This is getting too muddled, so I'm going to summarise thusly; I believe the
principle the OP raised is sound, that any initialiser performing a lossy
conversion from another type should be clear that this happening, and that a
label can do that best, as it makes the conversion self-documenting at the
call-site.
Consider for example; with type-inference it's not always obvious what the type
of a variable is, and an unlabelled initialiser does nothing to help, like-so:
var someValue = someMethod()
…
var someInt = Int(someValue)
At a glance it's not all obvious what is happening to someValue here; in fact
I'd argue that this looks like a lossless conversion, requiring you to find out
that someMethod() returns a Float before you can know for sure what's really
going on. Whereas the following is more clear:
var someValue = someMethod()
…
var someInt = Int(truncating: someValue)
It may not communicate everything that's happening, but at least now it's clear
at a glance that something is happening, and the term truncating suggests that
something is being lost/removed from someValue.
Now I don't really care if truncating is the best term for it or not, though I
do still think it is and won't change my mind on that; the key thing here is
that it's providing that extra safety to developers by making it clear that an
important conversion is taking place, and this to me is more consistent with
other initialisers on Int etc. where distinctions are made between types that
can and cannot be represented exactly.
I'm not saying it should be limited to floats either; I think any initialiser
that cannot, or may not, represent the passed value accurately should be
labelled for clarity. So passing an Int16 into Int32(_:) would be fine for
example, but the reverse should not be.
It's not just an issue of new developers; experienced ones make mistakes too,
or forget to consider whether the conversion will impact their code. A label
helps, though I still think forcing a decision on rounding is even better, as
both prevent a developer from simply throwing in a value in a way that may be a
mistake._______________________________________________
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