Add regression test for issue #15715

[Cherry-picked 0ff35b1]

Author: jchyb

tests/pos/i15715.scala

@@ -0,0 +1,7 @@
+import scala.quoted.*
+
+def macroImpl(using Quotes) =
+  val expr = Expr(1)
+  Some((1, 2)).map { (x, y) =>
+    '{ ${expr} + 1 }
+  }