IfNotAnyOrNever: Lazily evaluate different conditional branches

[som-sm]

Consider the following example:

type CrashIfAnyWrapper<T> = IfNotAnyOrNever<T, CrashIfAny<T>, 'any handled', 'never handled'>;

type CrashIfAny<T, Acc extends unknown[] = []> = 0 extends 1 & T // Check if `T` is `any`
	? CrashIfAny<T, [...Acc, unknown]>
	: never;

// @ts-expect-error
type T1 = CrashIfAny<any>;

type T2 = CrashIfAnyWrapper<any>; // Should not error, but errors!

CrashIfAny is a type that fails when instantiated with any. To fix this, we try wrapping it in IfNotAnyOrNever to handle the any case explicitly, but this currently doesn't prevent the error. This happens because when we write IfNotAnyOrNever<T, CrashIfAny<T>, 'any handled'>, CrashIfAny is instantiated with T even if its value isn't going to be used.

Couldn't really find a great fix for this, but accepting the values for different cases in an object seems to fix this issue. It seems to make the compiler not do the instantiation until the value is actually accessed.

type CrashIfAnyWrapper<T> = IfNotAnyOrNever<T, {ifNot: CrashIfAny<T>; ifAny: 'any handled'; ifNever: 'never handled'}>;

type CrashIfAny<T, Acc extends unknown[] = []> = 0 extends 1 & T // Check if `T` is `any`
	? CrashIfAny<T, [...Acc, unknown]>
	: never;

// @ts-expect-error
type T1 = CrashIfAny<any>;

type T2 = CrashIfAnyWrapper<any>; // Works!

[som-sm]

Umm... would this be better?

Suggested change

	type A = IfNotAnyOrNever<string, {ifNot: 'VALID'; ifAny: 'IS_ANY'; ifNever: 'IS_NEVER'}>;
	type A = IfNotAnyOrNever<string, {neither: 'VALID'; any: 'IS_ANY'; never: 'IS_NEVER'}>;