Fix ReferenceError in the wrapNativeSuper helper (#8100)

Fix a ReferenceError caused by a typo (`_construct` instead of
`construct`) in the external `wrapNativeSuper` helper. (The typo
doesn't usually cause an error in inline helpers because `_construct`
happens to be the default name given to the `construct` helper
function.)

packages/babel-plugin-transform-classes/test/fixtures/extend-builtins/overwritten-null/exec.js

@@ -2,7 +2,7 @@ var env = {
   Array: null,
 };
 
-// Wee need to use "with" to avoid leaking the modified Array to other tests.
+// We need to use "with" to avoid leaking the modified Array to other tests.
 with (env) {
   class List extends Array {}
   expect(List.prototype.__proto__).toBeUndefined();

packages/babel-plugin-transform-classes/test/fixtures/extend-builtins/super-called/exec.js

@@ -6,7 +6,7 @@ var env = {
   }
 };
 
-// Wee need to use "with" to avoid leaking the modified Array to other tests.
+// We need to use "with" to avoid leaking the modified Array to other tests.
 with (env) {
   class List extends Array {};
   new List();

packages/babel-plugin-transform-classes/test/fixtures/extend-builtins/wrap-native-super/exec.js

@@ -0,0 +1,25 @@
+// basic sanity check to confirm the external wrapNativeSuper helper works
+
+class Test1 extends Array {
+  name() {
+    return 'test1';
+  }
+}
+
+class Test2 extends Array {
+  name() {
+    return 'test2';
+  }
+}
+
+var t1 = new Test1();
+var t2 = new Test2();
+
+expect(Test1).not.toBe(Test2);
+expect(t1).not.toBe(t2);
+expect(t1.name()).toBe('test1');
+expect(t2.name()).toBe('test2');
+expect(t1).toBeInstanceOf(Test1);
+expect(t2).toBeInstanceOf(Test2);
+expect(t1).toBeInstanceOf(Array);
+expect(t2).toBeInstanceOf(Array);

packages/babel-plugin-transform-classes/test/fixtures/extend-builtins/wrap-native-super/options.json

@@ -0,0 +1,3 @@
+{
+  "plugins": ["transform-classes","transform-block-scoping","external-helpers"]
+}