Improve `opt_expr` performance #329

Job	Run time
pre_job	4s
pre_docs_job	5s
Reusable build (ubuntu-latest)	11m 16s
Reusable build (macos-latest)	5m 14s
Run docs tests (ubuntu-latest)	50s
Run tests (ubuntu-latest)	25m 25s
Run tests (macos-latest)	21m 0s
	1h 3m 54s

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