Cannot take the .keys of shared AA. Is this a regression in 2.087 or a feature?

Jonathan M Davis newsgroup.d at
Thu Aug 15 19:51:30 UTC 2019

n Thursday, August 15, 2019 11:33:06 AM MDT Piotr Mitana via Digitalmars-d-
learn wrote:
> Code:
> import std;
> shared(string[string]) dict;
> void main()
> {
>      dict.keys;
> }
> Error:
> /dlang/dmd/linux/bin64/../../src/druntime/import/object.d(3417):
> Error: cannot implicitly convert expression aa of type
> shared(string[string]) to const(shared(string)[string])
> onlineapp.d(7): Error: template instance
> `object.keys!(shared(string[string]), shared(string), string)`
> error instantiating
> Before D 2.087 it compiled - is this a regression?

Not being able to implicitly convert to const is a bit odd, but arguably,
nothing should ever be called on a shared AA anyway. If an operation isn't
thread-safe, then it shouldn't work with shared. To use a shared object
safely, you have to protect access to it with a mutex or some other
synchronization mechanism, after which you would normally cast away shared
to operate on the object as thread-local while the lock is in place and then
release the lock when you're done (also making sure that no thread-local
references exist when the lock is released). Because keys is not at all
thread-safe, I'd strongly argue that it should not work on a shared AA, and
if it does, that's a bug.

- Jonathan M Davis

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