Re: BUG #2954: null is not checked against domain constraints in return clause

I believe the bug to be here:

/* Normal case for scalar results */
estate->retval = exec_eval_expr(estate, stmt->expr,
&(estate->retisnull),
&(estate->rettype));

in exec_stmt_return() in pl_exec.c.

As I understand it, exec_eval_expr overwrites(!) estate->rettype instead
of casting the result to it.

What should be done is something like:

Datum value;
Oid valtype;

value = exec_eval_expr(estate, stmt->expr, &(estate->retisnull),
&valtype);

estate->retval = exec_cast_value(value, valtype, estate->rettype,
reqinput,
reqioparam,
reqtypmod,
estate->retisnull);

but where to get reqinput, reqioparam and reqtypmod? They should be
accessed through estate pointer, I think.