[GSB] Basic infrastructure for delaying and reprocessing requirements #8707
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Rather than true (an error occurred) or false (the constraint was resolved), introduce ConstraintResult to better model what happened. NFC for now, but the intent here is to report unresolved constraints through this mechanism.
We were putting conformance requirements on the representative of the equivalence class, rather than directly on the potential archetype on which the conformance requirement was specified. This violates the invariant used when forming protocol-requirement sources that we never reseat a requirement onto the representative (which would have become a problem when implementing recursive protocol constreaints) as well as masking a GSB idempotency issue that comes from same-type requirements where the right-hand side was not guaranteed to refer to the archetype anchor *within* that subcomponent.
DougGregor
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@swift-ci please smoke test and merge |
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Foundation failure looks like a spurious networking issue. |
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@swift-ci please smoke test Linux |
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I mis-clicked the request for review button. Sorry : ( |
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The Linux failure will be addressed by swiftlang/swift-corelibs-foundation#945 |
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@swift-ci please smoke test Linux |
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@slavapestov RequirementResult would be better, probably. Will update |
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Start staging in support for delaying the processing of a requirement in the
GenericSignatureBuilderwhen one of the involved types cannot be immediately resolved. In such cases, stash the requirement to be resolved later. Most of this infrastructure is unused at this point, but is important for the detection of recursion in constraint systems.While here... fix an issue where the
GenericSignatureBuilderwas placing conformance requirements on the representative of the equivalence class rather than on the potential archetype that was named, which breaks some invariants. That in turn uncovered a latent idempotency problem in the GSB, where we wouldn't necessarily have the appropriate anchor within a component within the implied same-type constraint graphs.