From 2ffecb841b078e2952b200ece21d1c2cdad52f9a Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Sat, 7 May 2016 13:04:22 +0200
Subject: Fix comments in Eq class and make it a trait.

---
 src/scala/Eq.scala | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

(limited to 'src/scala')

diff --git a/src/scala/Eq.scala b/src/scala/Eq.scala
index 6d993ac39..1ac6e55d2 100644
--- a/src/scala/Eq.scala
+++ b/src/scala/Eq.scala
@@ -2,9 +2,9 @@ package scala
 
 import annotation.implicitNotFound
 
-/** A marker class indicating that values of kind `T` can be compared. */
+/** A marker trait indicating that values of kind `T` can be compared to values of type `U`. */
 @implicitNotFound("Values of types ${L} and ${R} cannot be compared with == or !=")
-class Eq[-L, -R]
+trait Eq[-L, -R]
 
 /** Besides being a companion object, this object
  *  can also be used as a value that's compatible with
@@ -12,8 +12,11 @@ class Eq[-L, -R]
  */
 object Eq extends Eq[Any, Any] {
 
-  /** An implicit that provides an `Eq` instance for all types `T`
-   *  such that `T <: EqClass[T]`.
+  /** A fall-back implicit to compare values of any types.
+   *  The compiler will restrict implicit instances of `eqAny`. An instance
+   *  `eqAny[T, U]` is _invalid_ if `T` or `U` is a non-bottom type that
+   *  has an implicit `Eq[T, T]` (respectively `Eq[U, U]`) instance.
+   *  An implicit search will fail instead of returning an invalid `eqAny` instance,
    */
   implicit def eqAny[L, R]: Eq[L, R] = Eq
 }
-- 
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