Re: Implicit coercions need to be reined in

Tom Lane wrote:
> Thomas Lockhart <thomas@fourpalms.org> writes:
> >> It's one thing to say that "apples || oranges" should
> >> be interpreted as "apples::text || oranges::text", but it is quite
> >> another to say that "apples <= oranges" should be handled that way.
> 
> > Hmm. istm that we might need some information to travel with the
> > operators, not just the coersion functions themselves. We have a fairly
> > type-rich system, but need to preserve the ability to add types and a
> > *partial* set of functions and operators and get reasonable behaviors.
> 
> Could we do anything based on looking at the whole set of candidate
> operators?  For example, I think that the reason "apples || oranges"
> is so appealing is that there really is only one way to interpret
> the || operator; whereas of course there are lots of different <=
> operators.  Perhaps we could be more forgiving of implicit coercions
> when there are fewer candidate operators, in some way?  Again, something
> based on type categories would make sense to me.  Perhaps allow
> cross-category implicit coercions only if there are no candidate
> operators accepting the input's native category?

Yes, I think any solution will have to consider the number of possible
conversions for a given mix of function/args.

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