[fine] Parse is expression, partially

fine/tests/expression/alternates.fine

@@ -33,7 +33,7 @@ class Monster {
 fun print(x:string) {}
 
 fun in_range(weapon: MeleeWeapon or RangedWeapon, distance: f64) {
-  weapon match {
+  match weapon {
     w:RangedWeapon -> distance >= w.minRange and distance <= w.maxRange,
     _ -> distance == 1
   }