VirtualVariable: Add some accessors for type safety. #527

Job	Run time
macos / Test macOS	25s
ci / Build	3m 22s
windows / Test Windows	32s
ci / Lint	53s
ci / Typecheck	59s
ci / Test (0)	7m 37s
ci / Test (1)	5m 51s
ci / Test (2)	4m 12s
ci / Test (3)	6m 18s
ci / Test (4)	7m 10s
ci / Test (5)	5m 21s
ci / Test (6)	4m 38s
ci / Test (7)	5m 5s
ci / Test (8)	6m 19s
ci / Test (9)	6m 10s
ci / Publish Unit Tests Results	1s
	1h 4m 53s

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