Add missing primop documentation (#18454)

- Add three pseudoops to primops.txt.pp, so that Haddock renders
  the documentation
- Update comments
- Remove special case for "->" - it's no longer exported from GHC.Prim
- Remove reference to Note [Compiling GHC.Prim] - the ad-hoc fix is no
  longer there after updates to levity polymorphism.
- Document GHC.Prim
- Remove the comment that lazy is levity-polymorphic.
  As far as I can tell, it never was: in 80e399639,
  only the unfolding was given an open type variable.
- Remove haddock hack in GHC.Magic - no longer neccessary after
  adding realWorld# to primops.txt.pp.

1 files changed, 2 insertions, 15 deletions

diff --git a/libraries/ghc-prim/GHC/Magic.hs b/libraries/ghc-prim/GHC/Magic.hs
index d1f2650a96..cd9474271d 100644
--- a/libraries/ghc-prim/GHC/Magic.hs
+++ b/libraries/ghc-prim/GHC/Magic.hs
@@ -1,8 +1,6 @@
-{-# LANGUAGE CPP #-}
 {-# LANGUAGE Trustworthy #-}
 {-# LANGUAGE NoImplicitPrelude #-}
 {-# LANGUAGE MagicHash #-}
-{-# LANGUAGE UnboxedTuples #-}
 {-# LANGUAGE DataKinds #-}
 {-# LANGUAGE PolyKinds #-}
 {-# LANGUAGE ScopedTypeVariables #-}
@@ -32,13 +30,8 @@ module GHC.Magic ( inline, noinline, lazy, oneShot, runRW# ) where
 
 -- Here import TYPE explicitly from GHC.Types and not from GHC.Prim. This is
 -- because TYPE is not exported by the source Haskell module generated by
--- genprimops which Haddock will typecheck.
--- Likewise, realWorld# is not generated by genprimops so we use CPP and only
--- import/use it when not building haddock docs.
-#if !defined(__HADDOCK_VERSION__)
-import GHC.Prim (realWorld#)
-#endif
-import GHC.Prim (State#, RealWorld)
+-- genprimops which Haddock will typecheck (#15935).
+import GHC.Prim (State#, realWorld#, RealWorld)
 import GHC.Types (RuntimeRep, TYPE)
 
 -- | The call @inline f@ arranges that @f@ is inlined, regardless of
@@ -83,8 +76,6 @@ noinline x = x
 --
 -- If 'lazy' were not lazy, 'Control.Parallel.par' would look strict in
 -- @y@ which would defeat the whole purpose of 'Control.Parallel.par'.
---
--- Like 'seq', the argument of 'lazy' can have an unboxed type.
 lazy :: a -> a
 lazy x = x
 -- Implementation note: its strictness and unfolding are over-ridden
@@ -124,8 +115,4 @@ runRW# :: forall (r :: RuntimeRep) (o :: TYPE r).
           (State# RealWorld -> o) -> o
 -- See Note [runRW magic] in GHC.CoreToStg.Prep.
 {-# NOINLINE runRW# #-}  -- runRW# is inlined manually in CorePrep
-#if !defined(__HADDOCK_VERSION__)
 runRW# m = m realWorld#
-#else
-runRW# = runRW#   -- The realWorld# is too much for haddock
-#endif