reWriteBatchedInserts=true not working with ON CONFLICT DO UPDATE

When using the new reWriteBatchedInserts=true feature, this fails when using ON CONFLICT DO UPDATE ...

Assume the following table:

create table testbatch (x integer primary key, y integer)

And the following code:

pstmt = con.prepareStatement("insert into testbatch (x, y) values (?,?) on conflict (x) do update set y = exluded.y");
pstmt.setInt(1,1);
pstmt.setInt(2,1);
pstmt.addBatch();

pstmt.setInt(1,2);
pstmt.setInt(2,2);
pstmt.addBatch();

pstmt.executeBatch();

The executeBatch() fails with:

java.sql.BatchUpdateException: Batch entry 0

insert into testbatch (x, y) values (1,1) on conflict (x),(2,2) on conflict (x) do update set y = exluded.y was aborted: ERROR: syntax error at or near ","

It seems the rewrite code doesn't take the on conflict clause into account properly.

However, it _does_ work correctly with ON CONFLICT DO NOTHING

Tested with postgresql-42.0.0.jar

Regards
Thomas