On Wednesday, 22 August 2018 at 09:05:13 UTC, Walter Bright wrote:
On 8/21/2018 8:58 PM, Nicholas Wilson wrote:
On Tuesday, 21 August 2018 at 14:31:02 UTC, Atila Neves wrote:
The problem is that the code we write doesn't deal directly
with pointers - see the recent confusion in this forum over
where `scope` on the left applies to the `this` pointer or
the one returned by the member function.
Kagamin just told me I needed to use `return` instead of
`scope` to get things to work and I'm still not sure why.
The way I think about it is if you have a function that takes
a pointer, any pointer, and either returns it or a pointer
derived from it (dereferencing or indexing) that argument must
be marked `return`. In your case it was a pointer derived from
`this` so `return` must be applied to `this`.
Another way to think about it is this:
S s;
return &s;
We all know that is an error. The idea is to have a way to
express that for:
S s;
return s.foo();
and:
S s;
return foo(&s);
so that the compiler knows that the return value of foo() is
attached to the lifetime of s. Pretty much everything flows
from that.
Would the guideline below be correct?
"Add scope to every non-template member function that isn't meant
to escape this and add return to every non-template member
function that returns all or part of `this` by pointer or ref if
you want the compiler to check that nothing gets escaped in @safe
code."
