Pretty print readable unicode characters (#2041)

Closes #1943

src/swarm-lang/Swarm/Language/Pretty.hs

@@ -36,6 +36,7 @@ import Swarm.Language.Syntax.Direction
 import Swarm.Language.Typecheck
 import Swarm.Language.Types
 import Swarm.Util (number, showEnum, showLowT, unsnocNE)
+import Text.Show.Unicode (ushow)
 import Witch
 
 ------------------------------------------------------------
@@ -271,7 +272,7 @@ instance PrettyPrec (Term' ty) where
     TDir d -> ppr d
     TInt n -> pretty n
     TAntiInt v -> "$int:" <> pretty v
-    TText s -> fromString (show s)
+    TText s -> fromString (ushow s)
     TAntiText v -> "$str:" <> pretty v
     TBool b -> bool "false" "true" b
     TRobot r -> "<a" <> pretty r <> ">"

swarm.cabal

@@ -191,6 +191,7 @@ library swarm-lang
     terminal-size >=0.3 && <1.0,
     text,
     text-rope >=0.2 && <0.3,
+    unicode-show >=0.1 && <0.2,
     vector,
     vty,
     witch,

test/unit/TestEval.hs

@@ -227,6 +227,9 @@ testEval g =
         , testCase
             "format function"
             ("format (\\x. x + 1)" `evaluatesTo` VText "\\x. x + 1")
+        , testCase
+            "format forall"
+            ("format \"∀\"" `evaluatesTo` VText "\"∀\"")
         , testCase
             "concat"
             ("\"x = \" ++ format (2+3) ++ \"!\"" `evaluatesTo` VText "x = 5!")
@@ -346,6 +349,7 @@ testEval g =
  where
   tquote :: String -> Text
   tquote = T.pack . show
+
   throwsError :: Text -> (Text -> Bool) -> Assertion
   throwsError tm p = do
     result <- evaluate tm