Bug in destructuring assignment, losing type analysis information

[tomcumming]

TypeScript version: 2.0.8

export type State = {
    value: string,
    mode: Selecting | Selected,
}

type Selected = {
    type: 'selected',
    valid: boolean
}

type Selecting = {
    type: 'selecting',
    options: { type: 'loading', handle: number }
        | { type: 'loaded', selection: undefined | number, items: string[] }
}

function f(state: State) {
    if (state.mode.type === 'selecting' && state.mode.options.type === 'loaded') {
        const {options} = state.mode;
        const options2 = state.mode.options;
        options2.items;        
        options.items;
    }
}

Expected
inside f, options and options2 should have the same type

Actual
options loses the narrowed type information

[ahejlsberg]

Duplicate of #10065 and #10846.