errors.As is meant to check whether err (or other error in its chain) can
be assigned to the value that target is pointing at.
Let's consider this example:
errors.As(err, &pgx.ErrNoRows)
pgx.ErrNoRows (and pgx.ErrTxClosed) is typed as error, thus in all
errors.As calls, the target is typed as *error. Err is always an error.
So this call is basically asking whether error can be assigned to error.
If err != nil, this is always true, thus this check doesn't make any sense
over a plain err != nil.
Go 1.19 now checks this issue and if it's found, it refuses to compile the
code, see:
https://go-review.googlesource.com/c/tools/+/339889
This commit changes usages of errors.As() to errors.Is(). The Is() method
doesn't check assignability but equality (the only different between Is()
and a plain old == operator is that Is() also inspects the whole error chain).
This fixes the check because now, we are basically checking if err (or
any other error in its chain) == pgx.ErrTxClosed which is exactly what we
want.
Signed-off-by: Ondřej Budai <ondrej@budai.cz>
9def545570