Support MultiWayIf.

app/SimplifySyntax.hs

@@ -297,6 +297,7 @@ hsExpToSimpExp x = simplifyExp $ case x of
   Exts.EnumFromTo l e1 e2 -> desugarEnums l "enumFromTo" [e1, e2]
   Exts.EnumFromThen l e1 e2 -> desugarEnums l "enumFromThen" [e1, e2]
   Exts.EnumFromThenTo l e1 e2 e3 -> desugarEnums l "enumFromThenTo" [e1, e2, e3]
+  Exts.MultiIf l rhss -> SeGuard l (fmap guardedRhsToSelectorAndVal rhss)
   _ -> error $ "Unsupported syntax in hsExpToSimpExp: " ++ show x
 
 -- Parsing
@@ -306,7 +307,8 @@ customParseMode = Exts.defaultParseMode
   {Exts.extensions =
    [Exts.EnableExtension Exts.MultiParamTypeClasses,
     Exts.EnableExtension Exts.FlexibleContexts,
-    Exts.EnableExtension Exts.TupleSections
+    Exts.EnableExtension Exts.TupleSections,
+    Exts.EnableExtension Exts.MultiWayIf
    ]
   }
 

test/VisualTranslateTests.hs

@@ -280,6 +280,17 @@ dataDeclTests = [
   , "data Foo = Foo Int"
   ]
 
+multiWayIfTests :: [String]
+multiWayIfTests = [
+  "y = if | x == 0 -> 1"
+  , "y = if\n\
+  \  | x == 0 -> 1\n\
+  \  | otherwise -> 2"
+  , "y = if\n\
+  \  | x == 0 -> if {| y > z -> 2; | pizza -> 3} \n\
+  \  | otherwise -> 2"
+  ]
+
 testDecls :: [String]
 testDecls = mconcat [
   simpleTests
@@ -298,6 +309,7 @@ testDecls = mconcat [
   , otherTests
   , typeSigTests
   , dataDeclTests
+  , multiWayIfTests
   ]