OptionalstrictConsider never elements to match the target type only if the target type itself is never (or any).
true (default), never is not treated as a bottom type, instead, it is treated as a type that matches only itself (or any).false, never is treated as a bottom type, and behaves as it normally would.import type {AllExtend} from 'type-fest';
type A = AllExtend<[1, 2, never], number, {strictNever: true}>;
//=> false
type B = AllExtend<[1, 2, never], number, {strictNever: false}>;
//=> true
type C = AllExtend<[never, never], never, {strictNever: true}>;
//=> true
type D = AllExtend<[never, never], never, {strictNever: false}>;
//=> true
type E = AllExtend<['a', 'b', never], any, {strictNever: true}>;
//=> true
type F = AllExtend<['a', 'b', never], any, {strictNever: false}>;
//=> true
type G = AllExtend<[never, 1], never, {strictNever: true}>;
//=> false
type H = AllExtend<[never, 1], never, {strictNever: false}>;
//=> false
See
AllExtend