Improve rust parsing #4917

Job	Run time
maybe-expedite	7s
test (ubuntu-latest, third_party_0)	23m 52s
test (ubuntu-latest, third_party_1)	31m 10s
test (ubuntu-latest, trycmd)	3m 26s
test (ubuntu-latest, other)	5m 59s
test (macos-latest, third_party_0)	13m 8s
test (macos-latest, third_party_1)	28m 49s
test (macos-latest, trycmd)	3m 5s
test (macos-latest, other)	3m 35s
test (windows-latest, third_party_0)	21m 50s
test (windows-latest, third_party_1)	40m 17s
test (windows-latest, trycmd)	4m 48s
test (windows-latest, other)	7m 14s
test (ubuntu-latest, ci)	23m 7s
all-checks	1s
	3h 30m 28s

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