// ignore-tidy-filelength //! Lowers the AST to the HIR. //! //! Since the AST and HIR are fairly similar, this is mostly a simple procedure, //! much like a fold. Where lowering involves a bit more work things get more //! interesting and there are some invariants you should know about. These mostly //! concern spans and IDs. //! //! Spans are assigned to AST nodes during parsing and then are modified during //! expansion to indicate the origin of a node and the process it went through //! being expanded. IDs are assigned to AST nodes just before lowering. //! //! For the simpler lowering steps, IDs and spans should be preserved. Unlike //! expansion we do not preserve the process of lowering in the spans, so spans //! should not be modified here. When creating a new node (as opposed to //! 'folding' an existing one), then you create a new ID using `next_id()`. //! //! You must ensure that IDs are unique. That means that you should only use the //! ID from an AST node in a single HIR node (you can assume that AST node-IDs //! are unique). Every new node must have a unique ID. Avoid cloning HIR nodes. //! If you do, you must then set the new node's ID to a fresh one. //! //! Spans are used for error messages and for tools to map semantics back to //! source code. It is therefore not as important with spans as IDs to be strict //! about use (you can't break the compiler by screwing up a span). Obviously, a //! HIR node can only have a single span. But multiple nodes can have the same //! span and spans don't need to be kept in order, etc. Where code is preserved //! by lowering, it should have the same span as in the AST. Where HIR nodes are //! new it is probably best to give a span for the whole AST node being lowered. //! All nodes should have real spans, don't use dummy spans. Tools are likely to //! get confused if the spans from leaf AST nodes occur in multiple places //! in the HIR, especially for multiple identifiers. mod expr; mod item; use crate::dep_graph::DepGraph; use crate::hir::{self, ParamName}; use crate::hir::HirVec; use crate::hir::map::{DefKey, DefPathData, Definitions}; use crate::hir::def_id::{DefId, DefIndex, CRATE_DEF_INDEX}; use crate::hir::def::{Namespace, Res, DefKind, PartialRes, PerNS}; use crate::hir::{GenericArg, ConstArg}; use crate::hir::ptr::P; use crate::lint; use crate::lint::builtin::{self, PARENTHESIZED_PARAMS_IN_TYPES_AND_MODULES, ELIDED_LIFETIMES_IN_PATHS}; use crate::middle::cstore::CrateStore; use crate::session::Session; use crate::session::config::nightly_options; use crate::util::common::FN_OUTPUT_NAME; use crate::util::nodemap::{DefIdMap, NodeMap}; use errors::Applicability; use rustc_data_structures::fx::FxHashSet; use rustc_index::vec::IndexVec; use rustc_data_structures::thin_vec::ThinVec; use rustc_data_structures::sync::Lrc; use std::collections::BTreeMap; use std::mem; use smallvec::SmallVec; use syntax::attr; use syntax::ast; use syntax::ptr::P as AstP; use syntax::ast::*; use syntax::errors; use syntax::expand::SpecialDerives; use syntax::print::pprust; use syntax::parse::token::{self, Nonterminal, Token}; use syntax::tokenstream::{TokenStream, TokenTree}; use syntax::sess::ParseSess; use syntax::source_map::{respan, ExpnData, ExpnKind, DesugaringKind, Spanned}; use syntax::symbol::{kw, sym, Symbol}; use syntax::visit::{self, Visitor}; use syntax_pos::hygiene::ExpnId; use syntax_pos::Span; const HIR_ID_COUNTER_LOCKED: u32 = 0xFFFFFFFF; pub struct LoweringContext<'a> { crate_root: Option, /// Used to assign IDs to HIR nodes that do not directly correspond to AST nodes. sess: &'a Session, resolver: &'a mut dyn Resolver, /// HACK(Centril): there is a cyclic dependency between the parser and lowering /// if we don't have this function pointer. To avoid that dependency so that /// librustc is independent of the parser, we use dynamic dispatch here. nt_to_tokenstream: NtToTokenstream, /// The items being lowered are collected here. items: BTreeMap, trait_items: BTreeMap, impl_items: BTreeMap, bodies: BTreeMap, exported_macros: Vec, non_exported_macro_attrs: Vec, trait_impls: BTreeMap>, modules: BTreeMap, generator_kind: Option, /// Used to get the current `fn`'s def span to point to when using `await` /// outside of an `async fn`. current_item: Option, catch_scopes: Vec, loop_scopes: Vec, is_in_loop_condition: bool, is_in_trait_impl: bool, is_in_dyn_type: bool, /// What to do when we encounter either an "anonymous lifetime /// reference". The term "anonymous" is meant to encompass both /// `'_` lifetimes as well as fully elided cases where nothing is /// written at all (e.g., `&T` or `std::cell::Ref`). anonymous_lifetime_mode: AnonymousLifetimeMode, /// Used to create lifetime definitions from in-band lifetime usages. /// e.g., `fn foo(x: &'x u8) -> &'x u8` to `fn foo<'x>(x: &'x u8) -> &'x u8` /// When a named lifetime is encountered in a function or impl header and /// has not been defined /// (i.e., it doesn't appear in the in_scope_lifetimes list), it is added /// to this list. The results of this list are then added to the list of /// lifetime definitions in the corresponding impl or function generics. lifetimes_to_define: Vec<(Span, ParamName)>, /// `true` if in-band lifetimes are being collected. This is used to /// indicate whether or not we're in a place where new lifetimes will result /// in in-band lifetime definitions, such a function or an impl header, /// including implicit lifetimes from `impl_header_lifetime_elision`. is_collecting_in_band_lifetimes: bool, /// Currently in-scope lifetimes defined in impl headers, fn headers, or HRTB. /// When `is_collectin_in_band_lifetimes` is true, each lifetime is checked /// against this list to see if it is already in-scope, or if a definition /// needs to be created for it. /// /// We always store a `modern()` version of the param-name in this /// vector. in_scope_lifetimes: Vec, current_module: hir::HirId, type_def_lifetime_params: DefIdMap, current_hir_id_owner: Vec<(DefIndex, u32)>, item_local_id_counters: NodeMap, node_id_to_hir_id: IndexVec, allow_try_trait: Option>, allow_gen_future: Option>, } pub trait Resolver { fn cstore(&self) -> &dyn CrateStore; /// Obtains resolution for a `NodeId` with a single resolution. fn get_partial_res(&mut self, id: NodeId) -> Option; /// Obtains per-namespace resolutions for `use` statement with the given `NodeId`. fn get_import_res(&mut self, id: NodeId) -> PerNS>>; /// Obtains resolution for a label with the given `NodeId`. fn get_label_res(&mut self, id: NodeId) -> Option; /// We must keep the set of definitions up to date as we add nodes that weren't in the AST. /// This should only return `None` during testing. fn definitions(&mut self) -> &mut Definitions; /// Given suffix `["b", "c", "d"]`, creates an AST path for `[::crate_root]::b::c::d` and /// resolves it based on `is_value`. fn resolve_str_path( &mut self, span: Span, crate_root: Option, components: &[Symbol], ns: Namespace, ) -> (ast::Path, Res); fn has_derives(&self, node_id: NodeId, derives: SpecialDerives) -> bool; fn lint_buffer(&mut self) -> &mut lint::LintBuffer; } type NtToTokenstream = fn(&Nonterminal, &ParseSess, Span) -> TokenStream; /// Context of `impl Trait` in code, which determines whether it is allowed in an HIR subtree, /// and if so, what meaning it has. #[derive(Debug)] enum ImplTraitContext<'a> { /// Treat `impl Trait` as shorthand for a new universal generic parameter. /// Example: `fn foo(x: impl Debug)`, where `impl Debug` is conceptually /// equivalent to a fresh universal parameter like `fn foo(x: T)`. /// /// Newly generated parameters should be inserted into the given `Vec`. Universal(&'a mut Vec), /// Treat `impl Trait` as shorthand for a new opaque type. /// Example: `fn foo() -> impl Debug`, where `impl Debug` is conceptually /// equivalent to a new opaque type like `type T = impl Debug; fn foo() -> T`. /// /// We optionally store a `DefId` for the parent item here so we can look up necessary /// information later. It is `None` when no information about the context should be stored /// (e.g., for consts and statics). OpaqueTy(Option /* fn def-ID */), /// `impl Trait` is not accepted in this position. Disallowed(ImplTraitPosition), } /// Position in which `impl Trait` is disallowed. #[derive(Debug, Copy, Clone, PartialEq, Eq)] enum ImplTraitPosition { /// Disallowed in `let` / `const` / `static` bindings. Binding, /// All other posiitons. Other, } impl<'a> ImplTraitContext<'a> { #[inline] fn disallowed() -> Self { ImplTraitContext::Disallowed(ImplTraitPosition::Other) } fn reborrow(&'b mut self) -> ImplTraitContext<'b> { use self::ImplTraitContext::*; match self { Universal(params) => Universal(params), OpaqueTy(fn_def_id) => OpaqueTy(*fn_def_id), Disallowed(pos) => Disallowed(*pos), } } } pub fn lower_crate( sess: &Session, dep_graph: &DepGraph, krate: &Crate, resolver: &mut dyn Resolver, nt_to_tokenstream: NtToTokenstream, ) -> hir::Crate { // We're constructing the HIR here; we don't care what we will // read, since we haven't even constructed the *input* to // incr. comp. yet. dep_graph.assert_ignored(); let _prof_timer = sess.prof.generic_activity("hir_lowering"); LoweringContext { crate_root: sess.parse_sess.injected_crate_name.try_get().copied(), sess, resolver, nt_to_tokenstream, items: BTreeMap::new(), trait_items: BTreeMap::new(), impl_items: BTreeMap::new(), bodies: BTreeMap::new(), trait_impls: BTreeMap::new(), modules: BTreeMap::new(), exported_macros: Vec::new(), non_exported_macro_attrs: Vec::new(), catch_scopes: Vec::new(), loop_scopes: Vec::new(), is_in_loop_condition: false, is_in_trait_impl: false, is_in_dyn_type: false, anonymous_lifetime_mode: AnonymousLifetimeMode::PassThrough, type_def_lifetime_params: Default::default(), current_module: hir::CRATE_HIR_ID, current_hir_id_owner: vec![(CRATE_DEF_INDEX, 0)], item_local_id_counters: Default::default(), node_id_to_hir_id: IndexVec::new(), generator_kind: None, current_item: None, lifetimes_to_define: Vec::new(), is_collecting_in_band_lifetimes: false, in_scope_lifetimes: Vec::new(), allow_try_trait: Some([sym::try_trait][..].into()), allow_gen_future: Some([sym::gen_future][..].into()), }.lower_crate(krate) } #[derive(Copy, Clone, PartialEq)] enum ParamMode { /// Any path in a type context. Explicit, /// Path in a type definition, where the anonymous lifetime `'_` is not allowed. ExplicitNamed, /// The `module::Type` in `module::Type::method` in an expression. Optional, } enum ParenthesizedGenericArgs { Ok, Warn, Err, } /// What to do when we encounter an **anonymous** lifetime /// reference. Anonymous lifetime references come in two flavors. You /// have implicit, or fully elided, references to lifetimes, like the /// one in `&T` or `Ref`, and you have `'_` lifetimes, like `&'_ T` /// or `Ref<'_, T>`. These often behave the same, but not always: /// /// - certain usages of implicit references are deprecated, like /// `Ref`, and we sometimes just give hard errors in those cases /// as well. /// - for object bounds there is a difference: `Box` is not /// the same as `Box`. /// /// We describe the effects of the various modes in terms of three cases: /// /// - **Modern** -- includes all uses of `'_`, but also the lifetime arg /// of a `&` (e.g., the missing lifetime in something like `&T`) /// - **Dyn Bound** -- if you have something like `Box`, /// there is an elided lifetime bound (`Box`). These /// elided bounds follow special rules. Note that this only covers /// cases where *nothing* is written; the `'_` in `Box` is a case of "modern" elision. /// - **Deprecated** -- this coverse cases like `Ref`, where the lifetime /// parameter to ref is completely elided. `Ref<'_, T>` would be the modern, /// non-deprecated equivalent. /// /// Currently, the handling of lifetime elision is somewhat spread out /// between HIR lowering and -- as described below -- the /// `resolve_lifetime` module. Often we "fallthrough" to that code by generating /// an "elided" or "underscore" lifetime name. In the future, we probably want to move /// everything into HIR lowering. #[derive(Copy, Clone, Debug)] enum AnonymousLifetimeMode { /// For **Modern** cases, create a new anonymous region parameter /// and reference that. /// /// For **Dyn Bound** cases, pass responsibility to /// `resolve_lifetime` code. /// /// For **Deprecated** cases, report an error. CreateParameter, /// Give a hard error when either `&` or `'_` is written. Used to /// rule out things like `where T: Foo<'_>`. Does not imply an /// error on default object bounds (e.g., `Box`). ReportError, /// Pass responsibility to `resolve_lifetime` code for all cases. PassThrough, } struct ImplTraitTypeIdVisitor<'a> { ids: &'a mut SmallVec<[NodeId; 1]> } impl<'a, 'b> Visitor<'a> for ImplTraitTypeIdVisitor<'b> { fn visit_ty(&mut self, ty: &'a Ty) { match ty.kind { | TyKind::Typeof(_) | TyKind::BareFn(_) => return, TyKind::ImplTrait(id, _) => self.ids.push(id), _ => {}, } visit::walk_ty(self, ty); } fn visit_path_segment( &mut self, path_span: Span, path_segment: &'v PathSegment, ) { if let Some(ref p) = path_segment.args { if let GenericArgs::Parenthesized(_) = **p { return; } } visit::walk_path_segment(self, path_span, path_segment) } } impl<'a> LoweringContext<'a> { fn lower_crate(mut self, c: &Crate) -> hir::Crate { /// Full-crate AST visitor that inserts into a fresh /// `LoweringContext` any information that may be /// needed from arbitrary locations in the crate, /// e.g., the number of lifetime generic parameters /// declared for every type and trait definition. struct MiscCollector<'tcx, 'interner> { lctx: &'tcx mut LoweringContext<'interner>, hir_id_owner: Option, } impl MiscCollector<'_, '_> { fn allocate_use_tree_hir_id_counters( &mut self, tree: &UseTree, owner: DefIndex, ) { match tree.kind { UseTreeKind::Simple(_, id1, id2) => { for &id in &[id1, id2] { self.lctx.resolver.definitions().create_def_with_parent( owner, id, DefPathData::Misc, ExpnId::root(), tree.prefix.span, ); self.lctx.allocate_hir_id_counter(id); } } UseTreeKind::Glob => (), UseTreeKind::Nested(ref trees) => { for &(ref use_tree, id) in trees { let hir_id = self.lctx.allocate_hir_id_counter(id); self.allocate_use_tree_hir_id_counters(use_tree, hir_id.owner); } } } } fn with_hir_id_owner(&mut self, owner: Option, f: F) -> T where F: FnOnce(&mut Self) -> T, { let old = mem::replace(&mut self.hir_id_owner, owner); let r = f(self); self.hir_id_owner = old; r } } impl<'tcx, 'interner> Visitor<'tcx> for MiscCollector<'tcx, 'interner> { fn visit_pat(&mut self, p: &'tcx Pat) { if let PatKind::Paren(..) | PatKind::Rest = p.kind { // Doesn't generate a HIR node } else if let Some(owner) = self.hir_id_owner { self.lctx.lower_node_id_with_owner(p.id, owner); } visit::walk_pat(self, p) } fn visit_item(&mut self, item: &'tcx Item) { let hir_id = self.lctx.allocate_hir_id_counter(item.id); match item.kind { ItemKind::Struct(_, ref generics) | ItemKind::Union(_, ref generics) | ItemKind::Enum(_, ref generics) | ItemKind::TyAlias(_, ref generics) | ItemKind::OpaqueTy(_, ref generics) | ItemKind::Trait(_, _, ref generics, ..) => { let def_id = self.lctx.resolver.definitions().local_def_id(item.id); let count = generics .params .iter() .filter(|param| match param.kind { ast::GenericParamKind::Lifetime { .. } => true, _ => false, }) .count(); self.lctx.type_def_lifetime_params.insert(def_id, count); } ItemKind::Use(ref use_tree) => { self.allocate_use_tree_hir_id_counters(use_tree, hir_id.owner); } _ => {} } self.with_hir_id_owner(Some(item.id), |this| { visit::walk_item(this, item); }); } fn visit_trait_item(&mut self, item: &'tcx TraitItem) { self.lctx.allocate_hir_id_counter(item.id); match item.kind { TraitItemKind::Method(_, None) => { // Ignore patterns in trait methods without bodies self.with_hir_id_owner(None, |this| { visit::walk_trait_item(this, item) }); } _ => self.with_hir_id_owner(Some(item.id), |this| { visit::walk_trait_item(this, item); }) } } fn visit_impl_item(&mut self, item: &'tcx ImplItem) { self.lctx.allocate_hir_id_counter(item.id); self.with_hir_id_owner(Some(item.id), |this| { visit::walk_impl_item(this, item); }); } fn visit_foreign_item(&mut self, i: &'tcx ForeignItem) { // Ignore patterns in foreign items self.with_hir_id_owner(None, |this| { visit::walk_foreign_item(this, i) }); } fn visit_ty(&mut self, t: &'tcx Ty) { match t.kind { // Mirrors the case in visit::walk_ty TyKind::BareFn(ref f) => { walk_list!( self, visit_generic_param, &f.generic_params ); // Mirrors visit::walk_fn_decl for parameter in &f.decl.inputs { // We don't lower the ids of argument patterns self.with_hir_id_owner(None, |this| { this.visit_pat(¶meter.pat); }); self.visit_ty(¶meter.ty) } self.visit_fn_ret_ty(&f.decl.output) } _ => visit::walk_ty(self, t), } } } self.lower_node_id(CRATE_NODE_ID); debug_assert!(self.node_id_to_hir_id[CRATE_NODE_ID] == hir::CRATE_HIR_ID); visit::walk_crate(&mut MiscCollector { lctx: &mut self, hir_id_owner: None }, c); visit::walk_crate(&mut item::ItemLowerer { lctx: &mut self }, c); let module = self.lower_mod(&c.module); let attrs = self.lower_attrs(&c.attrs); let body_ids = body_ids(&self.bodies); self.resolver .definitions() .init_node_id_to_hir_id_mapping(self.node_id_to_hir_id); hir::Crate { module, attrs, span: c.span, exported_macros: hir::HirVec::from(self.exported_macros), non_exported_macro_attrs: hir::HirVec::from(self.non_exported_macro_attrs), items: self.items, trait_items: self.trait_items, impl_items: self.impl_items, bodies: self.bodies, body_ids, trait_impls: self.trait_impls, modules: self.modules, } } fn insert_item(&mut self, item: hir::Item) { let id = item.hir_id; // FIXME: Use `debug_asset-rt`. assert_eq!(id.local_id, hir::ItemLocalId::from_u32(0)); self.items.insert(id, item); self.modules.get_mut(&self.current_module).unwrap().items.insert(id); } fn allocate_hir_id_counter(&mut self, owner: NodeId) -> hir::HirId { // Set up the counter if needed. self.item_local_id_counters.entry(owner).or_insert(0); // Always allocate the first `HirId` for the owner itself. let lowered = self.lower_node_id_with_owner(owner, owner); debug_assert_eq!(lowered.local_id.as_u32(), 0); lowered } fn lower_node_id_generic(&mut self, ast_node_id: NodeId, alloc_hir_id: F) -> hir::HirId where F: FnOnce(&mut Self) -> hir::HirId, { if ast_node_id == DUMMY_NODE_ID { return hir::DUMMY_HIR_ID; } let min_size = ast_node_id.as_usize() + 1; if min_size > self.node_id_to_hir_id.len() { self.node_id_to_hir_id.resize(min_size, hir::DUMMY_HIR_ID); } let existing_hir_id = self.node_id_to_hir_id[ast_node_id]; if existing_hir_id == hir::DUMMY_HIR_ID { // Generate a new `HirId`. let hir_id = alloc_hir_id(self); self.node_id_to_hir_id[ast_node_id] = hir_id; hir_id } else { existing_hir_id } } fn with_hir_id_owner(&mut self, owner: NodeId, f: F) -> T where F: FnOnce(&mut Self) -> T, { let counter = self.item_local_id_counters .insert(owner, HIR_ID_COUNTER_LOCKED) .unwrap_or_else(|| panic!("no `item_local_id_counters` entry for {:?}", owner)); let def_index = self.resolver.definitions().opt_def_index(owner).unwrap(); self.current_hir_id_owner.push((def_index, counter)); let ret = f(self); let (new_def_index, new_counter) = self.current_hir_id_owner.pop().unwrap(); debug_assert!(def_index == new_def_index); debug_assert!(new_counter >= counter); let prev = self.item_local_id_counters .insert(owner, new_counter) .unwrap(); debug_assert!(prev == HIR_ID_COUNTER_LOCKED); ret } /// This method allocates a new `HirId` for the given `NodeId` and stores it in /// the `LoweringContext`'s `NodeId => HirId` map. /// Take care not to call this method if the resulting `HirId` is then not /// actually used in the HIR, as that would trigger an assertion in the /// `HirIdValidator` later on, which makes sure that all `NodeId`s got mapped /// properly. Calling the method twice with the same `NodeId` is fine though. fn lower_node_id(&mut self, ast_node_id: NodeId) -> hir::HirId { self.lower_node_id_generic(ast_node_id, |this| { let &mut (def_index, ref mut local_id_counter) = this.current_hir_id_owner.last_mut().unwrap(); let local_id = *local_id_counter; *local_id_counter += 1; hir::HirId { owner: def_index, local_id: hir::ItemLocalId::from_u32(local_id), } }) } fn lower_node_id_with_owner(&mut self, ast_node_id: NodeId, owner: NodeId) -> hir::HirId { self.lower_node_id_generic(ast_node_id, |this| { let local_id_counter = this .item_local_id_counters .get_mut(&owner) .expect("called `lower_node_id_with_owner` before `allocate_hir_id_counter`"); let local_id = *local_id_counter; // We want to be sure not to modify the counter in the map while it // is also on the stack. Otherwise we'll get lost updates when writing // back from the stack to the map. debug_assert!(local_id != HIR_ID_COUNTER_LOCKED); *local_id_counter += 1; let def_index = this .resolver .definitions() .opt_def_index(owner) .expect("you forgot to call `create_def_with_parent` or are lowering node-IDs \ that do not belong to the current owner"); hir::HirId { owner: def_index, local_id: hir::ItemLocalId::from_u32(local_id), } }) } fn next_id(&mut self) -> hir::HirId { self.lower_node_id(self.sess.next_node_id()) } fn lower_res(&mut self, res: Res) -> Res { res.map_id(|id| { self.lower_node_id_generic(id, |_| { panic!("expected `NodeId` to be lowered already for res {:#?}", res); }) }) } fn expect_full_res(&mut self, id: NodeId) -> Res { self.resolver.get_partial_res(id).map_or(Res::Err, |pr| { if pr.unresolved_segments() != 0 { bug!("path not fully resolved: {:?}", pr); } pr.base_res() }) } fn expect_full_res_from_use(&mut self, id: NodeId) -> impl Iterator> { self.resolver.get_import_res(id).present_items() } fn diagnostic(&self) -> &errors::Handler { self.sess.diagnostic() } /// Reuses the span but adds information like the kind of the desugaring and features that are /// allowed inside this span. fn mark_span_with_reason( &self, reason: DesugaringKind, span: Span, allow_internal_unstable: Option>, ) -> Span { span.fresh_expansion(ExpnData { allow_internal_unstable, ..ExpnData::default(ExpnKind::Desugaring(reason), span, self.sess.edition()) }) } fn with_anonymous_lifetime_mode( &mut self, anonymous_lifetime_mode: AnonymousLifetimeMode, op: impl FnOnce(&mut Self) -> R, ) -> R { debug!( "with_anonymous_lifetime_mode(anonymous_lifetime_mode={:?})", anonymous_lifetime_mode, ); let old_anonymous_lifetime_mode = self.anonymous_lifetime_mode; self.anonymous_lifetime_mode = anonymous_lifetime_mode; let result = op(self); self.anonymous_lifetime_mode = old_anonymous_lifetime_mode; debug!("with_anonymous_lifetime_mode: restoring anonymous_lifetime_mode={:?}", old_anonymous_lifetime_mode); result } /// Creates a new `hir::GenericParam` for every new lifetime and /// type parameter encountered while evaluating `f`. Definitions /// are created with the parent provided. If no `parent_id` is /// provided, no definitions will be returned. /// /// Presuming that in-band lifetimes are enabled, then /// `self.anonymous_lifetime_mode` will be updated to match the /// parameter while `f` is running (and restored afterwards). fn collect_in_band_defs( &mut self, parent_id: DefId, anonymous_lifetime_mode: AnonymousLifetimeMode, f: F, ) -> (Vec, T) where F: FnOnce(&mut LoweringContext<'_>) -> (Vec, T), { assert!(!self.is_collecting_in_band_lifetimes); assert!(self.lifetimes_to_define.is_empty()); let old_anonymous_lifetime_mode = self.anonymous_lifetime_mode; self.anonymous_lifetime_mode = anonymous_lifetime_mode; self.is_collecting_in_band_lifetimes = true; let (in_band_ty_params, res) = f(self); self.is_collecting_in_band_lifetimes = false; self.anonymous_lifetime_mode = old_anonymous_lifetime_mode; let lifetimes_to_define = self.lifetimes_to_define.split_off(0); let params = lifetimes_to_define .into_iter() .map(|(span, hir_name)| self.lifetime_to_generic_param( span, hir_name, parent_id.index, )) .chain(in_band_ty_params.into_iter()) .collect(); (params, res) } /// Converts a lifetime into a new generic parameter. fn lifetime_to_generic_param( &mut self, span: Span, hir_name: ParamName, parent_index: DefIndex, ) -> hir::GenericParam { let node_id = self.sess.next_node_id(); // Get the name we'll use to make the def-path. Note // that collisions are ok here and this shouldn't // really show up for end-user. let (str_name, kind) = match hir_name { ParamName::Plain(ident) => ( ident.name, hir::LifetimeParamKind::InBand, ), ParamName::Fresh(_) => ( kw::UnderscoreLifetime, hir::LifetimeParamKind::Elided, ), ParamName::Error => ( kw::UnderscoreLifetime, hir::LifetimeParamKind::Error, ), }; // Add a definition for the in-band lifetime def. self.resolver.definitions().create_def_with_parent( parent_index, node_id, DefPathData::LifetimeNs(str_name), ExpnId::root(), span, ); hir::GenericParam { hir_id: self.lower_node_id(node_id), name: hir_name, attrs: hir_vec![], bounds: hir_vec![], span, pure_wrt_drop: false, kind: hir::GenericParamKind::Lifetime { kind } } } /// When there is a reference to some lifetime `'a`, and in-band /// lifetimes are enabled, then we want to push that lifetime into /// the vector of names to define later. In that case, it will get /// added to the appropriate generics. fn maybe_collect_in_band_lifetime(&mut self, ident: Ident) { if !self.is_collecting_in_band_lifetimes { return; } if !self.sess.features_untracked().in_band_lifetimes { return; } if self.in_scope_lifetimes.contains(&ParamName::Plain(ident.modern())) { return; } let hir_name = ParamName::Plain(ident); if self.lifetimes_to_define.iter() .any(|(_, lt_name)| lt_name.modern() == hir_name.modern()) { return; } self.lifetimes_to_define.push((ident.span, hir_name)); } /// When we have either an elided or `'_` lifetime in an impl /// header, we convert it to an in-band lifetime. fn collect_fresh_in_band_lifetime(&mut self, span: Span) -> ParamName { assert!(self.is_collecting_in_band_lifetimes); let index = self.lifetimes_to_define.len() + self.in_scope_lifetimes.len(); let hir_name = ParamName::Fresh(index); self.lifetimes_to_define.push((span, hir_name)); hir_name } // Evaluates `f` with the lifetimes in `params` in-scope. // This is used to track which lifetimes have already been defined, and // which are new in-band lifetimes that need to have a definition created // for them. fn with_in_scope_lifetime_defs(&mut self, params: &[GenericParam], f: F) -> T where F: FnOnce(&mut LoweringContext<'_>) -> T, { let old_len = self.in_scope_lifetimes.len(); let lt_def_names = params.iter().filter_map(|param| match param.kind { GenericParamKind::Lifetime { .. } => Some(ParamName::Plain(param.ident.modern())), _ => None, }); self.in_scope_lifetimes.extend(lt_def_names); let res = f(self); self.in_scope_lifetimes.truncate(old_len); res } /// Appends in-band lifetime defs and argument-position `impl /// Trait` defs to the existing set of generics. /// /// Presuming that in-band lifetimes are enabled, then /// `self.anonymous_lifetime_mode` will be updated to match the /// parameter while `f` is running (and restored afterwards). fn add_in_band_defs( &mut self, generics: &Generics, parent_id: DefId, anonymous_lifetime_mode: AnonymousLifetimeMode, f: F, ) -> (hir::Generics, T) where F: FnOnce(&mut LoweringContext<'_>, &mut Vec) -> T, { let (in_band_defs, (mut lowered_generics, res)) = self.with_in_scope_lifetime_defs( &generics.params, |this| { this.collect_in_band_defs(parent_id, anonymous_lifetime_mode, |this| { let mut params = Vec::new(); // Note: it is necessary to lower generics *before* calling `f`. // When lowering `async fn`, there's a final step when lowering // the return type that assumes that all in-scope lifetimes have // already been added to either `in_scope_lifetimes` or // `lifetimes_to_define`. If we swapped the order of these two, // in-band-lifetimes introduced by generics or where-clauses // wouldn't have been added yet. let generics = this.lower_generics( generics, ImplTraitContext::Universal(&mut params), ); let res = f(this, &mut params); (params, (generics, res)) }) }, ); let mut lowered_params: Vec<_> = lowered_generics .params .into_iter() .chain(in_band_defs) .collect(); // FIXME(const_generics): the compiler doesn't always cope with // unsorted generic parameters at the moment, so we make sure // that they're ordered correctly here for now. (When we chain // the `in_band_defs`, we might make the order unsorted.) lowered_params.sort_by_key(|param| { match param.kind { hir::GenericParamKind::Lifetime { .. } => ParamKindOrd::Lifetime, hir::GenericParamKind::Type { .. } => ParamKindOrd::Type, hir::GenericParamKind::Const { .. } => ParamKindOrd::Const, } }); lowered_generics.params = lowered_params.into(); (lowered_generics, res) } fn with_dyn_type_scope(&mut self, in_scope: bool, f: F) -> T where F: FnOnce(&mut LoweringContext<'_>) -> T, { let was_in_dyn_type = self.is_in_dyn_type; self.is_in_dyn_type = in_scope; let result = f(self); self.is_in_dyn_type = was_in_dyn_type; result } fn with_new_scopes(&mut self, f: F) -> T where F: FnOnce(&mut LoweringContext<'_>) -> T, { let was_in_loop_condition = self.is_in_loop_condition; self.is_in_loop_condition = false; let catch_scopes = mem::take(&mut self.catch_scopes); let loop_scopes = mem::take(&mut self.loop_scopes); let ret = f(self); self.catch_scopes = catch_scopes; self.loop_scopes = loop_scopes; self.is_in_loop_condition = was_in_loop_condition; ret } fn def_key(&mut self, id: DefId) -> DefKey { if id.is_local() { self.resolver.definitions().def_key(id.index) } else { self.resolver.cstore().def_key(id) } } fn lower_attrs_extendable(&mut self, attrs: &[Attribute]) -> Vec { attrs .iter() .map(|a| self.lower_attr(a)) .collect() } fn lower_attrs(&mut self, attrs: &[Attribute]) -> hir::HirVec { self.lower_attrs_extendable(attrs).into() } fn lower_attr(&mut self, attr: &Attribute) -> Attribute { // Note that we explicitly do not walk the path. Since we don't really // lower attributes (we use the AST version) there is nowhere to keep // the `HirId`s. We don't actually need HIR version of attributes anyway. Attribute { item: AttrItem { path: attr.path.clone(), tokens: self.lower_token_stream(attr.tokens.clone()), }, id: attr.id, style: attr.style, is_sugared_doc: attr.is_sugared_doc, span: attr.span, } } fn lower_token_stream(&mut self, tokens: TokenStream) -> TokenStream { tokens .into_trees() .flat_map(|tree| self.lower_token_tree(tree).into_trees()) .collect() } fn lower_token_tree(&mut self, tree: TokenTree) -> TokenStream { match tree { TokenTree::Token(token) => self.lower_token(token), TokenTree::Delimited(span, delim, tts) => TokenTree::Delimited( span, delim, self.lower_token_stream(tts), ).into(), } } fn lower_token(&mut self, token: Token) -> TokenStream { match token.kind { token::Interpolated(nt) => { let tts = (self.nt_to_tokenstream)(&nt, &self.sess.parse_sess, token.span); self.lower_token_stream(tts) } _ => TokenTree::Token(token).into(), } } /// Given an associated type constraint like one of these: /// /// ``` /// T: Iterator /// ^^^^^^^^^^^ /// T: Iterator /// ^^^^^^^^^^^^ /// ``` /// /// returns a `hir::TypeBinding` representing `Item`. fn lower_assoc_ty_constraint( &mut self, constraint: &AssocTyConstraint, itctx: ImplTraitContext<'_>, ) -> hir::TypeBinding { debug!("lower_assoc_ty_constraint(constraint={:?}, itctx={:?})", constraint, itctx); let kind = match constraint.kind { AssocTyConstraintKind::Equality { ref ty } => hir::TypeBindingKind::Equality { ty: self.lower_ty(ty, itctx) }, AssocTyConstraintKind::Bound { ref bounds } => { // Piggy-back on the `impl Trait` context to figure out the correct behavior. let (desugar_to_impl_trait, itctx) = match itctx { // We are in the return position: // // fn foo() -> impl Iterator // // so desugar to // // fn foo() -> impl Iterator ImplTraitContext::OpaqueTy(_) => (true, itctx), // We are in the argument position, but within a dyn type: // // fn foo(x: dyn Iterator) // // so desugar to // // fn foo(x: dyn Iterator) ImplTraitContext::Universal(_) if self.is_in_dyn_type => (true, itctx), // In `type Foo = dyn Iterator` we desugar to // `type Foo = dyn Iterator` but we have to override the // "impl trait context" to permit `impl Debug` in this position (it desugars // then to an opaque type). // // FIXME: this is only needed until `impl Trait` is allowed in type aliases. ImplTraitContext::Disallowed(_) if self.is_in_dyn_type => (true, ImplTraitContext::OpaqueTy(None)), // We are in the parameter position, but not within a dyn type: // // fn foo(x: impl Iterator) // // so we leave it as is and this gets expanded in astconv to a bound like // `::Item: Debug` where `T` is the type parameter for the // `impl Iterator`. _ => (false, itctx), }; if desugar_to_impl_trait { // Desugar `AssocTy: Bounds` into `AssocTy = impl Bounds`. We do this by // constructing the HIR for `impl bounds...` and then lowering that. let impl_trait_node_id = self.sess.next_node_id(); let parent_def_index = self.current_hir_id_owner.last().unwrap().0; self.resolver.definitions().create_def_with_parent( parent_def_index, impl_trait_node_id, DefPathData::ImplTrait, ExpnId::root(), constraint.span, ); self.with_dyn_type_scope(false, |this| { let ty = this.lower_ty( &Ty { id: this.sess.next_node_id(), kind: TyKind::ImplTrait(impl_trait_node_id, bounds.clone()), span: constraint.span, }, itctx, ); hir::TypeBindingKind::Equality { ty } }) } else { // Desugar `AssocTy: Bounds` into a type binding where the // later desugars into a trait predicate. let bounds = self.lower_param_bounds(bounds, itctx); hir::TypeBindingKind::Constraint { bounds } } } }; hir::TypeBinding { hir_id: self.lower_node_id(constraint.id), ident: constraint.ident, kind, span: constraint.span, } } fn lower_generic_arg(&mut self, arg: &ast::GenericArg, itctx: ImplTraitContext<'_>) -> hir::GenericArg { match arg { ast::GenericArg::Lifetime(lt) => GenericArg::Lifetime(self.lower_lifetime(<)), ast::GenericArg::Type(ty) => GenericArg::Type(self.lower_ty_direct(&ty, itctx)), ast::GenericArg::Const(ct) => { GenericArg::Const(ConstArg { value: self.lower_anon_const(&ct), span: ct.value.span, }) } } } fn lower_ty(&mut self, t: &Ty, itctx: ImplTraitContext<'_>) -> P { P(self.lower_ty_direct(t, itctx)) } fn lower_path_ty( &mut self, t: &Ty, qself: &Option, path: &Path, param_mode: ParamMode, itctx: ImplTraitContext<'_> ) -> hir::Ty { let id = self.lower_node_id(t.id); let qpath = self.lower_qpath(t.id, qself, path, param_mode, itctx); let ty = self.ty_path(id, t.span, qpath); if let hir::TyKind::TraitObject(..) = ty.kind { self.maybe_lint_bare_trait(t.span, t.id, qself.is_none() && path.is_global()); } ty } fn lower_ty_direct(&mut self, t: &Ty, mut itctx: ImplTraitContext<'_>) -> hir::Ty { let kind = match t.kind { TyKind::Infer => hir::TyKind::Infer, TyKind::Err => hir::TyKind::Err, TyKind::Slice(ref ty) => hir::TyKind::Slice(self.lower_ty(ty, itctx)), TyKind::Ptr(ref mt) => hir::TyKind::Ptr(self.lower_mt(mt, itctx)), TyKind::Rptr(ref region, ref mt) => { let span = self.sess.source_map().next_point(t.span.shrink_to_lo()); let lifetime = match *region { Some(ref lt) => self.lower_lifetime(lt), None => self.elided_ref_lifetime(span), }; hir::TyKind::Rptr(lifetime, self.lower_mt(mt, itctx)) } TyKind::BareFn(ref f) => self.with_in_scope_lifetime_defs( &f.generic_params, |this| { this.with_anonymous_lifetime_mode( AnonymousLifetimeMode::PassThrough, |this| { hir::TyKind::BareFn(P(hir::BareFnTy { generic_params: this.lower_generic_params( &f.generic_params, &NodeMap::default(), ImplTraitContext::disallowed(), ), unsafety: this.lower_unsafety(f.unsafety), abi: f.abi, decl: this.lower_fn_decl(&f.decl, None, false, None), param_names: this.lower_fn_params_to_names(&f.decl), })) }, ) }, ), TyKind::Never => hir::TyKind::Never, TyKind::Tup(ref tys) => { hir::TyKind::Tup(tys.iter().map(|ty| { self.lower_ty_direct(ty, itctx.reborrow()) }).collect()) } TyKind::Paren(ref ty) => { return self.lower_ty_direct(ty, itctx); } TyKind::Path(ref qself, ref path) => { return self.lower_path_ty(t, qself, path, ParamMode::Explicit, itctx); } TyKind::ImplicitSelf => { let res = self.expect_full_res(t.id); let res = self.lower_res(res); hir::TyKind::Path(hir::QPath::Resolved( None, P(hir::Path { res, segments: hir_vec![hir::PathSegment::from_ident( Ident::with_dummy_span(kw::SelfUpper) )], span: t.span, }), )) }, TyKind::Array(ref ty, ref length) => { hir::TyKind::Array(self.lower_ty(ty, itctx), self.lower_anon_const(length)) } TyKind::Typeof(ref expr) => { hir::TyKind::Typeof(self.lower_anon_const(expr)) } TyKind::TraitObject(ref bounds, kind) => { let mut lifetime_bound = None; let (bounds, lifetime_bound) = self.with_dyn_type_scope(true, |this| { let bounds = bounds .iter() .filter_map(|bound| match *bound { GenericBound::Trait(ref ty, TraitBoundModifier::None) => { Some(this.lower_poly_trait_ref(ty, itctx.reborrow())) } GenericBound::Trait(_, TraitBoundModifier::Maybe) => None, GenericBound::Outlives(ref lifetime) => { if lifetime_bound.is_none() { lifetime_bound = Some(this.lower_lifetime(lifetime)); } None } }) .collect(); let lifetime_bound = lifetime_bound.unwrap_or_else(|| this.elided_dyn_bound(t.span)); (bounds, lifetime_bound) }); if kind != TraitObjectSyntax::Dyn { self.maybe_lint_bare_trait(t.span, t.id, false); } hir::TyKind::TraitObject(bounds, lifetime_bound) } TyKind::ImplTrait(def_node_id, ref bounds) => { let span = t.span; match itctx { ImplTraitContext::OpaqueTy(fn_def_id) => { self.lower_opaque_impl_trait( span, fn_def_id, def_node_id, |this| this.lower_param_bounds(bounds, itctx), ) } ImplTraitContext::Universal(in_band_ty_params) => { // Add a definition for the in-band `Param`. let def_index = self .resolver .definitions() .opt_def_index(def_node_id) .unwrap(); let hir_bounds = self.lower_param_bounds( bounds, ImplTraitContext::Universal(in_band_ty_params), ); // Set the name to `impl Bound1 + Bound2`. let ident = Ident::from_str_and_span(&pprust::ty_to_string(t), span); in_band_ty_params.push(hir::GenericParam { hir_id: self.lower_node_id(def_node_id), name: ParamName::Plain(ident), pure_wrt_drop: false, attrs: hir_vec![], bounds: hir_bounds, span, kind: hir::GenericParamKind::Type { default: None, synthetic: Some(hir::SyntheticTyParamKind::ImplTrait), } }); hir::TyKind::Path(hir::QPath::Resolved( None, P(hir::Path { span, res: Res::Def(DefKind::TyParam, DefId::local(def_index)), segments: hir_vec![hir::PathSegment::from_ident(ident)], }), )) } ImplTraitContext::Disallowed(pos) => { let allowed_in = if self.sess.features_untracked() .impl_trait_in_bindings { "bindings or function and inherent method return types" } else { "function and inherent method return types" }; let mut err = struct_span_err!( self.sess, t.span, E0562, "`impl Trait` not allowed outside of {}", allowed_in, ); if pos == ImplTraitPosition::Binding && nightly_options::is_nightly_build() { help!(err, "add `#![feature(impl_trait_in_bindings)]` to the crate \ attributes to enable"); } err.emit(); hir::TyKind::Err } } } TyKind::Mac(_) => bug!("`TyKind::Mac` should have been expanded by now"), TyKind::CVarArgs => bug!("`TyKind::CVarArgs` should have been handled elsewhere"), }; hir::Ty { kind, span: t.span, hir_id: self.lower_node_id(t.id), } } fn lower_opaque_impl_trait( &mut self, span: Span, fn_def_id: Option, opaque_ty_node_id: NodeId, lower_bounds: impl FnOnce(&mut LoweringContext<'_>) -> hir::GenericBounds, ) -> hir::TyKind { debug!( "lower_opaque_impl_trait(fn_def_id={:?}, opaque_ty_node_id={:?}, span={:?})", fn_def_id, opaque_ty_node_id, span, ); // Make sure we know that some funky desugaring has been going on here. // This is a first: there is code in other places like for loop // desugaring that explicitly states that we don't want to track that. // Not tracking it makes lints in rustc and clippy very fragile, as // frequently opened issues show. let opaque_ty_span = self.mark_span_with_reason( DesugaringKind::OpaqueTy, span, None, ); let opaque_ty_def_index = self .resolver .definitions() .opt_def_index(opaque_ty_node_id) .unwrap(); self.allocate_hir_id_counter(opaque_ty_node_id); let hir_bounds = self.with_hir_id_owner(opaque_ty_node_id, lower_bounds); let (lifetimes, lifetime_defs) = self.lifetimes_from_impl_trait_bounds( opaque_ty_node_id, opaque_ty_def_index, &hir_bounds, ); debug!( "lower_opaque_impl_trait: lifetimes={:#?}", lifetimes, ); debug!( "lower_opaque_impl_trait: lifetime_defs={:#?}", lifetime_defs, ); self.with_hir_id_owner(opaque_ty_node_id, |lctx| { let opaque_ty_item = hir::OpaqueTy { generics: hir::Generics { params: lifetime_defs, where_clause: hir::WhereClause { predicates: hir_vec![], span, }, span, }, bounds: hir_bounds, impl_trait_fn: fn_def_id, origin: hir::OpaqueTyOrigin::FnReturn, }; trace!("lower_opaque_impl_trait: {:#?}", opaque_ty_def_index); let opaque_ty_id = lctx.generate_opaque_type( opaque_ty_node_id, opaque_ty_item, span, opaque_ty_span, ); // `impl Trait` now just becomes `Foo<'a, 'b, ..>`. hir::TyKind::Def(hir::ItemId { id: opaque_ty_id }, lifetimes) }) } /// Registers a new opaque type with the proper `NodeId`s and /// returns the lowered node-ID for the opaque type. fn generate_opaque_type( &mut self, opaque_ty_node_id: NodeId, opaque_ty_item: hir::OpaqueTy, span: Span, opaque_ty_span: Span, ) -> hir::HirId { let opaque_ty_item_kind = hir::ItemKind::OpaqueTy(opaque_ty_item); let opaque_ty_id = self.lower_node_id(opaque_ty_node_id); // Generate an `type Foo = impl Trait;` declaration. trace!("registering opaque type with id {:#?}", opaque_ty_id); let opaque_ty_item = hir::Item { hir_id: opaque_ty_id, ident: Ident::invalid(), attrs: Default::default(), kind: opaque_ty_item_kind, vis: respan(span.shrink_to_lo(), hir::VisibilityKind::Inherited), span: opaque_ty_span, }; // Insert the item into the global item list. This usually happens // automatically for all AST items. But this opaque type item // does not actually exist in the AST. self.insert_item(opaque_ty_item); opaque_ty_id } fn lifetimes_from_impl_trait_bounds( &mut self, opaque_ty_id: NodeId, parent_index: DefIndex, bounds: &hir::GenericBounds, ) -> (HirVec, HirVec) { debug!( "lifetimes_from_impl_trait_bounds(opaque_ty_id={:?}, \ parent_index={:?}, \ bounds={:#?})", opaque_ty_id, parent_index, bounds, ); // This visitor walks over `impl Trait` bounds and creates defs for all lifetimes that // appear in the bounds, excluding lifetimes that are created within the bounds. // E.g., `'a`, `'b`, but not `'c` in `impl for<'c> SomeTrait<'a, 'b, 'c>`. struct ImplTraitLifetimeCollector<'r, 'a> { context: &'r mut LoweringContext<'a>, parent: DefIndex, opaque_ty_id: NodeId, collect_elided_lifetimes: bool, currently_bound_lifetimes: Vec, already_defined_lifetimes: FxHashSet, output_lifetimes: Vec, output_lifetime_params: Vec, } impl<'r, 'a, 'v> hir::intravisit::Visitor<'v> for ImplTraitLifetimeCollector<'r, 'a> { fn nested_visit_map<'this>( &'this mut self, ) -> hir::intravisit::NestedVisitorMap<'this, 'v> { hir::intravisit::NestedVisitorMap::None } fn visit_generic_args(&mut self, span: Span, parameters: &'v hir::GenericArgs) { // Don't collect elided lifetimes used inside of `Fn()` syntax. if parameters.parenthesized { let old_collect_elided_lifetimes = self.collect_elided_lifetimes; self.collect_elided_lifetimes = false; hir::intravisit::walk_generic_args(self, span, parameters); self.collect_elided_lifetimes = old_collect_elided_lifetimes; } else { hir::intravisit::walk_generic_args(self, span, parameters); } } fn visit_ty(&mut self, t: &'v hir::Ty) { // Don't collect elided lifetimes used inside of `fn()` syntax. if let hir::TyKind::BareFn(_) = t.kind { let old_collect_elided_lifetimes = self.collect_elided_lifetimes; self.collect_elided_lifetimes = false; // Record the "stack height" of `for<'a>` lifetime bindings // to be able to later fully undo their introduction. let old_len = self.currently_bound_lifetimes.len(); hir::intravisit::walk_ty(self, t); self.currently_bound_lifetimes.truncate(old_len); self.collect_elided_lifetimes = old_collect_elided_lifetimes; } else { hir::intravisit::walk_ty(self, t) } } fn visit_poly_trait_ref( &mut self, trait_ref: &'v hir::PolyTraitRef, modifier: hir::TraitBoundModifier, ) { // Record the "stack height" of `for<'a>` lifetime bindings // to be able to later fully undo their introduction. let old_len = self.currently_bound_lifetimes.len(); hir::intravisit::walk_poly_trait_ref(self, trait_ref, modifier); self.currently_bound_lifetimes.truncate(old_len); } fn visit_generic_param(&mut self, param: &'v hir::GenericParam) { // Record the introduction of 'a in `for<'a> ...`. if let hir::GenericParamKind::Lifetime { .. } = param.kind { // Introduce lifetimes one at a time so that we can handle // cases like `fn foo<'d>() -> impl for<'a, 'b: 'a, 'c: 'b + 'd>`. let lt_name = hir::LifetimeName::Param(param.name); self.currently_bound_lifetimes.push(lt_name); } hir::intravisit::walk_generic_param(self, param); } fn visit_lifetime(&mut self, lifetime: &'v hir::Lifetime) { let name = match lifetime.name { hir::LifetimeName::Implicit | hir::LifetimeName::Underscore => { if self.collect_elided_lifetimes { // Use `'_` for both implicit and underscore lifetimes in // `type Foo<'_> = impl SomeTrait<'_>;`. hir::LifetimeName::Underscore } else { return; } } hir::LifetimeName::Param(_) => lifetime.name, // Refers to some other lifetime that is "in // scope" within the type. hir::LifetimeName::ImplicitObjectLifetimeDefault => return, hir::LifetimeName::Error | hir::LifetimeName::Static => return, }; if !self.currently_bound_lifetimes.contains(&name) && !self.already_defined_lifetimes.contains(&name) { self.already_defined_lifetimes.insert(name); self.output_lifetimes.push(hir::GenericArg::Lifetime(hir::Lifetime { hir_id: self.context.next_id(), span: lifetime.span, name, })); let def_node_id = self.context.sess.next_node_id(); let hir_id = self.context.lower_node_id_with_owner(def_node_id, self.opaque_ty_id); self.context.resolver.definitions().create_def_with_parent( self.parent, def_node_id, DefPathData::LifetimeNs(name.ident().name), ExpnId::root(), lifetime.span); let (name, kind) = match name { hir::LifetimeName::Underscore => ( hir::ParamName::Plain(Ident::with_dummy_span(kw::UnderscoreLifetime)), hir::LifetimeParamKind::Elided, ), hir::LifetimeName::Param(param_name) => ( param_name, hir::LifetimeParamKind::Explicit, ), _ => bug!("expected `LifetimeName::Param` or `ParamName::Plain`"), }; self.output_lifetime_params.push(hir::GenericParam { hir_id, name, span: lifetime.span, pure_wrt_drop: false, attrs: hir_vec![], bounds: hir_vec![], kind: hir::GenericParamKind::Lifetime { kind } }); } } } let mut lifetime_collector = ImplTraitLifetimeCollector { context: self, parent: parent_index, opaque_ty_id, collect_elided_lifetimes: true, currently_bound_lifetimes: Vec::new(), already_defined_lifetimes: FxHashSet::default(), output_lifetimes: Vec::new(), output_lifetime_params: Vec::new(), }; for bound in bounds { hir::intravisit::walk_param_bound(&mut lifetime_collector, &bound); } ( lifetime_collector.output_lifetimes.into(), lifetime_collector.output_lifetime_params.into(), ) } fn lower_qpath( &mut self, id: NodeId, qself: &Option, p: &Path, param_mode: ParamMode, mut itctx: ImplTraitContext<'_>, ) -> hir::QPath { let qself_position = qself.as_ref().map(|q| q.position); let qself = qself.as_ref().map(|q| self.lower_ty(&q.ty, itctx.reborrow())); let partial_res = self.resolver .get_partial_res(id) .unwrap_or_else(|| PartialRes::new(Res::Err)); let proj_start = p.segments.len() - partial_res.unresolved_segments(); let path = P(hir::Path { res: self.lower_res(partial_res.base_res()), segments: p.segments[..proj_start] .iter() .enumerate() .map(|(i, segment)| { let param_mode = match (qself_position, param_mode) { (Some(j), ParamMode::Optional) if i < j => { // This segment is part of the trait path in a // qualified path - one of `a`, `b` or `Trait` // in `::T::U::method`. ParamMode::Explicit } _ => param_mode, }; // Figure out if this is a type/trait segment, // which may need lifetime elision performed. let parent_def_id = |this: &mut Self, def_id: DefId| DefId { krate: def_id.krate, index: this.def_key(def_id).parent.expect("missing parent"), }; let type_def_id = match partial_res.base_res() { Res::Def(DefKind::AssocTy, def_id) if i + 2 == proj_start => { Some(parent_def_id(self, def_id)) } Res::Def(DefKind::Variant, def_id) if i + 1 == proj_start => { Some(parent_def_id(self, def_id)) } Res::Def(DefKind::Struct, def_id) | Res::Def(DefKind::Union, def_id) | Res::Def(DefKind::Enum, def_id) | Res::Def(DefKind::TyAlias, def_id) | Res::Def(DefKind::Trait, def_id) if i + 1 == proj_start => { Some(def_id) } _ => None, }; let parenthesized_generic_args = match partial_res.base_res() { // `a::b::Trait(Args)` Res::Def(DefKind::Trait, _) if i + 1 == proj_start => ParenthesizedGenericArgs::Ok, // `a::b::Trait(Args)::TraitItem` Res::Def(DefKind::Method, _) | Res::Def(DefKind::AssocConst, _) | Res::Def(DefKind::AssocTy, _) if i + 2 == proj_start => { ParenthesizedGenericArgs::Ok } // Avoid duplicated errors. Res::Err => ParenthesizedGenericArgs::Ok, // An error Res::Def(DefKind::Struct, _) | Res::Def(DefKind::Enum, _) | Res::Def(DefKind::Union, _) | Res::Def(DefKind::TyAlias, _) | Res::Def(DefKind::Variant, _) if i + 1 == proj_start => { ParenthesizedGenericArgs::Err } // A warning for now, for compatibility reasons. _ => ParenthesizedGenericArgs::Warn, }; let num_lifetimes = type_def_id.map_or(0, |def_id| { if let Some(&n) = self.type_def_lifetime_params.get(&def_id) { return n; } assert!(!def_id.is_local()); let item_generics = self.resolver.cstore() .item_generics_cloned_untracked(def_id, self.sess); let n = item_generics.own_counts().lifetimes; self.type_def_lifetime_params.insert(def_id, n); n }); self.lower_path_segment( p.span, segment, param_mode, num_lifetimes, parenthesized_generic_args, itctx.reborrow(), None, ) }) .collect(), span: p.span, }); // Simple case, either no projections, or only fully-qualified. // E.g., `std::mem::size_of` or `::Item`. if partial_res.unresolved_segments() == 0 { return hir::QPath::Resolved(qself, path); } // Create the innermost type that we're projecting from. let mut ty = if path.segments.is_empty() { // If the base path is empty that means there exists a // syntactical `Self`, e.g., `&i32` in `<&i32>::clone`. qself.expect("missing QSelf for ::...") } else { // Otherwise, the base path is an implicit `Self` type path, // e.g., `Vec` in `Vec::new` or `::Item` in // `::Item::default`. let new_id = self.next_id(); P(self.ty_path(new_id, p.span, hir::QPath::Resolved(qself, path))) }; // Anything after the base path are associated "extensions", // out of which all but the last one are associated types, // e.g., for `std::vec::Vec::::IntoIter::Item::clone`: // * base path is `std::vec::Vec` // * "extensions" are `IntoIter`, `Item` and `clone` // * type nodes are: // 1. `std::vec::Vec` (created above) // 2. `>::IntoIter` // 3. `<>::IntoIter>::Item` // * final path is `<<>::IntoIter>::Item>::clone` for (i, segment) in p.segments.iter().enumerate().skip(proj_start) { let segment = P(self.lower_path_segment( p.span, segment, param_mode, 0, ParenthesizedGenericArgs::Warn, itctx.reborrow(), None, )); let qpath = hir::QPath::TypeRelative(ty, segment); // It's finished, return the extension of the right node type. if i == p.segments.len() - 1 { return qpath; } // Wrap the associated extension in another type node. let new_id = self.next_id(); ty = P(self.ty_path(new_id, p.span, qpath)); } // We should've returned in the for loop above. span_bug!( p.span, "lower_qpath: no final extension segment in {}..{}", proj_start, p.segments.len() ) } fn lower_path_extra( &mut self, res: Res, p: &Path, param_mode: ParamMode, explicit_owner: Option, ) -> hir::Path { hir::Path { res, segments: p.segments .iter() .map(|segment| { self.lower_path_segment( p.span, segment, param_mode, 0, ParenthesizedGenericArgs::Err, ImplTraitContext::disallowed(), explicit_owner, ) }) .collect(), span: p.span, } } fn lower_path(&mut self, id: NodeId, p: &Path, param_mode: ParamMode) -> hir::Path { let res = self.expect_full_res(id); let res = self.lower_res(res); self.lower_path_extra(res, p, param_mode, None) } fn lower_path_segment( &mut self, path_span: Span, segment: &PathSegment, param_mode: ParamMode, expected_lifetimes: usize, parenthesized_generic_args: ParenthesizedGenericArgs, itctx: ImplTraitContext<'_>, explicit_owner: Option, ) -> hir::PathSegment { let (mut generic_args, infer_args) = if let Some(ref generic_args) = segment.args { let msg = "parenthesized type parameters may only be used with a `Fn` trait"; match **generic_args { GenericArgs::AngleBracketed(ref data) => { self.lower_angle_bracketed_parameter_data(data, param_mode, itctx) } GenericArgs::Parenthesized(ref data) => match parenthesized_generic_args { ParenthesizedGenericArgs::Ok => self.lower_parenthesized_parameter_data(data), ParenthesizedGenericArgs::Warn => { self.resolver.lint_buffer().buffer_lint( PARENTHESIZED_PARAMS_IN_TYPES_AND_MODULES, CRATE_NODE_ID, data.span, msg.into(), ); (hir::GenericArgs::none(), true) } ParenthesizedGenericArgs::Err => { let mut err = struct_span_err!(self.sess, data.span, E0214, "{}", msg); err.span_label(data.span, "only `Fn` traits may use parentheses"); if let Ok(snippet) = self.sess.source_map().span_to_snippet(data.span) { // Do not suggest going from `Trait()` to `Trait<>` if data.inputs.len() > 0 { let split = snippet.find('(').unwrap(); let trait_name = &snippet[0..split]; let args = &snippet[split + 1 .. snippet.len() - 1]; err.span_suggestion( data.span, "use angle brackets instead", format!("{}<{}>", trait_name, args), Applicability::MaybeIncorrect, ); } }; err.emit(); ( self.lower_angle_bracketed_parameter_data( &data.as_angle_bracketed_args(), param_mode, itctx ).0, false, ) } }, } } else { self.lower_angle_bracketed_parameter_data(&Default::default(), param_mode, itctx) }; let has_lifetimes = generic_args.args.iter().any(|arg| match arg { GenericArg::Lifetime(_) => true, _ => false, }); let first_generic_span = generic_args.args.iter().map(|a| a.span()) .chain(generic_args.bindings.iter().map(|b| b.span)).next(); if !generic_args.parenthesized && !has_lifetimes { generic_args.args = self.elided_path_lifetimes(path_span, expected_lifetimes) .into_iter() .map(|lt| GenericArg::Lifetime(lt)) .chain(generic_args.args.into_iter()) .collect(); if expected_lifetimes > 0 && param_mode == ParamMode::Explicit { let anon_lt_suggestion = vec!["'_"; expected_lifetimes].join(", "); let no_non_lt_args = generic_args.args.len() == expected_lifetimes; let no_bindings = generic_args.bindings.is_empty(); let (incl_angl_brckt, insertion_sp, suggestion) = if no_non_lt_args && no_bindings { // If there are no (non-implicit) generic args or associated type // bindings, our suggestion includes the angle brackets. (true, path_span.shrink_to_hi(), format!("<{}>", anon_lt_suggestion)) } else { // Otherwise (sorry, this is kind of gross) we need to infer the // place to splice in the `'_, ` from the generics that do exist. let first_generic_span = first_generic_span .expect("already checked that non-lifetime args or bindings exist"); (false, first_generic_span.shrink_to_lo(), format!("{}, ", anon_lt_suggestion)) }; match self.anonymous_lifetime_mode { // In create-parameter mode we error here because we don't want to support // deprecated impl elision in new features like impl elision and `async fn`, // both of which work using the `CreateParameter` mode: // // impl Foo for std::cell::Ref // note lack of '_ // async fn foo(_: std::cell::Ref) { ... } AnonymousLifetimeMode::CreateParameter => { let mut err = struct_span_err!( self.sess, path_span, E0726, "implicit elided lifetime not allowed here" ); crate::lint::builtin::add_elided_lifetime_in_path_suggestion( &self.sess, &mut err, expected_lifetimes, path_span, incl_angl_brckt, insertion_sp, suggestion, ); err.emit(); } AnonymousLifetimeMode::PassThrough | AnonymousLifetimeMode::ReportError => { self.resolver.lint_buffer().buffer_lint_with_diagnostic( ELIDED_LIFETIMES_IN_PATHS, CRATE_NODE_ID, path_span, "hidden lifetime parameters in types are deprecated", builtin::BuiltinLintDiagnostics::ElidedLifetimesInPaths( expected_lifetimes, path_span, incl_angl_brckt, insertion_sp, suggestion, ) ); } } } } let res = self.expect_full_res(segment.id); let id = if let Some(owner) = explicit_owner { self.lower_node_id_with_owner(segment.id, owner) } else { self.lower_node_id(segment.id) }; debug!( "lower_path_segment: ident={:?} original-id={:?} new-id={:?}", segment.ident, segment.id, id, ); hir::PathSegment::new( segment.ident, Some(id), Some(self.lower_res(res)), generic_args, infer_args, ) } fn lower_angle_bracketed_parameter_data( &mut self, data: &AngleBracketedArgs, param_mode: ParamMode, mut itctx: ImplTraitContext<'_>, ) -> (hir::GenericArgs, bool) { let &AngleBracketedArgs { ref args, ref constraints, .. } = data; let has_non_lt_args = args.iter().any(|arg| match arg { ast::GenericArg::Lifetime(_) => false, ast::GenericArg::Type(_) => true, ast::GenericArg::Const(_) => true, }); ( hir::GenericArgs { args: args.iter().map(|a| self.lower_generic_arg(a, itctx.reborrow())).collect(), bindings: constraints.iter() .map(|b| self.lower_assoc_ty_constraint(b, itctx.reborrow())) .collect(), parenthesized: false, }, !has_non_lt_args && param_mode == ParamMode::Optional ) } fn lower_parenthesized_parameter_data( &mut self, data: &ParenthesizedArgs, ) -> (hir::GenericArgs, bool) { // Switch to `PassThrough` mode for anonymous lifetimes; this // means that we permit things like `&Ref`, where `Ref` has // a hidden lifetime parameter. This is needed for backwards // compatibility, even in contexts like an impl header where // we generally don't permit such things (see #51008). self.with_anonymous_lifetime_mode( AnonymousLifetimeMode::PassThrough, |this| { let &ParenthesizedArgs { ref inputs, ref output, span } = data; let inputs = inputs .iter() .map(|ty| this.lower_ty_direct(ty, ImplTraitContext::disallowed())) .collect(); let mk_tup = |this: &mut Self, tys, span| { hir::Ty { kind: hir::TyKind::Tup(tys), hir_id: this.next_id(), span } }; ( hir::GenericArgs { args: hir_vec![GenericArg::Type(mk_tup(this, inputs, span))], bindings: hir_vec![ hir::TypeBinding { hir_id: this.next_id(), ident: Ident::with_dummy_span(FN_OUTPUT_NAME), kind: hir::TypeBindingKind::Equality { ty: output .as_ref() .map(|ty| this.lower_ty( &ty, ImplTraitContext::disallowed() )) .unwrap_or_else(|| P(mk_tup(this, hir::HirVec::new(), span)) ), }, span: output.as_ref().map_or(span, |ty| ty.span), } ], parenthesized: true, }, false, ) } ) } fn lower_local(&mut self, l: &Local) -> (hir::Local, SmallVec<[NodeId; 1]>) { let mut ids = SmallVec::<[NodeId; 1]>::new(); if self.sess.features_untracked().impl_trait_in_bindings { if let Some(ref ty) = l.ty { let mut visitor = ImplTraitTypeIdVisitor { ids: &mut ids }; visitor.visit_ty(ty); } } let parent_def_id = DefId::local(self.current_hir_id_owner.last().unwrap().0); (hir::Local { hir_id: self.lower_node_id(l.id), ty: l.ty .as_ref() .map(|t| self.lower_ty(t, if self.sess.features_untracked().impl_trait_in_bindings { ImplTraitContext::OpaqueTy(Some(parent_def_id)) } else { ImplTraitContext::Disallowed(ImplTraitPosition::Binding) } )), pat: self.lower_pat(&l.pat), init: l.init.as_ref().map(|e| P(self.lower_expr(e))), span: l.span, attrs: l.attrs.clone(), source: hir::LocalSource::Normal, }, ids) } fn lower_mutability(&mut self, m: Mutability) -> hir::Mutability { match m { Mutability::Mutable => hir::MutMutable, Mutability::Immutable => hir::MutImmutable, } } fn lower_fn_params_to_names(&mut self, decl: &FnDecl) -> hir::HirVec { // Skip the `...` (`CVarArgs`) trailing arguments from the AST, // as they are not explicit in HIR/Ty function signatures. // (instead, the `c_variadic` flag is set to `true`) let mut inputs = &decl.inputs[..]; if decl.c_variadic() { inputs = &inputs[..inputs.len() - 1]; } inputs .iter() .map(|param| match param.pat.kind { PatKind::Ident(_, ident, _) => ident, _ => Ident::new(kw::Invalid, param.pat.span), }) .collect() } // Lowers a function declaration. // // `decl`: the unlowered (AST) function declaration. // `fn_def_id`: if `Some`, impl Trait arguments are lowered into generic parameters on the // given DefId, otherwise impl Trait is disallowed. Must be `Some` if // `make_ret_async` is also `Some`. // `impl_trait_return_allow`: determines whether `impl Trait` can be used in return position. // This guards against trait declarations and implementations where `impl Trait` is // disallowed. // `make_ret_async`: if `Some`, converts `-> T` into `-> impl Future` in the // return type. This is used for `async fn` declarations. The `NodeId` is the ID of the // return type `impl Trait` item. fn lower_fn_decl( &mut self, decl: &FnDecl, mut in_band_ty_params: Option<(DefId, &mut Vec)>, impl_trait_return_allow: bool, make_ret_async: Option, ) -> P { let lt_mode = if make_ret_async.is_some() { // In `async fn`, argument-position elided lifetimes // must be transformed into fresh generic parameters so that // they can be applied to the opaque `impl Trait` return type. AnonymousLifetimeMode::CreateParameter } else { self.anonymous_lifetime_mode }; let c_variadic = decl.c_variadic(); // Remember how many lifetimes were already around so that we can // only look at the lifetime parameters introduced by the arguments. let inputs = self.with_anonymous_lifetime_mode(lt_mode, |this| { // Skip the `...` (`CVarArgs`) trailing arguments from the AST, // as they are not explicit in HIR/Ty function signatures. // (instead, the `c_variadic` flag is set to `true`) let mut inputs = &decl.inputs[..]; if c_variadic { inputs = &inputs[..inputs.len() - 1]; } inputs .iter() .map(|param| { if let Some((_, ibty)) = &mut in_band_ty_params { this.lower_ty_direct(¶m.ty, ImplTraitContext::Universal(ibty)) } else { this.lower_ty_direct(¶m.ty, ImplTraitContext::disallowed()) } }) .collect::>() }); let output = if let Some(ret_id) = make_ret_async { self.lower_async_fn_ret_ty( &decl.output, in_band_ty_params.expect("`make_ret_async` but no `fn_def_id`").0, ret_id, ) } else { match decl.output { FunctionRetTy::Ty(ref ty) => match in_band_ty_params { Some((def_id, _)) if impl_trait_return_allow => { hir::Return(self.lower_ty(ty, ImplTraitContext::OpaqueTy(Some(def_id)))) } _ => { hir::Return(self.lower_ty(ty, ImplTraitContext::disallowed())) } }, FunctionRetTy::Default(span) => hir::DefaultReturn(span), } }; P(hir::FnDecl { inputs, output, c_variadic, implicit_self: decl.inputs.get(0).map_or( hir::ImplicitSelfKind::None, |arg| { let is_mutable_pat = match arg.pat.kind { PatKind::Ident(BindingMode::ByValue(mt), _, _) | PatKind::Ident(BindingMode::ByRef(mt), _, _) => mt == Mutability::Mutable, _ => false, }; match arg.ty.kind { TyKind::ImplicitSelf if is_mutable_pat => hir::ImplicitSelfKind::Mut, TyKind::ImplicitSelf => hir::ImplicitSelfKind::Imm, // Given we are only considering `ImplicitSelf` types, we needn't consider // the case where we have a mutable pattern to a reference as that would // no longer be an `ImplicitSelf`. TyKind::Rptr(_, ref mt) if mt.ty.kind.is_implicit_self() && mt.mutbl == ast::Mutability::Mutable => hir::ImplicitSelfKind::MutRef, TyKind::Rptr(_, ref mt) if mt.ty.kind.is_implicit_self() => hir::ImplicitSelfKind::ImmRef, _ => hir::ImplicitSelfKind::None, } }, ), }) } // Transforms `-> T` for `async fn` into `-> OpaqueTy { .. }` // combined with the following definition of `OpaqueTy`: // // type OpaqueTy = impl Future; // // `inputs`: lowered types of parameters to the function (used to collect lifetimes) // `output`: unlowered output type (`T` in `-> T`) // `fn_def_id`: `DefId` of the parent function (used to create child impl trait definition) // `opaque_ty_node_id`: `NodeId` of the opaque `impl Trait` type that should be created // `elided_lt_replacement`: replacement for elided lifetimes in the return type fn lower_async_fn_ret_ty( &mut self, output: &FunctionRetTy, fn_def_id: DefId, opaque_ty_node_id: NodeId, ) -> hir::FunctionRetTy { debug!( "lower_async_fn_ret_ty(\ output={:?}, \ fn_def_id={:?}, \ opaque_ty_node_id={:?})", output, fn_def_id, opaque_ty_node_id, ); let span = output.span(); let opaque_ty_span = self.mark_span_with_reason( DesugaringKind::Async, span, None, ); let opaque_ty_def_index = self .resolver .definitions() .opt_def_index(opaque_ty_node_id) .unwrap(); self.allocate_hir_id_counter(opaque_ty_node_id); // When we create the opaque type for this async fn, it is going to have // to capture all the lifetimes involved in the signature (including in the // return type). This is done by introducing lifetime parameters for: // // - all the explicitly declared lifetimes from the impl and function itself; // - all the elided lifetimes in the fn arguments; // - all the elided lifetimes in the return type. // // So for example in this snippet: // // ```rust // impl<'a> Foo<'a> { // async fn bar<'b>(&self, x: &'b Vec, y: &str) -> &u32 { // // ^ '0 ^ '1 ^ '2 // // elided lifetimes used below // } // } // ``` // // we would create an opaque type like: // // ``` // type Bar<'a, 'b, '0, '1, '2> = impl Future; // ``` // // and we would then desugar `bar` to the equivalent of: // // ```rust // impl<'a> Foo<'a> { // fn bar<'b, '0, '1>(&'0 self, x: &'b Vec, y: &'1 str) -> Bar<'a, 'b, '0, '1, '_> // } // ``` // // Note that the final parameter to `Bar` is `'_`, not `'2` -- // this is because the elided lifetimes from the return type // should be figured out using the ordinary elision rules, and // this desugaring achieves that. // // The variable `input_lifetimes_count` tracks the number of // lifetime parameters to the opaque type *not counting* those // lifetimes elided in the return type. This includes those // that are explicitly declared (`in_scope_lifetimes`) and // those elided lifetimes we found in the arguments (current // content of `lifetimes_to_define`). Next, we will process // the return type, which will cause `lifetimes_to_define` to // grow. let input_lifetimes_count = self.in_scope_lifetimes.len() + self.lifetimes_to_define.len(); let (opaque_ty_id, lifetime_params) = self.with_hir_id_owner(opaque_ty_node_id, |this| { // We have to be careful to get elision right here. The // idea is that we create a lifetime parameter for each // lifetime in the return type. So, given a return type // like `async fn foo(..) -> &[&u32]`, we lower to `impl // Future`. // // Then, we will create `fn foo(..) -> Foo<'_, '_>`, and // hence the elision takes place at the fn site. let future_bound = this.with_anonymous_lifetime_mode( AnonymousLifetimeMode::CreateParameter, |this| this.lower_async_fn_output_type_to_future_bound( output, fn_def_id, span, ), ); debug!("lower_async_fn_ret_ty: future_bound={:#?}", future_bound); // Calculate all the lifetimes that should be captured // by the opaque type. This should include all in-scope // lifetime parameters, including those defined in-band. // // Note: this must be done after lowering the output type, // as the output type may introduce new in-band lifetimes. let lifetime_params: Vec<(Span, ParamName)> = this.in_scope_lifetimes .iter().cloned() .map(|name| (name.ident().span, name)) .chain(this.lifetimes_to_define.iter().cloned()) .collect(); debug!("lower_async_fn_ret_ty: in_scope_lifetimes={:#?}", this.in_scope_lifetimes); debug!("lower_async_fn_ret_ty: lifetimes_to_define={:#?}", this.lifetimes_to_define); debug!("lower_async_fn_ret_ty: lifetime_params={:#?}", lifetime_params); let generic_params = lifetime_params .iter().cloned() .map(|(span, hir_name)| { this.lifetime_to_generic_param(span, hir_name, opaque_ty_def_index) }) .collect(); let opaque_ty_item = hir::OpaqueTy { generics: hir::Generics { params: generic_params, where_clause: hir::WhereClause { predicates: hir_vec![], span, }, span, }, bounds: hir_vec![future_bound], impl_trait_fn: Some(fn_def_id), origin: hir::OpaqueTyOrigin::AsyncFn, }; trace!("exist ty from async fn def index: {:#?}", opaque_ty_def_index); let opaque_ty_id = this.generate_opaque_type( opaque_ty_node_id, opaque_ty_item, span, opaque_ty_span, ); (opaque_ty_id, lifetime_params) }); // As documented above on the variable // `input_lifetimes_count`, we need to create the lifetime // arguments to our opaque type. Continuing with our example, // we're creating the type arguments for the return type: // // ``` // Bar<'a, 'b, '0, '1, '_> // ``` // // For the "input" lifetime parameters, we wish to create // references to the parameters themselves, including the // "implicit" ones created from parameter types (`'a`, `'b`, // '`0`, `'1`). // // For the "output" lifetime parameters, we just want to // generate `'_`. let mut generic_args: Vec<_> = lifetime_params[..input_lifetimes_count] .iter() .map(|&(span, hir_name)| { // Input lifetime like `'a` or `'1`: GenericArg::Lifetime(hir::Lifetime { hir_id: self.next_id(), span, name: hir::LifetimeName::Param(hir_name), }) }) .collect(); generic_args.extend( lifetime_params[input_lifetimes_count..] .iter() .map(|&(span, _)| { // Output lifetime like `'_`. GenericArg::Lifetime(hir::Lifetime { hir_id: self.next_id(), span, name: hir::LifetimeName::Implicit, }) }) ); // Create the `Foo<...>` refernece itself. Note that the `type // Foo = impl Trait` is, internally, created as a child of the // async fn, so the *type parameters* are inherited. It's // only the lifetime parameters that we must supply. let opaque_ty_ref = hir::TyKind::Def(hir::ItemId { id: opaque_ty_id }, generic_args.into()); hir::FunctionRetTy::Return(P(hir::Ty { kind: opaque_ty_ref, span, hir_id: self.next_id(), })) } /// Transforms `-> T` into `Future` fn lower_async_fn_output_type_to_future_bound( &mut self, output: &FunctionRetTy, fn_def_id: DefId, span: Span, ) -> hir::GenericBound { // Compute the `T` in `Future` from the return type. let output_ty = match output { FunctionRetTy::Ty(ty) => { self.lower_ty(ty, ImplTraitContext::OpaqueTy(Some(fn_def_id))) } FunctionRetTy::Default(ret_ty_span) => { P(hir::Ty { hir_id: self.next_id(), kind: hir::TyKind::Tup(hir_vec![]), span: *ret_ty_span, }) } }; // "" let future_params = P(hir::GenericArgs { args: hir_vec![], bindings: hir_vec![hir::TypeBinding { ident: Ident::with_dummy_span(FN_OUTPUT_NAME), kind: hir::TypeBindingKind::Equality { ty: output_ty, }, hir_id: self.next_id(), span, }], parenthesized: false, }); // ::std::future::Future let future_path = P(self.std_path(span, &[sym::future, sym::Future], Some(future_params), false)); hir::GenericBound::Trait( hir::PolyTraitRef { trait_ref: hir::TraitRef { path: future_path, hir_ref_id: self.next_id(), }, bound_generic_params: hir_vec![], span, }, hir::TraitBoundModifier::None, ) } fn lower_param_bound( &mut self, tpb: &GenericBound, itctx: ImplTraitContext<'_>, ) -> hir::GenericBound { match *tpb { GenericBound::Trait(ref ty, modifier) => { hir::GenericBound::Trait( self.lower_poly_trait_ref(ty, itctx), self.lower_trait_bound_modifier(modifier), ) } GenericBound::Outlives(ref lifetime) => { hir::GenericBound::Outlives(self.lower_lifetime(lifetime)) } } } fn lower_lifetime(&mut self, l: &Lifetime) -> hir::Lifetime { let span = l.ident.span; match l.ident { ident if ident.name == kw::StaticLifetime => self.new_named_lifetime(l.id, span, hir::LifetimeName::Static), ident if ident.name == kw::UnderscoreLifetime => match self.anonymous_lifetime_mode { AnonymousLifetimeMode::CreateParameter => { let fresh_name = self.collect_fresh_in_band_lifetime(span); self.new_named_lifetime(l.id, span, hir::LifetimeName::Param(fresh_name)) } AnonymousLifetimeMode::PassThrough => { self.new_named_lifetime(l.id, span, hir::LifetimeName::Underscore) } AnonymousLifetimeMode::ReportError => self.new_error_lifetime(Some(l.id), span), }, ident => { self.maybe_collect_in_band_lifetime(ident); let param_name = ParamName::Plain(ident); self.new_named_lifetime(l.id, span, hir::LifetimeName::Param(param_name)) } } } fn new_named_lifetime( &mut self, id: NodeId, span: Span, name: hir::LifetimeName, ) -> hir::Lifetime { hir::Lifetime { hir_id: self.lower_node_id(id), span, name: name, } } fn lower_generic_params( &mut self, params: &[GenericParam], add_bounds: &NodeMap>, mut itctx: ImplTraitContext<'_>, ) -> hir::HirVec { params.iter().map(|param| { self.lower_generic_param(param, add_bounds, itctx.reborrow()) }).collect() } fn lower_generic_param(&mut self, param: &GenericParam, add_bounds: &NodeMap>, mut itctx: ImplTraitContext<'_>) -> hir::GenericParam { let mut bounds = self.with_anonymous_lifetime_mode( AnonymousLifetimeMode::ReportError, |this| this.lower_param_bounds(¶m.bounds, itctx.reborrow()), ); let (name, kind) = match param.kind { GenericParamKind::Lifetime => { let was_collecting_in_band = self.is_collecting_in_band_lifetimes; self.is_collecting_in_band_lifetimes = false; let lt = self.with_anonymous_lifetime_mode( AnonymousLifetimeMode::ReportError, |this| this.lower_lifetime(&Lifetime { id: param.id, ident: param.ident }), ); let param_name = match lt.name { hir::LifetimeName::Param(param_name) => param_name, hir::LifetimeName::Implicit | hir::LifetimeName::Underscore | hir::LifetimeName::Static => hir::ParamName::Plain(lt.name.ident()), hir::LifetimeName::ImplicitObjectLifetimeDefault => { span_bug!( param.ident.span, "object-lifetime-default should not occur here", ); } hir::LifetimeName::Error => ParamName::Error, }; let kind = hir::GenericParamKind::Lifetime { kind: hir::LifetimeParamKind::Explicit }; self.is_collecting_in_band_lifetimes = was_collecting_in_band; (param_name, kind) } GenericParamKind::Type { ref default, .. } => { let add_bounds = add_bounds.get(¶m.id).map_or(&[][..], |x| &x); if !add_bounds.is_empty() { let params = self.lower_param_bounds(add_bounds, itctx.reborrow()).into_iter(); bounds = bounds.into_iter() .chain(params) .collect(); } let kind = hir::GenericParamKind::Type { default: default.as_ref().map(|x| { self.lower_ty(x, ImplTraitContext::OpaqueTy(None)) }), synthetic: param.attrs.iter() .filter(|attr| attr.check_name(sym::rustc_synthetic)) .map(|_| hir::SyntheticTyParamKind::ImplTrait) .next(), }; (hir::ParamName::Plain(param.ident), kind) } GenericParamKind::Const { ref ty } => { (hir::ParamName::Plain(param.ident), hir::GenericParamKind::Const { ty: self.lower_ty(&ty, ImplTraitContext::disallowed()), }) } }; hir::GenericParam { hir_id: self.lower_node_id(param.id), name, span: param.ident.span, pure_wrt_drop: attr::contains_name(¶m.attrs, sym::may_dangle), attrs: self.lower_attrs(¶m.attrs), bounds, kind, } } fn lower_trait_ref(&mut self, p: &TraitRef, itctx: ImplTraitContext<'_>) -> hir::TraitRef { let path = match self.lower_qpath(p.ref_id, &None, &p.path, ParamMode::Explicit, itctx) { hir::QPath::Resolved(None, path) => path, qpath => bug!("lower_trait_ref: unexpected QPath `{:?}`", qpath), }; hir::TraitRef { path, hir_ref_id: self.lower_node_id(p.ref_id), } } fn lower_poly_trait_ref( &mut self, p: &PolyTraitRef, mut itctx: ImplTraitContext<'_>, ) -> hir::PolyTraitRef { let bound_generic_params = self.lower_generic_params( &p.bound_generic_params, &NodeMap::default(), itctx.reborrow(), ); let trait_ref = self.with_in_scope_lifetime_defs( &p.bound_generic_params, |this| this.lower_trait_ref(&p.trait_ref, itctx), ); hir::PolyTraitRef { bound_generic_params, trait_ref, span: p.span, } } fn lower_mt(&mut self, mt: &MutTy, itctx: ImplTraitContext<'_>) -> hir::MutTy { hir::MutTy { ty: self.lower_ty(&mt.ty, itctx), mutbl: self.lower_mutability(mt.mutbl), } } fn lower_param_bounds(&mut self, bounds: &[GenericBound], mut itctx: ImplTraitContext<'_>) -> hir::GenericBounds { bounds.iter().map(|bound| self.lower_param_bound(bound, itctx.reborrow())).collect() } fn lower_block(&mut self, b: &Block, targeted_by_break: bool) -> P { let mut stmts = vec![]; let mut expr = None; for (index, stmt) in b.stmts.iter().enumerate() { if index == b.stmts.len() - 1 { if let StmtKind::Expr(ref e) = stmt.kind { expr = Some(P(self.lower_expr(e))); } else { stmts.extend(self.lower_stmt(stmt)); } } else { stmts.extend(self.lower_stmt(stmt)); } } P(hir::Block { hir_id: self.lower_node_id(b.id), stmts: stmts.into(), expr, rules: self.lower_block_check_mode(&b.rules), span: b.span, targeted_by_break, }) } /// Lowers a block directly to an expression, presuming that it /// has no attributes and is not targeted by a `break`. fn lower_block_expr(&mut self, b: &Block) -> hir::Expr { let block = self.lower_block(b, false); self.expr_block(block, ThinVec::new()) } fn lower_pat(&mut self, p: &Pat) -> P { let node = match p.kind { PatKind::Wild => hir::PatKind::Wild, PatKind::Ident(ref binding_mode, ident, ref sub) => { let lower_sub = |this: &mut Self| sub.as_ref().map(|x| this.lower_pat(x)); self.lower_pat_ident(p, binding_mode, ident, lower_sub) } PatKind::Lit(ref e) => hir::PatKind::Lit(P(self.lower_expr(e))), PatKind::TupleStruct(ref path, ref pats) => { let qpath = self.lower_qpath( p.id, &None, path, ParamMode::Optional, ImplTraitContext::disallowed(), ); let (pats, ddpos) = self.lower_pat_tuple(pats, "tuple struct"); hir::PatKind::TupleStruct(qpath, pats, ddpos) } PatKind::Or(ref pats) => { hir::PatKind::Or(pats.iter().map(|x| self.lower_pat(x)).collect()) } PatKind::Path(ref qself, ref path) => { let qpath = self.lower_qpath( p.id, qself, path, ParamMode::Optional, ImplTraitContext::disallowed(), ); hir::PatKind::Path(qpath) } PatKind::Struct(ref path, ref fields, etc) => { let qpath = self.lower_qpath( p.id, &None, path, ParamMode::Optional, ImplTraitContext::disallowed(), ); let fs = fields .iter() .map(|f| hir::FieldPat { hir_id: self.next_id(), ident: f.ident, pat: self.lower_pat(&f.pat), is_shorthand: f.is_shorthand, span: f.span, }) .collect(); hir::PatKind::Struct(qpath, fs, etc) } PatKind::Tuple(ref pats) => { let (pats, ddpos) = self.lower_pat_tuple(pats, "tuple"); hir::PatKind::Tuple(pats, ddpos) } PatKind::Box(ref inner) => hir::PatKind::Box(self.lower_pat(inner)), PatKind::Ref(ref inner, mutbl) => { hir::PatKind::Ref(self.lower_pat(inner), self.lower_mutability(mutbl)) } PatKind::Range(ref e1, ref e2, Spanned { node: ref end, .. }) => hir::PatKind::Range( P(self.lower_expr(e1)), P(self.lower_expr(e2)), self.lower_range_end(end), ), PatKind::Slice(ref pats) => self.lower_pat_slice(pats), PatKind::Rest => { // If we reach here the `..` pattern is not semantically allowed. self.ban_illegal_rest_pat(p.span) } PatKind::Paren(ref inner) => return self.lower_pat(inner), PatKind::Mac(_) => panic!("Shouldn't exist here"), }; self.pat_with_node_id_of(p, node) } fn lower_pat_tuple( &mut self, pats: &[AstP], ctx: &str, ) -> (HirVec>, Option) { let mut elems = Vec::with_capacity(pats.len()); let mut rest = None; let mut iter = pats.iter().enumerate(); while let Some((idx, pat)) = iter.next() { // Interpret the first `..` pattern as a subtuple pattern. if pat.is_rest() { rest = Some((idx, pat.span)); break; } // It was not a subslice pattern so lower it normally. elems.push(self.lower_pat(pat)); } while let Some((_, pat)) = iter.next() { // There was a previous subtuple pattern; make sure we don't allow more. if pat.is_rest() { self.ban_extra_rest_pat(pat.span, rest.unwrap().1, ctx); } else { elems.push(self.lower_pat(pat)); } } (elems.into(), rest.map(|(ddpos, _)| ddpos)) } fn lower_pat_slice(&mut self, pats: &[AstP]) -> hir::PatKind { let mut before = Vec::new(); let mut after = Vec::new(); let mut slice = None; let mut prev_rest_span = None; let mut iter = pats.iter(); while let Some(pat) = iter.next() { // Interpret the first `((ref mut?)? x @)? ..` pattern as a subslice pattern. match pat.kind { PatKind::Rest => { prev_rest_span = Some(pat.span); slice = Some(self.pat_wild_with_node_id_of(pat)); break; }, PatKind::Ident(ref bm, ident, Some(ref sub)) if sub.is_rest() => { prev_rest_span = Some(sub.span); let lower_sub = |this: &mut Self| Some(this.pat_wild_with_node_id_of(sub)); let node = self.lower_pat_ident(pat, bm, ident, lower_sub); slice = Some(self.pat_with_node_id_of(pat, node)); break; }, _ => {} } // It was not a subslice pattern so lower it normally. before.push(self.lower_pat(pat)); } while let Some(pat) = iter.next() { // There was a previous subslice pattern; make sure we don't allow more. let rest_span = match pat.kind { PatKind::Rest => Some(pat.span), PatKind::Ident(.., Some(ref sub)) if sub.is_rest() => { // The `HirValidator` is merciless; add a `_` pattern to avoid ICEs. after.push(self.pat_wild_with_node_id_of(pat)); Some(sub.span) }, _ => None, }; if let Some(rest_span) = rest_span { self.ban_extra_rest_pat(rest_span, prev_rest_span.unwrap(), "slice"); } else { after.push(self.lower_pat(pat)); } } hir::PatKind::Slice(before.into(), slice, after.into()) } fn lower_pat_ident( &mut self, p: &Pat, binding_mode: &BindingMode, ident: Ident, lower_sub: impl FnOnce(&mut Self) -> Option>, ) -> hir::PatKind { match self.resolver.get_partial_res(p.id).map(|d| d.base_res()) { // `None` can occur in body-less function signatures res @ None | res @ Some(Res::Local(_)) => { let canonical_id = match res { Some(Res::Local(id)) => id, _ => p.id, }; hir::PatKind::Binding( self.lower_binding_mode(binding_mode), self.lower_node_id(canonical_id), ident, lower_sub(self), ) } Some(res) => hir::PatKind::Path(hir::QPath::Resolved( None, P(hir::Path { span: ident.span, res: self.lower_res(res), segments: hir_vec![hir::PathSegment::from_ident(ident)], }), )), } } fn pat_wild_with_node_id_of(&mut self, p: &Pat) -> P { self.pat_with_node_id_of(p, hir::PatKind::Wild) } /// Construct a `Pat` with the `HirId` of `p.id` lowered. fn pat_with_node_id_of(&mut self, p: &Pat, kind: hir::PatKind) -> P { P(hir::Pat { hir_id: self.lower_node_id(p.id), kind, span: p.span, }) } /// Emit a friendly error for extra `..` patterns in a tuple/tuple struct/slice pattern. fn ban_extra_rest_pat(&self, sp: Span, prev_sp: Span, ctx: &str) { self.diagnostic() .struct_span_err(sp, &format!("`..` can only be used once per {} pattern", ctx)) .span_label(sp, &format!("can only be used once per {} pattern", ctx)) .span_label(prev_sp, "previously used here") .emit(); } /// Used to ban the `..` pattern in places it shouldn't be semantically. fn ban_illegal_rest_pat(&self, sp: Span) -> hir::PatKind { self.diagnostic() .struct_span_err(sp, "`..` patterns are not allowed here") .note("only allowed in tuple, tuple struct, and slice patterns") .emit(); // We're not in a list context so `..` can be reasonably treated // as `_` because it should always be valid and roughly matches the // intent of `..` (notice that the rest of a single slot is that slot). hir::PatKind::Wild } fn lower_range_end(&mut self, e: &RangeEnd) -> hir::RangeEnd { match *e { RangeEnd::Included(_) => hir::RangeEnd::Included, RangeEnd::Excluded => hir::RangeEnd::Excluded, } } fn lower_anon_const(&mut self, c: &AnonConst) -> hir::AnonConst { self.with_new_scopes(|this| { hir::AnonConst { hir_id: this.lower_node_id(c.id), body: this.lower_const_body(&c.value), } }) } fn lower_stmt(&mut self, s: &Stmt) -> SmallVec<[hir::Stmt; 1]> { let kind = match s.kind { StmtKind::Local(ref l) => { let (l, item_ids) = self.lower_local(l); let mut ids: SmallVec<[hir::Stmt; 1]> = item_ids .into_iter() .map(|item_id| { let item_id = hir::ItemId { id: self.lower_node_id(item_id) }; self.stmt(s.span, hir::StmtKind::Item(item_id)) }) .collect(); ids.push({ hir::Stmt { hir_id: self.lower_node_id(s.id), kind: hir::StmtKind::Local(P(l)), span: s.span, } }); return ids; }, StmtKind::Item(ref it) => { // Can only use the ID once. let mut id = Some(s.id); return self.lower_item_id(it) .into_iter() .map(|item_id| { let hir_id = id.take() .map(|id| self.lower_node_id(id)) .unwrap_or_else(|| self.next_id()); hir::Stmt { hir_id, kind: hir::StmtKind::Item(item_id), span: s.span, } }) .collect(); } StmtKind::Expr(ref e) => hir::StmtKind::Expr(P(self.lower_expr(e))), StmtKind::Semi(ref e) => hir::StmtKind::Semi(P(self.lower_expr(e))), StmtKind::Mac(..) => panic!("shouldn't exist here"), }; smallvec![hir::Stmt { hir_id: self.lower_node_id(s.id), kind, span: s.span, }] } fn lower_block_check_mode(&mut self, b: &BlockCheckMode) -> hir::BlockCheckMode { match *b { BlockCheckMode::Default => hir::DefaultBlock, BlockCheckMode::Unsafe(u) => hir::UnsafeBlock(self.lower_unsafe_source(u)), } } fn lower_binding_mode(&mut self, b: &BindingMode) -> hir::BindingAnnotation { match *b { BindingMode::ByValue(Mutability::Immutable) => hir::BindingAnnotation::Unannotated, BindingMode::ByRef(Mutability::Immutable) => hir::BindingAnnotation::Ref, BindingMode::ByValue(Mutability::Mutable) => hir::BindingAnnotation::Mutable, BindingMode::ByRef(Mutability::Mutable) => hir::BindingAnnotation::RefMut, } } fn lower_unsafe_source(&mut self, u: UnsafeSource) -> hir::UnsafeSource { match u { CompilerGenerated => hir::CompilerGenerated, UserProvided => hir::UserProvided, } } fn lower_trait_bound_modifier(&mut self, f: TraitBoundModifier) -> hir::TraitBoundModifier { match f { TraitBoundModifier::None => hir::TraitBoundModifier::None, TraitBoundModifier::Maybe => hir::TraitBoundModifier::Maybe, } } // Helper methods for building HIR. fn stmt(&mut self, span: Span, kind: hir::StmtKind) -> hir::Stmt { hir::Stmt { span, kind, hir_id: self.next_id() } } fn stmt_expr(&mut self, span: Span, expr: hir::Expr) -> hir::Stmt { self.stmt(span, hir::StmtKind::Expr(P(expr))) } fn stmt_let_pat( &mut self, attrs: ThinVec, span: Span, init: Option>, pat: P, source: hir::LocalSource, ) -> hir::Stmt { let local = hir::Local { attrs, hir_id: self.next_id(), init, pat, source, span, ty: None, }; self.stmt(span, hir::StmtKind::Local(P(local))) } fn block_expr(&mut self, expr: P) -> hir::Block { self.block_all(expr.span, hir::HirVec::new(), Some(expr)) } fn block_all( &mut self, span: Span, stmts: hir::HirVec, expr: Option>, ) -> hir::Block { hir::Block { stmts, expr, hir_id: self.next_id(), rules: hir::DefaultBlock, span, targeted_by_break: false, } } /// Constructs a `true` or `false` literal pattern. fn pat_bool(&mut self, span: Span, val: bool) -> P { let expr = self.expr_bool(span, val); self.pat(span, hir::PatKind::Lit(P(expr))) } fn pat_ok(&mut self, span: Span, pat: P) -> P { self.pat_std_enum(span, &[sym::result, sym::Result, sym::Ok], hir_vec![pat]) } fn pat_err(&mut self, span: Span, pat: P) -> P { self.pat_std_enum(span, &[sym::result, sym::Result, sym::Err], hir_vec![pat]) } fn pat_some(&mut self, span: Span, pat: P) -> P { self.pat_std_enum(span, &[sym::option, sym::Option, sym::Some], hir_vec![pat]) } fn pat_none(&mut self, span: Span) -> P { self.pat_std_enum(span, &[sym::option, sym::Option, sym::None], hir_vec![]) } fn pat_std_enum( &mut self, span: Span, components: &[Symbol], subpats: hir::HirVec>, ) -> P { let path = self.std_path(span, components, None, true); let qpath = hir::QPath::Resolved(None, P(path)); let pt = if subpats.is_empty() { hir::PatKind::Path(qpath) } else { hir::PatKind::TupleStruct(qpath, subpats, None) }; self.pat(span, pt) } fn pat_ident(&mut self, span: Span, ident: Ident) -> (P, hir::HirId) { self.pat_ident_binding_mode(span, ident, hir::BindingAnnotation::Unannotated) } fn pat_ident_binding_mode( &mut self, span: Span, ident: Ident, bm: hir::BindingAnnotation, ) -> (P, hir::HirId) { let hir_id = self.next_id(); ( P(hir::Pat { hir_id, kind: hir::PatKind::Binding(bm, hir_id, ident.with_span_pos(span), None), span, }), hir_id ) } fn pat_wild(&mut self, span: Span) -> P { self.pat(span, hir::PatKind::Wild) } fn pat(&mut self, span: Span, kind: hir::PatKind) -> P { P(hir::Pat { hir_id: self.next_id(), kind, span, }) } /// Given a suffix `["b", "c", "d"]`, returns path `::std::b::c::d` when /// `fld.cx.use_std`, and `::core::b::c::d` otherwise. /// The path is also resolved according to `is_value`. fn std_path( &mut self, span: Span, components: &[Symbol], params: Option>, is_value: bool, ) -> hir::Path { let ns = if is_value { Namespace::ValueNS } else { Namespace::TypeNS }; let (path, res) = self.resolver.resolve_str_path(span, self.crate_root, components, ns); let mut segments: Vec<_> = path.segments.iter().map(|segment| { let res = self.expect_full_res(segment.id); hir::PathSegment { ident: segment.ident, hir_id: Some(self.lower_node_id(segment.id)), res: Some(self.lower_res(res)), infer_args: true, args: None, } }).collect(); segments.last_mut().unwrap().args = params; hir::Path { span, res: res.map_id(|_| panic!("unexpected `NodeId`")), segments: segments.into(), } } fn ty_path(&mut self, mut hir_id: hir::HirId, span: Span, qpath: hir::QPath) -> hir::Ty { let kind = match qpath { hir::QPath::Resolved(None, path) => { // Turn trait object paths into `TyKind::TraitObject` instead. match path.res { Res::Def(DefKind::Trait, _) | Res::Def(DefKind::TraitAlias, _) => { let principal = hir::PolyTraitRef { bound_generic_params: hir::HirVec::new(), trait_ref: hir::TraitRef { path, hir_ref_id: hir_id, }, span, }; // The original ID is taken by the `PolyTraitRef`, // so the `Ty` itself needs a different one. hir_id = self.next_id(); hir::TyKind::TraitObject(hir_vec![principal], self.elided_dyn_bound(span)) } _ => hir::TyKind::Path(hir::QPath::Resolved(None, path)), } } _ => hir::TyKind::Path(qpath), }; hir::Ty { hir_id, kind, span, } } /// Invoked to create the lifetime argument for a type `&T` /// with no explicit lifetime. fn elided_ref_lifetime(&mut self, span: Span) -> hir::Lifetime { match self.anonymous_lifetime_mode { // Intercept when we are in an impl header or async fn and introduce an in-band // lifetime. // Hence `impl Foo for &u32` becomes `impl<'f> Foo for &'f u32` for some fresh // `'f`. AnonymousLifetimeMode::CreateParameter => { let fresh_name = self.collect_fresh_in_band_lifetime(span); hir::Lifetime { hir_id: self.next_id(), span, name: hir::LifetimeName::Param(fresh_name), } } AnonymousLifetimeMode::ReportError => self.new_error_lifetime(None, span), AnonymousLifetimeMode::PassThrough => self.new_implicit_lifetime(span), } } /// Report an error on illegal use of `'_` or a `&T` with no explicit lifetime; /// return a "error lifetime". fn new_error_lifetime(&mut self, id: Option, span: Span) -> hir::Lifetime { let (id, msg, label) = match id { Some(id) => (id, "`'_` cannot be used here", "`'_` is a reserved lifetime name"), None => ( self.sess.next_node_id(), "`&` without an explicit lifetime name cannot be used here", "explicit lifetime name needed here", ), }; let mut err = struct_span_err!( self.sess, span, E0637, "{}", msg, ); err.span_label(span, label); err.emit(); self.new_named_lifetime(id, span, hir::LifetimeName::Error) } /// Invoked to create the lifetime argument(s) for a path like /// `std::cell::Ref`; note that implicit lifetimes in these /// sorts of cases are deprecated. This may therefore report a warning or an /// error, depending on the mode. fn elided_path_lifetimes(&mut self, span: Span, count: usize) -> P<[hir::Lifetime]> { (0..count) .map(|_| self.elided_path_lifetime(span)) .collect() } fn elided_path_lifetime(&mut self, span: Span) -> hir::Lifetime { match self.anonymous_lifetime_mode { AnonymousLifetimeMode::CreateParameter => { // We should have emitted E0726 when processing this path above self.sess.delay_span_bug( span, "expected 'implicit elided lifetime not allowed' error", ); let id = self.sess.next_node_id(); self.new_named_lifetime(id, span, hir::LifetimeName::Error) } // `PassThrough` is the normal case. // `new_error_lifetime`, which would usually be used in the case of `ReportError`, // is unsuitable here, as these can occur from missing lifetime parameters in a // `PathSegment`, for which there is no associated `'_` or `&T` with no explicit // lifetime. Instead, we simply create an implicit lifetime, which will be checked // later, at which point a suitable error will be emitted. | AnonymousLifetimeMode::PassThrough | AnonymousLifetimeMode::ReportError => self.new_implicit_lifetime(span), } } /// Invoked to create the lifetime argument(s) for an elided trait object /// bound, like the bound in `Box`. This method is not invoked /// when the bound is written, even if it is written with `'_` like in /// `Box`. In those cases, `lower_lifetime` is invoked. fn elided_dyn_bound(&mut self, span: Span) -> hir::Lifetime { match self.anonymous_lifetime_mode { // NB. We intentionally ignore the create-parameter mode here. // and instead "pass through" to resolve-lifetimes, which will apply // the object-lifetime-defaulting rules. Elided object lifetime defaults // do not act like other elided lifetimes. In other words, given this: // // impl Foo for Box // // we do not introduce a fresh `'_` to serve as the bound, but instead // ultimately translate to the equivalent of: // // impl Foo for Box // // `resolve_lifetime` has the code to make that happen. AnonymousLifetimeMode::CreateParameter => {} AnonymousLifetimeMode::ReportError => { // ReportError applies to explicit use of `'_`. } // This is the normal case. AnonymousLifetimeMode::PassThrough => {} } let r = hir::Lifetime { hir_id: self.next_id(), span, name: hir::LifetimeName::ImplicitObjectLifetimeDefault, }; debug!("elided_dyn_bound: r={:?}", r); r } fn new_implicit_lifetime(&mut self, span: Span) -> hir::Lifetime { hir::Lifetime { hir_id: self.next_id(), span, name: hir::LifetimeName::Implicit, } } fn maybe_lint_bare_trait(&mut self, span: Span, id: NodeId, is_global: bool) { // FIXME(davidtwco): This is a hack to detect macros which produce spans of the // call site which do not have a macro backtrace. See #61963. let is_macro_callsite = self.sess.source_map() .span_to_snippet(span) .map(|snippet| snippet.starts_with("#[")) .unwrap_or(true); if !is_macro_callsite { self.resolver.lint_buffer().buffer_lint_with_diagnostic( builtin::BARE_TRAIT_OBJECTS, id, span, "trait objects without an explicit `dyn` are deprecated", builtin::BuiltinLintDiagnostics::BareTraitObject(span, is_global), ) } } } fn body_ids(bodies: &BTreeMap) -> Vec { // Sorting by span ensures that we get things in order within a // file, and also puts the files in a sensible order. let mut body_ids: Vec<_> = bodies.keys().cloned().collect(); body_ids.sort_by_key(|b| bodies[b].value.span); body_ids } /// Checks if the specified expression is a built-in range literal. /// (See: `LoweringContext::lower_expr()`). pub fn is_range_literal(sess: &Session, expr: &hir::Expr) -> bool { use hir::{Path, QPath, ExprKind, TyKind}; // Returns whether the given path represents a (desugared) range, // either in std or core, i.e. has either a `::std::ops::Range` or // `::core::ops::Range` prefix. fn is_range_path(path: &Path) -> bool { let segs: Vec<_> = path.segments.iter().map(|seg| seg.ident.as_str().to_string()).collect(); let segs: Vec<_> = segs.iter().map(|seg| &**seg).collect(); // "{{root}}" is the equivalent of `::` prefix in `Path`. if let ["{{root}}", std_core, "ops", range] = segs.as_slice() { (*std_core == "std" || *std_core == "core") && range.starts_with("Range") } else { false } }; // Check whether a span corresponding to a range expression is a // range literal, rather than an explicit struct or `new()` call. fn is_lit(sess: &Session, span: &Span) -> bool { let source_map = sess.source_map(); let end_point = source_map.end_point(*span); if let Ok(end_string) = source_map.span_to_snippet(end_point) { !(end_string.ends_with("}") || end_string.ends_with(")")) } else { false } }; match expr.kind { // All built-in range literals but `..=` and `..` desugar to `Struct`s. ExprKind::Struct(ref qpath, _, _) => { if let QPath::Resolved(None, ref path) = **qpath { return is_range_path(&path) && is_lit(sess, &expr.span); } } // `..` desugars to its struct path. ExprKind::Path(QPath::Resolved(None, ref path)) => { return is_range_path(&path) && is_lit(sess, &expr.span); } // `..=` desugars into `::std::ops::RangeInclusive::new(...)`. ExprKind::Call(ref func, _) => { if let ExprKind::Path(QPath::TypeRelative(ref ty, ref segment)) = func.kind { if let TyKind::Path(QPath::Resolved(None, ref path)) = ty.kind { let new_call = segment.ident.as_str() == "new"; return is_range_path(&path) && is_lit(sess, &expr.span) && new_call; } } } _ => {} } false }