Comment parsing: allow parsing comments with invalid source locations -- these

come from serialized modules


Swift SVN r15104

include/swift/Basic/SourceLoc.h

@@ -50,6 +50,12 @@ public:
         llvm::SMLoc::getFromPointer(Value.getPointer() + ByteOffset));
   }
 
+  SourceLoc getAdvancedLocOrInvalid(int ByteOffset) const {
+    if (isValid())
+      return getAdvancedLoc(ByteOffset);
+    return SourceLoc();
+  }
+
   /// Print out the SourceLoc.  If this location is in the same buffer
   /// as specified by \c LastBufferID, then we don't print the filename.  If
   /// not, we do print the filename, and then update \c LastBufferID with the