Primop types should not mention ()

I've just noticed that two primpops have types that mention tuples (see compiler/prelude/primops.txt.pp):

primop  FinalizeWeakOp "finalizeWeak#" GenPrimOp
   Weak# a -> State# RealWorld -> (# State# RealWorld, Int#,
              (State# RealWorld -> (# State# RealWorld, () #)) #)


primop  Check "check#" GenPrimOp
      (State# RealWorld -> (# State# RealWorld, a #) )
   -> (State# RealWorld -> (# State# RealWorld, () #) )

But they really really shouldn't. The unit tuple is a type defined in Haskell, and it makes an awkward cycle if the supposedly-truly-primitive primpops refer to it. (Discovered during the saga of [D757].)

Most primpops do not do this; eg

primop  WriteMutVarOp "writeMutVar#"  GenPrimOp
   MutVar# s a -> a -> State# s -> State# s

Now check# and finalizeWeak# are pretty obscure primops and I don't think anyone will mind if I fix their type signatures.

But in addition to doing that, I'll have to look at their implementations. 'But where are those implementations??' I can't find anything in the RTS.

While thinking about it

• Both come with literally zero Haddock documentation which is terrible. The type of both is pretty obscure.
• check# is a very short name for very specialised STM operation. Surely we should call it addSTMInvariant or something like that?

Trac metadata

Trac field	Value
Version	7.10.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
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CC	fryguybob
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Architecture