I'm unfamiliar with claudish and the example helped show the problem. But! There was something uncomfortably familiar in the Claudish example -- this is the way human programmers write when they're deep in the weedy details, and writing the changelist description afterwards as if coming up for air. Overuse of parentheses in nested lists especially, as if the English text needs to bend to the strict needs of a C++ parser.

The rewrite did seem to lose the important fact about the ensure- pattern being idempotent.