add back in identifier

packages/babel-generator/src/generators/types.js

@@ -4,6 +4,18 @@
 import * as t from "babel-types";
 
 export function Identifier(node: Object) {
+  // FIXME: We hang variance off Identifer to support Flow's def-site variance.
+  // This is a terrible hack, but changing type annotations to use a new,
+  // dedicated node would be a breaking change. This should be cleaned up in
+  // the next major.
+  if (node.variance) {
+    if (node.variance === "plus") {
+      this.push("+");
+    } else if (node.variance === "minus") {
+      this.push("-");
+    }
+  }
+
   this.push(node.name);
 }