Modifying discriminated union doesn't work when nested in another object

[craggy bloom]

bnason#1204

Playground Link

Preview:```ts
//
// Step1 is a discriminated union on the phase key
//
type PendingStep1 = {
order: 1;
phase: 'PENDING';
progress: number;
};

type RunningStep1 = {
order: 1;
phase: 'RUNNING';
startedAt: Date;
progress: number;
};

type CompletedStep1 = {
order: 1;
...```

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[graceful dirge]

// Shouldn't steps.step1 be a RunningStep1, instead error says it's still a PendingStep1
steps.step1.startedAt;

not really

thing is, you defined steps as being of type Steps

and it will stay that type, unless you give it a new type later on

you can tell at line 42, steps is still of type Steps

and since type Steps is an union of the more precise steps, you can only access the properties that have in common: order, phase, progress

@glacial bear

at line 66, you give it type Step1
but the variable then changes type at line 78, to become RunningStep1
after you assigned the phase RUNNING

the reason for that difference between those 2 examples is the "level" the change occurs at

as you figured

also Steps.step1 will always be defined as Step1
which is very broad, accepts any state for the step 1 and won't change

[glacial bear]

Ok I understand what you are saying. Any idea how I can actually accomplish what I'm trying to?