Forbid abstract or interface instantiation #642

Job	Run time
rust_ci (macos-latest, beta)	1m 29s
rust_ci (ubuntu-latest, stable)	1m 5s
rust_ci (macos-latest, stable)	1m 37s
rust_ci (ubuntu-latest, beta)	1m 29s
rust_ci (windows-latest, beta)	3m 15s
rust_ci (windows-latest, stable)	2m 22s
	11m 17s

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