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Rollup merge of #78793 - camelid:fixup-structuraleq, r=jyn514

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Clean up `StructuralEq` docs
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Mara Bos 2020-11-22 23:01:00 +01:00 committed by GitHub
parent b249844c33 b813c72723
commit 8a623e6f98
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1 changed files with 8 additions and 5 deletions
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13
library/core/src/marker.rs
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@ -156,18 +156,18 @@ pub trait StructuralPartialEq {
/// Required trait for constants used in pattern matches.
///
/// Any type that derives `Eq` automatically implements this trait, *regardless*
/// of whether its type-parameters implement `Eq`.
/// of whether its type parameters implement `Eq`.
///
/// This is a hack to workaround a limitation in our type-system.
/// This is a hack to work around a limitation in our type system.
///
/// Background:
/// # Background
///
/// We want to require that types of consts used in pattern matches
/// have the attribute `#[derive(PartialEq, Eq)]`.
///
/// In a more ideal world, we could check that requirement by just checking that
/// the given type implements both (1.) the `StructuralPartialEq` trait *and*
/// (2.) the `Eq` trait. However, you can have ADTs that *do* `derive(PartialEq, Eq)`,
/// the given type implements both the `StructuralPartialEq` trait *and*
/// the `Eq` trait. However, you can have ADTs that *do* `derive(PartialEq, Eq)`,
/// and be a case that we want the compiler to accept, and yet the constant's
/// type fails to implement `Eq`.
///
@ -176,8 +176,11 @@ pub trait StructuralPartialEq {
/// ```rust
/// #[derive(PartialEq, Eq)]
/// struct Wrap<X>(X);
///
/// fn higher_order(_: &()) { }
///
/// const CFN: Wrap<fn(&())> = Wrap(higher_order);
///
/// fn main() {
/// match CFN {
/// CFN => {}