[ fix ] Address some proofs of void via impossible from issues #2250 … #994

Job	Run time
initialise	3s
quick-check	5m 50s
ubuntu-bootstrap-racket	12m 22s
ubuntu-bootstrap-chez	7m 16s
nix-bootstrap-chez	20m 9s
macos-bootstrap-chez	6m 43s
ubuntu-self-host-previous-version	10m 30s
windows-bootstrap-chez	22m 40s
macos-self-host-chez	14m 13s
ubuntu-build-api	4m 3s
ubuntu-self-host-chez	10m 46s
ub-test-frex	3m 50s
ub-test-elab-util	36s
ub-test-collie	17s
ub-pack-test-pack	12m 0s
ub-pack-test-lsp	14m 42s
ub-test-katla-and-html	5m 56s
ubuntu-self-host-racket	0s
windows-self-host-racket	11m 36s
	2h 43m 32s

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