Quick action to explicitly annotate a `let` binding parameter

[cartermp]

Given code like this:

let myFunc x = x.ToString()

There should be a quick action available to convert it to this:

let myFunc (x: 'a) : string = x.ToString()

This would require some work to get the inferred types of the let-bound value(s) and each parameter if it's a function, and their ranges.

[kerams]

Where should the action pop up? With caret within the function identifier?

On a related note how are quick actions actually triggered? They don't have associated diagnostic IDs like code fixes, so does Roslyn iterate over all registered providers on every hover/caret move to see if they return anything actionable at the location?

[cartermp]

This would be added as a refactoring provider here: https://github.com/dotnet/fsharp/tree/main/vsintegration/src/FSharp.Editor/Refactor

[cartermp]

Refactoring Providers and quick fixes are different. The former is run periodically in the editor and whenever one is applicable it is triggered to run asynchronously. The latter are triggered based off of diagnostics.

[psfinaki]

refactoring.mp4

So this is half-there - works for parameters but not return types. Keeping the ticket, created a separate area for this to distinguish it from code fixes.