Fix PathHoister error attaching after export declarations.

Fixes #5369.

See also 4ee385e96c/packages/babel-plugin-transform-class-properties/src/index.js (L167)

packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/regression-node-type-export-default/actual.js

@@ -0,0 +1,7 @@
+class A {
+    render() {
+        return <B />
+    }
+}
+
+export default class B {}

packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/regression-node-type-export-default/expected.js

@@ -0,0 +1,9 @@
+class A {
+    render() {
+        return _ref;
+    }
+}
+
+export default class B {}
+
+var _ref = React.createElement(B, null);

packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/regression-node-type-export-default/options.json

@@ -0,0 +1,6 @@
+{
+    "plugins": [
+        "transform-react-jsx",
+        "transform-react-constant-elements"
+    ]
+}

packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/regression-node-type-export/actual.js

@@ -0,0 +1,7 @@
+class A {
+    render() {
+        return <B />
+    }
+}
+
+export class B {}

packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/regression-node-type-export/expected.js

@@ -0,0 +1,9 @@
+class A {
+    render() {
+        return _ref;
+    }
+}
+
+export class B {}
+
+var _ref = React.createElement(B, null);

packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/regression-node-type-export/options.json

@@ -0,0 +1,6 @@
+{
+    "plugins": [
+        "transform-react-jsx",
+        "transform-react-constant-elements"
+    ]
+}

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

@@ -117,6 +117,12 @@ export default class PathHoister {
       }
     }
 
+    // We can't insert before/after a child of an export declaration, so move up
+    // to the declaration itself.
+    if (path.parentPath.isExportDeclaration()) {
+      path = path.parentPath;
+    }
+
     return path;
   }