Tell ghc which pragmas to recognize

Motivation

hlint can use HLINT pragmas (or optionally, ANN pragmas, altho these result in the same recompilation rules as TH and so I prefer to avoid them) to control its behaviour on a case-by-case basis. Of course, these are not recognized by ghc, and so using them requires you to disable -Wunrecognised-pragmas if you wish to compile without warnings.

Unfortunately, this leaves you open to the possibility of error, e.g. typos in non-ghc pragma names. In short, it’s broader than I want—I don’t want ghc to ignore all unrecognized pragmas, just HLINT pragmas.

Proposal

I would therefore like to be able to tell ghc that it should recognize these HLINT pragmas with a flag along the lines of -frecognize-pragma=HLINT.

With this flag enabled in a module, you could leave -Wunrecognised-pragmas enabled, and use {-# HLINT … #-} without warnings.

At the same time, a typo like {-# HILNT … #-} would result in a warning, meaning that ghc can give you limited verification of other tools’ pragmas for you.