Don’t repeat lookup work that may not round-trip #85517
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@slavapestov I think you might be the best person to review this. |
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Looks like we've fixed a compiler crasher with this diff: |
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Nov 15, 2025
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Sure, that’s reasonable. FWIW I’d like to get rid of the bound decl entirely at some point. Caching the result of these lookups is best handled at higher levels.
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validation-test/compiler_crashers/RequirementMachine-areReducedTypeParametersEqual-1801de.swift
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When a DeclRefTypeRepr is bound to a known declaration, the exact DeclNameRef used to create it is erased. This means that we no longer know exactly which module selector was used in the source code, so repeating the lookup with the same instance might produce different results. Avoid this problem by reusing the bound decl instead of trying to look up the same declaration again. Fixes rdar://164647850.
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When a DeclRefTypeRepr is bound to a known declaration, the exact DeclNameRef used to create it is erased. This means that we no longer know exactly which module selector was used in the source code, so repeating the lookup with the same instance might produce different results.
Avoid this problem by reusing the bound decl instead of trying to look up the same declaration again.
Fixes rdar://164647850.