Add regression test

Closes #17409

Author: nicolasstucki

tests/pos-macros/i17409.scala

@@ -0,0 +1,10 @@
+import scala.quoted.*
+
+transparent inline def thing =
+  ${ thingImpl }
+
+def thingImpl(using Quotes): Expr[Any] =
+  '{
+    def makeThing: { def me: this.type } = ???
+    makeThing
+  }