Update @babel/helper-wrap-function templates (#6984)

This commit introduces 4 changes:

1) Function declarations are wrapped using function declarations.
   This has two advantages:
    - We can rely on native hoisting, instead of using _blockHoist
    - The function isn't wrapped until it is called. This avoids
      problems where `regeneratorRuntime.wrap` was called before
      that `babel-polyfill` was imported.

   Example:
     function fn() {}
     // becomes
     function fn() { return _fn.apply(this, arguments); }
     function _fn() {
       _fn = _wrapper(/* Original function ... */);
       return _fn.apply(this, arguments);
     }

2) Use a single template for both named and anonymous function
   expressions. They already had the same behavior, but the one
   used for named functions was a bit longer.

3) Use normal functions instead of arrow functions to wrap
   function expressions.

4) Generate a name based on the original one for wrapped
   functions (e.g. `foo` becomes `_foo` instead of `_ref`).

packages/babel-plugin-proposal-function-sent/test/fixtures/function-sent/basic/expected.js

@@ -1,13 +1,14 @@
-let gen = (() => {
-  var _ref = _skipFirstGeneratorNext(function* () {
+function _skipFirstGeneratorNext(fn) { return function () { var it = fn.apply(this, arguments); it.next(); return it; }; }
+
+function gen() {
+  return _gen.apply(this, arguments);
+}
+
+function _gen() {
+  _gen = _skipFirstGeneratorNext(function* () {
     let _functionSent = yield;
 
     let sent = _functionSent;
   });
-
-  return function gen() {
-    return _ref.apply(this, arguments);
-  };
-})();
-
-function _skipFirstGeneratorNext(fn) { return function () { var it = fn.apply(this, arguments); it.next(); return it; }; }
+  return _gen.apply(this, arguments);
+}

packages/babel-plugin-proposal-function-sent/test/fixtures/generator-kinds/async-generator/expected.js

@@ -1,17 +1,3 @@
-let foo =
-/*#__PURE__*/
-(() => {
-  var _ref = _wrapAsyncGenerator(_skipFirstGeneratorNext(function* () {
-    let _functionSent = yield;
-
-    _functionSent = yield _awaitAsyncGenerator(_functionSent);
-  }));
-
-  return function foo() {
-    return _ref.apply(this, arguments);
-  };
-})();
-
 function _skipFirstGeneratorNext(fn) { return function () { var it = fn.apply(this, arguments); it.next(); return it; }; }
 
 function _awaitAsyncGenerator(value) { return new _AwaitValue(value); }
@@ -29,3 +15,16 @@ _AsyncGenerator.prototype.throw = function (arg) { return this._invoke("throw",
 _AsyncGenerator.prototype.return = function (arg) { return this._invoke("return", arg); };
 
 function _AwaitValue(value) { this.wrapped = value; }
+
+function foo() {
+  return _foo.apply(this, arguments);
+}
+
+function _foo() {
+  _foo = _wrapAsyncGenerator(_skipFirstGeneratorNext(function* () {
+    let _functionSent = yield;
+
+    _functionSent = yield _awaitAsyncGenerator(_functionSent);
+  }));
+  return _foo.apply(this, arguments);
+}

packages/babel-plugin-proposal-function-sent/test/fixtures/generator-kinds/export-default-anonymous/expected.js

@@ -1,7 +1,14 @@
 function _skipFirstGeneratorNext(fn) { return function () { var it = fn.apply(this, arguments); it.next(); return it; }; }
 
-export default _skipFirstGeneratorNext(function* () {
-  let _functionSent = yield;
+export default function () {
+  return _ref.apply(this, arguments);
+}
 
-  return _functionSent;
-});
+function _ref() {
+  _ref = _skipFirstGeneratorNext(function* () {
+    let _functionSent = yield;
+
+    return _functionSent;
+  });
+  return _ref.apply(this, arguments);
+}

packages/babel-plugin-proposal-function-sent/test/fixtures/generator-kinds/export-default-named/expected.js

@@ -1,15 +1,14 @@
-let gen = (() => {
-  var _ref = _skipFirstGeneratorNext(function* () {
+function _skipFirstGeneratorNext(fn) { return function () { var it = fn.apply(this, arguments); it.next(); return it; }; }
+
+export default function gen() {
+  return _gen.apply(this, arguments);
+}
+
+function _gen() {
+  _gen = _skipFirstGeneratorNext(function* () {
     let _functionSent = yield;
 
     return _functionSent;
   });
-
-  return function gen() {
-    return _ref.apply(this, arguments);
-  };
-})();
-
-function _skipFirstGeneratorNext(fn) { return function () { var it = fn.apply(this, arguments); it.next(); return it; }; }
-
-export { gen as default };
+  return _gen.apply(this, arguments);
+}

packages/babel-plugin-proposal-function-sent/test/fixtures/generator-kinds/export/expected.js

@@ -1,13 +1,14 @@
 function _skipFirstGeneratorNext(fn) { return function () { var it = fn.apply(this, arguments); it.next(); return it; }; }
 
-export let gen = (() => {
-  var _ref = _skipFirstGeneratorNext(function* () {
+export function gen() {
+  return _gen.apply(this, arguments);
+}
+
+function _gen() {
+  _gen = _skipFirstGeneratorNext(function* () {
     let _functionSent = yield;
 
     return _functionSent;
   });
-
-  return function gen() {
-    return _ref.apply(this, arguments);
-  };
-})();
+  return _gen.apply(this, arguments);
+}

packages/babel-plugin-proposal-function-sent/test/fixtures/generator-kinds/expression-named/expected.js

@@ -1,15 +1,13 @@
 function _skipFirstGeneratorNext(fn) { return function () { var it = fn.apply(this, arguments); it.next(); return it; }; }
 
-const foo = (() => {
-  var _ref = _skipFirstGeneratorNext(function* () {
+const foo = function () {
+  var _gen = _skipFirstGeneratorNext(function* () {
     let _functionSent = yield;
 
     return _functionSent;
   });
 
-  function gen() {
-    return _ref.apply(this, arguments);
-  }
-
-  return gen;
-})();
+  return function gen() {
+    return _gen.apply(this, arguments);
+  };
+}();

packages/babel-plugin-proposal-function-sent/test/fixtures/generator-kinds/statement/expected.js

@@ -1,13 +1,14 @@
-let gen = (() => {
-  var _ref = _skipFirstGeneratorNext(function* () {
+function _skipFirstGeneratorNext(fn) { return function () { var it = fn.apply(this, arguments); it.next(); return it; }; }
+
+function gen() {
+  return _gen.apply(this, arguments);
+}
+
+function _gen() {
+  _gen = _skipFirstGeneratorNext(function* () {
     let _functionSent = yield;
 
     return _functionSent;
   });
-
-  return function gen() {
-    return _ref.apply(this, arguments);
-  };
-})();
-
-function _skipFirstGeneratorNext(fn) { return function () { var it = fn.apply(this, arguments); it.next(); return it; }; }
+  return _gen.apply(this, arguments);
+}