clang-format: [TypeScript] Fix bug in handling of non-null operator.

Before:
  var i = x!-1;

After:
  var i = x! - 1;

llvm-svn: 286367
diff --git a/clang/unittests/Format/FormatTestJS.cpp b/clang/unittests/Format/FormatTestJS.cpp
index f4b5059..7641598 100644
--- a/clang/unittests/Format/FormatTestJS.cpp
+++ b/clang/unittests/Format/FormatTestJS.cpp
@@ -1462,6 +1462,7 @@
   verifyFormat("let x = !foo;\n");
   verifyFormat("let x = foo[0]!;\n");
   verifyFormat("let x = (foo)!;\n");
+  verifyFormat("let x = foo! - 1;\n");
   verifyFormat("let x = {foo: 1}!;\n");
 }