Fix polyfilling of X.prototype (#207)

packages/babel-helper-define-polyfill-provider/src/visitors/usage.ts

@@ -30,19 +30,27 @@ export default (callProvider: CallProvider) => {
     callProvider({ kind: "global", name }, path);
   }
 
+  function analyzeMemberExpression(path: NodePath<t.MemberExpression>) {
+    const key = resolveKey(path.get("property"), path.node.computed);
+    return { key, handleAsMemberExpression: !!key && key !== "prototype" };
+  }
+
   return {
     // Symbol(), new Promise
     ReferencedIdentifier(path: NodePath<t.Identifier>) {
-      if (path.parentPath.isMemberExpression({ object: path.node })) {
-        // Handled in the MemberExpression visitor
+      const { parentPath } = path;
+      if (
+        parentPath.isMemberExpression({ object: path.node }) &&
+        analyzeMemberExpression(parentPath).handleAsMemberExpression
+      ) {
         return;
       }
       handleReferencedIdentifier(path);
     },
 
     MemberExpression(path: NodePath<t.MemberExpression>) {
-      const key = resolveKey(path.get("property"), path.node.computed);
-      if (!key || key === "prototype") return;
+      const { key, handleAsMemberExpression } = analyzeMemberExpression(path);
+      if (!handleAsMemberExpression) return;
 
       const object = path.get("object");
       let objectIsGlobalIdentifier = object.isIdentifier();

packages/babel-plugin-polyfill-corejs2/test/fixtures/usage-pure/symbol-prototype/input.js

@@ -0,0 +1 @@
+Symbol.prototype;

packages/babel-plugin-polyfill-corejs2/test/fixtures/usage-pure/symbol-prototype/options.json

@@ -0,0 +1,10 @@
+{
+  "plugins": [
+    [
+      "@@/polyfill-corejs2",
+      {
+        "method": "usage-pure"
+      }
+    ]
+  ]
+}

packages/babel-plugin-polyfill-corejs2/test/fixtures/usage-pure/symbol-prototype/output.js

@@ -0,0 +1,2 @@
+var _Symbol = require("core-js/library/fn/symbol/index.js");
+_Symbol.prototype;

packages/babel-plugin-polyfill-corejs3/test/fixtures/usage-pure/symbol-prototype/input.js

@@ -0,0 +1 @@
+Symbol.prototype;

packages/babel-plugin-polyfill-corejs3/test/fixtures/usage-pure/symbol-prototype/options.json

@@ -0,0 +1,10 @@
+{
+  "plugins": [
+    [
+      "@@/polyfill-corejs3",
+      {
+        "method": "usage-pure"
+      }
+    ]
+  ]
+}

packages/babel-plugin-polyfill-corejs3/test/fixtures/usage-pure/symbol-prototype/output.js

@@ -0,0 +1,2 @@
+var _Symbol = require("core-js-pure/stable/symbol/index.js");
+_Symbol.prototype;