anchor.diff:  
   %%
   -spec infer_col_type(#ddl_v1{}, selection(), Errors1::[any()]) ->
  -        {Type::simple_field_type(), Errors2::[any()]}.
  +        {Type::simple_field_type() | error, Errors2::[any()]}.
   infer_col_type(_, {Type, _}, Errors) when Type == sint64; Type == varchar;
                                             Type == boolean; Type == double ->
       {Type, Errors};
  
positive.code: prepend_select_columns(V, Acc) ->
      [V | Acc].
  
  %%
  compile_select_clause(DDL, ?SQL_SELECT{'SELECT' = #riak_sel_clause_v1{ clause = Sel } } = Q) ->
      CompileColFn = 
  
negative.code:     %% iterate from the right so we can append to the head of lists
      {ResultTypeSet, Q2} = lists:foldl(CompileColFn, Acc, Sel),
  
      {ColTypes, Errors} = my_mapfoldl(
          fun(ColASTX, Errors) ->
              infer_col_type(DDL, ColASTX, Errors)
          end, [], Sel),
  