This DEV-only field was added in 836331ba5f69f2cc53b273ec073fae116db14302 by @sebmarkbage but it's not being used anymore to my knowledge.
StaticMask,
} from './ReactFiberFlags';
import ReactSharedInternals from 'shared/ReactSharedInternals';
import {
  debugRenderPhaseSideEffectsForStrictMode,
  disableLegacyContext,
  disableModulePatternComponents,
  enableProfilerCommitHooks,
  enableProfilerTimer,
  enableSuspenseServerRenderer,
  warnAboutDefaultPropsOnFunctionComponents,
  enableScopeAPI,
  enableCache,
  enableLazyContextPropagation,
  enableSuspenseLayoutEffectSemantics,
} from 'shared/ReactFeatureFlags';
import invariant from 'shared/invariant';
import isArray from 'shared/isArray';
import shallowEqual from 'shared/shallowEqual';
import getComponentNameFromFiber from 'react-reconciler/src/getComponentNameFromFiber';
import getComponentNameFromType from 'shared/getComponentNameFromType';
import ReactStrictModeWarnings from './ReactStrictModeWarnings.new';
import {REACT_LAZY_TYPE, getIteratorFn} from 'shared/ReactSymbols';
import {
  getCurrentFiberOwnerNameInDevOrNull,
  setIsRendering,
} from './ReactCurrentFiber';
import {
  resolveFunctionForHotReloading,
  resolveForwardRefForHotReloading,