[GenericSignatureBuilder] Remove self-derived same-type-to-concrete constraints. #7812
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Whenever we create a (root) requirement source, associate it with the potential archetype on which the requirement is written. This lets us follow a requirement source from the (stated or implied) requirement on the root potential archetype to the effective requirement on the resulting potential archetype. Introduce FloatingRequirementSource for the cases where we need to state what the root source is, but don't yet have a potential archetype to attach it to. These get internally resolved to RequirementSources as soon as possible.
Use TrailingObjects to help us efficiently store the root potential archetype within requirement sources, so we can reconstruct the complete path from the point where a requirement was created to the potential archetype it affects. The test changes are because we are now dumping the root potential archetype as part of -debug-generic-signatures.
Introduce an operation on RequirementSource to determine whether a constraint with such a source, when it lands on a given potential archetype, is "self-derived": e.g., the final constraint is derived from the original constraint. Remove such constraints from the system during finalization, because otherwise they would make the original constraint redundant. Fixes rdar://problem/30478915, although we still need to apply this same logic to other kinds of constraints in the system.
DougGregor
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DougGregor
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@swift-ci please smoke test and merge |
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@shahmishal, any idea why I'm unable to trigger CI? |
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@swift-ci please smoke test and merge |
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GitHub Status (https://status.github.com/messages)
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Okay, thank you @shahmishal ! |
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Introduce an operation on
RequirementSourceto determine whether aconstraint with such a source, when it lands on a given potential
archetype, is "self-derived": e.g., the final constraint is derived
from the original constraint. Remove such constraints from the system
during finalization, because otherwise they would make the original
constraint redundant.
To get here, extend
RequirementSourceto store the rootPotentialArchetype(on which the constraint was generated) as well as theAssociatedTypeDeclfor each nested type access. We can now follow the paths more predictably.Fixes rdar://problem/30478915, although we still need to apply this
same logic to other kinds of constraints in the system.