Add support for extending builtins (#7020)

packages/babel-plugin-transform-classes/src/index.js

@@ -3,6 +3,15 @@ import VanillaTransformer from "./vanilla";
 import annotateAsPure from "@babel/helper-annotate-as-pure";
 import nameFunction from "@babel/helper-function-name";
 import { types as t } from "@babel/core";
+import globals from "globals";
+
+const getBuiltinClasses = category =>
+  Object.keys(globals[category]).filter(name => /^[A-Z]/.test(name));
+
+const builtinClasses = new Set([
+  ...getBuiltinClasses("builtin"),
+  ...getBuiltinClasses("browser"),
+]);
 
 export default function(api, options) {
   const { loose } = options;
@@ -54,7 +63,9 @@ export default function(api, options) {
 
         node[VISITED] = true;
 
-        path.replaceWith(new Constructor(path, state.file).run());
+        path.replaceWith(
+          new Constructor(path, state.file, builtinClasses).run(),
+        );
 
         if (path.isCallExpression()) {
           annotateAsPure(path);

packages/babel-plugin-transform-classes/src/vanilla.js

@@ -4,6 +4,8 @@ import optimiseCall from "@babel/helper-optimise-call-expression";
 import * as defineMap from "@babel/helper-define-map";
 import { traverse, template, types as t } from "@babel/core";
 
+type ReadonlySet<T> = Set<T> | { has(val: T): boolean };
+
 const noMethodVisitor = {
   "FunctionExpression|FunctionDeclaration"(path) {
     path.skip();
@@ -61,7 +63,7 @@ const findThisesVisitor = traverse.visitors.merge([
 ]);
 
 export default class ClassTransformer {
-  constructor(path: NodePath, file) {
+  constructor(path: NodePath, file, builtinClasses: ReadonlySet<string>) {
     this.parent = path.parent;
     this.scope = path.scope;
     this.node = path.node;
@@ -93,6 +95,12 @@ export default class ClassTransformer {
 
     this.superName = this.node.superClass || t.identifier("Function");
     this.isDerived = !!this.node.superClass;
+
+    const { name } = this.superName;
+    this.extendsNative =
+      this.isDerived &&
+      builtinClasses.has(name) &&
+      !this.scope.hasBinding(name, /* noGlobals */ true);
   }
 
   run() {
@@ -112,7 +120,13 @@ export default class ClassTransformer {
 
     //
     if (this.isDerived) {
-      closureArgs.push(superName);
+      if (this.extendsNative) {
+        closureArgs.push(
+          t.callExpression(this.file.addHelper("wrapNativeSuper"), [superName]),
+        );
+      } else {
+        closureArgs.push(superName);
+      }
 
       superName = this.scope.generateUidIdentifierBasedOnNode(superName);
       closureParams.push(superName);