Avoid meta programming to initialize functions in module scope (#26388)

I'm trying to get rid of all meta programming in the module scope so
that closure can do a better job figuring out cyclic dependencies and
ability to reorder.

This is converting a lot of the patterns that assign functions
conditionally to using function declarations instead.

```
let fn;
if (__DEV__) {
  fn = function() {
    ...
  };
}
```
->
```
function fn() {
  if (__DEV__) {
    ...
  }
}
```

packages/dom-event-testing-library/domEnvironment.js

@@ -13,7 +13,7 @@
  * Change environment support for PointerEvent.
  */
 
-const emptyFunction = function () {};
+function emptyFunction() {}
 
 export function hasPointerEvent() {
   return global != null && global.PointerEvent != null;

packages/react-dom-bindings/src/client/ReactDOMComponent.js

@@ -94,15 +94,8 @@ const HTML = '__html';
 let warnedUnknownTags: {
   [key: string]: boolean,
 };
-
-let validatePropertiesInDevelopment;
-let warnForPropDifference;
-let warnForExtraAttributes;
-let warnForInvalidEventListener;
 let canDiffStyleForHydrationWarning;
 
-let normalizeHTML;
-
 if (__DEV__) {
   warnedUnknownTags = {
     // There are working polyfills for <dialog>. Let people use it.
@@ -115,15 +108,6 @@ if (__DEV__) {
     webview: true,
   };
 
-  validatePropertiesInDevelopment = function (type: string, props: any) {
-    validateARIAProperties(type, props);
-    validateInputProperties(type, props);
-    validateUnknownProperties(type, props, {
-      registrationNameDependencies,
-      possibleRegistrationNames,
-    });
-  };
-
   // IE 11 parses & normalizes the style attribute as opposed to other
   // browsers. It adds spaces and sorts the properties in some
   // non-alphabetical order. Handling that would require sorting CSS
@@ -133,12 +117,25 @@ if (__DEV__) {
   // in that browser completely in favor of doing all that work.
   // See https://github.com/facebook/react/issues/11807
   canDiffStyleForHydrationWarning = canUseDOM && !document.documentMode;
+}
 
-  warnForPropDifference = function (
+function validatePropertiesInDevelopment(type: string, props: any) {
+  if (__DEV__) {
+    validateARIAProperties(type, props);
+    validateInputProperties(type, props);
+    validateUnknownProperties(type, props, {
+      registrationNameDependencies,
+      possibleRegistrationNames,
+    });
+  }
+}
+
+function warnForPropDifference(
   propName: string,
   serverValue: mixed,
   clientValue: mixed,
-  ) {
+) {
+  if (__DEV__) {
     if (didWarnInvalidHydration) {
       return;
     }
@@ -156,9 +153,11 @@ if (__DEV__) {
       JSON.stringify(normalizedServerValue),
       JSON.stringify(normalizedClientValue),
     );
-  };
+  }
+}
 
-  warnForExtraAttributes = function (attributeNames: Set<string>) {
+function warnForExtraAttributes(attributeNames: Set<string>) {
+  if (__DEV__) {
     if (didWarnInvalidHydration) {
       return;
     }
@@ -168,12 +167,11 @@ if (__DEV__) {
       names.push(name);
     });
     console.error('Extra attributes from the server: %s', names);
-  };
+  }
+}
 
-  warnForInvalidEventListener = function (
+function warnForInvalidEventListener(registrationName: string, listener: any) {
-    registrationName: string,
+  if (__DEV__) {
-    listener: any,
-  ) {
     if (listener === false) {
       console.error(
         'Expected `%s` listener to be a function, instead got `false`.\n\n' +
@@ -190,11 +188,13 @@ if (__DEV__) {
         typeof listener,
       );
     }
-  };
+  }
+}
 
-  // Parse the HTML and read it back to normalize the HTML string so that it
+// Parse the HTML and read it back to normalize the HTML string so that it
-  // can be used for comparison.
+// can be used for comparison.
-  normalizeHTML = function (parent: Element, html: string) {
+function normalizeHTML(parent: Element, html: string) {
+  if (__DEV__) {
     // We could have created a separate document here to avoid
     // re-initializing custom elements if they exist. But this breaks
     // how <noscript> is being handled. So we use the same document.
@@ -208,7 +208,7 @@ if (__DEV__) {
           );
     testElement.innerHTML = html;
     return testElement.innerHTML;
-  };
+  }
 }
 
 // HTML parsing normalizes CR and CRLF to LF.

packages/react-dom-bindings/src/client/createMicrosoftUnsafeLocalFunction.js

@@ -1,25 +0,0 @@
-/**
- * Copyright (c) Meta Platforms, Inc. and affiliates.
- *
- * This source code is licensed under the MIT license found in the
- * LICENSE file in the root directory of this source tree.
- */
-
-/* globals MSApp */
-
-/**
- * Create a function which has 'unsafe' privileges (required by windows8 apps)
- */
-const createMicrosoftUnsafeLocalFunction = function (func) {
-  if (typeof MSApp !== 'undefined' && MSApp.execUnsafeLocalFunction) {
-    return function (arg0, arg1, arg2, arg3) {
-      MSApp.execUnsafeLocalFunction(function () {
-        return func(arg0, arg1, arg2, arg3);
-      });
-    };
-  } else {
-    return func;
-  }
-};
-
-export default createMicrosoftUnsafeLocalFunction;

packages/react-dom-bindings/src/client/setInnerHTML.js

@@ -7,24 +7,15 @@
  * @flow
  */
 
+/* globals MSApp */
+
 import {SVG_NAMESPACE} from './DOMNamespaces';
-import createMicrosoftUnsafeLocalFunction from './createMicrosoftUnsafeLocalFunction';
 import {enableTrustedTypesIntegration} from 'shared/ReactFeatureFlags';
 
 // SVG temp container for IE lacking innerHTML
 let reusableSVGContainer: HTMLElement;
 
-/**
+function setInnerHTMLImpl(
- * Set the innerHTML property of a node
- *
- * @param {DOMElement} node
- * @param {string} html
- * @internal
- */
-const setInnerHTML: (
-  node: Element,
-  html: {valueOf(): {toString(): string, ...}, ...},
-) => void = createMicrosoftUnsafeLocalFunction(function (
   node: Element,
   html: {valueOf(): {toString(): string, ...}, ...},
 ): void {
@@ -66,6 +57,26 @@ const setInnerHTML: (
     }
   }
   node.innerHTML = (html: any);
-});
+}
+
+let setInnerHTML: (
+  node: Element,
+  html: {valueOf(): {toString(): string, ...}, ...},
+) => void = setInnerHTMLImpl;
+// $FlowFixMe[cannot-resolve-name]
+if (typeof MSApp !== 'undefined' && MSApp.execUnsafeLocalFunction) {
+  /**
+   * Create a function which has 'unsafe' privileges (required by windows8 apps)
+   */
+  setInnerHTML = function (
+    node: Element,
+    html: {valueOf(): {toString(): string, ...}, ...},
+  ): void {
+    // $FlowFixMe[cannot-resolve-name]
+    return MSApp.execUnsafeLocalFunction(function () {
+      return setInnerHTMLImpl(node, html);
+    });
+  };
+}
 
 export default setInnerHTML;

packages/react-dom-bindings/src/client/setTextContent.js

@@ -18,7 +18,7 @@ import {TEXT_NODE} from './HTMLNodeType';
  * @param {string} text
  * @internal
  */
-const setTextContent = function (node: Element, text: string): void {
+function setTextContent(node: Element, text: string): void {
   if (text) {
     const firstChild = node.firstChild;
 
@@ -32,6 +32,6 @@ const setTextContent = function (node: Element, text: string): void {
     }
   }
   node.textContent = text;
-};
+}
 
 export default setTextContent;

packages/react-dom-bindings/src/client/validateDOMNesting.js

@@ -7,12 +7,6 @@
  * @flow
  */
 
-type ValidateDOMNesting = (?string, ?string, AncestorInfoDev) => void;
-let validateDOMNesting: ValidateDOMNesting = (() => {}: any);
-
-type UpdatedAncestorInfoDev = (?AncestorInfoDev, string) => AncestorInfoDev;
-let updatedAncestorInfoDev: UpdatedAncestorInfoDev = (() => {}: any);
-
 type Info = {tag: string};
 export type AncestorInfoDev = {
   current: ?Info,
@@ -30,20 +24,19 @@ export type AncestorInfoDev = {
   containerTagInScope: ?Info,
 };
 
-if (__DEV__) {
+// This validation code was written based on the HTML5 parsing spec:
-  // This validation code was written based on the HTML5 parsing spec:
+// https://html.spec.whatwg.org/multipage/syntax.html#has-an-element-in-scope
-  // https://html.spec.whatwg.org/multipage/syntax.html#has-an-element-in-scope
+//
-  //
+// Note: this does not catch all invalid nesting, nor does it try to (as it's
-  // Note: this does not catch all invalid nesting, nor does it try to (as it's
+// not clear what practical benefit doing so provides); instead, we warn only
-  // not clear what practical benefit doing so provides); instead, we warn only
+// for cases where the parser will give a parse tree differing from what React
-  // for cases where the parser will give a parse tree differing from what React
+// intended. For example, <b><div></div></b> is invalid but we don't warn
-  // intended. For example, <b><div></div></b> is invalid but we don't warn
+// because it still parses correctly; we do warn for other cases like nested
-  // because it still parses correctly; we do warn for other cases like nested
+// <p> tags where the beginning of the second element implicitly closes the
-  // <p> tags where the beginning of the second element implicitly closes the
+// first, causing a confusing mess.
-  // first, causing a confusing mess.
 
-  // https://html.spec.whatwg.org/multipage/syntax.html#special
+// https://html.spec.whatwg.org/multipage/syntax.html#special
-  const specialTags = [
+const specialTags = [
   'address',
   'applet',
   'area',
@@ -127,10 +120,10 @@ if (__DEV__) {
   'ul',
   'wbr',
   'xmp',
-  ];
+];
 
-  // https://html.spec.whatwg.org/multipage/syntax.html#has-an-element-in-scope
+// https://html.spec.whatwg.org/multipage/syntax.html#has-an-element-in-scope
-  const inScopeTags = [
+const inScopeTags = [
   'applet',
   'caption',
   'html',
@@ -147,13 +140,13 @@ if (__DEV__) {
   'foreignObject',
   'desc',
   'title',
-  ];
+];
 
-  // https://html.spec.whatwg.org/multipage/syntax.html#has-an-element-in-button-scope
+// https://html.spec.whatwg.org/multipage/syntax.html#has-an-element-in-button-scope
-  const buttonScopeTags = inScopeTags.concat(['button']);
+const buttonScopeTags = __DEV__ ? inScopeTags.concat(['button']) : [];
 
-  // https://html.spec.whatwg.org/multipage/syntax.html#generate-implied-end-tags
+// https://html.spec.whatwg.org/multipage/syntax.html#generate-implied-end-tags
-  const impliedEndTags = [
+const impliedEndTags = [
   'dd',
   'dt',
   'li',
@@ -162,9 +155,9 @@ if (__DEV__) {
   'p',
   'rp',
   'rt',
-  ];
+];
 
-  const emptyAncestorInfoDev: AncestorInfoDev = {
+const emptyAncestorInfoDev: AncestorInfoDev = {
   current: null,
 
   formTag: null,
@@ -177,9 +170,13 @@ if (__DEV__) {
   dlItemTagAutoclosing: null,
 
   containerTagInScope: null,
-  };
+};
 
-  updatedAncestorInfoDev = function (oldInfo: ?AncestorInfoDev, tag: string) {
+function updatedAncestorInfoDev(
+  oldInfo: ?AncestorInfoDev,
+  tag: string,
+): AncestorInfoDev {
+  if (__DEV__) {
     const ancestorInfo = {...(oldInfo || emptyAncestorInfoDev)};
     const info = {tag};
 
@@ -234,15 +231,15 @@ if (__DEV__) {
     }
 
     return ancestorInfo;
-  };
+  } else {
+    return (null: any);
+  }
+}
 
-  /**
+/**
  * Returns whether
  */
-  const isTagValidWithParent = function (
+function isTagValidWithParent(tag: string, parentTag: ?string): boolean {
-    tag: string,
-    parentTag: ?string,
-  ): boolean {
   // First, let's check if we're in an unusual parsing mode...
   switch (parentTag) {
     // https://html.spec.whatwg.org/multipage/syntax.html#parsing-main-inselect
@@ -362,15 +359,15 @@ if (__DEV__) {
   }
 
   return true;
-  };
+}
 
-  /**
+/**
  * Returns whether
  */
-  const findInvalidAncestorForTag = function (
+function findInvalidAncestorForTag(
   tag: string,
   ancestorInfo: AncestorInfoDev,
-  ): ?Info {
+): ?Info {
   switch (tag) {
     case 'address':
     case 'article':
@@ -432,15 +429,16 @@ if (__DEV__) {
   }
 
   return null;
-  };
+}
 
-  const didWarn: {[string]: boolean} = {};
+const didWarn: {[string]: boolean} = {};
 
-  validateDOMNesting = function (
+function validateDOMNesting(
   childTag: ?string,
   childText: ?string,
   ancestorInfo: AncestorInfoDev,
-  ) {
+): void {
+  if (__DEV__) {
     ancestorInfo = ancestorInfo || emptyAncestorInfoDev;
     const parentInfo = ancestorInfo.current;
     const parentTag = parentInfo && parentInfo.tag;
@@ -517,7 +515,7 @@ if (__DEV__) {
         ancestorTag,
       );
     }
-  };
+  }
 }
 
 export {updatedAncestorInfoDev, validateDOMNesting};

packages/react-dom-bindings/src/shared/ReactDOMUnknownPropertyHook.js

@@ -16,16 +16,18 @@ import isCustomComponent from './isCustomComponent';
 import possibleStandardNames from './possibleStandardNames';
 import hasOwnProperty from 'shared/hasOwnProperty';
 
-let validateProperty = () => {};
+const warnedProperties = {};
+const EVENT_NAME_REGEX = /^on./;
+const INVALID_EVENT_NAME_REGEX = /^on[^A-Z]/;
+const rARIA = __DEV__
+  ? new RegExp('^(aria)-[' + ATTRIBUTE_NAME_CHAR + ']*$')
+  : null;
+const rARIACamel = __DEV__
+  ? new RegExp('^(aria)[A-Z][' + ATTRIBUTE_NAME_CHAR + ']*$')
+  : null;
 
-if (__DEV__) {
+function validateProperty(tagName, name, value, eventRegistry) {
-  const warnedProperties = {};
+  if (__DEV__) {
-  const EVENT_NAME_REGEX = /^on./;
-  const INVALID_EVENT_NAME_REGEX = /^on[^A-Z]/;
-  const rARIA = new RegExp('^(aria)-[' + ATTRIBUTE_NAME_CHAR + ']*$');
-  const rARIACamel = new RegExp('^(aria)[A-Z][' + ATTRIBUTE_NAME_CHAR + ']*$');
-
-  validateProperty = function (tagName, name, value, eventRegistry) {
     if (hasOwnProperty.call(warnedProperties, name) && warnedProperties[name]) {
       return true;
     }
@@ -234,10 +236,10 @@ if (__DEV__) {
     }
 
     return true;
-  };
+  }
 }
 
-const warnUnknownProperties = function (type, props, eventRegistry) {
+function warnUnknownProperties(type, props, eventRegistry) {
   if (__DEV__) {
     const unknownProps = [];
     for (const key in props) {
@@ -268,7 +270,7 @@ const warnUnknownProperties = function (type, props, eventRegistry) {
       );
     }
   }
-};
+}
 
 export function validateProperties(type, props, eventRegistry) {
   if (isCustomComponent(type, props)) {

packages/react-dom-bindings/src/shared/warnValidStyle.js

@@ -5,29 +5,27 @@
  * LICENSE file in the root directory of this source tree.
  */
 
-let warnValidStyle = () => {};
+// 'msTransform' is correct, but the other prefixes should be capitalized
+const badVendoredStyleNamePattern = /^(?:webkit|moz|o)[A-Z]/;
+const msPattern = /^-ms-/;
+const hyphenPattern = /-(.)/g;
 
-if (__DEV__) {
+// style values shouldn't contain a semicolon
-  // 'msTransform' is correct, but the other prefixes should be capitalized
+const badStyleValueWithSemicolonPattern = /;\s*$/;
-  const badVendoredStyleNamePattern = /^(?:webkit|moz|o)[A-Z]/;
-  const msPattern = /^-ms-/;
-  const hyphenPattern = /-(.)/g;
 
-  // style values shouldn't contain a semicolon
+const warnedStyleNames = {};
-  const badStyleValueWithSemicolonPattern = /;\s*$/;
+const warnedStyleValues = {};
+let warnedForNaNValue = false;
+let warnedForInfinityValue = false;
 
-  const warnedStyleNames = {};
+function camelize(string) {
-  const warnedStyleValues = {};
-  let warnedForNaNValue = false;
-  let warnedForInfinityValue = false;
-
-  const camelize = function (string) {
   return string.replace(hyphenPattern, function (_, character) {
     return character.toUpperCase();
   });
-  };
+}
 
-  const warnHyphenatedStyleName = function (name) {
+function warnHyphenatedStyleName(name) {
+  if (__DEV__) {
     if (warnedStyleNames.hasOwnProperty(name) && warnedStyleNames[name]) {
       return;
     }
@@ -41,9 +39,11 @@ if (__DEV__) {
       // is converted to lowercase `ms`.
       camelize(name.replace(msPattern, 'ms-')),
     );
-  };
+  }
+}
 
-  const warnBadVendoredStyleName = function (name) {
+function warnBadVendoredStyleName(name) {
+  if (__DEV__) {
     if (warnedStyleNames.hasOwnProperty(name) && warnedStyleNames[name]) {
       return;
     }
@@ -54,9 +54,11 @@ if (__DEV__) {
       name,
       name.charAt(0).toUpperCase() + name.slice(1),
     );
-  };
+  }
+}
 
-  const warnStyleValueWithSemicolon = function (name, value) {
+function warnStyleValueWithSemicolon(name, value) {
+  if (__DEV__) {
     if (warnedStyleValues.hasOwnProperty(value) && warnedStyleValues[value]) {
       return;
     }
@@ -68,9 +70,11 @@ if (__DEV__) {
       name,
       value.replace(badStyleValueWithSemicolonPattern, ''),
     );
-  };
+  }
+}
 
-  const warnStyleValueIsNaN = function (name, value) {
+function warnStyleValueIsNaN(name, value) {
+  if (__DEV__) {
     if (warnedForNaNValue) {
       return;
     }
@@ -80,9 +84,11 @@ if (__DEV__) {
       '`NaN` is an invalid value for the `%s` css style property.',
       name,
     );
-  };
+  }
+}
 
-  const warnStyleValueIsInfinity = function (name, value) {
+function warnStyleValueIsInfinity(name, value) {
+  if (__DEV__) {
     if (warnedForInfinityValue) {
       return;
     }
@@ -92,9 +98,11 @@ if (__DEV__) {
       '`Infinity` is an invalid value for the `%s` css style property.',
       name,
     );
-  };
+  }
+}
 
-  warnValidStyle = function (name, value) {
+function warnValidStyle(name, value) {
+  if (__DEV__) {
     if (name.indexOf('-') > -1) {
       warnHyphenatedStyleName(name);
     } else if (badVendoredStyleNamePattern.test(name)) {
@@ -110,7 +118,7 @@ if (__DEV__) {
         warnStyleValueIsInfinity(name, value);
       }
     }
-  };
+  }
 }
 
 export default warnValidStyle;

packages/react-dom/src/test-utils/ReactTestUtils.js

@@ -392,7 +392,7 @@ function executeDispatchesInOrder(event) {
  * @param {?object} event Synthetic event to be dispatched.
  * @private
  */
-const executeDispatchesAndRelease = function (event /* ReactSyntheticEvent */) {
+function executeDispatchesAndRelease(event /* ReactSyntheticEvent */) {
   if (event) {
     executeDispatchesInOrder(event);
 
@@ -400,7 +400,7 @@ const executeDispatchesAndRelease = function (event /* ReactSyntheticEvent */) {
       event.constructor.release(event);
     }
   }
-};
+}
 
 function isInteractive(tag) {
   return (

packages/react-native-renderer/src/ReactNativeEventEmitter.js

@@ -44,13 +44,13 @@ const EMPTY_NATIVE_EVENT = (({}: any): AnyNativeEvent);
  * @return {Array<Touch>} Subsequence of touch objects.
  */
 // $FlowFixMe[missing-local-annot]
-const touchSubsequence = function (touches, indices) {
+function touchSubsequence(touches, indices) {
   const ret = [];
   for (let i = 0; i < indices.length; i++) {
     ret.push(touches[indices[i]]);
   }
   return ret;
-};
+}
 
 /**
  * TODO: Pool all of this.
@@ -63,7 +63,7 @@ const touchSubsequence = function (touches, indices) {
  * @param {Array<number>} indices Indices to remove from `touches`.
  * @return {Array<Touch>} Subsequence of removed touch objects.
  */
-const removeTouchesAtIndices = function (
+function removeTouchesAtIndices(
   touches: Array<Object>,
   indices: Array<number>,
 ): Array<Object> {
@@ -85,7 +85,7 @@ const removeTouchesAtIndices = function (
   }
   temp.length = fillAt;
   return rippedOut;
-};
+}
 
 /**
  * Internal version of `receiveEvent` in terms of normalized (non-tag)

packages/react-native-renderer/src/ReactNativeFiberInspector.js

@@ -28,19 +28,8 @@ if (__DEV__) {
   Object.freeze(emptyObject);
 }
 
-let createHierarchy;
+// $FlowFixMe[missing-local-annot]
-let getHostNode;
+function createHierarchy(fiberHierarchy) {
-let getHostProps;
-let lastNonHostInstance;
-let getInspectorDataForInstance: (
-  closestInstance: Fiber | null,
-) => InspectorData;
-let getOwnerHierarchy;
-let traverseOwnerTreeUp: (hierarchy: Array<$FlowFixMe>, instance: any) => void;
-
-if (__DEV__ || enableGetInspectorDataForInstanceInProduction) {
-  // $FlowFixMe[missing-local-annot]
-  createHierarchy = function (fiberHierarchy) {
   return fiberHierarchy.map(fiber => ({
     name: getComponentNameFromType(fiber.type),
     getInspectorData: findNodeHandle => {
@@ -67,10 +56,11 @@ if (__DEV__ || enableGetInspectorDataForInstanceInProduction) {
       };
     },
   }));
-  };
+}
 
-  // $FlowFixMe[missing-local-annot]
+// $FlowFixMe[missing-local-annot]
-  getHostNode = function (fiber: Fiber | null, findNodeHandle) {
+function getHostNode(fiber: Fiber | null, findNodeHandle) {
+  if (__DEV__ || enableGetInspectorDataForInstanceInProduction) {
     let hostNode;
     // look for children first for the hostNode
     // as composite fibers do not have a hostNode
@@ -84,20 +74,22 @@ if (__DEV__ || enableGetInspectorDataForInstanceInProduction) {
       fiber = fiber.child;
     }
     return null;
-  };
+  }
+}
 
-  // $FlowFixMe[missing-local-annot]
+// $FlowFixMe[missing-local-annot]
-  getHostProps = function (fiber) {
+function getHostProps(fiber) {
   const host = findCurrentHostFiber(fiber);
   if (host) {
     return host.memoizedProps || emptyObject;
   }
   return emptyObject;
-  };
+}
 
-  getInspectorDataForInstance = function (
+function getInspectorDataForInstance(
   closestInstance: Fiber | null,
-  ): InspectorData {
+): InspectorData {
+  if (__DEV__ || enableGetInspectorDataForInstanceInProduction) {
     // Handle case where user clicks outside of ReactNative
     if (!closestInstance) {
       return {
@@ -123,16 +115,19 @@ if (__DEV__ || enableGetInspectorDataForInstanceInProduction) {
       selectedIndex,
       source,
     };
-  };
+  } else {
+    return (null: any);
+  }
+}
 
-  getOwnerHierarchy = function (instance: any) {
+function getOwnerHierarchy(instance: any) {
   const hierarchy: Array<$FlowFixMe> = [];
   traverseOwnerTreeUp(hierarchy, instance);
   return hierarchy;
-  };
+}
 
-  // $FlowFixMe[missing-local-annot]
+// $FlowFixMe[missing-local-annot]
-  lastNonHostInstance = function (hierarchy) {
+function lastNonHostInstance(hierarchy) {
   for (let i = hierarchy.length - 1; i > 1; i--) {
     const instance = hierarchy[i];
 
@@ -141,28 +136,23 @@ if (__DEV__ || enableGetInspectorDataForInstanceInProduction) {
     }
   }
   return hierarchy[0];
-  };
+}
 
-  // $FlowFixMe[missing-local-annot]
+// $FlowFixMe[missing-local-annot]
-  traverseOwnerTreeUp = function (hierarchy, instance: any): void {
+function traverseOwnerTreeUp(
+  hierarchy: Array<$FlowFixMe>,
+  instance: any,
+): void {
+  if (__DEV__ || enableGetInspectorDataForInstanceInProduction) {
     if (instance) {
       hierarchy.unshift(instance);
       traverseOwnerTreeUp(hierarchy, instance._debugOwner);
     }
-  };
+  }
 }
 
-let getInspectorDataForViewTag: (viewTag: number) => Object;
+function getInspectorDataForViewTag(viewTag: number): Object {
-let getInspectorDataForViewAtPoint: (
+  if (__DEV__) {
-  findNodeHandle: (componentOrHandle: any) => ?number,
-  inspectedView: Object,
-  locationX: number,
-  locationY: number,
-  callback: (viewData: TouchedViewDataAtPoint) => mixed,
-) => void;
-
-if (__DEV__) {
-  getInspectorDataForViewTag = function (viewTag: number): Object {
     const closestInstance = getClosestInstanceFromNode(viewTag);
 
     // Handle case where user clicks outside of ReactNative
@@ -189,15 +179,21 @@ if (__DEV__) {
       selectedIndex,
       source,
     };
-  };
+  } else {
+    throw new Error(
+      'getInspectorDataForViewTag() is not available in production',
+    );
+  }
+}
 
-  getInspectorDataForViewAtPoint = function (
+function getInspectorDataForViewAtPoint(
   findNodeHandle: (componentOrHandle: any) => ?number,
   inspectedView: Object,
   locationX: number,
   locationY: number,
   callback: (viewData: TouchedViewDataAtPoint) => mixed,
-  ): void {
+): void {
+  if (__DEV__) {
     let closestInstance = null;
 
     const fabricInstanceHandle =
@@ -271,25 +267,11 @@ if (__DEV__) {
 
       return;
     }
-  };
+  } else {
-} else {
-  getInspectorDataForViewTag = () => {
-    throw new Error(
-      'getInspectorDataForViewTag() is not available in production',
-    );
-  };
-
-  getInspectorDataForViewAtPoint = (
-    findNodeHandle: (componentOrHandle: any) => ?number,
-    inspectedView: Object,
-    locationX: number,
-    locationY: number,
-    callback: (viewData: TouchedViewDataAtPoint) => mixed,
-  ): void => {
     throw new Error(
       'getInspectorDataForViewAtPoint() is not available in production.',
     );
-  };
+  }
 }
 
 export {

packages/react-native-renderer/src/__mocks__/react-native/Libraries/ReactPrivate/deepDiffer.js

@@ -15,7 +15,7 @@ type Options = {+unsafelyIgnoreFunctions?: boolean};
 /*
  * @returns {bool} true if different, false if equal
  */
-const deepDiffer = function (
+function deepDiffer(
   one: any,
   two: any,
   maxDepthOrOptions: Options | number = -1,
@@ -79,6 +79,6 @@ const deepDiffer = function (
     }
   }
   return false;
-};
+}
 
 module.exports = deepDiffer;

packages/react-native-renderer/src/__mocks__/react-native/Libraries/ReactPrivate/deepFreezeAndThrowOnMutationInDev.js

@@ -9,6 +9,6 @@
 
 // TODO: move into react or fbjs
 
-const deepFreezeAndThrowOnMutationInDev = function () {};
+function deepFreezeAndThrowOnMutationInDev() {}
 
 module.exports = deepFreezeAndThrowOnMutationInDev;

packages/react-native-renderer/src/__mocks__/react-native/Libraries/ReactPrivate/flattenStyle.js

@@ -9,6 +9,6 @@
 
 // TODO: Move flattenStyle into react
 
-const flattenStyle = function () {};
+function flattenStyle() {}
 
 module.exports = flattenStyle;

packages/react-native-renderer/src/legacy-events/EventBatching.js

@@ -25,7 +25,7 @@ let eventQueue: ?(Array<ReactSyntheticEvent> | ReactSyntheticEvent) = null;
  * @param {?object} event Synthetic event to be dispatched.
  * @private
  */
-const executeDispatchesAndRelease = function (event: ReactSyntheticEvent) {
+function executeDispatchesAndRelease(event: ReactSyntheticEvent) {
   if (event) {
     executeDispatchesInOrder(event);
 
@@ -33,11 +33,11 @@ const executeDispatchesAndRelease = function (event: ReactSyntheticEvent) {
       event.constructor.release(event);
     }
   }
-};
+}
 // $FlowFixMe[missing-local-annot]
-const executeDispatchesAndReleaseTopLevel = function (e) {
+function executeDispatchesAndReleaseTopLevel(e) {
   return executeDispatchesAndRelease(e);
-};
+}
 
 export function runEventsInBatch(
   events: Array<ReactSyntheticEvent> | ReactSyntheticEvent | null,

packages/react-native-renderer/src/legacy-events/EventPluginUtils.js

@@ -30,9 +30,8 @@ export function setComponentTree(
   }
 }
 
-let validateEventDispatches;
+function validateEventDispatches(event) {
-if (__DEV__) {
+  if (__DEV__) {
-  validateEventDispatches = function (event) {
     const dispatchListeners = event._dispatchListeners;
     const dispatchInstances = event._dispatchInstances;
 
@@ -53,7 +52,7 @@ if (__DEV__) {
     if (instancesIsArr !== listenersIsArr || instancesLen !== listenersLen) {
       console.error('EventPluginUtils: Invalid `event`.');
     }
-  };
+  }
 }
 
 /**

packages/react-native-renderer/src/legacy-events/ResponderEventPlugin.js

@@ -44,7 +44,7 @@ let responderInst = null;
  */
 let trackedTouchCount = 0;
 
-const changeResponder = function (nextResponderInst, blockHostResponder) {
+function changeResponder(nextResponderInst, blockHostResponder) {
   const oldResponderInst = responderInst;
   responderInst = nextResponderInst;
   if (ResponderEventPlugin.GlobalResponderHandler !== null) {
@@ -54,7 +54,7 @@ const changeResponder = function (nextResponderInst, blockHostResponder) {
       blockHostResponder,
     );
   }
-};
+}
 
 const eventTypes = {
   /**

packages/react-reconciler/src/ReactFiber.js

@@ -224,7 +224,7 @@ function FiberNode(
 //    is faster.
 // 5) It should be easy to port this to a C struct and keep a C implementation
 //    compatible.
-const createFiber = function (
+function createFiber(
   tag: WorkTag,
   pendingProps: mixed,
   key: null | string,
@@ -232,7 +232,7 @@ const createFiber = function (
 ): Fiber {
   // $FlowFixMe: the shapes are exact here but Flow doesn't like constructors
   return new FiberNode(tag, pendingProps, key, mode);
-};
+}
 
 function shouldConstruct(Component: Function) {
   const prototype = Component.prototype;

packages/react-reconciler/src/ReactFiberClassComponent.js

@@ -85,11 +85,10 @@ let didWarnAboutUninitializedState;
 let didWarnAboutGetSnapshotBeforeUpdateWithoutDidUpdate;
 let didWarnAboutLegacyLifecyclesAndDerivedState;
 let didWarnAboutUndefinedDerivedState;
-let warnOnUndefinedDerivedState;
-let warnOnInvalidCallback;
 let didWarnAboutDirectlyAssigningPropsToState;
 let didWarnAboutContextTypeAndContextTypes;
 let didWarnAboutInvalidateContextType;
+let didWarnOnInvalidCallback;
 
 if (__DEV__) {
   didWarnAboutStateAssignmentForComponent = new Set<string>();
@@ -100,38 +99,7 @@ if (__DEV__) {
   didWarnAboutUndefinedDerivedState = new Set<string>();
   didWarnAboutContextTypeAndContextTypes = new Set<string>();
   didWarnAboutInvalidateContextType = new Set<string>();
-
+  didWarnOnInvalidCallback = new Set<string>();
-  const didWarnOnInvalidCallback = new Set<string>();
-
-  warnOnInvalidCallback = function (callback: mixed, callerName: string) {
-    if (callback === null || typeof callback === 'function') {
-      return;
-    }
-    const key = callerName + '_' + (callback: any);
-    if (!didWarnOnInvalidCallback.has(key)) {
-      didWarnOnInvalidCallback.add(key);
-      console.error(
-        '%s(...): Expected the last optional `callback` argument to be a ' +
-          'function. Instead received: %s.',
-        callerName,
-        callback,
-      );
-    }
-  };
-
-  warnOnUndefinedDerivedState = function (type: any, partialState: any) {
-    if (partialState === undefined) {
-      const componentName = getComponentNameFromType(type) || 'Component';
-      if (!didWarnAboutUndefinedDerivedState.has(componentName)) {
-        didWarnAboutUndefinedDerivedState.add(componentName);
-        console.error(
-          '%s.getDerivedStateFromProps(): A valid state object (or null) must be returned. ' +
-            'You have returned undefined.',
-          componentName,
-        );
-      }
-    }
-  };
 
   // This is so gross but it's at least non-critical and can be removed if
   // it causes problems. This is meant to give a nicer error message for
@@ -154,6 +122,40 @@ if (__DEV__) {
   Object.freeze(fakeInternalInstance);
 }
 
+function warnOnInvalidCallback(callback: mixed, callerName: string) {
+  if (__DEV__) {
+    if (callback === null || typeof callback === 'function') {
+      return;
+    }
+    const key = callerName + '_' + (callback: any);
+    if (!didWarnOnInvalidCallback.has(key)) {
+      didWarnOnInvalidCallback.add(key);
+      console.error(
+        '%s(...): Expected the last optional `callback` argument to be a ' +
+          'function. Instead received: %s.',
+        callerName,
+        callback,
+      );
+    }
+  }
+}
+
+function warnOnUndefinedDerivedState(type: any, partialState: any) {
+  if (__DEV__) {
+    if (partialState === undefined) {
+      const componentName = getComponentNameFromType(type) || 'Component';
+      if (!didWarnAboutUndefinedDerivedState.has(componentName)) {
+        didWarnAboutUndefinedDerivedState.add(componentName);
+        console.error(
+          '%s.getDerivedStateFromProps(): A valid state object (or null) must be returned. ' +
+            'You have returned undefined.',
+          componentName,
+        );
+      }
+    }
+  }
+}
+
 function applyDerivedStateFromProps(
   workInProgress: Fiber,
   ctor: any,

packages/react-reconciler/src/ReactFiberCommitWork.js

@@ -253,10 +253,7 @@ export function reportUncaughtErrorInDEV(error: mixed) {
   }
 }
 
-const callComponentWillUnmountWithTimer = function (
+function callComponentWillUnmountWithTimer(current: Fiber, instance: any) {
-  current: Fiber,
-  instance: any,
-) {
   instance.props = current.memoizedProps;
   instance.state = current.memoizedState;
   if (shouldProfile(current)) {
@@ -269,7 +266,7 @@ const callComponentWillUnmountWithTimer = function (
   } else {
     instance.componentWillUnmount();
   }
-};
+}
 
 // Capture errors so they don't interrupt unmounting.
 function safelyCallComponentWillUnmount(

packages/react-server/src/ReactFizzClassComponent.js

@@ -24,11 +24,10 @@ let didWarnAboutUninitializedState;
 let didWarnAboutGetSnapshotBeforeUpdateWithoutDidUpdate;
 let didWarnAboutLegacyLifecyclesAndDerivedState;
 let didWarnAboutUndefinedDerivedState;
-let warnOnUndefinedDerivedState;
-let warnOnInvalidCallback;
 let didWarnAboutDirectlyAssigningPropsToState;
 let didWarnAboutContextTypeAndContextTypes;
 let didWarnAboutInvalidateContextType;
+let didWarnOnInvalidCallback;
 
 if (__DEV__) {
   didWarnAboutUninitializedState = new Set<string>();
@@ -38,10 +37,11 @@ if (__DEV__) {
   didWarnAboutUndefinedDerivedState = new Set<string>();
   didWarnAboutContextTypeAndContextTypes = new Set<mixed>();
   didWarnAboutInvalidateContextType = new Set<mixed>();
+  didWarnOnInvalidCallback = new Set<string>();
+}
 
-  const didWarnOnInvalidCallback = new Set<string>();
+function warnOnInvalidCallback(callback: mixed, callerName: string) {
-
+  if (__DEV__) {
-  warnOnInvalidCallback = function (callback: mixed, callerName: string) {
     if (callback === null || typeof callback === 'function') {
       return;
     }
@@ -55,9 +55,11 @@ if (__DEV__) {
         callback,
       );
     }
-  };
+  }
+}
 
-  warnOnUndefinedDerivedState = function (type: any, partialState: any) {
+function warnOnUndefinedDerivedState(type: any, partialState: any) {
+  if (__DEV__) {
     if (partialState === undefined) {
       const componentName = getComponentNameFromType(type) || 'Component';
       if (!didWarnAboutUndefinedDerivedState.has(componentName)) {
@@ -69,7 +71,7 @@ if (__DEV__) {
         );
       }
     }
-  };
+  }
 }
 
 function warnNoop(

packages/react/src/ReactElement.js

@@ -145,7 +145,7 @@ function warnIfStringRefCannotBeAutoConverted(config) {
  * indicating filename, line number, and/or other information.
  * @internal
  */
-const ReactElement = function (type, key, ref, self, source, owner, props) {
+function ReactElement(type, key, ref, self, source, owner, props) {
   const element = {
     // This tag allows us to uniquely identify this as a React Element
     $$typeof: REACT_ELEMENT_TYPE,
@@ -199,7 +199,7 @@ const ReactElement = function (type, key, ref, self, source, owner, props) {
   }
 
   return element;
-};
+}
 
 /**
  * https://github.com/reactjs/rfcs/pull/107

packages/react/src/jsx/ReactJSXElement.js

@@ -145,7 +145,7 @@ function defineRefPropWarningGetter(props, displayName) {
  * indicating filename, line number, and/or other information.
  * @internal
  */
-const ReactElement = function (type, key, ref, self, source, owner, props) {
+function ReactElement(type, key, ref, self, source, owner, props) {
   const element = {
     // This tag allows us to uniquely identify this as a React Element
     $$typeof: REACT_ELEMENT_TYPE,
@@ -199,7 +199,7 @@ const ReactElement = function (type, key, ref, self, source, owner, props) {
   }
 
   return element;
-};
+}
 
 /**
  * https://github.com/reactjs/rfcs/pull/107

packages/shared/forks/invokeGuardedCallbackImpl.www.js

@@ -16,7 +16,7 @@ if (typeof ReactFbErrorUtils.invokeGuardedCallback !== 'function') {
   );
 }
 
-const invokeGuardedCallbackImpl = function <A, B, C, D, E, F, Context>(
+function invokeGuardedCallbackImpl<A, B, C, D, E, F, Context>(
   name: string | null,
   func: (a: A, b: B, c: C, d: D, e: E, f: F) => mixed,
   context: Context,
@@ -29,6 +29,6 @@ const invokeGuardedCallbackImpl = function <A, B, C, D, E, F, Context>(
 ) {
   // This will call `this.onError(err)` if an error was caught.
   ReactFbErrorUtils.invokeGuardedCallback.apply(this, arguments);
-};
+}
 
 export default invokeGuardedCallbackImpl;