Split cross-package types from implementation

Some of our internal reconciler types have leaked into other packages.
Usually, these types are treated as opaque; we don't read and write
to its fields. This is good.

However, the type is often passed back to a reconciler method. For
example, React DOM creates a FiberRoot with `createContainer`, then
passes that root to `updateContainer`. It doesn't do anything with the
root except pass it through, but because `updateContainer` expects a
full FiberRoot, React DOM is still coupled to all its fields.

I don't know if there's an idiomatic way to handle this in Flow. Opaque
types are simlar, but those only work within a single file. AFAIK,
there's no way to use a package as the boundary for opaqueness.

The immediate problem this presents is that the reconciler refactor will
involve changes to our internal data structures. I don't want to have to
fork every single package that happens to pass through a Fiber or
FiberRoot, or access any one of its fields. So my current plan is to
share the same Flow type across both forks. The shared type will be a
superset of each implementation's type, e.g. Fiber will have both an
`expirationTime` field and a `lanes` field. The implementations will
diverge, but not the types.

To do this, I lifted the type definitions into a separate module.

Author: acdlite

packages/legacy-events/PluginModuleType.js

@@ -7,7 +7,7 @@
  * @flow
  */
 
-import type {Fiber} from 'react-reconciler/src/ReactFiber.old';
+import type {Fiber} from 'react-reconciler/src/ReactInternalTypes';
 import type {
   DispatchConfig,
   ReactSyntheticEvent,

packages/legacy-events/ReactSyntheticEventType.js

@@ -8,7 +8,7 @@
  * @flow
  */
 
-import type {Fiber} from 'react-reconciler/src/ReactFiber.old';
+import type {Fiber} from 'react-reconciler/src/ReactInternalTypes';
 import type {EventPriority} from 'shared/ReactTypes';
 import type {TopLevelType} from './TopLevelEventTypes';
 

packages/react-debug-tools/src/ReactDebugHooks.js

@@ -17,15 +17,13 @@ import type {
   ReactEventResponderListener,
   ReactScopeMethods,
 } from 'shared/ReactTypes';
-import type {Fiber} from 'react-reconciler/src/ReactFiber.old';
-import type {OpaqueIDType} from 'react-reconciler/src/ReactFiberHostConfig';
-
 import type {
-  Hook,
-  TimeoutConfig,
+  Fiber,
   Dispatcher as DispatcherType,
-} from 'react-reconciler/src/ReactFiberHooks.old';
-import type {SuspenseConfig} from 'react-reconciler/src/ReactFiberSuspenseConfig.old';
+} from 'react-reconciler/src/ReactInternalTypes';
+import type {OpaqueIDType} from 'react-reconciler/src/ReactFiberHostConfig';
+
+import type {SuspenseConfig} from 'react-reconciler/src/ReactFiberSuspenseConfig';
 import {NoMode} from 'react-reconciler/src/ReactTypeOfMode';
 
 import ErrorStackParser from 'error-stack-parser';
@@ -70,6 +68,15 @@ let primitiveStackCache: null | Map<string, Array<any>> = null;
 
 let currentFiber: Fiber | null = null;
 
+type Hook = {
+  memoizedState: any,
+  next: Hook | null,
+};
+
+type TimeoutConfig = {|
+  timeoutMs: number,
+|};
+
 function getPrimitiveStackCache(): Map<string, Array<any>> {
   // This initializes a cache of all primitive hooks so that the top
   // most stack frames added by calling the primitive hook can be removed.

packages/react-devtools-shared/src/backend/console.js

@@ -10,7 +10,7 @@
 import {getInternalReactConstants} from './renderer';
 import describeComponentFrame from './describeComponentFrame';
 
-import type {Fiber} from 'react-reconciler/src/ReactFiber.old';
+import type {Fiber} from 'react-reconciler/src/ReactInternalTypes';
 import type {ReactRenderer} from './types';
 
 const APPEND_STACK_TO_METHODS = ['error', 'trace', 'warn'];

packages/react-devtools-shared/src/backend/renderer.js

@@ -50,7 +50,7 @@ import {
   registerRenderer as registerRendererWithConsole,
 } from './console';
 
-import type {Fiber} from 'react-reconciler/src/ReactFiber.old';
+import type {Fiber} from 'react-reconciler/src/ReactInternalTypes';
 import type {
   ChangeDescription,
   CommitDataBackend,

packages/react-devtools-shared/src/backend/types.js

@@ -9,7 +9,7 @@
 
 import type {ReactContext} from 'shared/ReactTypes';
 import type {Source} from 'shared/ReactElementType';
-import type {Fiber} from 'react-reconciler/src/ReactFiber.old';
+import type {Fiber} from 'react-reconciler/src/ReactInternalTypes';
 import type {
   ComponentFilter,
   ElementType,

packages/react-dom/src/client/ReactDOMComponentTree.js

@@ -7,7 +7,7 @@
  * @flow
  */
 
-import type {Fiber} from 'react-reconciler/src/ReactFiber.old';
+import type {Fiber} from 'react-reconciler/src/ReactInternalTypes';
 import type {
   Container,
   TextInstance,

packages/react-dom/src/client/ReactDOMRoot.js

@@ -10,9 +10,7 @@
 import type {Container} from './ReactDOMHostConfig';
 import type {RootTag} from 'react-reconciler/src/ReactRootTags';
 import type {ReactNodeList} from 'shared/ReactTypes';
-// TODO: This type is shared between the reconciler and ReactDOM, but will
-// eventually be lifted out to the renderer.
-import type {FiberRoot} from 'react-reconciler/src/ReactFiberRoot.old';
+import type {FiberRoot} from 'react-reconciler/src/ReactInternalTypes';
 import {findHostInstanceWithNoPortals} from 'react-reconciler/src/ReactFiberReconciler';
 
 export type RootType = {

packages/react-dom/src/events/DOMLegacyEventPluginSystem.js

@@ -11,7 +11,7 @@ import type {AnyNativeEvent} from 'legacy-events/PluginModuleType';
 import type {DOMTopLevelEventType} from 'legacy-events/TopLevelEventTypes';
 import type {ElementListenerMap} from '../events/DOMEventListenerMap';
 import type {EventSystemFlags} from './EventSystemFlags';
-import type {Fiber} from 'react-reconciler/src/ReactFiber.old';
+import type {Fiber} from 'react-reconciler/src/ReactInternalTypes';
 import type {PluginModule} from 'legacy-events/PluginModuleType';
 import type {ReactSyntheticEvent} from 'legacy-events/ReactSyntheticEventType';
 import type {TopLevelType} from 'legacy-events/TopLevelEventTypes';

packages/react-dom/src/events/DOMModernPluginEventSystem.js

@@ -15,7 +15,7 @@ import type {
 } from '../events/DOMEventListenerMap';
 import type {EventSystemFlags} from './EventSystemFlags';
 import type {EventPriority, ReactScopeMethods} from 'shared/ReactTypes';
-import type {Fiber} from 'react-reconciler/src/ReactFiber.old';
+import type {Fiber} from 'react-reconciler/src/ReactInternalTypes';
 import type {PluginModule} from 'legacy-events/PluginModuleType';
 import type {
   ReactSyntheticEvent,