On Friday, 17 August 2018 at 13:39:29 UTC, Steven Schveighoffer
wrote:
On 8/17/18 3:36 AM, Atila Neves wrote:
Here's a struct:
-----------------
struct MyStruct {
import core.stdc.stdlib;
int* ints;
this(int size) @trusted { ints = cast(int*) malloc(size);
}
~this() @trusted { free(ints); }
scope int* ptr() { return ints; }
}
-----------------
Let's try and be evil with -dip1000:
-----------------
@safe:
// struct MyStruct ...
const(int) *gInt;
void main() {
auto s = MyStruct(10);
gInt = s.ptr;
}
-----------------
% dmd -dip1000 scope_inout.d
scope_inout.d(26): Error: scope variable this may not be
returned
Yay!
What if instead of `auto` I write `const` instead (or
immutable)? This is D we're talking about, so none of this
boilerplate nonsense of writing two (or three) basically
identical functions. So:
-----------------
// used to be scope int* ptr() { return ints; }
scope inout(int)* ptr() inout { return ints; }
Does scope apply to the return value or the `this` reference?
I assumed the return value. I think I've read DIP1000 about a
dozen times now and I still get confused. As opposed to `const`
or `immutable`, `scope(T)` isn't a thing so... I don't know?
What happens if you remove the return type? (i.e. scope auto)
And write what instead?
-----------------
% dmd -dip1000 scope_inout.d
% echo $?
0
# nope, no error here
Wait, what? Turns out now it compiles. After some
under-the-breath mumbling I go hit issues.dlang.org and
realise that the issue already exists:
https://issues.dlang.org/show_bug.cgi?id=17935
I don't see what this bug report has to do with the given case.
That's because I'm an idiot and I meant this one:
https://issues.dlang.org/show_bug.cgi?id=17927
This seems like a straight up bug.
I agree, but I also think #17935 is a straight up bug as well...
This doesn't surprise me. I'm beginning to question whether
scope shouldn't have been a type constructor instead of a
storage class. It's treated almost like a type constructor in
most places, but the language grammar makes it difficult to be
specific as to what part it applies.
I'm so confused it's not even funny.
