[Feature request] Type sigs on class plugin

[googleson78]

Would it be possible to look at the current source file, and if InstanceSigs is enabled, also add type signatures to the methods that the "Add placeholders" action generates?

I would add this too, but I don't know

• how to get the type information
• how to get "currently enabled extensions" (if it's possible to do so)

[Ailrun]

For 1., I believe the current plugin already uses type information of instantiated class.

[jneira]

For 2, you can take a look to the hlint plugin, there we are querying the actual extensions used by a module

[ndmitchell]

Alternative design would be to always show the signatures (they can be quite helpful) and if someone clicks on the hyperlink and InstanceSigs aren't enabled you insert it too.

[googleson78]

Which "hyperlink" are you referring to? (using vim, so I'm not too sure about what gets shown in vscode and the like..)

Right now there's

• a diagnostic message mentioning the unimplemented method
• a code action associated with the instance declaration, where it inserts the method

Where could the signatures be? I can think of having a code lens on the method, like there currently is for top level declarations with no types, which you can trigger to add the type.

[googleson78]

As far as I can tell, the only information I have available regarding class methods is their names (and whether they have default definitions).

I guess this needs to get fetched in a similar way to how the Tactics plugin fetches type info.

[googleson78]

Their approach won't work here, since they're interested in getting bindings, not the type of an arbitrary identifier.

Perhaps something like requesting a typecheck and/or a ghc session and looking in there might work..

[Ailrun]

@googleson78 We already request a typecheck and ghc session in the action part of the plugin, so I believe you can reuse those if you need them (and create type info in the action part instead of the command part).

[July541]

Hello @googleson78, do you still work on this? I'll pick this if you don't have more plan on it.

[googleson78]

Go ahead and pick it up, I'd completely forgotten it 😅 Sorry!

[michaelpj]

My $0.02 on design would be:

• Always show the type signature in a code lens (like we do for normal bindings without type signatures)
• If the user clicks it and InstanceSigs isn't enabled, add it.
• Also provide a code action to add the signature, this can make automation easier.

[July541]

Very handy 😉

codelens.mp4