Avoid redundant work in diagnostics pass

[pepeiborra]

The diagnostics pass is at least O(FRlog(F)) in the number of Files and Rules. While there's no obvious way to improve the asymptotic, we can avoid some wasted work by skipping rules that never produce diagnostics, like GetDependencyInformation.

Turns out that there are quite a few such rules, so the strategy pays off in large projects.

[ndmitchell]

Is there any way to encode this statically? E.g. add:

defineNoDiagnostics
    :: IdeRule k v
    => (k -> NormalizedFilePath -> Action v) -> Rules ()

And then pass this information to the underlying super-define, so it knows which rules have no diagnostics, and if they in their type try and produce diagnostics, we get a type error?

If we are doing the more dynamic approach, I'd definitely want an error asserting that it claimed no diagnostics and there were indeed no diagnostics - otherwise we might accidentally lose a diagnostic, which would be awful.

[pepeiborra]

Is there any way to encode this statically? E.g. add:

defineNoDiagnostics
    :: IdeRule k v
    => (k -> NormalizedFilePath -> Action v) -> Rules ()

And then pass this information to the underlying super-define, so it knows which rules have no diagnostics, and if they in their type try and produce diagnostics, we get a type error?

If we are doing the more dynamic approach, I'd definitely want an error asserting that it claimed no diagnostics and there were indeed no diagnostics - otherwise we might accidentally lose a diagnostic, which would be awful.

I like that much better, thanks for the suggestion!

[ndmitchell]

Looks good!