When an error import would conflict with another method,

preserve the original method name.

This heuristic is based on the Objective-C selector and therefore
doesn't really handle factory methods that would conflict with
initializers, but we can hope that those simply don't come up in
the wild.

It's not clear that this is the best thing to do --- it tends to
promote the non-throwing API over what's probably a newer, throwing
API --- but it's significantly easier, and it unblocks code without
creating deployment problems.

Swift SVN r28066

lib/Serialization/Serialization.cpp

@@ -1829,6 +1829,7 @@ void Serializer::writeForeignErrorConvention(const ForeignErrorConvention &fec){
 
   auto kind = getRawStableForeignErrorConventionKind(fec.getKind());
   uint8_t isOwned = fec.isErrorOwned() == ForeignErrorConvention::IsOwned;
+  uint8_t isReplaced = bool(fec.isErrorParameterReplacedWithVoid());
   TypeID errorParameterTypeID = addTypeRef(fec.getErrorParameterType());
   TypeID resultTypeID;
   switch (fec.getKind()) {
@@ -1847,6 +1848,7 @@ void Serializer::writeForeignErrorConvention(const ForeignErrorConvention &fec){
   ForeignErrorConventionLayout::emitRecord(Out, ScratchRecord, abbrCode,
                                            static_cast<uint8_t>(kind),
                                            isOwned,
+                                           isReplaced,
                                            fec.getErrorParameterIndex(),
                                            errorParameterTypeID,
                                            resultTypeID);