Add ID field to SourceKit's diagnostics

tools/SourceKit/docs/Protocol.md

@@ -310,6 +310,7 @@ entity ::=
 ```
 diagnostic ::=
 {
+    <key.id>:          (string) // The internal ID of the diagnostic.
     <key.line>:        (int64)  // The line upon which the diagnostic was emitted.
     <key.column>:      (int64)  // The column upon which the diagnostic was emitted.
     <key.filepath>:    (string) // The absolute path to the file that was being parsed

tools/SourceKit/include/SourceKit/Core/LangSupport.h

@@ -200,6 +200,7 @@ struct DiagnosticEntryInfoBase {
     std::string Text;
   };
 
+  std::string ID;
   std::string Description;
   unsigned Offset = 0;
   unsigned Line = 0;

tools/SourceKit/tools/sourcekitd/lib/API/Requests.cpp

@@ -2824,6 +2824,9 @@ static void fillDictionaryForDiagnosticInfo(
 static void fillDictionaryForDiagnosticInfoBase(
     ResponseBuilder::Dictionary Elem, const DiagnosticEntryInfoBase &Info) {
 
+  if (!Info.ID.empty())
+    Elem.set(KeyID, Info.ID);
+
   Elem.set(KeyDescription, Info.Description);
   if (Info.Line != 0) {
     Elem.set(KeyLine, Info.Line);

utils/gyb_sourcekit_support/UIDs.py

@@ -54,6 +54,7 @@ UID_KEYS = [
     KEY('EnableSyntaxMap', 'key.enablesyntaxmap'),
     KEY('SyntaxTreeTransferMode', 'key.syntaxtreetransfermode'),
     KEY('EnableStructure', 'key.enablesubstructure'),
+    KEY('ID', 'key.id'),
     KEY('Description', 'key.description'),
     KEY('TypeName', 'key.typename'),
     KEY('RuntimeName', 'key.runtime_name'),