Add regression test for #7897

Author: nicolasstucki

tests/run-staging/i7897.scala

@@ -0,0 +1,14 @@
+import scala.quoted._, staging._
+
+given Toolbox = Toolbox.make(getClass.getClassLoader)
+
+val f: Array[Int] => Int = run {
+  val stagedSum: Expr[Array[Int] => Int] = '{ (arr: Array[Int]) => 6 }
+  println(stagedSum.show)
+  stagedSum
+}
+
+@main
+def Test = {
+  f.apply(Array(1, 2, 3)) // Returns 6
+}