compiler/rustc_hir/src/def.rs

   1 use crate::hir;
   2
   3 use rustc_ast as ast;
   4 use rustc_ast::NodeId;
   5 use rustc_macros::HashStable_Generic;
   6 use rustc_span::def_id::{DefId, LocalDefId};
   7 use rustc_span::hygiene::MacroKind;
   8 use rustc_span::Symbol;
   9
  10 use std::array::IntoIter;
  11 use std::fmt::Debug;
  12
  13 /// Encodes if a `DefKind::Ctor` is the constructor of an enum variant or a struct.
  14 #[derive(Clone, Copy, PartialEq, Eq, Encodable, Decodable, Hash, Debug)]
  15 #[derive(HashStable_Generic)]
  16 pub enum CtorOf {
  17     /// This `DefKind::Ctor` is a synthesized constructor of a tuple or unit struct.
  18     Struct,
  19     /// This `DefKind::Ctor` is a synthesized constructor of a tuple or unit variant.
  20     Variant,
  21 }
  22
  23 /// What kind of constructor something is.
  24 #[derive(Clone, Copy, PartialEq, Eq, Encodable, Decodable, Hash, Debug)]
  25 #[derive(HashStable_Generic)]
  26 pub enum CtorKind {
  27     /// Constructor function automatically created by a tuple struct/variant.
  28     Fn,
  29     /// Constructor constant automatically created by a unit struct/variant.
  30     Const,
  31     /// Unusable name in value namespace created by a struct variant.
  32     Fictive,
  33 }
  34
  35 /// An attribute that is not a macro; e.g., `#[inline]` or `#[rustfmt::skip]`.
  36 #[derive(Clone, Copy, PartialEq, Eq, Encodable, Decodable, Hash, Debug)]
  37 #[derive(HashStable_Generic)]
  38 pub enum NonMacroAttrKind {
  39     /// Single-segment attribute defined by the language (`#[inline]`)
  40     Builtin(Symbol),
  41     /// Multi-segment custom attribute living in a "tool module" (`#[rustfmt::skip]`).
  42     Tool,
  43     /// Single-segment custom attribute registered by a derive macro (`#[serde(default)]`).
  44     DeriveHelper,
  45     /// Single-segment custom attribute registered by a derive macro
  46     /// but used before that derive macro was expanded (deprecated).
  47     DeriveHelperCompat,
  48     /// Single-segment custom attribute registered with `#[register_attr]`.
  49     Registered,
  50 }
  51
  52 /// What kind of definition something is; e.g., `mod` vs `struct`.
  53 #[derive(Clone, Copy, PartialEq, Eq, Encodable, Decodable, Hash, Debug)]
  54 #[derive(HashStable_Generic)]
  55 pub enum DefKind {
  56     // Type namespace
  57     Mod,
  58     /// Refers to the struct itself, [`DefKind::Ctor`] refers to its constructor if it exists.
  59     Struct,
  60     Union,
  61     Enum,
  62     /// Refers to the variant itself, [`DefKind::Ctor`] refers to its constructor if it exists.
  63     Variant,
  64     Trait,
  65     /// Type alias: `type Foo = Bar;`
  66     TyAlias,
  67     /// Type from an `extern` block.
  68     ForeignTy,
  69     /// Trait alias: `trait IntIterator = Iterator<Item = i32>;`
  70     TraitAlias,
  71     /// Associated type: `trait MyTrait { type Assoc; }`
  72     AssocTy,
  73     /// Type parameter: the `T` in `struct Vec<T> { ... }`
  74     TyParam,
  75
  76     // Value namespace
  77     Fn,
  78     Const,
  79     /// Constant generic parameter: `struct Foo<const N: usize> { ... }`
  80     ConstParam,
  81     Static(ast::Mutability),
  82     /// Refers to the struct or enum variant's constructor.
  83     ///
  84     /// The reason `Ctor` exists in addition to [`DefKind::Struct`] and
  85     /// [`DefKind::Variant`] is because structs and enum variants exist
  86     /// in the *type* namespace, whereas struct and enum variant *constructors*
  87     /// exist in the *value* namespace.
  88     ///
  89     /// You may wonder why enum variants exist in the type namespace as opposed
  90     /// to the value namespace. Check out [RFC 2593] for intuition on why that is.
  91     ///
  92     /// [RFC 2593]: https://github.com/rust-lang/rfcs/pull/2593
  93     Ctor(CtorOf, CtorKind),
  94     /// Associated function: `impl MyStruct { fn associated() {} }`
  95     /// or `trait Foo { fn associated() {} }`
  96     AssocFn,
  97     /// Associated constant: `trait MyTrait { const ASSOC: usize; }`
  98     AssocConst,
  99
 100     // Macro namespace
 101     Macro(MacroKind),
 102
 103     // Not namespaced (or they are, but we don't treat them so)
 104     ExternCrate,
 105     Use,
 106     /// An `extern` block.
 107     ForeignMod,
 108     /// Anonymous constant, e.g. the `1 + 2` in `[u8; 1 + 2]`
 109     AnonConst,
 110     /// An inline constant, e.g. `const { 1 + 2 }`
 111     InlineConst,
 112     /// Opaque type, aka `impl Trait`.
 113     OpaqueTy,
 114     Field,
 115     /// Lifetime parameter: the `'a` in `struct Foo<'a> { ... }`
 116     LifetimeParam,
 117     /// A use of `global_asm!`.
 118     GlobalAsm,
 119     Impl,
 120     Closure,
 121     Generator,
 122 }
 123
 124 impl DefKind {
 125     pub fn descr(self, def_id: DefId) -> &'static str {
 126         match self {
 127             DefKind::Fn => "function",
 128             DefKind::Mod if def_id.is_crate_root() && !def_id.is_local() => "crate",
 129             DefKind::Mod => "module",
 130             DefKind::Static(..) => "static",
 131             DefKind::Enum => "enum",
 132             DefKind::Variant => "variant",
 133             DefKind::Ctor(CtorOf::Variant, CtorKind::Fn) => "tuple variant",
 134             DefKind::Ctor(CtorOf::Variant, CtorKind::Const) => "unit variant",
 135             DefKind::Ctor(CtorOf::Variant, CtorKind::Fictive) => "struct variant",
 136             DefKind::Struct => "struct",
 137             DefKind::Ctor(CtorOf::Struct, CtorKind::Fn) => "tuple struct",
 138             DefKind::Ctor(CtorOf::Struct, CtorKind::Const) => "unit struct",
 139             DefKind::Ctor(CtorOf::Struct, CtorKind::Fictive) => {
 140                 panic!("impossible struct constructor")
 141             }
 142             DefKind::OpaqueTy => "opaque type",
 143             DefKind::TyAlias => "type alias",
 144             DefKind::TraitAlias => "trait alias",
 145             DefKind::AssocTy => "associated type",
 146             DefKind::Union => "union",
 147             DefKind::Trait => "trait",
 148             DefKind::ForeignTy => "foreign type",
 149             DefKind::AssocFn => "associated function",
 150             DefKind::Const => "constant",
 151             DefKind::AssocConst => "associated constant",
 152             DefKind::TyParam => "type parameter",
 153             DefKind::ConstParam => "const parameter",
 154             DefKind::Macro(macro_kind) => macro_kind.descr(),
 155             DefKind::LifetimeParam => "lifetime parameter",
 156             DefKind::Use => "import",
 157             DefKind::ForeignMod => "foreign module",
 158             DefKind::AnonConst => "constant expression",
 159             DefKind::InlineConst => "inline constant",
 160             DefKind::Field => "field",
 161             DefKind::Impl => "implementation",
 162             DefKind::Closure => "closure",
 163             DefKind::Generator => "generator",
 164             DefKind::ExternCrate => "extern crate",
 165             DefKind::GlobalAsm => "global assembly block",
 166         }
 167     }
 168
 169     /// Gets an English article for the definition.
 170     pub fn article(&self) -> &'static str {
 171         match *self {
 172             DefKind::AssocTy
 173             | DefKind::AssocConst
 174             | DefKind::AssocFn
 175             | DefKind::Enum
 176             | DefKind::OpaqueTy
 177             | DefKind::Impl
 178             | DefKind::Use
 179             | DefKind::InlineConst
 180             | DefKind::ExternCrate => "an",
 181             DefKind::Macro(macro_kind) => macro_kind.article(),
 182             _ => "a",
 183         }
 184     }
 185
 186     pub fn ns(&self) -> Option<Namespace> {
 187         match self {
 188             DefKind::Mod
 189             | DefKind::Struct
 190             | DefKind::Union
 191             | DefKind::Enum
 192             | DefKind::Variant
 193             | DefKind::Trait
 194             | DefKind::OpaqueTy
 195             | DefKind::TyAlias
 196             | DefKind::ForeignTy
 197             | DefKind::TraitAlias
 198             | DefKind::AssocTy
 199             | DefKind::TyParam => Some(Namespace::TypeNS),
 200
 201             DefKind::Fn
 202             | DefKind::Const
 203             | DefKind::ConstParam
 204             | DefKind::Static(..)
 205             | DefKind::Ctor(..)
 206             | DefKind::AssocFn
 207             | DefKind::AssocConst => Some(Namespace::ValueNS),
 208
 209             DefKind::Macro(..) => Some(Namespace::MacroNS),
 210
 211             // Not namespaced.
 212             DefKind::AnonConst
 213             | DefKind::InlineConst
 214             | DefKind::Field
 215             | DefKind::LifetimeParam
 216             | DefKind::ExternCrate
 217             | DefKind::Closure
 218             | DefKind::Generator
 219             | DefKind::Use
 220             | DefKind::ForeignMod
 221             | DefKind::GlobalAsm
 222             | DefKind::Impl => None,
 223         }
 224     }
 225
 226     #[inline]
 227     pub fn is_fn_like(self) -> bool {
 228         match self {
 229             DefKind::Fn | DefKind::AssocFn | DefKind::Closure | DefKind::Generator => true,
 230             _ => false,
 231         }
 232     }
 233
 234     /// Whether `query get_codegen_attrs` should be used with this definition.
 235     pub fn has_codegen_attrs(self) -> bool {
 236         match self {
 237             DefKind::Fn
 238             | DefKind::AssocFn
 239             | DefKind::Ctor(..)
 240             | DefKind::Closure
 241             | DefKind::Generator
 242             | DefKind::Static(_) => true,
 243             DefKind::Mod
 244             | DefKind::Struct
 245             | DefKind::Union
 246             | DefKind::Enum
 247             | DefKind::Variant
 248             | DefKind::Trait
 249             | DefKind::TyAlias
 250             | DefKind::ForeignTy
 251             | DefKind::TraitAlias
 252             | DefKind::AssocTy
 253             | DefKind::Const
 254             | DefKind::AssocConst
 255             | DefKind::Macro(..)
 256             | DefKind::Use
 257             | DefKind::ForeignMod
 258             | DefKind::OpaqueTy
 259             | DefKind::Impl
 260             | DefKind::Field
 261             | DefKind::TyParam
 262             | DefKind::ConstParam
 263             | DefKind::LifetimeParam
 264             | DefKind::AnonConst
 265             | DefKind::InlineConst
 266             | DefKind::GlobalAsm
 267             | DefKind::ExternCrate => false,
 268         }
 269     }
 270 }
 271
 272 /// The resolution of a path or export.
 273 ///
 274 /// For every path or identifier in Rust, the compiler must determine
 275 /// what the path refers to. This process is called name resolution,
 276 /// and `Res` is the primary result of name resolution.
 277 ///
 278 /// For example, everything prefixed with `/* Res */` in this example has
 279 /// an associated `Res`:
 280 ///
 281 /// ```
 282 /// fn str_to_string(s: & /* Res */ str) -> /* Res */ String {
 283 ///     /* Res */ String::from(/* Res */ s)
 284 /// }
 285 ///
 286 /// /* Res */ str_to_string("hello");
 287 /// ```
 288 ///
 289 /// The associated `Res`s will be:
 290 ///
 291 /// - `str` will resolve to [`Res::PrimTy`];
 292 /// - `String` will resolve to [`Res::Def`], and the `Res` will include the [`DefId`]
 293 ///   for `String` as defined in the standard library;
 294 /// - `String::from` will also resolve to [`Res::Def`], with the [`DefId`]
 295 ///   pointing to `String::from`;
 296 /// - `s` will resolve to [`Res::Local`];
 297 /// - the call to `str_to_string` will resolve to [`Res::Def`], with the [`DefId`]
 298 ///   pointing to the definition of `str_to_string` in the current crate.
 299 //
 300 #[derive(Clone, Copy, PartialEq, Eq, Encodable, Decodable, Hash, Debug)]
 301 #[derive(HashStable_Generic)]
 302 pub enum Res<Id = hir::HirId> {
 303     /// Definition having a unique ID (`DefId`), corresponds to something defined in user code.
 304     ///
 305     /// **Not bound to a specific namespace.**
 306     Def(DefKind, DefId),
 307
 308     // Type namespace
 309     /// A primitive type such as `i32` or `str`.
 310     ///
 311     /// **Belongs to the type namespace.**
 312     PrimTy(hir::PrimTy),
 313     /// The `Self` type, optionally with the [`DefId`] of the trait it belongs to and
 314     /// optionally with the [`DefId`] of the item introducing the `Self` type alias.
 315     ///
 316     /// **Belongs to the type namespace.**
 317     ///
 318     /// Examples:
 319     /// ```
 320     /// struct Bar(Box<Self>);
 321     /// // `Res::SelfTy { trait_: None, alias_of: Some(Bar) }`
 322     ///
 323     /// trait Foo {
 324     ///     fn foo() -> Box<Self>;
 325     ///     // `Res::SelfTy { trait_: Some(Foo), alias_of: None }`
 326     /// }
 327     ///
 328     /// impl Bar {
 329     ///     fn blah() {
 330     ///         let _: Self;
 331     ///         // `Res::SelfTy { trait_: None, alias_of: Some(::{impl#0}) }`
 332     ///     }
 333     /// }
 334     ///
 335     /// impl Foo for Bar {
 336     ///     fn foo() -> Box<Self> {
 337     ///     // `Res::SelfTy { trait_: Some(Foo), alias_of: Some(::{impl#1}) }`
 338     ///         let _: Self;
 339     ///         // `Res::SelfTy { trait_: Some(Foo), alias_of: Some(::{impl#1}) }`
 340     ///
 341     ///         todo!()
 342     ///     }
 343     /// }
 344     /// ```
 345     ///
 346     /// *See also [`Res::SelfCtor`].*
 347     ///
 348     /// -----
 349     ///
 350     /// HACK(min_const_generics): self types also have an optional requirement to **not** mention
 351     /// any generic parameters to allow the following with `min_const_generics`:
 352     /// ```
 353     /// # struct Foo;
 354     /// impl Foo { fn test() -> [u8; std::mem::size_of::<Self>()] { todo!() } }
 355     ///
 356     /// struct Bar([u8; baz::<Self>()]);
 357     /// const fn baz<T>() -> usize { 10 }
 358     /// ```
 359     /// We do however allow `Self` in repeat expression even if it is generic to not break code
 360     /// which already works on stable while causing the `const_evaluatable_unchecked` future compat lint:
 361     /// ```
 362     /// fn foo<T>() {
 363     ///     let _bar = [1_u8; std::mem::size_of::<*mut T>()];
 364     /// }
 365     /// ```
 366     // FIXME(generic_const_exprs): Remove this bodge once that feature is stable.
 367     SelfTy {
 368         /// The trait this `Self` is a generic arg for.
 369         trait_: Option<DefId>,
 370         /// The item introducing the `Self` type alias. Can be used in the `type_of` query
 371         /// to get the underlying type. Additionally whether the `Self` type is disallowed
 372         /// from mentioning generics (i.e. when used in an anonymous constant).
 373         alias_to: Option<(DefId, bool)>,
 374     },
 375     /// A tool attribute module; e.g., the `rustfmt` in `#[rustfmt::skip]`.
 376     ///
 377     /// **Belongs to the type namespace.**
 378     ToolMod,
 379
 380     // Value namespace
 381     /// The `Self` constructor, along with the [`DefId`]
 382     /// of the impl it is associated with.
 383     ///
 384     /// **Belongs to the value namespace.**
 385     ///
 386     /// *See also [`Res::SelfTy`].*
 387     SelfCtor(DefId),
 388     /// A local variable or function parameter.
 389     ///
 390     /// **Belongs to the value namespace.**
 391     Local(Id),
 392
 393     // Macro namespace
 394     /// An attribute that is *not* implemented via macro.
 395     /// E.g., `#[inline]` and `#[rustfmt::skip]`, which are essentially directives,
 396     /// as opposed to `#[test]`, which is a builtin macro.
 397     ///
 398     /// **Belongs to the macro namespace.**
 399     NonMacroAttr(NonMacroAttrKind), // e.g., `#[inline]` or `#[rustfmt::skip]`
 400
 401     // All namespaces
 402     /// Name resolution failed. We use a dummy `Res` variant so later phases
 403     /// of the compiler won't crash and can instead report more errors.
 404     ///
 405     /// **Not bound to a specific namespace.**
 406     Err,
 407 }
 408
 409 /// The result of resolving a path before lowering to HIR,
 410 /// with "module" segments resolved and associated item
 411 /// segments deferred to type checking.
 412 /// `base_res` is the resolution of the resolved part of the
 413 /// path, `unresolved_segments` is the number of unresolved
 414 /// segments.
 415 ///
 416 /// ```text
 417 /// module::Type::AssocX::AssocY::MethodOrAssocType
 418 /// ^~~~~~~~~~~~  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 419 /// base_res      unresolved_segments = 3
 420 ///
 421 /// <T as Trait>::AssocX::AssocY::MethodOrAssocType
 422 ///       ^~~~~~~~~~~~~~  ^~~~~~~~~~~~~~~~~~~~~~~~~
 423 ///       base_res        unresolved_segments = 2
 424 /// ```
 425 #[derive(Copy, Clone, Debug)]
 426 pub struct PartialRes {
 427     base_res: Res<NodeId>,
 428     unresolved_segments: usize,
 429 }
 430
 431 impl PartialRes {
 432     #[inline]
 433     pub fn new(base_res: Res<NodeId>) -> Self {
 434         PartialRes { base_res, unresolved_segments: 0 }
 435     }
 436
 437     #[inline]
 438     pub fn with_unresolved_segments(base_res: Res<NodeId>, mut unresolved_segments: usize) -> Self {
 439         if base_res == Res::Err {
 440             unresolved_segments = 0
 441         }
 442         PartialRes { base_res, unresolved_segments }
 443     }
 444
 445     #[inline]
 446     pub fn base_res(&self) -> Res<NodeId> {
 447         self.base_res
 448     }
 449
 450     #[inline]
 451     pub fn unresolved_segments(&self) -> usize {
 452         self.unresolved_segments
 453     }
 454 }
 455
 456 /// Different kinds of symbols can coexist even if they share the same textual name.
 457 /// Therefore, they each have a separate universe (known as a "namespace").
 458 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
 459 pub enum Namespace {
 460     /// The type namespace includes `struct`s, `enum`s, `union`s, `trait`s, and `mod`s
 461     /// (and, by extension, crates).
 462     ///
 463     /// Note that the type namespace includes other items; this is not an
 464     /// exhaustive list.
 465     TypeNS,
 466     /// The value namespace includes `fn`s, `const`s, `static`s, and local variables (including function arguments).
 467     ValueNS,
 468     /// The macro namespace includes `macro_rules!` macros, declarative `macro`s,
 469     /// procedural macros, attribute macros, `derive` macros, and non-macro attributes
 470     /// like `#[inline]` and `#[rustfmt::skip]`.
 471     MacroNS,
 472 }
 473
 474 impl Namespace {
 475     /// The English description of the namespace.
 476     pub fn descr(self) -> &'static str {
 477         match self {
 478             Self::TypeNS => "type",
 479             Self::ValueNS => "value",
 480             Self::MacroNS => "macro",
 481         }
 482     }
 483 }
 484
 485 /// Just a helper ‒ separate structure for each namespace.
 486 #[derive(Copy, Clone, Default, Debug)]
 487 pub struct PerNS<T> {
 488     pub value_ns: T,
 489     pub type_ns: T,
 490     pub macro_ns: T,
 491 }
 492
 493 impl<T> PerNS<T> {
 494     pub fn map<U, F: FnMut(T) -> U>(self, mut f: F) -> PerNS<U> {
 495         PerNS { value_ns: f(self.value_ns), type_ns: f(self.type_ns), macro_ns: f(self.macro_ns) }
 496     }
 497
 498     pub fn into_iter(self) -> IntoIter<T, 3> {
 499         [self.value_ns, self.type_ns, self.macro_ns].into_iter()
 500     }
 501
 502     pub fn iter(&self) -> IntoIter<&T, 3> {
 503         [&self.value_ns, &self.type_ns, &self.macro_ns].into_iter()
 504     }
 505 }
 506
 507 impl<T> ::std::ops::Index<Namespace> for PerNS<T> {
 508     type Output = T;
 509
 510     fn index(&self, ns: Namespace) -> &T {
 511         match ns {
 512             Namespace::ValueNS => &self.value_ns,
 513             Namespace::TypeNS => &self.type_ns,
 514             Namespace::MacroNS => &self.macro_ns,
 515         }
 516     }
 517 }
 518
 519 impl<T> ::std::ops::IndexMut<Namespace> for PerNS<T> {
 520     fn index_mut(&mut self, ns: Namespace) -> &mut T {
 521         match ns {
 522             Namespace::ValueNS => &mut self.value_ns,
 523             Namespace::TypeNS => &mut self.type_ns,
 524             Namespace::MacroNS => &mut self.macro_ns,
 525         }
 526     }
 527 }
 528
 529 impl<T> PerNS<Option<T>> {
 530     /// Returns `true` if all the items in this collection are `None`.
 531     pub fn is_empty(&self) -> bool {
 532         self.type_ns.is_none() && self.value_ns.is_none() && self.macro_ns.is_none()
 533     }
 534
 535     /// Returns an iterator over the items which are `Some`.
 536     pub fn present_items(self) -> impl Iterator<Item = T> {
 537         [self.type_ns, self.value_ns, self.macro_ns].into_iter().flatten()
 538     }
 539 }
 540
 541 impl CtorKind {
 542     pub fn from_ast(vdata: &ast::VariantData) -> CtorKind {
 543         match *vdata {
 544             ast::VariantData::Tuple(..) => CtorKind::Fn,
 545             ast::VariantData::Unit(..) => CtorKind::Const,
 546             ast::VariantData::Struct(..) => CtorKind::Fictive,
 547         }
 548     }
 549
 550     pub fn from_hir(vdata: &hir::VariantData<'_>) -> CtorKind {
 551         match *vdata {
 552             hir::VariantData::Tuple(..) => CtorKind::Fn,
 553             hir::VariantData::Unit(..) => CtorKind::Const,
 554             hir::VariantData::Struct(..) => CtorKind::Fictive,
 555         }
 556     }
 557 }
 558
 559 impl NonMacroAttrKind {
 560     pub fn descr(self) -> &'static str {
 561         match self {
 562             NonMacroAttrKind::Builtin(..) => "built-in attribute",
 563             NonMacroAttrKind::Tool => "tool attribute",
 564             NonMacroAttrKind::DeriveHelper | NonMacroAttrKind::DeriveHelperCompat => {
 565                 "derive helper attribute"
 566             }
 567             NonMacroAttrKind::Registered => "explicitly registered attribute",
 568         }
 569     }
 570
 571     pub fn article(self) -> &'static str {
 572         match self {
 573             NonMacroAttrKind::Registered => "an",
 574             _ => "a",
 575         }
 576     }
 577
 578     /// Users of some attributes cannot mark them as used, so they are considered always used.
 579     pub fn is_used(self) -> bool {
 580         match self {
 581             NonMacroAttrKind::Tool
 582             | NonMacroAttrKind::DeriveHelper
 583             | NonMacroAttrKind::DeriveHelperCompat => true,
 584             NonMacroAttrKind::Builtin(..) | NonMacroAttrKind::Registered => false,
 585         }
 586     }
 587 }
 588
 589 impl<Id> Res<Id> {
 590     /// Return the `DefId` of this `Def` if it has an ID, else panic.
 591     pub fn def_id(&self) -> DefId
 592     where
 593         Id: Debug,
 594     {
 595         self.opt_def_id()
 596             .unwrap_or_else(|| panic!("attempted .def_id() on invalid res: {:?}", self))
 597     }
 598
 599     /// Return `Some(..)` with the `DefId` of this `Res` if it has a ID, else `None`.
 600     pub fn opt_def_id(&self) -> Option<DefId> {
 601         match *self {
 602             Res::Def(_, id) => Some(id),
 603
 604             Res::Local(..)
 605             | Res::PrimTy(..)
 606             | Res::SelfTy { .. }
 607             | Res::SelfCtor(..)
 608             | Res::ToolMod
 609             | Res::NonMacroAttr(..)
 610             | Res::Err => None,
 611         }
 612     }
 613
 614     /// Return the `DefId` of this `Res` if it represents a module.
 615     pub fn mod_def_id(&self) -> Option<DefId> {
 616         match *self {
 617             Res::Def(DefKind::Mod, id) => Some(id),
 618             _ => None,
 619         }
 620     }
 621
 622     /// A human readable name for the res kind ("function", "module", etc.).
 623     pub fn descr(&self) -> &'static str {
 624         match *self {
 625             Res::Def(kind, def_id) => kind.descr(def_id),
 626             Res::SelfCtor(..) => "self constructor",
 627             Res::PrimTy(..) => "builtin type",
 628             Res::Local(..) => "local variable",
 629             Res::SelfTy { .. } => "self type",
 630             Res::ToolMod => "tool module",
 631             Res::NonMacroAttr(attr_kind) => attr_kind.descr(),
 632             Res::Err => "unresolved item",
 633         }
 634     }
 635
 636     /// Gets an English article for the `Res`.
 637     pub fn article(&self) -> &'static str {
 638         match *self {
 639             Res::Def(kind, _) => kind.article(),
 640             Res::NonMacroAttr(kind) => kind.article(),
 641             Res::Err => "an",
 642             _ => "a",
 643         }
 644     }
 645
 646     pub fn map_id<R>(self, mut map: impl FnMut(Id) -> R) -> Res<R> {
 647         match self {
 648             Res::Def(kind, id) => Res::Def(kind, id),
 649             Res::SelfCtor(id) => Res::SelfCtor(id),
 650             Res::PrimTy(id) => Res::PrimTy(id),
 651             Res::Local(id) => Res::Local(map(id)),
 652             Res::SelfTy { trait_, alias_to } => Res::SelfTy { trait_, alias_to },
 653             Res::ToolMod => Res::ToolMod,
 654             Res::NonMacroAttr(attr_kind) => Res::NonMacroAttr(attr_kind),
 655             Res::Err => Res::Err,
 656         }
 657     }
 658
 659     pub fn apply_id<R, E>(self, mut map: impl FnMut(Id) -> Result<R, E>) -> Result<Res<R>, E> {
 660         Ok(match self {
 661             Res::Def(kind, id) => Res::Def(kind, id),
 662             Res::SelfCtor(id) => Res::SelfCtor(id),
 663             Res::PrimTy(id) => Res::PrimTy(id),
 664             Res::Local(id) => Res::Local(map(id)?),
 665             Res::SelfTy { trait_, alias_to } => Res::SelfTy { trait_, alias_to },
 666             Res::ToolMod => Res::ToolMod,
 667             Res::NonMacroAttr(attr_kind) => Res::NonMacroAttr(attr_kind),
 668             Res::Err => Res::Err,
 669         })
 670     }
 671
 672     #[track_caller]
 673     pub fn expect_non_local<OtherId>(self) -> Res<OtherId> {
 674         self.map_id(
 675             #[track_caller]
 676             |_| panic!("unexpected `Res::Local`"),
 677         )
 678     }
 679
 680     pub fn macro_kind(self) -> Option<MacroKind> {
 681         match self {
 682             Res::Def(DefKind::Macro(kind), _) => Some(kind),
 683             Res::NonMacroAttr(..) => Some(MacroKind::Attr),
 684             _ => None,
 685         }
 686     }
 687
 688     /// Returns `None` if this is `Res::Err`
 689     pub fn ns(&self) -> Option<Namespace> {
 690         match self {
 691             Res::Def(kind, ..) => kind.ns(),
 692             Res::PrimTy(..) | Res::SelfTy { .. } | Res::ToolMod => Some(Namespace::TypeNS),
 693             Res::SelfCtor(..) | Res::Local(..) => Some(Namespace::ValueNS),
 694             Res::NonMacroAttr(..) => Some(Namespace::MacroNS),
 695             Res::Err => None,
 696         }
 697     }
 698
 699     /// Always returns `true` if `self` is `Res::Err`
 700     pub fn matches_ns(&self, ns: Namespace) -> bool {
 701         self.ns().map_or(true, |actual_ns| actual_ns == ns)
 702     }
 703
 704     /// Returns whether such a resolved path can occur in a tuple struct/variant pattern
 705     pub fn expected_in_tuple_struct_pat(&self) -> bool {
 706         matches!(self, Res::Def(DefKind::Ctor(_, CtorKind::Fn), _) | Res::SelfCtor(..))
 707     }
 708
 709     /// Returns whether such a resolved path can occur in a unit struct/variant pattern
 710     pub fn expected_in_unit_struct_pat(&self) -> bool {
 711         matches!(self, Res::Def(DefKind::Ctor(_, CtorKind::Const), _) | Res::SelfCtor(..))
 712     }
 713 }
 714
 715 /// Resolution for a lifetime appearing in a type.
 716 #[derive(Copy, Clone, Debug)]
 717 pub enum LifetimeRes {
 718     /// Successfully linked the lifetime to a generic parameter.
 719     Param {
 720         /// Id of the generic parameter that introduced it.
 721         param: LocalDefId,
 722         /// Id of the introducing place. That can be:
 723         /// - an item's id, for the item's generic parameters;
 724         /// - a TraitRef's ref_id, identifying the `for<...>` binder;
 725         /// - a BareFn type's id.
 726         ///
 727         /// This information is used for impl-trait lifetime captures, to know when to or not to
 728         /// capture any given lifetime.
 729         binder: NodeId,
 730     },
 731     /// Created a generic parameter for an anonymous lifetime.
 732     Fresh {
 733         /// Id of the generic parameter that introduced it.
 734         ///
 735         /// Creating the associated `LocalDefId` is the responsibility of lowering.
 736         param: NodeId,
 737         /// Id of the introducing place. See `Param`.
 738         binder: NodeId,
 739     },
 740     /// This variant is used for anonymous lifetimes that we did not resolve during
 741     /// late resolution.  Shifting the work to the HIR lifetime resolver.
 742     Anonymous {
 743         /// Id of the introducing place. See `Param`.
 744         binder: NodeId,
 745         /// Whether this lifetime was spelled or elided.
 746         elided: bool,
 747     },
 748     /// Explicit `'static` lifetime.
 749     Static,
 750     /// Resolution failure.
 751     Error,
 752     /// HACK: This is used to recover the NodeId of an elided lifetime.
 753     ElidedAnchor { start: NodeId, end: NodeId },
 754 }