Support union of parameters in functions in Effect.Tag.Proxy type

.changeset/four-items-itch.md

@@ -0,0 +1,5 @@
+---
+"effect": patch
+---
+
+Support union of parameters in functions in `Effect.Tag.Proxy` type

packages/effect/src/Effect.ts

@@ -6497,14 +6497,19 @@ export declare namespace Tag {
    */
   export type Proxy<Self, Type> = {
     [
-      k in keyof Type as Type[k] extends ((...args: [...infer Args]) => infer Ret) ?
+      k in keyof Type as Type[k] extends ((...args: infer Args extends ReadonlyArray<any>) => infer Ret) ?
         ((...args: Readonly<Args>) => Ret) extends Type[k] ? k : never
         : k
-    ]: Type[k] extends (...args: [...infer Args]) => Effect<infer A, infer E, infer R> ?
+    ]: Type[k] extends (...args: infer Args extends ReadonlyArray<any>) => Effect<infer A, infer E, infer R> ?
       (...args: Readonly<Args>) => Effect<A, E, Self | R>
-      : Type[k] extends (...args: [...infer Args]) => infer A ? (...args: Readonly<Args>) => Effect<A, never, Self>
+      : Type[k] extends (...args: infer Args extends ReadonlyArray<any>) => infer A ?
+        (...args: Readonly<Args>) => Effect<A, never, Self>
       : Type[k] extends Effect<infer A, infer E, infer R> ? Effect<A, E, Self | R>
-      : Effect<Type[k], never, Self>
+      : Effect<
+        Type[k] extends (...args: infer Args extends ReadonlyArray<any>) => any ? [Type[k], Args] : [Type[k], "no"],
+        never,
+        Self
+      >
   }
 }
 

packages/effect/test/Effect/environment.test.ts

@@ -27,6 +27,9 @@ class DemoTag extends Effect.Tag("DemoTag")<DemoTag, {
   readonly getNumbers: () => Array<number>
   readonly strings: Array<string>
   readonly fn: (...args: ReadonlyArray<string>) => Array<string>
+  readonly fnParamsUnion: (
+    ...args: ReadonlyArray<string> | [number] | [false, true]
+  ) => ReadonlyArray<string> | [number] | [false, true]
   readonly fnGen: <S>(s: S) => Array<S>
 }>() {
 }
@@ -69,28 +72,32 @@ describe("Effect", () => {
         getNumbers: () => [0, 1],
         strings: ["a", "b"],
         fn: (...args) => Array.from(args),
-        fnGen: (s) => [s]
+        fnGen: (s) => [s],
+        fnParamsUnion: (..._args) => _args
       })))
   })
   it.effect("effect tag", () =>
     Effect.gen(function*($) {
-      const [n, s, z] = yield* $(Effect.all([
+      const [n, s, z, zUnion] = yield* $(Effect.all([
         DemoTag.getNumbers(),
         DemoTag.strings,
-        DemoTag.fn("a", "b", "c")
+        DemoTag.fn("a", "b", "c"),
+        DemoTag.fnParamsUnion(1)
       ]))
       const s2 = yield* $(DemoTag.pipe(Effect.map((_) => _.strings)))
       const s3 = yield* $(DemoTag.use((_) => _.fnGen("hello")))
       expect(n).toEqual([0, 1])
       expect(s).toEqual(["a", "b"])
       expect(z).toEqual(["a", "b", "c"])
+      expect(zUnion).toEqual([1])
       expect(s2).toEqual(["a", "b"])
       expect(s3).toEqual(["hello"])
     }).pipe(Effect.provideService(DemoTag, {
       getNumbers: () => [0, 1],
       strings: ["a", "b"],
       fn: (...args) => Array.from(args),
-      fnGen: (s) => [s]
+      fnGen: (s) => [s],
+      fnParamsUnion: (..._args) => _args
     })))
   it.effect("effect tag with primitives", () =>
     Effect.gen(function*($) {