Reflect modern generics, opaque types & generalized existentials#77
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Reflect modern generics, opaque types & generalized existentials#77NSExceptional wants to merge 4 commits into
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GenericParameterKind only had .type, and GenericRequirementKind lacked .sameShape/.invertedProtocols, so the force-unwrapped rawValue decode crashed on any variadic-generic (each T), integer-generic (let N: Int), or noncopyable-generic type. Add: - GenericParameterKind: .typePack, .value - GenericRequirementKind: .sameShape, .invertedProtocols Test reflects a variadic-generic type and confirms its pack parameter decodes as .typePack without trapping.
OpaqueDescriptor.underlyingType(at:genericArguments:) resolves a 'some P' opaque type's mangled underlying-type name into a live metatype via the in-context resolver, threading the opaque descriptor's generic context. Out-of-range indices return nil. Test enumerates the image's opaque descriptors and confirms two opaque-returning functions' underlying types realize to Int and String.
…load) Adds GenericContext.descriptorFlags (hasTypePacks / hasConditionalInverted Protocols / hasValues), packShapeHeader, and packShapeDescriptors, decoding the GenericPackShapeHeader + GenericPackShapeDescriptor records that trail a variadic-generic context's parameters and requirements. Each descriptor reports its pack kind (metadata / witness-table), generic-argument index, and same-shape equivalence class. Also relaxes GenericRequirementDescriptor. mangledTypeName to accept .sameShape requirements. Tests confirm PackGeneric<each Element> exposes a metadata pack shape and a non-pack generic exposes none.
Reflecting a parameterized-protocol existential like 'any Collection<Int>' crashed Echo with 'unknown kind 775' (ExtendedExistential = 0x307). Adds the .extendedExistential MetadataKind, an ExtendedExistentialMetadata type exposing the existential shape, and ExtendedExistentialTypeShape with flags (specialKind: opaque/class/metatype/explicit-layout; hasGeneralization Signature / hasTypeExpression / hasSuggestedValueWitnesses), wired into getMetadata. Test reflects 'any Collection<Int>': kind .extendedExistential, the shape reports a generalization signature and opaque special kind, and the metadata round-trips; a plain 'any Equatable' still uses the classic layout.
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Summary
Completes modern-Swift type reflection: variadic/value generic parameters, parameter-pack shapes, opaque-type realization, and generalized (parameterized-protocol) existentials — the last of which was an outright crash.
New Features
Generic parameter & requirement kinds —
GenericParameterKindonly had.type, andGenericRequirementKindlacked.sameShape/.invertedProtocols, so the force-unwrapped decode crashed when reflecting any variadic-generic (each T), integer-generic (let N: Int), or noncopyable-constrained type. Adds.typePack/.valueand.sameShape/.invertedProtocols.Variadic-generic pack shapes (
GenericContext.swift) —descriptorFlags(hasTypePacks/hasConditionalInvertedProtocols/hasValues),packShapeHeader, andpackShapeDescriptors(pack kind, generic-argument index, same-shape equivalence class).Opaque type realization —
OpaqueDescriptor.underlyingType(at:genericArguments:)resolves asome Popaque type's mangled underlying type into a live metatype.Generalized existential metadata — reflecting
any Collection<Int>(a parameterized-protocol existential) crashed Echo with "unknown kind 775". Adds the.extendedExistentialMetadataKind, anExtendedExistentialMetadatatype, andExtendedExistentialTypeShape(special kind + generalization/type-expression/value-witness flags), wired intogetMetadata.Tests
Tests reflect a variadic-generic type (pack parameter decodes as
.typePack, pack shape exposes a metadata pack), realize two opaque-returning functions' underlying types toInt/Stringvia image enumeration, and reflectany Collection<Int>(kind.extendedExistential, generalization signature present, round-trips) while confirming a plainany Equatablekeeps the classic layout.swift testgreen (32 tests).