Improve generated `GHC.Prim` docs

Summary:
* Extended `genprimcode` to generate Haddock-compatible deprecations,
  as well as displaying information about which functions are LLVM-only
  and which functions can fail with an unchecked exception.

* Ported existing deprecations to the new format, and also added a
  deprecation on `par#` (see Trac #15227).

* Emit an error on fixity/deprecation of builtins, unless we are
  processing the module in which that name is defined (see Trac #15233).
  That means the following is no longer accepted (outside of `GHC.Types`):

```
infixr 7 :
{-# DEPRECATED (:) "cons is deprecated" #-}
```

* Generate `data (->) a b` with docs and fixity in `GHC.Prim`. This
  means: GHC can now parse `data (->) a b` and `infixr 0 ->` (only in
  `GHC.Prim`) and `genprimcode` can digest `primtype (->) a b` (See Trac
  #4861)

as well as some misc fixes along the way.

Reviewers: bgamari, RyanGlScott

Reviewed By: RyanGlScott

Subscribers: RyanGlScott, rwbarton, mpickering, carter

GHC Trac Issues: #15227, #15233, #4861

Differential Revision: https://phabricator.haskell.org/D5167

1 files changed, 1 insertions, 0 deletions

diff --git a/compiler/parser/Parser.y b/compiler/parser/Parser.y
index adfbf2c332..8789c9b333 100644
--- a/compiler/parser/Parser.y
+++ b/compiler/parser/Parser.y
@@ -3238,6 +3238,7 @@ tyconsym :: { Located RdrName }
 op      :: { Located RdrName }   -- used in infix decls
         : varop                 { $1 }
         | conop                 { $1 }
+        | '->'                  { sL1 $1 $ getRdrName funTyCon }
 
 varop   :: { Located RdrName }
         : varsym                { $1 }