fixes more nil handling regressions

tests/notnil/tnotnil.nim

@@ -1,5 +1,5 @@
 discard """
-  line: 22
+  line: 13
   errormsg: "type mismatch"
 """
 {.experimental: "notnil".}
@@ -8,16 +8,6 @@ type
   TObj = object
     x: int
 
-  MyString = string not nil
-
-#var x: PObj = nil
-
-proc p(x: string not nil): int =
-  result = 45
-
-proc q(x: MyString) = discard
 proc q2(x: string) = discard
 
 q2(nil)
-q(nil)
-