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<hir::HirId>>,
94 modules: BTreeMap<NodeId, hir::ModuleItems>,
98 catch_scopes: Vec<NodeId>,
99 loop_scopes: Vec<NodeId>,
100 is_in_loop_condition: bool,
101 is_in_trait_impl: bool,
103 /// What to do when we encounter either an "anonymous lifetime
104 /// reference". The term "anonymous" is meant to encompass both
105 /// `'_` lifetimes as well as fully elided cases where nothing is
106 /// written at all (e.g., `&T` or `std::cell::Ref<T>`).
107 anonymous_lifetime_mode: AnonymousLifetimeMode,
109 /// Used to create lifetime definitions from in-band lifetime usages.
110 /// e.g., `fn foo(x: &'x u8) -> &'x u8` to `fn foo<'x>(x: &'x u8) -> &'x u8`
111 /// When a named lifetime is encountered in a function or impl header and
112 /// has not been defined
113 /// (i.e., it doesn't appear in the in_scope_lifetimes list), it is added
114 /// to this list. The results of this list are then added to the list of
115 /// lifetime definitions in the corresponding impl or function generics.
116 lifetimes_to_define: Vec<(Span, ParamName)>,
118 /// Whether or not in-band lifetimes are being collected. This is used to
119 /// indicate whether or not we're in a place where new lifetimes will result
120 /// in in-band lifetime definitions, such a function or an impl header,
121 /// including implicit lifetimes from `impl_header_lifetime_elision`.
122 is_collecting_in_band_lifetimes: bool,
124 /// Currently in-scope lifetimes defined in impl headers, fn headers, or HRTB.
125 /// When `is_collectin_in_band_lifetimes` is true, each lifetime is checked
126 /// against this list to see if it is already in-scope, or if a definition
127 /// needs to be created for it.
128 in_scope_lifetimes: Vec<Ident>,
130 current_module: NodeId,
132 type_def_lifetime_params: DefIdMap<usize>,
134 current_hir_id_owner: Vec<(DefIndex, u32)>,
135 item_local_id_counters: NodeMap<u32>,
136 node_id_to_hir_id: IndexVec<NodeId, hir::HirId>,
140 /// Resolve a path generated by the lowerer when expanding `for`, `if let`, etc.
147 /// Obtain the resolution for a `NodeId`.
148 fn get_resolution(&mut self, id: NodeId) -> Option<PathResolution>;
150 /// Obtain the possible resolutions for the given `use` statement.
151 fn get_import(&mut self, id: NodeId) -> PerNS<Option<PathResolution>>;
153 /// We must keep the set of definitions up to date as we add nodes that weren't in the AST.
154 /// This should only return `None` during testing.
155 fn definitions(&mut self) -> &mut Definitions;
157 /// Given suffix `["b", "c", "d"]`, creates a HIR path for `[::crate_root]::b::c::d` and
158 /// resolves it based on `is_value`.
162 crate_root: Option<&str>,
169 enum ImplTraitContext<'a> {
170 /// Treat `impl Trait` as shorthand for a new universal generic parameter.
171 /// Example: `fn foo(x: impl Debug)`, where `impl Debug` is conceptually
172 /// equivalent to a fresh universal parameter like `fn foo<T: Debug>(x: T)`.
174 /// Newly generated parameters should be inserted into the given `Vec`.
175 Universal(&'a mut Vec<hir::GenericParam>),
177 /// Treat `impl Trait` as shorthand for a new existential parameter.
178 /// Example: `fn foo() -> impl Debug`, where `impl Debug` is conceptually
179 /// equivalent to a fresh existential parameter like `existential type T; fn foo() -> T`.
181 /// We optionally store a `DefId` for the parent item here so we can look up necessary
182 /// information later. It is `None` when no information about the context should be stored,
183 /// e.g., for consts and statics.
184 Existential(Option<DefId>),
186 /// `impl Trait` is not accepted in this position.
187 Disallowed(ImplTraitPosition),
190 /// Position in which `impl Trait` is disallowed. Used for error reporting.
191 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
192 enum ImplTraitPosition {
197 impl<'a> ImplTraitContext<'a> {
199 fn disallowed() -> Self {
200 ImplTraitContext::Disallowed(ImplTraitPosition::Other)
203 fn reborrow(&'b mut self) -> ImplTraitContext<'b> {
204 use self::ImplTraitContext::*;
206 Universal(params) => Universal(params),
207 Existential(did) => Existential(*did),
208 Disallowed(pos) => Disallowed(*pos),
215 cstore: &dyn CrateStore,
216 dep_graph: &DepGraph,
218 resolver: &mut dyn Resolver,
220 // We're constructing the HIR here; we don't care what we will
221 // read, since we haven't even constructed the *input* to
223 dep_graph.assert_ignored();
226 crate_root: std_inject::injected_crate_name(),
230 items: BTreeMap::new(),
231 trait_items: BTreeMap::new(),
232 impl_items: BTreeMap::new(),
233 bodies: BTreeMap::new(),
234 trait_impls: BTreeMap::new(),
235 modules: BTreeMap::new(),
236 exported_macros: Vec::new(),
237 catch_scopes: Vec::new(),
238 loop_scopes: Vec::new(),
239 is_in_loop_condition: false,
240 anonymous_lifetime_mode: AnonymousLifetimeMode::PassThrough,
241 type_def_lifetime_params: Default::default(),
242 current_module: CRATE_NODE_ID,
243 current_hir_id_owner: vec![(CRATE_DEF_INDEX, 0)],
244 item_local_id_counters: Default::default(),
245 node_id_to_hir_id: IndexVec::new(),
247 is_in_trait_impl: false,
248 lifetimes_to_define: Vec::new(),
249 is_collecting_in_band_lifetimes: false,
250 in_scope_lifetimes: Vec::new(),
254 #[derive(Copy, Clone, PartialEq)]
256 /// Any path in a type context.
258 /// The `module::Type` in `module::Type::method` in an expression.
263 struct LoweredNodeId {
268 enum ParenthesizedGenericArgs {
274 /// What to do when we encounter an **anonymous** lifetime
275 /// reference. Anonymous lifetime references come in two flavors. You
276 /// have implicit, or fully elided, references to lifetimes, like the
277 /// one in `&T` or `Ref<T>`, and you have `'_` lifetimes, like `&'_ T`
278 /// or `Ref<'_, T>`. These often behave the same, but not always:
280 /// - certain usages of implicit references are deprecated, like
281 /// `Ref<T>`, and we sometimes just give hard errors in those cases
283 /// - for object bounds there is a difference: `Box<dyn Foo>` is not
284 /// the same as `Box<dyn Foo + '_>`.
286 /// We describe the effects of the various modes in terms of three cases:
288 /// - **Modern** -- includes all uses of `'_`, but also the lifetime arg
289 /// of a `&` (e.g., the missing lifetime in something like `&T`)
290 /// - **Dyn Bound** -- if you have something like `Box<dyn Foo>`,
291 /// there is an elided lifetime bound (`Box<dyn Foo + 'X>`). These
292 /// elided bounds follow special rules. Note that this only covers
293 /// cases where *nothing* is written; the `'_` in `Box<dyn Foo +
294 /// '_>` is a case of "modern" elision.
295 /// - **Deprecated** -- this coverse cases like `Ref<T>`, where the lifetime
296 /// parameter to ref is completely elided. `Ref<'_, T>` would be the modern,
297 /// non-deprecated equivalent.
299 /// Currently, the handling of lifetime elision is somewhat spread out
300 /// between HIR lowering and -- as described below -- the
301 /// `resolve_lifetime` module. Often we "fallthrough" to that code by generating
302 /// an "elided" or "underscore" lifetime name. In the future, we probably want to move
303 /// everything into HIR lowering.
304 #[derive(Copy, Clone)]
305 enum AnonymousLifetimeMode {
306 /// For **Modern** cases, create a new anonymous region parameter
307 /// and reference that.
309 /// For **Dyn Bound** cases, pass responsibility to
310 /// `resolve_lifetime` code.
312 /// For **Deprecated** cases, report an error.
315 /// Give a hard error when either `&` or `'_` is written. Used to
316 /// rule out things like `where T: Foo<'_>`. Does not imply an
317 /// error on default object bounds (e.g., `Box<dyn Foo>`).
320 /// Pass responsibility to `resolve_lifetime` code for all cases.
324 struct ImplTraitTypeIdVisitor<'a> { ids: &'a mut SmallVec<[hir::ItemId; 1]> }
326 impl<'a, 'b> Visitor<'a> for ImplTraitTypeIdVisitor<'b> {
327 fn visit_ty(&mut self, ty: &'a Ty) {
333 TyKind::ImplTrait(id, _) => self.ids.push(hir::ItemId { id }),
336 visit::walk_ty(self, ty);
339 fn visit_path_segment(
342 path_segment: &'v PathSegment,
344 if let Some(ref p) = path_segment.args {
345 if let GenericArgs::Parenthesized(_) = **p {
349 visit::walk_path_segment(self, path_span, path_segment)
353 impl<'a> LoweringContext<'a> {
354 fn lower_crate(mut self, c: &Crate) -> hir::Crate {
355 /// Full-crate AST visitor that inserts into a fresh
356 /// `LoweringContext` any information that may be
357 /// needed from arbitrary locations in the crate,
358 /// e.g., the number of lifetime generic parameters
359 /// declared for every type and trait definition.
360 struct MiscCollector<'lcx, 'interner: 'lcx> {
361 lctx: &'lcx mut LoweringContext<'interner>,
364 impl<'lcx, 'interner> Visitor<'lcx> for MiscCollector<'lcx, 'interner> {
365 fn visit_item(&mut self, item: &'lcx Item) {
366 self.lctx.allocate_hir_id_counter(item.id, item);
369 ItemKind::Struct(_, ref generics)
370 | ItemKind::Union(_, ref generics)
371 | ItemKind::Enum(_, ref generics)
372 | ItemKind::Ty(_, ref generics)
373 | ItemKind::Existential(_, ref generics)
374 | ItemKind::Trait(_, _, ref generics, ..) => {
375 let def_id = self.lctx.resolver.definitions().local_def_id(item.id);
379 .filter(|param| match param.kind {
380 ast::GenericParamKind::Lifetime { .. } => true,
384 self.lctx.type_def_lifetime_params.insert(def_id, count);
388 visit::walk_item(self, item);
391 fn visit_trait_item(&mut self, item: &'lcx TraitItem) {
392 self.lctx.allocate_hir_id_counter(item.id, item);
393 visit::walk_trait_item(self, item);
396 fn visit_impl_item(&mut self, item: &'lcx ImplItem) {
397 self.lctx.allocate_hir_id_counter(item.id, item);
398 visit::walk_impl_item(self, item);
402 struct ItemLowerer<'lcx, 'interner: 'lcx> {
403 lctx: &'lcx mut LoweringContext<'interner>,
406 impl<'lcx, 'interner> ItemLowerer<'lcx, 'interner> {
407 fn with_trait_impl_ref<F>(&mut self, trait_impl_ref: &Option<TraitRef>, f: F)
409 F: FnOnce(&mut Self),
411 let old = self.lctx.is_in_trait_impl;
412 self.lctx.is_in_trait_impl = if let &None = trait_impl_ref {
418 self.lctx.is_in_trait_impl = old;
422 impl<'lcx, 'interner> Visitor<'lcx> for ItemLowerer<'lcx, 'interner> {
423 fn visit_mod(&mut self, m: &'lcx Mod, _s: Span, _attrs: &[Attribute], n: NodeId) {
424 self.lctx.modules.insert(n, hir::ModuleItems {
425 items: BTreeSet::new(),
426 trait_items: BTreeSet::new(),
427 impl_items: BTreeSet::new(),
430 let old = self.lctx.current_module;
431 self.lctx.current_module = n;
432 visit::walk_mod(self, m);
433 self.lctx.current_module = old;
436 fn visit_item(&mut self, item: &'lcx Item) {
437 let mut item_lowered = true;
438 self.lctx.with_hir_id_owner(item.id, |lctx| {
439 if let Some(hir_item) = lctx.lower_item(item) {
440 lctx.insert_item(item.id, hir_item);
442 item_lowered = false;
447 let item_generics = match self.lctx.items.get(&item.id).unwrap().node {
448 hir::ItemKind::Impl(_, _, _, ref generics, ..)
449 | hir::ItemKind::Trait(_, _, ref generics, ..) => {
450 generics.params.clone()
455 self.lctx.with_parent_impl_lifetime_defs(&item_generics, |this| {
456 let this = &mut ItemLowerer { lctx: this };
457 if let ItemKind::Impl(.., ref opt_trait_ref, _, _) = item.node {
458 this.with_trait_impl_ref(opt_trait_ref, |this| {
459 visit::walk_item(this, item)
462 visit::walk_item(this, item);
468 fn visit_trait_item(&mut self, item: &'lcx TraitItem) {
469 self.lctx.with_hir_id_owner(item.id, |lctx| {
470 let hir_item = lctx.lower_trait_item(item);
471 let id = hir::TraitItemId { hir_id: hir_item.hir_id };
472 lctx.trait_items.insert(id, hir_item);
473 lctx.modules.get_mut(&lctx.current_module).unwrap().trait_items.insert(id);
476 visit::walk_trait_item(self, item);
479 fn visit_impl_item(&mut self, item: &'lcx ImplItem) {
480 self.lctx.with_hir_id_owner(item.id, |lctx| {
481 let hir_item = lctx.lower_impl_item(item);
482 let id = hir::ImplItemId { hir_id: hir_item.hir_id };
483 lctx.impl_items.insert(id, hir_item);
484 lctx.modules.get_mut(&lctx.current_module).unwrap().impl_items.insert(id);
486 visit::walk_impl_item(self, item);
490 self.lower_node_id(CRATE_NODE_ID);
491 debug_assert!(self.node_id_to_hir_id[CRATE_NODE_ID] == hir::CRATE_HIR_ID);
493 visit::walk_crate(&mut MiscCollector { lctx: &mut self }, c);
494 visit::walk_crate(&mut ItemLowerer { lctx: &mut self }, c);
496 let module = self.lower_mod(&c.module);
497 let attrs = self.lower_attrs(&c.attrs);
498 let body_ids = body_ids(&self.bodies);
502 .init_node_id_to_hir_id_mapping(self.node_id_to_hir_id);
508 exported_macros: hir::HirVec::from(self.exported_macros),
510 trait_items: self.trait_items,
511 impl_items: self.impl_items,
514 trait_impls: self.trait_impls,
515 modules: self.modules,
519 fn insert_item(&mut self, id: NodeId, item: hir::Item) {
520 self.items.insert(id, item);
521 self.modules.get_mut(&self.current_module).unwrap().items.insert(id);
524 fn allocate_hir_id_counter<T: Debug>(&mut self, owner: NodeId, debug: &T) -> LoweredNodeId {
525 if self.item_local_id_counters.insert(owner, 0).is_some() {
527 "Tried to allocate item_local_id_counter for {:?} twice",
531 // Always allocate the first `HirId` for the owner itself.
532 self.lower_node_id_with_owner(owner, owner)
535 fn lower_node_id_generic<F>(&mut self, ast_node_id: NodeId, alloc_hir_id: F) -> LoweredNodeId
537 F: FnOnce(&mut Self) -> hir::HirId,
539 if ast_node_id == DUMMY_NODE_ID {
540 return LoweredNodeId {
541 node_id: DUMMY_NODE_ID,
542 hir_id: hir::DUMMY_HIR_ID,
546 let min_size = ast_node_id.as_usize() + 1;
548 if min_size > self.node_id_to_hir_id.len() {
549 self.node_id_to_hir_id.resize(min_size, hir::DUMMY_HIR_ID);
552 let existing_hir_id = self.node_id_to_hir_id[ast_node_id];
554 if existing_hir_id == hir::DUMMY_HIR_ID {
555 // Generate a new `HirId`.
556 let hir_id = alloc_hir_id(self);
557 self.node_id_to_hir_id[ast_node_id] = hir_id;
559 node_id: ast_node_id,
564 node_id: ast_node_id,
565 hir_id: existing_hir_id,
570 fn with_hir_id_owner<F, T>(&mut self, owner: NodeId, f: F) -> T
572 F: FnOnce(&mut Self) -> T,
574 let counter = self.item_local_id_counters
575 .insert(owner, HIR_ID_COUNTER_LOCKED)
576 .unwrap_or_else(|| panic!("No item_local_id_counters entry for {:?}", owner));
577 let def_index = self.resolver.definitions().opt_def_index(owner).unwrap();
578 self.current_hir_id_owner.push((def_index, counter));
580 let (new_def_index, new_counter) = self.current_hir_id_owner.pop().unwrap();
582 debug_assert!(def_index == new_def_index);
583 debug_assert!(new_counter >= counter);
585 let prev = self.item_local_id_counters
586 .insert(owner, new_counter)
588 debug_assert!(prev == HIR_ID_COUNTER_LOCKED);
592 /// This method allocates a new `HirId` for the given `NodeId` and stores it in
593 /// the `LoweringContext`'s `NodeId => HirId` map.
594 /// Take care not to call this method if the resulting `HirId` is then not
595 /// actually used in the HIR, as that would trigger an assertion in the
596 /// `HirIdValidator` later on, which makes sure that all `NodeId`s got mapped
597 /// properly. Calling the method twice with the same `NodeId` is fine though.
598 fn lower_node_id(&mut self, ast_node_id: NodeId) -> LoweredNodeId {
599 self.lower_node_id_generic(ast_node_id, |this| {
600 let &mut (def_index, ref mut local_id_counter) =
601 this.current_hir_id_owner.last_mut().unwrap();
602 let local_id = *local_id_counter;
603 *local_id_counter += 1;
606 local_id: hir::ItemLocalId::from_u32(local_id),
611 fn lower_node_id_with_owner(&mut self, ast_node_id: NodeId, owner: NodeId) -> LoweredNodeId {
612 self.lower_node_id_generic(ast_node_id, |this| {
613 let local_id_counter = this
614 .item_local_id_counters
616 .expect("called lower_node_id_with_owner before allocate_hir_id_counter");
617 let local_id = *local_id_counter;
619 // We want to be sure not to modify the counter in the map while it
620 // is also on the stack. Otherwise we'll get lost updates when writing
621 // back from the stack to the map.
622 debug_assert!(local_id != HIR_ID_COUNTER_LOCKED);
624 *local_id_counter += 1;
628 .opt_def_index(owner)
629 .expect("You forgot to call `create_def_with_parent` or are lowering node ids \
630 that do not belong to the current owner");
634 local_id: hir::ItemLocalId::from_u32(local_id),
639 fn record_body(&mut self, value: hir::Expr, decl: Option<&FnDecl>) -> hir::BodyId {
640 let body = hir::Body {
641 arguments: decl.map_or(hir_vec![], |decl| {
642 decl.inputs.iter().map(|x| self.lower_arg(x)).collect()
644 is_generator: self.is_generator,
648 self.bodies.insert(id, body);
652 fn next_id(&mut self) -> LoweredNodeId {
653 self.lower_node_id(self.sess.next_node_id())
656 fn expect_full_def(&mut self, id: NodeId) -> Def {
657 self.resolver.get_resolution(id).map_or(Def::Err, |pr| {
658 if pr.unresolved_segments() != 0 {
659 bug!("path not fully resolved: {:?}", pr);
665 fn expect_full_def_from_use(&mut self, id: NodeId) -> impl Iterator<Item = Def> {
666 self.resolver.get_import(id).present_items().map(|pr| {
667 if pr.unresolved_segments() != 0 {
668 bug!("path not fully resolved: {:?}", pr);
674 fn diagnostic(&self) -> &errors::Handler {
675 self.sess.diagnostic()
678 fn str_to_ident(&self, s: &'static str) -> Ident {
679 Ident::with_empty_ctxt(Symbol::gensym(s))
682 /// Reuses the span but adds information like the kind of the desugaring and features that are
683 /// allowed inside this span.
684 fn mark_span_with_reason(
686 reason: CompilerDesugaringKind,
688 allow_internal_unstable: Option<Lrc<[Symbol]>>,
690 let mark = Mark::fresh(Mark::root());
691 mark.set_expn_info(source_map::ExpnInfo {
693 def_site: Some(span),
694 format: source_map::CompilerDesugaring(reason),
695 allow_internal_unstable,
696 allow_internal_unsafe: false,
697 local_inner_macros: false,
698 edition: source_map::hygiene::default_edition(),
700 span.with_ctxt(SyntaxContext::empty().apply_mark(mark))
703 fn with_anonymous_lifetime_mode<R>(
705 anonymous_lifetime_mode: AnonymousLifetimeMode,
706 op: impl FnOnce(&mut Self) -> R,
708 let old_anonymous_lifetime_mode = self.anonymous_lifetime_mode;
709 self.anonymous_lifetime_mode = anonymous_lifetime_mode;
710 let result = op(self);
711 self.anonymous_lifetime_mode = old_anonymous_lifetime_mode;
715 /// Creates a new hir::GenericParam for every new lifetime and
716 /// type parameter encountered while evaluating `f`. Definitions
717 /// are created with the parent provided. If no `parent_id` is
718 /// provided, no definitions will be returned.
720 /// Presuming that in-band lifetimes are enabled, then
721 /// `self.anonymous_lifetime_mode` will be updated to match the
722 /// argument while `f` is running (and restored afterwards).
723 fn collect_in_band_defs<T, F>(
726 anonymous_lifetime_mode: AnonymousLifetimeMode,
728 ) -> (Vec<hir::GenericParam>, T)
730 F: FnOnce(&mut LoweringContext<'_>) -> (Vec<hir::GenericParam>, T),
732 assert!(!self.is_collecting_in_band_lifetimes);
733 assert!(self.lifetimes_to_define.is_empty());
734 let old_anonymous_lifetime_mode = self.anonymous_lifetime_mode;
736 self.anonymous_lifetime_mode = anonymous_lifetime_mode;
737 self.is_collecting_in_band_lifetimes = true;
739 let (in_band_ty_params, res) = f(self);
741 self.is_collecting_in_band_lifetimes = false;
742 self.anonymous_lifetime_mode = old_anonymous_lifetime_mode;
744 let lifetimes_to_define = self.lifetimes_to_define.split_off(0);
746 let params = lifetimes_to_define
748 .map(|(span, hir_name)| {
749 let LoweredNodeId { node_id, hir_id } = self.next_id();
751 // Get the name we'll use to make the def-path. Note
752 // that collisions are ok here and this shouldn't
753 // really show up for end-user.
754 let (str_name, kind) = match hir_name {
755 ParamName::Plain(ident) => (
756 ident.as_interned_str(),
757 hir::LifetimeParamKind::InBand,
759 ParamName::Fresh(_) => (
760 keywords::UnderscoreLifetime.name().as_interned_str(),
761 hir::LifetimeParamKind::Elided,
763 ParamName::Error => (
764 keywords::UnderscoreLifetime.name().as_interned_str(),
765 hir::LifetimeParamKind::Error,
769 // Add a definition for the in-band lifetime def.
770 self.resolver.definitions().create_def_with_parent(
773 DefPathData::LifetimeParam(str_name),
774 DefIndexAddressSpace::High,
785 pure_wrt_drop: false,
786 kind: hir::GenericParamKind::Lifetime { kind }
789 .chain(in_band_ty_params.into_iter())
795 /// When there is a reference to some lifetime `'a`, and in-band
796 /// lifetimes are enabled, then we want to push that lifetime into
797 /// the vector of names to define later. In that case, it will get
798 /// added to the appropriate generics.
799 fn maybe_collect_in_band_lifetime(&mut self, ident: Ident) {
800 if !self.is_collecting_in_band_lifetimes {
804 if !self.sess.features_untracked().in_band_lifetimes {
808 if self.in_scope_lifetimes.contains(&ident.modern()) {
812 let hir_name = ParamName::Plain(ident);
814 if self.lifetimes_to_define.iter()
815 .any(|(_, lt_name)| lt_name.modern() == hir_name.modern()) {
819 self.lifetimes_to_define.push((ident.span, hir_name));
822 /// When we have either an elided or `'_` lifetime in an impl
823 /// header, we convert it to an in-band lifetime.
824 fn collect_fresh_in_band_lifetime(&mut self, span: Span) -> ParamName {
825 assert!(self.is_collecting_in_band_lifetimes);
826 let index = self.lifetimes_to_define.len();
827 let hir_name = ParamName::Fresh(index);
828 self.lifetimes_to_define.push((span, hir_name));
832 // Evaluates `f` with the lifetimes in `params` in-scope.
833 // This is used to track which lifetimes have already been defined, and
834 // which are new in-band lifetimes that need to have a definition created
836 fn with_in_scope_lifetime_defs<T, F>(&mut self, params: &[GenericParam], f: F) -> T
838 F: FnOnce(&mut LoweringContext<'_>) -> T,
840 let old_len = self.in_scope_lifetimes.len();
841 let lt_def_names = params.iter().filter_map(|param| match param.kind {
842 GenericParamKind::Lifetime { .. } => Some(param.ident.modern()),
845 self.in_scope_lifetimes.extend(lt_def_names);
849 self.in_scope_lifetimes.truncate(old_len);
853 // Same as the method above, but accepts `hir::GenericParam`s
854 // instead of `ast::GenericParam`s.
855 // This should only be used with generics that have already had their
856 // in-band lifetimes added. In practice, this means that this function is
857 // only used when lowering a child item of a trait or impl.
858 fn with_parent_impl_lifetime_defs<T, F>(&mut self,
859 params: &HirVec<hir::GenericParam>,
862 F: FnOnce(&mut LoweringContext<'_>) -> T,
864 let old_len = self.in_scope_lifetimes.len();
865 let lt_def_names = params.iter().filter_map(|param| match param.kind {
866 hir::GenericParamKind::Lifetime { .. } => Some(param.name.ident().modern()),
869 self.in_scope_lifetimes.extend(lt_def_names);
873 self.in_scope_lifetimes.truncate(old_len);
877 /// Appends in-band lifetime defs and argument-position `impl
878 /// Trait` defs to the existing set of generics.
880 /// Presuming that in-band lifetimes are enabled, then
881 /// `self.anonymous_lifetime_mode` will be updated to match the
882 /// argument while `f` is running (and restored afterwards).
883 fn add_in_band_defs<F, T>(
887 anonymous_lifetime_mode: AnonymousLifetimeMode,
889 ) -> (hir::Generics, T)
891 F: FnOnce(&mut LoweringContext<'_>, &mut Vec<hir::GenericParam>) -> T,
893 let (in_band_defs, (mut lowered_generics, res)) = self.with_in_scope_lifetime_defs(
896 this.collect_in_band_defs(parent_id, anonymous_lifetime_mode, |this| {
897 let mut params = Vec::new();
898 let generics = this.lower_generics(
900 ImplTraitContext::Universal(&mut params),
902 let res = f(this, &mut params);
903 (params, (generics, res))
908 lowered_generics.params = lowered_generics
915 (lowered_generics, res)
918 fn with_catch_scope<T, F>(&mut self, catch_id: NodeId, f: F) -> T
920 F: FnOnce(&mut LoweringContext<'_>) -> T,
922 let len = self.catch_scopes.len();
923 self.catch_scopes.push(catch_id);
925 let result = f(self);
928 self.catch_scopes.len(),
929 "catch scopes should be added and removed in stack order"
932 self.catch_scopes.pop().unwrap();
939 capture_clause: CaptureBy,
940 closure_node_id: NodeId,
942 body: impl FnOnce(&mut LoweringContext<'_>) -> hir::Expr,
944 let prev_is_generator = mem::replace(&mut self.is_generator, true);
945 let body_expr = body(self);
946 let span = body_expr.span;
947 let output = match ret_ty {
948 Some(ty) => FunctionRetTy::Ty(P(ty.clone())),
949 None => FunctionRetTy::Default(span),
956 let body_id = self.record_body(body_expr, Some(&decl));
957 self.is_generator = prev_is_generator;
959 let capture_clause = self.lower_capture_clause(capture_clause);
960 let closure_hir_id = self.lower_node_id(closure_node_id).hir_id;
961 let decl = self.lower_fn_decl(&decl, None, /* impl trait allowed */ false, None);
962 let generator = hir::Expr {
963 hir_id: closure_hir_id,
964 node: hir::ExprKind::Closure(capture_clause, decl, body_id, span,
965 Some(hir::GeneratorMovability::Static)),
967 attrs: ThinVec::new(),
970 let unstable_span = self.mark_span_with_reason(
971 CompilerDesugaringKind::Async,
974 Symbol::intern("gen_future"),
977 let gen_future = self.expr_std_path(
978 unstable_span, &["future", "from_generator"], None, ThinVec::new());
979 hir::ExprKind::Call(P(gen_future), hir_vec![generator])
982 fn lower_body<F>(&mut self, decl: Option<&FnDecl>, f: F) -> hir::BodyId
984 F: FnOnce(&mut LoweringContext<'_>) -> hir::Expr,
986 let prev = mem::replace(&mut self.is_generator, false);
987 let result = f(self);
988 let r = self.record_body(result, decl);
989 self.is_generator = prev;
993 fn with_loop_scope<T, F>(&mut self, loop_id: NodeId, f: F) -> T
995 F: FnOnce(&mut LoweringContext<'_>) -> T,
997 // We're no longer in the base loop's condition; we're in another loop.
998 let was_in_loop_condition = self.is_in_loop_condition;
999 self.is_in_loop_condition = false;
1001 let len = self.loop_scopes.len();
1002 self.loop_scopes.push(loop_id);
1004 let result = f(self);
1007 self.loop_scopes.len(),
1008 "Loop scopes should be added and removed in stack order"
1011 self.loop_scopes.pop().unwrap();
1013 self.is_in_loop_condition = was_in_loop_condition;
1018 fn with_loop_condition_scope<T, F>(&mut self, f: F) -> T
1020 F: FnOnce(&mut LoweringContext<'_>) -> T,
1022 let was_in_loop_condition = self.is_in_loop_condition;
1023 self.is_in_loop_condition = true;
1025 let result = f(self);
1027 self.is_in_loop_condition = was_in_loop_condition;
1032 fn with_new_scopes<T, F>(&mut self, f: F) -> T
1034 F: FnOnce(&mut LoweringContext<'_>) -> T,
1036 let was_in_loop_condition = self.is_in_loop_condition;
1037 self.is_in_loop_condition = false;
1039 let catch_scopes = mem::replace(&mut self.catch_scopes, Vec::new());
1040 let loop_scopes = mem::replace(&mut self.loop_scopes, Vec::new());
1042 self.catch_scopes = catch_scopes;
1043 self.loop_scopes = loop_scopes;
1045 self.is_in_loop_condition = was_in_loop_condition;
1050 fn def_key(&mut self, id: DefId) -> DefKey {
1052 self.resolver.definitions().def_key(id.index)
1054 self.cstore.def_key(id)
1058 fn lower_label(&mut self, label: Option<Label>) -> Option<hir::Label> {
1059 label.map(|label| hir::Label {
1064 fn lower_loop_destination(&mut self, destination: Option<(NodeId, Label)>) -> hir::Destination {
1065 let target_id = match destination {
1067 if let Def::Label(loop_id) = self.expect_full_def(id) {
1068 Ok(self.lower_node_id(loop_id).hir_id)
1070 Err(hir::LoopIdError::UnresolvedLabel)
1077 .map(|id| Ok(self.lower_node_id(id).hir_id))
1078 .unwrap_or(Err(hir::LoopIdError::OutsideLoopScope))
1083 label: self.lower_label(destination.map(|(_, label)| label)),
1088 fn lower_attrs(&mut self, attrs: &[Attribute]) -> hir::HirVec<Attribute> {
1091 .map(|a| self.lower_attr(a))
1095 fn lower_attr(&mut self, attr: &Attribute) -> Attribute {
1096 // Note that we explicitly do not walk the path. Since we don't really
1097 // lower attributes (we use the AST version) there is nowhere to keep
1098 // the `HirId`s. We don't actually need HIR version of attributes anyway.
1102 path: attr.path.clone(),
1103 tokens: self.lower_token_stream(attr.tokens.clone()),
1104 is_sugared_doc: attr.is_sugared_doc,
1109 fn lower_token_stream(&mut self, tokens: TokenStream) -> TokenStream {
1112 .flat_map(|tree| self.lower_token_tree(tree).into_trees())
1116 fn lower_token_tree(&mut self, tree: TokenTree) -> TokenStream {
1118 TokenTree::Token(span, token) => self.lower_token(token, span),
1119 TokenTree::Delimited(span, delim, tts) => TokenTree::Delimited(
1122 self.lower_token_stream(tts),
1127 fn lower_token(&mut self, token: Token, span: Span) -> TokenStream {
1129 Token::Interpolated(nt) => {
1130 let tts = nt.to_tokenstream(&self.sess.parse_sess, span);
1131 self.lower_token_stream(tts)
1133 other => TokenTree::Token(span, other).into(),
1137 fn lower_arm(&mut self, arm: &Arm) -> hir::Arm {
1139 attrs: self.lower_attrs(&arm.attrs),
1140 pats: arm.pats.iter().map(|x| self.lower_pat(x)).collect(),
1141 guard: match arm.guard {
1142 Some(Guard::If(ref x)) => Some(hir::Guard::If(P(self.lower_expr(x)))),
1145 body: P(self.lower_expr(&arm.body)),
1149 fn lower_ty_binding(&mut self, b: &TypeBinding,
1150 itctx: ImplTraitContext<'_>) -> hir::TypeBinding {
1151 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(b.id);
1156 ty: self.lower_ty(&b.ty, itctx),
1161 fn lower_generic_arg(&mut self,
1162 arg: &ast::GenericArg,
1163 itctx: ImplTraitContext<'_>)
1164 -> hir::GenericArg {
1166 ast::GenericArg::Lifetime(lt) => GenericArg::Lifetime(self.lower_lifetime(<)),
1167 ast::GenericArg::Type(ty) => GenericArg::Type(self.lower_ty_direct(&ty, itctx)),
1168 ast::GenericArg::Const(ct) => {
1169 GenericArg::Const(ConstArg {
1170 value: self.lower_anon_const(&ct),
1171 span: ct.value.span,
1177 fn lower_ty(&mut self, t: &Ty, itctx: ImplTraitContext<'_>) -> P<hir::Ty> {
1178 P(self.lower_ty_direct(t, itctx))
1181 fn lower_ty_direct(&mut self, t: &Ty, mut itctx: ImplTraitContext<'_>) -> hir::Ty {
1182 let kind = match t.node {
1183 TyKind::Infer => hir::TyKind::Infer,
1184 TyKind::Err => hir::TyKind::Err,
1185 TyKind::Slice(ref ty) => hir::TyKind::Slice(self.lower_ty(ty, itctx)),
1186 TyKind::Ptr(ref mt) => hir::TyKind::Ptr(self.lower_mt(mt, itctx)),
1187 TyKind::Rptr(ref region, ref mt) => {
1188 let span = self.sess.source_map().next_point(t.span.shrink_to_lo());
1189 let lifetime = match *region {
1190 Some(ref lt) => self.lower_lifetime(lt),
1191 None => self.elided_ref_lifetime(span),
1193 hir::TyKind::Rptr(lifetime, self.lower_mt(mt, itctx))
1195 TyKind::BareFn(ref f) => self.with_in_scope_lifetime_defs(
1198 this.with_anonymous_lifetime_mode(
1199 AnonymousLifetimeMode::PassThrough,
1201 hir::TyKind::BareFn(P(hir::BareFnTy {
1202 generic_params: this.lower_generic_params(
1204 &NodeMap::default(),
1205 ImplTraitContext::disallowed(),
1207 unsafety: this.lower_unsafety(f.unsafety),
1209 decl: this.lower_fn_decl(&f.decl, None, false, None),
1210 arg_names: this.lower_fn_args_to_names(&f.decl),
1216 TyKind::Never => hir::TyKind::Never,
1217 TyKind::Tup(ref tys) => {
1218 hir::TyKind::Tup(tys.iter().map(|ty| {
1219 self.lower_ty_direct(ty, itctx.reborrow())
1222 TyKind::Paren(ref ty) => {
1223 return self.lower_ty_direct(ty, itctx);
1225 TyKind::Path(ref qself, ref path) => {
1226 let id = self.lower_node_id(t.id);
1227 let qpath = self.lower_qpath(t.id, qself, path, ParamMode::Explicit, itctx);
1228 let ty = self.ty_path(id, t.span, qpath);
1229 if let hir::TyKind::TraitObject(..) = ty.node {
1230 self.maybe_lint_bare_trait(t.span, t.id, qself.is_none() && path.is_global());
1234 TyKind::ImplicitSelf => hir::TyKind::Path(hir::QPath::Resolved(
1237 def: self.expect_full_def(t.id),
1238 segments: hir_vec![hir::PathSegment::from_ident(keywords::SelfUpper.ident())],
1242 TyKind::Array(ref ty, ref length) => {
1243 hir::TyKind::Array(self.lower_ty(ty, itctx), self.lower_anon_const(length))
1245 TyKind::Typeof(ref expr) => {
1246 hir::TyKind::Typeof(self.lower_anon_const(expr))
1248 TyKind::TraitObject(ref bounds, kind) => {
1249 let mut lifetime_bound = None;
1252 .filter_map(|bound| match *bound {
1253 GenericBound::Trait(ref ty, TraitBoundModifier::None) => {
1254 Some(self.lower_poly_trait_ref(ty, itctx.reborrow()))
1256 GenericBound::Trait(_, TraitBoundModifier::Maybe) => None,
1257 GenericBound::Outlives(ref lifetime) => {
1258 if lifetime_bound.is_none() {
1259 lifetime_bound = Some(self.lower_lifetime(lifetime));
1265 let lifetime_bound =
1266 lifetime_bound.unwrap_or_else(|| self.elided_dyn_bound(t.span));
1267 if kind != TraitObjectSyntax::Dyn {
1268 self.maybe_lint_bare_trait(t.span, t.id, false);
1270 hir::TyKind::TraitObject(bounds, lifetime_bound)
1272 TyKind::ImplTrait(def_node_id, ref bounds) => {
1275 ImplTraitContext::Existential(fn_def_id) => {
1276 self.lower_existential_impl_trait(
1277 span, fn_def_id, def_node_id,
1278 |this| this.lower_param_bounds(bounds, itctx),
1281 ImplTraitContext::Universal(in_band_ty_params) => {
1282 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(def_node_id);
1283 // Add a definition for the in-band `Param`.
1284 let def_index = self
1287 .opt_def_index(def_node_id)
1290 let hir_bounds = self.lower_param_bounds(
1292 ImplTraitContext::Universal(in_band_ty_params),
1294 // Set the name to `impl Bound1 + Bound2`.
1295 let ident = Ident::from_str(&pprust::ty_to_string(t)).with_span_pos(span);
1296 in_band_ty_params.push(hir::GenericParam {
1298 name: ParamName::Plain(ident),
1299 pure_wrt_drop: false,
1303 kind: hir::GenericParamKind::Type {
1305 synthetic: Some(hir::SyntheticTyParamKind::ImplTrait),
1309 hir::TyKind::Path(hir::QPath::Resolved(
1313 def: Def::TyParam(DefId::local(def_index)),
1314 segments: hir_vec![hir::PathSegment::from_ident(ident)],
1318 ImplTraitContext::Disallowed(pos) => {
1319 let allowed_in = if self.sess.features_untracked()
1320 .impl_trait_in_bindings {
1321 "bindings or function and inherent method return types"
1323 "function and inherent method return types"
1325 let mut err = struct_span_err!(
1329 "`impl Trait` not allowed outside of {}",
1332 if pos == ImplTraitPosition::Binding &&
1333 nightly_options::is_nightly_build() {
1335 "add #![feature(impl_trait_in_bindings)] to the crate attributes \
1343 TyKind::Mac(_) => panic!("TyMac should have been expanded by now."),
1344 TyKind::CVarArgs => {
1345 // Create the implicit lifetime of the "spoofed" `VaList`.
1346 let span = self.sess.source_map().next_point(t.span.shrink_to_lo());
1347 let lt = self.new_implicit_lifetime(span);
1348 hir::TyKind::CVarArgs(lt)
1352 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(t.id);
1360 fn lower_existential_impl_trait(
1363 fn_def_id: Option<DefId>,
1364 exist_ty_node_id: NodeId,
1365 lower_bounds: impl FnOnce(&mut LoweringContext<'_>) -> hir::GenericBounds,
1367 // Make sure we know that some funky desugaring has been going on here.
1368 // This is a first: there is code in other places like for loop
1369 // desugaring that explicitly states that we don't want to track that.
1370 // Not tracking it makes lints in rustc and clippy very fragile as
1371 // frequently opened issues show.
1372 let exist_ty_span = self.mark_span_with_reason(
1373 CompilerDesugaringKind::ExistentialReturnType,
1378 let exist_ty_def_index = self
1381 .opt_def_index(exist_ty_node_id)
1384 self.allocate_hir_id_counter(exist_ty_node_id, &"existential impl trait");
1386 let hir_bounds = self.with_hir_id_owner(exist_ty_node_id, lower_bounds);
1388 let (lifetimes, lifetime_defs) = self.lifetimes_from_impl_trait_bounds(
1394 self.with_hir_id_owner(exist_ty_node_id, |lctx| {
1395 let LoweredNodeId { node_id: _, hir_id } = lctx.next_id();
1396 let exist_ty_item_kind = hir::ItemKind::Existential(hir::ExistTy {
1397 generics: hir::Generics {
1398 params: lifetime_defs,
1399 where_clause: hir::WhereClause {
1401 predicates: Vec::new().into(),
1406 impl_trait_fn: fn_def_id,
1408 let exist_ty_id = lctx.lower_node_id(exist_ty_node_id);
1409 // Generate an `existential type Foo: Trait;` declaration.
1410 trace!("creating existential type with id {:#?}", exist_ty_id);
1412 trace!("exist ty def index: {:#?}", exist_ty_def_index);
1413 let exist_ty_item = hir::Item {
1414 hir_id: exist_ty_id.hir_id,
1415 ident: keywords::Invalid.ident(),
1416 attrs: Default::default(),
1417 node: exist_ty_item_kind,
1418 vis: respan(span.shrink_to_lo(), hir::VisibilityKind::Inherited),
1419 span: exist_ty_span,
1422 // Insert the item into the global list. This usually happens
1423 // automatically for all AST items. But this existential type item
1424 // does not actually exist in the AST.
1425 lctx.insert_item(exist_ty_id.node_id, exist_ty_item);
1427 // `impl Trait` now just becomes `Foo<'a, 'b, ..>`.
1428 hir::TyKind::Def(hir::ItemId { id: exist_ty_id.node_id }, lifetimes)
1432 fn lifetimes_from_impl_trait_bounds(
1434 exist_ty_id: NodeId,
1435 parent_index: DefIndex,
1436 bounds: &hir::GenericBounds,
1437 ) -> (HirVec<hir::GenericArg>, HirVec<hir::GenericParam>) {
1438 // This visitor walks over impl trait bounds and creates defs for all lifetimes which
1439 // appear in the bounds, excluding lifetimes that are created within the bounds.
1440 // E.g., `'a`, `'b`, but not `'c` in `impl for<'c> SomeTrait<'a, 'b, 'c>`.
1441 struct ImplTraitLifetimeCollector<'r, 'a: 'r> {
1442 context: &'r mut LoweringContext<'a>,
1444 exist_ty_id: NodeId,
1445 collect_elided_lifetimes: bool,
1446 currently_bound_lifetimes: Vec<hir::LifetimeName>,
1447 already_defined_lifetimes: FxHashSet<hir::LifetimeName>,
1448 output_lifetimes: Vec<hir::GenericArg>,
1449 output_lifetime_params: Vec<hir::GenericParam>,
1452 impl<'r, 'a: 'r, 'v> hir::intravisit::Visitor<'v> for ImplTraitLifetimeCollector<'r, 'a> {
1453 fn nested_visit_map<'this>(
1455 ) -> hir::intravisit::NestedVisitorMap<'this, 'v> {
1456 hir::intravisit::NestedVisitorMap::None
1459 fn visit_generic_args(&mut self, span: Span, parameters: &'v hir::GenericArgs) {
1460 // Don't collect elided lifetimes used inside of `Fn()` syntax.
1461 if parameters.parenthesized {
1462 let old_collect_elided_lifetimes = self.collect_elided_lifetimes;
1463 self.collect_elided_lifetimes = false;
1464 hir::intravisit::walk_generic_args(self, span, parameters);
1465 self.collect_elided_lifetimes = old_collect_elided_lifetimes;
1467 hir::intravisit::walk_generic_args(self, span, parameters);
1471 fn visit_ty(&mut self, t: &'v hir::Ty) {
1472 // Don't collect elided lifetimes used inside of `fn()` syntax.
1473 if let hir::TyKind::BareFn(_) = t.node {
1474 let old_collect_elided_lifetimes = self.collect_elided_lifetimes;
1475 self.collect_elided_lifetimes = false;
1477 // Record the "stack height" of `for<'a>` lifetime bindings
1478 // to be able to later fully undo their introduction.
1479 let old_len = self.currently_bound_lifetimes.len();
1480 hir::intravisit::walk_ty(self, t);
1481 self.currently_bound_lifetimes.truncate(old_len);
1483 self.collect_elided_lifetimes = old_collect_elided_lifetimes;
1485 hir::intravisit::walk_ty(self, t)
1489 fn visit_poly_trait_ref(
1491 trait_ref: &'v hir::PolyTraitRef,
1492 modifier: hir::TraitBoundModifier,
1494 // Record the "stack height" of `for<'a>` lifetime bindings
1495 // to be able to later fully undo their introduction.
1496 let old_len = self.currently_bound_lifetimes.len();
1497 hir::intravisit::walk_poly_trait_ref(self, trait_ref, modifier);
1498 self.currently_bound_lifetimes.truncate(old_len);
1501 fn visit_generic_param(&mut self, param: &'v hir::GenericParam) {
1502 // Record the introduction of 'a in `for<'a> ...`.
1503 if let hir::GenericParamKind::Lifetime { .. } = param.kind {
1504 // Introduce lifetimes one at a time so that we can handle
1505 // cases like `fn foo<'d>() -> impl for<'a, 'b: 'a, 'c: 'b + 'd>`.
1506 let lt_name = hir::LifetimeName::Param(param.name);
1507 self.currently_bound_lifetimes.push(lt_name);
1510 hir::intravisit::walk_generic_param(self, param);
1513 fn visit_lifetime(&mut self, lifetime: &'v hir::Lifetime) {
1514 let name = match lifetime.name {
1515 hir::LifetimeName::Implicit | hir::LifetimeName::Underscore => {
1516 if self.collect_elided_lifetimes {
1517 // Use `'_` for both implicit and underscore lifetimes in
1518 // `abstract type Foo<'_>: SomeTrait<'_>;`.
1519 hir::LifetimeName::Underscore
1524 hir::LifetimeName::Param(_) => lifetime.name,
1525 hir::LifetimeName::Error | hir::LifetimeName::Static => return,
1528 if !self.currently_bound_lifetimes.contains(&name)
1529 && !self.already_defined_lifetimes.contains(&name) {
1530 self.already_defined_lifetimes.insert(name);
1532 let LoweredNodeId { node_id: _, hir_id } = self.context.next_id();
1533 self.output_lifetimes.push(hir::GenericArg::Lifetime(hir::Lifetime {
1535 span: lifetime.span,
1539 // We need to manually create the ids here, because the
1540 // definitions will go into the explicit `existential type`
1541 // declaration and thus need to have their owner set to that item
1542 let def_node_id = self.context.sess.next_node_id();
1543 let LoweredNodeId { node_id: _, hir_id } =
1544 self.context.lower_node_id_with_owner(def_node_id, self.exist_ty_id);
1545 self.context.resolver.definitions().create_def_with_parent(
1548 DefPathData::LifetimeParam(name.ident().as_interned_str()),
1549 DefIndexAddressSpace::High,
1554 let (name, kind) = match name {
1555 hir::LifetimeName::Underscore => (
1556 hir::ParamName::Plain(keywords::UnderscoreLifetime.ident()),
1557 hir::LifetimeParamKind::Elided,
1559 hir::LifetimeName::Param(param_name) => (
1561 hir::LifetimeParamKind::Explicit,
1563 _ => bug!("expected LifetimeName::Param or ParamName::Plain"),
1566 self.output_lifetime_params.push(hir::GenericParam {
1569 span: lifetime.span,
1570 pure_wrt_drop: false,
1573 kind: hir::GenericParamKind::Lifetime { kind }
1579 let mut lifetime_collector = ImplTraitLifetimeCollector {
1581 parent: parent_index,
1583 collect_elided_lifetimes: true,
1584 currently_bound_lifetimes: Vec::new(),
1585 already_defined_lifetimes: FxHashSet::default(),
1586 output_lifetimes: Vec::new(),
1587 output_lifetime_params: Vec::new(),
1590 for bound in bounds {
1591 hir::intravisit::walk_param_bound(&mut lifetime_collector, &bound);
1595 lifetime_collector.output_lifetimes.into(),
1596 lifetime_collector.output_lifetime_params.into(),
1600 fn lower_foreign_mod(&mut self, fm: &ForeignMod) -> hir::ForeignMod {
1605 .map(|x| self.lower_foreign_item(x))
1610 fn lower_global_asm(&mut self, ga: &GlobalAsm) -> P<hir::GlobalAsm> {
1617 fn lower_variant(&mut self, v: &Variant) -> hir::Variant {
1619 node: hir::VariantKind {
1620 ident: v.node.ident,
1621 attrs: self.lower_attrs(&v.node.attrs),
1622 data: self.lower_variant_data(&v.node.data),
1623 disr_expr: v.node.disr_expr.as_ref().map(|e| self.lower_anon_const(e)),
1632 qself: &Option<QSelf>,
1634 param_mode: ParamMode,
1635 mut itctx: ImplTraitContext<'_>,
1637 let qself_position = qself.as_ref().map(|q| q.position);
1638 let qself = qself.as_ref().map(|q| self.lower_ty(&q.ty, itctx.reborrow()));
1640 let resolution = self.resolver
1642 .unwrap_or_else(|| PathResolution::new(Def::Err));
1644 let proj_start = p.segments.len() - resolution.unresolved_segments();
1645 let path = P(hir::Path {
1646 def: resolution.base_def(),
1647 segments: p.segments[..proj_start]
1650 .map(|(i, segment)| {
1651 let param_mode = match (qself_position, param_mode) {
1652 (Some(j), ParamMode::Optional) if i < j => {
1653 // This segment is part of the trait path in a
1654 // qualified path - one of `a`, `b` or `Trait`
1655 // in `<X as a::b::Trait>::T::U::method`.
1661 // Figure out if this is a type/trait segment,
1662 // which may need lifetime elision performed.
1663 let parent_def_id = |this: &mut Self, def_id: DefId| DefId {
1664 krate: def_id.krate,
1665 index: this.def_key(def_id).parent.expect("missing parent"),
1667 let type_def_id = match resolution.base_def() {
1668 Def::AssociatedTy(def_id) if i + 2 == proj_start => {
1669 Some(parent_def_id(self, def_id))
1671 Def::Variant(def_id) if i + 1 == proj_start => {
1672 Some(parent_def_id(self, def_id))
1675 | Def::Union(def_id)
1677 | Def::TyAlias(def_id)
1678 | Def::Trait(def_id) if i + 1 == proj_start =>
1684 let parenthesized_generic_args = match resolution.base_def() {
1685 // `a::b::Trait(Args)`
1686 Def::Trait(..) if i + 1 == proj_start => ParenthesizedGenericArgs::Ok,
1687 // `a::b::Trait(Args)::TraitItem`
1688 Def::Method(..) | Def::AssociatedConst(..) | Def::AssociatedTy(..)
1689 if i + 2 == proj_start =>
1691 ParenthesizedGenericArgs::Ok
1693 // Avoid duplicated errors.
1694 Def::Err => ParenthesizedGenericArgs::Ok,
1700 | Def::Variant(..) if i + 1 == proj_start =>
1702 ParenthesizedGenericArgs::Err
1704 // A warning for now, for compatibility reasons
1705 _ => ParenthesizedGenericArgs::Warn,
1708 let num_lifetimes = type_def_id.map_or(0, |def_id| {
1709 if let Some(&n) = self.type_def_lifetime_params.get(&def_id) {
1712 assert!(!def_id.is_local());
1714 self.cstore.item_generics_cloned_untracked(def_id, self.sess);
1715 let n = item_generics.own_counts().lifetimes;
1716 self.type_def_lifetime_params.insert(def_id, n);
1719 self.lower_path_segment(
1724 parenthesized_generic_args,
1733 // Simple case, either no projections, or only fully-qualified.
1734 // E.g., `std::mem::size_of` or `<I as Iterator>::Item`.
1735 if resolution.unresolved_segments() == 0 {
1736 return hir::QPath::Resolved(qself, path);
1739 // Create the innermost type that we're projecting from.
1740 let mut ty = if path.segments.is_empty() {
1741 // If the base path is empty that means there exists a
1742 // syntactical `Self`, e.g., `&i32` in `<&i32>::clone`.
1743 qself.expect("missing QSelf for <T>::...")
1745 // Otherwise, the base path is an implicit `Self` type path,
1746 // e.g., `Vec` in `Vec::new` or `<I as Iterator>::Item` in
1747 // `<I as Iterator>::Item::default`.
1748 let new_id = self.next_id();
1749 P(self.ty_path(new_id, p.span, hir::QPath::Resolved(qself, path)))
1752 // Anything after the base path are associated "extensions",
1753 // out of which all but the last one are associated types,
1754 // e.g., for `std::vec::Vec::<T>::IntoIter::Item::clone`:
1755 // * base path is `std::vec::Vec<T>`
1756 // * "extensions" are `IntoIter`, `Item` and `clone`
1757 // * type nodes are:
1758 // 1. `std::vec::Vec<T>` (created above)
1759 // 2. `<std::vec::Vec<T>>::IntoIter`
1760 // 3. `<<std::vec::Vec<T>>::IntoIter>::Item`
1761 // * final path is `<<<std::vec::Vec<T>>::IntoIter>::Item>::clone`
1762 for (i, segment) in p.segments.iter().enumerate().skip(proj_start) {
1763 let segment = P(self.lower_path_segment(
1768 ParenthesizedGenericArgs::Warn,
1772 let qpath = hir::QPath::TypeRelative(ty, segment);
1774 // It's finished, return the extension of the right node type.
1775 if i == p.segments.len() - 1 {
1779 // Wrap the associated extension in another type node.
1780 let new_id = self.next_id();
1781 ty = P(self.ty_path(new_id, p.span, qpath));
1784 // We should've returned in the for loop above.
1787 "lower_qpath: no final extension segment in {}..{}",
1793 fn lower_path_extra(
1797 param_mode: ParamMode,
1798 explicit_owner: Option<NodeId>,
1802 segments: p.segments
1805 self.lower_path_segment(
1810 ParenthesizedGenericArgs::Err,
1811 ImplTraitContext::disallowed(),
1820 fn lower_path(&mut self, id: NodeId, p: &Path, param_mode: ParamMode) -> hir::Path {
1821 let def = self.expect_full_def(id);
1822 self.lower_path_extra(def, p, param_mode, None)
1825 fn lower_path_segment(
1828 segment: &PathSegment,
1829 param_mode: ParamMode,
1830 expected_lifetimes: usize,
1831 parenthesized_generic_args: ParenthesizedGenericArgs,
1832 itctx: ImplTraitContext<'_>,
1833 explicit_owner: Option<NodeId>,
1834 ) -> hir::PathSegment {
1835 let (mut generic_args, infer_types) = if let Some(ref generic_args) = segment.args {
1836 let msg = "parenthesized type parameters may only be used with a `Fn` trait";
1837 match **generic_args {
1838 GenericArgs::AngleBracketed(ref data) => {
1839 self.lower_angle_bracketed_parameter_data(data, param_mode, itctx)
1841 GenericArgs::Parenthesized(ref data) => match parenthesized_generic_args {
1842 ParenthesizedGenericArgs::Ok => self.lower_parenthesized_parameter_data(data),
1843 ParenthesizedGenericArgs::Warn => {
1844 self.sess.buffer_lint(
1845 PARENTHESIZED_PARAMS_IN_TYPES_AND_MODULES,
1850 (hir::GenericArgs::none(), true)
1852 ParenthesizedGenericArgs::Err => {
1853 let mut err = struct_span_err!(self.sess, data.span, E0214, "{}", msg);
1854 err.span_label(data.span, "only `Fn` traits may use parentheses");
1855 if let Ok(snippet) = self.sess.source_map().span_to_snippet(data.span) {
1856 // Do not suggest going from `Trait()` to `Trait<>`
1857 if data.inputs.len() > 0 {
1858 err.span_suggestion(
1860 "use angle brackets instead",
1861 format!("<{}>", &snippet[1..snippet.len() - 1]),
1862 Applicability::MaybeIncorrect,
1867 (self.lower_angle_bracketed_parameter_data(
1868 &data.as_angle_bracketed_args(),
1876 self.lower_angle_bracketed_parameter_data(&Default::default(), param_mode, itctx)
1879 let has_lifetimes = generic_args.args.iter().any(|arg| match arg {
1880 GenericArg::Lifetime(_) => true,
1883 let first_generic_span = generic_args.args.iter().map(|a| a.span())
1884 .chain(generic_args.bindings.iter().map(|b| b.span)).next();
1885 if !generic_args.parenthesized && !has_lifetimes {
1887 self.elided_path_lifetimes(path_span, expected_lifetimes)
1889 .map(|lt| GenericArg::Lifetime(lt))
1890 .chain(generic_args.args.into_iter())
1892 if expected_lifetimes > 0 && param_mode == ParamMode::Explicit {
1893 let anon_lt_suggestion = vec!["'_"; expected_lifetimes].join(", ");
1894 let no_ty_args = generic_args.args.len() == expected_lifetimes;
1895 let no_bindings = generic_args.bindings.is_empty();
1896 let (incl_angl_brckt, insertion_span, suggestion) = if no_ty_args && no_bindings {
1897 // If there are no (non-implicit) generic args or associated-type
1898 // bindings, our suggestion includes the angle brackets.
1899 (true, path_span.shrink_to_hi(), format!("<{}>", anon_lt_suggestion))
1901 // Otherwise—sorry, this is kind of gross—we need to infer the
1902 // place to splice in the `'_, ` from the generics that do exist.
1903 let first_generic_span = first_generic_span
1904 .expect("already checked that type args or bindings exist");
1905 (false, first_generic_span.shrink_to_lo(), format!("{}, ", anon_lt_suggestion))
1907 self.sess.buffer_lint_with_diagnostic(
1908 ELIDED_LIFETIMES_IN_PATHS,
1911 "hidden lifetime parameters in types are deprecated",
1912 builtin::BuiltinLintDiagnostics::ElidedLifetimesInPaths(
1913 expected_lifetimes, path_span, incl_angl_brckt, insertion_span, suggestion
1919 let def = self.expect_full_def(segment.id);
1920 let id = if let Some(owner) = explicit_owner {
1921 self.lower_node_id_with_owner(segment.id, owner)
1923 self.lower_node_id(segment.id)
1926 "lower_path_segment: ident={:?} original-id={:?} new-id={:?}",
1927 segment.ident, segment.id, id,
1930 hir::PathSegment::new(
1939 fn lower_angle_bracketed_parameter_data(
1941 data: &AngleBracketedArgs,
1942 param_mode: ParamMode,
1943 mut itctx: ImplTraitContext<'_>,
1944 ) -> (hir::GenericArgs, bool) {
1945 let &AngleBracketedArgs { ref args, ref bindings, .. } = data;
1946 let has_types = args.iter().any(|arg| match arg {
1947 ast::GenericArg::Type(_) => true,
1951 args: args.iter().map(|a| self.lower_generic_arg(a, itctx.reborrow())).collect(),
1952 bindings: bindings.iter().map(|b| self.lower_ty_binding(b, itctx.reborrow())).collect(),
1953 parenthesized: false,
1955 !has_types && param_mode == ParamMode::Optional)
1958 fn lower_parenthesized_parameter_data(
1960 data: &ParenthesizedArgs,
1961 ) -> (hir::GenericArgs, bool) {
1962 // Switch to `PassThrough` mode for anonymous lifetimes: this
1963 // means that we permit things like `&Ref<T>`, where `Ref` has
1964 // a hidden lifetime parameter. This is needed for backwards
1965 // compatibility, even in contexts like an impl header where
1966 // we generally don't permit such things (see #51008).
1967 self.with_anonymous_lifetime_mode(
1968 AnonymousLifetimeMode::PassThrough,
1970 let &ParenthesizedArgs { ref inputs, ref output, span } = data;
1973 .map(|ty| this.lower_ty_direct(ty, ImplTraitContext::disallowed()))
1975 let mk_tup = |this: &mut Self, tys, span| {
1976 let LoweredNodeId { node_id: _, hir_id } = this.next_id();
1977 hir::Ty { node: hir::TyKind::Tup(tys), hir_id, span }
1979 let LoweredNodeId { node_id: _, hir_id } = this.next_id();
1983 args: hir_vec![GenericArg::Type(mk_tup(this, inputs, span))],
1987 ident: Ident::from_str(FN_OUTPUT_NAME),
1990 .map(|ty| this.lower_ty(&ty, ImplTraitContext::disallowed()))
1991 .unwrap_or_else(|| P(mk_tup(this, hir::HirVec::new(), span))),
1992 span: output.as_ref().map_or(span, |ty| ty.span),
1995 parenthesized: true,
2003 fn lower_local(&mut self, l: &Local) -> (hir::Local, SmallVec<[hir::ItemId; 1]>) {
2004 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(l.id);
2005 let mut ids = SmallVec::<[hir::ItemId; 1]>::new();
2006 if self.sess.features_untracked().impl_trait_in_bindings {
2007 if let Some(ref ty) = l.ty {
2008 let mut visitor = ImplTraitTypeIdVisitor { ids: &mut ids };
2009 visitor.visit_ty(ty);
2012 let parent_def_id = DefId::local(self.current_hir_id_owner.last().unwrap().0);
2017 .map(|t| self.lower_ty(t,
2018 if self.sess.features_untracked().impl_trait_in_bindings {
2019 ImplTraitContext::Existential(Some(parent_def_id))
2021 ImplTraitContext::Disallowed(ImplTraitPosition::Binding)
2024 pat: self.lower_pat(&l.pat),
2025 init: l.init.as_ref().map(|e| P(self.lower_expr(e))),
2027 attrs: l.attrs.clone(),
2028 source: hir::LocalSource::Normal,
2032 fn lower_mutability(&mut self, m: Mutability) -> hir::Mutability {
2034 Mutability::Mutable => hir::MutMutable,
2035 Mutability::Immutable => hir::MutImmutable,
2039 fn lower_arg(&mut self, arg: &Arg) -> hir::Arg {
2040 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(arg.id);
2043 pat: self.lower_pat(&arg.pat),
2047 fn lower_fn_args_to_names(&mut self, decl: &FnDecl) -> hir::HirVec<Ident> {
2050 .map(|arg| match arg.pat.node {
2051 PatKind::Ident(_, ident, _) => ident,
2052 _ => Ident::new(keywords::Invalid.name(), arg.pat.span),
2057 // Lowers a function declaration.
2059 // decl: the unlowered (ast) function declaration.
2060 // fn_def_id: if `Some`, impl Trait arguments are lowered into generic parameters on the
2061 // given DefId, otherwise impl Trait is disallowed. Must be `Some` if
2062 // make_ret_async is also `Some`.
2063 // impl_trait_return_allow: determines whether impl Trait can be used in return position.
2064 // This guards against trait declarations and implementations where impl Trait is
2066 // make_ret_async: if `Some`, converts `-> T` into `-> impl Future<Output = T>` in the
2067 // return type. This is used for `async fn` declarations. The `NodeId` is the id of the
2068 // return type impl Trait item.
2072 mut in_band_ty_params: Option<(DefId, &mut Vec<hir::GenericParam>)>,
2073 impl_trait_return_allow: bool,
2074 make_ret_async: Option<NodeId>,
2075 ) -> P<hir::FnDecl> {
2076 let inputs = decl.inputs
2079 if let Some((_, ref mut ibty)) = in_band_ty_params {
2080 self.lower_ty_direct(&arg.ty, ImplTraitContext::Universal(ibty))
2082 self.lower_ty_direct(&arg.ty, ImplTraitContext::disallowed())
2085 .collect::<HirVec<_>>();
2087 let output = if let Some(ret_id) = make_ret_async {
2088 self.lower_async_fn_ret_ty(
2091 in_band_ty_params.expect("make_ret_async but no fn_def_id").0,
2096 FunctionRetTy::Ty(ref ty) => match in_band_ty_params {
2097 Some((def_id, _)) if impl_trait_return_allow => {
2098 hir::Return(self.lower_ty(ty,
2099 ImplTraitContext::Existential(Some(def_id))))
2102 hir::Return(self.lower_ty(ty, ImplTraitContext::disallowed()))
2105 FunctionRetTy::Default(span) => hir::DefaultReturn(span),
2112 c_variadic: decl.c_variadic,
2113 implicit_self: decl.inputs.get(0).map_or(
2114 hir::ImplicitSelfKind::None,
2116 let is_mutable_pat = match arg.pat.node {
2117 PatKind::Ident(BindingMode::ByValue(mt), _, _) |
2118 PatKind::Ident(BindingMode::ByRef(mt), _, _) =>
2119 mt == Mutability::Mutable,
2124 TyKind::ImplicitSelf if is_mutable_pat => hir::ImplicitSelfKind::Mut,
2125 TyKind::ImplicitSelf => hir::ImplicitSelfKind::Imm,
2126 // Given we are only considering `ImplicitSelf` types, we needn't consider
2127 // the case where we have a mutable pattern to a reference as that would
2128 // no longer be an `ImplicitSelf`.
2129 TyKind::Rptr(_, ref mt) if mt.ty.node.is_implicit_self() &&
2130 mt.mutbl == ast::Mutability::Mutable =>
2131 hir::ImplicitSelfKind::MutRef,
2132 TyKind::Rptr(_, ref mt) if mt.ty.node.is_implicit_self() =>
2133 hir::ImplicitSelfKind::ImmRef,
2134 _ => hir::ImplicitSelfKind::None,
2141 // Transform `-> T` into `-> impl Future<Output = T>` for `async fn`
2143 // fn_span: the span of the async function declaration. Used for error reporting.
2144 // inputs: lowered types of arguments to the function. Used to collect lifetimes.
2145 // output: unlowered output type (`T` in `-> T`)
2146 // fn_def_id: DefId of the parent function. Used to create child impl trait definition.
2147 fn lower_async_fn_ret_ty(
2150 output: &FunctionRetTy,
2152 return_impl_trait_id: NodeId,
2153 ) -> hir::FunctionRetTy {
2154 // Get lifetimes used in the input arguments to the function. Our output type must also
2155 // have the same lifetime.
2156 // FIXME(cramertj): multiple different lifetimes are not allowed because
2157 // `impl Trait + 'a + 'b` doesn't allow for capture `'a` and `'b` where neither is a subset
2158 // of the other. We really want some new lifetime that is a subset of all input lifetimes,
2159 // but that doesn't exist at the moment.
2161 struct AsyncFnLifetimeCollector<'r, 'a: 'r> {
2162 context: &'r mut LoweringContext<'a>,
2163 // Lifetimes bound by HRTB.
2164 currently_bound_lifetimes: Vec<hir::LifetimeName>,
2165 // Whether to count elided lifetimes.
2166 // Disabled inside of `Fn` or `fn` syntax.
2167 collect_elided_lifetimes: bool,
2168 // The lifetime found.
2169 // Multiple different or elided lifetimes cannot appear in async fn for now.
2170 output_lifetime: Option<(hir::LifetimeName, Span)>,
2173 impl<'r, 'a: 'r, 'v> hir::intravisit::Visitor<'v> for AsyncFnLifetimeCollector<'r, 'a> {
2174 fn nested_visit_map<'this>(
2176 ) -> hir::intravisit::NestedVisitorMap<'this, 'v> {
2177 hir::intravisit::NestedVisitorMap::None
2180 fn visit_generic_args(&mut self, span: Span, parameters: &'v hir::GenericArgs) {
2181 // Don't collect elided lifetimes used inside of `Fn()` syntax.
2182 if parameters.parenthesized {
2183 let old_collect_elided_lifetimes = self.collect_elided_lifetimes;
2184 self.collect_elided_lifetimes = false;
2185 hir::intravisit::walk_generic_args(self, span, parameters);
2186 self.collect_elided_lifetimes = old_collect_elided_lifetimes;
2188 hir::intravisit::walk_generic_args(self, span, parameters);
2192 fn visit_ty(&mut self, t: &'v hir::Ty) {
2193 // Don't collect elided lifetimes used inside of `fn()` syntax.
2194 if let &hir::TyKind::BareFn(_) = &t.node {
2195 let old_collect_elided_lifetimes = self.collect_elided_lifetimes;
2196 self.collect_elided_lifetimes = false;
2198 // Record the "stack height" of `for<'a>` lifetime bindings
2199 // to be able to later fully undo their introduction.
2200 let old_len = self.currently_bound_lifetimes.len();
2201 hir::intravisit::walk_ty(self, t);
2202 self.currently_bound_lifetimes.truncate(old_len);
2204 self.collect_elided_lifetimes = old_collect_elided_lifetimes;
2206 hir::intravisit::walk_ty(self, t);
2210 fn visit_poly_trait_ref(
2212 trait_ref: &'v hir::PolyTraitRef,
2213 modifier: hir::TraitBoundModifier,
2215 // Record the "stack height" of `for<'a>` lifetime bindings
2216 // to be able to later fully undo their introduction.
2217 let old_len = self.currently_bound_lifetimes.len();
2218 hir::intravisit::walk_poly_trait_ref(self, trait_ref, modifier);
2219 self.currently_bound_lifetimes.truncate(old_len);
2222 fn visit_generic_param(&mut self, param: &'v hir::GenericParam) {
2223 // Record the introduction of 'a in `for<'a> ...`
2224 if let hir::GenericParamKind::Lifetime { .. } = param.kind {
2225 // Introduce lifetimes one at a time so that we can handle
2226 // cases like `fn foo<'d>() -> impl for<'a, 'b: 'a, 'c: 'b + 'd>`
2227 let lt_name = hir::LifetimeName::Param(param.name);
2228 self.currently_bound_lifetimes.push(lt_name);
2231 hir::intravisit::walk_generic_param(self, param);
2234 fn visit_lifetime(&mut self, lifetime: &'v hir::Lifetime) {
2235 let name = match lifetime.name {
2236 hir::LifetimeName::Implicit | hir::LifetimeName::Underscore => {
2237 if self.collect_elided_lifetimes {
2238 // Use `'_` for both implicit and underscore lifetimes in
2239 // `abstract type Foo<'_>: SomeTrait<'_>;`
2240 hir::LifetimeName::Underscore
2245 hir::LifetimeName::Param(_) => lifetime.name,
2246 hir::LifetimeName::Error | hir::LifetimeName::Static => return,
2249 if !self.currently_bound_lifetimes.contains(&name) {
2250 if let Some((current_lt_name, current_lt_span)) = self.output_lifetime {
2251 // We don't currently have a reliable way to desugar `async fn` with
2252 // multiple potentially unrelated input lifetimes into
2253 // `-> impl Trait + 'lt`, so we report an error in this case.
2254 if current_lt_name != name {
2257 MultiSpan::from_spans(vec![current_lt_span, lifetime.span]),
2259 "multiple different lifetimes used in arguments of `async fn`",
2261 .span_label(current_lt_span, "first lifetime here")
2262 .span_label(lifetime.span, "different lifetime here")
2263 .help("`async fn` can only accept borrowed values \
2264 with identical lifetimes")
2266 } else if current_lt_name.is_elided() && name.is_elided() {
2269 MultiSpan::from_spans(vec![current_lt_span, lifetime.span]),
2271 "multiple elided lifetimes used in arguments of `async fn`",
2273 .span_label(current_lt_span, "first lifetime here")
2274 .span_label(lifetime.span, "different lifetime here")
2275 .help("consider giving these arguments named lifetimes")
2279 self.output_lifetime = Some((name, lifetime.span));
2285 let bound_lifetime = {
2286 let mut lifetime_collector = AsyncFnLifetimeCollector {
2288 currently_bound_lifetimes: Vec::new(),
2289 collect_elided_lifetimes: true,
2290 output_lifetime: None,
2294 hir::intravisit::walk_ty(&mut lifetime_collector, arg);
2296 lifetime_collector.output_lifetime
2299 let span = match output {
2300 FunctionRetTy::Ty(ty) => ty.span,
2301 FunctionRetTy::Default(span) => *span,
2304 let impl_trait_ty = self.lower_existential_impl_trait(
2305 span, Some(fn_def_id), return_impl_trait_id, |this| {
2306 let output_ty = match output {
2307 FunctionRetTy::Ty(ty) => {
2308 this.lower_ty(ty, ImplTraitContext::Existential(Some(fn_def_id)))
2310 FunctionRetTy::Default(span) => {
2311 let LoweredNodeId { node_id: _, hir_id } = this.next_id();
2314 node: hir::TyKind::Tup(hir_vec![]),
2321 let LoweredNodeId { node_id: _, hir_id } = this.next_id();
2322 let future_params = P(hir::GenericArgs {
2324 bindings: hir_vec![hir::TypeBinding {
2325 ident: Ident::from_str(FN_OUTPUT_NAME),
2330 parenthesized: false,
2334 this.std_path(span, &["future", "Future"], Some(future_params), false);
2336 let LoweredNodeId { node_id: _, hir_id } = this.next_id();
2337 let mut bounds = vec![
2338 hir::GenericBound::Trait(
2340 trait_ref: hir::TraitRef {
2344 bound_generic_params: hir_vec![],
2347 hir::TraitBoundModifier::None
2351 if let Some((name, span)) = bound_lifetime {
2352 let LoweredNodeId { node_id: _, hir_id } = this.next_id();
2353 bounds.push(hir::GenericBound::Outlives(
2354 hir::Lifetime { hir_id, name, span }));
2357 hir::HirVec::from(bounds)
2360 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
2361 let impl_trait_ty = P(hir::Ty {
2362 node: impl_trait_ty,
2367 hir::FunctionRetTy::Return(impl_trait_ty)
2370 fn lower_param_bound(
2373 itctx: ImplTraitContext<'_>,
2374 ) -> hir::GenericBound {
2376 GenericBound::Trait(ref ty, modifier) => {
2377 hir::GenericBound::Trait(
2378 self.lower_poly_trait_ref(ty, itctx),
2379 self.lower_trait_bound_modifier(modifier),
2382 GenericBound::Outlives(ref lifetime) => {
2383 hir::GenericBound::Outlives(self.lower_lifetime(lifetime))
2388 fn lower_lifetime(&mut self, l: &Lifetime) -> hir::Lifetime {
2389 let span = l.ident.span;
2391 ident if ident.name == keywords::StaticLifetime.name() =>
2392 self.new_named_lifetime(l.id, span, hir::LifetimeName::Static),
2393 ident if ident.name == keywords::UnderscoreLifetime.name() =>
2394 match self.anonymous_lifetime_mode {
2395 AnonymousLifetimeMode::CreateParameter => {
2396 let fresh_name = self.collect_fresh_in_band_lifetime(span);
2397 self.new_named_lifetime(l.id, span, hir::LifetimeName::Param(fresh_name))
2400 AnonymousLifetimeMode::PassThrough => {
2401 self.new_named_lifetime(l.id, span, hir::LifetimeName::Underscore)
2404 AnonymousLifetimeMode::ReportError => self.new_error_lifetime(Some(l.id), span),
2407 self.maybe_collect_in_band_lifetime(ident);
2408 let param_name = ParamName::Plain(ident);
2409 self.new_named_lifetime(l.id, span, hir::LifetimeName::Param(param_name))
2414 fn new_named_lifetime(
2418 name: hir::LifetimeName,
2419 ) -> hir::Lifetime {
2420 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(id);
2429 fn lower_generic_params(
2431 params: &[GenericParam],
2432 add_bounds: &NodeMap<Vec<GenericBound>>,
2433 mut itctx: ImplTraitContext<'_>,
2434 ) -> hir::HirVec<hir::GenericParam> {
2435 params.iter().map(|param| {
2436 self.lower_generic_param(param, add_bounds, itctx.reborrow())
2440 fn lower_generic_param(&mut self,
2441 param: &GenericParam,
2442 add_bounds: &NodeMap<Vec<GenericBound>>,
2443 mut itctx: ImplTraitContext<'_>)
2444 -> hir::GenericParam {
2445 let mut bounds = self.with_anonymous_lifetime_mode(
2446 AnonymousLifetimeMode::ReportError,
2447 |this| this.lower_param_bounds(¶m.bounds, itctx.reborrow()),
2450 let (name, kind) = match param.kind {
2451 GenericParamKind::Lifetime => {
2452 let was_collecting_in_band = self.is_collecting_in_band_lifetimes;
2453 self.is_collecting_in_band_lifetimes = false;
2455 let lt = self.with_anonymous_lifetime_mode(
2456 AnonymousLifetimeMode::ReportError,
2457 |this| this.lower_lifetime(&Lifetime { id: param.id, ident: param.ident }),
2459 let param_name = match lt.name {
2460 hir::LifetimeName::Param(param_name) => param_name,
2461 hir::LifetimeName::Implicit
2462 | hir::LifetimeName::Underscore
2463 | hir::LifetimeName::Static => hir::ParamName::Plain(lt.name.ident()),
2464 hir::LifetimeName::Error => ParamName::Error,
2467 let kind = hir::GenericParamKind::Lifetime {
2468 kind: hir::LifetimeParamKind::Explicit
2471 self.is_collecting_in_band_lifetimes = was_collecting_in_band;
2475 GenericParamKind::Type { ref default, .. } => {
2476 // Don't expose `Self` (recovered "keyword used as ident" parse error).
2477 // `rustc::ty` expects `Self` to be only used for a trait's `Self`.
2478 // Instead, use `gensym("Self")` to create a distinct name that looks the same.
2479 let ident = if param.ident.name == keywords::SelfUpper.name() {
2480 param.ident.gensym()
2485 let add_bounds = add_bounds.get(¶m.id).map_or(&[][..], |x| &x);
2486 if !add_bounds.is_empty() {
2487 let params = self.lower_param_bounds(add_bounds, itctx.reborrow()).into_iter();
2488 bounds = bounds.into_iter()
2493 let kind = hir::GenericParamKind::Type {
2494 default: default.as_ref().map(|x| {
2495 self.lower_ty(x, ImplTraitContext::disallowed())
2497 synthetic: param.attrs.iter()
2498 .filter(|attr| attr.check_name("rustc_synthetic"))
2499 .map(|_| hir::SyntheticTyParamKind::ImplTrait)
2503 (hir::ParamName::Plain(ident), kind)
2505 GenericParamKind::Const { ref ty } => {
2506 (hir::ParamName::Plain(param.ident), hir::GenericParamKind::Const {
2507 ty: self.lower_ty(&ty, ImplTraitContext::disallowed()),
2512 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(param.id);
2517 span: param.ident.span,
2518 pure_wrt_drop: attr::contains_name(¶m.attrs, "may_dangle"),
2519 attrs: self.lower_attrs(¶m.attrs),
2527 generics: &Generics,
2528 itctx: ImplTraitContext<'_>)
2531 // Collect `?Trait` bounds in where clause and move them to parameter definitions.
2532 // FIXME: this could probably be done with less rightward drift. Also looks like two control
2533 // paths where report_error is called are also the only paths that advance to after
2534 // the match statement, so the error reporting could probably just be moved there.
2535 let mut add_bounds: NodeMap<Vec<_>> = Default::default();
2536 for pred in &generics.where_clause.predicates {
2537 if let WherePredicate::BoundPredicate(ref bound_pred) = *pred {
2538 'next_bound: for bound in &bound_pred.bounds {
2539 if let GenericBound::Trait(_, TraitBoundModifier::Maybe) = *bound {
2540 let report_error = |this: &mut Self| {
2541 this.diagnostic().span_err(
2542 bound_pred.bounded_ty.span,
2543 "`?Trait` bounds are only permitted at the \
2544 point where a type parameter is declared",
2547 // Check if the where clause type is a plain type parameter.
2548 match bound_pred.bounded_ty.node {
2549 TyKind::Path(None, ref path)
2550 if path.segments.len() == 1
2551 && bound_pred.bound_generic_params.is_empty() =>
2553 if let Some(Def::TyParam(def_id)) = self.resolver
2554 .get_resolution(bound_pred.bounded_ty.id)
2555 .map(|d| d.base_def())
2557 if let Some(node_id) =
2558 self.resolver.definitions().as_local_node_id(def_id)
2560 for param in &generics.params {
2562 GenericParamKind::Type { .. } => {
2563 if node_id == param.id {
2564 add_bounds.entry(param.id)
2566 .push(bound.clone());
2567 continue 'next_bound;
2577 _ => report_error(self),
2585 params: self.lower_generic_params(&generics.params, &add_bounds, itctx),
2586 where_clause: self.lower_where_clause(&generics.where_clause),
2587 span: generics.span,
2591 fn lower_where_clause(&mut self, wc: &WhereClause) -> hir::WhereClause {
2592 self.with_anonymous_lifetime_mode(
2593 AnonymousLifetimeMode::ReportError,
2595 let LoweredNodeId { node_id: _, hir_id } = this.lower_node_id(wc.id);
2599 predicates: wc.predicates
2601 .map(|predicate| this.lower_where_predicate(predicate))
2608 fn lower_where_predicate(&mut self, pred: &WherePredicate) -> hir::WherePredicate {
2610 WherePredicate::BoundPredicate(WhereBoundPredicate {
2611 ref bound_generic_params,
2616 self.with_in_scope_lifetime_defs(
2617 &bound_generic_params,
2619 hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
2620 bound_generic_params: this.lower_generic_params(
2621 bound_generic_params,
2622 &NodeMap::default(),
2623 ImplTraitContext::disallowed(),
2625 bounded_ty: this.lower_ty(bounded_ty, ImplTraitContext::disallowed()),
2628 .filter_map(|bound| match *bound {
2629 // Ignore `?Trait` bounds.
2630 // They were copied into type parameters already.
2631 GenericBound::Trait(_, TraitBoundModifier::Maybe) => None,
2632 _ => Some(this.lower_param_bound(
2634 ImplTraitContext::disallowed(),
2643 WherePredicate::RegionPredicate(WhereRegionPredicate {
2647 }) => hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate {
2649 lifetime: self.lower_lifetime(lifetime),
2650 bounds: self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
2652 WherePredicate::EqPredicate(WhereEqPredicate {
2658 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(id);
2660 hir::WherePredicate::EqPredicate(hir::WhereEqPredicate {
2662 lhs_ty: self.lower_ty(lhs_ty, ImplTraitContext::disallowed()),
2663 rhs_ty: self.lower_ty(rhs_ty, ImplTraitContext::disallowed()),
2670 fn lower_variant_data(&mut self, vdata: &VariantData) -> hir::VariantData {
2672 VariantData::Struct(ref fields, id, recovered) => {
2673 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(id);
2675 hir::VariantData::Struct(
2679 .map(|f| self.lower_struct_field(f))
2685 VariantData::Tuple(ref fields, id) => {
2686 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(id);
2688 hir::VariantData::Tuple(
2692 .map(|f| self.lower_struct_field(f))
2697 VariantData::Unit(id) => {
2698 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(id);
2700 hir::VariantData::Unit(hir_id)
2705 fn lower_trait_ref(&mut self, p: &TraitRef, itctx: ImplTraitContext<'_>) -> hir::TraitRef {
2706 let path = match self.lower_qpath(p.ref_id, &None, &p.path, ParamMode::Explicit, itctx) {
2707 hir::QPath::Resolved(None, path) => path.and_then(|path| path),
2708 qpath => bug!("lower_trait_ref: unexpected QPath `{:?}`", qpath),
2710 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(p.ref_id);
2717 fn lower_poly_trait_ref(
2720 mut itctx: ImplTraitContext<'_>,
2721 ) -> hir::PolyTraitRef {
2722 let bound_generic_params = self.lower_generic_params(
2723 &p.bound_generic_params,
2724 &NodeMap::default(),
2727 let trait_ref = self.with_parent_impl_lifetime_defs(
2728 &bound_generic_params,
2729 |this| this.lower_trait_ref(&p.trait_ref, itctx),
2733 bound_generic_params,
2739 fn lower_struct_field(&mut self, (index, f): (usize, &StructField)) -> hir::StructField {
2740 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(f.id);
2745 ident: match f.ident {
2746 Some(ident) => ident,
2747 // FIXME(jseyfried): positional field hygiene
2748 None => Ident::new(Symbol::intern(&index.to_string()), f.span),
2750 vis: self.lower_visibility(&f.vis, None),
2751 ty: self.lower_ty(&f.ty, ImplTraitContext::disallowed()),
2752 attrs: self.lower_attrs(&f.attrs),
2756 fn lower_field(&mut self, f: &Field) -> hir::Field {
2757 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
2762 expr: P(self.lower_expr(&f.expr)),
2764 is_shorthand: f.is_shorthand,
2768 fn lower_mt(&mut self, mt: &MutTy, itctx: ImplTraitContext<'_>) -> hir::MutTy {
2770 ty: self.lower_ty(&mt.ty, itctx),
2771 mutbl: self.lower_mutability(mt.mutbl),
2775 fn lower_param_bounds(&mut self, bounds: &[GenericBound], mut itctx: ImplTraitContext<'_>)
2776 -> hir::GenericBounds {
2777 bounds.iter().map(|bound| self.lower_param_bound(bound, itctx.reborrow())).collect()
2780 fn lower_block(&mut self, b: &Block, targeted_by_break: bool) -> P<hir::Block> {
2781 let mut expr = None;
2783 let mut stmts = vec![];
2785 for (index, stmt) in b.stmts.iter().enumerate() {
2786 if index == b.stmts.len() - 1 {
2787 if let StmtKind::Expr(ref e) = stmt.node {
2788 expr = Some(P(self.lower_expr(e)));
2790 stmts.extend(self.lower_stmt(stmt));
2793 stmts.extend(self.lower_stmt(stmt));
2797 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(b.id);
2801 stmts: stmts.into(),
2803 rules: self.lower_block_check_mode(&b.rules),
2809 fn lower_async_body(
2815 self.lower_body(Some(decl), |this| {
2816 if let IsAsync::Async { closure_id, .. } = asyncness {
2817 let async_expr = this.make_async_expr(
2818 CaptureBy::Value, closure_id, None,
2820 let body = this.lower_block(body, false);
2821 this.expr_block(body, ThinVec::new())
2823 this.expr(body.span, async_expr, ThinVec::new())
2825 let body = this.lower_block(body, false);
2826 this.expr_block(body, ThinVec::new())
2835 attrs: &hir::HirVec<Attribute>,
2836 vis: &mut hir::Visibility,
2838 ) -> hir::ItemKind {
2840 ItemKind::ExternCrate(orig_name) => hir::ItemKind::ExternCrate(orig_name),
2841 ItemKind::Use(ref use_tree) => {
2842 // Start with an empty prefix
2845 span: use_tree.span,
2848 self.lower_use_tree(use_tree, &prefix, id, vis, ident, attrs)
2850 ItemKind::Static(ref t, m, ref e) => {
2851 let value = self.lower_body(None, |this| this.lower_expr(e));
2852 hir::ItemKind::Static(
2855 if self.sess.features_untracked().impl_trait_in_bindings {
2856 ImplTraitContext::Existential(None)
2858 ImplTraitContext::Disallowed(ImplTraitPosition::Binding)
2861 self.lower_mutability(m),
2865 ItemKind::Const(ref t, ref e) => {
2866 let value = self.lower_body(None, |this| this.lower_expr(e));
2867 hir::ItemKind::Const(
2870 if self.sess.features_untracked().impl_trait_in_bindings {
2871 ImplTraitContext::Existential(None)
2873 ImplTraitContext::Disallowed(ImplTraitPosition::Binding)
2879 ItemKind::Fn(ref decl, header, ref generics, ref body) => {
2880 let fn_def_id = self.resolver.definitions().local_def_id(id);
2881 self.with_new_scopes(|this| {
2882 // Note: we don't need to change the return type from `T` to
2883 // `impl Future<Output = T>` here because lower_body
2884 // only cares about the input argument patterns in the function
2885 // declaration (decl), not the return types.
2886 let body_id = this.lower_async_body(decl, header.asyncness.node, body);
2888 let (generics, fn_decl) = this.add_in_band_defs(
2891 AnonymousLifetimeMode::PassThrough,
2892 |this, idty| this.lower_fn_decl(
2894 Some((fn_def_id, idty)),
2896 header.asyncness.node.opt_return_id()
2902 this.lower_fn_header(header),
2908 ItemKind::Mod(ref m) => hir::ItemKind::Mod(self.lower_mod(m)),
2909 ItemKind::ForeignMod(ref nm) => hir::ItemKind::ForeignMod(self.lower_foreign_mod(nm)),
2910 ItemKind::GlobalAsm(ref ga) => hir::ItemKind::GlobalAsm(self.lower_global_asm(ga)),
2911 ItemKind::Ty(ref t, ref generics) => hir::ItemKind::Ty(
2912 self.lower_ty(t, ImplTraitContext::disallowed()),
2913 self.lower_generics(generics, ImplTraitContext::disallowed()),
2915 ItemKind::Existential(ref b, ref generics) => hir::ItemKind::Existential(hir::ExistTy {
2916 generics: self.lower_generics(generics, ImplTraitContext::disallowed()),
2917 bounds: self.lower_param_bounds(b, ImplTraitContext::disallowed()),
2918 impl_trait_fn: None,
2920 ItemKind::Enum(ref enum_definition, ref generics) => hir::ItemKind::Enum(
2922 variants: enum_definition
2925 .map(|x| self.lower_variant(x))
2928 self.lower_generics(generics, ImplTraitContext::disallowed()),
2930 ItemKind::Struct(ref struct_def, ref generics) => {
2931 let struct_def = self.lower_variant_data(struct_def);
2932 hir::ItemKind::Struct(
2934 self.lower_generics(generics, ImplTraitContext::disallowed()),
2937 ItemKind::Union(ref vdata, ref generics) => {
2938 let vdata = self.lower_variant_data(vdata);
2939 hir::ItemKind::Union(
2941 self.lower_generics(generics, ImplTraitContext::disallowed()),
2953 let def_id = self.resolver.definitions().local_def_id(id);
2955 // Lower the "impl header" first. This ordering is important
2956 // for in-band lifetimes! Consider `'a` here:
2958 // impl Foo<'a> for u32 {
2959 // fn method(&'a self) { .. }
2962 // Because we start by lowering the `Foo<'a> for u32`
2963 // part, we will add `'a` to the list of generics on
2964 // the impl. When we then encounter it later in the
2965 // method, it will not be considered an in-band
2966 // lifetime to be added, but rather a reference to a
2968 let lowered_trait_impl_id = self.lower_node_id(id).hir_id;
2969 let (generics, (trait_ref, lowered_ty)) = self.add_in_band_defs(
2972 AnonymousLifetimeMode::CreateParameter,
2974 let trait_ref = trait_ref.as_ref().map(|trait_ref| {
2975 this.lower_trait_ref(trait_ref, ImplTraitContext::disallowed())
2978 if let Some(ref trait_ref) = trait_ref {
2979 if let Def::Trait(def_id) = trait_ref.path.def {
2980 this.trait_impls.entry(def_id).or_default().push(
2981 lowered_trait_impl_id);
2985 let lowered_ty = this.lower_ty(ty, ImplTraitContext::disallowed());
2987 (trait_ref, lowered_ty)
2991 let new_impl_items = self.with_in_scope_lifetime_defs(
2992 &ast_generics.params,
2996 .map(|item| this.lower_impl_item_ref(item))
3001 hir::ItemKind::Impl(
3002 self.lower_unsafety(unsafety),
3003 self.lower_impl_polarity(polarity),
3004 self.lower_defaultness(defaultness, true /* [1] */),
3011 ItemKind::Trait(is_auto, unsafety, ref generics, ref bounds, ref items) => {
3012 let bounds = self.lower_param_bounds(bounds, ImplTraitContext::disallowed());
3015 .map(|item| self.lower_trait_item_ref(item))
3017 hir::ItemKind::Trait(
3018 self.lower_is_auto(is_auto),
3019 self.lower_unsafety(unsafety),
3020 self.lower_generics(generics, ImplTraitContext::disallowed()),
3025 ItemKind::TraitAlias(ref generics, ref bounds) => hir::ItemKind::TraitAlias(
3026 self.lower_generics(generics, ImplTraitContext::disallowed()),
3027 self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
3029 ItemKind::MacroDef(..) | ItemKind::Mac(..) => panic!("Shouldn't still be around"),
3032 // [1] `defaultness.has_value()` is never called for an `impl`, always `true` in order to
3033 // not cause an assertion failure inside the `lower_defaultness` function.
3041 vis: &mut hir::Visibility,
3043 attrs: &hir::HirVec<Attribute>,
3044 ) -> hir::ItemKind {
3045 debug!("lower_use_tree(tree={:?})", tree);
3046 debug!("lower_use_tree: vis = {:?}", vis);
3048 let path = &tree.prefix;
3049 let segments = prefix
3052 .chain(path.segments.iter())
3057 UseTreeKind::Simple(rename, id1, id2) => {
3058 *ident = tree.ident();
3060 // First, apply the prefix to the path.
3061 let mut path = Path {
3066 // Correctly resolve `self` imports.
3067 if path.segments.len() > 1
3068 && path.segments.last().unwrap().ident.name == keywords::SelfLower.name()
3070 let _ = path.segments.pop();
3071 if rename.is_none() {
3072 *ident = path.segments.last().unwrap().ident;
3076 let parent_def_index = self.current_hir_id_owner.last().unwrap().0;
3077 let mut defs = self.expect_full_def_from_use(id);
3078 // We want to return *something* from this function, so hold onto the first item
3080 let ret_def = defs.next().unwrap_or(Def::Err);
3082 // Here, we are looping over namespaces, if they exist for the definition
3083 // being imported. We only handle type and value namespaces because we
3084 // won't be dealing with macros in the rest of the compiler.
3085 // Essentially a single `use` which imports two names is desugared into
3087 for (def, &new_node_id) in defs.zip([id1, id2].iter()) {
3088 let vis = vis.clone();
3089 let ident = ident.clone();
3090 let mut path = path.clone();
3091 for seg in &mut path.segments {
3092 seg.id = self.sess.next_node_id();
3094 let span = path.span;
3095 self.resolver.definitions().create_def_with_parent(
3099 DefIndexAddressSpace::High,
3102 self.allocate_hir_id_counter(new_node_id, &path);
3104 self.with_hir_id_owner(new_node_id, |this| {
3105 let new_id = this.lower_node_id(new_node_id);
3107 this.lower_path_extra(def, &path, ParamMode::Explicit, None);
3108 let item = hir::ItemKind::Use(P(path), hir::UseKind::Single);
3109 let vis_kind = match vis.node {
3110 hir::VisibilityKind::Public => hir::VisibilityKind::Public,
3111 hir::VisibilityKind::Crate(sugar) => hir::VisibilityKind::Crate(sugar),
3112 hir::VisibilityKind::Inherited => hir::VisibilityKind::Inherited,
3113 hir::VisibilityKind::Restricted { ref path, hir_id: _ } => {
3114 let id = this.next_id();
3115 let path = this.renumber_segment_ids(path);
3116 hir::VisibilityKind::Restricted {
3122 let vis = respan(vis.span, vis_kind);
3127 hir_id: new_id.hir_id,
3129 attrs: attrs.clone(),
3139 P(self.lower_path_extra(ret_def, &path, ParamMode::Explicit, None));
3140 hir::ItemKind::Use(path, hir::UseKind::Single)
3142 UseTreeKind::Glob => {
3143 let path = P(self.lower_path(
3149 ParamMode::Explicit,
3151 hir::ItemKind::Use(path, hir::UseKind::Glob)
3153 UseTreeKind::Nested(ref trees) => {
3154 // Nested imports are desugared into simple imports.
3155 // So, if we start with
3158 // pub(x) use foo::{a, b};
3161 // we will create three items:
3164 // pub(x) use foo::a;
3165 // pub(x) use foo::b;
3166 // pub(x) use foo::{}; // <-- this is called the `ListStem`
3169 // The first two are produced by recursively invoking
3170 // `lower_use_tree` (and indeed there may be things
3171 // like `use foo::{a::{b, c}}` and so forth). They
3172 // wind up being directly added to
3173 // `self.items`. However, the structure of this
3174 // function also requires us to return one item, and
3175 // for that we return the `{}` import (called the
3180 span: prefix.span.to(path.span),
3183 // Add all the nested `PathListItem`s to the HIR.
3184 for &(ref use_tree, id) in trees {
3185 self.allocate_hir_id_counter(id, &use_tree);
3190 } = self.lower_node_id(id);
3192 let mut vis = vis.clone();
3193 let mut ident = ident.clone();
3194 let mut prefix = prefix.clone();
3196 // Give the segments new node-ids since they are being cloned.
3197 for seg in &mut prefix.segments {
3198 seg.id = self.sess.next_node_id();
3201 // Each `use` import is an item and thus are owners of the
3202 // names in the path. Up to this point the nested import is
3203 // the current owner, since we want each desugared import to
3204 // own its own names, we have to adjust the owner before
3205 // lowering the rest of the import.
3206 self.with_hir_id_owner(new_id, |this| {
3207 let item = this.lower_use_tree(use_tree,
3214 let vis_kind = match vis.node {
3215 hir::VisibilityKind::Public => hir::VisibilityKind::Public,
3216 hir::VisibilityKind::Crate(sugar) => hir::VisibilityKind::Crate(sugar),
3217 hir::VisibilityKind::Inherited => hir::VisibilityKind::Inherited,
3218 hir::VisibilityKind::Restricted { ref path, hir_id: _ } => {
3219 let id = this.next_id();
3220 let path = this.renumber_segment_ids(path);
3221 hir::VisibilityKind::Restricted {
3227 let vis = respan(vis.span, vis_kind);
3234 attrs: attrs.clone(),
3237 span: use_tree.span,
3243 // Subtle and a bit hacky: we lower the privacy level
3244 // of the list stem to "private" most of the time, but
3245 // not for "restricted" paths. The key thing is that
3246 // we don't want it to stay as `pub` (with no caveats)
3247 // because that affects rustdoc and also the lints
3248 // about `pub` items. But we can't *always* make it
3249 // private -- particularly not for restricted paths --
3250 // because it contains node-ids that would then be
3251 // unused, failing the check that HirIds are "densely
3254 hir::VisibilityKind::Public |
3255 hir::VisibilityKind::Crate(_) |
3256 hir::VisibilityKind::Inherited => {
3257 *vis = respan(prefix.span.shrink_to_lo(), hir::VisibilityKind::Inherited);
3259 hir::VisibilityKind::Restricted { .. } => {
3260 // Do nothing here, as described in the comment on the match.
3264 let def = self.expect_full_def_from_use(id).next().unwrap_or(Def::Err);
3265 let path = P(self.lower_path_extra(def, &prefix, ParamMode::Explicit, None));
3266 hir::ItemKind::Use(path, hir::UseKind::ListStem)
3271 /// Paths like the visibility path in `pub(super) use foo::{bar, baz}` are repeated
3272 /// many times in the HIR tree; for each occurrence, we need to assign distinct
3273 /// `NodeId`s. (See, e.g., #56128.)
3274 fn renumber_segment_ids(&mut self, path: &P<hir::Path>) -> P<hir::Path> {
3275 debug!("renumber_segment_ids(path = {:?})", path);
3276 let mut path = path.clone();
3277 for seg in path.segments.iter_mut() {
3278 if seg.hir_id.is_some() {
3279 seg.hir_id = Some(self.next_id().hir_id);
3285 fn lower_trait_item(&mut self, i: &TraitItem) -> hir::TraitItem {
3286 let LoweredNodeId { node_id, hir_id } = self.lower_node_id(i.id);
3287 let trait_item_def_id = self.resolver.definitions().local_def_id(node_id);
3289 let (generics, node) = match i.node {
3290 TraitItemKind::Const(ref ty, ref default) => (
3291 self.lower_generics(&i.generics, ImplTraitContext::disallowed()),
3292 hir::TraitItemKind::Const(
3293 self.lower_ty(ty, ImplTraitContext::disallowed()),
3296 .map(|x| self.lower_body(None, |this| this.lower_expr(x))),
3299 TraitItemKind::Method(ref sig, None) => {
3300 let names = self.lower_fn_args_to_names(&sig.decl);
3301 let (generics, sig) = self.lower_method_sig(
3308 (generics, hir::TraitItemKind::Method(sig, hir::TraitMethod::Required(names)))
3310 TraitItemKind::Method(ref sig, Some(ref body)) => {
3311 let body_id = self.lower_body(Some(&sig.decl), |this| {
3312 let body = this.lower_block(body, false);
3313 this.expr_block(body, ThinVec::new())
3315 let (generics, sig) = self.lower_method_sig(
3322 (generics, hir::TraitItemKind::Method(sig, hir::TraitMethod::Provided(body_id)))
3324 TraitItemKind::Type(ref bounds, ref default) => (
3325 self.lower_generics(&i.generics, ImplTraitContext::disallowed()),
3326 hir::TraitItemKind::Type(
3327 self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
3330 .map(|x| self.lower_ty(x, ImplTraitContext::disallowed())),
3333 TraitItemKind::Macro(..) => panic!("Shouldn't exist any more"),
3339 attrs: self.lower_attrs(&i.attrs),
3346 fn lower_trait_item_ref(&mut self, i: &TraitItem) -> hir::TraitItemRef {
3347 let (kind, has_default) = match i.node {
3348 TraitItemKind::Const(_, ref default) => {
3349 (hir::AssociatedItemKind::Const, default.is_some())
3351 TraitItemKind::Type(_, ref default) => {
3352 (hir::AssociatedItemKind::Type, default.is_some())
3354 TraitItemKind::Method(ref sig, ref default) => (
3355 hir::AssociatedItemKind::Method {
3356 has_self: sig.decl.has_self(),
3360 TraitItemKind::Macro(..) => unimplemented!(),
3363 id: hir::TraitItemId { hir_id: self.lower_node_id(i.id).hir_id },
3366 defaultness: self.lower_defaultness(Defaultness::Default, has_default),
3371 fn lower_impl_item(&mut self, i: &ImplItem) -> hir::ImplItem {
3372 let LoweredNodeId { node_id, hir_id } = self.lower_node_id(i.id);
3373 let impl_item_def_id = self.resolver.definitions().local_def_id(node_id);
3375 let (generics, node) = match i.node {
3376 ImplItemKind::Const(ref ty, ref expr) => {
3377 let body_id = self.lower_body(None, |this| this.lower_expr(expr));
3379 self.lower_generics(&i.generics, ImplTraitContext::disallowed()),
3380 hir::ImplItemKind::Const(
3381 self.lower_ty(ty, ImplTraitContext::disallowed()),
3386 ImplItemKind::Method(ref sig, ref body) => {
3387 let body_id = self.lower_async_body(&sig.decl, sig.header.asyncness.node, body);
3388 let impl_trait_return_allow = !self.is_in_trait_impl;
3389 let (generics, sig) = self.lower_method_sig(
3393 impl_trait_return_allow,
3394 sig.header.asyncness.node.opt_return_id(),
3396 (generics, hir::ImplItemKind::Method(sig, body_id))
3398 ImplItemKind::Type(ref ty) => (
3399 self.lower_generics(&i.generics, ImplTraitContext::disallowed()),
3400 hir::ImplItemKind::Type(self.lower_ty(ty, ImplTraitContext::disallowed())),
3402 ImplItemKind::Existential(ref bounds) => (
3403 self.lower_generics(&i.generics, ImplTraitContext::disallowed()),
3404 hir::ImplItemKind::Existential(
3405 self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
3408 ImplItemKind::Macro(..) => panic!("Shouldn't exist any more"),
3414 attrs: self.lower_attrs(&i.attrs),
3416 vis: self.lower_visibility(&i.vis, None),
3417 defaultness: self.lower_defaultness(i.defaultness, true /* [1] */),
3422 // [1] since `default impl` is not yet implemented, this is always true in impls
3425 fn lower_impl_item_ref(&mut self, i: &ImplItem) -> hir::ImplItemRef {
3427 id: hir::ImplItemId { hir_id: self.lower_node_id(i.id).hir_id },
3430 vis: self.lower_visibility(&i.vis, Some(i.id)),
3431 defaultness: self.lower_defaultness(i.defaultness, true /* [1] */),
3432 kind: match i.node {
3433 ImplItemKind::Const(..) => hir::AssociatedItemKind::Const,
3434 ImplItemKind::Type(..) => hir::AssociatedItemKind::Type,
3435 ImplItemKind::Existential(..) => hir::AssociatedItemKind::Existential,
3436 ImplItemKind::Method(ref sig, _) => hir::AssociatedItemKind::Method {
3437 has_self: sig.decl.has_self(),
3439 ImplItemKind::Macro(..) => unimplemented!(),
3443 // [1] since `default impl` is not yet implemented, this is always true in impls
3446 fn lower_mod(&mut self, m: &Mod) -> hir::Mod {
3449 item_ids: m.items.iter().flat_map(|x| self.lower_item_id(x)).collect(),
3453 fn lower_item_id(&mut self, i: &Item) -> SmallVec<[hir::ItemId; 1]> {
3455 ItemKind::Use(ref use_tree) => {
3456 let mut vec = smallvec![hir::ItemId { id: i.id }];
3457 self.lower_item_id_use_tree(use_tree, i.id, &mut vec);
3460 ItemKind::MacroDef(..) => SmallVec::new(),
3462 ItemKind::Impl(.., None, _, _) => smallvec![hir::ItemId { id: i.id }],
3463 ItemKind::Static(ref ty, ..) => {
3464 let mut ids = smallvec![hir::ItemId { id: i.id }];
3465 if self.sess.features_untracked().impl_trait_in_bindings {
3466 let mut visitor = ImplTraitTypeIdVisitor { ids: &mut ids };
3467 visitor.visit_ty(ty);
3471 ItemKind::Const(ref ty, ..) => {
3472 let mut ids = smallvec![hir::ItemId { id: i.id }];
3473 if self.sess.features_untracked().impl_trait_in_bindings {
3474 let mut visitor = ImplTraitTypeIdVisitor { ids: &mut ids };
3475 visitor.visit_ty(ty);
3479 _ => smallvec![hir::ItemId { id: i.id }],
3483 fn lower_item_id_use_tree(&mut self,
3486 vec: &mut SmallVec<[hir::ItemId; 1]>)
3489 UseTreeKind::Nested(ref nested_vec) => for &(ref nested, id) in nested_vec {
3490 vec.push(hir::ItemId { id });
3491 self.lower_item_id_use_tree(nested, id, vec);
3493 UseTreeKind::Glob => {}
3494 UseTreeKind::Simple(_, id1, id2) => {
3495 for (_, &id) in self.expect_full_def_from_use(base_id)
3497 .zip([id1, id2].iter())
3499 vec.push(hir::ItemId { id });
3505 pub fn lower_item(&mut self, i: &Item) -> Option<hir::Item> {
3506 let mut ident = i.ident;
3507 let mut vis = self.lower_visibility(&i.vis, None);
3508 let attrs = self.lower_attrs(&i.attrs);
3509 if let ItemKind::MacroDef(ref def) = i.node {
3510 if !def.legacy || attr::contains_name(&i.attrs, "macro_export") ||
3511 attr::contains_name(&i.attrs, "rustc_doc_only_macro") {
3512 let body = self.lower_token_stream(def.stream());
3513 let hir_id = self.lower_node_id(i.id).hir_id;
3514 self.exported_macros.push(hir::MacroDef {
3527 let node = self.lower_item_kind(i.id, &mut ident, &attrs, &mut vis, &i.node);
3529 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(i.id);
3541 fn lower_foreign_item(&mut self, i: &ForeignItem) -> hir::ForeignItem {
3542 let LoweredNodeId { node_id, hir_id } = self.lower_node_id(i.id);
3543 let def_id = self.resolver.definitions().local_def_id(node_id);
3547 attrs: self.lower_attrs(&i.attrs),
3548 node: match i.node {
3549 ForeignItemKind::Fn(ref fdec, ref generics) => {
3550 let (generics, (fn_dec, fn_args)) = self.add_in_band_defs(
3553 AnonymousLifetimeMode::PassThrough,
3556 // Disallow impl Trait in foreign items
3557 this.lower_fn_decl(fdec, None, false, None),
3558 this.lower_fn_args_to_names(fdec),
3563 hir::ForeignItemKind::Fn(fn_dec, fn_args, generics)
3565 ForeignItemKind::Static(ref t, m) => {
3566 hir::ForeignItemKind::Static(
3567 self.lower_ty(t, ImplTraitContext::disallowed()), m)
3569 ForeignItemKind::Ty => hir::ForeignItemKind::Type,
3570 ForeignItemKind::Macro(_) => panic!("shouldn't exist here"),
3572 vis: self.lower_visibility(&i.vis, None),
3577 fn lower_method_sig(
3579 generics: &Generics,
3582 impl_trait_return_allow: bool,
3583 is_async: Option<NodeId>,
3584 ) -> (hir::Generics, hir::MethodSig) {
3585 let header = self.lower_fn_header(sig.header);
3586 let (generics, decl) = self.add_in_band_defs(
3589 AnonymousLifetimeMode::PassThrough,
3590 |this, idty| this.lower_fn_decl(
3592 Some((fn_def_id, idty)),
3593 impl_trait_return_allow,
3597 (generics, hir::MethodSig { header, decl })
3600 fn lower_is_auto(&mut self, a: IsAuto) -> hir::IsAuto {
3602 IsAuto::Yes => hir::IsAuto::Yes,
3603 IsAuto::No => hir::IsAuto::No,
3607 fn lower_fn_header(&mut self, h: FnHeader) -> hir::FnHeader {
3609 unsafety: self.lower_unsafety(h.unsafety),
3610 asyncness: self.lower_asyncness(h.asyncness.node),
3611 constness: self.lower_constness(h.constness),
3616 fn lower_unsafety(&mut self, u: Unsafety) -> hir::Unsafety {
3618 Unsafety::Unsafe => hir::Unsafety::Unsafe,
3619 Unsafety::Normal => hir::Unsafety::Normal,
3623 fn lower_constness(&mut self, c: Spanned<Constness>) -> hir::Constness {
3625 Constness::Const => hir::Constness::Const,
3626 Constness::NotConst => hir::Constness::NotConst,
3630 fn lower_asyncness(&mut self, a: IsAsync) -> hir::IsAsync {
3632 IsAsync::Async { .. } => hir::IsAsync::Async,
3633 IsAsync::NotAsync => hir::IsAsync::NotAsync,
3637 fn lower_unop(&mut self, u: UnOp) -> hir::UnOp {
3639 UnOp::Deref => hir::UnDeref,
3640 UnOp::Not => hir::UnNot,
3641 UnOp::Neg => hir::UnNeg,
3645 fn lower_binop(&mut self, b: BinOp) -> hir::BinOp {
3647 node: match b.node {
3648 BinOpKind::Add => hir::BinOpKind::Add,
3649 BinOpKind::Sub => hir::BinOpKind::Sub,
3650 BinOpKind::Mul => hir::BinOpKind::Mul,
3651 BinOpKind::Div => hir::BinOpKind::Div,
3652 BinOpKind::Rem => hir::BinOpKind::Rem,
3653 BinOpKind::And => hir::BinOpKind::And,
3654 BinOpKind::Or => hir::BinOpKind::Or,
3655 BinOpKind::BitXor => hir::BinOpKind::BitXor,
3656 BinOpKind::BitAnd => hir::BinOpKind::BitAnd,
3657 BinOpKind::BitOr => hir::BinOpKind::BitOr,
3658 BinOpKind::Shl => hir::BinOpKind::Shl,
3659 BinOpKind::Shr => hir::BinOpKind::Shr,
3660 BinOpKind::Eq => hir::BinOpKind::Eq,
3661 BinOpKind::Lt => hir::BinOpKind::Lt,
3662 BinOpKind::Le => hir::BinOpKind::Le,
3663 BinOpKind::Ne => hir::BinOpKind::Ne,
3664 BinOpKind::Ge => hir::BinOpKind::Ge,
3665 BinOpKind::Gt => hir::BinOpKind::Gt,
3671 fn lower_pat(&mut self, p: &Pat) -> P<hir::Pat> {
3672 let node = match p.node {
3673 PatKind::Wild => hir::PatKind::Wild,
3674 PatKind::Ident(ref binding_mode, ident, ref sub) => {
3675 match self.resolver.get_resolution(p.id).map(|d| d.base_def()) {
3676 // `None` can occur in body-less function signatures
3677 def @ None | def @ Some(Def::Local(_)) => {
3678 let canonical_id = match def {
3679 Some(Def::Local(id)) => id,
3683 hir::PatKind::Binding(
3684 self.lower_binding_mode(binding_mode),
3685 self.lower_node_id(canonical_id).hir_id,
3687 sub.as_ref().map(|x| self.lower_pat(x)),
3690 Some(def) => hir::PatKind::Path(hir::QPath::Resolved(
3695 segments: hir_vec![hir::PathSegment::from_ident(ident)],
3700 PatKind::Lit(ref e) => hir::PatKind::Lit(P(self.lower_expr(e))),
3701 PatKind::TupleStruct(ref path, ref pats, ddpos) => {
3702 let qpath = self.lower_qpath(
3706 ParamMode::Optional,
3707 ImplTraitContext::disallowed(),
3709 hir::PatKind::TupleStruct(
3711 pats.iter().map(|x| self.lower_pat(x)).collect(),
3715 PatKind::Path(ref qself, ref path) => {
3716 let qpath = self.lower_qpath(
3720 ParamMode::Optional,
3721 ImplTraitContext::disallowed(),
3723 hir::PatKind::Path(qpath)
3725 PatKind::Struct(ref path, ref fields, etc) => {
3726 let qpath = self.lower_qpath(
3730 ParamMode::Optional,
3731 ImplTraitContext::disallowed(),
3737 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
3741 node: hir::FieldPat {
3743 ident: f.node.ident,
3744 pat: self.lower_pat(&f.node.pat),
3745 is_shorthand: f.node.is_shorthand,
3750 hir::PatKind::Struct(qpath, fs, etc)
3752 PatKind::Tuple(ref elts, ddpos) => {
3753 hir::PatKind::Tuple(elts.iter().map(|x| self.lower_pat(x)).collect(), ddpos)
3755 PatKind::Box(ref inner) => hir::PatKind::Box(self.lower_pat(inner)),
3756 PatKind::Ref(ref inner, mutbl) => {
3757 hir::PatKind::Ref(self.lower_pat(inner), self.lower_mutability(mutbl))
3759 PatKind::Range(ref e1, ref e2, Spanned { node: ref end, .. }) => hir::PatKind::Range(
3760 P(self.lower_expr(e1)),
3761 P(self.lower_expr(e2)),
3762 self.lower_range_end(end),
3764 PatKind::Slice(ref before, ref slice, ref after) => hir::PatKind::Slice(
3765 before.iter().map(|x| self.lower_pat(x)).collect(),
3766 slice.as_ref().map(|x| self.lower_pat(x)),
3767 after.iter().map(|x| self.lower_pat(x)).collect(),
3769 PatKind::Paren(ref inner) => return self.lower_pat(inner),
3770 PatKind::Mac(_) => panic!("Shouldn't exist here"),
3773 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(p.id);
3781 fn lower_range_end(&mut self, e: &RangeEnd) -> hir::RangeEnd {
3783 RangeEnd::Included(_) => hir::RangeEnd::Included,
3784 RangeEnd::Excluded => hir::RangeEnd::Excluded,
3788 fn lower_anon_const(&mut self, c: &AnonConst) -> hir::AnonConst {
3789 self.with_new_scopes(|this| {
3790 let LoweredNodeId { node_id: _, hir_id } = this.lower_node_id(c.id);
3793 body: this.lower_body(None, |this| this.lower_expr(&c.value)),
3798 fn lower_expr(&mut self, e: &Expr) -> hir::Expr {
3799 let kind = match e.node {
3800 ExprKind::Box(ref inner) => hir::ExprKind::Box(P(self.lower_expr(inner))),
3801 ExprKind::ObsoleteInPlace(..) => {
3802 self.sess.abort_if_errors();
3803 span_bug!(e.span, "encountered ObsoleteInPlace expr during lowering");
3805 ExprKind::Array(ref exprs) => {
3806 hir::ExprKind::Array(exprs.iter().map(|x| self.lower_expr(x)).collect())
3808 ExprKind::Repeat(ref expr, ref count) => {
3809 let expr = P(self.lower_expr(expr));
3810 let count = self.lower_anon_const(count);
3811 hir::ExprKind::Repeat(expr, count)
3813 ExprKind::Tup(ref elts) => {
3814 hir::ExprKind::Tup(elts.iter().map(|x| self.lower_expr(x)).collect())
3816 ExprKind::Call(ref f, ref args) => {
3817 let f = P(self.lower_expr(f));
3818 hir::ExprKind::Call(f, args.iter().map(|x| self.lower_expr(x)).collect())
3820 ExprKind::MethodCall(ref seg, ref args) => {
3821 let hir_seg = P(self.lower_path_segment(
3824 ParamMode::Optional,
3826 ParenthesizedGenericArgs::Err,
3827 ImplTraitContext::disallowed(),
3830 let args = args.iter().map(|x| self.lower_expr(x)).collect();
3831 hir::ExprKind::MethodCall(hir_seg, seg.ident.span, args)
3833 ExprKind::Binary(binop, ref lhs, ref rhs) => {
3834 let binop = self.lower_binop(binop);
3835 let lhs = P(self.lower_expr(lhs));
3836 let rhs = P(self.lower_expr(rhs));
3837 hir::ExprKind::Binary(binop, lhs, rhs)
3839 ExprKind::Unary(op, ref ohs) => {
3840 let op = self.lower_unop(op);
3841 let ohs = P(self.lower_expr(ohs));
3842 hir::ExprKind::Unary(op, ohs)
3844 ExprKind::Lit(ref l) => hir::ExprKind::Lit((*l).clone()),
3845 ExprKind::Cast(ref expr, ref ty) => {
3846 let expr = P(self.lower_expr(expr));
3847 hir::ExprKind::Cast(expr, self.lower_ty(ty, ImplTraitContext::disallowed()))
3849 ExprKind::Type(ref expr, ref ty) => {
3850 let expr = P(self.lower_expr(expr));
3851 hir::ExprKind::Type(expr, self.lower_ty(ty, ImplTraitContext::disallowed()))
3853 ExprKind::AddrOf(m, ref ohs) => {
3854 let m = self.lower_mutability(m);
3855 let ohs = P(self.lower_expr(ohs));
3856 hir::ExprKind::AddrOf(m, ohs)
3858 // More complicated than you might expect because the else branch
3859 // might be `if let`.
3860 ExprKind::If(ref cond, ref blk, ref else_opt) => {
3861 let else_opt = else_opt.as_ref().map(|els| {
3863 ExprKind::IfLet(..) => {
3864 // Wrap the `if let` expr in a block.
3865 let span = els.span;
3866 let els = P(self.lower_expr(els));
3867 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
3868 let blk = P(hir::Block {
3872 rules: hir::DefaultBlock,
3874 targeted_by_break: false,
3876 P(self.expr_block(blk, ThinVec::new()))
3878 _ => P(self.lower_expr(els)),
3882 let then_blk = self.lower_block(blk, false);
3883 let then_expr = self.expr_block(then_blk, ThinVec::new());
3885 hir::ExprKind::If(P(self.lower_expr(cond)), P(then_expr), else_opt)
3887 ExprKind::While(ref cond, ref body, opt_label) => self.with_loop_scope(e.id, |this| {
3888 hir::ExprKind::While(
3889 this.with_loop_condition_scope(|this| P(this.lower_expr(cond))),
3890 this.lower_block(body, false),
3891 this.lower_label(opt_label),
3894 ExprKind::Loop(ref body, opt_label) => self.with_loop_scope(e.id, |this| {
3895 hir::ExprKind::Loop(
3896 this.lower_block(body, false),
3897 this.lower_label(opt_label),
3898 hir::LoopSource::Loop,
3901 ExprKind::TryBlock(ref body) => {
3902 self.with_catch_scope(body.id, |this| {
3903 let unstable_span = this.mark_span_with_reason(
3904 CompilerDesugaringKind::TryBlock,
3907 Symbol::intern("try_trait"),
3910 let mut block = this.lower_block(body, true).into_inner();
3911 let tail = block.expr.take().map_or_else(
3913 let LoweredNodeId { node_id: _, hir_id } = this.next_id();
3914 let span = this.sess.source_map().end_point(unstable_span);
3917 node: hir::ExprKind::Tup(hir_vec![]),
3918 attrs: ThinVec::new(),
3922 |x: P<hir::Expr>| x.into_inner(),
3924 block.expr = Some(this.wrap_in_try_constructor(
3925 "from_ok", tail, unstable_span));
3926 hir::ExprKind::Block(P(block), None)
3929 ExprKind::Match(ref expr, ref arms) => hir::ExprKind::Match(
3930 P(self.lower_expr(expr)),
3931 arms.iter().map(|x| self.lower_arm(x)).collect(),
3932 hir::MatchSource::Normal,
3934 ExprKind::Async(capture_clause, closure_node_id, ref block) => {
3935 self.make_async_expr(capture_clause, closure_node_id, None, |this| {
3936 this.with_new_scopes(|this| {
3937 let block = this.lower_block(block, false);
3938 this.expr_block(block, ThinVec::new())
3943 capture_clause, asyncness, movability, ref decl, ref body, fn_decl_span
3945 if let IsAsync::Async { closure_id, .. } = asyncness {
3946 let outer_decl = FnDecl {
3947 inputs: decl.inputs.clone(),
3948 output: FunctionRetTy::Default(fn_decl_span),
3951 // We need to lower the declaration outside the new scope, because we
3952 // have to conserve the state of being inside a loop condition for the
3953 // closure argument types.
3954 let fn_decl = self.lower_fn_decl(&outer_decl, None, false, None);
3956 self.with_new_scopes(|this| {
3957 // FIXME(cramertj): allow `async` non-`move` closures with arguments.
3958 if capture_clause == CaptureBy::Ref &&
3959 !decl.inputs.is_empty()
3965 "`async` non-`move` closures with arguments \
3966 are not currently supported",
3968 .help("consider using `let` statements to manually capture \
3969 variables by reference before entering an \
3970 `async move` closure")
3974 // Transform `async |x: u8| -> X { ... }` into
3975 // `|x: u8| future_from_generator(|| -> X { ... })`.
3976 let body_id = this.lower_body(Some(&outer_decl), |this| {
3977 let async_ret_ty = if let FunctionRetTy::Ty(ty) = &decl.output {
3980 let async_body = this.make_async_expr(
3981 capture_clause, closure_id, async_ret_ty,
3983 this.with_new_scopes(|this| this.lower_expr(body))
3985 this.expr(fn_decl_span, async_body, ThinVec::new())
3987 hir::ExprKind::Closure(
3988 this.lower_capture_clause(capture_clause),
3996 // Lower outside new scope to preserve `is_in_loop_condition`.
3997 let fn_decl = self.lower_fn_decl(decl, None, false, None);
3999 self.with_new_scopes(|this| {
4000 let mut is_generator = false;
4001 let body_id = this.lower_body(Some(decl), |this| {
4002 let e = this.lower_expr(body);
4003 is_generator = this.is_generator;
4006 let generator_option = if is_generator {
4007 if !decl.inputs.is_empty() {
4012 "generators cannot have explicit arguments"
4014 this.sess.abort_if_errors();
4016 Some(match movability {
4017 Movability::Movable => hir::GeneratorMovability::Movable,
4018 Movability::Static => hir::GeneratorMovability::Static,
4021 if movability == Movability::Static {
4026 "closures cannot be static"
4031 hir::ExprKind::Closure(
4032 this.lower_capture_clause(capture_clause),
4041 ExprKind::Block(ref blk, opt_label) => {
4042 hir::ExprKind::Block(self.lower_block(blk,
4043 opt_label.is_some()),
4044 self.lower_label(opt_label))
4046 ExprKind::Assign(ref el, ref er) => {
4047 hir::ExprKind::Assign(P(self.lower_expr(el)), P(self.lower_expr(er)))
4049 ExprKind::AssignOp(op, ref el, ref er) => hir::ExprKind::AssignOp(
4050 self.lower_binop(op),
4051 P(self.lower_expr(el)),
4052 P(self.lower_expr(er)),
4054 ExprKind::Field(ref el, ident) => hir::ExprKind::Field(P(self.lower_expr(el)), ident),
4055 ExprKind::Index(ref el, ref er) => {
4056 hir::ExprKind::Index(P(self.lower_expr(el)), P(self.lower_expr(er)))
4058 // Desugar `<start>..=<end>` into `std::ops::RangeInclusive::new(<start>, <end>)`.
4059 ExprKind::Range(Some(ref e1), Some(ref e2), RangeLimits::Closed) => {
4060 let id = self.next_id();
4061 let e1 = self.lower_expr(e1);
4062 let e2 = self.lower_expr(e2);
4063 let ty_path = P(self.std_path(e.span, &["ops", "RangeInclusive"], None, false));
4064 let ty = P(self.ty_path(id, e.span, hir::QPath::Resolved(None, ty_path)));
4065 let new_seg = P(hir::PathSegment::from_ident(Ident::from_str("new")));
4066 let new_path = hir::QPath::TypeRelative(ty, new_seg);
4067 let new = P(self.expr(e.span, hir::ExprKind::Path(new_path), ThinVec::new()));
4068 hir::ExprKind::Call(new, hir_vec![e1, e2])
4070 ExprKind::Range(ref e1, ref e2, lims) => {
4071 use syntax::ast::RangeLimits::*;
4073 let path = match (e1, e2, lims) {
4074 (&None, &None, HalfOpen) => "RangeFull",
4075 (&Some(..), &None, HalfOpen) => "RangeFrom",
4076 (&None, &Some(..), HalfOpen) => "RangeTo",
4077 (&Some(..), &Some(..), HalfOpen) => "Range",
4078 (&None, &Some(..), Closed) => "RangeToInclusive",
4079 (&Some(..), &Some(..), Closed) => unreachable!(),
4080 (_, &None, Closed) => self.diagnostic()
4081 .span_fatal(e.span, "inclusive range with no end")
4085 let fields = e1.iter()
4086 .map(|e| ("start", e))
4087 .chain(e2.iter().map(|e| ("end", e)))
4089 let expr = P(self.lower_expr(&e));
4090 let ident = Ident::new(Symbol::intern(s), e.span);
4091 self.field(ident, expr, e.span)
4093 .collect::<P<[hir::Field]>>();
4095 let is_unit = fields.is_empty();
4096 let struct_path = ["ops", path];
4097 let struct_path = self.std_path(e.span, &struct_path, None, is_unit);
4098 let struct_path = hir::QPath::Resolved(None, P(struct_path));
4100 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(e.id);
4105 hir::ExprKind::Path(struct_path)
4107 hir::ExprKind::Struct(P(struct_path), fields, None)
4110 attrs: e.attrs.clone(),
4113 ExprKind::Path(ref qself, ref path) => {
4114 let qpath = self.lower_qpath(
4118 ParamMode::Optional,
4119 ImplTraitContext::disallowed(),
4121 hir::ExprKind::Path(qpath)
4123 ExprKind::Break(opt_label, ref opt_expr) => {
4124 let destination = if self.is_in_loop_condition && opt_label.is_none() {
4127 target_id: Err(hir::LoopIdError::UnlabeledCfInWhileCondition).into(),
4130 self.lower_loop_destination(opt_label.map(|label| (e.id, label)))
4132 hir::ExprKind::Break(
4134 opt_expr.as_ref().map(|x| P(self.lower_expr(x))),
4137 ExprKind::Continue(opt_label) => {
4138 hir::ExprKind::Continue(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)))
4147 ExprKind::Ret(ref e) => hir::ExprKind::Ret(e.as_ref().map(|x| P(self.lower_expr(x)))),
4148 ExprKind::InlineAsm(ref asm) => {
4149 let hir_asm = hir::InlineAsm {
4150 inputs: asm.inputs.iter().map(|&(ref c, _)| c.clone()).collect(),
4151 outputs: asm.outputs
4153 .map(|out| hir::InlineAsmOutput {
4154 constraint: out.constraint.clone(),
4156 is_indirect: out.is_indirect,
4157 span: out.expr.span,
4160 asm: asm.asm.clone(),
4161 asm_str_style: asm.asm_str_style,
4162 clobbers: asm.clobbers.clone().into(),
4163 volatile: asm.volatile,
4164 alignstack: asm.alignstack,
4165 dialect: asm.dialect,
4168 let outputs = asm.outputs
4170 .map(|out| self.lower_expr(&out.expr))
4172 let inputs = asm.inputs
4174 .map(|&(_, ref input)| self.lower_expr(input))
4176 hir::ExprKind::InlineAsm(P(hir_asm), outputs, inputs)
4178 ExprKind::Struct(ref path, ref fields, ref maybe_expr) => hir::ExprKind::Struct(
4183 ParamMode::Optional,
4184 ImplTraitContext::disallowed(),
4186 fields.iter().map(|x| self.lower_field(x)).collect(),
4187 maybe_expr.as_ref().map(|x| P(self.lower_expr(x))),
4189 ExprKind::Paren(ref ex) => {
4190 let mut ex = self.lower_expr(ex);
4191 // Include parens in span, but only if it is a super-span.
4192 if e.span.contains(ex.span) {
4195 // Merge attributes into the inner expression.
4196 let mut attrs = e.attrs.clone();
4197 attrs.extend::<Vec<_>>(ex.attrs.into());
4202 ExprKind::Yield(ref opt_expr) => {
4203 self.is_generator = true;
4206 .map(|x| self.lower_expr(x))
4208 self.expr(e.span, hir::ExprKind::Tup(hir_vec![]), ThinVec::new())
4210 hir::ExprKind::Yield(P(expr))
4213 ExprKind::Err => hir::ExprKind::Err,
4215 // Desugar `ExprIfLet`
4216 // from: `if let <pat> = <sub_expr> <body> [<else_opt>]`
4217 ExprKind::IfLet(ref pats, ref sub_expr, ref body, ref else_opt) => {
4220 // match <sub_expr> {
4222 // _ => [<else_opt> | ()]
4225 let mut arms = vec![];
4227 // `<pat> => <body>`
4229 let body = self.lower_block(body, false);
4230 let body_expr = P(self.expr_block(body, ThinVec::new()));
4231 let pats = pats.iter().map(|pat| self.lower_pat(pat)).collect();
4232 arms.push(self.arm(pats, body_expr));
4235 // _ => [<else_opt>|()]
4237 let wildcard_arm: Option<&Expr> = else_opt.as_ref().map(|p| &**p);
4238 let wildcard_pattern = self.pat_wild(e.span);
4239 let body = if let Some(else_expr) = wildcard_arm {
4240 P(self.lower_expr(else_expr))
4242 self.expr_tuple(e.span, hir_vec![])
4244 arms.push(self.arm(hir_vec![wildcard_pattern], body));
4247 let contains_else_clause = else_opt.is_some();
4249 let sub_expr = P(self.lower_expr(sub_expr));
4251 hir::ExprKind::Match(
4254 hir::MatchSource::IfLetDesugar {
4255 contains_else_clause,
4260 // Desugar `ExprWhileLet`
4261 // from: `[opt_ident]: while let <pat> = <sub_expr> <body>`
4262 ExprKind::WhileLet(ref pats, ref sub_expr, ref body, opt_label) => {
4265 // [opt_ident]: loop {
4266 // match <sub_expr> {
4272 // Note that the block AND the condition are evaluated in the loop scope.
4273 // This is done to allow `break` from inside the condition of the loop.
4274 let (body, break_expr, sub_expr) = self.with_loop_scope(e.id, |this| {
4276 this.lower_block(body, false),
4277 this.expr_break(e.span, ThinVec::new()),
4278 this.with_loop_condition_scope(|this| P(this.lower_expr(sub_expr))),
4282 // `<pat> => <body>`
4284 let body_expr = P(self.expr_block(body, ThinVec::new()));
4285 let pats = pats.iter().map(|pat| self.lower_pat(pat)).collect();
4286 self.arm(pats, body_expr)
4291 let pat_under = self.pat_wild(e.span);
4292 self.arm(hir_vec![pat_under], break_expr)
4295 // `match <sub_expr> { ... }`
4296 let arms = hir_vec![pat_arm, break_arm];
4297 let match_expr = self.expr(
4299 hir::ExprKind::Match(sub_expr, arms, hir::MatchSource::WhileLetDesugar),
4303 // `[opt_ident]: loop { ... }`
4304 let loop_block = P(self.block_expr(P(match_expr)));
4305 let loop_expr = hir::ExprKind::Loop(
4307 self.lower_label(opt_label),
4308 hir::LoopSource::WhileLet,
4310 // Add attributes to the outer returned expr node.
4314 // Desugar `ExprForLoop`
4315 // from: `[opt_ident]: for <pat> in <head> <body>`
4316 ExprKind::ForLoop(ref pat, ref head, ref body, opt_label) => {
4320 // let result = match ::std::iter::IntoIterator::into_iter(<head>) {
4322 // [opt_ident]: loop {
4324 // match ::std::iter::Iterator::next(&mut iter) {
4325 // ::std::option::Option::Some(val) => __next = val,
4326 // ::std::option::Option::None => break
4328 // let <pat> = __next;
4329 // StmtKind::Expr(<body>);
4337 let head = self.lower_expr(head);
4338 let head_sp = head.span;
4339 let desugared_span = self.mark_span_with_reason(
4340 CompilerDesugaringKind::ForLoop,
4345 let iter = self.str_to_ident("iter");
4347 let next_ident = self.str_to_ident("__next");
4348 let (next_pat, next_pat_nid) = self.pat_ident_binding_mode(
4351 hir::BindingAnnotation::Mutable,
4354 // `::std::option::Option::Some(val) => next = val`
4356 let val_ident = self.str_to_ident("val");
4357 let (val_pat, val_pat_nid) = self.pat_ident(pat.span, val_ident);
4358 let val_expr = P(self.expr_ident(pat.span, val_ident, val_pat_nid));
4359 let next_expr = P(self.expr_ident(pat.span, next_ident, next_pat_nid));
4360 let assign = P(self.expr(
4362 hir::ExprKind::Assign(next_expr, val_expr),
4365 let some_pat = self.pat_some(pat.span, val_pat);
4366 self.arm(hir_vec![some_pat], assign)
4369 // `::std::option::Option::None => break`
4372 self.with_loop_scope(e.id, |this| this.expr_break(e.span, ThinVec::new()));
4373 let pat = self.pat_none(e.span);
4374 self.arm(hir_vec![pat], break_expr)
4378 let (iter_pat, iter_pat_nid) = self.pat_ident_binding_mode(
4381 hir::BindingAnnotation::Mutable
4384 // `match ::std::iter::Iterator::next(&mut iter) { ... }`
4386 let iter = P(self.expr_ident(head_sp, iter, iter_pat_nid));
4387 let ref_mut_iter = self.expr_mut_addr_of(head_sp, iter);
4388 let next_path = &["iter", "Iterator", "next"];
4389 let next_path = P(self.expr_std_path(head_sp, next_path, None, ThinVec::new()));
4390 let next_expr = P(self.expr_call(head_sp, next_path, hir_vec![ref_mut_iter]));
4391 let arms = hir_vec![pat_arm, break_arm];
4395 hir::ExprKind::Match(
4398 hir::MatchSource::ForLoopDesugar
4403 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
4404 let match_stmt = hir::Stmt {
4406 node: hir::StmtKind::Expr(match_expr),
4410 let next_expr = P(self.expr_ident(head_sp, next_ident, next_pat_nid));
4413 let next_let = self.stmt_let_pat(
4417 hir::LocalSource::ForLoopDesugar,
4420 // `let <pat> = __next`
4421 let pat = self.lower_pat(pat);
4422 let pat_let = self.stmt_let_pat(
4426 hir::LocalSource::ForLoopDesugar,
4429 let body_block = self.with_loop_scope(e.id, |this| this.lower_block(body, false));
4430 let body_expr = P(self.expr_block(body_block, ThinVec::new()));
4431 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
4432 let body_stmt = hir::Stmt {
4434 node: hir::StmtKind::Expr(body_expr),
4438 let loop_block = P(self.block_all(
4440 hir_vec![next_let, match_stmt, pat_let, body_stmt],
4444 // `[opt_ident]: loop { ... }`
4445 let loop_expr = hir::ExprKind::Loop(
4447 self.lower_label(opt_label),
4448 hir::LoopSource::ForLoop,
4450 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(e.id);
4451 let loop_expr = P(hir::Expr {
4455 attrs: ThinVec::new(),
4458 // `mut iter => { ... }`
4459 let iter_arm = self.arm(hir_vec![iter_pat], loop_expr);
4461 // `match ::std::iter::IntoIterator::into_iter(<head>) { ... }`
4462 let into_iter_expr = {
4463 let into_iter_path = &["iter", "IntoIterator", "into_iter"];
4464 let into_iter = P(self.expr_std_path(
4465 head_sp, into_iter_path, None, ThinVec::new()));
4466 P(self.expr_call(head_sp, into_iter, hir_vec![head]))
4469 let match_expr = P(self.expr_match(
4473 hir::MatchSource::ForLoopDesugar,
4476 // `{ let _result = ...; _result }`
4477 // Underscore prevents an `unused_variables` lint if the head diverges.
4478 let result_ident = self.str_to_ident("_result");
4479 let (let_stmt, let_stmt_binding) =
4480 self.stmt_let(e.span, false, result_ident, match_expr);
4482 let result = P(self.expr_ident(e.span, result_ident, let_stmt_binding));
4483 let block = P(self.block_all(e.span, hir_vec![let_stmt], Some(result)));
4484 // Add the attributes to the outer returned expr node.
4485 return self.expr_block(block, e.attrs.clone());
4488 // Desugar `ExprKind::Try`
4490 ExprKind::Try(ref sub_expr) => {
4493 // match Try::into_result(<expr>) {
4494 // Ok(val) => #[allow(unreachable_code)] val,
4495 // Err(err) => #[allow(unreachable_code)]
4496 // // If there is an enclosing `catch {...}`
4497 // break 'catch_target Try::from_error(From::from(err)),
4499 // return Try::from_error(From::from(err)),
4502 let unstable_span = self.mark_span_with_reason(
4503 CompilerDesugaringKind::QuestionMark,
4506 Symbol::intern("try_trait")
4510 // `Try::into_result(<expr>)`
4513 let sub_expr = self.lower_expr(sub_expr);
4515 let path = &["ops", "Try", "into_result"];
4516 let path = P(self.expr_std_path(
4517 unstable_span, path, None, ThinVec::new()));
4518 P(self.expr_call(e.span, path, hir_vec![sub_expr]))
4521 // `#[allow(unreachable_code)]`
4523 // `allow(unreachable_code)`
4525 let allow_ident = Ident::from_str("allow").with_span_pos(e.span);
4526 let uc_ident = Ident::from_str("unreachable_code").with_span_pos(e.span);
4527 let uc_nested = attr::mk_nested_word_item(uc_ident);
4528 attr::mk_list_item(e.span, allow_ident, vec![uc_nested])
4530 attr::mk_spanned_attr_outer(e.span, attr::mk_attr_id(), allow)
4532 let attrs = vec![attr];
4534 // `Ok(val) => #[allow(unreachable_code)] val,`
4536 let val_ident = self.str_to_ident("val");
4537 let (val_pat, val_pat_nid) = self.pat_ident(e.span, val_ident);
4538 let val_expr = P(self.expr_ident_with_attrs(
4542 ThinVec::from(attrs.clone()),
4544 let ok_pat = self.pat_ok(e.span, val_pat);
4546 self.arm(hir_vec![ok_pat], val_expr)
4549 // `Err(err) => #[allow(unreachable_code)]
4550 // return Try::from_error(From::from(err)),`
4552 let err_ident = self.str_to_ident("err");
4553 let (err_local, err_local_nid) = self.pat_ident(e.span, err_ident);
4555 let path = &["convert", "From", "from"];
4556 let from = P(self.expr_std_path(
4557 e.span, path, None, ThinVec::new()));
4558 let err_expr = self.expr_ident(e.span, err_ident, err_local_nid);
4560 self.expr_call(e.span, from, hir_vec![err_expr])
4563 self.wrap_in_try_constructor("from_error", from_expr, unstable_span);
4564 let thin_attrs = ThinVec::from(attrs);
4565 let catch_scope = self.catch_scopes.last().map(|x| *x);
4566 let ret_expr = if let Some(catch_node) = catch_scope {
4567 let target_id = Ok(self.lower_node_id(catch_node).hir_id);
4570 hir::ExprKind::Break(
4575 Some(from_err_expr),
4580 P(self.expr(e.span, hir::ExprKind::Ret(Some(from_err_expr)), thin_attrs))
4583 let err_pat = self.pat_err(e.span, err_local);
4584 self.arm(hir_vec![err_pat], ret_expr)
4587 hir::ExprKind::Match(
4589 hir_vec![err_arm, ok_arm],
4590 hir::MatchSource::TryDesugar,
4594 ExprKind::Mac(_) => panic!("Shouldn't exist here"),
4597 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(e.id);
4603 attrs: e.attrs.clone(),
4607 fn lower_stmt(&mut self, s: &Stmt) -> SmallVec<[hir::Stmt; 1]> {
4608 smallvec![match s.node {
4609 StmtKind::Local(ref l) => {
4610 let (l, item_ids) = self.lower_local(l);
4611 let mut ids: SmallVec<[hir::Stmt; 1]> = item_ids
4614 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
4618 node: hir::StmtKind::Item(item_id),
4624 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(s.id);
4628 node: hir::StmtKind::Local(P(l)),
4634 StmtKind::Item(ref it) => {
4635 // Can only use the ID once.
4636 let mut id = Some(s.id);
4637 return self.lower_item_id(it)
4640 let LoweredNodeId { node_id: _, hir_id } = id.take()
4641 .map(|id| self.lower_node_id(id))
4642 .unwrap_or_else(|| self.next_id());
4646 node: hir::StmtKind::Item(item_id),
4652 StmtKind::Expr(ref e) => {
4653 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(s.id);
4657 node: hir::StmtKind::Expr(P(self.lower_expr(e))),
4661 StmtKind::Semi(ref e) => {
4662 let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(s.id);
4666 node: hir::StmtKind::Semi(P(self.lower_expr(e))),
4670 StmtKind::Mac(..) => panic!("Shouldn't exist here"),
4674 fn lower_capture_clause(&mut self, c: CaptureBy) -> hir::CaptureClause {
4676 CaptureBy::Value => hir::CaptureByValue,
4677 CaptureBy::Ref => hir::CaptureByRef,
4681 /// If an `explicit_owner` is given, this method allocates the `HirId` in
4682 /// the address space of that item instead of the item currently being
4683 /// lowered. This can happen during `lower_impl_item_ref()` where we need to
4684 /// lower a `Visibility` value although we haven't lowered the owning
4685 /// `ImplItem` in question yet.
4686 fn lower_visibility(
4689 explicit_owner: Option<NodeId>,
4690 ) -> hir::Visibility {
4691 let node = match v.node {
4692 VisibilityKind::Public => hir::VisibilityKind::Public,
4693 VisibilityKind::Crate(sugar) => hir::VisibilityKind::Crate(sugar),
4694 VisibilityKind::Restricted { ref path, id } => {
4695 debug!("lower_visibility: restricted path id = {:?}", id);
4696 let lowered_id = if let Some(owner) = explicit_owner {
4697 self.lower_node_id_with_owner(id, owner)
4699 self.lower_node_id(id)
4701 let def = self.expect_full_def(id);
4702 hir::VisibilityKind::Restricted {
4703 path: P(self.lower_path_extra(
4706 ParamMode::Explicit,
4709 hir_id: lowered_id.hir_id,
4712 VisibilityKind::Inherited => hir::VisibilityKind::Inherited,
4714 respan(v.span, node)
4717 fn lower_defaultness(&self, d: Defaultness, has_value: bool) -> hir::Defaultness {
4719 Defaultness::Default => hir::Defaultness::Default {
4720 has_value: has_value,
4722 Defaultness::Final => {
4724 hir::Defaultness::Final
4729 fn lower_block_check_mode(&mut self, b: &BlockCheckMode) -> hir::BlockCheckMode {
4731 BlockCheckMode::Default => hir::DefaultBlock,
4732 BlockCheckMode::Unsafe(u) => hir::UnsafeBlock(self.lower_unsafe_source(u)),
4736 fn lower_binding_mode(&mut self, b: &BindingMode) -> hir::BindingAnnotation {
4738 BindingMode::ByValue(Mutability::Immutable) => hir::BindingAnnotation::Unannotated,
4739 BindingMode::ByRef(Mutability::Immutable) => hir::BindingAnnotation::Ref,
4740 BindingMode::ByValue(Mutability::Mutable) => hir::BindingAnnotation::Mutable,
4741 BindingMode::ByRef(Mutability::Mutable) => hir::BindingAnnotation::RefMut,
4745 fn lower_unsafe_source(&mut self, u: UnsafeSource) -> hir::UnsafeSource {
4747 CompilerGenerated => hir::CompilerGenerated,
4748 UserProvided => hir::UserProvided,
4752 fn lower_impl_polarity(&mut self, i: ImplPolarity) -> hir::ImplPolarity {
4754 ImplPolarity::Positive => hir::ImplPolarity::Positive,
4755 ImplPolarity::Negative => hir::ImplPolarity::Negative,
4759 fn lower_trait_bound_modifier(&mut self, f: TraitBoundModifier) -> hir::TraitBoundModifier {
4761 TraitBoundModifier::None => hir::TraitBoundModifier::None,
4762 TraitBoundModifier::Maybe => hir::TraitBoundModifier::Maybe,
4766 // Helper methods for building HIR.
4768 fn arm(&mut self, pats: hir::HirVec<P<hir::Pat>>, expr: P<hir::Expr>) -> hir::Arm {
4777 fn field(&mut self, ident: Ident, expr: P<hir::Expr>, span: Span) -> hir::Field {
4778 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
4785 is_shorthand: false,
4789 fn expr_break(&mut self, span: Span, attrs: ThinVec<Attribute>) -> P<hir::Expr> {
4790 let expr_break = hir::ExprKind::Break(self.lower_loop_destination(None), None);
4791 P(self.expr(span, expr_break, attrs))
4798 args: hir::HirVec<hir::Expr>,
4800 self.expr(span, hir::ExprKind::Call(e, args), ThinVec::new())
4803 fn expr_ident(&mut self, span: Span, ident: Ident, binding: NodeId) -> hir::Expr {
4804 self.expr_ident_with_attrs(span, ident, binding, ThinVec::new())
4807 fn expr_ident_with_attrs(
4812 attrs: ThinVec<Attribute>,
4814 let expr_path = hir::ExprKind::Path(hir::QPath::Resolved(
4818 def: Def::Local(binding),
4819 segments: hir_vec![hir::PathSegment::from_ident(ident)],
4823 self.expr(span, expr_path, attrs)
4826 fn expr_mut_addr_of(&mut self, span: Span, e: P<hir::Expr>) -> hir::Expr {
4827 self.expr(span, hir::ExprKind::AddrOf(hir::MutMutable, e), ThinVec::new())
4833 components: &[&str],
4834 params: Option<P<hir::GenericArgs>>,
4835 attrs: ThinVec<Attribute>,
4837 let path = self.std_path(span, components, params, true);
4840 hir::ExprKind::Path(hir::QPath::Resolved(None, P(path))),
4849 arms: hir::HirVec<hir::Arm>,
4850 source: hir::MatchSource,
4852 self.expr(span, hir::ExprKind::Match(arg, arms, source), ThinVec::new())
4855 fn expr_block(&mut self, b: P<hir::Block>, attrs: ThinVec<Attribute>) -> hir::Expr {
4856 self.expr(b.span, hir::ExprKind::Block(b, None), attrs)
4859 fn expr_tuple(&mut self, sp: Span, exprs: hir::HirVec<hir::Expr>) -> P<hir::Expr> {
4860 P(self.expr(sp, hir::ExprKind::Tup(exprs), ThinVec::new()))
4863 fn expr(&mut self, span: Span, node: hir::ExprKind, attrs: ThinVec<Attribute>) -> hir::Expr {
4864 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
4876 ex: Option<P<hir::Expr>>,
4878 source: hir::LocalSource,
4880 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
4882 let local = hir::Local {
4888 attrs: ThinVec::new(),
4892 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
4895 node: hir::StmtKind::Local(P(local)),
4906 ) -> (hir::Stmt, NodeId) {
4907 let (pat, pat_nid) = if mutbl {
4908 self.pat_ident_binding_mode(sp, ident, hir::BindingAnnotation::Mutable)
4910 self.pat_ident(sp, ident)
4914 self.stmt_let_pat(sp, Some(ex), pat, hir::LocalSource::Normal),
4919 fn block_expr(&mut self, expr: P<hir::Expr>) -> hir::Block {
4920 self.block_all(expr.span, hir::HirVec::new(), Some(expr))
4926 stmts: hir::HirVec<hir::Stmt>,
4927 expr: Option<P<hir::Expr>>,
4929 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
4935 rules: hir::DefaultBlock,
4937 targeted_by_break: false,
4941 fn pat_ok(&mut self, span: Span, pat: P<hir::Pat>) -> P<hir::Pat> {
4942 self.pat_std_enum(span, &["result", "Result", "Ok"], hir_vec![pat])
4945 fn pat_err(&mut self, span: Span, pat: P<hir::Pat>) -> P<hir::Pat> {
4946 self.pat_std_enum(span, &["result", "Result", "Err"], hir_vec![pat])
4949 fn pat_some(&mut self, span: Span, pat: P<hir::Pat>) -> P<hir::Pat> {
4950 self.pat_std_enum(span, &["option", "Option", "Some"], hir_vec![pat])
4953 fn pat_none(&mut self, span: Span) -> P<hir::Pat> {
4954 self.pat_std_enum(span, &["option", "Option", "None"], hir_vec![])
4960 components: &[&str],
4961 subpats: hir::HirVec<P<hir::Pat>>,
4963 let path = self.std_path(span, components, None, true);
4964 let qpath = hir::QPath::Resolved(None, P(path));
4965 let pt = if subpats.is_empty() {
4966 hir::PatKind::Path(qpath)
4968 hir::PatKind::TupleStruct(qpath, subpats, None)
4973 fn pat_ident(&mut self, span: Span, ident: Ident) -> (P<hir::Pat>, NodeId) {
4974 self.pat_ident_binding_mode(span, ident, hir::BindingAnnotation::Unannotated)
4977 fn pat_ident_binding_mode(
4981 bm: hir::BindingAnnotation,
4982 ) -> (P<hir::Pat>, NodeId) {
4983 let LoweredNodeId { node_id, hir_id } = self.next_id();
4988 node: hir::PatKind::Binding(bm, hir_id, ident.with_span_pos(span), None),
4995 fn pat_wild(&mut self, span: Span) -> P<hir::Pat> {
4996 self.pat(span, hir::PatKind::Wild)
4999 fn pat(&mut self, span: Span, pat: hir::PatKind) -> P<hir::Pat> {
5000 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
5008 /// Given suffix ["b","c","d"], returns path `::std::b::c::d` when
5009 /// `fld.cx.use_std`, and `::core::b::c::d` otherwise.
5010 /// The path is also resolved according to `is_value`.
5014 components: &[&str],
5015 params: Option<P<hir::GenericArgs>>,
5018 let mut path = self.resolver
5019 .resolve_str_path(span, self.crate_root, components, is_value);
5020 path.segments.last_mut().unwrap().args = params;
5023 for seg in path.segments.iter_mut() {
5024 if seg.hir_id.is_some() {
5025 seg.hir_id = Some(self.next_id().hir_id);
5031 fn ty_path(&mut self, id: LoweredNodeId, span: Span, qpath: hir::QPath) -> hir::Ty {
5033 let node = match qpath {
5034 hir::QPath::Resolved(None, path) => {
5035 // Turn trait object paths into `TyKind::TraitObject` instead.
5037 Def::Trait(_) | Def::TraitAlias(_) => {
5038 let principal = hir::PolyTraitRef {
5039 bound_generic_params: hir::HirVec::new(),
5040 trait_ref: hir::TraitRef {
5041 path: path.and_then(|path| path),
5042 hir_ref_id: id.hir_id,
5047 // The original ID is taken by the `PolyTraitRef`,
5048 // so the `Ty` itself needs a different one.
5049 id = self.next_id();
5050 hir::TyKind::TraitObject(hir_vec![principal], self.elided_dyn_bound(span))
5052 _ => hir::TyKind::Path(hir::QPath::Resolved(None, path)),
5055 _ => hir::TyKind::Path(qpath),
5064 /// Invoked to create the lifetime argument for a type `&T`
5065 /// with no explicit lifetime.
5066 fn elided_ref_lifetime(&mut self, span: Span) -> hir::Lifetime {
5067 match self.anonymous_lifetime_mode {
5068 // Intercept when we are in an impl header and introduce an in-band lifetime.
5069 // Hence `impl Foo for &u32` becomes `impl<'f> Foo for &'f u32` for some fresh
5071 AnonymousLifetimeMode::CreateParameter => {
5072 let fresh_name = self.collect_fresh_in_band_lifetime(span);
5073 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
5077 name: hir::LifetimeName::Param(fresh_name),
5081 AnonymousLifetimeMode::ReportError => self.new_error_lifetime(None, span),
5083 AnonymousLifetimeMode::PassThrough => self.new_implicit_lifetime(span),
5087 /// Report an error on illegal use of `'_` or a `&T` with no explicit lifetime;
5088 /// return a "error lifetime".
5089 fn new_error_lifetime(&mut self, id: Option<NodeId>, span: Span) -> hir::Lifetime {
5090 let (id, msg, label) = match id {
5091 Some(id) => (id, "`'_` cannot be used here", "`'_` is a reserved lifetime name"),
5094 self.next_id().node_id,
5095 "`&` without an explicit lifetime name cannot be used here",
5096 "explicit lifetime name needed here",
5100 let mut err = struct_span_err!(
5107 err.span_label(span, label);
5110 self.new_named_lifetime(id, span, hir::LifetimeName::Error)
5113 /// Invoked to create the lifetime argument(s) for a path like
5114 /// `std::cell::Ref<T>`; note that implicit lifetimes in these
5115 /// sorts of cases are deprecated. This may therefore report a warning or an
5116 /// error, depending on the mode.
5117 fn elided_path_lifetimes(&mut self, span: Span, count: usize) -> P<[hir::Lifetime]> {
5118 match self.anonymous_lifetime_mode {
5119 // N.B., We intentionally ignore the create-parameter mode here
5120 // and instead "pass through" to resolve-lifetimes, which will then
5121 // report an error. This is because we don't want to support
5122 // impl elision for deprecated forms like
5124 // impl Foo for std::cell::Ref<u32> // note lack of '_
5125 AnonymousLifetimeMode::CreateParameter => {}
5127 AnonymousLifetimeMode::ReportError => {
5129 .map(|_| self.new_error_lifetime(None, span))
5133 // This is the normal case.
5134 AnonymousLifetimeMode::PassThrough => {}
5138 .map(|_| self.new_implicit_lifetime(span))
5142 /// Invoked to create the lifetime argument(s) for an elided trait object
5143 /// bound, like the bound in `Box<dyn Debug>`. This method is not invoked
5144 /// when the bound is written, even if it is written with `'_` like in
5145 /// `Box<dyn Debug + '_>`. In those cases, `lower_lifetime` is invoked.
5146 fn elided_dyn_bound(&mut self, span: Span) -> hir::Lifetime {
5147 match self.anonymous_lifetime_mode {
5148 // NB. We intentionally ignore the create-parameter mode here.
5149 // and instead "pass through" to resolve-lifetimes, which will apply
5150 // the object-lifetime-defaulting rules. Elided object lifetime defaults
5151 // do not act like other elided lifetimes. In other words, given this:
5153 // impl Foo for Box<dyn Debug>
5155 // we do not introduce a fresh `'_` to serve as the bound, but instead
5156 // ultimately translate to the equivalent of:
5158 // impl Foo for Box<dyn Debug + 'static>
5160 // `resolve_lifetime` has the code to make that happen.
5161 AnonymousLifetimeMode::CreateParameter => {}
5163 AnonymousLifetimeMode::ReportError => {
5164 // ReportError applies to explicit use of `'_`.
5167 // This is the normal case.
5168 AnonymousLifetimeMode::PassThrough => {}
5171 self.new_implicit_lifetime(span)
5174 fn new_implicit_lifetime(&mut self, span: Span) -> hir::Lifetime {
5175 let LoweredNodeId { node_id: _, hir_id } = self.next_id();
5180 name: hir::LifetimeName::Implicit,
5184 fn maybe_lint_bare_trait(&self, span: Span, id: NodeId, is_global: bool) {
5185 self.sess.buffer_lint_with_diagnostic(
5186 builtin::BARE_TRAIT_OBJECTS,
5189 "trait objects without an explicit `dyn` are deprecated",
5190 builtin::BuiltinLintDiagnostics::BareTraitObject(span, is_global),
5194 fn wrap_in_try_constructor(
5196 method: &'static str,
5198 unstable_span: Span,
5200 let path = &["ops", "Try", method];
5201 let from_err = P(self.expr_std_path(unstable_span, path, None,
5203 P(self.expr_call(e.span, from_err, hir_vec![e]))
5207 fn body_ids(bodies: &BTreeMap<hir::BodyId, hir::Body>) -> Vec<hir::BodyId> {
5208 // Sorting by span ensures that we get things in order within a
5209 // file, and also puts the files in a sensible order.
5210 let mut body_ids: Vec<_> = bodies.keys().cloned().collect();
5211 body_ids.sort_by_key(|b| bodies[b].value.span);