Sema: Fix non-determinism with ConstraintSystem::ConstraintRestrictions #80057
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Mar 17, 2025
We iterate over the DenseMap and simplify both types appearing in the key. If multiple keys simplify to the same type, later keys overwrite earlier keys, so the outcome depends on hash table order. Fix this by introducing an arbitrary tie break: we prefer the highest-numbered restriction. Fixes rdar://146780049.
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This fixes a regression from 62a470e.
We iterate over the DenseMap and simplify both types appearing
in the key. If multiple keys simplify to the same type, later
keys overwrite earlier keys, so the outcome depends on hash
table order.
Fix this by introducing an arbitrary tie break: we prefer the
highest-numbered restriction.
Fixes rdar://146780049.