AST: Allow non-canonical opaque archetypes #84299
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We cannot in general assume the substitution map's replacement types are written in terms of the generic signautre of the owner declaration. This was only necessary because this substitution map did not preserve type sugar, but now that it does, we no longer need this hack.
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…utions We need to serialize the underlying type substitution map for an inlinable function. However, there is no reason to deserialize it eagerly, since doing so can lead to cycles. It is better for correctness and performance to only deserialize it when needed. Technically this fixes a regression from swiftlang#84299, but the actual problem was there all along, it was just exposed by my change on a specific project. Fixes rdar://163301203.
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…utions We need to serialize the underlying type substitution map for an inlinable function. However, there is no reason to deserialize it eagerly, since doing so can lead to cycles. It is better for correctness and performance to only deserialize it when needed. Technically this fixes a regression from swiftlang#84299, but the actual problem was there all along, it was just exposed by my change on a specific project. Fixes rdar://163301203.
slavapestov
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Nov 19, 2025
…utions We need to serialize the underlying type substitution map for an inlinable function. However, there is no reason to deserialize it eagerly, since doing so can lead to cycles. It is better for correctness and performance to only deserialize it when needed. Technically this fixes a regression from swiftlang#84299, but the actual problem was there all along, it was just exposed by my change on a specific project. Fixes rdar://163301203.
slavapestov
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Nov 20, 2025
…utions We need to serialize the underlying type substitution map for an inlinable function. However, there is no reason to deserialize it eagerly, since doing so can lead to cycles. It is better for correctness and performance to only deserialize it when needed. Technically this fixes a regression from swiftlang#84299, but the actual problem was there all along, it was just exposed by my change on a specific project. Fixes rdar://163301203.
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An opaque archetype contains a substitution map. Previously, we required that all replacement types in this substitution map were canonical. This requires the ASTPrinter to re-sugaring generic parameter types in order to get something that round trips, and this re-sugaring was hacky and not fully correct.
Instead, let's just say that opaque archetypes can be non-canonical if their replacement types are non-canonical. Computing the canonical type of an opaque archetype then canonicalizes this substitution map.
This PR only changes opaque archetypes, but existential and pack element archetypes also store substitution maps, and they should receive the same treatment eventually too.