Optimize implicit def Predef.<???>ArrayOps

Remove object allocation overhead by peeling off abstraction layer,
revealing that the `ArrayOps` implicit conversions in `Predef`
return value classes.

d3f879a turned `ArrayOps.of<???>` into value classes,
but the non-`AnyVal` result type of the corresponding
`<???>arrayOps` implicit conversions (`ArrayOps[_]`) caused boxing anyway.

The optimized versions are introduced under a new name,
so that the old ones (without `implicit`) can be kept
for binary compatibility, for now.

Author: xuwei-k

src/library/scala/Predef.scala

@@ -329,16 +329,28 @@ object Predef extends LowPriorityImplicits with DeprecatedPredef {
     case null              => null
   }).asInstanceOf[ArrayOps[T]]
 
-  implicit def booleanArrayOps(xs: Array[Boolean]): ArrayOps[Boolean] = new ArrayOps.ofBoolean(xs)
-  implicit def byteArrayOps(xs: Array[Byte]): ArrayOps[Byte]          = new ArrayOps.ofByte(xs)
-  implicit def charArrayOps(xs: Array[Char]): ArrayOps[Char]          = new ArrayOps.ofChar(xs)
-  implicit def doubleArrayOps(xs: Array[Double]): ArrayOps[Double]    = new ArrayOps.ofDouble(xs)
-  implicit def floatArrayOps(xs: Array[Float]): ArrayOps[Float]       = new ArrayOps.ofFloat(xs)
-  implicit def intArrayOps(xs: Array[Int]): ArrayOps[Int]             = new ArrayOps.ofInt(xs)
-  implicit def longArrayOps(xs: Array[Long]): ArrayOps[Long]          = new ArrayOps.ofLong(xs)
-  implicit def refArrayOps[T <: AnyRef](xs: Array[T]): ArrayOps[T]    = new ArrayOps.ofRef[T](xs)
-  implicit def shortArrayOps(xs: Array[Short]): ArrayOps[Short]       = new ArrayOps.ofShort(xs)
-  implicit def unitArrayOps(xs: Array[Unit]): ArrayOps[Unit]          = new ArrayOps.ofUnit(xs)
+  // TODO: when we remove, these should we drop the underscores from the new generation below? (For source compatibility in case someone was shadowing these.)
+  @deprecated("For binary compatibility only. Release new partest and remove in M3.", "2.12.0-M2") def booleanArrayOps(xs: Array[Boolean]): ArrayOps[Boolean] = new ArrayOps.ofBoolean(xs)
+  @deprecated("For binary compatibility only. Release new partest and remove in M3.", "2.12.0-M2") def byteArrayOps(xs: Array[Byte]): ArrayOps[Byte]          = new ArrayOps.ofByte(xs)
+  @deprecated("For binary compatibility only. Release new partest and remove in M3.", "2.12.0-M2") def charArrayOps(xs: Array[Char]): ArrayOps[Char]          = new ArrayOps.ofChar(xs)
+  @deprecated("For binary compatibility only. Release new partest and remove in M3.", "2.12.0-M2") def doubleArrayOps(xs: Array[Double]): ArrayOps[Double]    = new ArrayOps.ofDouble(xs)
+  @deprecated("For binary compatibility only. Release new partest and remove in M3.", "2.12.0-M2") def floatArrayOps(xs: Array[Float]): ArrayOps[Float]       = new ArrayOps.ofFloat(xs)
+  @deprecated("For binary compatibility only. Release new partest and remove in M3.", "2.12.0-M2") def intArrayOps(xs: Array[Int]): ArrayOps[Int]             = new ArrayOps.ofInt(xs)
+  @deprecated("For binary compatibility only. Release new partest and remove in M3.", "2.12.0-M2") def longArrayOps(xs: Array[Long]): ArrayOps[Long]          = new ArrayOps.ofLong(xs)
+  @deprecated("For binary compatibility only. Release new partest and remove in M3.", "2.12.0-M2") def refArrayOps[T <: AnyRef](xs: Array[T]): ArrayOps[T]    = new ArrayOps.ofRef[T](xs)
+  @deprecated("For binary compatibility only. Release new partest and remove in M3.", "2.12.0-M2") def shortArrayOps(xs: Array[Short]): ArrayOps[Short]       = new ArrayOps.ofShort(xs)
+  @deprecated("For binary compatibility only. Release new partest and remove in M3.", "2.12.0-M2") def unitArrayOps(xs: Array[Unit]): ArrayOps[Unit]          = new ArrayOps.ofUnit(xs)
+
+  implicit def _booleanArrayOps(xs: Array[Boolean]): ArrayOps.ofBoolean   = new ArrayOps.ofBoolean(xs)
+  implicit def _byteArrayOps(xs: Array[Byte]): ArrayOps.ofByte            = new ArrayOps.ofByte(xs)
+  implicit def _charArrayOps(xs: Array[Char]): ArrayOps.ofChar            = new ArrayOps.ofChar(xs)
+  implicit def _doubleArrayOps(xs: Array[Double]): ArrayOps.ofDouble      = new ArrayOps.ofDouble(xs)
+  implicit def _floatArrayOps(xs: Array[Float]): ArrayOps.ofFloat         = new ArrayOps.ofFloat(xs)
+  implicit def _intArrayOps(xs: Array[Int]): ArrayOps.ofInt               = new ArrayOps.ofInt(xs)
+  implicit def _longArrayOps(xs: Array[Long]): ArrayOps.ofLong            = new ArrayOps.ofLong(xs)
+  implicit def _refArrayOps[T <: AnyRef](xs: Array[T]): ArrayOps.ofRef[T] = new ArrayOps.ofRef[T](xs)
+  implicit def _shortArrayOps(xs: Array[Short]): ArrayOps.ofShort         = new ArrayOps.ofShort(xs)
+  implicit def _unitArrayOps(xs: Array[Unit]): ArrayOps.ofUnit            = new ArrayOps.ofUnit(xs)
 
   // "Autoboxing" and "Autounboxing" ---------------------------------------------------
 

test/files/neg/logImplicits.check

@@ -1,4 +1,4 @@
-logImplicits.scala:2: applied implicit conversion from xs.type to ?{def size: ?} = implicit def byteArrayOps(xs: Array[Byte]): scala.collection.mutable.ArrayOps[Byte]
+logImplicits.scala:2: applied implicit conversion from xs.type to ?{def size: ?} = implicit def _byteArrayOps(xs: Array[Byte]): scala.collection.mutable.ArrayOps.ofByte
   def f(xs: Array[Byte]) = xs.size
                            ^
 logImplicits.scala:7: applied implicit conversion from String("abc") to ?{def map: ?} = implicit def augmentString(x: String): scala.collection.immutable.StringOps