Fix Issue 2450 - Error using operators from named template mixin

[RazvanN7]

template Event() {
	void opCall() { }
	void opAddAssign(int i) { }
}
class Button {
	mixin Event clicked;
	void func() {
		clicked.opCall(); // works
		this.clicked();   // works   => should not work, fixed by this patch

		// Error: function expected before (), not mixin Event!() clicked; of type void
		clicked();
		// Error: mixin 'Event!()' is not a variable
		clicked += 7;
	}
}

Operator overloading applies only for structs and classes (aggregated declarations), not for template declaration, so the expectation that a named mixin should call opCall (like in the above example) is invalid. The patch makes it so that when this.clicked() is rejected by the compiler.

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	2450	normal	Error using operators from named template mixin

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub fetch digger
dub run digger -- build "master + dmd#10406"

[thewilsonator]

mixin Event!() would still allow that, right? its only explicitly naming the mixin that causes the error now?

If so I approve.

[RazvanN7]

Yes. It disallows calling opCall when using just the name of the mixin with ().

[BorisCarvajal]

While I was trying to fix another issue I discovered a test that is not fixed by this pull, so I'm pushing a patch touching the root of the problem and moving the other test (part of test33() from runnable/mixin1.d) to fail_compilation/fail2450.d.