Boolean inference is too strict

[hipolipolopigus]

TypeScript Version: 3.5.0-dev.20190503

Search Terms: Boolean inference true false

Code

type State<TStateKeys extends string = string> = {
	[k in TStateKeys]: boolean | number | string
};

class Foo<TState extends State> {
	constructor(public state: TState) {}
}

const obj = new Foo({
	a: 1,
	b: "string",
	c: true,
	d: false,
	// Workaround
	e: !!false
});

obj.state.a = 2; // No error
obj.state.b = "another string"; // No error

// Accepts only `false`, should accept either
obj.state.c = false; // TS2322: Type 'false' is not assignable to type 'true'.

// Accepts only `true`, should accept either
obj.state.d = true; // TS2322: Type 'true' is not assignable to type 'false'.

// Accepts either boolean
obj.state.e = true; // No error

Expected behavior: obj.state.c and obj.state.d accept either boolean.

Actual behavior: obj.state.c and obj.state.d are hard-typed to true and false, respectively.

[ahejlsberg]

This issue has the same root cause as #30390, so I'm marking it as a duplicate.

[typescript-bot]

This issue has been marked as a 'Duplicate' and has seen no recent activity. It has been automatically closed for house-keeping purposes.