tree a6fe3a78919574366a72a8783a8c1c1bdc79b7d8
parent dfb4926d3783411da406da73ce8fcbf8fc5315bc
author Googler <noreply@google.com> 1561953200 -0700
committer Copybara-Service <copybara-worker@google.com> 1561953258 -0700

bazel syntax: don't use exceptions for control flow

Previously, break, continue, and return were implemented by
throwing and catching exceptions.

Now, the Eval.exec methods return a token to indicate the
continuation: one of PASS, BREAK, CONTINUE, or RETURN.
In addition, the return value is saved in the Eval,
which is good for only one function invocation.

This is simpler (and slightly more efficient).

Also:
- FlowStatement now includes PASS too; PassStatement is gone.
- ReturnException is gone, plus one EvalException constructor.
PiperOrigin-RevId: 255882194