refactor(evaluate): more consistent type inference

Author: pevisscher

src/function/evaluate/evaluate.spec.ts

@@ -3,7 +3,7 @@ import { evaluate } from './evaluate.js'
 import { sleep } from '../../async/index.js'
 import { asyncForAll, forAll, unknown } from '../../random/index.js'
 
-import { it } from 'vitest'
+import { it, expectTypeOf } from 'vitest'
 
 it('constant', () => {
     forAll(unknown(), (x) => evaluate(x) === x)
@@ -23,3 +23,20 @@ it('async fn', async () => {
         )
     })
 })
+
+it('types', () => {
+    expectTypeOf(evaluate(1)).toEqualTypeOf<1>()
+    expectTypeOf(evaluate('foo')).toEqualTypeOf<'foo'>()
+    expectTypeOf(evaluate(true)).toEqualTypeOf<true>()
+    expectTypeOf(evaluate(null)).toEqualTypeOf<null>()
+
+    expectTypeOf(evaluate(() => 1)).toEqualTypeOf<number>()
+    expectTypeOf(evaluate(() => 'foo')).toEqualTypeOf<string>()
+    expectTypeOf(evaluate(() => true)).toEqualTypeOf<boolean>()
+    expectTypeOf(evaluate(() => null)).toEqualTypeOf<null>()
+
+    expectTypeOf(evaluate((..._: any[]) => 1)).toEqualTypeOf<number>()
+    expectTypeOf(evaluate((..._: any[]) => 'foo')).toEqualTypeOf<string>()
+    expectTypeOf(evaluate((..._: any[]) => true)).toEqualTypeOf<boolean>()
+    expectTypeOf(evaluate((..._: any[]) => null)).toEqualTypeOf<null>()
+})

src/function/evaluate/evaluate.ts

@@ -1,7 +1,4 @@
 import { isFunction } from '../../guard/is-function/index.js'
-import type { ConstExpr } from '../../type/function/index.js'
-
-export type Evaluated<T extends ConstExpr> = T extends () => infer V ? V : T
 
 /**
  * Takes a value or a function that returns a value, and returns the value.
@@ -23,6 +20,6 @@ export type Evaluated<T extends ConstExpr> = T extends () => infer V ? V : T
  *
  * @group Functions
  */
-export function evaluate<T extends ConstExpr>(maybeEvaluate: T): Evaluated<T> {
-    return (isFunction(maybeEvaluate) ? maybeEvaluate() : maybeEvaluate) as Evaluated<T>
+export function evaluate<const T>(maybeEvaluate: T | (() => T)): T {
+    return isFunction(maybeEvaluate) ? maybeEvaluate() : maybeEvaluate
 }