Make rule printing wobble less

a) When generating specialisations, include the types in the name
   of the rule, to avoid having rules with duplicate names.
   (The rule name is used to put rules in canonical order for
   fingerprinting.)

b) In Specialise and SpecConstr use a new function Rules.pprRulesForUser
   to print rules in canonical order.  This reduces unnecessary wobbling
   in test output, notably in T2486

1 files changed, 17 insertions, 2 deletions

diff --git a/compiler/specialise/Rules.lhs b/compiler/specialise/Rules.lhs
index 0303833726..66442ebb55 100644
--- a/compiler/specialise/Rules.lhs
+++ b/compiler/specialise/Rules.lhs
@@ -29,7 +29,7 @@ module Rules (
 	addIdSpecialisations, 
 	
 	-- * Misc. CoreRule helpers
-        rulesOfBinds,
+        rulesOfBinds, pprRulesForUser,
         
         lookupRule, mkLocalRule, roughTopNames
     ) where
@@ -152,6 +152,22 @@ ruleCantMatch (t       : ts) (a       : as) = ruleCantMatch ts as
 ruleCantMatch ts	     as		    = False
 \end{code}
 
+\begin{code}
+pprRulesForUser :: [CoreRule] -> SDoc
+-- (a) tidy the rules
+-- (b) sort them into order based on the rule name
+-- (c) suppress uniques (unless -dppr-debug is on)
+-- This combination makes the output stable so we can use in testing
+-- It's here rather than in PprCore because it calls tidyRules
+pprRulesForUser rules
+  = withPprStyle defaultUserStyle $
+    pprRules $
+    sortLe le_rule  $
+    tidyRules emptyTidyEnv rules
+  where 
+    le_rule r1 r2 = ru_name r1 <= ru_name r2
+\end{code}
+
 
 %************************************************************************
 %*									*
@@ -168,7 +184,6 @@ mkSpecInfo rules = SpecInfo rules (rulesFreeVars rules)
 extendSpecInfo :: SpecInfo -> [CoreRule] -> SpecInfo
 extendSpecInfo (SpecInfo rs1 fvs1) rs2
   = SpecInfo (rs2 ++ rs1) (rulesFreeVars rs2 `unionVarSet` fvs1)
-
 addSpecInfo :: SpecInfo -> SpecInfo -> SpecInfo
 addSpecInfo (SpecInfo rs1 fvs1) (SpecInfo rs2 fvs2) 
   = SpecInfo (rs1 ++ rs2) (fvs1 `unionVarSet` fvs2)