Problem with do_quote_ident()

I see in quote.c::do_quote_ident():

*cp2++ = '"';
while (len-- > 0)
{
if (*cp1 == '"')
*cp2++ = '"';
if (*cp1 == '\\')
*cp2++ = '\\';
*cp2++ = *cp1++;
}
*cp2++ = '"';

I am confused by the backslash handling. In my tests, a backslash in a
double-quoted string does not require two backslashes:

test=> create user "a\d";
CREATE USER
test=> select usename, length(usename) from pg_user;
usename | length
----------+--------
a\d | 3

This is because a double-quote in a double-quoted string is entered as
"", not \".

Is it adding another backslash because it assumes the result will appear
in another quoted string?

--
Bruce Momjian | http://candle.pha.pa.us
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