sourcekitd: duplicate sourcekitd UIDs should fail the build. (swiftlang#14796)

This ensures we can safely add new UIDs.

Author: nkcsgexi

tools/SourceKit/include/SourceKit/Core/ProtocolUIDs.def.gyb

@@ -1,8 +1,7 @@
 %{
   # -*- mode: Python -*-
-  from gyb_sourcekit_support.UIDs import UID_KEYS
-  from gyb_sourcekit_support.UIDs import UID_REQUESTS
-  from gyb_sourcekit_support.UIDs import UID_KINDS
+  from gyb_sourcekit_support import *
+  assert check_uid_duplication(), "Found UID duplication"
   # Ignore the following admonition; it applies to the resulting .def file only
 }%
 //// Automatically Generated From ProtocolUIDs.def.gyb.

utils/gyb_sourcekit_support/__init__.py

@@ -14,3 +14,13 @@
 # utils/gyb_sourcekit_support/ directory as a module.
 #
 # ----------------------------------------------------------------------------
+from UIDs import UID_KEYS
+from UIDs import UID_KINDS
+from UIDs import UID_REQUESTS
+
+
+def check_uid_duplication():
+    all_external_names = [K.externalName for K in UID_KEYS] + \
+        [R.externalName for R in UID_REQUESTS] +              \
+        [K.externalName for K in UID_KINDS]
+    return len(all_external_names) == len(set(all_external_names))