presto-spi/src/main/java/io/prestosql/spi/type/TypeSignatureParameter.java/TypeSignatureParameter/anonymousField
class TypeSignatureParameter:    public static TypeSignatureParameter anonymousField(TypeSignature type)
    {
        return new TypeSignatureParameter(ParameterKind.NAMED_TYPE, new NamedTypeSignature(Optional.empty(), type));
    }