Fix #1167: Remove the magic from Arrays.newRefArray.

Previously, the method `Arrays.newRefArray` was one of the only 3
methods that are kept generic after erasure. This commit removes
this magic, by making it take an actual `j.l.Class[T]` as
parameter.

Moreover, the methods `newXArray` all receive an actual body,
implemented on top of Java reflection, which means that a back-end
does not *have to* special-case those methods for correctness.
It might still be required for performance, though, depending on
the back-end.

The JVM back-end is made non-optimal in this commit, precisely
because it does not specialize that method anymore. Doing so
requires modifying the fork of scalac that we use, which should
be done separately.

The JS back-end is adapted simply by doing nothing at all on any
of the newXArray methods. It will normally call the user-space
implementations which use reflection. The Scala.js optimizer will
inline and intrinsify the reflective calls, producing optimal
code, at the end of the day.

1 files changed, 0 insertions, 20 deletions

diff --git a/src/dotty/tools/backend/sjs/JSCodeGen.scala b/src/dotty/tools/backend/sjs/JSCodeGen.scala
index 70c5af1e7..401e01784 100644
--- a/src/dotty/tools/backend/sjs/JSCodeGen.scala
+++ b/src/dotty/tools/backend/sjs/JSCodeGen.scala
@@ -1036,8 +1036,6 @@ class JSCodeGen()(implicit ctx: Context) {
       genStringConcat(tree, receiver, args)
     else if (code == HASH)
       genScalaHash(tree, receiver)
-    else if (isArrayNew(code))
-      genArrayNew(tree, code)
     else if (isArrayOp(code))
       genArrayOp(tree, code)
     else if (code == SYNCHRONIZED)
@@ -1409,24 +1407,6 @@ class JSCodeGen()(implicit ctx: Context) {
         List(genExpr(receiver)))
   }
 
-  /** Gen JS code for a new array operation. */
-  private def genArrayNew(tree: Tree, code: Int): js.Tree = {
-    import scala.tools.nsc.backend.ScalaPrimitives._
-
-    implicit val pos: Position = tree.pos
-
-    val Apply(fun, args) = tree
-    val genLength = genExpr(args.head)
-
-    toIRType(tree.tpe) match {
-      case arrayType: jstpe.ArrayType =>
-        js.NewArray(arrayType, List(genLength))
-
-      case irTpe =>
-        throw new FatalError(s"ArrayNew $tree must have an array type but was $irTpe")
-    }
-  }
-
   /** Gen JS code for an array operation (get, set or length) */
   private def genArrayOp(tree: Tree, code: Int): js.Tree = {
     import scala.tools.nsc.backend.ScalaPrimitives._