This DEV-only field was added in 836331ba5f69f2cc53b273ec073fae116db14302 by @sebmarkbage but it's not being used anymore to my knowledge.
FunctionComponent,
  MemoComponent,
  SimpleMemoComponent,
  LazyComponent,
  ScopeComponent,
  OffscreenComponent,
  LegacyHiddenComponent,
  CacheComponent,
} from './ReactWorkTags';
import getComponentNameFromFiber from 'react-reconciler/src/getComponentNameFromFiber';
import {isDevToolsPresent} from './ReactFiberDevToolsHook.old';
import {
  resolveClassForHotReloading,
  resolveFunctionForHotReloading,
  resolveForwardRefForHotReloading,
} from './ReactFiberHotReloading.old';
import {NoLanes} from './ReactFiberLane.old';
import {
  NoMode,
  ConcurrentMode,
  DebugTracingMode,
  ProfileMode,
  StrictLegacyMode,
  StrictEffectsMode,
  ConcurrentUpdatesByDefaultMode,
} from './ReactTypeOfMode';
import {
  REACT_FORWARD_REF_TYPE,
  REACT_FRAGMENT_TYPE,
  REACT_DEBUG_TRACING_MODE_TYPE,