As hinted at in IRC, it turned out that the FFP was erroneously dropped due to using the equivalent of i_error_clear_push rather than of i_error_push in three out of four *_branch (choice) super-instructions:

si:voidvalue_branch
si:valuevoid_branch
si:valuevalue_branch

This was fixed for the TclOO and Snit RDE (the C one was not affected, naturally). NX benefits from the TclOO fix directly, as it derives from the TclOO engine.

Branch -ffp-3ed39a451f [*] contains a fix plus test. The test is WIP, because I don't exactly know how to best instrument the test runner to cover for this failure case? Here, the combined "failure" condition would be (as signalled by parset):

- matched prefix ne input suffix ne ""
- the content of myerror with the FFP

Pls. advise.

[*]