Improve show of ScheduleMod

Author: jasagredo

io-sim/CHANGELOG.md

@@ -5,6 +5,8 @@
 - Support `threadLabel` (`io-classes-1.8`)
 - `IOSimPOR`'s `Effect` traces now will correctly show labels on read/written
   `TVars`.
+- `Show` instance for `ScheduleMod` now prints `ThreadId`s in a slightly nicer
+  way, matching the way those steps would be traced in the `SimTrace`.
 
 ## 1.6.0.0
 

io-sim/src/Control/Monad/IOSimPOR/Types.hs

@@ -171,11 +171,12 @@ instance Show ScheduleMod where
   showsPrec d (ScheduleMod tgt ctrl insertion) =
     showParen (d>10) $
       showString "ScheduleMod " .
-      showsPrec 11 tgt .
+      showParen True (showString (ppStepId tgt)) .
       showString " " .
       showsPrec 11 ctrl .
-      showString " " .
-      showsPrec 11 insertion
+      showString " [" .
+      showString (List.intercalate "," (map ppStepId insertion)) .
+      showString "]"
 
 --
 -- Steps