False warning for if statement on box var

[Chuck]

class X

	def main is shared
		x = X()
		x.compute

	var _foo as X?
	
	def compute
		if _foo
			.bar
			if _foo  # false warning here since .bar can change _foo
				.bar
	
	def bar
		_foo = nil

The warning is: foo.cobra(12): warning: The expression "_foo" (of type "X") will always evaluate to true because it is not nilable. You can remove the expression.

This is low priority as it comes up rarely.

[hopscc]

patch for failure of warning suppression on Boxes.cobra:853
see
 Spurious warning on compiler compile

[Chuck]

The problem addressed by the patch has been fixed, although I took a different approach and more importantly, added a test case to lock this down. changeset:1620

Note that the patch does not address the issue described by this ticket. It should not be confused as a fix for this ticket.