Fix long/double variable slot crash #650

Job	Run time
rust_ci (ubuntu-latest, stable)	1m 36s
rust_ci (macos-latest, stable)	1m 30s
rust_ci (macos-latest, beta)	2m 47s
rust_ci (ubuntu-latest, beta)	1m 22s
rust_ci (windows-latest, stable)	3m 5s
rust_ci (windows-latest, beta)	4m 38s
	14m 58s

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