No implicit any

src/constructors.ts

@@ -31,7 +31,9 @@ function toError(maybeError: unknown): Error {
  * That function is gonna catch any errors and always return a Result.
  * @param fn a function to be used as a Composable
  */
-function composable<T extends (...args: any[]) => any>(fn: T): Composable<T> {
+function composable<T extends Function>(
+  fn: T,
+): Composable<T extends (...args: any[]) => any ? T : never> {
   return async (...args) => {
     try {
       // deno-lint-ignore no-explicit-any

src/tests/constructors.test.ts

@@ -49,6 +49,12 @@ describe('composable', () => {
     assertEquals(res, success(3))
   })
 
+  it('will enforce noImplicitAny', () => {
+    // @ts-expect-error: implicit any
+    const fn = composable((a) => a)
+    type _FN = Expect<Equal<typeof fn, Composable<(a: any) => any>>>
+  })
+
   it('infers the types of async functions', async () => {
     const fn = composable(asyncAdd)
     const res = await fn(1, 2)
@@ -110,7 +116,7 @@ describe('fromSuccess', () => {
     const a = composable(() => 1)
 
     const c = fromSuccess(a)
-    type _R = Expect<Equal<typeof c, () => Promise<number>>>
+    type _R = Expect<Equal<typeof c, () => Promise<1>>>
 
     assertEquals(await c(), 1)
   })
@@ -145,7 +151,7 @@ describe('withSchema', () => {
       assertEquals(await handler(), success('no input!'))
     })
 
-    it('ignores the input and pass undefined', async () => {
+    it('defaults non-declared input to unknown', async () => {
       const handler = withSchema()((args) => args)
       type _R = Expect<
         Equal<