matcher: simplify function protocol

src/types/InvertPattern.ts

@@ -133,9 +133,7 @@ type InvertPatternInternal<p, input> = 0 extends 1 & p
       and: ReduceIntersection<Extract<subpattern, readonly any[]>, input>;
       or: ReduceUnion<Extract<subpattern, readonly any[]>, input>;
       default: [subpattern] extends [never] ? input : subpattern;
-      custom: Override<
-        narrowFn extends Fn ? Apply<narrowFn, [input, subpattern]> : never
-      >;
+      custom: Override<narrowFn extends Fn ? Apply<narrowFn, input> : never>;
     }[matcherType]
   : p extends Primitives
   ? p
@@ -344,7 +342,7 @@ type InvertPatternForExcludeInternal<p, i, empty = never> =
         >;
         default: excluded;
         custom: excluded extends infer narrowFn extends Fn
-          ? Apply<narrowFn, [i, subpattern]>
+          ? Apply<narrowFn, i>
           : never;
       }[matcherType]
     : p extends readonly any[]

src/types/helpers.ts

@@ -278,18 +278,10 @@ export type GetKey<O, K> = O extends any
   : never;
 
 export interface Fn {
-  [rawArgs]: unknown;
-  args: this[rawArgs] extends infer args extends unknown[] ? args : never;
-  arg0: this[rawArgs] extends [infer arg, ...any] ? arg : never;
-  arg1: this[rawArgs] extends [any, infer arg, ...any] ? arg : never;
-  arg2: this[rawArgs] extends [any, any, infer arg, ...any] ? arg : never;
-  arg3: this[rawArgs] extends [any, any, any, infer arg, ...any] ? arg : never;
-  return: unknown;
+  input: unknown;
+  output: unknown;
 }
 
-export type Apply<fn extends Fn, args extends unknown[]> = (fn & {
-  [rawArgs]: args;
-})['return'];
-
-declare const rawArgs: unique symbol;
-type rawArgs = typeof rawArgs;
+export type Apply<fn extends Fn, input> = (fn & {
+  input: input;
+})['output'];

tests/matcher-protocol.test.ts

@@ -6,9 +6,9 @@ describe('matcher protocol', () => {
   type SomeValue<T> = T extends Some<infer V> ? V : never;
 
   interface SomeNarrowFn<p extends P.Pattern<unknown> = never> extends Fn {
-    return: [p] extends [never]
-      ? Some<SomeValue<this['arg0']>>
-      : Some<P.narrow<SomeValue<this['arg0']>, p>>;
+    output: [p] extends [never]
+      ? Some<SomeValue<this['input']>>
+      : Some<P.narrow<SomeValue<this['input']>, p>>;
   }
 
   class Some<const T> {
@@ -36,7 +36,7 @@ describe('matcher protocol', () => {
     }
   }
   interface NoneNarrowFn extends Fn {
-    return: None;
+    output: None;
   }
   class None {
     coucou: number;