[commit: ghc] wip/T9732: Update documentation of matcher type (bbbd75c)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : wip/T9732
Link       : http://ghc.haskell.org/trac/ghc/changeset/bbbd75c6b7d26c04c00daecc5dfe63736aedf88c/ghc

>---------------------------------------------------------------

commit bbbd75c6b7d26c04c00daecc5dfe63736aedf88c
Author: Dr. ERDI Gergo <gergo at erdi.hu>
Date:   Thu Nov 6 20:31:03 2014 +0800

    Update documentation of matcher type


>---------------------------------------------------------------

bbbd75c6b7d26c04c00daecc5dfe63736aedf88c
 compiler/basicTypes/PatSyn.lhs | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/compiler/basicTypes/PatSyn.lhs b/compiler/basicTypes/PatSyn.lhs
index 9efd69d..af77d36 100644
--- a/compiler/basicTypes/PatSyn.lhs
+++ b/compiler/basicTypes/PatSyn.lhs
@@ -130,11 +130,19 @@ data PatSyn
 
         -- See Note [Matchers and wrappers for pattern synonyms]
         psMatcher     :: Id,
-             -- Matcher function, of type
-             --   forall r univ_tvs. req_theta
-             --                   => res_ty
-             --                   -> (forall ex_tvs. prov_theta -> arg_tys -> r)
-             --                   -> r -> r
+            -- Matcher function. If psArgs is empty, then it has type
+             --   forall (r :: ?) univ_tvs. req_theta
+             --                       => res_ty
+             --                       -> (forall ex_tvs. prov_theta -> Void# -> r)
+             --                       -> (Void# -> r)
+             --                       -> r
+             --
+             -- Otherwise:
+             --   forall (r :: ?) univ_tvs. req_theta
+             --                       => res_ty
+             --                       -> (forall ex_tvs. prov_theta -> arg_tys -> r)
+             --                       -> (Void# -> r)
+             --                       -> r
 
         psWrapper     :: Maybe Id
              -- Nothing  => uni-directional pattern synonym