Allow putting SCC annotations on class instance methods

Perhaps there's a way to do this that I don't know about.

Here's a file:

module Test where                                   

class C a where                                     
  foo :: a -> String                                

instance C Int where                                
  -- this would be a parse error: {-# SCC foo #-}   
  foo a = show a                                    

I want to put a cost center on foo. Like mentioned in the comment, doing that in the obvious way is a parse error.

Interestingly -fprof-auto-top puts a cost center on foo.

This came up when debugging #14637.

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Trac field	Value
Version
Type	FeatureRequest
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Profiling
Test case
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changed weight to 5

added Tfeature request Trac import profiling labels

Do you not get the same effect with -fprof-auto-top if you do foo a = {-# SCC foo #-} show a?

I'm also a bit surprised that -fprof-auto-top adds a SCC to this foo. Apparently typeclass methods are considered as top level.

Do you not get the same effect with -fprof-auto-top if you do foo a = {-# SCC foo #-} show a?

Yes, that works, but if foo does pattern matching on the parameters, you need to put multiple SCCs or refactor the code.

You can also make fooHelper that's a top level function and just foo = fooHelper.

Right.. I made some progress on supporting SCCs in more places some time ago: https://github.com/ghc/ghc/commit/98b2c508 it shouldn't be too hard to make it possible to use in this context.

added Pnormal label