On 01/11/2014 08:16 PM, Maxim Fomin wrote:
On Saturday, 11 January 2014 at 18:52:39 UTC, Adam D. Ruppe wrote:
On Saturday, 11 January 2014 at 18:48:15 UTC, Maxim Fomin wrote:
It is legal exactly because function is marked as pure. Result of
pure function is implicitly convertible to immutable.
It shouldn't be here though... the reason it is implicitly convertable
is that pure means the result is unique. But, with the hidden this
pointer having a reference to the data as well, it obviously is not
unique. I think the compiler should catch this; i'd call it a bug.
Creating undefined behavior is not a sufficient reason to be a bug.
...
Add a @safe annotation and it is.
Changelog mentions example with pure struct constructors which provide
value implicitly castable to immutable. So, strictly speaking current
behavior is conforming to spec.
You can still argue that the example does not address the issue with
'this' parameter, so code should be rejected (which should happen from
safity aspect). I think this case was not considered when 'unique
expression' was introduced, so it is yet another hole in type system (to
be more precise, bug is in spec-language, not compiler).
It is an implementation bug. Implicit conversion to immutable is only
supposed to work for strongly pure functions.
