Le 20/06/2012 16:55, Timon Gehr a écrit :
It works if implicit conversions from 'R delegate(A)' to
'R delegate(A) const' are allowed, as well as looking up an
'R delegate(A) in a const receiver object.
What about conversion from/to immutable ?
Simple application of transitivity. This part is the same for 1./2.
'R delegate(A)' and 'R delegate(A) const' are not convertible to
'R delegate(A) immutable', but 'R delegate(A) immutable' is
convertible to 'R delegate(A)' and 'R delegate(A) const'.
'R delegate(A)' and 'R delegate(A) const' decay to
'R delegate(A) immutable' when stored in an immutable object.
I've gone through a similar reasoning. It does not work. Here are
implicit casts summed up :
mutable -> const
immutable -> const
immutable -> mutable
which implicitely imply immutable -> const
And then you add when storing in immutable object.
mutable -> immutable
const -> immutable
It means that you can store a delegate that have a mutable frame pointer
into an immutable object, which break transitivity.
