arrayFilterBooleanOverload.types

//// [tests/cases/compiler/arrayFilterBooleanOverload.ts] ////

=== arrayFilterBooleanOverload.ts ===
const nullableValues = ['a', 'b', null]; // expect (string | null)[]
>nullableValues : (string | null)[]
>['a', 'b', null] : (string | null)[]
>'a' : "a"
>'b' : "b"

const values1 = nullableValues.filter(Boolean); // expect string[]
>values1 : string[]
>nullableValues.filter(Boolean) : string[]
>nullableValues.filter : { <S extends string | null>(predicate: (value: string | null, index: number, array: (string | null)[]) => value is S, thisArg?: any): S[]; (predicate: (value: string | null, index: number, array: (string | null)[]) => unknown, thisArg?: any): (string | null)[]; }
>nullableValues : (string | null)[]
>filter : { <S extends string | null>(predicate: (value: string | null, index: number, array: (string | null)[]) => value is S, thisArg?: any): S[]; (predicate: (value: string | null, index: number, array: (string | null)[]) => unknown, thisArg?: any): (string | null)[]; }
>Boolean : BooleanConstructor

// @ts-expect-error
const values2 = nullableValues.filter(new Boolean);
>values2 : (string | null)[]
>nullableValues.filter(new Boolean) : (string | null)[]
>nullableValues.filter : { <S extends string | null>(predicate: (value: string | null, index: number, array: (string | null)[]) => value is S, thisArg?: any): S[]; (predicate: (value: string | null, index: number, array: (string | null)[]) => unknown, thisArg?: any): (string | null)[]; }
>nullableValues : (string | null)[]
>filter : { <S extends string | null>(predicate: (value: string | null, index: number, array: (string | null)[]) => value is S, thisArg?: any): S[]; (predicate: (value: string | null, index: number, array: (string | null)[]) => unknown, thisArg?: any): (string | null)[]; }
>new Boolean : Boolean
>Boolean : BooleanConstructor

const arr = [0, 1, "", "foo", null] as const;
>arr : readonly [0, 1, "", "foo", null]
>[0, 1, "", "foo", null] as const : readonly [0, 1, "", "foo", null]
>[0, 1, "", "foo", null] : readonly [0, 1, "", "foo", null]
>0 : 0
>1 : 1
>"" : ""
>"foo" : "foo"

const arr2 = arr.filter(Boolean); // expect ("foo" | 1)[]
>arr2 : (1 | "foo")[]
>arr.filter(Boolean) : (1 | "foo")[]
>arr.filter : { <S extends "" | 0 | 1 | "foo" | null>(predicate: (value: "" | 0 | 1 | "foo" | null, index: number, array: readonly ("" | 0 | 1 | "foo" | null)[]) => value is S, thisArg?: any): S[]; (predicate: (value: "" | 0 | 1 | "foo" | null, index: number, array: readonly ("" | 0 | 1 | "foo" | null)[]) => unknown, thisArg?: any): ("" | 0 | 1 | "foo" | null)[]; }
>arr : readonly [0, 1, "", "foo", null]
>filter : { <S extends "" | 0 | 1 | "foo" | null>(predicate: (value: "" | 0 | 1 | "foo" | null, index: number, array: readonly ("" | 0 | 1 | "foo" | null)[]) => value is S, thisArg?: any): S[]; (predicate: (value: "" | 0 | 1 | "foo" | null, index: number, array: readonly ("" | 0 | 1 | "foo" | null)[]) => unknown, thisArg?: any): ("" | 0 | 1 | "foo" | null)[]; }
>Boolean : BooleanConstructor