Make the typescript preset require a filename unless the user configured it for general use.

packages/babel-plugin-syntax-flow/src/index.js

@@ -9,6 +9,16 @@ export default declare((api, options) => {
 
   return {
     manipulateOptions(opts, parserOpts) {
+      // If the file has already enabled TS, assume that this is not a
+      // valid Flowtype file.
+      if (
+        parserOpts.plugins.some(
+          p => (Array.isArray(p) ? p[0] : p) === "typescript",
+        )
+      ) {
+        return;
+      }
+
       parserOpts.plugins.push(["flow", { all }]);
     },
   };