Move is_bit_set into match body #1517

Job	Run time
Wheel on macos-latest py-3.7	6m 3s
Wheel on ubuntu-latest py-3.7	4m 38s
Wheel on windows-latest py-3.7	3m 34s
Checks	1m 22s
coverage	20m 23s
Run fuzz targets (macos-latest, 3.7)	44m 58s
Run fuzz targets (ubuntu-latest, 3.7)	31m 7s
Unit tests (macos-latest, 3.7)	8m 59s
Unit tests (ubuntu-latest, 3.7)	5m 54s
Unit tests (windows-latest, 3.7)	11m 26s
	2h 18m 24s

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