[Issue 6856] Preconditions are not inherited

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=6856



--- Comment #19 from Stewart Gordon <smjg at iname.com> 2012-02-26 09:15:32 PST ---
(In reply to comment #17)
> That assumption is bogus, because this is almost never the case.  
> It makes contract programming basically unusable.  Such a strong 
> weakening of the 'in' contract should not be the default.

It depends on how you look at it.  A function can, by default, accept 
any arguments of the types specified.  I think the view taken is that 
the in contract supplements the parameter list, and the absence of an 
in contract with a given parameter list denotes an absence of further 
restrictions on what may be passed into the function.

> Don's proposal is to remove 'in' contract widening completely.  
> That does not make a lot of sense to me.

Indeed, it does seem that Don doesn't like contravariance.

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