crates/hir_def/src/item_tree/lower.rs

   1 //! AST -> `ItemTree` lowering code.
   2
   3 use std::{collections::hash_map::Entry, mem, sync::Arc};
   4
   5 use hir_expand::{ast_id_map::AstIdMap, hygiene::Hygiene, name::known, HirFileId};
   6 use smallvec::SmallVec;
   7 use syntax::{
   8     ast::{self, ModuleItemOwner},
   9     SyntaxNode, WalkEvent,
  10 };
  11
  12 use crate::{
  13     generics::{GenericParams, TypeParamData, TypeParamProvenance},
  14     type_ref::LifetimeRef,
  15 };
  16
  17 use super::*;
  18
  19 fn id<N: ItemTreeNode>(index: Idx<N>) -> FileItemTreeId<N> {
  20     FileItemTreeId { index, _p: PhantomData }
  21 }
  22
  23 struct ModItems(SmallVec<[ModItem; 1]>);
  24
  25 impl<T> From<T> for ModItems
  26 where
  27     T: Into<ModItem>,
  28 {
  29     fn from(t: T) -> Self {
  30         ModItems(SmallVec::from_buf([t.into(); 1]))
  31     }
  32 }
  33
  34 pub(super) struct Ctx {
  35     tree: ItemTree,
  36     hygiene: Hygiene,
  37     file: HirFileId,
  38     source_ast_id_map: Arc<AstIdMap>,
  39     body_ctx: crate::body::LowerCtx,
  40     forced_visibility: Option<RawVisibilityId>,
  41 }
  42
  43 impl Ctx {
  44     pub(super) fn new(db: &dyn DefDatabase, hygiene: Hygiene, file: HirFileId) -> Self {
  45         Self {
  46             tree: ItemTree::empty(),
  47             hygiene,
  48             file,
  49             source_ast_id_map: db.ast_id_map(file),
  50             body_ctx: crate::body::LowerCtx::new(db, file),
  51             forced_visibility: None,
  52         }
  53     }
  54
  55     pub(super) fn lower_module_items(mut self, item_owner: &dyn ModuleItemOwner) -> ItemTree {
  56         self.tree.top_level = item_owner
  57             .items()
  58             .flat_map(|item| self.lower_mod_item(&item, false))
  59             .flat_map(|items| items.0)
  60             .collect();
  61         self.tree
  62     }
  63
  64     pub(super) fn lower_inner_items(mut self, within: &SyntaxNode) -> ItemTree {
  65         self.collect_inner_items(within);
  66         self.tree
  67     }
  68
  69     fn data(&mut self) -> &mut ItemTreeData {
  70         self.tree.data_mut()
  71     }
  72
  73     fn lower_mod_item(&mut self, item: &ast::Item, inner: bool) -> Option<ModItems> {
  74         // Collect inner items for 1-to-1-lowered items.
  75         match item {
  76             ast::Item::Struct(_)
  77             | ast::Item::Union(_)
  78             | ast::Item::Enum(_)
  79             | ast::Item::Fn(_)
  80             | ast::Item::TypeAlias(_)
  81             | ast::Item::Const(_)
  82             | ast::Item::Static(_) => {
  83                 // Skip this if we're already collecting inner items. We'll descend into all nodes
  84                 // already.
  85                 if !inner {
  86                     self.collect_inner_items(item.syntax());
  87                 }
  88             }
  89
  90             // These are handled in their respective `lower_X` method (since we can't just blindly
  91             // walk them).
  92             ast::Item::Trait(_) | ast::Item::Impl(_) | ast::Item::ExternBlock(_) => {}
  93
  94             // These don't have inner items.
  95             ast::Item::Module(_)
  96             | ast::Item::ExternCrate(_)
  97             | ast::Item::Use(_)
  98             | ast::Item::MacroCall(_)
  99             | ast::Item::MacroRules(_)
 100             | ast::Item::MacroDef(_) => {}
 101         };
 102
 103         let attrs = RawAttrs::new(item, &self.hygiene);
 104         let items = match item {
 105             ast::Item::Struct(ast) => self.lower_struct(ast).map(Into::into),
 106             ast::Item::Union(ast) => self.lower_union(ast).map(Into::into),
 107             ast::Item::Enum(ast) => self.lower_enum(ast).map(Into::into),
 108             ast::Item::Fn(ast) => self.lower_function(ast).map(Into::into),
 109             ast::Item::TypeAlias(ast) => self.lower_type_alias(ast).map(Into::into),
 110             ast::Item::Static(ast) => self.lower_static(ast).map(Into::into),
 111             ast::Item::Const(ast) => Some(self.lower_const(ast).into()),
 112             ast::Item::Module(ast) => self.lower_module(ast).map(Into::into),
 113             ast::Item::Trait(ast) => self.lower_trait(ast).map(Into::into),
 114             ast::Item::Impl(ast) => self.lower_impl(ast).map(Into::into),
 115             ast::Item::Use(ast) => Some(ModItems(
 116                 self.lower_use(ast).into_iter().map(Into::into).collect::<SmallVec<_>>(),
 117             )),
 118             ast::Item::ExternCrate(ast) => self.lower_extern_crate(ast).map(Into::into),
 119             ast::Item::MacroCall(ast) => self.lower_macro_call(ast).map(Into::into),
 120             ast::Item::MacroRules(ast) => self.lower_macro_rules(ast).map(Into::into),
 121             ast::Item::MacroDef(ast) => self.lower_macro_def(ast).map(Into::into),
 122             ast::Item::ExternBlock(ast) => {
 123                 Some(ModItems(self.lower_extern_block(ast).into_iter().collect::<SmallVec<_>>()))
 124             }
 125         };
 126
 127         if !attrs.is_empty() {
 128             for item in items.iter().flat_map(|items| &items.0) {
 129                 self.add_attrs((*item).into(), attrs.clone());
 130             }
 131         }
 132
 133         items
 134     }
 135
 136     fn add_attrs(&mut self, item: AttrOwner, attrs: RawAttrs) {
 137         match self.tree.attrs.entry(item) {
 138             Entry::Occupied(mut entry) => {
 139                 *entry.get_mut() = entry.get().merge(attrs);
 140             }
 141             Entry::Vacant(entry) => {
 142                 entry.insert(attrs);
 143             }
 144         }
 145     }
 146
 147     fn collect_inner_items(&mut self, container: &SyntaxNode) {
 148         let forced_vis = self.forced_visibility.take();
 149
 150         let mut block_stack = Vec::new();
 151         for event in container.preorder().skip(1) {
 152             match event {
 153                 WalkEvent::Enter(node) => {
 154                     match_ast! {
 155                         match node {
 156                             ast::BlockExpr(block) => {
 157                                 block_stack.push(self.source_ast_id_map.ast_id(&block));
 158                             },
 159                             ast::Item(item) => {
 160                                 let mod_items = self.lower_mod_item(&item, true);
 161                                 let current_block = block_stack.last();
 162                                 if let (Some(mod_items), Some(block)) = (mod_items, current_block) {
 163                                     if !mod_items.0.is_empty() {
 164                                         self.data().inner_items.entry(*block).or_default().extend(mod_items.0.iter().copied());
 165                                     }
 166                                 }
 167                             },
 168                             _ => {}
 169                         }
 170                     }
 171                 }
 172                 WalkEvent::Leave(node) => {
 173                     if ast::BlockExpr::cast(node).is_some() {
 174                         block_stack.pop();
 175                     }
 176                 }
 177             }
 178         }
 179
 180         self.forced_visibility = forced_vis;
 181     }
 182
 183     fn lower_assoc_item(&mut self, item: &ast::AssocItem) -> Option<AssocItem> {
 184         match item {
 185             ast::AssocItem::Fn(ast) => self.lower_function(ast).map(Into::into),
 186             ast::AssocItem::TypeAlias(ast) => self.lower_type_alias(ast).map(Into::into),
 187             ast::AssocItem::Const(ast) => Some(self.lower_const(ast).into()),
 188             ast::AssocItem::MacroCall(ast) => self.lower_macro_call(ast).map(Into::into),
 189         }
 190     }
 191
 192     fn lower_struct(&mut self, strukt: &ast::Struct) -> Option<FileItemTreeId<Struct>> {
 193         let visibility = self.lower_visibility(strukt);
 194         let name = strukt.name()?.as_name();
 195         let generic_params = self.lower_generic_params(GenericsOwner::Struct, strukt);
 196         let fields = self.lower_fields(&strukt.kind());
 197         let ast_id = self.source_ast_id_map.ast_id(strukt);
 198         let kind = match strukt.kind() {
 199             ast::StructKind::Record(_) => StructDefKind::Record,
 200             ast::StructKind::Tuple(_) => StructDefKind::Tuple,
 201             ast::StructKind::Unit => StructDefKind::Unit,
 202         };
 203         let res = Struct { name, visibility, generic_params, fields, ast_id, kind };
 204         Some(id(self.data().structs.alloc(res)))
 205     }
 206
 207     fn lower_fields(&mut self, strukt_kind: &ast::StructKind) -> Fields {
 208         match strukt_kind {
 209             ast::StructKind::Record(it) => {
 210                 let range = self.lower_record_fields(it);
 211                 Fields::Record(range)
 212             }
 213             ast::StructKind::Tuple(it) => {
 214                 let range = self.lower_tuple_fields(it);
 215                 Fields::Tuple(range)
 216             }
 217             ast::StructKind::Unit => Fields::Unit,
 218         }
 219     }
 220
 221     fn lower_record_fields(&mut self, fields: &ast::RecordFieldList) -> IdRange<Field> {
 222         let start = self.next_field_idx();
 223         for field in fields.fields() {
 224             if let Some(data) = self.lower_record_field(&field) {
 225                 let idx = self.data().fields.alloc(data);
 226                 self.add_attrs(idx.into(), RawAttrs::new(&field, &self.hygiene));
 227             }
 228         }
 229         let end = self.next_field_idx();
 230         IdRange::new(start..end)
 231     }
 232
 233     fn lower_record_field(&mut self, field: &ast::RecordField) -> Option<Field> {
 234         let name = field.name()?.as_name();
 235         let visibility = self.lower_visibility(field);
 236         let type_ref = self.lower_type_ref_opt(field.ty());
 237         let res = Field { name, type_ref, visibility };
 238         Some(res)
 239     }
 240
 241     fn lower_tuple_fields(&mut self, fields: &ast::TupleFieldList) -> IdRange<Field> {
 242         let start = self.next_field_idx();
 243         for (i, field) in fields.fields().enumerate() {
 244             let data = self.lower_tuple_field(i, &field);
 245             let idx = self.data().fields.alloc(data);
 246             self.add_attrs(idx.into(), RawAttrs::new(&field, &self.hygiene));
 247         }
 248         let end = self.next_field_idx();
 249         IdRange::new(start..end)
 250     }
 251
 252     fn lower_tuple_field(&mut self, idx: usize, field: &ast::TupleField) -> Field {
 253         let name = Name::new_tuple_field(idx);
 254         let visibility = self.lower_visibility(field);
 255         let type_ref = self.lower_type_ref_opt(field.ty());
 256         let res = Field { name, type_ref, visibility };
 257         res
 258     }
 259
 260     fn lower_union(&mut self, union: &ast::Union) -> Option<FileItemTreeId<Union>> {
 261         let visibility = self.lower_visibility(union);
 262         let name = union.name()?.as_name();
 263         let generic_params = self.lower_generic_params(GenericsOwner::Union, union);
 264         let fields = match union.record_field_list() {
 265             Some(record_field_list) => self.lower_fields(&StructKind::Record(record_field_list)),
 266             None => Fields::Record(IdRange::new(self.next_field_idx()..self.next_field_idx())),
 267         };
 268         let ast_id = self.source_ast_id_map.ast_id(union);
 269         let res = Union { name, visibility, generic_params, fields, ast_id };
 270         Some(id(self.data().unions.alloc(res)))
 271     }
 272
 273     fn lower_enum(&mut self, enum_: &ast::Enum) -> Option<FileItemTreeId<Enum>> {
 274         let visibility = self.lower_visibility(enum_);
 275         let name = enum_.name()?.as_name();
 276         let generic_params = self.lower_generic_params(GenericsOwner::Enum, enum_);
 277         let variants = match &enum_.variant_list() {
 278             Some(variant_list) => self.lower_variants(variant_list),
 279             None => IdRange::new(self.next_variant_idx()..self.next_variant_idx()),
 280         };
 281         let ast_id = self.source_ast_id_map.ast_id(enum_);
 282         let res = Enum { name, visibility, generic_params, variants, ast_id };
 283         Some(id(self.data().enums.alloc(res)))
 284     }
 285
 286     fn lower_variants(&mut self, variants: &ast::VariantList) -> IdRange<Variant> {
 287         let start = self.next_variant_idx();
 288         for variant in variants.variants() {
 289             if let Some(data) = self.lower_variant(&variant) {
 290                 let idx = self.data().variants.alloc(data);
 291                 self.add_attrs(idx.into(), RawAttrs::new(&variant, &self.hygiene));
 292             }
 293         }
 294         let end = self.next_variant_idx();
 295         IdRange::new(start..end)
 296     }
 297
 298     fn lower_variant(&mut self, variant: &ast::Variant) -> Option<Variant> {
 299         let name = variant.name()?.as_name();
 300         let fields = self.lower_fields(&variant.kind());
 301         let res = Variant { name, fields };
 302         Some(res)
 303     }
 304
 305     fn lower_function(&mut self, func: &ast::Fn) -> Option<FileItemTreeId<Function>> {
 306         let visibility = self.lower_visibility(func);
 307         let name = func.name()?.as_name();
 308
 309         let mut params = Vec::new();
 310         let mut has_self_param = false;
 311         if let Some(param_list) = func.param_list() {
 312             if let Some(self_param) = param_list.self_param() {
 313                 let self_type = match self_param.ty() {
 314                     Some(type_ref) => TypeRef::from_ast(&self.body_ctx, type_ref),
 315                     None => {
 316                         let self_type = TypeRef::Path(name![Self].into());
 317                         match self_param.kind() {
 318                             ast::SelfParamKind::Owned => self_type,
 319                             ast::SelfParamKind::Ref => TypeRef::Reference(
 320                                 Box::new(self_type),
 321                                 self_param.lifetime().as_ref().map(LifetimeRef::new),
 322                                 Mutability::Shared,
 323                             ),
 324                             ast::SelfParamKind::MutRef => TypeRef::Reference(
 325                                 Box::new(self_type),
 326                                 self_param.lifetime().as_ref().map(LifetimeRef::new),
 327                                 Mutability::Mut,
 328                             ),
 329                         }
 330                     }
 331                 };
 332                 params.push(self_type);
 333                 has_self_param = true;
 334             }
 335             for param in param_list.params() {
 336                 let type_ref = TypeRef::from_ast_opt(&self.body_ctx, param.ty());
 337                 params.push(type_ref);
 338             }
 339         }
 340
 341         let mut is_varargs = false;
 342         if let Some(params) = func.param_list() {
 343             if let Some(last) = params.params().last() {
 344                 is_varargs = last.dotdotdot_token().is_some();
 345             }
 346         }
 347
 348         let ret_type = match func.ret_type().and_then(|rt| rt.ty()) {
 349             Some(type_ref) => TypeRef::from_ast(&self.body_ctx, type_ref),
 350             _ => TypeRef::unit(),
 351         };
 352
 353         let ret_type = if func.async_token().is_some() {
 354             let future_impl = desugar_future_path(ret_type);
 355             let ty_bound = TypeBound::Path(future_impl);
 356             TypeRef::ImplTrait(vec![ty_bound])
 357         } else {
 358             ret_type
 359         };
 360
 361         let has_body = func.body().is_some();
 362
 363         let ast_id = self.source_ast_id_map.ast_id(func);
 364         let mut res = Function {
 365             name,
 366             visibility,
 367             generic_params: GenericParamsId::EMPTY,
 368             has_self_param,
 369             has_body,
 370             is_unsafe: func.unsafe_token().is_some(),
 371             is_extern: false,
 372             params: params.into_boxed_slice(),
 373             is_varargs,
 374             ret_type,
 375             ast_id,
 376         };
 377         res.generic_params = self.lower_generic_params(GenericsOwner::Function(&res), func);
 378
 379         Some(id(self.data().functions.alloc(res)))
 380     }
 381
 382     fn lower_type_alias(
 383         &mut self,
 384         type_alias: &ast::TypeAlias,
 385     ) -> Option<FileItemTreeId<TypeAlias>> {
 386         let name = type_alias.name()?.as_name();
 387         let type_ref = type_alias.ty().map(|it| self.lower_type_ref(&it));
 388         let visibility = self.lower_visibility(type_alias);
 389         let bounds = self.lower_type_bounds(type_alias);
 390         let generic_params = self.lower_generic_params(GenericsOwner::TypeAlias, type_alias);
 391         let ast_id = self.source_ast_id_map.ast_id(type_alias);
 392         let res = TypeAlias {
 393             name,
 394             visibility,
 395             bounds: bounds.into_boxed_slice(),
 396             generic_params,
 397             type_ref,
 398             ast_id,
 399             is_extern: false,
 400         };
 401         Some(id(self.data().type_aliases.alloc(res)))
 402     }
 403
 404     fn lower_static(&mut self, static_: &ast::Static) -> Option<FileItemTreeId<Static>> {
 405         let name = static_.name()?.as_name();
 406         let type_ref = self.lower_type_ref_opt(static_.ty());
 407         let visibility = self.lower_visibility(static_);
 408         let mutable = static_.mut_token().is_some();
 409         let ast_id = self.source_ast_id_map.ast_id(static_);
 410         let res = Static { name, visibility, mutable, type_ref, ast_id, is_extern: false };
 411         Some(id(self.data().statics.alloc(res)))
 412     }
 413
 414     fn lower_const(&mut self, konst: &ast::Const) -> FileItemTreeId<Const> {
 415         let name = konst.name().map(|it| it.as_name());
 416         let type_ref = self.lower_type_ref_opt(konst.ty());
 417         let visibility = self.lower_visibility(konst);
 418         let ast_id = self.source_ast_id_map.ast_id(konst);
 419         let res = Const { name, visibility, type_ref, ast_id };
 420         id(self.data().consts.alloc(res))
 421     }
 422
 423     fn lower_module(&mut self, module: &ast::Module) -> Option<FileItemTreeId<Mod>> {
 424         let name = module.name()?.as_name();
 425         let visibility = self.lower_visibility(module);
 426         let kind = if module.semicolon_token().is_some() {
 427             ModKind::Outline {}
 428         } else {
 429             ModKind::Inline {
 430                 items: module
 431                     .item_list()
 432                     .map(|list| {
 433                         list.items()
 434                             .flat_map(|item| self.lower_mod_item(&item, false))
 435                             .flat_map(|items| items.0)
 436                             .collect()
 437                     })
 438                     .unwrap_or_else(|| {
 439                         mark::hit!(name_res_works_for_broken_modules);
 440                         Box::new([]) as Box<[_]>
 441                     }),
 442             }
 443         };
 444         let ast_id = self.source_ast_id_map.ast_id(module);
 445         let res = Mod { name, visibility, kind, ast_id };
 446         Some(id(self.data().mods.alloc(res)))
 447     }
 448
 449     fn lower_trait(&mut self, trait_def: &ast::Trait) -> Option<FileItemTreeId<Trait>> {
 450         let name = trait_def.name()?.as_name();
 451         let visibility = self.lower_visibility(trait_def);
 452         let generic_params =
 453             self.lower_generic_params_and_inner_items(GenericsOwner::Trait(trait_def), trait_def);
 454         let auto = trait_def.auto_token().is_some();
 455         let items = trait_def.assoc_item_list().map(|list| {
 456             self.with_inherited_visibility(visibility, |this| {
 457                 list.assoc_items()
 458                     .filter_map(|item| {
 459                         let attrs = RawAttrs::new(&item, &this.hygiene);
 460                         this.collect_inner_items(item.syntax());
 461                         this.lower_assoc_item(&item).map(|item| {
 462                             this.add_attrs(ModItem::from(item).into(), attrs);
 463                             item
 464                         })
 465                     })
 466                     .collect()
 467             })
 468         });
 469         let ast_id = self.source_ast_id_map.ast_id(trait_def);
 470         let res = Trait {
 471             name,
 472             visibility,
 473             generic_params,
 474             auto,
 475             items: items.unwrap_or_default(),
 476             ast_id,
 477         };
 478         Some(id(self.data().traits.alloc(res)))
 479     }
 480
 481     fn lower_impl(&mut self, impl_def: &ast::Impl) -> Option<FileItemTreeId<Impl>> {
 482         let generic_params =
 483             self.lower_generic_params_and_inner_items(GenericsOwner::Impl, impl_def);
 484         let target_trait = impl_def.trait_().map(|tr| self.lower_type_ref(&tr));
 485         let target_type = self.lower_type_ref(&impl_def.self_ty()?);
 486         let is_negative = impl_def.excl_token().is_some();
 487
 488         // We cannot use `assoc_items()` here as that does not include macro calls.
 489         let items = impl_def
 490             .assoc_item_list()
 491             .into_iter()
 492             .flat_map(|it| it.assoc_items())
 493             .filter_map(|item| {
 494                 self.collect_inner_items(item.syntax());
 495                 let assoc = self.lower_assoc_item(&item)?;
 496                 let attrs = RawAttrs::new(&item, &self.hygiene);
 497                 self.add_attrs(ModItem::from(assoc).into(), attrs);
 498                 Some(assoc)
 499             })
 500             .collect();
 501         let ast_id = self.source_ast_id_map.ast_id(impl_def);
 502         let res = Impl { generic_params, target_trait, target_type, is_negative, items, ast_id };
 503         Some(id(self.data().impls.alloc(res)))
 504     }
 505
 506     fn lower_use(&mut self, use_item: &ast::Use) -> Vec<FileItemTreeId<Import>> {
 507         let visibility = self.lower_visibility(use_item);
 508         let ast_id = self.source_ast_id_map.ast_id(use_item);
 509
 510         // Every use item can expand to many `Import`s.
 511         let mut imports = Vec::new();
 512         let tree = self.tree.data_mut();
 513         ModPath::expand_use_item(
 514             InFile::new(self.file, use_item.clone()),
 515             &self.hygiene,
 516             |path, _use_tree, is_glob, alias| {
 517                 imports.push(id(tree.imports.alloc(Import {
 518                     path,
 519                     alias,
 520                     visibility,
 521                     is_glob,
 522                     ast_id,
 523                     index: imports.len(),
 524                 })));
 525             },
 526         );
 527
 528         imports
 529     }
 530
 531     fn lower_extern_crate(
 532         &mut self,
 533         extern_crate: &ast::ExternCrate,
 534     ) -> Option<FileItemTreeId<ExternCrate>> {
 535         let name = extern_crate.name_ref()?.as_name();
 536         let alias = extern_crate.rename().map(|a| {
 537             a.name().map(|it| it.as_name()).map_or(ImportAlias::Underscore, ImportAlias::Alias)
 538         });
 539         let visibility = self.lower_visibility(extern_crate);
 540         let ast_id = self.source_ast_id_map.ast_id(extern_crate);
 541
 542         let res = ExternCrate { name, alias, visibility, ast_id };
 543         Some(id(self.data().extern_crates.alloc(res)))
 544     }
 545
 546     fn lower_macro_call(&mut self, m: &ast::MacroCall) -> Option<FileItemTreeId<MacroCall>> {
 547         let path = ModPath::from_src(m.path()?, &self.hygiene)?;
 548         let ast_id = self.source_ast_id_map.ast_id(m);
 549         let res = MacroCall { path, ast_id };
 550         Some(id(self.data().macro_calls.alloc(res)))
 551     }
 552
 553     fn lower_macro_rules(&mut self, m: &ast::MacroRules) -> Option<FileItemTreeId<MacroRules>> {
 554         let name = m.name().map(|it| it.as_name())?;
 555         let ast_id = self.source_ast_id_map.ast_id(m);
 556
 557         let res = MacroRules { name, ast_id };
 558         Some(id(self.data().macro_rules.alloc(res)))
 559     }
 560
 561     fn lower_macro_def(&mut self, m: &ast::MacroDef) -> Option<FileItemTreeId<MacroDef>> {
 562         let name = m.name().map(|it| it.as_name())?;
 563
 564         let ast_id = self.source_ast_id_map.ast_id(m);
 565         let visibility = self.lower_visibility(m);
 566
 567         let res = MacroDef { name, ast_id, visibility };
 568         Some(id(self.data().macro_defs.alloc(res)))
 569     }
 570
 571     fn lower_extern_block(&mut self, block: &ast::ExternBlock) -> Vec<ModItem> {
 572         block.extern_item_list().map_or(Vec::new(), |list| {
 573             list.extern_items()
 574                 .filter_map(|item| {
 575                     self.collect_inner_items(item.syntax());
 576                     let attrs = RawAttrs::new(&item, &self.hygiene);
 577                     let id: ModItem = match item {
 578                         ast::ExternItem::Fn(ast) => {
 579                             let func_id = self.lower_function(&ast)?;
 580                             let func = &mut self.data().functions[func_id.index];
 581                             func.is_unsafe = is_intrinsic_fn_unsafe(&func.name);
 582                             func.is_extern = true;
 583                             func_id.into()
 584                         }
 585                         ast::ExternItem::Static(ast) => {
 586                             let statik = self.lower_static(&ast)?;
 587                             self.data().statics[statik.index].is_extern = true;
 588                             statik.into()
 589                         }
 590                         ast::ExternItem::TypeAlias(ty) => {
 591                             let foreign_ty = self.lower_type_alias(&ty)?;
 592                             self.data().type_aliases[foreign_ty.index].is_extern = true;
 593                             foreign_ty.into()
 594                         }
 595                         ast::ExternItem::MacroCall(_) => return None,
 596                     };
 597                     self.add_attrs(id.into(), attrs);
 598                     Some(id)
 599                 })
 600                 .collect()
 601         })
 602     }
 603
 604     /// Lowers generics defined on `node` and collects inner items defined within.
 605     fn lower_generic_params_and_inner_items(
 606         &mut self,
 607         owner: GenericsOwner<'_>,
 608         node: &impl ast::GenericParamsOwner,
 609     ) -> GenericParamsId {
 610         // Generics are part of item headers and may contain inner items we need to collect.
 611         if let Some(params) = node.generic_param_list() {
 612             self.collect_inner_items(params.syntax());
 613         }
 614         if let Some(clause) = node.where_clause() {
 615             self.collect_inner_items(clause.syntax());
 616         }
 617
 618         self.lower_generic_params(owner, node)
 619     }
 620
 621     fn lower_generic_params(
 622         &mut self,
 623         owner: GenericsOwner<'_>,
 624         node: &impl ast::GenericParamsOwner,
 625     ) -> GenericParamsId {
 626         let mut sm = &mut Default::default();
 627         let mut generics = GenericParams::default();
 628         match owner {
 629             GenericsOwner::Function(func) => {
 630                 generics.fill(&self.body_ctx, sm, node);
 631                 // lower `impl Trait` in arguments
 632                 for param in &*func.params {
 633                     generics.fill_implicit_impl_trait_args(param);
 634                 }
 635             }
 636             GenericsOwner::Struct
 637             | GenericsOwner::Enum
 638             | GenericsOwner::Union
 639             | GenericsOwner::TypeAlias => {
 640                 generics.fill(&self.body_ctx, sm, node);
 641             }
 642             GenericsOwner::Trait(trait_def) => {
 643                 // traits get the Self type as an implicit first type parameter
 644                 let self_param_id = generics.types.alloc(TypeParamData {
 645                     name: Some(name![Self]),
 646                     default: None,
 647                     provenance: TypeParamProvenance::TraitSelf,
 648                 });
 649                 sm.type_params.insert(self_param_id, Either::Left(trait_def.clone()));
 650                 // add super traits as bounds on Self
 651                 // i.e., trait Foo: Bar is equivalent to trait Foo where Self: Bar
 652                 let self_param = TypeRef::Path(name![Self].into());
 653                 generics.fill_bounds(&self.body_ctx, trait_def, Either::Left(self_param));
 654                 generics.fill(&self.body_ctx, &mut sm, node);
 655             }
 656             GenericsOwner::Impl => {
 657                 // Note that we don't add `Self` here: in `impl`s, `Self` is not a
 658                 // type-parameter, but rather is a type-alias for impl's target
 659                 // type, so this is handled by the resolver.
 660                 generics.fill(&self.body_ctx, &mut sm, node);
 661             }
 662         }
 663
 664         self.data().generics.alloc(generics)
 665     }
 666
 667     fn lower_type_bounds(&mut self, node: &impl ast::TypeBoundsOwner) -> Vec<TypeBound> {
 668         match node.type_bound_list() {
 669             Some(bound_list) => {
 670                 bound_list.bounds().map(|it| TypeBound::from_ast(&self.body_ctx, it)).collect()
 671             }
 672             None => Vec::new(),
 673         }
 674     }
 675
 676     fn lower_visibility(&mut self, item: &impl ast::VisibilityOwner) -> RawVisibilityId {
 677         let vis = match self.forced_visibility {
 678             Some(vis) => return vis,
 679             None => RawVisibility::from_ast_with_hygiene(item.visibility(), &self.hygiene),
 680         };
 681
 682         self.data().vis.alloc(vis)
 683     }
 684
 685     fn lower_type_ref(&self, type_ref: &ast::Type) -> TypeRef {
 686         TypeRef::from_ast(&self.body_ctx, type_ref.clone())
 687     }
 688     fn lower_type_ref_opt(&self, type_ref: Option<ast::Type>) -> TypeRef {
 689         type_ref.map(|ty| self.lower_type_ref(&ty)).unwrap_or(TypeRef::Error)
 690     }
 691
 692     /// Forces the visibility `vis` to be used for all items lowered during execution of `f`.
 693     fn with_inherited_visibility<R>(
 694         &mut self,
 695         vis: RawVisibilityId,
 696         f: impl FnOnce(&mut Self) -> R,
 697     ) -> R {
 698         let old = mem::replace(&mut self.forced_visibility, Some(vis));
 699         let res = f(self);
 700         self.forced_visibility = old;
 701         res
 702     }
 703
 704     fn next_field_idx(&self) -> Idx<Field> {
 705         Idx::from_raw(RawIdx::from(
 706             self.tree.data.as_ref().map_or(0, |data| data.fields.len() as u32),
 707         ))
 708     }
 709     fn next_variant_idx(&self) -> Idx<Variant> {
 710         Idx::from_raw(RawIdx::from(
 711             self.tree.data.as_ref().map_or(0, |data| data.variants.len() as u32),
 712         ))
 713     }
 714 }
 715
 716 fn desugar_future_path(orig: TypeRef) -> Path {
 717     let path = path![core::future::Future];
 718     let mut generic_args: Vec<_> = std::iter::repeat(None).take(path.segments.len() - 1).collect();
 719     let mut last = GenericArgs::empty();
 720     let binding =
 721         AssociatedTypeBinding { name: name![Output], type_ref: Some(orig), bounds: Vec::new() };
 722     last.bindings.push(binding);
 723     generic_args.push(Some(Arc::new(last)));
 724
 725     Path::from_known_path(path, generic_args)
 726 }
 727
 728 enum GenericsOwner<'a> {
 729     /// We need access to the partially-lowered `Function` for lowering `impl Trait` in argument
 730     /// position.
 731     Function(&'a Function),
 732     Struct,
 733     Enum,
 734     Union,
 735     /// The `TraitDef` is needed to fill the source map for the implicit `Self` parameter.
 736     Trait(&'a ast::Trait),
 737     TypeAlias,
 738     Impl,
 739 }
 740
 741 /// Returns `true` if the given intrinsic is unsafe to call, or false otherwise.
 742 fn is_intrinsic_fn_unsafe(name: &Name) -> bool {
 743     // Should be kept in sync with https://github.com/rust-lang/rust/blob/c6e4db620a7d2f569f11dcab627430921ea8aacf/compiler/rustc_typeck/src/check/intrinsic.rs#L68
 744     ![
 745         known::abort,
 746         known::min_align_of,
 747         known::needs_drop,
 748         known::caller_location,
 749         known::size_of_val,
 750         known::min_align_of_val,
 751         known::add_with_overflow,
 752         known::sub_with_overflow,
 753         known::mul_with_overflow,
 754         known::wrapping_add,
 755         known::wrapping_sub,
 756         known::wrapping_mul,
 757         known::saturating_add,
 758         known::saturating_sub,
 759         known::rotate_left,
 760         known::rotate_right,
 761         known::ctpop,
 762         known::ctlz,
 763         known::cttz,
 764         known::bswap,
 765         known::bitreverse,
 766         known::discriminant_value,
 767         known::type_id,
 768         known::likely,
 769         known::unlikely,
 770         known::ptr_guaranteed_eq,
 771         known::ptr_guaranteed_ne,
 772         known::minnumf32,
 773         known::minnumf64,
 774         known::maxnumf32,
 775         known::rustc_peek,
 776         known::maxnumf64,
 777         known::type_name,
 778         known::variant_count,
 779     ]
 780     .contains(&name)
 781 }