[commit: ghc] master: More informative pretty-printing for phantom coercions (83b96a4)

[git at git.haskell.org]

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

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/83b96a47a5f859729a2e48efcbc10211fbf0435d/ghc

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

commit 83b96a47a5f859729a2e48efcbc10211fbf0435d
Author: Simon Peyton Jones <simonpj at microsoft.com>
Date:   Tue Jan 2 17:07:33 2018 +0000

    More informative pretty-printing for phantom coercions


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

83b96a47a5f859729a2e48efcbc10211fbf0435d
 compiler/iface/IfaceType.hs | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/compiler/iface/IfaceType.hs b/compiler/iface/IfaceType.hs
index c5a4a3d..62b33cd 100644
--- a/compiler/iface/IfaceType.hs
+++ b/compiler/iface/IfaceType.hs
@@ -1083,8 +1083,10 @@ ppr_co ctxt_prec (IfaceUnivCo IfaceUnsafeCoerceProv r ty1 ty2)
     text "UnsafeCo" <+> ppr r <+>
     pprParendIfaceType ty1 <+> pprParendIfaceType ty2
 
-ppr_co _ (IfaceUnivCo _ _ ty1 ty2)
-  = angleBrackets ( ppr ty1 <> comma <+> ppr ty2 )
+ppr_co _ (IfaceUnivCo prov role ty1 ty2)
+  = text "Univ" <> (parens $
+      sep [ ppr role <+> pprIfaceUnivCoProv prov
+          , dcolon <+>  ppr ty1 <> comma <+> ppr ty2 ])
 
 ppr_co ctxt_prec (IfaceInstCo co ty)
   = maybeParen ctxt_prec TyConPrec $
@@ -1124,6 +1126,17 @@ ppr_role r = underscore <> pp_role
                     Representational -> char 'R'
                     Phantom          -> char 'P'
 
+------------------
+pprIfaceUnivCoProv :: IfaceUnivCoProv -> SDoc
+pprIfaceUnivCoProv IfaceUnsafeCoerceProv
+  = text "unsafe"
+pprIfaceUnivCoProv (IfacePhantomProv co)
+  = text "phantom" <+> pprParendIfaceCoercion co
+pprIfaceUnivCoProv (IfaceProofIrrelProv co)
+  = text "irrel" <+> pprParendIfaceCoercion co
+pprIfaceUnivCoProv (IfacePluginProv s)
+  = text "plugin" <+> doubleQuotes (text s)
+
 -------------------
 instance Outputable IfaceTyCon where
   ppr tc = pprPromotionQuote tc <> ppr (ifaceTyConName tc)