something between try-completion and test-completion?

[Drew Adams]

I'd be interested in a function similar to both `try-completion' and
`test-completion', but which would just test whether its STRING arg can be
completed against its COLLECTION arg, respecting its PREDICATE arg.

It would be like `test-completion', in that as soon as some match is found
it would return non-nil, not bothering to test the other completions and
calculate the common prefix.

It would be like `try-completion', in that it would test whether the STRING
is a prefix of some COLLECTION element, not whether STRING is itself one of
the COLLECTION elements.

The idea is to have a quick version of `try-completion' for situations where
the common prefix of all matches is not needed, and all you want is an
indication of whether the STRING could be completed.

Any other interest in this? Any chance this will become available?