COMPLETE pragmas

[Richard Eisenberg]

Hi Sebastian,

I enjoyed your presentation last week at ICFP!

This thread (https://ghc-devs.haskell.narkive.com/NXBBDXg1/suppressing-false-incomplete-pattern-matching-warnings-for-polymorphic-pattern-synonyms) played out before you became so interested in pattern-match coverage. I'd be curious for your thoughts there -- do you agree with the conclusions in the thread?

My motivation for asking is https://github.com/conal/linalg/pull/54 (you don't need to read the whole thing), which can be boiled down to a request for a COMPLETE pragma that works at a polymorphic result type. (Or a COMPLETE pragma written in a module that is not the defining module for a pattern synonym.) https://gitlab.haskell.org/ghc/ghc/-/issues/14422 describes a similar, but even more challenging scenario.

Do you see any ways forward here?

Thanks!
Richard