Possible feature: Strictness annotations

[unhammer]

With

ghc --show-iface Foo.hi|grep -C10 Strictness:

you can see the demand analysis(?) for each function, cf. https://ghc.gitlab.haskell.org/ghc/doc/users_guide/using-optimisation.html?highlight=demand#ghc-flag--fstrictness According to https://ghc.readthedocs.io/en/latest/sooner.html#faster-producing-a-program-that-runs-quicker (“How do I find out a function’s strictness?”) this info is useful for debugging performance issues as well as allegedly being fun to look at.

Could/should haskell-language-server be able to show strictness annotations? I imagine it might be useful to be able to see such strictness hints some times (when the user requests it), perhaps displayed similar types in a little popup/overlay.

(No reproduction steps for this issue since it's just a feature idea discussion, moved from https://old.reddit.com/r/haskell/comments/nz5hym/ann_haskelllanguageserver120_has_been_released/h1qamg9/ )

[jneira]

Thanks for the feature request, i think add diagnostics about performance like this could be useful for intermmediate/advanced haskellers

[michaelpj]

Related: #2529