string enums (ish, with some caveats) before ts 2.4

enums.ts

// cast the strings as any
enum StringEnum {
	a = 'a' as any,
	b = 'b' as any,
}

const a = StringEnum.a;
const x = 'a';
const y = 1;


const fn = (x: StringEnum) => 1;

// type error: Argument of type "a" is not assi...
fn(x)
fn('z')
      
// weirdly, no type error
fn(1)
fn(10)

// ok
fn(a)

// but can't narrow
class A {
	type = StringEnum.a;
	propA = true;
}
class B {
	type = StringEnum.b;
	propB = true;
}

type C = A | B;

function aOrB(c: C) {
	if(c.type === StringEnum.a) {
		// error - type B has no property propA
		return c.propA;
	}

}