Improve preset/plugin-typescript typings

packages/babel-plugin-transform-typescript/src/enum.ts

@@ -39,7 +39,7 @@ export default function transpileEnum(
       throw new Error(`Unexpected enum parent '${path.parent.type}`);
   }
 
-  function seen(parentPath: NodePath<t.Node>) {
+  function seen(parentPath: NodePath<t.Node>): boolean {
     if (parentPath.isExportDeclaration()) {
       return seen(parentPath.parentPath);
     }
@@ -193,12 +193,12 @@ export function translateEnumValues(
 
 // Based on the TypeScript repository's `evalConstant` in `checker.ts`.
 function evaluate(
-  expr,
+  expr: t.Node,
   seen: PreviousEnumMembers,
 ): number | string | typeof undefined {
   return evalConstant(expr);
 
-  function evalConstant(expr): number | typeof undefined {
+  function evalConstant(expr: t.Node): number | typeof undefined {
     switch (expr.type) {
       case "StringLiteral":
         return expr.value;
@@ -225,7 +225,7 @@ function evaluate(
   function evalUnaryExpression({
     argument,
     operator,
-  }): number | typeof undefined {
+  }: t.UnaryExpression): number | typeof undefined {
     const value = evalConstant(argument);
     if (value === undefined) {
       return undefined;
@@ -243,7 +243,7 @@ function evaluate(
     }
   }
 
-  function evalBinaryExpression(expr): number | typeof undefined {
+  function evalBinaryExpression(expr: t.BinaryExpression): number | undefined {
     const left = evalConstant(expr.left);
     if (left === undefined) {
       return undefined;

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

@@ -2,7 +2,7 @@ import { declare } from "@babel/helper-plugin-utils";
 import syntaxTypeScript from "@babel/plugin-syntax-typescript";
 import { types as t, template } from "@babel/core";
 import { injectInitialization } from "@babel/helper-create-class-features-plugin";
-import type { NodePath } from "@babel/traverse";
+import type { Binding, NodePath } from "@babel/traverse";
 import type { Options as SyntaxOptions } from "@babel/plugin-syntax-typescript";
 
 import transpileConstEnum from "./const-enum";
@@ -149,15 +149,15 @@ export default declare((api, opts: Options) => {
       if (node.declare) node.declare = null;
       if (node.override) node.override = null;
     },
-    method({ node }) {
+    method({ node }: NodePath<t.ClassMethod | t.ClassPrivateMethod>) {
       if (node.accessibility) node.accessibility = null;
       if (node.abstract) node.abstract = null;
       if (node.optional) node.optional = null;
       if (node.override) node.override = null;
 
       // Rest handled by Function visitor
     },
-    constructor(path, classPath) {
+    constructor(path: NodePath<t.ClassMethod>, classPath: NodePath<t.Class>) {
       if (path.node.accessibility) path.node.accessibility = null;
       // Collects parameter properties so that we can add an assignment
       // for each of them in the constructor body
@@ -487,7 +487,11 @@ export default declare((api, opts: Options) => {
         path.get("body.body").forEach(child => {
           if (child.isClassMethod() || child.isClassPrivateMethod()) {
             if (child.node.kind === "constructor") {
-              classMemberVisitors.constructor(child, path);
+              classMemberVisitors.constructor(
+                // @ts-expect-error A constructor must not be a private method
+                child,
+                path,
+              );
             } else {
               classMemberVisitors.method(child);
             }
@@ -512,7 +516,7 @@ export default declare((api, opts: Options) => {
       },
 
       TSModuleDeclaration(path) {
-        transpileNamespace(path, t, allowNamespaces);
+        transpileNamespace(path, allowNamespaces);
       },
 
       TSInterfaceDeclaration(path) {
@@ -614,7 +618,9 @@ export default declare((api, opts: Options) => {
     return node;
   }
 
-  function visitPattern({ node }) {
+  function visitPattern({
+    node,
+  }: NodePath<t.Identifier | t.Pattern | t.RestElement>) {
     if (node.typeAnnotation) node.typeAnnotation = null;
     if (t.isIdentifier(node) && node.optional) node.optional = null;
     // 'access' and 'readonly' are only for parameter properties, so constructor visitor will handle them.
@@ -625,6 +631,11 @@ export default declare((api, opts: Options) => {
     programPath,
     pragmaImportName,
     pragmaFragImportName,
+  }: {
+    binding: Binding;
+    programPath: NodePath<t.Program>;
+    pragmaImportName: string;
+    pragmaFragImportName: string;
   }) {
     for (const path of binding.referencePaths) {
       if (!isInType(path)) {

packages/babel-plugin-transform-typescript/src/namespace.ts

@@ -1,29 +1,33 @@
 import { template, types as t } from "@babel/core";
 import type { NodePath } from "@babel/traverse";
 
-export default function transpileNamespace(path, t, allowNamespaces) {
+export default function transpileNamespace(
+  path: NodePath<t.TSModuleDeclaration>,
+  allowNamespaces: boolean,
+) {
   if (path.node.declare || path.node.id.type === "StringLiteral") {
     path.remove();
     return;
   }
 
   if (!allowNamespaces) {
-    throw path.hub.file.buildCodeFrameError(
-      path.node.id,
-      "Namespace not marked type-only declare." +
-        " Non-declarative namespaces are only supported experimentally in Babel." +
-        " To enable and review caveats see:" +
-        " https://babeljs.io/docs/en/babel-plugin-transform-typescript",
-    );
+    throw path
+      .get("id")
+      .buildCodeFrameError(
+        "Namespace not marked type-only declare." +
+          " Non-declarative namespaces are only supported experimentally in Babel." +
+          " To enable and review caveats see:" +
+          " https://babeljs.io/docs/en/babel-plugin-transform-typescript",
+      );
   }
 
   const name = path.node.id.name;
-  const value = handleNested(path, t, t.cloneDeep(path.node));
+  const value = handleNested(path, t.cloneNode(path.node, true));
   const bound = path.scope.hasOwnBinding(name);
   if (path.parent.type === "ExportNamedDeclaration") {
     if (!bound) {
       path.parentPath.insertAfter(value);
-      path.replaceWith(getDeclaration(t, name));
+      path.replaceWith(getDeclaration(name));
       path.scope.registerDeclaration(path.parentPath);
     } else {
       path.parentPath.replaceWith(value);
@@ -32,18 +36,18 @@ export default function transpileNamespace(path, t, allowNamespaces) {
     path.replaceWith(value);
   } else {
     path.scope.registerDeclaration(
-      path.replaceWithMultiple([getDeclaration(t, name), value])[0],
+      path.replaceWithMultiple([getDeclaration(name), value])[0],
     );
   }
 }
 
-function getDeclaration(t, name) {
+function getDeclaration(name: string) {
   return t.variableDeclaration("let", [
     t.variableDeclarator(t.identifier(name)),
   ]);
 }
 
-function getMemberExpression(t, name, itemName) {
+function getMemberExpression(name: string, itemName: string) {
   return t.memberExpression(t.identifier(name), t.identifier(itemName));
 }
 
@@ -79,7 +83,7 @@ function handleVariableDeclaration(
     for (const declarator of declarations) {
       declarator.init = t.assignmentExpression(
         "=",
-        getMemberExpression(t, name, declarator.id.name),
+        getMemberExpression(name, declarator.id.name),
         declarator.init,
       );
     }
@@ -95,7 +99,7 @@ function handleVariableDeclaration(
     assignments.push(
       t.assignmentExpression(
         "=",
-        getMemberExpression(t, name, idName),
+        getMemberExpression(name, idName),
         t.cloneNode(bindingIdentifiers[idName]),
       ),
     );
@@ -113,9 +117,8 @@ function buildNestedAmbiendModuleError(path: NodePath, node: t.Node) {
 
 function handleNested(
   path: NodePath,
-  t: typeof import("@babel/types"),
   node: t.TSModuleDeclaration,
-  parentExport?,
+  parentExport?: t.Expression,
 ) {
   const names = new Set();
   const realName = node.id;
@@ -142,7 +145,7 @@ function handleNested(
           throw buildNestedAmbiendModuleError(path, subNode);
         }
 
-        const transformed = handleNested(path, t, subNode);
+        const transformed = handleNested(path, subNode);
         const moduleName = subNode.id.name;
         if (names.has(moduleName)) {
           namespaceTopLevel[i] = transformed;
@@ -151,7 +154,7 @@ function handleNested(
           namespaceTopLevel.splice(
             i++,
             1,
-            getDeclaration(t, moduleName),
+            getDeclaration(moduleName),
             transformed,
           );
         }
@@ -191,7 +194,7 @@ function handleNested(
           t.expressionStatement(
             t.assignmentExpression(
               "=",
-              getMemberExpression(t, name, itemName),
+              getMemberExpression(name, itemName),
               t.identifier(itemName),
             ),
           ),
@@ -215,7 +218,6 @@ function handleNested(
 
         const transformed = handleNested(
           path,
-          t,
           subNode.declaration,
           t.identifier(name),
         );
@@ -227,7 +229,7 @@ function handleNested(
           namespaceTopLevel.splice(
             i++,
             1,
-            getDeclaration(t, moduleName),
+            getDeclaration(moduleName),
             transformed,
           );
         }

packages/babel-preset-typescript/src/index.ts

@@ -18,7 +18,7 @@ export default declarePreset((api, opts: Options) => {
   } = normalizeOptions(opts);
 
   const pluginOptions = process.env.BABEL_8_BREAKING
-    ? (isTSX, disallowAmbiguousJSXLike) => ({
+    ? (isTSX: boolean, disallowAmbiguousJSXLike: boolean) => ({
         allowNamespaces,
         disallowAmbiguousJSXLike,
         isTSX,
@@ -27,7 +27,7 @@ export default declarePreset((api, opts: Options) => {
         onlyRemoveTypeImports,
         optimizeConstEnums,
       })
-    : (isTSX, disallowAmbiguousJSXLike) => ({
+    : (isTSX: boolean, disallowAmbiguousJSXLike: boolean) => ({
         allowDeclareFields: opts.allowDeclareFields,
         allowNamespaces,
         disallowAmbiguousJSXLike,