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 syntax::ast::{self, HasModuleItem};
   7
   8 use crate::{
   9     generics::{GenericParams, TypeParamData, TypeParamProvenance},
  10     type_ref::{LifetimeRef, TraitBoundModifier, TraitRef},
  11 };
  12
  13 use super::*;
  14
  15 fn id<N: ItemTreeNode>(index: Idx<N>) -> FileItemTreeId<N> {
  16     FileItemTreeId { index, _p: PhantomData }
  17 }
  18
  19 pub(super) struct Ctx<'a> {
  20     db: &'a dyn DefDatabase,
  21     tree: ItemTree,
  22     source_ast_id_map: Arc<AstIdMap>,
  23     body_ctx: crate::body::LowerCtx<'a>,
  24     forced_visibility: Option<RawVisibilityId>,
  25 }
  26
  27 impl<'a> Ctx<'a> {
  28     pub(super) fn new(db: &'a dyn DefDatabase, file: HirFileId) -> Self {
  29         Self {
  30             db,
  31             tree: ItemTree::default(),
  32             source_ast_id_map: db.ast_id_map(file),
  33             body_ctx: crate::body::LowerCtx::new(db, file),
  34             forced_visibility: None,
  35         }
  36     }
  37
  38     pub(super) fn hygiene(&self) -> &Hygiene {
  39         self.body_ctx.hygiene()
  40     }
  41
  42     pub(super) fn lower_module_items(mut self, item_owner: &dyn HasModuleItem) -> ItemTree {
  43         self.tree.top_level =
  44             item_owner.items().flat_map(|item| self.lower_mod_item(&item)).collect();
  45         self.tree
  46     }
  47
  48     pub(super) fn lower_macro_stmts(mut self, stmts: ast::MacroStmts) -> ItemTree {
  49         self.tree.top_level = stmts
  50             .statements()
  51             .filter_map(|stmt| match stmt {
  52                 ast::Stmt::Item(item) => Some(item),
  53                 // Macro calls can be both items and expressions. The syntax library always treats
  54                 // them as expressions here, so we undo that.
  55                 ast::Stmt::ExprStmt(es) => match es.expr()? {
  56                     ast::Expr::MacroCall(call) => {
  57                         cov_mark::hit!(macro_call_in_macro_stmts_is_added_to_item_tree);
  58                         Some(call.into())
  59                     }
  60                     _ => None,
  61                 },
  62                 _ => None,
  63             })
  64             .flat_map(|item| self.lower_mod_item(&item))
  65             .collect();
  66
  67         self.tree
  68     }
  69
  70     pub(super) fn lower_block(mut self, block: &ast::BlockExpr) -> ItemTree {
  71         self.tree.top_level = block
  72             .statements()
  73             .filter_map(|stmt| match stmt {
  74                 ast::Stmt::Item(item) => self.lower_mod_item(&item),
  75                 // Macro calls can be both items and expressions. The syntax library always treats
  76                 // them as expressions here, so we undo that.
  77                 ast::Stmt::ExprStmt(es) => match es.expr()? {
  78                     ast::Expr::MacroCall(call) => self.lower_mod_item(&call.into()),
  79                     _ => None,
  80                 },
  81                 _ => None,
  82             })
  83             .collect();
  84
  85         self.tree
  86     }
  87
  88     fn data(&mut self) -> &mut ItemTreeData {
  89         self.tree.data_mut()
  90     }
  91
  92     fn lower_mod_item(&mut self, item: &ast::Item) -> Option<ModItem> {
  93         let attrs = RawAttrs::new(self.db, item, self.hygiene());
  94         let item: ModItem = match item {
  95             ast::Item::Struct(ast) => self.lower_struct(ast)?.into(),
  96             ast::Item::Union(ast) => self.lower_union(ast)?.into(),
  97             ast::Item::Enum(ast) => self.lower_enum(ast)?.into(),
  98             ast::Item::Fn(ast) => self.lower_function(ast)?.into(),
  99             ast::Item::TypeAlias(ast) => self.lower_type_alias(ast)?.into(),
 100             ast::Item::Static(ast) => self.lower_static(ast)?.into(),
 101             ast::Item::Const(ast) => self.lower_const(ast).into(),
 102             ast::Item::Module(ast) => self.lower_module(ast)?.into(),
 103             ast::Item::Trait(ast) => self.lower_trait(ast)?.into(),
 104             ast::Item::Impl(ast) => self.lower_impl(ast)?.into(),
 105             ast::Item::Use(ast) => self.lower_use(ast)?.into(),
 106             ast::Item::ExternCrate(ast) => self.lower_extern_crate(ast)?.into(),
 107             ast::Item::MacroCall(ast) => self.lower_macro_call(ast)?.into(),
 108             ast::Item::MacroRules(ast) => self.lower_macro_rules(ast)?.into(),
 109             ast::Item::MacroDef(ast) => self.lower_macro_def(ast)?.into(),
 110             ast::Item::ExternBlock(ast) => self.lower_extern_block(ast).into(),
 111         };
 112
 113         self.add_attrs(item.into(), attrs);
 114
 115         Some(item)
 116     }
 117
 118     fn add_attrs(&mut self, item: AttrOwner, attrs: RawAttrs) {
 119         match self.tree.attrs.entry(item) {
 120             Entry::Occupied(mut entry) => {
 121                 *entry.get_mut() = entry.get().merge(attrs);
 122             }
 123             Entry::Vacant(entry) => {
 124                 entry.insert(attrs);
 125             }
 126         }
 127     }
 128
 129     fn lower_assoc_item(&mut self, item: &ast::AssocItem) -> Option<AssocItem> {
 130         match item {
 131             ast::AssocItem::Fn(ast) => self.lower_function(ast).map(Into::into),
 132             ast::AssocItem::TypeAlias(ast) => self.lower_type_alias(ast).map(Into::into),
 133             ast::AssocItem::Const(ast) => Some(self.lower_const(ast).into()),
 134             ast::AssocItem::MacroCall(ast) => self.lower_macro_call(ast).map(Into::into),
 135         }
 136     }
 137
 138     fn lower_struct(&mut self, strukt: &ast::Struct) -> Option<FileItemTreeId<Struct>> {
 139         let visibility = self.lower_visibility(strukt);
 140         let name = strukt.name()?.as_name();
 141         let generic_params = self.lower_generic_params(GenericsOwner::Struct, strukt);
 142         let fields = self.lower_fields(&strukt.kind());
 143         let ast_id = self.source_ast_id_map.ast_id(strukt);
 144         let res = Struct { name, visibility, generic_params, fields, ast_id };
 145         Some(id(self.data().structs.alloc(res)))
 146     }
 147
 148     fn lower_fields(&mut self, strukt_kind: &ast::StructKind) -> Fields {
 149         match strukt_kind {
 150             ast::StructKind::Record(it) => {
 151                 let range = self.lower_record_fields(it);
 152                 Fields::Record(range)
 153             }
 154             ast::StructKind::Tuple(it) => {
 155                 let range = self.lower_tuple_fields(it);
 156                 Fields::Tuple(range)
 157             }
 158             ast::StructKind::Unit => Fields::Unit,
 159         }
 160     }
 161
 162     fn lower_record_fields(&mut self, fields: &ast::RecordFieldList) -> IdxRange<Field> {
 163         let start = self.next_field_idx();
 164         for field in fields.fields() {
 165             if let Some(data) = self.lower_record_field(&field) {
 166                 let idx = self.data().fields.alloc(data);
 167                 self.add_attrs(idx.into(), RawAttrs::new(self.db, &field, self.hygiene()));
 168             }
 169         }
 170         let end = self.next_field_idx();
 171         IdxRange::new(start..end)
 172     }
 173
 174     fn lower_record_field(&mut self, field: &ast::RecordField) -> Option<Field> {
 175         let name = field.name()?.as_name();
 176         let visibility = self.lower_visibility(field);
 177         let type_ref = self.lower_type_ref_opt(field.ty());
 178         let res = Field { name, type_ref, visibility };
 179         Some(res)
 180     }
 181
 182     fn lower_tuple_fields(&mut self, fields: &ast::TupleFieldList) -> IdxRange<Field> {
 183         let start = self.next_field_idx();
 184         for (i, field) in fields.fields().enumerate() {
 185             let data = self.lower_tuple_field(i, &field);
 186             let idx = self.data().fields.alloc(data);
 187             self.add_attrs(idx.into(), RawAttrs::new(self.db, &field, self.hygiene()));
 188         }
 189         let end = self.next_field_idx();
 190         IdxRange::new(start..end)
 191     }
 192
 193     fn lower_tuple_field(&mut self, idx: usize, field: &ast::TupleField) -> Field {
 194         let name = Name::new_tuple_field(idx);
 195         let visibility = self.lower_visibility(field);
 196         let type_ref = self.lower_type_ref_opt(field.ty());
 197         Field { name, type_ref, visibility }
 198     }
 199
 200     fn lower_union(&mut self, union: &ast::Union) -> Option<FileItemTreeId<Union>> {
 201         let visibility = self.lower_visibility(union);
 202         let name = union.name()?.as_name();
 203         let generic_params = self.lower_generic_params(GenericsOwner::Union, union);
 204         let fields = match union.record_field_list() {
 205             Some(record_field_list) => self.lower_fields(&StructKind::Record(record_field_list)),
 206             None => Fields::Record(IdxRange::new(self.next_field_idx()..self.next_field_idx())),
 207         };
 208         let ast_id = self.source_ast_id_map.ast_id(union);
 209         let res = Union { name, visibility, generic_params, fields, ast_id };
 210         Some(id(self.data().unions.alloc(res)))
 211     }
 212
 213     fn lower_enum(&mut self, enum_: &ast::Enum) -> Option<FileItemTreeId<Enum>> {
 214         let visibility = self.lower_visibility(enum_);
 215         let name = enum_.name()?.as_name();
 216         let generic_params = self.lower_generic_params(GenericsOwner::Enum, enum_);
 217         let variants =
 218             self.with_inherited_visibility(visibility, |this| match &enum_.variant_list() {
 219                 Some(variant_list) => this.lower_variants(variant_list),
 220                 None => IdxRange::new(this.next_variant_idx()..this.next_variant_idx()),
 221             });
 222         let ast_id = self.source_ast_id_map.ast_id(enum_);
 223         let res = Enum { name, visibility, generic_params, variants, ast_id };
 224         Some(id(self.data().enums.alloc(res)))
 225     }
 226
 227     fn lower_variants(&mut self, variants: &ast::VariantList) -> IdxRange<Variant> {
 228         let start = self.next_variant_idx();
 229         for variant in variants.variants() {
 230             if let Some(data) = self.lower_variant(&variant) {
 231                 let idx = self.data().variants.alloc(data);
 232                 self.add_attrs(idx.into(), RawAttrs::new(self.db, &variant, self.hygiene()));
 233             }
 234         }
 235         let end = self.next_variant_idx();
 236         IdxRange::new(start..end)
 237     }
 238
 239     fn lower_variant(&mut self, variant: &ast::Variant) -> Option<Variant> {
 240         let name = variant.name()?.as_name();
 241         let fields = self.lower_fields(&variant.kind());
 242         let res = Variant { name, fields };
 243         Some(res)
 244     }
 245
 246     fn lower_function(&mut self, func: &ast::Fn) -> Option<FileItemTreeId<Function>> {
 247         let visibility = self.lower_visibility(func);
 248         let name = func.name()?.as_name();
 249
 250         let mut has_self_param = false;
 251         let start_param = self.next_param_idx();
 252         if let Some(param_list) = func.param_list() {
 253             if let Some(self_param) = param_list.self_param() {
 254                 let self_type = match self_param.ty() {
 255                     Some(type_ref) => TypeRef::from_ast(&self.body_ctx, type_ref),
 256                     None => {
 257                         let self_type = TypeRef::Path(name![Self].into());
 258                         match self_param.kind() {
 259                             ast::SelfParamKind::Owned => self_type,
 260                             ast::SelfParamKind::Ref => TypeRef::Reference(
 261                                 Box::new(self_type),
 262                                 self_param.lifetime().as_ref().map(LifetimeRef::new),
 263                                 Mutability::Shared,
 264                             ),
 265                             ast::SelfParamKind::MutRef => TypeRef::Reference(
 266                                 Box::new(self_type),
 267                                 self_param.lifetime().as_ref().map(LifetimeRef::new),
 268                                 Mutability::Mut,
 269                             ),
 270                         }
 271                     }
 272                 };
 273                 let ty = Interned::new(self_type);
 274                 let idx = self.data().params.alloc(Param::Normal(None, ty));
 275                 self.add_attrs(idx.into(), RawAttrs::new(self.db, &self_param, self.hygiene()));
 276                 has_self_param = true;
 277             }
 278             for param in param_list.params() {
 279                 let idx = match param.dotdotdot_token() {
 280                     Some(_) => self.data().params.alloc(Param::Varargs),
 281                     None => {
 282                         let type_ref = TypeRef::from_ast_opt(&self.body_ctx, param.ty());
 283                         let ty = Interned::new(type_ref);
 284                         let mut pat = param.pat();
 285                         // FIXME: This really shouldn't be here, in fact FunctionData/ItemTree's function shouldn't know about
 286                         // pattern names at all
 287                         let name = loop {
 288                             match pat {
 289                                 Some(ast::Pat::RefPat(ref_pat)) => pat = ref_pat.pat(),
 290                                 Some(ast::Pat::IdentPat(ident)) => {
 291                                     break ident.name().map(|it| it.as_name())
 292                                 }
 293                                 _ => break None,
 294                             }
 295                         };
 296                         self.data().params.alloc(Param::Normal(name, ty))
 297                     }
 298                 };
 299                 self.add_attrs(idx.into(), RawAttrs::new(self.db, &param, self.hygiene()));
 300             }
 301         }
 302         let end_param = self.next_param_idx();
 303         let params = IdxRange::new(start_param..end_param);
 304
 305         let ret_type = match func.ret_type().and_then(|rt| rt.ty()) {
 306             Some(type_ref) => TypeRef::from_ast(&self.body_ctx, type_ref),
 307             _ => TypeRef::unit(),
 308         };
 309
 310         let (ret_type, async_ret_type) = if func.async_token().is_some() {
 311             let async_ret_type = ret_type.clone();
 312             let future_impl = desugar_future_path(ret_type);
 313             let ty_bound = Interned::new(TypeBound::Path(future_impl, TraitBoundModifier::None));
 314             (TypeRef::ImplTrait(vec![ty_bound]), Some(async_ret_type))
 315         } else {
 316             (ret_type, None)
 317         };
 318
 319         let abi = func.abi().map(lower_abi);
 320
 321         let ast_id = self.source_ast_id_map.ast_id(func);
 322
 323         let mut flags = FnFlags::default();
 324         if func.body().is_some() {
 325             flags.bits |= FnFlags::HAS_BODY;
 326         }
 327         if has_self_param {
 328             flags.bits |= FnFlags::HAS_SELF_PARAM;
 329         }
 330         if func.default_token().is_some() {
 331             flags.bits |= FnFlags::IS_DEFAULT;
 332         }
 333         if func.const_token().is_some() {
 334             flags.bits |= FnFlags::IS_CONST;
 335         }
 336         if func.async_token().is_some() {
 337             flags.bits |= FnFlags::IS_ASYNC;
 338         }
 339         if func.unsafe_token().is_some() {
 340             flags.bits |= FnFlags::IS_UNSAFE;
 341         }
 342
 343         let mut res = Function {
 344             name,
 345             visibility,
 346             explicit_generic_params: Interned::new(GenericParams::default()),
 347             abi,
 348             params,
 349             ret_type: Interned::new(ret_type),
 350             async_ret_type: async_ret_type.map(Interned::new),
 351             ast_id,
 352             flags,
 353         };
 354         res.explicit_generic_params =
 355             self.lower_generic_params(GenericsOwner::Function(&res), func);
 356
 357         Some(id(self.data().functions.alloc(res)))
 358     }
 359
 360     fn lower_type_alias(
 361         &mut self,
 362         type_alias: &ast::TypeAlias,
 363     ) -> Option<FileItemTreeId<TypeAlias>> {
 364         let name = type_alias.name()?.as_name();
 365         let type_ref = type_alias.ty().map(|it| self.lower_type_ref(&it));
 366         let visibility = self.lower_visibility(type_alias);
 367         let bounds = self.lower_type_bounds(type_alias);
 368         let generic_params = self.lower_generic_params(GenericsOwner::TypeAlias, type_alias);
 369         let ast_id = self.source_ast_id_map.ast_id(type_alias);
 370         let res = TypeAlias {
 371             name,
 372             visibility,
 373             bounds: bounds.into_boxed_slice(),
 374             generic_params,
 375             type_ref,
 376             ast_id,
 377         };
 378         Some(id(self.data().type_aliases.alloc(res)))
 379     }
 380
 381     fn lower_static(&mut self, static_: &ast::Static) -> Option<FileItemTreeId<Static>> {
 382         let name = static_.name()?.as_name();
 383         let type_ref = self.lower_type_ref_opt(static_.ty());
 384         let visibility = self.lower_visibility(static_);
 385         let mutable = static_.mut_token().is_some();
 386         let ast_id = self.source_ast_id_map.ast_id(static_);
 387         let res = Static { name, visibility, mutable, type_ref, ast_id };
 388         Some(id(self.data().statics.alloc(res)))
 389     }
 390
 391     fn lower_const(&mut self, konst: &ast::Const) -> FileItemTreeId<Const> {
 392         let name = konst.name().map(|it| it.as_name());
 393         let type_ref = self.lower_type_ref_opt(konst.ty());
 394         let visibility = self.lower_visibility(konst);
 395         let ast_id = self.source_ast_id_map.ast_id(konst);
 396         let res = Const { name, visibility, type_ref, ast_id };
 397         id(self.data().consts.alloc(res))
 398     }
 399
 400     fn lower_module(&mut self, module: &ast::Module) -> Option<FileItemTreeId<Mod>> {
 401         let name = module.name()?.as_name();
 402         let visibility = self.lower_visibility(module);
 403         let kind = if module.semicolon_token().is_some() {
 404             ModKind::Outline {}
 405         } else {
 406             ModKind::Inline {
 407                 items: module
 408                     .item_list()
 409                     .map(|list| list.items().flat_map(|item| self.lower_mod_item(&item)).collect())
 410                     .unwrap_or_else(|| {
 411                         cov_mark::hit!(name_res_works_for_broken_modules);
 412                         Box::new([]) as Box<[_]>
 413                     }),
 414             }
 415         };
 416         let ast_id = self.source_ast_id_map.ast_id(module);
 417         let res = Mod { name, visibility, kind, ast_id };
 418         Some(id(self.data().mods.alloc(res)))
 419     }
 420
 421     fn lower_trait(&mut self, trait_def: &ast::Trait) -> Option<FileItemTreeId<Trait>> {
 422         let name = trait_def.name()?.as_name();
 423         let visibility = self.lower_visibility(trait_def);
 424         let generic_params = self.lower_generic_params(GenericsOwner::Trait(trait_def), trait_def);
 425         let is_auto = trait_def.auto_token().is_some();
 426         let is_unsafe = trait_def.unsafe_token().is_some();
 427         let items = trait_def.assoc_item_list().map(|list| {
 428             let db = self.db;
 429             self.with_inherited_visibility(visibility, |this| {
 430                 list.assoc_items()
 431                     .filter_map(|item| {
 432                         let attrs = RawAttrs::new(db, &item, this.hygiene());
 433                         this.lower_assoc_item(&item).map(|item| {
 434                             this.add_attrs(ModItem::from(item).into(), attrs);
 435                             item
 436                         })
 437                     })
 438                     .collect()
 439             })
 440         });
 441         let ast_id = self.source_ast_id_map.ast_id(trait_def);
 442         let res = Trait {
 443             name,
 444             visibility,
 445             generic_params,
 446             is_auto,
 447             is_unsafe,
 448             items: items.unwrap_or_default(),
 449             ast_id,
 450         };
 451         Some(id(self.data().traits.alloc(res)))
 452     }
 453
 454     fn lower_impl(&mut self, impl_def: &ast::Impl) -> Option<FileItemTreeId<Impl>> {
 455         let generic_params = self.lower_generic_params(GenericsOwner::Impl, impl_def);
 456         // FIXME: If trait lowering fails, due to a non PathType for example, we treat this impl
 457         // as if it was an non-trait impl. Ideally we want to create a unique missing ref that only
 458         // equals itself.
 459         let target_trait = impl_def.trait_().and_then(|tr| self.lower_trait_ref(&tr));
 460         let self_ty = self.lower_type_ref(&impl_def.self_ty()?);
 461         let is_negative = impl_def.excl_token().is_some();
 462
 463         // We cannot use `assoc_items()` here as that does not include macro calls.
 464         let items = impl_def
 465             .assoc_item_list()
 466             .into_iter()
 467             .flat_map(|it| it.assoc_items())
 468             .filter_map(|item| {
 469                 let assoc = self.lower_assoc_item(&item)?;
 470                 let attrs = RawAttrs::new(self.db, &item, self.hygiene());
 471                 self.add_attrs(ModItem::from(assoc).into(), attrs);
 472                 Some(assoc)
 473             })
 474             .collect();
 475         let ast_id = self.source_ast_id_map.ast_id(impl_def);
 476         let res = Impl { generic_params, target_trait, self_ty, is_negative, items, ast_id };
 477         Some(id(self.data().impls.alloc(res)))
 478     }
 479
 480     fn lower_use(&mut self, use_item: &ast::Use) -> Option<FileItemTreeId<Import>> {
 481         let visibility = self.lower_visibility(use_item);
 482         let ast_id = self.source_ast_id_map.ast_id(use_item);
 483         let (use_tree, _) = lower_use_tree(self.db, self.hygiene(), use_item.use_tree()?)?;
 484
 485         let res = Import { visibility, ast_id, use_tree };
 486         Some(id(self.data().imports.alloc(res)))
 487     }
 488
 489     fn lower_extern_crate(
 490         &mut self,
 491         extern_crate: &ast::ExternCrate,
 492     ) -> Option<FileItemTreeId<ExternCrate>> {
 493         let name = extern_crate.name_ref()?.as_name();
 494         let alias = extern_crate.rename().map(|a| {
 495             a.name().map(|it| it.as_name()).map_or(ImportAlias::Underscore, ImportAlias::Alias)
 496         });
 497         let visibility = self.lower_visibility(extern_crate);
 498         let ast_id = self.source_ast_id_map.ast_id(extern_crate);
 499
 500         let res = ExternCrate { name, alias, visibility, ast_id };
 501         Some(id(self.data().extern_crates.alloc(res)))
 502     }
 503
 504     fn lower_macro_call(&mut self, m: &ast::MacroCall) -> Option<FileItemTreeId<MacroCall>> {
 505         let path = Interned::new(ModPath::from_src(self.db.upcast(), m.path()?, self.hygiene())?);
 506         let ast_id = self.source_ast_id_map.ast_id(m);
 507         let expand_to = hir_expand::ExpandTo::from_call_site(m);
 508         let res = MacroCall { path, ast_id, expand_to };
 509         Some(id(self.data().macro_calls.alloc(res)))
 510     }
 511
 512     fn lower_macro_rules(&mut self, m: &ast::MacroRules) -> Option<FileItemTreeId<MacroRules>> {
 513         let name = m.name().map(|it| it.as_name())?;
 514         let ast_id = self.source_ast_id_map.ast_id(m);
 515
 516         let res = MacroRules { name, ast_id };
 517         Some(id(self.data().macro_rules.alloc(res)))
 518     }
 519
 520     fn lower_macro_def(&mut self, m: &ast::MacroDef) -> Option<FileItemTreeId<MacroDef>> {
 521         let name = m.name().map(|it| it.as_name())?;
 522
 523         let ast_id = self.source_ast_id_map.ast_id(m);
 524         let visibility = self.lower_visibility(m);
 525
 526         let res = MacroDef { name, ast_id, visibility };
 527         Some(id(self.data().macro_defs.alloc(res)))
 528     }
 529
 530     fn lower_extern_block(&mut self, block: &ast::ExternBlock) -> FileItemTreeId<ExternBlock> {
 531         let ast_id = self.source_ast_id_map.ast_id(block);
 532         let abi = block.abi().map(lower_abi);
 533         let children: Box<[_]> = block.extern_item_list().map_or(Box::new([]), |list| {
 534             list.extern_items()
 535                 .filter_map(|item| {
 536                     // Note: All items in an `extern` block need to be lowered as if they're outside of one
 537                     // (in other words, the knowledge that they're in an extern block must not be used).
 538                     // This is because an extern block can contain macros whose ItemTree's top-level items
 539                     // should be considered to be in an extern block too.
 540                     let attrs = RawAttrs::new(self.db, &item, self.hygiene());
 541                     let id: ModItem = match item {
 542                         ast::ExternItem::Fn(ast) => {
 543                             let func_id = self.lower_function(&ast)?;
 544                             let func = &mut self.data().functions[func_id.index];
 545                             if is_intrinsic_fn_unsafe(&func.name) {
 546                                 // FIXME: this breaks in macros
 547                                 func.flags.bits |= FnFlags::IS_UNSAFE;
 548                             }
 549                             func_id.into()
 550                         }
 551                         ast::ExternItem::Static(ast) => self.lower_static(&ast)?.into(),
 552                         ast::ExternItem::TypeAlias(ty) => self.lower_type_alias(&ty)?.into(),
 553                         ast::ExternItem::MacroCall(call) => {
 554                             // FIXME: we need some way of tracking that the macro call is in an
 555                             // extern block
 556                             self.lower_macro_call(&call)?.into()
 557                         }
 558                     };
 559                     self.add_attrs(id.into(), attrs);
 560                     Some(id)
 561                 })
 562                 .collect()
 563         });
 564
 565         let res = ExternBlock { abi, ast_id, children };
 566         id(self.data().extern_blocks.alloc(res))
 567     }
 568
 569     fn lower_generic_params(
 570         &mut self,
 571         owner: GenericsOwner<'_>,
 572         node: &dyn ast::HasGenericParams,
 573     ) -> Interned<GenericParams> {
 574         let mut generics = GenericParams::default();
 575         match owner {
 576             GenericsOwner::Function(_)
 577             | GenericsOwner::Struct
 578             | GenericsOwner::Enum
 579             | GenericsOwner::Union
 580             | GenericsOwner::TypeAlias => {
 581                 generics.fill(&self.body_ctx, node);
 582             }
 583             GenericsOwner::Trait(trait_def) => {
 584                 // traits get the Self type as an implicit first type parameter
 585                 generics.types.alloc(TypeParamData {
 586                     name: Some(name![Self]),
 587                     default: None,
 588                     provenance: TypeParamProvenance::TraitSelf,
 589                 });
 590                 // add super traits as bounds on Self
 591                 // i.e., trait Foo: Bar is equivalent to trait Foo where Self: Bar
 592                 let self_param = TypeRef::Path(name![Self].into());
 593                 generics.fill_bounds(&self.body_ctx, trait_def, Either::Left(self_param));
 594                 generics.fill(&self.body_ctx, node);
 595             }
 596             GenericsOwner::Impl => {
 597                 // Note that we don't add `Self` here: in `impl`s, `Self` is not a
 598                 // type-parameter, but rather is a type-alias for impl's target
 599                 // type, so this is handled by the resolver.
 600                 generics.fill(&self.body_ctx, node);
 601             }
 602         }
 603
 604         generics.shrink_to_fit();
 605         Interned::new(generics)
 606     }
 607
 608     fn lower_type_bounds(&mut self, node: &dyn ast::HasTypeBounds) -> Vec<Interned<TypeBound>> {
 609         match node.type_bound_list() {
 610             Some(bound_list) => bound_list
 611                 .bounds()
 612                 .map(|it| Interned::new(TypeBound::from_ast(&self.body_ctx, it)))
 613                 .collect(),
 614             None => Vec::new(),
 615         }
 616     }
 617
 618     fn lower_visibility(&mut self, item: &dyn ast::HasVisibility) -> RawVisibilityId {
 619         let vis = match self.forced_visibility {
 620             Some(vis) => return vis,
 621             None => {
 622                 RawVisibility::from_ast_with_hygiene(self.db, item.visibility(), self.hygiene())
 623             }
 624         };
 625
 626         self.data().vis.alloc(vis)
 627     }
 628
 629     fn lower_trait_ref(&mut self, trait_ref: &ast::Type) -> Option<Interned<TraitRef>> {
 630         let trait_ref = TraitRef::from_ast(&self.body_ctx, trait_ref.clone())?;
 631         Some(Interned::new(trait_ref))
 632     }
 633
 634     fn lower_type_ref(&mut self, type_ref: &ast::Type) -> Interned<TypeRef> {
 635         let tyref = TypeRef::from_ast(&self.body_ctx, type_ref.clone());
 636         Interned::new(tyref)
 637     }
 638
 639     fn lower_type_ref_opt(&mut self, type_ref: Option<ast::Type>) -> Interned<TypeRef> {
 640         match type_ref.map(|ty| self.lower_type_ref(&ty)) {
 641             Some(it) => it,
 642             None => Interned::new(TypeRef::Error),
 643         }
 644     }
 645
 646     /// Forces the visibility `vis` to be used for all items lowered during execution of `f`.
 647     fn with_inherited_visibility<R>(
 648         &mut self,
 649         vis: RawVisibilityId,
 650         f: impl FnOnce(&mut Self) -> R,
 651     ) -> R {
 652         let old = mem::replace(&mut self.forced_visibility, Some(vis));
 653         let res = f(self);
 654         self.forced_visibility = old;
 655         res
 656     }
 657
 658     fn next_field_idx(&self) -> Idx<Field> {
 659         Idx::from_raw(RawIdx::from(
 660             self.tree.data.as_ref().map_or(0, |data| data.fields.len() as u32),
 661         ))
 662     }
 663     fn next_variant_idx(&self) -> Idx<Variant> {
 664         Idx::from_raw(RawIdx::from(
 665             self.tree.data.as_ref().map_or(0, |data| data.variants.len() as u32),
 666         ))
 667     }
 668     fn next_param_idx(&self) -> Idx<Param> {
 669         Idx::from_raw(RawIdx::from(
 670             self.tree.data.as_ref().map_or(0, |data| data.params.len() as u32),
 671         ))
 672     }
 673 }
 674
 675 fn desugar_future_path(orig: TypeRef) -> Path {
 676     let path = path![core::future::Future];
 677     let mut generic_args: Vec<_> =
 678         std::iter::repeat(None).take(path.segments().len() - 1).collect();
 679     let mut last = GenericArgs::empty();
 680     let binding =
 681         AssociatedTypeBinding { name: name![Output], type_ref: Some(orig), bounds: Vec::new() };
 682     last.bindings.push(binding);
 683     generic_args.push(Some(Interned::new(last)));
 684
 685     Path::from_known_path(path, generic_args)
 686 }
 687
 688 enum GenericsOwner<'a> {
 689     /// We need access to the partially-lowered `Function` for lowering `impl Trait` in argument
 690     /// position.
 691     Function(&'a Function),
 692     Struct,
 693     Enum,
 694     Union,
 695     /// The `TraitDef` is needed to fill the source map for the implicit `Self` parameter.
 696     Trait(&'a ast::Trait),
 697     TypeAlias,
 698     Impl,
 699 }
 700
 701 /// Returns `true` if the given intrinsic is unsafe to call, or false otherwise.
 702 fn is_intrinsic_fn_unsafe(name: &Name) -> bool {
 703     // Should be kept in sync with https://github.com/rust-lang/rust/blob/532d2b14c05f9bc20b2d27cbb5f4550d28343a36/compiler/rustc_typeck/src/check/intrinsic.rs#L72-L106
 704     ![
 705         known::add_with_overflow,
 706         known::bitreverse,
 707         known::black_box,
 708         known::bswap,
 709         known::caller_location,
 710         known::ctlz,
 711         known::ctpop,
 712         known::cttz,
 713         known::discriminant_value,
 714         known::forget,
 715         known::likely,
 716         known::maxnumf32,
 717         known::maxnumf64,
 718         known::min_align_of,
 719         known::minnumf32,
 720         known::minnumf64,
 721         known::mul_with_overflow,
 722         known::needs_drop,
 723         known::ptr_guaranteed_eq,
 724         known::ptr_guaranteed_ne,
 725         known::rotate_left,
 726         known::rotate_right,
 727         known::rustc_peek,
 728         known::saturating_add,
 729         known::saturating_sub,
 730         known::size_of,
 731         known::sub_with_overflow,
 732         known::type_id,
 733         known::type_name,
 734         known::unlikely,
 735         known::variant_count,
 736         known::wrapping_add,
 737         known::wrapping_mul,
 738         known::wrapping_sub,
 739     ]
 740     .contains(name)
 741 }
 742
 743 fn lower_abi(abi: ast::Abi) -> Interned<str> {
 744     // FIXME: Abi::abi() -> Option<SyntaxToken>?
 745     match abi.syntax().last_token() {
 746         Some(tok) if tok.kind() == SyntaxKind::STRING => {
 747             // FIXME: Better way to unescape?
 748             Interned::new_str(tok.text().trim_matches('"'))
 749         }
 750         _ => {
 751             // `extern` default to be `extern "C"`.
 752             Interned::new_str("C")
 753         }
 754     }
 755 }
 756
 757 struct UseTreeLowering<'a> {
 758     db: &'a dyn DefDatabase,
 759     hygiene: &'a Hygiene,
 760     mapping: Arena<ast::UseTree>,
 761 }
 762
 763 impl UseTreeLowering<'_> {
 764     fn lower_use_tree(&mut self, tree: ast::UseTree) -> Option<UseTree> {
 765         if let Some(use_tree_list) = tree.use_tree_list() {
 766             let prefix = match tree.path() {
 767                 // E.g. use something::{{{inner}}};
 768                 None => None,
 769                 // E.g. `use something::{inner}` (prefix is `None`, path is `something`)
 770                 // or `use something::{path::{inner::{innerer}}}` (prefix is `something::path`, path is `inner`)
 771                 Some(path) => {
 772                     match ModPath::from_src(self.db.upcast(), path, self.hygiene) {
 773                         Some(it) => Some(it),
 774                         None => return None, // FIXME: report errors somewhere
 775                     }
 776                 }
 777             };
 778
 779             let list =
 780                 use_tree_list.use_trees().filter_map(|tree| self.lower_use_tree(tree)).collect();
 781
 782             Some(
 783                 self.use_tree(
 784                     UseTreeKind::Prefixed { prefix: prefix.map(Interned::new), list },
 785                     tree,
 786                 ),
 787             )
 788         } else {
 789             let is_glob = tree.star_token().is_some();
 790             let path = match tree.path() {
 791                 Some(path) => Some(ModPath::from_src(self.db.upcast(), path, self.hygiene)?),
 792                 None => None,
 793             };
 794             let alias = tree.rename().map(|a| {
 795                 a.name().map(|it| it.as_name()).map_or(ImportAlias::Underscore, ImportAlias::Alias)
 796             });
 797             if alias.is_some() && is_glob {
 798                 return None;
 799             }
 800
 801             match (path, alias, is_glob) {
 802                 (path, None, true) => {
 803                     if path.is_none() {
 804                         cov_mark::hit!(glob_enum_group);
 805                     }
 806                     Some(self.use_tree(UseTreeKind::Glob { path: path.map(Interned::new) }, tree))
 807                 }
 808                 // Globs can't be renamed
 809                 (_, Some(_), true) | (None, None, false) => None,
 810                 // `bla::{ as Name}` is invalid
 811                 (None, Some(_), false) => None,
 812                 (Some(path), alias, false) => Some(
 813                     self.use_tree(UseTreeKind::Single { path: Interned::new(path), alias }, tree),
 814                 ),
 815             }
 816         }
 817     }
 818
 819     fn use_tree(&mut self, kind: UseTreeKind, ast: ast::UseTree) -> UseTree {
 820         let index = self.mapping.alloc(ast);
 821         UseTree { index, kind }
 822     }
 823 }
 824
 825 pub(super) fn lower_use_tree(
 826     db: &dyn DefDatabase,
 827     hygiene: &Hygiene,
 828     tree: ast::UseTree,
 829 ) -> Option<(UseTree, Arena<ast::UseTree>)> {
 830     let mut lowering = UseTreeLowering { db, hygiene, mapping: Arena::new() };
 831     let tree = lowering.lower_use_tree(tree)?;
 832     Some((tree, lowering.mapping))
 833 }