bugfix: inline iterator do not mess up line information anymore

tests/errmsgs/tproper_stacktrace2.nim

@@ -0,0 +1,22 @@
+discard """
+  outputsub: '''tproper_stacktrace2.nim(20) main'''
+  exitcode: 1
+"""
+
+proc returnsNil(): string = return nil
+
+iterator fields*(a, b: int): int =
+  if a == b:
+    for f in a..b:
+      yield f
+  else:
+    for f in a..b:
+      yield f
+
+proc main(): string =
+  result = ""
+  for i in fields(0, 1):
+    let x = returnsNil()
+    result &= "string literal " & $x
+
+echo main()