There is also another counter-obvious bit regarding current
implementation - it only tracks lifetime of actual references.
Check this example:
ref int wrap ( return ref int input )
{
return input;
}
int badWrapper()
{
int z;
{
int x = 42;
z = wrap(x);
}
return z;
}
it looks obvious that this compiles OK with dip25 check because
once value assignment happens, there is no more reference to
track. However it is very common to expect different semantics if
return type contains reference types - probably because it would
be very useful and because Rust has changed expectations of what
lifetime control can do :) And yet it will still work exactly the
same with no warnings from compiler, creating false sense of
correctness.
