unexpected.ts

export interface Module<State> {
    state(): State
}

export interface FooState {
    foo: String,
}

// No error
const correct: Module<FooState> = {
    state() {
        return {
            foo: 'bar',
            baz: 'qux'
        }
    }
}

// Error
const wrong: Module<FooState> = {
    state(): FooState {
        return {
            foo: 'bar',
            baz: 'qux' // <-- 'baz' does not exist in type 'FooState'
        }
    }
}