Fix PathHoister attaching to default parameters. (#5415)

* Fix PathHoister attaching to default parameters.

Ref: #5315

* Update hoister.js

packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/dont-hoist-before-default-params-2/actual.js

@@ -0,0 +1,5 @@
+function render(title= '') {
+  return () => (
+    <Component title={title} />
+  );
+}

packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/dont-hoist-before-default-params-2/expected.js

@@ -0,0 +1,7 @@
+function render() {
+  var title = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : '';
+
+  var _ref = <Component title={title} />;
+
+  return () => _ref;
+}

packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/dont-hoist-before-default-params-2/options.json

@@ -0,0 +1,8 @@
+{
+  "plugins": [
+    "transform-es2015-parameters",
+    "transform-react-constant-elements",
+    "transform-es2015-block-scoping",
+    "syntax-jsx"
+  ]
+}

packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/dont-hoist-before-default-params/actual.js

@@ -0,0 +1,5 @@
+function render(Component, text = '') {
+  return function() {
+    return <Component text={text} />;
+  }
+}

packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/dont-hoist-before-default-params/expected.js

@@ -0,0 +1,9 @@
+function render(Component) {
+  var text = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : '';
+
+  var _ref = <Component text={text} />;
+
+  return function () {
+    return _ref;
+  };
+}

packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/dont-hoist-before-default-params/options.json

@@ -0,0 +1,8 @@
+{
+  "plugins": [
+    "transform-es2015-parameters",
+    "transform-react-constant-elements",
+    "transform-es2015-block-scoping",
+    "syntax-jsx"
+  ]
+}

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

@@ -133,7 +133,14 @@ export default class PathHoister {
         if (this.scope === scope) return;
 
         // needs to be attached to the body
-        return scope.path.get("body").get("body")[0];
+        const bodies = scope.path.get("body").get("body");
+        for (let i = 0; i < bodies.length; i++) {
+          // Don't attach to something that's going to get hoisted,
+          // like a default parameter
+          if (bodies[i].node._blockHoist) continue;
+          return bodies[i];
+        }
+        // deopt: If here, no attachment path found
       } else {
         // doesn't need to be be attached to this scope
         return this.getNextScopeAttachmentParent();