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[rustc.git] / compiler / rustc_ast_lowering / src / item.rs
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dfeec247 1use super::{AnonymousLifetimeMode, LoweringContext, ParamMode};
f035d41b 2use super::{ImplTraitContext, ImplTraitPosition};
ba9703b0 3use crate::Arena;
dfeec247 4
74b04a01 5use rustc_ast::node_id::NodeMap;
ba9703b0 6use rustc_ast::ptr::P;
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7use rustc_ast::visit::{self, AssocCtxt, FnCtxt, FnKind, Visitor};
8use rustc_ast::*;
f035d41b 9use rustc_data_structures::fx::FxHashSet;
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10use rustc_errors::struct_span_err;
11use rustc_hir as hir;
12use rustc_hir::def::{DefKind, Res};
ba9703b0 13use rustc_hir::def_id::LocalDefId;
dfeec247 14use rustc_span::source_map::{respan, DesugaringKind};
f9f354fc 15use rustc_span::symbol::{kw, sym, Ident};
dfeec247 16use rustc_span::Span;
60c5eb7d 17use rustc_target::spec::abi;
dfeec247 18use smallvec::{smallvec, SmallVec};
3dfed10e 19use tracing::debug;
60c5eb7d 20
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21use std::mem;
22
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23pub(super) struct ItemLowerer<'a, 'lowering, 'hir> {
24 pub(super) lctx: &'a mut LoweringContext<'lowering, 'hir>,
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25}
26
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27impl ItemLowerer<'_, '_, '_> {
28 fn with_trait_impl_ref(&mut self, impl_ref: &Option<TraitRef>, f: impl FnOnce(&mut Self)) {
416331ca 29 let old = self.lctx.is_in_trait_impl;
1b1a35ee 30 self.lctx.is_in_trait_impl = impl_ref.is_some();
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31 f(self);
32 self.lctx.is_in_trait_impl = old;
33 }
34}
35
dfeec247 36impl<'a> Visitor<'a> for ItemLowerer<'a, '_, '_> {
dfeec247 37 fn visit_item(&mut self, item: &'a Item) {
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38 let mut item_hir_id = None;
39 self.lctx.with_hir_id_owner(item.id, |lctx| {
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40 lctx.without_in_scope_lifetime_defs(|lctx| {
41 if let Some(hir_item) = lctx.lower_item(item) {
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42 let id = lctx.insert_item(hir_item);
43 item_hir_id = Some(id);
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44 }
45 })
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46 });
47
48 if let Some(hir_id) = item_hir_id {
49 self.lctx.with_parent_item_lifetime_defs(hir_id, |this| {
50 let this = &mut ItemLowerer { lctx: this };
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51 match item.kind {
52 ItemKind::Mod(..) => {
53 let def_id = this.lctx.lower_node_id(item.id).expect_owner();
54 let old_current_module =
55 mem::replace(&mut this.lctx.current_module, def_id);
56 visit::walk_item(this, item);
57 this.lctx.current_module = old_current_module;
58 }
59 ItemKind::Impl(box ImplKind { ref of_trait, .. }) => {
60 this.with_trait_impl_ref(of_trait, |this| visit::walk_item(this, item));
61 }
62 _ => visit::walk_item(this, item),
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63 }
64 });
65 }
66 }
67
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68 fn visit_fn(&mut self, fk: FnKind<'a>, sp: Span, _: NodeId) {
69 match fk {
70 FnKind::Fn(FnCtxt::Foreign, _, sig, _, _) => {
71 self.visit_fn_header(&sig.header);
72 visit::walk_fn_decl(self, &sig.decl);
73 // Don't visit the foreign function body even if it has one, since lowering the
74 // body would have no meaning and will have already been caught as a parse error.
75 }
76 _ => visit::walk_fn(self, fk, sp),
77 }
78 }
79
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80 fn visit_assoc_item(&mut self, item: &'a AssocItem, ctxt: AssocCtxt) {
81 self.lctx.with_hir_id_owner(item.id, |lctx| match ctxt {
82 AssocCtxt::Trait => {
83 let hir_item = lctx.lower_trait_item(item);
6a06907d 84 let id = hir_item.trait_item_id();
74b04a01 85 lctx.trait_items.insert(id, hir_item);
6a06907d 86 lctx.modules.entry(lctx.current_module).or_default().trait_items.insert(id);
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87 }
88 AssocCtxt::Impl => {
89 let hir_item = lctx.lower_impl_item(item);
6a06907d 90 let id = hir_item.impl_item_id();
74b04a01 91 lctx.impl_items.insert(id, hir_item);
6a06907d 92 lctx.modules.entry(lctx.current_module).or_default().impl_items.insert(id);
74b04a01 93 }
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94 });
95
74b04a01 96 visit::walk_assoc_item(self, item, ctxt);
416331ca 97 }
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98
99 fn visit_foreign_item(&mut self, item: &'a ForeignItem) {
100 self.lctx.allocate_hir_id_counter(item.id);
101 self.lctx.with_hir_id_owner(item.id, |lctx| {
102 let hir_item = lctx.lower_foreign_item(item);
6a06907d 103 let id = hir_item.foreign_item_id();
fc512014 104 lctx.foreign_items.insert(id, hir_item);
6a06907d 105 lctx.modules.entry(lctx.current_module).or_default().foreign_items.insert(id);
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106 });
107
108 visit::walk_foreign_item(self, item);
109 }
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110}
111
dfeec247 112impl<'hir> LoweringContext<'_, 'hir> {
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113 // Same as the method above, but accepts `hir::GenericParam`s
114 // instead of `ast::GenericParam`s.
115 // This should only be used with generics that have already had their
116 // in-band lifetimes added. In practice, this means that this function is
117 // only used when lowering a child item of a trait or impl.
118 fn with_parent_item_lifetime_defs<T>(
119 &mut self,
6a06907d 120 parent_hir_id: hir::ItemId,
dfeec247 121 f: impl FnOnce(&mut LoweringContext<'_, '_>) -> T,
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122 ) -> T {
123 let old_len = self.in_scope_lifetimes.len();
124
e74abb32 125 let parent_generics = match self.items.get(&parent_hir_id).unwrap().kind {
5869c6ff 126 hir::ItemKind::Impl(hir::Impl { ref generics, .. })
6a06907d 127 | hir::ItemKind::Trait(_, _, ref generics, ..) => generics.params,
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128 _ => &[],
129 };
130 let lt_def_names = parent_generics.iter().filter_map(|param| match param.kind {
ba9703b0 131 hir::GenericParamKind::Lifetime { .. } => Some(param.name.normalize_to_macros_2_0()),
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132 _ => None,
133 });
134 self.in_scope_lifetimes.extend(lt_def_names);
135
136 let res = f(self);
137
138 self.in_scope_lifetimes.truncate(old_len);
139 res
140 }
141
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142 // Clears (and restores) the `in_scope_lifetimes` field. Used when
143 // visiting nested items, which never inherit in-scope lifetimes
144 // from their surrounding environment.
145 fn without_in_scope_lifetime_defs<T>(
146 &mut self,
dfeec247 147 f: impl FnOnce(&mut LoweringContext<'_, '_>) -> T,
e1599b0c 148 ) -> T {
6a06907d 149 let old_in_scope_lifetimes = mem::replace(&mut self.in_scope_lifetimes, vec![]);
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150
151 // this vector is only used when walking over impl headers,
152 // input types, and the like, and should not be non-empty in
153 // between items
154 assert!(self.lifetimes_to_define.is_empty());
155
156 let res = f(self);
157
158 assert!(self.in_scope_lifetimes.is_empty());
159 self.in_scope_lifetimes = old_in_scope_lifetimes;
160
161 res
162 }
163
6a06907d 164 pub(super) fn lower_mod(&mut self, items: &[P<Item>], inner: Span) -> hir::Mod<'hir> {
416331ca 165 hir::Mod {
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166 inner,
167 item_ids: self.arena.alloc_from_iter(items.iter().flat_map(|x| self.lower_item_id(x))),
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168 }
169 }
170
171 pub(super) fn lower_item_id(&mut self, i: &Item) -> SmallVec<[hir::ItemId; 1]> {
e74abb32 172 let node_ids = match i.kind {
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173 ItemKind::Use(ref use_tree) => {
174 let mut vec = smallvec![i.id];
175 self.lower_item_id_use_tree(use_tree, i.id, &mut vec);
176 vec
177 }
178 ItemKind::MacroDef(..) => SmallVec::new(),
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179 ItemKind::Fn(..) | ItemKind::Impl(box ImplKind { of_trait: None, .. }) => {
180 smallvec![i.id]
181 }
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182 _ => smallvec![i.id],
183 };
184
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185 node_ids
186 .into_iter()
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187 .map(|node_id| hir::ItemId {
188 def_id: self.allocate_hir_id_counter(node_id).expect_owner(),
189 })
dfeec247 190 .collect()
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191 }
192
193 fn lower_item_id_use_tree(
194 &mut self,
195 tree: &UseTree,
196 base_id: NodeId,
dfeec247 197 vec: &mut SmallVec<[NodeId; 1]>,
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198 ) {
199 match tree.kind {
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200 UseTreeKind::Nested(ref nested_vec) => {
201 for &(ref nested, id) in nested_vec {
202 vec.push(id);
203 self.lower_item_id_use_tree(nested, id, vec);
204 }
205 }
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206 UseTreeKind::Glob => {}
207 UseTreeKind::Simple(_, id1, id2) => {
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208 for (_, &id) in
209 self.expect_full_res_from_use(base_id).skip(1).zip([id1, id2].iter())
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210 {
211 vec.push(id);
212 }
dfeec247 213 }
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214 }
215 }
216
dfeec247 217 pub fn lower_item(&mut self, i: &Item) -> Option<hir::Item<'hir>> {
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218 let mut ident = i.ident;
219 let mut vis = self.lower_visibility(&i.vis, None);
416331ca 220
ba9703b0 221 if let ItemKind::MacroDef(MacroDef { ref body, macro_rules }) = i.kind {
3dfed10e 222 if !macro_rules || self.sess.contains_name(&i.attrs, sym::macro_export) {
416331ca 223 let hir_id = self.lower_node_id(i.id);
6a06907d 224 self.lower_attrs(hir_id, &i.attrs);
ba9703b0 225 let body = P(self.lower_mac_args(body));
416331ca 226 self.exported_macros.push(hir::MacroDef {
ba9703b0 227 ident,
416331ca 228 vis,
6a06907d 229 def_id: hir_id.expect_owner(),
416331ca 230 span: i.span,
ba9703b0 231 ast: MacroDef { body, macro_rules },
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232 });
233 } else {
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234 for a in i.attrs.iter() {
235 let a = self.lower_attr(a);
236 self.non_exported_macro_attrs.push(a);
237 }
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238 }
239 return None;
240 }
241
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242 let hir_id = self.lower_node_id(i.id);
243 let attrs = self.lower_attrs(hir_id, &i.attrs);
244 let kind = self.lower_item_kind(i.span, i.id, hir_id, &mut ident, attrs, &mut vis, &i.kind);
245 Some(hir::Item { def_id: hir_id.expect_owner(), ident, kind, vis, span: i.span })
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246 }
247
248 fn lower_item_kind(
249 &mut self,
dfeec247 250 span: Span,
416331ca 251 id: NodeId,
6a06907d 252 hir_id: hir::HirId,
416331ca 253 ident: &mut Ident,
6a06907d 254 attrs: Option<&'hir [Attribute]>,
dfeec247 255 vis: &mut hir::Visibility<'hir>,
416331ca 256 i: &ItemKind,
dfeec247 257 ) -> hir::ItemKind<'hir> {
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258 match *i {
259 ItemKind::ExternCrate(orig_name) => hir::ItemKind::ExternCrate(orig_name),
260 ItemKind::Use(ref use_tree) => {
261 // Start with an empty prefix.
1b1a35ee 262 let prefix = Path { segments: vec![], span: use_tree.span, tokens: None };
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263
264 self.lower_use_tree(use_tree, &prefix, id, vis, ident, attrs)
265 }
266 ItemKind::Static(ref t, m, ref e) => {
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267 let (ty, body_id) = self.lower_const_item(t, span, e.as_deref());
268 hir::ItemKind::Static(ty, m, body_id)
416331ca 269 }
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270 ItemKind::Const(_, ref t, ref e) => {
271 let (ty, body_id) = self.lower_const_item(t, span, e.as_deref());
272 hir::ItemKind::Const(ty, body_id)
416331ca 273 }
5869c6ff 274 ItemKind::Fn(box FnKind(
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275 _,
276 FnSig { ref decl, header, span: fn_sig_span },
277 ref generics,
278 ref body,
5869c6ff 279 )) => {
f035d41b 280 let fn_def_id = self.resolver.local_def_id(id);
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281 self.with_new_scopes(|this| {
282 this.current_item = Some(ident.span);
283
284 // Note: we don't need to change the return type from `T` to
285 // `impl Future<Output = T>` here because lower_body
286 // only cares about the input argument patterns in the function
287 // declaration (decl), not the return types.
74b04a01 288 let asyncness = header.asyncness;
dfeec247 289 let body_id =
74b04a01 290 this.lower_maybe_async_body(span, &decl, asyncness, body.as_deref());
416331ca 291
60c5eb7d 292 let (generics, decl) = this.add_in_band_defs(
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293 generics,
294 fn_def_id,
295 AnonymousLifetimeMode::PassThrough,
dfeec247 296 |this, idty| {
74b04a01 297 let ret_id = asyncness.opt_return_id();
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298 this.lower_fn_decl(
299 &decl,
300 Some((fn_def_id.to_def_id(), idty)),
301 true,
302 ret_id,
303 )
dfeec247 304 },
416331ca 305 );
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306 let sig = hir::FnSig {
307 decl,
5869c6ff 308 header: this.lower_fn_header(header, fn_sig_span, id),
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309 span: fn_sig_span,
310 };
60c5eb7d 311 hir::ItemKind::Fn(sig, generics, body_id)
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312 })
313 }
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314 ItemKind::Mod(_, ref mod_kind) => match mod_kind {
315 ModKind::Loaded(items, _, inner_span) => {
316 hir::ItemKind::Mod(self.lower_mod(items, *inner_span))
317 }
318 ModKind::Unloaded => panic!("`mod` items should have been loaded by now"),
319 },
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320 ItemKind::ForeignMod(ref fm) => {
321 if fm.abi.is_none() {
6a06907d 322 self.maybe_lint_missing_abi(span, id, abi::Abi::C { unwind: false });
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323 }
324 hir::ItemKind::ForeignMod {
6a06907d 325 abi: fm.abi.map_or(abi::Abi::C { unwind: false }, |abi| self.lower_abi(abi)),
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326 items: self
327 .arena
328 .alloc_from_iter(fm.items.iter().map(|x| self.lower_foreign_item_ref(x))),
329 }
330 }
416331ca 331 ItemKind::GlobalAsm(ref ga) => hir::ItemKind::GlobalAsm(self.lower_global_asm(ga)),
5869c6ff 332 ItemKind::TyAlias(box TyAliasKind(_, ref gen, _, Some(ref ty))) => {
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333 // We lower
334 //
335 // type Foo = impl Trait
336 //
337 // to
338 //
339 // type Foo = Foo1
340 // opaque type Foo1: Trait
341 let ty = self.lower_ty(
342 ty,
343 ImplTraitContext::OtherOpaqueTy {
344 capturable_lifetimes: &mut FxHashSet::default(),
6a06907d 345 origin: hir::OpaqueTyOrigin::TyAlias,
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346 },
347 );
348 let generics = self.lower_generics(gen, ImplTraitContext::disallowed());
349 hir::ItemKind::TyAlias(ty, generics)
350 }
5869c6ff 351 ItemKind::TyAlias(box TyAliasKind(_, ref generics, _, None)) => {
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352 let ty = self.arena.alloc(self.ty(span, hir::TyKind::Err));
353 let generics = self.lower_generics(generics, ImplTraitContext::disallowed());
354 hir::ItemKind::TyAlias(ty, generics)
355 }
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356 ItemKind::Enum(ref enum_definition, ref generics) => hir::ItemKind::Enum(
357 hir::EnumDef {
358 variants: self.arena.alloc_from_iter(
359 enum_definition.variants.iter().map(|x| self.lower_variant(x)),
360 ),
361 },
362 self.lower_generics(generics, ImplTraitContext::disallowed()),
363 ),
416331ca 364 ItemKind::Struct(ref struct_def, ref generics) => {
6a06907d 365 let struct_def = self.lower_variant_data(hir_id, struct_def);
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366 hir::ItemKind::Struct(
367 struct_def,
368 self.lower_generics(generics, ImplTraitContext::disallowed()),
369 )
370 }
371 ItemKind::Union(ref vdata, ref generics) => {
6a06907d 372 let vdata = self.lower_variant_data(hir_id, vdata);
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373 hir::ItemKind::Union(
374 vdata,
375 self.lower_generics(generics, ImplTraitContext::disallowed()),
376 )
377 }
5869c6ff 378 ItemKind::Impl(box ImplKind {
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379 unsafety,
380 polarity,
381 defaultness,
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382 constness,
383 generics: ref ast_generics,
384 of_trait: ref trait_ref,
385 self_ty: ref ty,
386 items: ref impl_items,
5869c6ff 387 }) => {
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388 // Lower the "impl header" first. This ordering is important
389 // for in-band lifetimes! Consider `'a` here:
390 //
391 // impl Foo<'a> for u32 {
392 // fn method(&'a self) { .. }
393 // }
394 //
395 // Because we start by lowering the `Foo<'a> for u32`
396 // part, we will add `'a` to the list of generics on
397 // the impl. When we then encounter it later in the
398 // method, it will not be considered an in-band
399 // lifetime to be added, but rather a reference to a
400 // parent lifetime.
6a06907d 401 let lowered_trait_def_id = self.lower_node_id(id).expect_owner();
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402 let (generics, (trait_ref, lowered_ty)) = self.add_in_band_defs(
403 ast_generics,
6a06907d 404 lowered_trait_def_id,
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405 AnonymousLifetimeMode::CreateParameter,
406 |this, _| {
407 let trait_ref = trait_ref.as_ref().map(|trait_ref| {
408 this.lower_trait_ref(trait_ref, ImplTraitContext::disallowed())
409 });
410
411 if let Some(ref trait_ref) = trait_ref {
412 if let Res::Def(DefKind::Trait, def_id) = trait_ref.path.res {
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413 this.trait_impls
414 .entry(def_id)
415 .or_default()
6a06907d 416 .push(lowered_trait_def_id);
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417 }
418 }
419
420 let lowered_ty = this.lower_ty(ty, ImplTraitContext::disallowed());
421
422 (trait_ref, lowered_ty)
423 },
424 );
425
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426 let new_impl_items =
427 self.with_in_scope_lifetime_defs(&ast_generics.params, |this| {
428 this.arena.alloc_from_iter(
429 impl_items.iter().map(|item| this.lower_impl_item_ref(item)),
430 )
431 });
416331ca 432
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433 // `defaultness.has_value()` is never called for an `impl`, always `true` in order
434 // to not cause an assertion failure inside the `lower_defaultness` function.
435 let has_val = true;
436 let (defaultness, defaultness_span) = self.lower_defaultness(defaultness, has_val);
5869c6ff 437 hir::ItemKind::Impl(hir::Impl {
74b04a01 438 unsafety: self.lower_unsafety(unsafety),
60c5eb7d 439 polarity,
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440 defaultness,
441 defaultness_span,
74b04a01 442 constness: self.lower_constness(constness),
416331ca 443 generics,
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444 of_trait: trait_ref,
445 self_ty: lowered_ty,
446 items: new_impl_items,
5869c6ff 447 })
416331ca 448 }
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449 ItemKind::Trait(box TraitKind(
450 is_auto,
451 unsafety,
452 ref generics,
453 ref bounds,
454 ref items,
455 )) => {
416331ca 456 let bounds = self.lower_param_bounds(bounds, ImplTraitContext::disallowed());
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457 let items = self
458 .arena
459 .alloc_from_iter(items.iter().map(|item| self.lower_trait_item_ref(item)));
416331ca 460 hir::ItemKind::Trait(
60c5eb7d 461 is_auto,
74b04a01 462 self.lower_unsafety(unsafety),
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463 self.lower_generics(generics, ImplTraitContext::disallowed()),
464 bounds,
465 items,
466 )
467 }
468 ItemKind::TraitAlias(ref generics, ref bounds) => hir::ItemKind::TraitAlias(
469 self.lower_generics(generics, ImplTraitContext::disallowed()),
470 self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
471 ),
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472 ItemKind::MacroDef(..) | ItemKind::MacCall(..) => {
473 panic!("`TyMac` should have been expanded by now")
dfeec247 474 }
416331ca 475 }
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476 }
477
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478 fn lower_const_item(
479 &mut self,
480 ty: &Ty,
481 span: Span,
482 body: Option<&Expr>,
483 ) -> (&'hir hir::Ty<'hir>, hir::BodyId) {
f035d41b 484 let mut capturable_lifetimes;
74b04a01 485 let itctx = if self.sess.features_untracked().impl_trait_in_bindings {
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486 capturable_lifetimes = FxHashSet::default();
487 ImplTraitContext::OtherOpaqueTy {
488 capturable_lifetimes: &mut capturable_lifetimes,
489 origin: hir::OpaqueTyOrigin::Misc,
490 }
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491 } else {
492 ImplTraitContext::Disallowed(ImplTraitPosition::Binding)
493 };
494 let ty = self.lower_ty(ty, itctx);
495 (ty, self.lower_const_body(span, body))
496 }
497
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498 fn lower_use_tree(
499 &mut self,
500 tree: &UseTree,
501 prefix: &Path,
502 id: NodeId,
dfeec247 503 vis: &mut hir::Visibility<'hir>,
416331ca 504 ident: &mut Ident,
6a06907d 505 attrs: Option<&'hir [Attribute]>,
dfeec247 506 ) -> hir::ItemKind<'hir> {
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507 debug!("lower_use_tree(tree={:?})", tree);
508 debug!("lower_use_tree: vis = {:?}", vis);
509
510 let path = &tree.prefix;
dfeec247 511 let segments = prefix.segments.iter().chain(path.segments.iter()).cloned().collect();
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512
513 match tree.kind {
514 UseTreeKind::Simple(rename, id1, id2) => {
515 *ident = tree.ident();
516
517 // First, apply the prefix to the path.
1b1a35ee 518 let mut path = Path { segments, span: path.span, tokens: None };
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519
520 // Correctly resolve `self` imports.
521 if path.segments.len() > 1
522 && path.segments.last().unwrap().ident.name == kw::SelfLower
523 {
524 let _ = path.segments.pop();
525 if rename.is_none() {
526 *ident = path.segments.last().unwrap().ident;
527 }
528 }
529
530 let mut resolutions = self.expect_full_res_from_use(id);
531 // We want to return *something* from this function, so hold onto the first item
532 // for later.
533 let ret_res = self.lower_res(resolutions.next().unwrap_or(Res::Err));
534
535 // Here, we are looping over namespaces, if they exist for the definition
536 // being imported. We only handle type and value namespaces because we
537 // won't be dealing with macros in the rest of the compiler.
538 // Essentially a single `use` which imports two names is desugared into
539 // two imports.
540 for (res, &new_node_id) in resolutions.zip([id1, id2].iter()) {
541 let ident = *ident;
542 let mut path = path.clone();
543 for seg in &mut path.segments {
60c5eb7d 544 seg.id = self.resolver.next_node_id();
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545 }
546 let span = path.span;
547
548 self.with_hir_id_owner(new_node_id, |this| {
549 let new_id = this.lower_node_id(new_node_id);
550 let res = this.lower_res(res);
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551 let path = this.lower_path_extra(res, &path, ParamMode::Explicit, None);
552 let kind = hir::ItemKind::Use(path, hir::UseKind::Single);
416331ca 553 let vis = this.rebuild_vis(&vis);
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554 if let Some(attrs) = attrs {
555 this.attrs.insert(new_id, attrs);
556 }
416331ca 557
dfeec247 558 this.insert_item(hir::Item {
6a06907d 559 def_id: new_id.expect_owner(),
dfeec247 560 ident,
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561 kind,
562 vis,
563 span,
564 });
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565 });
566 }
567
dfeec247 568 let path = self.lower_path_extra(ret_res, &path, ParamMode::Explicit, None);
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569 hir::ItemKind::Use(path, hir::UseKind::Single)
570 }
571 UseTreeKind::Glob => {
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572 let path = self.lower_path(
573 id,
574 &Path { segments, span: path.span, tokens: None },
575 ParamMode::Explicit,
576 );
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577 hir::ItemKind::Use(path, hir::UseKind::Glob)
578 }
579 UseTreeKind::Nested(ref trees) => {
580 // Nested imports are desugared into simple imports.
581 // So, if we start with
582 //
583 // ```
584 // pub(x) use foo::{a, b};
585 // ```
586 //
587 // we will create three items:
588 //
589 // ```
590 // pub(x) use foo::a;
591 // pub(x) use foo::b;
592 // pub(x) use foo::{}; // <-- this is called the `ListStem`
593 // ```
594 //
595 // The first two are produced by recursively invoking
596 // `lower_use_tree` (and indeed there may be things
597 // like `use foo::{a::{b, c}}` and so forth). They
598 // wind up being directly added to
599 // `self.items`. However, the structure of this
600 // function also requires us to return one item, and
601 // for that we return the `{}` import (called the
602 // `ListStem`).
603
1b1a35ee 604 let prefix = Path { segments, span: prefix.span.to(path.span), tokens: None };
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605
606 // Add all the nested `PathListItem`s to the HIR.
607 for &(ref use_tree, id) in trees {
608 let new_hir_id = self.lower_node_id(id);
609
610 let mut prefix = prefix.clone();
611
612 // Give the segments new node-ids since they are being cloned.
613 for seg in &mut prefix.segments {
60c5eb7d 614 seg.id = self.resolver.next_node_id();
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615 }
616
617 // Each `use` import is an item and thus are owners of the
618 // names in the path. Up to this point the nested import is
619 // the current owner, since we want each desugared import to
620 // own its own names, we have to adjust the owner before
621 // lowering the rest of the import.
622 self.with_hir_id_owner(id, |this| {
623 let mut vis = this.rebuild_vis(&vis);
624 let mut ident = *ident;
625
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626 let kind =
627 this.lower_use_tree(use_tree, &prefix, id, &mut vis, &mut ident, attrs);
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628 if let Some(attrs) = attrs {
629 this.attrs.insert(new_hir_id, attrs);
630 }
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631
632 this.insert_item(hir::Item {
6a06907d 633 def_id: new_hir_id.expect_owner(),
dfeec247 634 ident,
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635 kind,
636 vis,
637 span: use_tree.span,
638 });
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639 });
640 }
641
642 // Subtle and a bit hacky: we lower the privacy level
643 // of the list stem to "private" most of the time, but
644 // not for "restricted" paths. The key thing is that
645 // we don't want it to stay as `pub` (with no caveats)
646 // because that affects rustdoc and also the lints
647 // about `pub` items. But we can't *always* make it
648 // private -- particularly not for restricted paths --
649 // because it contains node-ids that would then be
650 // unused, failing the check that HirIds are "densely
651 // assigned".
652 match vis.node {
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653 hir::VisibilityKind::Public
654 | hir::VisibilityKind::Crate(_)
655 | hir::VisibilityKind::Inherited => {
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656 *vis = respan(prefix.span.shrink_to_lo(), hir::VisibilityKind::Inherited);
657 }
658 hir::VisibilityKind::Restricted { .. } => {
659 // Do nothing here, as described in the comment on the match.
660 }
661 }
662
663 let res = self.expect_full_res_from_use(id).next().unwrap_or(Res::Err);
664 let res = self.lower_res(res);
dfeec247 665 let path = self.lower_path_extra(res, &prefix, ParamMode::Explicit, None);
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666 hir::ItemKind::Use(path, hir::UseKind::ListStem)
667 }
668 }
669 }
670
671 /// Paths like the visibility path in `pub(super) use foo::{bar, baz}` are repeated
672 /// many times in the HIR tree; for each occurrence, we need to assign distinct
673 /// `NodeId`s. (See, e.g., #56128.)
dfeec247 674 fn rebuild_use_path(&mut self, path: &hir::Path<'hir>) -> &'hir hir::Path<'hir> {
416331ca 675 debug!("rebuild_use_path(path = {:?})", path);
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676 let segments =
677 self.arena.alloc_from_iter(path.segments.iter().map(|seg| hir::PathSegment {
678 ident: seg.ident,
679 hir_id: seg.hir_id.map(|_| self.next_id()),
680 res: seg.res,
681 args: None,
682 infer_args: seg.infer_args,
683 }));
684 self.arena.alloc(hir::Path { span: path.span, res: path.res, segments })
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685 }
686
dfeec247 687 fn rebuild_vis(&mut self, vis: &hir::Visibility<'hir>) -> hir::Visibility<'hir> {
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688 let vis_kind = match vis.node {
689 hir::VisibilityKind::Public => hir::VisibilityKind::Public,
690 hir::VisibilityKind::Crate(sugar) => hir::VisibilityKind::Crate(sugar),
691 hir::VisibilityKind::Inherited => hir::VisibilityKind::Inherited,
692 hir::VisibilityKind::Restricted { ref path, hir_id: _ } => {
693 hir::VisibilityKind::Restricted {
dfeec247 694 path: self.rebuild_use_path(path),
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695 hir_id: self.next_id(),
696 }
697 }
698 };
699 respan(vis.span, vis_kind)
700 }
701
dfeec247 702 fn lower_foreign_item(&mut self, i: &ForeignItem) -> hir::ForeignItem<'hir> {
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703 let hir_id = self.lower_node_id(i.id);
704 let def_id = hir_id.expect_owner();
705 self.lower_attrs(hir_id, &i.attrs);
416331ca 706 hir::ForeignItem {
6a06907d 707 def_id,
416331ca 708 ident: i.ident,
e74abb32 709 kind: match i.kind {
5869c6ff 710 ForeignItemKind::Fn(box FnKind(_, ref sig, ref generics, _)) => {
74b04a01 711 let fdec = &sig.decl;
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712 let (generics, (fn_dec, fn_args)) = self.add_in_band_defs(
713 generics,
714 def_id,
715 AnonymousLifetimeMode::PassThrough,
716 |this, _| {
717 (
e1599b0c 718 // Disallow `impl Trait` in foreign items.
416331ca 719 this.lower_fn_decl(fdec, None, false, None),
e1599b0c 720 this.lower_fn_params_to_names(fdec),
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721 )
722 },
723 );
724
725 hir::ForeignItemKind::Fn(fn_dec, fn_args, generics)
726 }
74b04a01 727 ForeignItemKind::Static(ref t, m, _) => {
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728 let ty = self.lower_ty(t, ImplTraitContext::disallowed());
729 hir::ForeignItemKind::Static(ty, m)
416331ca 730 }
74b04a01 731 ForeignItemKind::TyAlias(..) => hir::ForeignItemKind::Type,
ba9703b0 732 ForeignItemKind::MacCall(_) => panic!("macro shouldn't exist here"),
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733 },
734 vis: self.lower_visibility(&i.vis, None),
735 span: i.span,
736 }
737 }
738
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739 fn lower_foreign_item_ref(&mut self, i: &ForeignItem) -> hir::ForeignItemRef<'hir> {
740 hir::ForeignItemRef {
6a06907d 741 id: hir::ForeignItemId { def_id: self.lower_node_id(i.id).expect_owner() },
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742 ident: i.ident,
743 span: i.span,
744 vis: self.lower_visibility(&i.vis, Some(i.id)),
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745 }
746 }
747
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748 fn lower_global_asm(&mut self, ga: &GlobalAsm) -> &'hir hir::GlobalAsm {
749 self.arena.alloc(hir::GlobalAsm { asm: ga.asm })
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750 }
751
dfeec247 752 fn lower_variant(&mut self, v: &Variant) -> hir::Variant<'hir> {
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753 let id = self.lower_node_id(v.id);
754 self.lower_attrs(id, &v.attrs);
e1599b0c 755 hir::Variant {
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756 id,
757 data: self.lower_variant_data(id, &v.data),
e1599b0c 758 disr_expr: v.disr_expr.as_ref().map(|e| self.lower_anon_const(e)),
e1599b0c 759 ident: v.ident,
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760 span: v.span,
761 }
762 }
763
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764 fn lower_variant_data(
765 &mut self,
766 parent_id: hir::HirId,
767 vdata: &VariantData,
768 ) -> hir::VariantData<'hir> {
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769 match *vdata {
770 VariantData::Struct(ref fields, recovered) => hir::VariantData::Struct(
dfeec247 771 self.arena
6a06907d 772 .alloc_from_iter(fields.iter().enumerate().map(|f| self.lower_field_def(f))),
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773 recovered,
774 ),
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775 VariantData::Tuple(ref fields, id) => {
776 let ctor_id = self.lower_node_id(id);
777 self.alias_attrs(ctor_id, parent_id);
778 hir::VariantData::Tuple(
779 self.arena.alloc_from_iter(
780 fields.iter().enumerate().map(|f| self.lower_field_def(f)),
781 ),
782 ctor_id,
783 )
784 }
785 VariantData::Unit(id) => {
786 let ctor_id = self.lower_node_id(id);
787 self.alias_attrs(ctor_id, parent_id);
788 hir::VariantData::Unit(ctor_id)
789 }
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790 }
791 }
792
6a06907d 793 fn lower_field_def(&mut self, (index, f): (usize, &FieldDef)) -> hir::FieldDef<'hir> {
e74abb32 794 let ty = if let TyKind::Path(ref qself, ref path) = f.ty.kind {
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795 let t = self.lower_path_ty(
796 &f.ty,
797 qself,
798 path,
799 ParamMode::ExplicitNamed, // no `'_` in declarations (Issue #61124)
dfeec247 800 ImplTraitContext::disallowed(),
416331ca 801 );
dfeec247 802 self.arena.alloc(t)
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803 } else {
804 self.lower_ty(&f.ty, ImplTraitContext::disallowed())
805 };
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806 let hir_id = self.lower_node_id(f.id);
807 self.lower_attrs(hir_id, &f.attrs);
808 hir::FieldDef {
416331ca 809 span: f.span,
6a06907d 810 hir_id,
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811 ident: match f.ident {
812 Some(ident) => ident,
813 // FIXME(jseyfried): positional field hygiene.
814 None => Ident::new(sym::integer(index), f.span),
815 },
816 vis: self.lower_visibility(&f.vis, None),
817 ty,
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818 }
819 }
820
dfeec247 821 fn lower_trait_item(&mut self, i: &AssocItem) -> hir::TraitItem<'hir> {
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822 let hir_id = self.lower_node_id(i.id);
823 let trait_item_def_id = hir_id.expect_owner();
416331ca 824
e74abb32 825 let (generics, kind) = match i.kind {
74b04a01 826 AssocItemKind::Const(_, ref ty, ref default) => {
dfeec247 827 let ty = self.lower_ty(ty, ImplTraitContext::disallowed());
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828 let body = default.as_ref().map(|x| self.lower_const_body(i.span, Some(x)));
829 (hir::Generics::empty(), hir::TraitItemKind::Const(ty, body))
dfeec247 830 }
5869c6ff 831 AssocItemKind::Fn(box FnKind(_, ref sig, ref generics, None)) => {
e1599b0c 832 let names = self.lower_fn_params_to_names(&sig.decl);
dfeec247 833 let (generics, sig) =
5869c6ff 834 self.lower_method_sig(generics, sig, trait_item_def_id, false, None, i.id);
ba9703b0 835 (generics, hir::TraitItemKind::Fn(sig, hir::TraitFn::Required(names)))
416331ca 836 }
5869c6ff 837 AssocItemKind::Fn(box FnKind(_, ref sig, ref generics, Some(ref body))) => {
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838 let body_id = self.lower_fn_body_block(i.span, &sig.decl, Some(body));
839 let (generics, sig) =
5869c6ff 840 self.lower_method_sig(generics, sig, trait_item_def_id, false, None, i.id);
ba9703b0 841 (generics, hir::TraitItemKind::Fn(sig, hir::TraitFn::Provided(body_id)))
416331ca 842 }
5869c6ff 843 AssocItemKind::TyAlias(box TyAliasKind(_, ref generics, ref bounds, ref default)) => {
dfeec247 844 let ty = default.as_ref().map(|x| self.lower_ty(x, ImplTraitContext::disallowed()));
74b04a01 845 let generics = self.lower_generics(generics, ImplTraitContext::disallowed());
e74abb32 846 let kind = hir::TraitItemKind::Type(
416331ca 847 self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
dfeec247 848 ty,
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849 );
850
e74abb32 851 (generics, kind)
dfeec247 852 }
ba9703b0 853 AssocItemKind::MacCall(..) => panic!("macro item shouldn't exist at this point"),
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854 };
855
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856 self.lower_attrs(hir_id, &i.attrs);
857 hir::TraitItem { def_id: trait_item_def_id, ident: i.ident, generics, kind, span: i.span }
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858 }
859
dfeec247 860 fn lower_trait_item_ref(&mut self, i: &AssocItem) -> hir::TraitItemRef {
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861 let (kind, has_default) = match &i.kind {
862 AssocItemKind::Const(_, _, default) => (hir::AssocItemKind::Const, default.is_some()),
5869c6ff 863 AssocItemKind::TyAlias(box TyAliasKind(_, _, _, default)) => {
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864 (hir::AssocItemKind::Type, default.is_some())
865 }
5869c6ff 866 AssocItemKind::Fn(box FnKind(_, sig, _, default)) => {
ba9703b0 867 (hir::AssocItemKind::Fn { has_self: sig.decl.has_self() }, default.is_some())
416331ca 868 }
ba9703b0 869 AssocItemKind::MacCall(..) => unimplemented!(),
416331ca 870 };
6a06907d 871 let id = hir::TraitItemId { def_id: self.lower_node_id(i.id).expect_owner() };
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872 let defaultness = hir::Defaultness::Default { has_value: has_default };
873 hir::TraitItemRef { id, ident: i.ident, span: i.span, defaultness, kind }
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874 }
875
dfeec247 876 /// Construct `ExprKind::Err` for the given `span`.
ba9703b0 877 crate fn expr_err(&mut self, span: Span) -> hir::Expr<'hir> {
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878 self.expr(span, hir::ExprKind::Err, AttrVec::new())
879 }
880
881 fn lower_impl_item(&mut self, i: &AssocItem) -> hir::ImplItem<'hir> {
f035d41b 882 let impl_item_def_id = self.resolver.local_def_id(i.id);
416331ca 883
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884 let (generics, kind) = match &i.kind {
885 AssocItemKind::Const(_, ty, expr) => {
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886 let ty = self.lower_ty(ty, ImplTraitContext::disallowed());
887 (
74b04a01 888 hir::Generics::empty(),
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889 hir::ImplItemKind::Const(ty, self.lower_const_body(i.span, expr.as_deref())),
890 )
891 }
5869c6ff 892 AssocItemKind::Fn(box FnKind(_, sig, generics, body)) => {
416331ca 893 self.current_item = Some(i.span);
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894 let asyncness = sig.header.asyncness;
895 let body_id =
896 self.lower_maybe_async_body(i.span, &sig.decl, asyncness, body.as_deref());
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897 let impl_trait_return_allow = !self.is_in_trait_impl;
898 let (generics, sig) = self.lower_method_sig(
74b04a01 899 generics,
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900 sig,
901 impl_item_def_id,
902 impl_trait_return_allow,
74b04a01 903 asyncness.opt_return_id(),
5869c6ff 904 i.id,
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905 );
906
ba9703b0 907 (generics, hir::ImplItemKind::Fn(sig, body_id))
416331ca 908 }
5869c6ff 909 AssocItemKind::TyAlias(box TyAliasKind(_, generics, _, ty)) => {
74b04a01 910 let generics = self.lower_generics(generics, ImplTraitContext::disallowed());
dfeec247 911 let kind = match ty {
60c5eb7d 912 None => {
dfeec247 913 let ty = self.arena.alloc(self.ty(i.span, hir::TyKind::Err));
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914 hir::ImplItemKind::TyAlias(ty)
915 }
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916 Some(ty) => {
917 let ty = self.lower_ty(
918 ty,
919 ImplTraitContext::OtherOpaqueTy {
920 capturable_lifetimes: &mut FxHashSet::default(),
6a06907d 921 origin: hir::OpaqueTyOrigin::TyAlias,
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922 },
923 );
924 hir::ImplItemKind::TyAlias(ty)
925 }
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926 };
927 (generics, kind)
dfeec247 928 }
ba9703b0 929 AssocItemKind::MacCall(..) => panic!("`TyMac` should have been expanded by now"),
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930 };
931
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932 // Since `default impl` is not yet implemented, this is always true in impls.
933 let has_value = true;
934 let (defaultness, _) = self.lower_defaultness(i.kind.defaultness(), has_value);
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935 let hir_id = self.lower_node_id(i.id);
936 self.lower_attrs(hir_id, &i.attrs);
416331ca 937 hir::ImplItem {
6a06907d 938 def_id: hir_id.expect_owner(),
416331ca 939 ident: i.ident,
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940 generics,
941 vis: self.lower_visibility(&i.vis, None),
ba9703b0 942 defaultness,
e74abb32 943 kind,
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944 span: i.span,
945 }
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946 }
947
dfeec247 948 fn lower_impl_item_ref(&mut self, i: &AssocItem) -> hir::ImplItemRef<'hir> {
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949 // Since `default impl` is not yet implemented, this is always true in impls.
950 let has_value = true;
951 let (defaultness, _) = self.lower_defaultness(i.kind.defaultness(), has_value);
416331ca 952 hir::ImplItemRef {
6a06907d 953 id: hir::ImplItemId { def_id: self.lower_node_id(i.id).expect_owner() },
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954 ident: i.ident,
955 span: i.span,
956 vis: self.lower_visibility(&i.vis, Some(i.id)),
ba9703b0 957 defaultness,
60c5eb7d 958 kind: match &i.kind {
dfeec247 959 AssocItemKind::Const(..) => hir::AssocItemKind::Const,
f035d41b 960 AssocItemKind::TyAlias(..) => hir::AssocItemKind::Type,
5869c6ff 961 AssocItemKind::Fn(box FnKind(_, sig, ..)) => {
ba9703b0 962 hir::AssocItemKind::Fn { has_self: sig.decl.has_self() }
dfeec247 963 }
ba9703b0 964 AssocItemKind::MacCall(..) => unimplemented!(),
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965 },
966 }
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967 }
968
969 /// If an `explicit_owner` is given, this method allocates the `HirId` in
970 /// the address space of that item instead of the item currently being
971 /// lowered. This can happen during `lower_impl_item_ref()` where we need to
972 /// lower a `Visibility` value although we haven't lowered the owning
973 /// `ImplItem` in question yet.
974 fn lower_visibility(
975 &mut self,
976 v: &Visibility,
977 explicit_owner: Option<NodeId>,
dfeec247 978 ) -> hir::Visibility<'hir> {
1b1a35ee 979 let node = match v.kind {
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980 VisibilityKind::Public => hir::VisibilityKind::Public,
981 VisibilityKind::Crate(sugar) => hir::VisibilityKind::Crate(sugar),
982 VisibilityKind::Restricted { ref path, id } => {
983 debug!("lower_visibility: restricted path id = {:?}", id);
984 let lowered_id = if let Some(owner) = explicit_owner {
985 self.lower_node_id_with_owner(id, owner)
986 } else {
987 self.lower_node_id(id)
988 };
989 let res = self.expect_full_res(id);
990 let res = self.lower_res(res);
991 hir::VisibilityKind::Restricted {
dfeec247 992 path: self.lower_path_extra(res, path, ParamMode::Explicit, explicit_owner),
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993 hir_id: lowered_id,
994 }
dfeec247 995 }
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996 VisibilityKind::Inherited => hir::VisibilityKind::Inherited,
997 };
998 respan(v.span, node)
999 }
1000
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1001 fn lower_defaultness(
1002 &self,
1003 d: Defaultness,
1004 has_value: bool,
1005 ) -> (hir::Defaultness, Option<Span>) {
416331ca 1006 match d {
ba9703b0 1007 Defaultness::Default(sp) => (hir::Defaultness::Default { has_value }, Some(sp)),
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1008 Defaultness::Final => {
1009 assert!(has_value);
ba9703b0 1010 (hir::Defaultness::Final, None)
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1011 }
1012 }
1013 }
1014
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1015 fn record_body(
1016 &mut self,
1017 params: &'hir [hir::Param<'hir>],
1018 value: hir::Expr<'hir>,
1019 ) -> hir::BodyId {
1020 let body = hir::Body { generator_kind: self.generator_kind, params, value };
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1021 let id = body.id();
1022 self.bodies.insert(id, body);
1023 id
1024 }
1025
ba9703b0 1026 pub(super) fn lower_body(
416331ca 1027 &mut self,
dfeec247 1028 f: impl FnOnce(&mut Self) -> (&'hir [hir::Param<'hir>], hir::Expr<'hir>),
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1029 ) -> hir::BodyId {
1030 let prev_gen_kind = self.generator_kind.take();
ba9703b0 1031 let task_context = self.task_context.take();
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1032 let (parameters, result) = f(self);
1033 let body_id = self.record_body(parameters, result);
ba9703b0 1034 self.task_context = task_context;
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1035 self.generator_kind = prev_gen_kind;
1036 body_id
1037 }
1038
dfeec247 1039 fn lower_param(&mut self, param: &Param) -> hir::Param<'hir> {
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1040 let hir_id = self.lower_node_id(param.id);
1041 self.lower_attrs(hir_id, &param.attrs);
e1599b0c 1042 hir::Param {
6a06907d 1043 hir_id,
e1599b0c 1044 pat: self.lower_pat(&param.pat),
3dfed10e 1045 ty_span: param.ty.span,
e1599b0c 1046 span: param.span,
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1047 }
1048 }
1049
1050 pub(super) fn lower_fn_body(
1051 &mut self,
1052 decl: &FnDecl,
dfeec247 1053 body: impl FnOnce(&mut Self) -> hir::Expr<'hir>,
416331ca 1054 ) -> hir::BodyId {
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1055 self.lower_body(|this| {
1056 (
1057 this.arena.alloc_from_iter(decl.inputs.iter().map(|x| this.lower_param(x))),
1058 body(this),
1059 )
1060 })
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1061 }
1062
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1063 fn lower_fn_body_block(
1064 &mut self,
1065 span: Span,
1066 decl: &FnDecl,
1067 body: Option<&Block>,
1068 ) -> hir::BodyId {
1069 self.lower_fn_body(decl, |this| this.lower_block_expr_opt(span, body))
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1070 }
1071
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1072 fn lower_block_expr_opt(&mut self, span: Span, block: Option<&Block>) -> hir::Expr<'hir> {
1073 match block {
1074 Some(block) => self.lower_block_expr(block),
1075 None => self.expr_err(span),
1076 }
1077 }
1078
1079 pub(super) fn lower_const_body(&mut self, span: Span, expr: Option<&Expr>) -> hir::BodyId {
1080 self.lower_body(|this| {
1081 (
1082 &[],
1083 match expr {
1084 Some(expr) => this.lower_expr_mut(expr),
1085 None => this.expr_err(span),
1086 },
1087 )
1088 })
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1089 }
1090
1091 fn lower_maybe_async_body(
1092 &mut self,
dfeec247 1093 span: Span,
416331ca 1094 decl: &FnDecl,
74b04a01 1095 asyncness: Async,
dfeec247 1096 body: Option<&Block>,
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1097 ) -> hir::BodyId {
1098 let closure_id = match asyncness {
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1099 Async::Yes { closure_id, .. } => closure_id,
1100 Async::No => return self.lower_fn_body_block(span, decl, body),
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1101 };
1102
1103 self.lower_body(|this| {
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1104 let mut parameters: Vec<hir::Param<'_>> = Vec::new();
1105 let mut statements: Vec<hir::Stmt<'_>> = Vec::new();
416331ca 1106
e1599b0c 1107 // Async function parameters are lowered into the closure body so that they are
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1108 // captured and so that the drop order matches the equivalent non-async functions.
1109 //
1110 // from:
1111 //
1112 // async fn foo(<pattern>: <ty>, <pattern>: <ty>, <pattern>: <ty>) {
e1599b0c 1113 // <body>
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1114 // }
1115 //
1116 // into:
1117 //
1118 // fn foo(__arg0: <ty>, __arg1: <ty>, __arg2: <ty>) {
1119 // async move {
1120 // let __arg2 = __arg2;
1121 // let <pattern> = __arg2;
1122 // let __arg1 = __arg1;
1123 // let <pattern> = __arg1;
1124 // let __arg0 = __arg0;
1125 // let <pattern> = __arg0;
e1599b0c 1126 // drop-temps { <body> } // see comments later in fn for details
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1127 // }
1128 // }
1129 //
1130 // If `<pattern>` is a simple ident, then it is lowered to a single
1131 // `let <pattern> = <pattern>;` statement as an optimization.
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1132 //
1133 // Note that the body is embedded in `drop-temps`; an
1134 // equivalent desugaring would be `return { <body>
1135 // };`. The key point is that we wish to drop all the
1136 // let-bound variables and temporaries created in the body
1137 // (and its tail expression!) before we drop the
1138 // parameters (c.f. rust-lang/rust#64512).
1139 for (index, parameter) in decl.inputs.iter().enumerate() {
1140 let parameter = this.lower_param(parameter);
1141 let span = parameter.pat.span;
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1142
1143 // Check if this is a binding pattern, if so, we can optimize and avoid adding a
e1599b0c 1144 // `let <pat> = __argN;` statement. In this case, we do not rename the parameter.
e74abb32 1145 let (ident, is_simple_parameter) = match parameter.pat.kind {
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1146 hir::PatKind::Binding(
1147 hir::BindingAnnotation::Unannotated | hir::BindingAnnotation::Mutable,
1148 _,
1149 ident,
1150 _,
1151 ) => (ident, true),
1152 // For `ref mut` or wildcard arguments, we can't reuse the binding, but
1153 // we can keep the same name for the parameter.
1154 // This lets rustdoc render it correctly in documentation.
1155 hir::PatKind::Binding(_, _, ident, _) => (ident, false),
1156 hir::PatKind::Wild => {
1157 (Ident::with_dummy_span(rustc_span::symbol::kw::Underscore), false)
dfeec247 1158 }
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1159 _ => {
1160 // Replace the ident for bindings that aren't simple.
1161 let name = format!("__arg{}", index);
1162 let ident = Ident::from_str(&name);
1163
1164 (ident, false)
dfeec247 1165 }
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1166 };
1167
dfeec247 1168 let desugared_span = this.mark_span_with_reason(DesugaringKind::Async, span, None);
416331ca 1169
e1599b0c 1170 // Construct a parameter representing `__argN: <ty>` to replace the parameter of the
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1171 // async function.
1172 //
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1173 // If this is the simple case, this parameter will end up being the same as the
1174 // original parameter, but with a different pattern id.
6a06907d 1175 let stmt_attrs = this.attrs.get(&parameter.hir_id).copied();
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1176 let (new_parameter_pat, new_parameter_id) = this.pat_ident(desugared_span, ident);
1177 let new_parameter = hir::Param {
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1178 hir_id: parameter.hir_id,
1179 pat: new_parameter_pat,
3dfed10e 1180 ty_span: parameter.ty_span,
e1599b0c 1181 span: parameter.span,
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1182 };
1183
e1599b0c 1184 if is_simple_parameter {
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1185 // If this is the simple case, then we only insert one statement that is
1186 // `let <pat> = <pat>;`. We re-use the original argument's pattern so that
1187 // `HirId`s are densely assigned.
e1599b0c 1188 let expr = this.expr_ident(desugared_span, ident, new_parameter_id);
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1189 let stmt = this.stmt_let_pat(
1190 stmt_attrs,
1191 desugared_span,
dfeec247 1192 Some(expr),
e1599b0c 1193 parameter.pat,
dfeec247 1194 hir::LocalSource::AsyncFn,
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1195 );
1196 statements.push(stmt);
1197 } else {
1198 // If this is not the simple case, then we construct two statements:
1199 //
1200 // ```
1201 // let __argN = __argN;
1202 // let <pat> = __argN;
1203 // ```
1204 //
e1599b0c 1205 // The first statement moves the parameter into the closure and thus ensures
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1206 // that the drop order is correct.
1207 //
1208 // The second statement creates the bindings that the user wrote.
1209
1210 // Construct the `let mut __argN = __argN;` statement. It must be a mut binding
1211 // because the user may have specified a `ref mut` binding in the next
1212 // statement.
1213 let (move_pat, move_id) = this.pat_ident_binding_mode(
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1214 desugared_span,
1215 ident,
1216 hir::BindingAnnotation::Mutable,
1217 );
e1599b0c 1218 let move_expr = this.expr_ident(desugared_span, ident, new_parameter_id);
416331ca 1219 let move_stmt = this.stmt_let_pat(
6a06907d 1220 None,
416331ca 1221 desugared_span,
dfeec247 1222 Some(move_expr),
416331ca 1223 move_pat,
dfeec247 1224 hir::LocalSource::AsyncFn,
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1225 );
1226
1227 // Construct the `let <pat> = __argN;` statement. We re-use the original
e1599b0c 1228 // parameter's pattern so that `HirId`s are densely assigned.
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1229 let pattern_expr = this.expr_ident(desugared_span, ident, move_id);
1230 let pattern_stmt = this.stmt_let_pat(
1231 stmt_attrs,
1232 desugared_span,
dfeec247 1233 Some(pattern_expr),
e1599b0c 1234 parameter.pat,
dfeec247 1235 hir::LocalSource::AsyncFn,
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1236 );
1237
1238 statements.push(move_stmt);
1239 statements.push(pattern_stmt);
1240 };
1241
e1599b0c 1242 parameters.push(new_parameter);
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1243 }
1244
dfeec247 1245 let body_span = body.map_or(span, |b| b.span);
416331ca 1246 let async_expr = this.make_async_expr(
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1247 CaptureBy::Value,
1248 closure_id,
1249 None,
dfeec247 1250 body_span,
e74abb32 1251 hir::AsyncGeneratorKind::Fn,
416331ca 1252 |this| {
e1599b0c 1253 // Create a block from the user's function body:
dfeec247 1254 let user_body = this.lower_block_expr_opt(body_span, body);
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1255
1256 // Transform into `drop-temps { <user-body> }`, an expression:
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1257 let desugared_span =
1258 this.mark_span_with_reason(DesugaringKind::Async, user_body.span, None);
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1259 let user_body = this.expr_drop_temps(
1260 desugared_span,
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1261 this.arena.alloc(user_body),
1262 AttrVec::new(),
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1263 );
1264
1265 // As noted above, create the final block like
1266 //
1267 // ```
1268 // {
1269 // let $param_pattern = $raw_param;
1270 // ...
1271 // drop-temps { <user-body> }
1272 // }
1273 // ```
1274 let body = this.block_all(
1275 desugared_span,
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1276 this.arena.alloc_from_iter(statements),
1277 Some(user_body),
e1599b0c 1278 );
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1279
1280 this.expr_block(body, AttrVec::new())
1281 },
1282 );
1283
1284 (
1285 this.arena.alloc_from_iter(parameters),
1286 this.expr(body_span, async_expr, AttrVec::new()),
1287 )
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1288 })
1289 }
1290
1291 fn lower_method_sig(
1292 &mut self,
1293 generics: &Generics,
60c5eb7d 1294 sig: &FnSig,
ba9703b0 1295 fn_def_id: LocalDefId,
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1296 impl_trait_return_allow: bool,
1297 is_async: Option<NodeId>,
5869c6ff 1298 id: NodeId,
dfeec247 1299 ) -> (hir::Generics<'hir>, hir::FnSig<'hir>) {
5869c6ff 1300 let header = self.lower_fn_header(sig.header, sig.span, id);
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1301 let (generics, decl) = self.add_in_band_defs(
1302 generics,
1303 fn_def_id,
1304 AnonymousLifetimeMode::PassThrough,
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1305 |this, idty| {
1306 this.lower_fn_decl(
1307 &sig.decl,
ba9703b0 1308 Some((fn_def_id.to_def_id(), idty)),
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1309 impl_trait_return_allow,
1310 is_async,
1311 )
1312 },
416331ca 1313 );
3dfed10e 1314 (generics, hir::FnSig { header, decl, span: sig.span })
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1315 }
1316
5869c6ff 1317 fn lower_fn_header(&mut self, h: FnHeader, span: Span, id: NodeId) -> hir::FnHeader {
416331ca 1318 hir::FnHeader {
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1319 unsafety: self.lower_unsafety(h.unsafety),
1320 asyncness: self.lower_asyncness(h.asyncness),
1321 constness: self.lower_constness(h.constness),
5869c6ff 1322 abi: self.lower_extern(h.ext, span, id),
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1323 }
1324 }
1325
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1326 pub(super) fn lower_abi(&mut self, abi: StrLit) -> abi::Abi {
1327 abi::lookup(&abi.symbol_unescaped.as_str()).unwrap_or_else(|| {
1328 self.error_on_invalid_abi(abi);
1329 abi::Abi::Rust
1330 })
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1331 }
1332
5869c6ff 1333 pub(super) fn lower_extern(&mut self, ext: Extern, span: Span, id: NodeId) -> abi::Abi {
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1334 match ext {
1335 Extern::None => abi::Abi::Rust,
5869c6ff 1336 Extern::Implicit => {
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1337 self.maybe_lint_missing_abi(span, id, abi::Abi::C { unwind: false });
1338 abi::Abi::C { unwind: false }
5869c6ff 1339 }
60c5eb7d 1340 Extern::Explicit(abi) => self.lower_abi(abi),
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1341 }
1342 }
1343
60c5eb7d 1344 fn error_on_invalid_abi(&self, abi: StrLit) {
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1345 struct_span_err!(self.sess, abi.span, E0703, "invalid ABI: found `{}`", abi.symbol)
1346 .span_label(abi.span, "invalid ABI")
1347 .help(&format!("valid ABIs: {}", abi::all_names().join(", ")))
1348 .emit();
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1349 }
1350
74b04a01 1351 fn lower_asyncness(&mut self, a: Async) -> hir::IsAsync {
416331ca 1352 match a {
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1353 Async::Yes { .. } => hir::IsAsync::Async,
1354 Async::No => hir::IsAsync::NotAsync,
1355 }
1356 }
1357
1358 fn lower_constness(&mut self, c: Const) -> hir::Constness {
1359 match c {
1360 Const::Yes(_) => hir::Constness::Const,
1361 Const::No => hir::Constness::NotConst,
1362 }
1363 }
1364
1365 pub(super) fn lower_unsafety(&mut self, u: Unsafe) -> hir::Unsafety {
1366 match u {
1367 Unsafe::Yes(_) => hir::Unsafety::Unsafe,
1368 Unsafe::No => hir::Unsafety::Normal,
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1369 }
1370 }
1371
dfeec247 1372 pub(super) fn lower_generics_mut(
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1373 &mut self,
1374 generics: &Generics,
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1375 itctx: ImplTraitContext<'_, 'hir>,
1376 ) -> GenericsCtor<'hir> {
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1377 // Collect `?Trait` bounds in where clause and move them to parameter definitions.
1378 // FIXME: this could probably be done with less rightward drift. It also looks like two
1379 // control paths where `report_error` is called are the only paths that advance to after the
1380 // match statement, so the error reporting could probably just be moved there.
1381 let mut add_bounds: NodeMap<Vec<_>> = Default::default();
1382 for pred in &generics.where_clause.predicates {
1383 if let WherePredicate::BoundPredicate(ref bound_pred) = *pred {
1384 'next_bound: for bound in &bound_pred.bounds {
1385 if let GenericBound::Trait(_, TraitBoundModifier::Maybe) = *bound {
1386 let report_error = |this: &mut Self| {
1387 this.diagnostic().span_err(
1388 bound_pred.bounded_ty.span,
1389 "`?Trait` bounds are only permitted at the \
1390 point where a type parameter is declared",
1391 );
1392 };
1393 // Check if the where clause type is a plain type parameter.
e74abb32 1394 match bound_pred.bounded_ty.kind {
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1395 TyKind::Path(None, ref path)
1396 if path.segments.len() == 1
1397 && bound_pred.bound_generic_params.is_empty() =>
1398 {
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1399 if let Some(Res::Def(DefKind::TyParam, def_id)) = self
1400 .resolver
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1401 .get_partial_res(bound_pred.bounded_ty.id)
1402 .map(|d| d.base_res())
1403 {
f9f354fc 1404 if let Some(def_id) = def_id.as_local() {
416331ca 1405 for param in &generics.params {
ba9703b0 1406 if let GenericParamKind::Type { .. } = param.kind {
f035d41b 1407 if def_id == self.resolver.local_def_id(param.id) {
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1408 add_bounds
1409 .entry(param.id)
1410 .or_default()
1411 .push(bound.clone());
1412 continue 'next_bound;
416331ca 1413 }
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1414 }
1415 }
1416 }
1417 }
1418 report_error(self)
1419 }
1420 _ => report_error(self),
1421 }
1422 }
1423 }
1424 }
1425 }
1426
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1427 GenericsCtor {
1428 params: self.lower_generic_params_mut(&generics.params, &add_bounds, itctx).collect(),
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1429 where_clause: self.lower_where_clause(&generics.where_clause),
1430 span: generics.span,
1431 }
1432 }
1433
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1434 pub(super) fn lower_generics(
1435 &mut self,
1436 generics: &Generics,
1437 itctx: ImplTraitContext<'_, 'hir>,
1438 ) -> hir::Generics<'hir> {
1439 let generics_ctor = self.lower_generics_mut(generics, itctx);
1440 generics_ctor.into_generics(self.arena)
1441 }
1442
1443 fn lower_where_clause(&mut self, wc: &WhereClause) -> hir::WhereClause<'hir> {
1444 self.with_anonymous_lifetime_mode(AnonymousLifetimeMode::ReportError, |this| {
1445 hir::WhereClause {
1446 predicates: this.arena.alloc_from_iter(
1447 wc.predicates.iter().map(|predicate| this.lower_where_predicate(predicate)),
1448 ),
1449 span: wc.span,
1450 }
1451 })
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1452 }
1453
dfeec247 1454 fn lower_where_predicate(&mut self, pred: &WherePredicate) -> hir::WherePredicate<'hir> {
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1455 match *pred {
1456 WherePredicate::BoundPredicate(WhereBoundPredicate {
1457 ref bound_generic_params,
1458 ref bounded_ty,
1459 ref bounds,
1460 span,
1461 }) => {
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1462 self.with_in_scope_lifetime_defs(&bound_generic_params, |this| {
1463 hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
1464 bound_generic_params: this.lower_generic_params(
1465 bound_generic_params,
1466 &NodeMap::default(),
1467 ImplTraitContext::disallowed(),
1468 ),
1469 bounded_ty: this.lower_ty(bounded_ty, ImplTraitContext::disallowed()),
1470 bounds: this.arena.alloc_from_iter(bounds.iter().filter_map(|bound| {
1471 match *bound {
1472 // Ignore `?Trait` bounds.
1473 // They were copied into type parameters already.
1474 GenericBound::Trait(_, TraitBoundModifier::Maybe) => None,
1475 _ => Some(
1476 this.lower_param_bound(bound, ImplTraitContext::disallowed()),
1477 ),
1478 }
1479 })),
1480 span,
1481 })
1482 })
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1483 }
1484 WherePredicate::RegionPredicate(WhereRegionPredicate {
1485 ref lifetime,
1486 ref bounds,
1487 span,
1488 }) => hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate {
1489 span,
1490 lifetime: self.lower_lifetime(lifetime),
1491 bounds: self.lower_param_bounds(bounds, ImplTraitContext::disallowed()),
1492 }),
dfeec247 1493 WherePredicate::EqPredicate(WhereEqPredicate { id, ref lhs_ty, ref rhs_ty, span }) => {
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1494 hir::WherePredicate::EqPredicate(hir::WhereEqPredicate {
1495 hir_id: self.lower_node_id(id),
1496 lhs_ty: self.lower_ty(lhs_ty, ImplTraitContext::disallowed()),
1497 rhs_ty: self.lower_ty(rhs_ty, ImplTraitContext::disallowed()),
1498 span,
1499 })
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1500 }
1501 }
1502 }
1503}
1504
1505/// Helper struct for delayed construction of Generics.
1506pub(super) struct GenericsCtor<'hir> {
1507 pub(super) params: SmallVec<[hir::GenericParam<'hir>; 4]>,
1508 where_clause: hir::WhereClause<'hir>,
1509 span: Span,
1510}
1511
1512impl<'hir> GenericsCtor<'hir> {
1513 pub(super) fn into_generics(self, arena: &'hir Arena<'hir>) -> hir::Generics<'hir> {
1514 hir::Generics {
1515 params: arena.alloc_from_iter(self.params),
1516 where_clause: self.where_clause,
1517 span: self.span,
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1518 }
1519 }
1520}