Fix PathHoister hoisting before a same-scope variable declaration.

Seems we didn't have tests running for this very simple case.

Also fixes #5520

packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/async-function/actual.js

@@ -0,0 +1,9 @@
+export default {
+    async function(name) {
+        const uppercasedName = name.upperCase();
+
+        // awaits depending on uppercasedName go here
+
+        return (<Foo name={uppercasedName} />);
+    }
+};

packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/async-function/expected.js

@@ -0,0 +1,13 @@
+function _asyncToGenerator(fn) { return function () { var gen = fn.apply(this, arguments); return new Promise(function (resolve, reject) { function step(key, arg) { try { var info = gen[key](arg); var value = info.value; } catch (error) { reject(error); return; } if (info.done) { resolve(value); } else { Promise.resolve(value).then(_next, _throw); } } function _next(value) { step("next", value); } function _throw(err) { step("throw", err); } _next(); }); }; }
+
+export default {
+    function(name) {
+        return _asyncToGenerator(function* () {
+            const uppercasedName = name.upperCase();
+
+            // awaits depending on uppercasedName go here
+
+            return <Foo name={uppercasedName} />;
+        })();
+    }
+};

packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/async-function/options.json

@@ -0,0 +1,3 @@
+{
+  "plugins": ["transform-async-to-generator", "transform-react-constant-elements", "syntax-jsx"]
+}

packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/param-and-var/actual.js

@@ -0,0 +1,6 @@
+function fn(Component, obj) {
+
+  var data = obj.data;
+
+  return () => <Component prop={data} />;
+}

packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/param-and-var/expected.js

@@ -0,0 +1,7 @@
+function fn(Component, obj) {
+
+  var data = obj.data,
+      _ref = <Component prop={data} />;
+
+  return () => _ref;
+}

packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/var/actual.js

@@ -0,0 +1,6 @@
+function fn(Component) {
+
+  var data = "prop";
+
+  return () => <Component prop={data} />;
+}

packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/var/expected.js

@@ -0,0 +1,7 @@
+function fn(Component) {
+
+  var data = "prop",
+      _ref = <Component prop={data} />;
+
+  return () => _ref;
+}

packages/babel-traverse/src/path/lib/hoister.js

@@ -99,11 +99,15 @@ export default class PathHoister {
 
         const binding = this.bindings[name];
 
-        // allow parameter references
-        if (binding.kind === "param") continue;
+        // allow parameter references and expressions in params (like destructuring rest)
+        if (binding.kind === "param" || binding.path.parentKey === "params") continue;
 
-        // if this binding appears after our attachment point, then we move after it.
-        if (this.getAttachmentParentForPath(binding.path).key > path.key) {
+        // For each binding, get its attachment parent. This gives us an idea of where we might
+        // introduce conflicts.
+        const bindingParentPath = this.getAttachmentParentForPath(binding.path);
+
+        // If the binding's attachment appears at or after our attachment point, then we move after it.
+        if (bindingParentPath.key >= path.key) {
           this.attachAfter = true;
           path = binding.path;