breaking: disallow state mutations in logic block expression #13625
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The problem of mutations in logic block expressions has come up a dozen or so times now, the latest is #13446. The common one is sorting in the expression:
This PR changes it so block effects behave a bit like deriveds and forbid state mutations. This in turn will help developers find issues in their applications quickly by hitting the error about unsafe mutations rather than too many updates error message which is harder to track down.