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**Do you want to request a *feature* or report a *bug*?**
bug, I believe, unless I misunderstand how it works
**What is the current behavior?**
Given a `Suspense` inside `Suspense` case like
```
<Suspense fallback="Fallback 1">
  <LazyText1 text="First text" />
  <Suspense fallback="Fallback 2">
    <LazyText2 text="Second text!" />
  </Suspense>
</Suspense>
```

Promises in `LazyTexts` start resolving at the same time, but if `LazyText2` is resolved first it never renders, `Fallback 2` stays.

Result:
```
First text

Fallback 2
```

Please see https://codesandbox.io/s/234o4zry7n

**What is the expected behavior?**

Every `LazyText` displayed in the end
```
First text

Second text!
```

**Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?**
react, react-dom 16.6.0

let nextRenderExpirationTime: ExpirationTime = NoWork;
let nextLatestAbsoluteTimeoutMs: number = -1;
let nextRenderDidError: boolean = false;
let nextEffect: Fiber | null = null;
let isCommitting: boolean = false;
let rootWithPendingPassiveEffects: FiberRoot | null = null;
let passiveEffectCallbackHandle: * = null;
let passiveEffectCallback: * = null;
let legacyErrorBoundariesThatAlreadyFailed: Set<mixed> | null = null;
// Used for performance tracking.
let interruptedBy: Fiber | null = null;
let stashedWorkInProgressProperties;
let replayUnitOfWork;
let isReplayingFailedUnitOfWork;
let originalReplayError;
let rethrowOriginalError;
if (__DEV__ && replayFailedUnitOfWorkWithInvokeGuardedCallback) {
  stashedWorkInProgressProperties = null;
  isReplayingFailedUnitOfWork = false;
  originalReplayError = null;
  replayUnitOfWork = (
    failedUnitOfWork: Fiber,
    thrownValue: mixed,
    isYieldy: boolean,
  ) => {
    if (
      thrownValue !== null &&
      typeof thrownValue === 'object' &&
      typeof thrownValue.then === 'function'
    ) {