Fix bug with importing empty type (#904)

src/printer.js

@@ -529,6 +529,8 @@ function genericPrintNoParens(path, options, print) {
         }
 
         fromParts.push(grouped.length === 0 ? line : " ", "from ");
+      } else if (n.importKind && n.importKind === "type") {
+        parts.push("{} from ");
       }
 
       fromParts.push(path.call(print, "source"), ";");

tests/flow/import_type/__snapshots__/jsfmt.spec.js.snap

@@ -353,12 +353,14 @@ exports[`import_type_specifier.js 1`] = `
  */
 
 import { Foo, type Baz } from \\"../module\\";
+import type {} from 'foo';
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 /**
  * @flow
  */
 
 import { Foo, type Baz } from \\"../module\\";
+import type {} from \\"foo\\";
 "
 `;
 

tests/flow/import_type/import_type_specifier.js

@@ -3,3 +3,4 @@
  */
 
 import { Foo, type Baz } from "../module";
+import type {} from 'foo';