Possibly inconsistent type casting logic

In the old days, when every function of the form foo(bar) was a cast from
bar to foo, and if foo and bar happened to be binary compatible, the
system short-circuited this function call to do a "zero-effort" cast.

This logic still exists, but since in general casts are controlled
through pg_cast now, it seems inconsistent that the old system still
exists in some places. Did we forget that or is that intentional?

The consequence of this feature put in other words appears to be that "if
you create a binary-compatible cast from foo to bar, a function 'bar(foo)
returns bar' will magically appear to exist". Maybe that's fine, but then
we should probably document it more explicitly.

--
Peter Eisentraut peter_e(at)gmx(dot)net