I took a cursory look at https://issues.dlang.org/show_bug.cgi?id=22626:

class Oops {
    synchronized void oops() {}
}

% dmd -o- -preview=nosharedaccess d.d
d.d(2): Error: direct access to shared this is not allowed, see core.atomic

But I soon got lost in the codebase. The issue is SharedCheckVisitor in expressionsem.d is checking this, which is shared, and thinks that access to it is disallowed since it has no idea that the member function is synchronized.

This is stopping me from transitioning nosharedaccess to be on by default.

On 3/7/22 12:47 PM, Atila Neves wrote:

Looking at the AST output, a synchronized function looks like:

synchronized shared void oops()
	{
		shared shared(Oops) __sync2 = this;
		_d_monitorenter(__sync2);
		_d_monitorexit(__sync2);
	}

If we type this all out (except for the synchronized attribute), then it fails on any of those calls (the copy of the parameter, or the direct calls to monitorenter or monitorexit).

Which brings the question -- how do you call a function with a shared this? If this isn't possible, then there is something wrong with the preview implementation -- you should be able to abstract out your sync routines into functions without requiring casts.

This might come down to the fact that the this reference itself (as in the pointer on the stack) is shared, not just the thing it refers to.

-Steve