On Wed, Oct 17, 2018 at 6:15 AM Timon Gehr via Digitalmars-d <digitalmars-d@puremagic.com> wrote: > > On 17.10.2018 14:24, Timon Gehr wrote: > > and unshared methods are only allowed to access unshared members. > > This is actually not necessary, let me reformulate: > > You want: > > - if you have a C c and a shared(C) s, typeof(s.x) == typeof(c.x).
No. c.x is mutable, s.x is shared (and inaccessible). > - shared methods are not allowed to access unshared members. No. Shared methods are not allowed to access ANY members. Shared data has no access. I don't believe there's any rules that can make raw access to shared data safe. We must depend on threadsafe tooling (libraries). > - shared is not transitive, and therefore unshared class references > implicitly convert to shared class references No. Shared is transitive. > Applied to pointers, this would mean that you can implicitly convert > int* -> shared(int*), but not shared(int*)->int*, int* -> shared(int)* > or shared(int)* -> int*. Correct. This is acceptable because shared(int)* can not be accessed; can't produce to a race. shared -> unshared conversion produces an unshared alias, and is obviously invalid. > shared(int*) and shared(shared(int)*) would be > different types, such that shared(int*) cannot be dereferenced but > shared(shared(int)*) can. No. No manner of shared(T) is safely accessible under any circumstance. This is just the reality, and there's no way it can be allowed. The escape hatch is that T may have some shared methods which implement threadsafe interaction with T, and THAT is the only safe way to interact with shared data.
