Merge pull request #1305 from dhardy/gen_iter #552

Job	Run time
test-miri	4m 46s
test-cross (ubuntu-latest, mips-unknown-linux-gnu, stable)	3m 55s
test (ubuntu-latest, x86_64-unknown-linux-gnu, stable)	1m 48s
test (macos-latest, x86_64-apple-darwin, stable)	2m 34s
test (windows-latest, x86_64-pc-windows-gnu, stable)	6m 9s
test (windows-latest, x86_64-pc-windows-msvc, beta)	2m 19s
test (ubuntu-latest, x86_64-unknown-linux-gnu, MSRV, 1.56.0)	2m 53s
test (ubuntu-latest, sudo apt-get update ; sudo apt install gcc-multilib, i686-unknown-linux-gnu,...	3m 37s
test (ubuntu-latest, x86_64-unknown-linux-gnu, nightly, minimal_versions)	3m 28s
Check doc	2m 14s
test-ios	34s
test-no-std	19s
	34m 36s

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