doBodiesStarted property

The do loops whose body has already been entered.

SCE19. The state machine re-enters a DoStatement node for two different reasons — arriving at the loop from the statement before it, and coming back from the end of its body — and it used to assume the second, evaluating the condition every time. So do { n++; } while (false); never ran its body at all. Loops whose condition is true on entry gave the right answer, which is why nothing caught it.

Membership is what tells the two arrivals apart: absent means the body has not run yet and must, present means the body has finished and the condition decides. continue deliberately leaves the entry in place — it returns to the loop from INSIDE, and Dart evaluates the condition for it (F-SCD4-13 pins that).

Keyed by IDENTITY, and load-bearing in the tom_d4rt_ast twin: SAstNode overrides == with a structural toJson() comparison, so a plain Set there would treat two identical-looking do loops as one.