From 1886c52ecedc95088c78b55b73d8ff951fcd95ae Mon Sep 17 00:00:00 2001
From: Pablo Baleztena <pablo@ultharsoftware.com>
Date: Tue, 15 Oct 2024 07:59:35 -0300
Subject: [PATCH] [fabric/core] Enhance VariantMatcher to support return type
 parameterization in match function

---
 packages/fabric/core/src/variant/match.ts | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/packages/fabric/core/src/variant/match.ts b/packages/fabric/core/src/variant/match.ts
index e4f6932..5d14799 100644
--- a/packages/fabric/core/src/variant/match.ts
+++ b/packages/fabric/core/src/variant/match.ts
@@ -1,17 +1,21 @@
 import { Fn } from "../types/fn.js";
 import { TaggedVariant, VariantFromTag, VariantTag } from "./variant.js";
 
-export type VariantMatcher<TVariant extends TaggedVariant<string>> = {
-  [K in TVariant[VariantTag]]: Fn<VariantFromTag<TVariant, K>>;
+export type VariantMatcher<TVariant extends TaggedVariant<string>, T> = {
+  [K in TVariant[VariantTag]]: Fn<VariantFromTag<TVariant, K>, T>;
 };
 
 export function match<const TVariant extends TaggedVariant<string>>(
   v: TVariant,
 ) {
   return {
-    case<const TMatcher extends VariantMatcher<TVariant>>(
-      cases: TMatcher,
-    ): ReturnType<TMatcher[TVariant[VariantTag]]> {
+    case<
+      const TReturnType,
+      const TMatcher extends VariantMatcher<
+        TVariant,
+        TReturnType
+      > = VariantMatcher<TVariant, TReturnType>,
+    >(cases: TMatcher): TReturnType {
       if (!(v[VariantTag] in cases)) {
         throw new Error("Non-exhaustive pattern match");
       }