SI-7521 Fix erasure of parametric value classes.

`Erasure.boxingErasure` exists to ensure that we use boxed primitives
to represent the value, if the value class has type parameters
referred to by its element type.

However, this is implenented with a type map that runs deeply
across the type. In the enclosed test case, we have
`Repr=Array[Int]`, which should be erased to `Array[Int]`, _not_
to `Array[Integer]`.

This commit ensures that the `boxingErasure` map only applies
boxing at the top level, and not within array arguments. (Other
type arguments will be erased, so we don't have to deal with them.)

1 files changed, 20 insertions, 0 deletions

diff --git a/test/files/run/t7521b.scala b/test/files/run/t7521b.scala
new file mode 100644
index 0000000000..c9e27f28b4
--- /dev/null
+++ b/test/files/run/t7521b.scala
@@ -0,0 +1,20 @@
+class Wrapper[X](x: X)
+
+class C {
+  def a(w: Wrapper[Array[Int]]) = 0
+  def b(w: Wrapper[Int]) = 0
+}
+
+object Test {
+  def main(args: Array[String]): Unit = {
+    val c = new C
+    c.a(new Wrapper(Array(1, 2)))
+    c.b(new Wrapper(1))
+
+    val methods = classOf[C].getDeclaredMethods.sortBy(_.getName)
+    println("= Java Erased Signatures =")
+    println(methods.mkString("\n"))
+    println("\n= Java Generic Signatures =")
+    println(methods.map(_.toGenericString).mkString("\n"))
+  }
+}