explain doesn't work with execute using

Hello

I found following bug - using explain in stored procedures like:

CREATE OR REPLACE FUNCTION test(int)
RETURNS void AS $$
DECLARE s varchar;
BEGIN FOR s IN EXECUTE 'EXPLAIN SELECT * FROM o WHERE a = $1+1' USING $1 LOOP   RAISE NOTICE '%', s; END LOOP;
END; $$
LANGUAGE plpgsql;

produce wrong result. Real plan is correct, etc variables are
substituted. Bud this explain show variables. Reason is in difference
in pflags. Planner works with PARAM_FLAG_CONST's variables, but
explain (proc ExplainQuery) get variables from Portal, where flag
PARAM_FLAG_CONST is lost.

Portal
SPI_cursor_open_with_args(const char *name,                                                 const char *src,
                                    int nargs, Oid *argtypes,                                                 Datum
*Values,const
 
char *Nulls,                                                 bool read_only, int
cursorOptions)
{  ...       paramLI = _SPI_convert_params(nargs, argtypes,
   Values, Nulls,
 

PARAM_FLAG_CONST);
      // variables are correct

but      result = SPI_cursor_open(name, &plan, Values, Nulls, read_only);      // result->portalParams lost flags

Portal
SPI_cursor_open(const char *name, SPIPlanPtr plan,                               Datum *Values, const char *Nulls,
                        bool read_only)
 
{       CachedPlanSource *plansource;       CachedPlan *cplan;       List       *stmt_list;       char
*query_string;      ParamListInfo paramLI;....       if (plan->nargs > 0)       {               /*
sizeof(ParamListInfoData)includes the first array
 
element */               paramLI = (ParamListInfo) palloc(sizeof(ParamListInfoData) +

(plan->nargs - 1) *sizeof(ParamExternData));               paramLI->numParams = plan->nargs;
               for (k = 0; k < plan->nargs; k++)               {                       ParamExternData *prm =
¶mLI->params[k];
                       prm->ptype = plan->argtypes[k];

/***************************************************/                       prm->pflags = 0; // correct flags is
overwritten
/***************************************************/                       prm->isnull = (Nulls && Nulls[k] == 'n');
                   if (prm->isnull)                       {                               /* nulls just copy */
                     prm->value = Values[k];                       }
 

so this is strange bug - EXECUTE USING use well plan, but isn't
possible verify it.

Regards
Pavel Stehule