message: Position existence need not be consistent
diff: @@ -124,10 +124,11 @@ It also has the optional `args`, `funcs`, and `labels` fields.
  Source Positions
  ----------------
  -All syntax objects can optionally have a `pos` field to reflect a source position:
  +Any syntax object may optionally have a `pos` field to reflect a source position:
  { ..., "pos": {"row": <int>, "col": <int>} }
  The `pos` object has two keys: `row` (the line number) and `col` (the column number within the line).
  -Front-end compilers that generate Bril code may add this information to help with debugging, but tools can't require it to exist (or to follow any specific rules).
  +Front-end compilers that generate Bril code may add this information to help with debugging.
  The [text format parser](../tools/text.md), for example, can optionally add source positions.
  +However, tools can't require positions to exist, to consistently exist or not on all syntax objects in a program, or to follow any particular rules.
  