odd behavior/possible bug

I created a function thus:

CREATE OR REPLACE FUNCTION dwarray(anyelement, anyelement)
RETURNS anyarray AS '  SELECT ARRAY[$1,$2]
' LANGUAGE 'sql' IMMUTABLE STRICT;

My hope was to use STRICT to get the following behavior: if either or 
both arguments are NULL, I get a NULL. If both are non-NULL, I get an 
array. Seems simple enough at first glance. Here's what I get when I try 
it out:

regression=# select dwarray(1,2); dwarray
--------- {1,2}
(1 row)
regression=# select dwarray(1,null) is null; ?column?
---------- t
(1 row)

regression=# select dwarray(null,2) is null; ?column?
---------- t
(1 row)

So far so good. But look at this one:
regression=# select dwarray(null,null);
ERROR:  cannot determine ANYARRAY/ANYELEMENT type because input is UNKNOWN

This happens because enforce_generic_type_consistency() can't resolve 
the return type from the NULLs which are typed as UNKNOWN. This call is 
made from ParseFuncOrColumn().

Should ParseFuncOrColumn() bypass the call to 
enforce_generic_type_consistency() when all arguments are NULL?

The next item is a bit more strange. Create a table and load some data:
create table t(f1 int, f2 float, f3 float);
insert into t values(1,11.1,21.1);
insert into t values(1,11.2,21.2);
insert into t values(1,11.3,21.3);
insert into t values(1,11.4,null);
insert into t values(1,null,21.5);
insert into t values(1,null,null);

Now call the same function:
regression=# select dwarray(f2,f3) from t;
ERROR:  arrays cannot have NULL elements

This call makes it all the way to ExecEvalArray(), which means that 
dwarray() is getting evaluated even though it is declared STRICT and has 
been called with NULL inputs. That shouldn't happen, should it?

Joe