We should not garbage collect hashtable key #580

Job	Run time
rust_ci (macos-latest, beta)	1m 26s
rust_ci (windows-latest, stable)	2m 10s
rust_ci (macos-latest, stable)	47s
rust_ci (ubuntu-latest, stable)	48s
rust_ci (ubuntu-latest, beta)	1m 29s
rust_ci (windows-latest, beta)	3m 9s
	9m 49s

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