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change docs on Res::SelfTy

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This commit is contained in:
Ellen 2022-02-12 11:18:21 +00:00
parent e81e09a24e
commit 9130af2e4d
1 changed files with 35 additions and 27 deletions
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62
compiler/rustc_hir/src/def.rs
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@ -266,57 +266,65 @@ pub enum Res<Id = hir::HirId> {
///
/// **Belongs to the type namespace.**
PrimTy(hir::PrimTy),
/// The `Self` type, optionally with the trait it is associated with
/// and optionally with the [`DefId`] of the impl it is associated with.
/// The `Self` type, optionally with the [`DefId`] of the trait it belongs to and
/// optionally with the [`DefId`] of the item introducing the `Self` type alias.
///
/// **Belongs to the type namespace.**
///
/// For example, the `Self` in
///
/// Examples:
/// ```
/// struct Bar(Box<Self>);
/// // `Res::SelfTy { trait_: None, alias_of: Some(Bar) }`
///
/// trait Foo {
/// fn foo() -> Box<Self>;
/// // `Res::SelfTy { trait_: Some(Foo), alias_of: None }`
/// }
/// ```
///
/// would have the [`DefId`] of `Foo` associated with it. The `Self` in
///
/// ```
/// struct Bar;
///
///
/// impl Bar {
/// fn new() -> Self { Bar }
/// fn blah() {
/// let _: Self;
/// // `Res::SelfTy { trait_: None, alias_of: Some(::{impl#0}) }`
/// }
/// }
/// ```
///
/// would have the [`DefId`] of the impl associated with it. Finally, the `Self` in
///
/// ```
///
/// impl Foo for Bar {
/// fn foo() -> Box<Self> { Box::new(Bar) }
/// fn foo() -> Box<Self> {
/// // `Res::SelfTy { trait_: Some(Foo), alias_of: Some(::{impl#1}) }`
/// let _: Self;
/// // `Res::SelfTy { trait_: Some(Foo), alias_of: Some(::{impl#1}) }`
///
/// todo!()
/// }
/// }
/// ```
///
/// would have both the [`DefId`] of `Foo` and the [`DefId`] of the impl
/// associated with it.
///
/// *See also [`Res::SelfCtor`].*
///
/// -----
///
/// HACK(min_const_generics): impl self types also have an optional requirement to **not** mention
/// HACK(min_const_generics): self types also have an optional requirement to **not** mention
/// any generic parameters to allow the following with `min_const_generics`:
/// ```
/// impl Foo { fn test() -> [u8; std::mem::size_of::<Self>()] { todo!() } }
///
/// struct Bar([u8; baz::<Self>()]);
/// const fn baz<T>() -> usize { 10 }
/// ```
/// We do however allow `Self` in repeat expression even if it is generic to not break code
/// which already works on stable while causing the `const_evaluatable_unchecked` future compat lint.
///
/// FIXME(generic_const_exprs): Remove this bodge once that feature is stable.
/// which already works on stable while causing the `const_evaluatable_unchecked` future compat lint:
/// ```
/// fn foo<T>() {
/// let _bar = [1_u8; std::mem::size_of::<*mut T>()];
/// }
/// ```
// FIXME(generic_const_exprs): Remove this bodge once that feature is stable.
SelfTy {
/// Optionally, the trait associated with this `Self` type.
/// The trait this `Self` is a generic arg for.
trait_: Option<DefId>,
/// Optionally, the impl or adt associated with this `Self` type.
/// The item introducing the `Self` type alias. Can be used in the `type_of` query
/// to get the underlying type. Additionally whether the `Self` type is disallowed
/// from mentioning generics (i.e. when used in an anonymous constant).
alias_to: Option<(DefId, bool)>,
},
/// A tool attribute module; e.g., the `rustfmt` in `#[rustfmt::skip]`.