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From: dewar@gnat.com (Robert Dewar)
Newsgroups: comp.lang.ada
Subject: Re: Refactoring and Ada
Date: 4 Feb 2002 09:59:41 -0800
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Richard Riehle <richard@adaworks.com> wrote in message news:<3C5E0ED6.E2D52BD3@adaworks.com>...
> Pat Rogers wrote:
> 
> >
> I still prefer renames clauses when only one or two
> operators  need direct
> visibility.    Use type can be as dangerous as the full 
> use clause under some circumstances.


I find this bad advice, so I would appreciate some further
evidence for this rather remarkable claim.

By the way, I talked to a never-ever-use-use user of Ada
the other day who was appalled to discover that even if
you don't use USE clauses, you can have a case where you
write

       a := f (x);

where there were no other occurrences of f in the same
source file, no USE clauses, and the textual declaration
of f was in another unit.

This is of course standard in both Ada 83 and Ada 95 (if
you don't know how it arises, and always assumed that avoiding use
clauses guaranteed that this could not happen,
you have always been fooling yourself :-)

I often find that people think that avoiding use clauses
avoids this, and requires full qualification. In fact in 
the above example, suppose the only other occurrence of
f is in package p, then it is the case that trying to
qualify by writing

       a := p.f (x);

is not just unnecessary, but in fact illegal. 

Implicit declarations often surprise people :-)