Add regression test for #10047

Author: griggt

tests/run/i10047.check

@@ -0,0 +1 @@
+slash

tests/run/i10047.scala

@@ -0,0 +1,15 @@
+object wrapper {
+  val / = "slash"
+}
+
+object foo {
+  implicit val postfixOps: scala.languageFeature.postfixOps = scala.language.postfixOps
+  val / = wrapper./
+}
+
+object Test {
+  def main(args: Array[String]): Unit = {
+    val wd = foo./
+    println(wd)
+  }
+}