On Tuesday, 23 June 2015 at 12:45:25 UTC, kink wrote:
On Tuesday, 23 June 2015 at 09:57:26 UTC, Marc Schütz wrote:
To guarantee this from the caller's POV, the callee must be
pure and the parameters must be known not to alias each other.
This is obviously true. Rvalues aren't affected as they cannot
alias another parameter by definition.
You're right, I didn't think of that! They are not _transitively_
unique, but there can indeed be no other references to the
rvalues themselves. So for rvalues, const is enough. Nice :-)
Lvalues are if passed by ref and the same instance is
accessible by mutable ref from another parameter or global. But
as shown by your example, that danger is always there. The
proposed `in` semantics make it less obvious, that's true, but
I still think it'd be worth it, as these aliasing bugs are a
pain to track down, but in my experience extremely rare.
