Migrate Babel from Flow to TypeScript (except Babel parser) (#11578)

Co-authored-by: Nicolò Ribaudo <nicolo.ribaudo@gmail.com>

.eslintrc.cjs

@@ -84,7 +84,7 @@ module.exports = {
       ],
       excludedFiles: [
         // @babel/register is the require() hook, so it will always be CJS-based
-        "packages/babel-register/**/*.js",
+        "packages/babel-register/**/*.{js,ts}",
       ],
       rules: {
         "no-restricted-globals": ["error", ...cjsGlobals],

Gulpfile.mjs

@@ -61,7 +61,7 @@ function mapSrcToLib(srcPath) {
 function mapToDts(packageName) {
   return packageName.replace(
     /(?<=\\|\/|^)(packages|eslint|codemods)(?=\\|\/)/,
-    "dts"
+    "dts/$1"
   );
 }
 

eslint/babel-eslint-plugin/src/rules/semi.ts

@@ -47,7 +47,7 @@ function isOneLinerBlock(context, node) {
   );
 }
 
-function report(context, node, missing) {
+function report(context, node, missing?) {
   const lastToken = context.getSourceCode().getLastToken(node);
 
   let message,

packages/babel-core/src/config/plugin.ts

@@ -2,13 +2,13 @@ import type { PluginObject } from "./validation/plugins";
 
 export default class Plugin {
   key: string | undefined | null;
-  manipulateOptions: ((options: unknown, parserOpts: unknown) => void) | void;
+  manipulateOptions?: (options: unknown, parserOpts: unknown) => void;
-  post: Function | void;
+  post?: Function;
-  pre: Function | void;
+  pre?: Function;
   visitor: {};
 
-  parserOverride: Function | void;
+  parserOverride?: Function;
-  generatorOverride: Function | void;
+  generatorOverride?: Function;
 
   options: {};
 

packages/babel-generator/src/buffer.ts

@@ -38,7 +38,7 @@ export default class Buffer {
    * Get the final string output from the buffer, along with the sourcemap if one exists.
    */
 
-  get(): any {
+  get() {
     this._flush();
 
     const map = this._map;

packages/babel-generator/src/generators/jsx.ts

@@ -67,7 +67,7 @@ export function JSXElement(this: Printer, node: t.JSXElement) {
   if (open.selfClosing) return;
 
   this.indent();
-  for (const child of node.children as Array<any>) {
+  for (const child of node.children) {
     this.print(child, node);
   }
   this.dedent();
@@ -109,7 +109,7 @@ export function JSXFragment(this: Printer, node: t.JSXFragment) {
   this.print(node.openingFragment, node);
 
   this.indent();
-  for (const child of node.children as Array<any>) {
+  for (const child of node.children) {
     this.print(child, node);
   }
   this.dedent();

packages/babel-generator/src/generators/statements.ts

@@ -267,7 +267,7 @@ export function VariableDeclaration(
   let hasInits = false;
   // don't add whitespace to loop heads
   if (!isFor(parent)) {
-    for (const declar of node.declarations as Array<any>) {
+    for (const declar of node.declarations) {
       if (declar.init) {
         // has an init so let's split it up over multiple lines
         hasInits = true;

packages/babel-generator/src/index.ts

@@ -246,7 +246,7 @@ export default function generate(
   ast: t.Node,
   opts?: GeneratorOptions,
   code?: string | { [filename: string]: string },
-): any {
+) {
   const gen = new Generator(ast, opts, code);
   return gen.generate();
 }

packages/babel-generator/src/printer.ts

@@ -375,7 +375,7 @@ class Printer {
    *  `undefined` will be returned and not `foo` due to the terminator.
    */
 
-  startTerminatorless(isLabel: boolean = false): any {
+  startTerminatorless(isLabel: boolean = false) {
     if (isLabel) {
       this._noLineTerminator = true;
       return null;

packages/babel-helper-builder-binary-assignment-operator-visitor/src/index.ts

@@ -1,15 +1,17 @@
 import explode from "@babel/helper-explode-assignable-expression";
 import { assignmentExpression, sequenceExpression } from "@babel/types";
+import type { Visitor } from "@babel/traverse";
 
-export default function (opts: { build: Function, operator: string }): Object {
+export default function (opts: { build: Function; operator: string }) {
   const { build, operator } = opts;
 
-  return {
+  const visitor: Visitor = {
     AssignmentExpression(path) {
       const { node, scope } = path;
       if (node.operator !== operator + "=") return;
 
       const nodes = [];
+      // @ts-expect-error todo(flow->ts)
       const exploded = explode(node.left, nodes, this, scope);
       nodes.push(
         assignmentExpression(
@@ -28,4 +30,5 @@ export default function (opts: { build: Function, operator: string }): Object {
       }
     },
   };
+  return visitor;
 }

packages/babel-helper-builder-react-jsx/package.json

@@ -17,6 +17,9 @@
     "@babel/helper-annotate-as-pure": "workspace:^",
     "@babel/types": "workspace:^"
   },
+  "devDependencies": {
+    "@babel/traverse": "workspace:^"
+  },
   "engines": {
     "node": ">=6.9.0"
   },

packages/babel-helper-builder-react-jsx/src/index.ts

@@ -24,17 +24,19 @@ import {
   thisExpression,
 } from "@babel/types";
 import annotateAsPure from "@babel/helper-annotate-as-pure";
+import type { Visitor } from "@babel/traverse";
 
 type ElementState = {
-  tagExpr: Object, // tag node
+  tagExpr: any; // tag node,
-  tagName: ?string, // raw string tag name
+  tagName: string | undefined | null; // raw string tag name,
-  args: Array<Object>, // array of call arguments
+  args: Array<any>; // array of call arguments,
-  call?: Object, // optional call property that can be set to override the call expression returned
+  call?: any; // optional call property that can be set to override the call expression returned,
-  pure: boolean, // true if the element can be marked with a #__PURE__ annotation
+  pure: boolean; // true if the element can be marked with a #__PURE__ annotation
+  callee?: any;
 };
 
 export default function (opts) {
-  const visitor = {};
+  const visitor: Visitor = {};
 
   visitor.JSXNamespacedName = function (path) {
     if (opts.throwIfNamespace) {
@@ -81,6 +83,7 @@ You can set \`throwIfNamespace: false\` to bypass this warning.`,
       if (node.name === "this" && isReferenced(node, parent)) {
         return thisExpression();
       } else if (isValidIdentifier(node.name, false)) {
+        // @ts-expect-error todo(flow->ts) avoid type unsafe mutations
         node.type = "Identifier";
       } else {
         return stringLiteral(node.name);
@@ -152,6 +155,7 @@ You can set \`throwIfNamespace: false\` to bypass this warning.`,
     if (isIdentifier(tagExpr)) {
       tagName = tagExpr.name;
     } else if (isLiteral(tagExpr)) {
+      // @ts-expect-error todo(flow->ts) NullLiteral
       tagName = tagExpr.value;
     }
 

packages/babel-helper-create-class-features-plugin/src/index.ts

@@ -19,6 +19,7 @@ import {
   isLoose,
 } from "./features";
 import { assertFieldTransformed } from "./typescript";
+import type { ParserOptions } from "@babel/parser";
 
 export { FEATURES, enableFeature, injectInitialization };
 
@@ -38,7 +39,7 @@ interface Options {
   feature: number;
   loose?: boolean;
   // same as PluginObject.manipulateOptions
-  manipulateOptions: (options: unknown, parserOpts: unknown) => void;
+  manipulateOptions: (options: unknown, parserOpts: ParserOptions) => void;
   // TODO(flow->ts): change to babel api
   api?: { assumption: (key?: string) => boolean | undefined };
 }

packages/babel-helper-define-map/src/index.ts

@@ -18,7 +18,7 @@ import {
   toKeyAlias,
 } from "@babel/types";
 
-function toKind(node: Object) {
+function toKind(node: any) {
   if (isClassMethod(node) || isObjectMethod(node)) {
     if (node.kind === "get" || node.kind === "set") {
       return node.kind;
@@ -30,18 +30,12 @@ function toKind(node: Object) {
 
 const has = Function.prototype.call.bind(Object.prototype.hasOwnProperty);
 
-export function push(
+export function push(mutatorMap: any, node: any, kind: string, file, scope?) {
-  mutatorMap: Object,
-  node: Object,
-  kind: string,
-  file,
-  scope?,
-): Object {
   const alias = toKeyAlias(node);
 
   //
 
-  let map = {};
+  let map = {} as any;
   if (has(mutatorMap, alias)) map = mutatorMap[alias];
   mutatorMap[alias] = map;
 
@@ -79,6 +73,7 @@ export function push(
   } else if (isObjectMethod(node) || isClassMethod(node)) {
     value = functionExpression(
       null,
+      // @ts-expect-error todo(flow->ts) TSParameterProperty is not assignable to parameter of type 'Identifier | RestElement | Pattern'.
       node.params,
       node.body,
       node.generator,
@@ -110,7 +105,7 @@ export function push(
   return map;
 }
 
-export function hasComputed(mutatorMap: Object): boolean {
+export function hasComputed(mutatorMap: any): boolean {
   for (const key of Object.keys(mutatorMap)) {
     if (mutatorMap[key]._computed) {
       return true;
@@ -119,7 +114,7 @@ export function hasComputed(mutatorMap: Object): boolean {
   return false;
 }
 
-export function toComputedObjectFromClass(obj: Object): Object {
+export function toComputedObjectFromClass(obj: any) {
   const objExpr = arrayExpression([]);
 
   for (let i = 0; i < obj.properties.length; i++) {
@@ -134,7 +129,7 @@ export function toComputedObjectFromClass(obj: Object): Object {
   return objExpr;
 }
 
-export function toClassObject(mutatorMap: Object): Object {
+export function toClassObject(mutatorMap: any) {
   const objExpr = objectExpression([]);
 
   Object.keys(mutatorMap).forEach(function (mutatorMapKey) {
@@ -160,7 +155,7 @@ export function toClassObject(mutatorMap: Object): Object {
   return objExpr;
 }
 
-export function toDefineObject(mutatorMap: Object): Object {
+export function toDefineObject(mutatorMap: any) {
   Object.keys(mutatorMap).forEach(function (key) {
     const map = mutatorMap[key];
     if (map.value) map.writable = booleanLiteral(true);

packages/babel-helper-module-transforms/src/normalize-and-load-metadata.ts

@@ -482,8 +482,7 @@ function getLocalExportMetadata(
       (initializeReexports || !child.node.source)
     ) {
       if (child.node.declaration) {
-        // todo: flow->ts babel-types node field types
+        const declaration = child.get("declaration");
-        const declaration = child.get("declaration") as NodePath;
         const ids = declaration.getOuterBindingIdentifierPaths();
         Object.keys(ids).forEach(name => {
           if (name === "__esModule") {

packages/babel-helper-plugin-utils/src/index.ts

@@ -1,4 +1,19 @@
-export function declare(builder) {
+export function declare<
+  Args extends
+    | [any]
+    | [any, any?]
+    | [any, any?, any?]
+    | [any, any]
+    | [any, any, any?]
+    | [any, any, any],
+  Builder extends (...args: Args) => any,
+>(
+  builder: Builder,
+  // todo(flow->ts) maybe add stricter type for returned function
+  // reason any is there to not expose exact implementation details in type
+  // example of issue with this packages/babel-preset-typescript/src/index.ts
+): Builder extends (...args: infer A) => any ? (...args: A) => any : never {
+  // @ts-ignore
   return (api, options, dirname) => {
     let clonedApi;
 
@@ -10,6 +25,7 @@ export function declare(builder) {
       clonedApi[name] = apiPolyfills[name](clonedApi);
     }
 
+    // @ts-ignore
     return builder(clonedApi ?? api, options || {}, dirname);
   };
 }
@@ -101,12 +117,9 @@ function throwVersionError(range, version) {
     Error.stackTraceLimit = limit;
   }
 
-  throw Object.assign(
+  throw Object.assign(err, {
-    err,
-    ({
     code: "BABEL_VERSION_UNSUPPORTED",
     version,
     range,
-    }: any),
+  } as any);
-  );
 }

packages/babel-helper-remap-async-to-generator/src/index.ts

@@ -30,8 +30,11 @@ const awaitVisitor = {
 };
 
 export default function (
-  path: NodePath,
+  path: NodePath<any>,
-  helpers: { wrapAsync: Object, wrapAwait: Object },
+  helpers: {
+    wrapAsync: any;
+    wrapAwait?: any;
+  },
   noNewArrows?: boolean,
 ) {
   path.traverse(awaitVisitor, {

packages/babel-helper-wrap-function/src/index.ts

@@ -9,6 +9,7 @@ import {
   isRestElement,
   returnStatement,
 } from "@babel/types";
+import type * as t from "@babel/types";
 
 const buildAnonymousExpressionWrapper = template.expression(`
   (function () {
@@ -37,7 +38,10 @@ const buildDeclarationWrapper = template(`
   }
 `);
 
-function classOrObjectMethod(path: NodePath, callId: Object) {
+function classOrObjectMethod(
+  path: NodePath<t.ClassMethod | t.ClassPrivateMethod | t.ObjectMethod>,
+  callId: any,
+) {
   const node = path.node;
   const body = node.body;
 
@@ -57,12 +61,12 @@ function classOrObjectMethod(path: NodePath, callId: Object) {
   node.generator = false;
 
   // Unwrap the wrapper IIFE's environment so super and this and such still work.
-  path
+  (
-    .get("body.body.0.argument.callee.arguments.0")
+    path.get("body.body.0.argument.callee.arguments.0") as NodePath
-    .unwrapFunctionEnvironment();
+  ).unwrapFunctionEnvironment();
 }
 
-function plainFunction(path: NodePath, callId: Object, noNewArrows: boolean) {
+function plainFunction(path: NodePath<any>, callId: any, noNewArrows: boolean) {
   const node = path.node;
   const isDeclaration = path.isFunctionDeclaration();
   const functionId = node.id;
@@ -109,6 +113,7 @@ function plainFunction(path: NodePath, callId: Object, noNewArrows: boolean) {
     path.replaceWith(container[0]);
     path.insertAfter(container[1]);
   } else {
+    // @ts-expect-error todo(flow->ts) separate `wrapper` for `isDeclaration` and `else` branches
     const retFunction = container.callee.body.body[1].argument;
     if (!functionId) {
       nameFunction({
@@ -120,6 +125,7 @@ function plainFunction(path: NodePath, callId: Object, noNewArrows: boolean) {
 
     if (!retFunction || retFunction.id || node.params.length) {
       // we have an inferred function id or params so we need this wrapper
+      // @ts-expect-error todo(flow->ts) separate `wrapper` for `isDeclaration` and `else` branches
       path.replaceWith(container);
     } else {
       // we can omit this wrapper as the conditions it protects for do not apply
@@ -130,7 +136,7 @@ function plainFunction(path: NodePath, callId: Object, noNewArrows: boolean) {
 
 export default function wrapFunction(
   path: NodePath,
-  callId: Object,
+  callId: any,
   // TODO(Babel 8): Consider defaulting to false for spec compliancy
   noNewArrows: boolean = true,
 ) {

packages/babel-node/src/_babel-node.ts

@@ -67,6 +67,7 @@ program.option(
 program.option("-w, --plugins [string]", "", collect);
 program.option("-b, --presets [string]", "", collect);
 
+declare const PACKAGE_JSON: { name: string; version: string };
 program.version(PACKAGE_JSON.version);
 program.usage("[options] [ -e script | script.js ] [arguments]");
 program.parse(process.argv);
@@ -144,17 +145,26 @@ if (program.eval || program.print) {
   let code = program.eval;
   if (!code || code === true) code = program.print;
 
+  // @ts-expect-error todo(flow->ts)
   global.__filename = "[eval]";
+  // @ts-expect-error todo(flow->ts)
   global.__dirname = process.cwd();
 
+  // @ts-expect-error todo(flow->ts)
   const module = new Module(global.__filename);
+  // @ts-expect-error todo(flow->ts)
   module.filename = global.__filename;
+  // @ts-expect-error todo(flow->ts)
   module.paths = Module._nodeModulePaths(global.__dirname);
 
+  // @ts-expect-error todo(flow->ts)
   global.exports = module.exports;
+  // @ts-expect-error todo(flow->ts)
   global.module = module;
+  // @ts-expect-error todo(flow->ts)
   global.require = module.require.bind(module);
 
+  // @ts-expect-error todo(flow->ts)
   const result = _eval(code, global.__filename);
   if (program.print) {
     const output = typeof result === "string" ? result : inspect(result);

packages/babel-plugin-proposal-async-generator-functions/src/for-await.ts

@@ -61,6 +61,7 @@ export default function (path, { getAsyncIterator }) {
   });
 
   // remove async function wrapper
+  // @ts-expect-error todo(flow->ts) improve type annotation for buildForAwait
   template = template.body.body;
 
   const isLabeledParent = t.isLabeledStatement(parent);

packages/babel-plugin-proposal-class-static-block/package.json

@@ -28,7 +28,9 @@
   },
   "devDependencies": {
     "@babel/core": "workspace:^",
-    "@babel/helper-plugin-test-runner": "workspace:^"
+    "@babel/helper-plugin-test-runner": "workspace:^",
+    "@babel/traverse": "workspace:^",
+    "@babel/types": "workspace:^"
   },
   "homepage": "https://babel.dev/docs/en/next/babel-plugin-proposal-class-static-block",
   "engines": {

packages/babel-plugin-proposal-class-static-block/src/index.ts

@@ -6,11 +6,13 @@ import {
   FEATURES,
 } from "@babel/helper-create-class-features-plugin";
 
+import type * as t from "@babel/types";
+import type { NodePath } from "@babel/traverse";
 /**
  * Generate a uid that is not in `denyList`
  *
  * @param {*} scope
- * @param {Set<string>} a deny list that the generated uid should avoid
+ * @param {Set<string>} denyList a deny list that the generated uid should avoid
  * @returns
  */
 function generateUid(scope, denyList: Set<string>) {
@@ -41,9 +43,9 @@ export default declare(({ types: t, template, assertVersion }) => {
       // Run on ClassBody and not on class so that if @babel/helper-create-class-features-plugin
       // is enabled it can generte optimized output without passing from the intermediate
       // private fields representation.
-      ClassBody(classBody: NodePath<Class>) {
+      ClassBody(classBody: NodePath<t.ClassBody>) {
         const { scope } = classBody;
-        const privateNames = new Set();
+        const privateNames = new Set<string>();
         const body = classBody.get("body");
         for (const path of body) {
           if (path.isPrivate()) {
@@ -60,7 +62,9 @@ export default declare(({ types: t, template, assertVersion }) => {
           path.replaceWith(
             t.classPrivateProperty(
               staticBlockRef,
-              template.expression.ast`(() => { ${path.node.body} })()`,
+              template.expression.ast`(() => { ${
+                (path.node as t.StaticBlock).body
+              } })()`,
               [],
               /* static */ true,
             ),

packages/babel-plugin-proposal-decorators/package.json

@@ -30,6 +30,7 @@
   "devDependencies": {
     "@babel/core": "workspace:^",
     "@babel/helper-plugin-test-runner": "workspace:^",
+    "@babel/traverse": "workspace:^",
     "babel-plugin-polyfill-es-shims": "^0.6.0",
     "object.getownpropertydescriptors": "^2.1.1"
   },

packages/babel-plugin-proposal-decorators/src/transformer-legacy.ts

@@ -1,18 +1,19 @@
 // Fork of https://github.com/loganfsmyth/babel-plugin-proposal-decorators-legacy
 
 import { template, types as t } from "@babel/core";
+import type { Visitor } from "@babel/traverse";
 
 const buildClassDecorator = template(`
   DECORATOR(CLASS_REF = INNER) || CLASS_REF;
-`);
+`) as (replacements: { DECORATOR; CLASS_REF; INNER }) => t.ExpressionStatement;
 
 const buildClassPrototype = template(`
   CLASS_REF.prototype;
-`);
+`) as (replacements: { CLASS_REF }) => t.ExpressionStatement;
 
 const buildGetDescriptor = template(`
     Object.getOwnPropertyDescriptor(TARGET, PROPERTY);
-`);
+`) as (replacements: { TARGET; PROPERTY }) => t.ExpressionStatement;
 
 const buildGetObjectInitializer = template(`
     (TEMP = Object.getOwnPropertyDescriptor(TARGET, PROPERTY), (TEMP = TEMP ? TEMP.value : undefined), {
@@ -23,7 +24,7 @@ const buildGetObjectInitializer = template(`
             return TEMP;
         }
     })
-`);
+`) as (replacements: { TEMP; TARGET; PROPERTY }) => t.ExpressionStatement;
 
 const WARNING_CALLS = new WeakSet();
 
@@ -241,6 +242,7 @@ export default {
         replacement,
         t.exportNamedDeclaration(null, [
           t.exportSpecifier(
+            // @ts-expect-error todo(flow->ts) might be add more specific return type for decoratedClassToExpression
             t.cloneNode(replacement.declarations[0].id),
             t.identifier("default"),
           ),
@@ -263,7 +265,7 @@ export default {
     // class decorators, and a second pass to process method decorators.
     const decoratedClass =
       applyEnsureOrdering(path) ||
-      applyClassDecorators(path, state) ||
+      applyClassDecorators(path) ||
       applyMethodDecorators(path, state);
 
     if (decoratedClass) path.replaceWith(decoratedClass);
@@ -280,12 +282,17 @@ export default {
 
     path.replaceWith(
       t.callExpression(state.addHelper("initializerDefineProperty"), [
+        // @ts-expect-error todo(flow->ts) typesafe NodePath.get
         t.cloneNode(path.get("left.object").node),
         t.stringLiteral(
+          // @ts-expect-error todo(flow->ts) typesafe NodePath.get
           path.get("left.property").node.name ||
+            // @ts-expect-error todo(flow->ts) typesafe NodePath.get
             path.get("left.property").node.value,
         ),
+        // @ts-expect-error todo(flow->ts)
         t.cloneNode(path.get("right.arguments")[0].node),
+        // @ts-expect-error todo(flow->ts)
         t.cloneNode(path.get("right.arguments")[1].node),
       ]),
     );
@@ -297,6 +304,7 @@ export default {
 
     // If the class properties plugin isn't enabled, this line will add an unused helper
     // to the code. It's not ideal, but it's ok since the configuration is not valid anyway.
+    // @ts-expect-error todo(flow->ts) check that `callee` is Identifier
     if (path.node.callee.name !== state.addHelper("defineProperty").name) {
       return;
     }
@@ -305,9 +313,11 @@ export default {
       t.callExpression(state.addHelper("initializerDefineProperty"), [
         t.cloneNode(path.get("arguments")[0].node),
         t.cloneNode(path.get("arguments")[1].node),
+        // @ts-expect-error todo(flow->ts)
         t.cloneNode(path.get("arguments.2.arguments")[0].node),
+        // @ts-expect-error todo(flow->ts)
         t.cloneNode(path.get("arguments.2.arguments")[1].node),
       ]),
     );
   },
-};
+} as Visitor<any>;

packages/babel-plugin-proposal-dynamic-import/src/index.ts

@@ -16,6 +16,8 @@ the @babel/plugin-syntax-dynamic-import plugin and let your
 bundler handle dynamic imports.
 `;
 
+declare const PACKAGE_JSON: { name: string; version: string };
+
 export default declare(api => {
   api.assertVersion(7);
 

packages/babel-plugin-proposal-logical-assignment-operators/src/index.ts

@@ -34,6 +34,7 @@ export default declare(api => {
               lhs.property = t.assignmentExpression(
                 "=",
                 t.cloneNode(memo),
+                // @ts-expect-error todo(flow->ts): property can be t.PrivateName
                 property,
               );
             }

packages/babel-plugin-proposal-numeric-separator/package.json

@@ -25,7 +25,9 @@
   },
   "devDependencies": {
     "@babel/core": "workspace:^",
-    "@babel/helper-plugin-test-runner": "workspace:^"
+    "@babel/helper-plugin-test-runner": "workspace:^",
+    "@babel/traverse": "workspace:^",
+    "@babel/types": "workspace:^"
   },
   "engines": {
     "node": ">=6.9.0"

packages/babel-plugin-proposal-numeric-separator/src/index.ts

@@ -1,5 +1,7 @@
 import { declare } from "@babel/helper-plugin-utils";
 import syntaxNumericSeparator from "@babel/plugin-syntax-numeric-separator";
+import type { NodePath } from "@babel/traverse";
+import type * as t from "@babel/types";
 
 /**
  * Given a bigIntLiteral or NumericLiteral, remove numeric
@@ -7,9 +9,11 @@ import syntaxNumericSeparator from "@babel/plugin-syntax-numeric-separator";
  *
  * @param {NodePath<BigIntLiteral | NumericLiteral>} { node }: A Babel AST node path
  */
-function remover({ node }: NodePath<BigIntLiteral | NumericLiteral>) {
+function remover({ node }: NodePath<t.BigIntLiteral | t.NumericLiteral>) {
   const { extra } = node;
+  // @ts-expect-error todo(flow->ts)
   if (extra?.raw?.includes("_")) {
+    // @ts-expect-error todo(flow->ts)
     extra.raw = extra.raw.replace(/_/g, "");
   }
 }

packages/babel-plugin-proposal-optional-chaining/package.json

@@ -27,7 +27,8 @@
   "devDependencies": {
     "@babel/core": "workspace:^",
     "@babel/helper-plugin-test-runner": "workspace:^",
-    "@babel/plugin-transform-block-scoping": "workspace:^"
+    "@babel/plugin-transform-block-scoping": "workspace:^",
+    "@babel/traverse": "workspace:^"
   },
   "engines": {
     "node": ">=6.9.0"

packages/babel-plugin-proposal-optional-chaining/src/transform.ts

@@ -1,4 +1,5 @@
 import { types as t, template } from "@babel/core";
+import type { NodePath } from "@babel/traverse";
 import {
   skipTransparentExprWrapperNodes,
   skipTransparentExprWrappers,
@@ -48,7 +49,7 @@ export function transform(
   {
     pureGetters,
     noDocumentAll,
-  }: { pureGetters: boolean, noDocumentAll: boolean },
+  }: { pureGetters: boolean; noDocumentAll: boolean },
 ) {
   const { scope } = path;
   // maybeWrapped points to the outermost transparent expression wrapper
@@ -69,7 +70,7 @@ export function transform(
   // Replace `function (a, x = a.b?.c) {}` to `function (a, x = (() => a.b?.c)() ){}`
   // so the temporary variable can be injected in correct scope
   if (scope.path.isPattern() && needsMemoize(optionalPath)) {
-    path.replaceWith(template.ast`(() => ${path.node})()`);
+    path.replaceWith(template.ast`(() => ${path.node})()` as t.Statement);
     // The injected optional chain will be queued and eventually transformed when visited
     return;
   }
@@ -83,15 +84,19 @@ export function transform(
     }
 
     if (optionalPath.isOptionalMemberExpression()) {
+      // @ts-expect-error todo(flow->ts) avoid changing more type
       optionalPath.node.type = "MemberExpression";
+      // @ts-expect-error todo(flow->ts)
       optionalPath = skipTransparentExprWrappers(optionalPath.get("object"));
     } else if (optionalPath.isOptionalCallExpression()) {
+      // @ts-expect-error todo(flow->ts) avoid changing more type
       optionalPath.node.type = "CallExpression";
+      // @ts-expect-error todo(flow->ts)
       optionalPath = skipTransparentExprWrappers(optionalPath.get("callee"));
     }
   }
 
-  let replacementPath = path;
+  let replacementPath: NodePath<any> = path;
   if (parentPath.isUnaryExpression({ operator: "delete" })) {
     replacementPath = parentPath;
     isDeleteOperation = true;
@@ -145,7 +150,7 @@ export function transform(
         // Otherwise, we need to memoize the context object, and change the call into a Function#call.
         // `a.?b.?()` translates roughly to `(_b = _a.b) != null && _b.call(_a)`
         const { object } = chain;
-        let context = scope.maybeGenerateMemoised(object);
+        let context: t.Expression = scope.maybeGenerateMemoised(object);
         if (context) {
           chain.object = t.assignmentExpression("=", context, object);
         } else if (t.isSuper(object)) {
@@ -194,6 +199,7 @@ export function transform(
         t.logicalExpression("&&", nonNullishCheck, replacement),
       );
       replacementPath = skipTransparentExprWrappers(
+        // @ts-expect-error todo(flow->ts)
         replacementPath.get("right"),
       );
     } else {
@@ -207,6 +213,7 @@ export function transform(
         t.conditionalExpression(nullishCheck, returnValue, replacement),
       );
       replacementPath = skipTransparentExprWrappers(
+        // @ts-expect-error todo(flow->ts)
         replacementPath.get("alternate"),
       );
     }

packages/babel-plugin-proposal-optional-chaining/src/util.ts

@@ -1,3 +1,4 @@
+import type { NodePath } from "@babel/traverse";
 import { isTransparentExprWrapper } from "@babel/helper-skip-transparent-expression-wrappers";
 /**
  * Test if a NodePath will be cast to boolean when evaluated.
@@ -58,7 +59,7 @@ export function willPathCastToBoolean(path: NodePath): boolean {
 export function findOutermostTransparentParent(path: NodePath): NodePath {
   let maybeWrapped = path;
   path.findParent(p => {
-    if (!isTransparentExprWrapper(p)) return true;
+    if (!isTransparentExprWrapper(p.node)) return true;
     maybeWrapped = p;
   });
   return maybeWrapped;

packages/babel-plugin-proposal-record-and-tuple/src/index.ts

@@ -20,6 +20,7 @@ import { types as t } from "@babel/core";
 import { addNamed, isModule } from "@babel/helper-module-imports";
 import { OptionValidator } from "@babel/helper-validator-option";
 
+declare const PACKAGE_JSON: { name: string; version: string };
 const v = new OptionValidator(PACKAGE_JSON.name);
 
 export default declare((api, options) => {

packages/babel-plugin-transform-arrow-functions/package.json

@@ -25,7 +25,8 @@
   "devDependencies": {
     "@babel/core": "workspace:^",
     "@babel/helper-plugin-test-runner": "workspace:^",
-    "@babel/traverse": "workspace:^"
+    "@babel/traverse": "workspace:^",
+    "@babel/types": "workspace:^"
   },
   "engines": {
     "node": ">=6.9.0"

packages/babel-plugin-transform-arrow-functions/src/index.ts

@@ -1,5 +1,6 @@
 import { declare } from "@babel/helper-plugin-utils";
-import type NodePath from "@babel/traverse";
+import type { NodePath } from "@babel/traverse";
+import type * as t from "@babel/types";
 
 export default declare((api, options) => {
   api.assertVersion(7);
@@ -10,9 +11,7 @@ export default declare((api, options) => {
     name: "transform-arrow-functions",
 
     visitor: {
-      ArrowFunctionExpression(
+      ArrowFunctionExpression(path: NodePath<t.ArrowFunctionExpression>) {
-        path: NodePath<BabelNodeArrowFunctionExpression>,
-      ) {
         // In some conversion cases, it may have already been converted to a function while this callback
         // was queued up.
         if (!path.isArrowFunctionExpression()) return;

packages/babel-plugin-transform-block-scoped-functions/src/index.ts

@@ -5,7 +5,7 @@ export default declare(api => {
   api.assertVersion(7);
 
   function statementList(key, path) {
-    const paths: Array = path.get(key);
+    const paths = path.get(key);
 
     for (const path of paths) {
       const func = path.node;
@@ -16,6 +16,7 @@ export default declare(api => {
       ]);
 
       // hoist it up above everything else
+      // @ts-expect-error todo(flow->ts): avoid mutations
       declar._blockHoist = 2;
 
       // todo: name this

packages/babel-plugin-transform-block-scoping/src/index.ts

@@ -920,7 +920,7 @@ class BlockScoping {
    * later on.
    */
 
-  checkLoop(): any {
+  checkLoop() {
     const state: LoopVisitorState = {
       hasBreakContinue: false,
       ignoreLabeless: false,

packages/babel-plugin-transform-computed-properties/src/index.ts

@@ -32,7 +32,7 @@ export default declare((api, options) => {
 
   function pushAssign(objId, prop, body) {
     if (prop.kind === "get" && prop.kind === "set") {
-      pushMutatorDefine(objId, prop, body);
+      pushMutatorDefine(objId, prop);
     } else {
       body.push(
         t.expressionStatement(
@@ -43,6 +43,7 @@ export default declare((api, options) => {
               prop.key,
               prop.computed || t.isLiteral(prop.key),
             ),
+            // @ts-expect-error todo(flow->ts): double-check type error
             getValue(prop),
           ),
         ),
@@ -65,12 +66,12 @@ export default declare((api, options) => {
     }
 
     body.push(
-      ...buildMutatorMapAssign({
+      ...(buildMutatorMapAssign({
         MUTATOR_MAP_REF: getMutatorId(),
         KEY: t.cloneNode(key),
         VALUE: getValue(prop),
         KIND: t.identifier(prop.kind),
-      }),
+      }) as t.Statement[]),
     );
   }
 
@@ -122,7 +123,7 @@ export default declare((api, options) => {
         exit(path, state) {
           const { node, parent, scope } = path;
           let hasComputed = false;
-          for (const prop of (node.properties: Array<Object>)) {
+          for (const prop of node.properties) {
             hasComputed = prop.computed === true;
             if (hasComputed) break;
           }
@@ -194,6 +195,7 @@ export default declare((api, options) => {
             );
           }
 
+          // @ts-expect-error todo(flow->ts) `void` should not be used as variable
           if (single) {
             path.replaceWith(single);
           } else {

packages/babel-plugin-transform-destructuring/package.json

@@ -24,7 +24,8 @@
   },
   "devDependencies": {
     "@babel/core": "workspace:^",
-    "@babel/helper-plugin-test-runner": "workspace:^"
+    "@babel/helper-plugin-test-runner": "workspace:^",
+    "@babel/traverse": "workspace:^"
   },
   "engines": {
     "node": ">=6.9.0"

packages/babel-plugin-transform-destructuring/src/index.ts

@@ -1,5 +1,6 @@
 import { declare } from "@babel/helper-plugin-utils";
 import { types as t } from "@babel/core";
+import type { Scope } from "@babel/traverse";
 
 export default declare((api, options) => {
   api.assertVersion(7);
@@ -23,7 +24,7 @@ export default declare((api, options) => {
    */
 
   function variableDeclarationHasPattern(node) {
-    for (const declar of (node.declarations: Array)) {
+    for (const declar of node.declarations) {
       if (t.isPattern(declar.id)) {
         return true;
       }
@@ -36,7 +37,7 @@ export default declare((api, options) => {
    */
 
   function hasRest(pattern) {
-    for (const elem of (pattern.elements: Array)) {
+    for (const elem of pattern.elements) {
       if (t.isRestElement(elem)) {
         return true;
       }
@@ -49,7 +50,7 @@ export default declare((api, options) => {
    */
 
   function hasObjectRest(pattern) {
-    for (const elem of (pattern.properties: Array)) {
+    for (const elem of pattern.properties) {
       if (t.isRestElement(elem)) {
         return true;
       }
@@ -77,6 +78,15 @@ export default declare((api, options) => {
   };
 
   class DestructuringTransformer {
+    private blockHoist: any;
+    private operator: any;
+    arrays: any;
+    private nodes: any;
+    private scope: Scope;
+    private kind: any;
+    private iterableIsArray: any;
+    private arrayLikeIsIterable: any;
+    private addHelper: any;
     constructor(opts) {
       this.blockHoist = opts.blockHoist;
       this.operator = opts.operator;
@@ -118,6 +128,7 @@ export default declare((api, options) => {
       const declar = t.variableDeclaration("var", [
         t.variableDeclarator(t.cloneNode(id), t.cloneNode(init)),
       ]);
+      // @ts-expect-error todo(flow->ts): avoid mutations
       declar._blockHoist = this.blockHoist;
       return declar;
     }
@@ -135,7 +146,7 @@ export default declare((api, options) => {
       }
     }
 
-    toArray(node, count) {
+    toArray(node, count?) {
       if (
         this.iterableIsArray ||
         (t.isIdentifier(node) && this.arrays[node.name])
@@ -208,6 +219,7 @@ export default declare((api, options) => {
           keys.push(t.cloneNode(key));
           hasTemplateLiteral = true;
         } else if (t.isLiteral(key)) {
+          // @ts-expect-error todo(flow->ts) NullLiteral
           keys.push(t.stringLiteral(String(key.value)));
         } else {
           keys.push(t.cloneNode(key));
@@ -222,7 +234,7 @@ export default declare((api, options) => {
           t.cloneNode(objRef),
         ]);
       } else {
-        let keyExpression = t.arrayExpression(keys);
+        let keyExpression: t.Expression = t.arrayExpression(keys);
 
         if (!allLiteral) {
           keyExpression = t.callExpression(
@@ -342,7 +354,7 @@ export default declare((api, options) => {
         return false;
       }
 
-      for (const elem of (pattern.elements: Array)) {
+      for (const elem of pattern.elements) {
         // deopt on holes
         if (!elem) return false;
 
@@ -350,7 +362,7 @@ export default declare((api, options) => {
         if (t.isMemberExpression(elem)) return false;
       }
 
-      for (const elem of (arr.elements: Array)) {
+      for (const elem of arr.elements) {
         // deopt on spread elements
         if (t.isSpreadElement(elem)) return false;