Add explicit span IDs when creating ast.token().

The new generated ASDL code let us omit any constructor argument, and
then it would be None.  That should be fixed.

core/word.py

@@ -311,9 +311,10 @@ def TildeDetect(word):
      pre, post = val[:p], val[p:]
      prefix += pre
      tilde_part = ast.TildeSubPart(prefix)
      # TODO: Need a span_id here.  Or use different algorithm.
      #print('SPLITTING %s p = %d' % (word.parts[i], p), file=sys.stderr)
      remainder_part = ast.LiteralPart(ast.token(Id.Lit_Chars, post))
      # NOTE: no span_id here.  It would be nicer to use a different algorithm
      # that didn't require this.
      t = ast.token(Id.Lit_Chars, post, const.NO_INTEGER)
      remainder_part = ast.LiteralPart(t)
      found_slash = True
      break

osh/cmd_parse.py

@@ -121,9 +121,10 @@ def _MaybeReadHereDocs(self):
        h.body = word
        h.was_filled = True
      else:
        # TODO: Add span_id to token
        # Each line is a single span.
        tokens = [ast.token(Id.Lit_Chars, line) for _, line in lines]
        # Each line is a single span.  TODO: Add span_id to token.
        tokens = [
            ast.token(Id.Lit_Chars, line, const.NO_INTEGER)
            for _, line in lines]
        parts = [ast.LiteralPart(t) for t in tokens]
        h.body = ast.CompoundWord(parts)
        h.was_filled = True