fix: avoid name conflicts with current class elements

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

@@ -1,6 +1,40 @@
 import { declare } from "@babel/helper-plugin-utils";
 import syntaxClassStaticBlock from "@babel/plugin-syntax-class-static-block";
 
+/**
+ * Generate a uid that is not in `denyList`
+ *
+ * @param {*} scope
+ * @param {Set<string>} privateNames
+ * @returns
+ */
+function generateUid(scope, denyList: Set<string>) {
+  const name = "";
+  let uid;
+  let i = 0;
+  do {
+    uid = scope._generateUid(name, i);
+    i++;
+  } while (denyList.has(uid));
+  return uid;
+}
+
+/**
+ * Get private names defined in current class body
+ *
+ * @param {NodePath<ClassBody>} classBody
+ * @returns {Set<string>} A set of defined private names
+ */
+function getPrivateNames(classBody: NodePath<ClassBody>): Set<string> {
+  const privateNames = new Set();
+  for (const path of classBody.get("body")) {
+    if (path.isPrivate()) {
+      privateNames.add(path.get("key.id").node.name);
+    }
+  }
+  return privateNames;
+}
+
 export default declare(({ types: t, template, assertVersion }) => {
   // todo remove this check after Babel 7.12.0 is published
   if (process.env.NODE_ENV !== "test") {
@@ -11,13 +45,15 @@ export default declare(({ types: t, template, assertVersion }) => {
     name: "proposal-class-static-block",
     inherits: syntaxClassStaticBlock,
     visitor: {
-      StaticBlock(path) {
-        const staticBlockRef = path.scope.generateUidIdentifier("");
-        const classBody = path.parentPath;
+      StaticBlock(path: NodePath<StaticBlock>) {
+        const { parentPath: classBody, scope } = path;
+        const staticBlockRef = t.privateName(
+          t.identifier(generateUid(scope, getPrivateNames(classBody))),
+        );
         classBody.pushContainer(
           "body",
           t.classPrivateProperty(
-            t.privateName(staticBlockRef),
+            staticBlockRef,
             template.expression.ast`(() => { ${path.node.body} })()`,
             [],
             /* static */ true,

packages/babel-plugin-proposal-class-static-block/test/fixtures/class-static-block/in-class-heritage/output.js

@@ -1,9 +1,9 @@
 class Foo extends class extends class Base {
-  static #_3 = (() => {
+  static #_ = (() => {
     this.qux = 21;
   })();
 } {
-  static #_2 = (() => {
+  static #_ = (() => {
     this.bar = 21;
   })();
 } {

packages/babel-plugin-proposal-class-static-block/test/fixtures/class-static-block/name-conflict/exec.js

@@ -0,0 +1,8 @@
+class Foo {
+  static #_ = 42;
+  // static block can not be tranformed as `#_` here
+  static {
+    this.foo = this.#_;
+  }
+}
+expect(Foo.foo).toBe(42);

packages/babel-plugin-proposal-class-static-block/test/fixtures/class-static-block/name-conflict/input.js

@@ -0,0 +1,8 @@
+class Foo {
+  static #_ = 42;
+  // static block can not be tranformed as `#_` here
+  static {
+    this.foo = this.#_;
+  }
+}
+expect(Foo.foo).toBe(42);

packages/babel-plugin-proposal-class-static-block/test/fixtures/class-static-block/name-conflict/output.js

@@ -0,0 +1,9 @@
+class Foo {
+  static #_ = 42; // static block can not be tranformed as `#_` here
+
+  static #_2 = (() => {
+    this.foo = this.#_;
+  })();
+}
+
+expect(Foo.foo).toBe(42);