🏷️ Better typings for constantFrom (#4103)

As recommended by #4047, let's leverage const generics to make usage of `constantFrom` even simpler for TS users.

.yarn/versions/be2c76af.yml

@@ -0,0 +1,8 @@
+releases:
+  fast-check: minor
+
+declined:
+  - "@fast-check/ava"
+  - "@fast-check/jest"
+  - "@fast-check/vitest"
+  - "@fast-check/worker"

packages/fast-check/src/arbitrary/_internals/builders/StringifiedNatArbitraryBuilder.ts

@@ -6,7 +6,7 @@ import { natToStringifiedNatMapper, natToStringifiedNatUnmapper } from '../mappe
 
 /** @internal */
 export function buildStringifiedNatArbitrary(maxValue: number): Arbitrary<string> {
-  return tuple(constantFrom<('dec' | 'oct' | 'hex')[]>('dec', 'oct', 'hex'), nat(maxValue)).map(
+  return tuple(constantFrom('dec', 'oct', 'hex'), nat(maxValue)).map(
     natToStringifiedNatMapper,
     natToStringifiedNatUnmapper,
   );

packages/fast-check/src/arbitrary/constantFrom.ts

@@ -16,7 +16,7 @@ type Elem<T> = T extends any[] ? T[number] : T;
  * @remarks Since 0.0.12
  * @public
  */
-function constantFrom<T = never>(...values: T[]): Arbitrary<T>;
+function constantFrom<const T = never>(...values: T[]): Arbitrary<T>;
 
 /**
  * For one `...values` values - all equiprobable

packages/fast-check/test-types/main.ts

@@ -87,7 +87,7 @@ expectType<fc.Arbitrary<string[]>>()(
   fc.nat().chain((n) => fc.array(fc.char(), { maxLength: n })),
   'Type of "chain" corresponds to the return type of the passed lambda',
 );
-expectType<fc.Arbitrary<number>>()(
+expectType<fc.Arbitrary<1 | 2 | 3>>()(
   fc.constantFrom(1, 2, 3).chain((value) => fc.constant(value)),
   'Type of "chain" corresponds to the return type of the passed lambda',
 );
@@ -110,21 +110,19 @@ expectType<fc.Arbitrary<string>>()(
 );
 
 // constantFrom arbitrary
-expectType<fc.Arbitrary<number>>()(
-  fc.constantFrom(1, 2),
-  'By default, "constantFrom" simplifies the type (eg.: "1 -> number")',
-);
+expectType<fc.Arbitrary<1 | 2>>()(fc.constantFrom(1, 2), 'By default, "constantFrom" preserves the precise type');
+expectType<fc.Arbitrary<number>>()(fc.constantFrom<number[]>(1, 2), 'But it also accepts to receive the type');
 expectType<fc.Arbitrary<1 | 2>>()(
   fc.constantFrom(...([1, 2] as const)),
-  '"as const" prevent extra simplification of "constantFrom"',
+  '"as const" was a way to prevent extra simplification of "constantFrom", it\'s now not needed anymore',
 );
 expectType<fc.Arbitrary<number | string>>()(
   fc.constantFrom(1, 2, 'hello'),
   '"constantFrom" accepts arguments not having the same types without any typing trick',
 );
 expectType<fc.Arbitrary<1 | 2 | 'hello'>>()(
   fc.constantFrom(...([1, 2, 'hello'] as const)),
-  '"as const" prevent extra simplification of "constantFrom"',
+  '"as const" was a way to prevent extra simplification of "constantFrom"',
 );
 
 // uniqueArray arbitrary