avoid unnecessary variants

src/compiler/api/GF/Compile/TypeCheck/ConcreteNew.hs

@@ -501,7 +501,7 @@ resolveOverloads scope c t0 q args mb_ty = do
                       arg_tys <- mapCM (checkArg g) c1 args
                       let v_ttys = mapC (\c (t,ty) -> (t,eval g [] c ty [])) c2 ttys
                       try (\(fun,fun_ty) -> reapply2 scope c3 fun fun_ty arg_tys mb_ty)
-                          (\ttys -> fmap (\(ts,ty) -> (FV ts,ty)) (snd (minimum g ttys)))
+                          (\ttys -> fmap (\(ts,ty) -> (mkFV ts,ty)) (snd (minimum g ttys)))
                           v_ttys
   where
     checkArg g c (ImplArg arg) = do
@@ -515,6 +515,9 @@ resolveOverloads scope c t0 q args mb_ty = do
       let v = eval g (scopeEnv scope) c2 arg []
       return (arg,v,arg_ty)
 
+    mkFV [t] = t
+    mkFV ts  = FV ts
+
     minimum g []                    = (maxBound,err)
       where
         err = evalError (pp "Overload resolution failed")