref body, opt_label) => {
4279 // [opt_ident]: loop {
4280 // match <sub_expr> {
4286 // Note that the block AND the condition are evaluated in the loop scope.
4287 // This is done to allow `break` from inside the condition of the loop.
4288 let (body, break_expr, sub_expr) = self.with_loop_scope(e.id, |this| {
4290 this.lower_block(body, false),
4291 this.expr_break(e.span, ThinVec::new()),
4292 this.with_loop_condition_scope(|this| P(this.lower_expr(sub_expr))),
4296 // `<pat> => <body>`
4298 let body_expr = P(self.expr_block(body, ThinVec::new()));
4299 let pats = pats.iter().map(|pat| self.lower_pat(pat)).collect();
4300 self.arm(pats, body_expr)
4305 let pat_under = self.pat_wild(e.span);
4306 self.arm(hir_vec![pat_under], break_expr)
4309 // `match <sub_expr> { ... }`
4310 let arms = hir_vec![pat_arm, break_arm];
4311 let match_expr = self.expr(
4313 hir::ExprKind::Match(sub_expr, arms, hir::MatchSource::WhileLetDesugar),
4317 // `[opt_ident]: loop { ... }`
4318 let loop_block = P(self.block_expr(P(match_expr)));
4319 let loop_expr = hir::ExprKind::Loop(
4321 self.lower_label(opt_label),
4322 hir::LoopSource::WhileLet,
4324 // Add attributes to the outer returned expr node.
4328 // Desugar `ExprForLoop`
4329 // from: `[opt_ident]: for <pat> in <head> <body>`
4330 ExprKind::ForLoop(ref pat, ref head, ref body, opt_label) => {
4334 // let result = match ::std::iter::IntoIterator::into_iter(<head>) {
4336 // [opt_ident]: loop {
4338 // match ::std::iter::Iterator::next(&mut iter) {
4339 // ::std::option::Option::Some(val) => __next = val,
4340 // ::std::option::Option::None => break
4342 // let <pat> = __next;
4343 // StmtKind::Expr(<body>);
4351 let head = self.lower_expr(head);
4352 let head_sp = head.span;
4353 let desugared_span = self.mark_span_with_reason(
4354 CompilerDesugaringKind::ForLoop,
4359 let iter = self.str_to_ident("iter");
4361 let next_ident = self.str_to_ident("__next");
4362 let next_pat = self.pat_ident_binding_mode(
4365 hir::BindingAnnotation::Mutable,
4368 // `::std::option::Option::Some(val) => next = val`
4370 let val_ident = self.str_to_ident("val");
4371 let val_pat = self.pat_ident(pat.span, val_ident);
4372 let val_expr = P(self.expr_ident(pat.span, val_ident, val_pat.id));
4373 let next_expr = P(self.expr_ident(pat.span, next_ident, next_pat.id));
4374 let assign = P(self.expr(
4376 hir::ExprKind::Assign(next_expr, val_expr),
4379 let some_pat = self.pat_some(pat.span, val_pat);
4380 self.arm(hir_vec![some_pat], assign)
4383 // `::std::option::Option::None => break`
4386 self.with_loop_scope(e.id, |this| this.expr_break(e.span, ThinVec::new()));
4387 let pat = self.pat_none(e.span);
4388 self.arm(hir_vec![pat], break_expr)
4392 let iter_pat = self.pat_ident_binding_mode(
4395 hir::BindingAnnotation::Mutable
4398 // `match ::std::iter::Iterator::next(&mut iter) { ... }`
4400 let iter = P(self.expr_ident(head_sp, iter, iter_pat.id));
4401 let ref_mut_iter = self.expr_mut_addr_of(head_sp, iter);
4402 let next_path = &["iter", "Iterator", "next"];
4403 let next_path = P(self.expr_std_path(head_sp, next_path, None, ThinVec::new()));
4404 let next_expr = P(self.expr_call(head_sp, next_path, hir_vec![ref_mut_iter]));
4405 let arms = hir_vec![pat_arm, break_arm];
4409 hir::ExprKind::Match(
4412 hir::MatchSource::ForLoopDesugar
4417 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
4418 let match_stmt = hir::Stmt {
4420 node: hir::StmtKind::Expr(match_expr),
4424 let next_expr = P(self.expr_ident(head_sp, next_ident, next_pat.id));
4427 let next_let = self.stmt_let_pat(
4431 hir::LocalSource::ForLoopDesugar,
4434 // `let <pat> = __next`
4435 let pat = self.lower_pat(pat);
4436 let pat_let = self.stmt_let_pat(
4440 hir::LocalSource::ForLoopDesugar,
4443 let body_block = self.with_loop_scope(e.id, |this| this.lower_block(body, false));
4444 let body_expr = P(self.expr_block(body_block, ThinVec::new()));
4445 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
4446 let body_stmt = hir::Stmt {
4448 node: hir::StmtKind::Expr(body_expr),
4452 let loop_block = P(self.block_all(
4454 hir_vec![next_let, match_stmt, pat_let, body_stmt],
4458 // `[opt_ident]: loop { ... }`
4459 let loop_expr = hir::ExprKind::Loop(
4461 self.lower_label(opt_label),
4462 hir::LoopSource::ForLoop,
4464 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(e.id);
4465 let loop_expr = P(hir::Expr {
4469 attrs: ThinVec::new(),
4472 // `mut iter => { ... }`
4473 let iter_arm = self.arm(hir_vec![iter_pat], loop_expr);
4475 // `match ::std::iter::IntoIterator::into_iter(<head>) { ... }`
4476 let into_iter_expr = {
4477 let into_iter_path = &["iter", "IntoIterator", "into_iter"];
4478 let into_iter = P(self.expr_std_path(
4479 head_sp, into_iter_path, None, ThinVec::new()));
4480 P(self.expr_call(head_sp, into_iter, hir_vec![head]))
4483 let match_expr = P(self.expr_match(
4487 hir::MatchSource::ForLoopDesugar,
4490 // `{ let _result = ...; _result }`
4491 // Underscore prevents an `unused_variables` lint if the head diverges.
4492 let result_ident = self.str_to_ident("_result");
4493 let (let_stmt, let_stmt_binding) =
4494 self.stmt_let(e.span, false, result_ident, match_expr);
4496 let result = P(self.expr_ident(e.span, result_ident, let_stmt_binding));
4497 let block = P(self.block_all(e.span, hir_vec![let_stmt], Some(result)));
4498 // Add the attributes to the outer returned expr node.
4499 return self.expr_block(block, e.attrs.clone());
4502 // Desugar `ExprKind::Try`
4504 ExprKind::Try(ref sub_expr) => {
4507 // match Try::into_result(<expr>) {
4508 // Ok(val) => #[allow(unreachable_code)] val,
4509 // Err(err) => #[allow(unreachable_code)]
4510 // // If there is an enclosing `catch {...}`
4511 // break 'catch_target Try::from_error(From::from(err)),
4513 // return Try::from_error(From::from(err)),
4516 let unstable_span = self.mark_span_with_reason(
4517 CompilerDesugaringKind::QuestionMark,
4520 Symbol::intern("try_trait")
4524 // `Try::into_result(<expr>)`
4527 let sub_expr = self.lower_expr(sub_expr);
4529 let path = &["ops", "Try", "into_result"];
4530 let path = P(self.expr_std_path(
4531 unstable_span, path, None, ThinVec::new()));
4532 P(self.expr_call(e.span, path, hir_vec![sub_expr]))
4535 // `#[allow(unreachable_code)]`
4537 // `allow(unreachable_code)`
4539 let allow_ident = Ident::from_str("allow").with_span_pos(e.span);
4540 let uc_ident = Ident::from_str("unreachable_code").with_span_pos(e.span);
4541 let uc_nested = attr::mk_nested_word_item(uc_ident);
4542 attr::mk_list_item(e.span, allow_ident, vec![uc_nested])
4544 attr::mk_spanned_attr_outer(e.span, attr::mk_attr_id(), allow)
4546 let attrs = vec![attr];
4548 // `Ok(val) => #[allow(unreachable_code)] val,`
4550 let val_ident = self.str_to_ident("val");
4551 let val_pat = self.pat_ident(e.span, val_ident);
4552 let val_expr = P(self.expr_ident_with_attrs(
4556 ThinVec::from(attrs.clone()),
4558 let ok_pat = self.pat_ok(e.span, val_pat);
4560 self.arm(hir_vec![ok_pat], val_expr)
4563 // `Err(err) => #[allow(unreachable_code)]
4564 // return Try::from_error(From::from(err)),`
4566 let err_ident = self.str_to_ident("err");
4567 let err_local = self.pat_ident(e.span, err_ident);
4569 let path = &["convert", "From", "from"];
4570 let from = P(self.expr_std_path(
4571 e.span, path, None, ThinVec::new()));
4572 let err_expr = self.expr_ident(e.span, err_ident, err_local.id);
4574 self.expr_call(e.span, from, hir_vec![err_expr])
4577 self.wrap_in_try_constructor("from_error", from_expr, unstable_span);
4578 let thin_attrs = ThinVec::from(attrs);
4579 let catch_scope = self.catch_scopes.last().map(|x| *x);
4580 let ret_expr = if let Some(catch_node) = catch_scope {
4583 hir::ExprKind::Break(
4586 target_id: Ok(catch_node),
4588 Some(from_err_expr),
4593 P(self.expr(e.span, hir::ExprKind::Ret(Some(from_err_expr)), thin_attrs))
4596 let err_pat = self.pat_err(e.span, err_local);
4597 self.arm(hir_vec![err_pat], ret_expr)
4600 hir::ExprKind::Match(
4602 hir_vec![err_arm, ok_arm],
4603 hir::MatchSource::TryDesugar,
4607 ExprKind::Mac(_) => panic!("Shouldn't exist here"),
4610 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(e.id);
4616 attrs: e.attrs.clone(),
4620 fn lower_stmt(&mut self, s: &Stmt) -> SmallVec<[hir::Stmt; 1]> {
4621 smallvec![match s.node {
4622 StmtKind::Local(ref l) => {
4623 let (l, item_ids) = self.lower_local(l);
4624 let mut ids: SmallVec<[hir::Stmt; 1]> = item_ids
4627 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
4631 node: hir::StmtKind::Item(item_id),
4637 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(s.id);
4641 node: hir::StmtKind::Local(P(l)),
4647 StmtKind::Item(ref it) => {
4648 // Can only use the ID once.
4649 let mut id = Some(s.id);
4650 return self.lower_item_id(it)
4653 let LoweredNodeId { node_id: _, hir_id } = id.take()
4654 .map(|id| self.lower_node_id(id))
4655 .unwrap_or_else(|| self.next_id());
4659 node: hir::StmtKind::Item(item_id),
4665 StmtKind::Expr(ref e) => {
4666 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(s.id);
4670 node: hir::StmtKind::Expr(P(self.lower_expr(e))),
4674 StmtKind::Semi(ref e) => {
4675 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(s.id);
4679 node: hir::StmtKind::Semi(P(self.lower_expr(e))),
4683 StmtKind::Mac(..) => panic!("Shouldn't exist here"),
4687 fn lower_capture_clause(&mut self, c: CaptureBy) -> hir::CaptureClause {
4689 CaptureBy::Value => hir::CaptureByValue,
4690 CaptureBy::Ref => hir::CaptureByRef,
4694 /// If an `explicit_owner` is given, this method allocates the `HirId` in
4695 /// the address space of that item instead of the item currently being
4696 /// lowered. This can happen during `lower_impl_item_ref()` where we need to
4697 /// lower a `Visibility` value although we haven't lowered the owning
4698 /// `ImplItem` in question yet.
4699 fn lower_visibility(
4702 explicit_owner: Option<NodeId>,
4703 ) -> hir::Visibility {
4704 let node = match v.node {
4705 VisibilityKind::Public => hir::VisibilityKind::Public,
4706 VisibilityKind::Crate(sugar) => hir::VisibilityKind::Crate(sugar),
4707 VisibilityKind::Restricted { ref path, id } => {
4708 debug!("lower_visibility: restricted path id = {:?}", id);
4709 let lowered_id = if let Some(owner) = explicit_owner {
4710 self.lower_node_id_with_owner(id, owner)
4712 self.lower_node_id(id)
4714 let def = self.expect_full_def(id);
4715 hir::VisibilityKind::Restricted {
4716 path: P(self.lower_path_extra(
4719 ParamMode::Explicit,
4722 hir_id: lowered_id.hir_id,
4725 VisibilityKind::Inherited => hir::VisibilityKind::Inherited,
4727 respan(v.span, node)
4730 fn lower_defaultness(&self, d: Defaultness, has_value: bool) -> hir::Defaultness {
4732 Defaultness::Default => hir::Defaultness::Default {
4733 has_value: has_value,
4735 Defaultness::Final => {
4737 hir::Defaultness::Final
4742 fn lower_block_check_mode(&mut self, b: &BlockCheckMode) -> hir::BlockCheckMode {
4744 BlockCheckMode::Default => hir::DefaultBlock,
4745 BlockCheckMode::Unsafe(u) => hir::UnsafeBlock(self.lower_unsafe_source(u)),
4749 fn lower_binding_mode(&mut self, b: &BindingMode) -> hir::BindingAnnotation {
4751 BindingMode::ByValue(Mutability::Immutable) => hir::BindingAnnotation::Unannotated,
4752 BindingMode::ByRef(Mutability::Immutable) => hir::BindingAnnotation::Ref,
4753 BindingMode::ByValue(Mutability::Mutable) => hir::BindingAnnotation::Mutable,
4754 BindingMode::ByRef(Mutability::Mutable) => hir::BindingAnnotation::RefMut,
4758 fn lower_unsafe_source(&mut self, u: UnsafeSource) -> hir::UnsafeSource {
4760 CompilerGenerated => hir::CompilerGenerated,
4761 UserProvided => hir::UserProvided,
4765 fn lower_impl_polarity(&mut self, i: ImplPolarity) -> hir::ImplPolarity {
4767 ImplPolarity::Positive => hir::ImplPolarity::Positive,
4768 ImplPolarity::Negative => hir::ImplPolarity::Negative,
4772 fn lower_trait_bound_modifier(&mut self, f: TraitBoundModifier) -> hir::TraitBoundModifier {
4774 TraitBoundModifier::None => hir::TraitBoundModifier::None,
4775 TraitBoundModifier::Maybe => hir::TraitBoundModifier::Maybe,
4779 // Helper methods for building HIR.
4781 fn arm(&mut self, pats: hir::HirVec<P<hir::Pat>>, expr: P<hir::Expr>) -> hir::Arm {
4790 fn field(&mut self, ident: Ident, expr: P<hir::Expr>, span: Span) -> hir::Field {
4791 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
4798 is_shorthand: false,
4802 fn expr_break(&mut self, span: Span, attrs: ThinVec<Attribute>) -> P<hir::Expr> {
4803 let expr_break = hir::ExprKind::Break(self.lower_loop_destination(None), None);
4804 P(self.expr(span, expr_break, attrs))
4811 args: hir::HirVec<hir::Expr>,
4813 self.expr(span, hir::ExprKind::Call(e, args), ThinVec::new())
4816 fn expr_ident(&mut self, span: Span, ident: Ident, binding: NodeId) -> hir::Expr {
4817 self.expr_ident_with_attrs(span, ident, binding, ThinVec::new())
4820 fn expr_ident_with_attrs(
4825 attrs: ThinVec<Attribute>,
4827 let expr_path = hir::ExprKind::Path(hir::QPath::Resolved(
4831 def: Def::Local(binding),
4832 segments: hir_vec![hir::PathSegment::from_ident(ident)],
4836 self.expr(span, expr_path, attrs)
4839 fn expr_mut_addr_of(&mut self, span: Span, e: P<hir::Expr>) -> hir::Expr {
4840 self.expr(span, hir::ExprKind::AddrOf(hir::MutMutable, e), ThinVec::new())
4846 components: &[&str],
4847 params: Option<P<hir::GenericArgs>>,
4848 attrs: ThinVec<Attribute>,
4850 let path = self.std_path(span, components, params, true);
4853 hir::ExprKind::Path(hir::QPath::Resolved(None, P(path))),
4862 arms: hir::HirVec<hir::Arm>,
4863 source: hir::MatchSource,
4865 self.expr(span, hir::ExprKind::Match(arg, arms, source), ThinVec::new())
4868 fn expr_block(&mut self, b: P<hir::Block>, attrs: ThinVec<Attribute>) -> hir::Expr {
4869 self.expr(b.span, hir::ExprKind::Block(b, None), attrs)
4872 fn expr_tuple(&mut self, sp: Span, exprs: hir::HirVec<hir::Expr>) -> P<hir::Expr> {
4873 P(self.expr(sp, hir::ExprKind::Tup(exprs), ThinVec::new()))
4876 fn expr(&mut self, span: Span, node: hir::ExprKind, attrs: ThinVec<Attribute>) -> hir::Expr {
4877 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
4889 ex: Option<P<hir::Expr>>,
4891 source: hir::LocalSource,
4893 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
4895 let local = hir::Local {
4901 attrs: ThinVec::new(),
4905 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
4908 node: hir::StmtKind::Local(P(local)),
4919 ) -> (hir::Stmt, NodeId) {
4920 let pat = if mutbl {
4921 self.pat_ident_binding_mode(sp, ident, hir::BindingAnnotation::Mutable)
4923 self.pat_ident(sp, ident)
4925 let pat_id = pat.id;
4927 self.stmt_let_pat(sp, Some(ex), pat, hir::LocalSource::Normal),
4932 fn block_expr(&mut self, expr: P<hir::Expr>) -> hir::Block {
4933 self.block_all(expr.span, hir::HirVec::new(), Some(expr))
4939 stmts: hir::HirVec<hir::Stmt>,
4940 expr: Option<P<hir::Expr>>,
4942 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
4948 rules: hir::DefaultBlock,
4950 targeted_by_break: false,
4954 fn pat_ok(&mut self, span: Span, pat: P<hir::Pat>) -> P<hir::Pat> {
4955 self.pat_std_enum(span, &["result", "Result", "Ok"], hir_vec![pat])
4958 fn pat_err(&mut self, span: Span, pat: P<hir::Pat>) -> P<hir::Pat> {
4959 self.pat_std_enum(span, &["result", "Result", "Err"], hir_vec![pat])
4962 fn pat_some(&mut self, span: Span, pat: P<hir::Pat>) -> P<hir::Pat> {
4963 self.pat_std_enum(span, &["option", "Option", "Some"], hir_vec![pat])
4966 fn pat_none(&mut self, span: Span) -> P<hir::Pat> {
4967 self.pat_std_enum(span, &["option", "Option", "None"], hir_vec![])
4973 components: &[&str],
4974 subpats: hir::HirVec<P<hir::Pat>>,
4976 let path = self.std_path(span, components, None, true);
4977 let qpath = hir::QPath::Resolved(None, P(path));
4978 let pt = if subpats.is_empty() {
4979 hir::PatKind::Path(qpath)
4981 hir::PatKind::TupleStruct(qpath, subpats, None)
4986 fn pat_ident(&mut self, span: Span, ident: Ident) -> P<hir::Pat> {
4987 self.pat_ident_binding_mode(span, ident, hir::BindingAnnotation::Unannotated)
4990 fn pat_ident_binding_mode(
4994 bm: hir::BindingAnnotation,
4996 let LoweredNodeId { node_id, hir_id } = self.next_id();
5001 node: hir::PatKind::Binding(bm, node_id, hir_id, ident.with_span_pos(span), None),
5006 fn pat_wild(&mut self, span: Span) -> P<hir::Pat> {
5007 self.pat(span, hir::PatKind::Wild)
5010 fn pat(&mut self, span: Span, pat: hir::PatKind) -> P<hir::Pat> {
5011 let LoweredNodeId { node_id, hir_id } = self.next_id();
5020 /// Given suffix ["b","c","d"], returns path `::std::b::c::d` when
5021 /// `fld.cx.use_std`, and `::core::b::c::d` otherwise.
5022 /// The path is also resolved according to `is_value`.
5026 components: &[&str],
5027 params: Option<P<hir::GenericArgs>>,
5030 let mut path = self.resolver
5031 .resolve_str_path(span, self.crate_root, components, is_value);
5032 path.segments.last_mut().unwrap().args = params;
5035 for seg in path.segments.iter_mut() {
5036 if let Some(id) = seg.id {
5037 seg.id = Some(self.lower_node_id(id).node_id);
5043 fn ty_path(&mut self, id: LoweredNodeId, span: Span, qpath: hir::QPath) -> hir::Ty {
5045 let node = match qpath {
5046 hir::QPath::Resolved(None, path) => {
5047 // Turn trait object paths into `TyKind::TraitObject` instead.
5049 Def::Trait(_) | Def::TraitAlias(_) => {
5050 let principal = hir::PolyTraitRef {
5051 bound_generic_params: hir::HirVec::new(),
5052 trait_ref: hir::TraitRef {
5053 path: path.and_then(|path| path),
5054 hir_ref_id: id.hir_id,
5059 // The original ID is taken by the `PolyTraitRef`,
5060 // so the `Ty` itself needs a different one.
5061 id = self.next_id();
5062 hir::TyKind::TraitObject(hir_vec![principal], self.elided_dyn_bound(span))
5064 _ => hir::TyKind::Path(hir::QPath::Resolved(None, path)),
5067 _ => hir::TyKind::Path(qpath),
5076 /// Invoked to create the lifetime argument for a type `&T`
5077 /// with no explicit lifetime.
5078 fn elided_ref_lifetime(&mut self, span: Span) -> hir::Lifetime {
5079 match self.anonymous_lifetime_mode {
5080 // Intercept when we are in an impl header and introduce an in-band lifetime.
5081 // Hence `impl Foo for &u32` becomes `impl<'f> Foo for &'f u32` for some fresh
5083 AnonymousLifetimeMode::CreateParameter => {
5084 let fresh_name = self.collect_fresh_in_band_lifetime(span);
5085 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
5089 name: hir::LifetimeName::Param(fresh_name),
5093 AnonymousLifetimeMode::ReportError => self.new_error_lifetime(None, span),
5095 AnonymousLifetimeMode::PassThrough => self.new_implicit_lifetime(span),
5099 /// Report an error on illegal use of `'_` or a `&T` with no explicit lifetime;
5100 /// return a "error lifetime".
5101 fn new_error_lifetime(&mut self, id: Option<NodeId>, span: Span) -> hir::Lifetime {
5102 let (id, msg, label) = match id {
5103 Some(id) => (id, "`'_` cannot be used here", "`'_` is a reserved lifetime name"),
5106 self.next_id().node_id,
5107 "`&` without an explicit lifetime name cannot be used here",
5108 "explicit lifetime name needed here",
5112 let mut err = struct_span_err!(
5119 err.span_label(span, label);
5122 self.new_named_lifetime(id, span, hir::LifetimeName::Error)
5125 /// Invoked to create the lifetime argument(s) for a path like
5126 /// `std::cell::Ref<T>`; note that implicit lifetimes in these
5127 /// sorts of cases are deprecated. This may therefore report a warning or an
5128 /// error, depending on the mode.
5129 fn elided_path_lifetimes(&mut self, span: Span, count: usize) -> P<[hir::Lifetime]> {
5130 match self.anonymous_lifetime_mode {
5131 // N.B., We intentionally ignore the create-parameter mode here
5132 // and instead "pass through" to resolve-lifetimes, which will then
5133 // report an error. This is because we don't want to support
5134 // impl elision for deprecated forms like
5136 // impl Foo for std::cell::Ref<u32> // note lack of '_
5137 AnonymousLifetimeMode::CreateParameter => {}
5139 AnonymousLifetimeMode::ReportError => {
5141 .map(|_| self.new_error_lifetime(None, span))
5145 // This is the normal case.
5146 AnonymousLifetimeMode::PassThrough => {}
5150 .map(|_| self.new_implicit_lifetime(span))
5154 /// Invoked to create the lifetime argument(s) for an elided trait object
5155 /// bound, like the bound in `Box<dyn Debug>`. This method is not invoked
5156 /// when the bound is written, even if it is written with `'_` like in
5157 /// `Box<dyn Debug + '_>`. In those cases, `lower_lifetime` is invoked.
5158 fn elided_dyn_bound(&mut self, span: Span) -> hir::Lifetime {
5159 match self.anonymous_lifetime_mode {
5160 // NB. We intentionally ignore the create-parameter mode here.
5161 // and instead "pass through" to resolve-lifetimes, which will apply
5162 // the object-lifetime-defaulting rules. Elided object lifetime defaults
5163 // do not act like other elided lifetimes. In other words, given this:
5165 // impl Foo for Box<dyn Debug>
5167 // we do not introduce a fresh `'_` to serve as the bound, but instead
5168 // ultimately translate to the equivalent of:
5170 // impl Foo for Box<dyn Debug + 'static>
5172 // `resolve_lifetime` has the code to make that happen.
5173 AnonymousLifetimeMode::CreateParameter => {}
5175 AnonymousLifetimeMode::ReportError => {
5176 // ReportError applies to explicit use of `'_`.
5179 // This is the normal case.
5180 AnonymousLifetimeMode::PassThrough => {}
5183 self.new_implicit_lifetime(span)
5186 fn new_implicit_lifetime(&mut self, span: Span) -> hir::Lifetime {
5187 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
5192 name: hir::LifetimeName::Implicit,
5196 fn maybe_lint_bare_trait(&self, span: Span, id: NodeId, is_global: bool) {
5197 self.sess.buffer_lint_with_diagnostic(
5198 builtin::BARE_TRAIT_OBJECTS,
5201 "trait objects without an explicit `dyn` are deprecated",
5202 builtin::BuiltinLintDiagnostics::BareTraitObject(span, is_global),
5206 fn wrap_in_try_constructor(
5208 method: &'static str,
5210 unstable_span: Span,
5212 let path = &["ops", "Try", method];
5213 let from_err = P(self.expr_std_path(unstable_span, path, None,
5215 P(self.expr_call(e.span, from_err, hir_vec![e]))
5219 fn body_ids(bodies: &BTreeMap<hir::BodyId, hir::Body>) -> Vec<hir::BodyId> {
5220 // Sorting by span ensures that we get things in order within a
5221 // file, and also puts the files in a sensible order.
5222 let mut body_ids: Vec<_> = bodies.keys().cloned().collect();
5223 body_ids.sort_by_key(|b| bodies[b].value.span);