simplify: no distinction between generic types and 'normal' types.

lib/structures/enum.js

@@ -11,7 +11,7 @@ const eatParameters = (numParams, result) => {
 
 export const makeMatchFn = variants => {
   if (variants.length === 0) {
-    return undefined;
+    throw new Error("Bottom!");
   }
   const [_, ...remainingVariants] = variants;
   return sum => handler => {
@@ -34,4 +34,4 @@ export const makeConstructors = variants => {
     ...makeConstructors(remainingVariants).map(ctor =>
       ({[ctor.name]: val => newRight(ctor(val))}[ctor.name])),
   ];
-}
+};