possibly to automatic detection of bad variable types in plans?

Hi

I have a talk with Alex Stanev about known issue that block indexes - bad
param types

postgres=# do $$
declare _id numeric = 777722;
begin
perform * from bigtable where a = _id;
end;
$$;
DO
Time: 108,775 ms
postgres=# do $$
declare _id numeric = 777722;
begin
perform * from bigtable where a = _id;
end;
$$;
DO
Time: 106,111 ms
postgres=# do $$
declare _id int = 777722;
begin
perform * from bigtable where a = _id;
end;
$$;
DO
Time: 1,522 ms
postgres=# do $$
declare _id numeric = 777722;
begin
perform * from bigtable where a = _id;
end;
$$;
DO
Time: 108,287 ms

https://github.com/okbob/plpgsql_check/issues/32

Is possible to write a extension, that raise warning so index is not
possible due bad parameter type, or so cast will be performed on every row?

It can be started like autoexplain.

Regards

Pavel