Fix #2698: Move eqXYZ instances to Eq

Author: odersky

library/src/dotty/DottyPredef.scala

@@ -6,46 +6,16 @@ import scala.collection.Seq
 
 /** unimplemented implicit for TypeTag */
 object DottyPredef {
+
   /** A fall-back implicit to compare values of any types.
    *  The compiler will restrict implicit instances of `eqAny`. An instance
    *  `eqAny[T, U]` is _valid_ if `T <: U` or `U <: T` or both `T` and `U` are
    *  Eq-free. A type `S` is Eq-free if there is no implicit instance of `Eq[S, S]`.
    *  An implicit search will fail instead of returning an invalid `eqAny` instance.
+   *  The method is here instead of the `Eq` object so that it can be disabled.
    */
   implicit def eqAny[L, R]: Eq[L, R] = Eq
 
-  implicit def eqNumber   : Eq[Number, Number] = Eq
-  implicit def eqString   : Eq[String, String] = Eq
-  implicit def eqBoolean  : Eq[Boolean, Boolean] = Eq
-  implicit def eqByte     : Eq[Byte, Byte] = Eq
-  implicit def eqShort    : Eq[Short, Short] = Eq
-  implicit def eqChar     : Eq[Char, Char] = Eq
-  implicit def eqInt      : Eq[Int, Int] = Eq
-  implicit def eqLong     : Eq[Long, Long] = Eq
-  implicit def eqFloat    : Eq[Float, Float] = Eq
-  implicit def eqDouble   : Eq[Double, Double] = Eq
-  implicit def eqUnit     : Eq[Unit, Unit] = Eq
-
-  // true asymmetry, modeling the (somewhat problematic) nature of equals on Proxies
-  implicit def eqProxy    : Eq[Proxy, Any]     = Eq
-
-  implicit def eqSeq[T, U](implicit eq: Eq[T, U]): Eq[Seq[T], Seq[U]] = Eq
-
-  implicit def eqByteNum  : Eq[Byte, Number]   = Eq
-  implicit def eqNumByte  : Eq[Number, Byte]   = Eq
-  implicit def eqCharNum  : Eq[Char, Number]   = Eq
-  implicit def eqNumChar  : Eq[Number, Char]   = Eq
-  implicit def eqShortNum : Eq[Short, Number]  = Eq
-  implicit def eqNumShort : Eq[Number, Short]  = Eq
-  implicit def eqIntNum   : Eq[Int, Number]    = Eq
-  implicit def eqNumInt   : Eq[Number, Int]    = Eq
-  implicit def eqLongNum  : Eq[Long, Number]   = Eq
-  implicit def eqNumLong  : Eq[Number, Long]   = Eq
-  implicit def eqFloatNum : Eq[Float, Number]  = Eq
-  implicit def eqNumFloat : Eq[Number, Float]  = Eq
-  implicit def eqDoubleNum: Eq[Double, Number] = Eq
-  implicit def eqNumDouble: Eq[Number, Double] = Eq
-
   /** A class for implicit values that can serve as implicit conversions
    *  The implicit resolution algorithm will act as if there existed
    *  the additional implicit definition:

library/src/scala/Eq.scala

@@ -10,5 +10,39 @@ sealed trait Eq[-L, -R]
  *  can also be used as a value that's compatible with
  *  any instance of `Eq`.
  */
-object Eq extends Eq[Any, Any]
+object Eq extends Eq[Any, Any] {
 
+  // Instances of `Eq` for common types
+
+  implicit def eqNumber   : Eq[Number, Number] = Eq
+  implicit def eqString   : Eq[String, String] = Eq
+  implicit def eqBoolean  : Eq[Boolean, Boolean] = Eq
+  implicit def eqByte     : Eq[Byte, Byte] = Eq
+  implicit def eqShort    : Eq[Short, Short] = Eq
+  implicit def eqChar     : Eq[Char, Char] = Eq
+  implicit def eqInt      : Eq[Int, Int] = Eq
+  implicit def eqLong     : Eq[Long, Long] = Eq
+  implicit def eqFloat    : Eq[Float, Float] = Eq
+  implicit def eqDouble   : Eq[Double, Double] = Eq
+  implicit def eqUnit     : Eq[Unit, Unit] = Eq
+
+  // true asymmetry, modeling the (somewhat problematic) nature of equals on Proxies
+  implicit def eqProxy    : Eq[Proxy, Any]     = Eq
+
+  implicit def eqSeq[T, U](implicit eq: Eq[T, U]): Eq[Seq[T], Seq[U]] = Eq
+
+  implicit def eqByteNum  : Eq[Byte, Number]   = Eq
+  implicit def eqNumByte  : Eq[Number, Byte]   = Eq
+  implicit def eqCharNum  : Eq[Char, Number]   = Eq
+  implicit def eqNumChar  : Eq[Number, Char]   = Eq
+  implicit def eqShortNum : Eq[Short, Number]  = Eq
+  implicit def eqNumShort : Eq[Number, Short]  = Eq
+  implicit def eqIntNum   : Eq[Int, Number]    = Eq
+  implicit def eqNumInt   : Eq[Number, Int]    = Eq
+  implicit def eqLongNum  : Eq[Long, Number]   = Eq
+  implicit def eqNumLong  : Eq[Number, Long]   = Eq
+  implicit def eqFloatNum : Eq[Float, Number]  = Eq
+  implicit def eqNumFloat : Eq[Number, Float]  = Eq
+  implicit def eqDoubleNum: Eq[Double, Number] = Eq
+  implicit def eqNumDouble: Eq[Number, Double] = Eq
+}