Fix #4840: Alias class prototype for methods in loose mode (#5560)

* Fix #4840: Alias class prototype for methods in loose mode

* Cleanup

packages/babel-plugin-transform-es2015-classes/test/fixtures/loose-classCallCheck/with-constructor/expected.js

@@ -5,7 +5,9 @@ let A = function A() {
 let B = function () {
   function B() {}
 
-  B.prototype.b = function b() {
+  var _proto = B.prototype;
+
+  _proto.b = function b() {
     console.log('b');
   };
 

packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/constructor-order/expected.js

@@ -1,5 +1,7 @@
 var x = function () {
-  x.prototype.f = function f() {
+  var _proto = x.prototype;
+
+  _proto.f = function f() {
     1;
     2;
     3;

packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/literal-key/expected.js

@@ -1,7 +1,9 @@
 var Foo = function () {
   function Foo() {}
 
-  Foo.prototype["bar"] = function bar() {};
+  var _proto = Foo.prototype;
+
+  _proto["bar"] = function bar() {};
 
   return Foo;
-}();
+}();

packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/method-return-type-annotation/expected.js

@@ -2,9 +2,11 @@
 var C = function () {
   function C() {}
 
-  C.prototype.m = function m(x: number): string {
+  var _proto = C.prototype;
+
+  _proto.m = function m(x: number): string {
     return 'a';
   };
 
   return C;
-}();
+}();

packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/method-reuse-prototype/actual.js

@@ -0,0 +1,5 @@
+class Test {
+  a() {}
+  static b() {}
+  c() {}
+}

packages/babel-plugin-transform-es2015-classes/test/fixtures/loose/method-reuse-prototype/expected.js

@@ -0,0 +1,13 @@
+var Test = function () {
+  function Test() {}
+
+  var _proto = Test.prototype;
+
+  _proto.a = function a() {};
+
+  Test.b = function b() {};
+
+  _proto.c = function c() {};
+
+  return Test;
+}();

packages/babel-plugin-transform-es2015-classes/test/fixtures/regression/T6755/expected.js

@@ -3,11 +3,13 @@
 var Example = function () {
   function Example() {}
 
-  Example.prototype.test1 = async function test1() {
+  var _proto = Example.prototype;
+
+  _proto.test1 = async function test1() {
     await Promise.resolve(2);
   };
 
-  Example.prototype.test2 =
+  _proto.test2 =
   /*#__PURE__*/
   regeneratorRuntime.mark(function test2() {
     return regeneratorRuntime.wrap(function test2$(_context) {