[backport] Fix unsafe array opt. / opt. primitive Array(...)

SI-6611, SI-6247 (partial fix)

The original commits on master were a bit circuitous, this
is squashed to a neat little package.

I had to add type arguments to the Array.apply calls in the
test case, they are inferred on master.

commit 41ff05dfdbcf032157b3509ace633f2e7a12295c
Author: Jason Zaugg <jzaugg@gmail.com>
Date:   Sun Nov 4 14:44:59 2012 +0100

    Refactor guards checking for a particular overload of Array.apply.
    (cherry picked from commit 092345a24c22a821204fb358d33272ae8f7353be)

commit 1e5c942deccaf64f8d57bd8891b912381d7f220a
Author: Jason Zaugg <jzaugg@gmail.com>
Date:   Sun Nov 4 14:17:25 2012 +0100

    Expand optimization of Array(e1, ..., en) to primitive arrays.
    (cherry picked from commit 8265175ecc42293997d59049f430396c77a2b891)

commit ab1bf77e39f2dfeacf3fc107ccb2907a1867f04c
Author: Jason Zaugg <jzaugg@gmail.com>
Date:   Sat Nov 3 13:34:20 2012 +0100

    SI-6611 Tighten up an unsafe array optimization

    The net was cast too wide and was unsafely optimizing away array
    copies.
    (cherry picked from commit dad886659faca4fba2d4937c9bc6780591b02c27)

And also:

Optimize primitive Array(e1, ..., en)

Expands an existing optimization for reference arrays to
apply to primitives, as well.

Fixes one aspect of SI-6247.
(cherry picked from commit cac5a08611f9511ba4d94b99db630404efae190a)

Conflicts:
	src/compiler/scala/tools/nsc/transform/CleanUp.scala

More principled tree copying.

Canonical > home-spun.

Conflicts:
	src/compiler/scala/tools/nsc/transform/CleanUp.scala

1 files changed, 11 insertions, 8 deletions

diff --git a/src/compiler/scala/tools/nsc/transform/CleanUp.scala b/src/compiler/scala/tools/nsc/transform/CleanUp.scala
index 0c9cb31d58..a6ea45d8b4 100644
--- a/src/compiler/scala/tools/nsc/transform/CleanUp.scala
+++ b/src/compiler/scala/tools/nsc/transform/CleanUp.scala
@@ -15,6 +15,7 @@ abstract class CleanUp extends Transform with ast.TreeDSL {
   import global._
   import definitions._
   import CODE._
+  import treeInfo.StripCast
 
   /** the following two members override abstract members in Transform */
   val phaseName: String = "cleanup"
@@ -606,14 +607,16 @@ abstract class CleanUp extends Transform with ast.TreeDSL {
         }
         transformApply
 
-      // This transform replaces Array(Predef.wrapArray(Array(...)), <tag>)
-      // with just Array(...)
-      case Apply(appMeth, List(Apply(wrapRefArrayMeth, List(array)), _))
-      if (wrapRefArrayMeth.symbol == Predef_wrapRefArray &&
-          appMeth.symbol == ArrayModule_overloadedApply.suchThat {
-            _.tpe.resultType.dealias.typeSymbol == ObjectClass
-          }) =>
-        super.transform(array)
+      // Replaces `Array(Predef.wrapArray(ArrayValue(...).$asInstanceOf[...]), <tag>)`
+      // with just `ArrayValue(...).$asInstanceOf[...]`
+      //
+      // See SI-6611; we must *only* do this for literal vararg arrays.
+      case Apply(appMeth, List(Apply(wrapRefArrayMeth, List(arg @ StripCast(ArrayValue(_, _)))), _))
+      if wrapRefArrayMeth.symbol == Predef_wrapRefArray && appMeth.symbol == ArrayModule_genericApply =>
+        super.transform(arg)
+      case Apply(appMeth, List(elem0, Apply(wrapArrayMeth, List(rest @ ArrayValue(elemtpt, _)))))
+      if wrapArrayMeth.symbol == Predef_wrapArray(elemtpt.tpe) && appMeth.symbol == ArrayModule_apply(elemtpt.tpe) =>
+        super.transform(treeCopy.ArrayValue(rest, rest.elemtpt, elem0 :: rest.elems))
 
       case _ =>
         super.transform(tree)