[Issue 14251] synchronized (mtx) doesn't check attributes (pure, const)

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=14251

--- Comment #4 from github-bugzi...@puremagic.com ---
Commit pushed to master at https://github.com/D-Programming-Language/phobos

https://github.com/D-Programming-Language/phobos/commit/4b74c5f687a06d95c4ffe6e8aefe10f88acc098b
Remove deprecated `std.concurrency.MessageBox.isClosed() const`.

Within Phobos, this is the only occurrence of synchronizing on an immutable
object. Removal of this deprecated function allows us to resolve Issue 14251.

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