Port #62275: Discard types that reduce to never before discriminating… #9461

Job	Run time
tidy	1m 26s
misc	1m 17s
format	1m 49s
generate	12m 25s
test (race mode)	18m 0s
test (no submodules)	8m 33s
extension	42s
build	4m 49s
lint (noembed)	6m 59s
lint (windows-latest)	17m 55s
test (noembed)	9m 47s
test (macos-latest)	13m 28s
test (ubuntu-latest)	12m 52s
test (concurrent test programs)	13m 18s
test (windows-latest)	22m 10s
smoke	6m 19s
lint (ubuntu-latest)	7m 11s
required	3s
	2h 39m 3s

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