Migrated issue, originally created by Michael Bayer (@zzzeek)

I think we need a new method on type that's specific to rendering a type for literal SQL. At the moment, a string type on an encoding backend can pass in a bytes into render_literal_value (see test.sql.test_types:EnumTest.test_mock_engine_no_prob using Oracle backend on python3). We're working around this by re-decoding the bytes in the method, but more elaborate bind processor schemes will need to be aware of literal SQL and naturally this should be type-based in any case.