On 6/10/22 3:46 AM, Mike Parker wrote:
On Friday, 10 June 2022 at 07:35:17 UTC, Bastiaan Veelo wrote:
Is there a use case where this makes sense? I would have much
appreciated the compiler slapping me on the fingers, but it doesn't. I
understand that it is safe and that the compiler can allow this, but
why would anyone want that? D-scanner does not check for this either.
Any initialization of a member field is overriding the field's `.init`
value for the type. If a dynamic allocation set a different value per
instance, then you'd have inconsistent behavior with, e.g., `int a = 5`.
Yes, it can't be done the way that is expected (which is common to many
languages): allocate one for every instance.
I think a helpful error message would be: "Error: The initializer
`A(5)` allocates memory that is shared among all instances of `S`. If
you want that, make `S.a` `static`."
I understand that it's not something that people expect, but making it
an error can't be the answer. And making it a static field is not the
same thing.
I think this is a case where having a warning that's on by default, and
which can be explicitly disabled, is useful. "Blah blah .init blah blah.
See link-to-something-in-docs. Is this what you intended?"
Here the language is being extremely unsafe.
Not only is the field shared between instances, it's shared across
instances in *different threads*.
Discovered circa 2009: https://issues.dlang.org/show_bug.cgi?id=2947
It should be illegal to declare a field this way that has mutable
references without being `shared`. End of story.
-Steve
