add support for export types

packages/babylon/src/plugins/flow.js

@@ -669,6 +669,39 @@ export default function (instance) {
     };
   });
 
+  instance.extend("parseExport", function (inner) {
+    return function (node) {
+      node = inner.call(this, node);
+      if (node.type === "ExportNamedDeclaration") {
+        node.exportKind = node.exportKind || "value";
+      }
+      return node;
+    };
+  });
+
+  instance.extend("parseExportDeclaration", function (inner) {
+    return function (node) {
+      if (this.isContextual("type")) {
+        node.exportKind = "type";
+
+        var declarationNode = this.startNode();
+        this.next();
+
+        if (this.match(tt.braceL)) {
+          // export type { foo, bar };
+          node.specifiers = this.parseExportSpecifiers();
+          this.parseExportFrom(node);
+          return null;
+        } else {
+          // export type Foo = Bar;
+          return this.flowParseTypeAlias(declarationNode);
+        }
+      } else {
+        return inner.call(this, node);
+      }
+    };
+  });
+
   instance.extend("parseClassId", function (inner) {
     return function (node, isStatement) {
       inner.call(this, node, isStatement);