[NSError bridging] Use embedded NSError when erasing types to Error e… #3953
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…xistentials. Imported Cocoa error types are represented by structs wrapping an NSError. The conversion from these structs to Error would end up boxing the structs in _SwiftNativeNSError, losing identity and leading to a wrapping loop. Instead, extract the embedded NSError if there is one. In the Swift runtime, do this as part of the dynamic cast to NSError, using a (new, defaulted) requirement in the Error type so we can avoid an extra runtime lookup of the protocol. In SILGEn, do this by looking for the _BridgedStoredNSError protocol conformance when erasing to an Error type. Fixes SR-1562 / rdar://problem/26370984.
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@swift-ci please smoke test and merge |
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@jckarter , can you please review? |
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Whoops, missed a case. Will try again. |
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LGTM. |
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What's in this pull request?
Imported Cocoa error types are represented by structs wrapping an NSError. The conversion from these structs to Error would end up boxing the structs in _SwiftNativeNSError, losing identity and leading to a wrapping loop.
Instead, extract the embedded NSError if there is one. In the Swift runtime, do this as part of the dynamic cast to NSError, using a (new, defaulted) requirement in the Error type so we can avoid an extra runtime lookup of the protocol. In SILGEn, do this by looking for the _BridgedStoredNSError protocol conformance when erasing to an Error type.
Resolved bug number: (SR-1562)
AKA: rdar://problem/26370984
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…xistentials.
Imported Cocoa error types are represented by structs wrapping an
NSError. The conversion from these structs to Error would end up
boxing the structs in _SwiftNativeNSError, losing identity and leading
to a wrapping loop.
Instead, extract the embedded NSError if there is one. In the Swift
runtime, do this as part of the dynamic cast to NSError, using a (new,
defaulted) requirement in the Error type so we can avoid an extra
runtime lookup of the protocol. In SILGEn, do this by looking for the
_BridgedStoredNSError protocol conformance when erasing to an Error
type. Fixes SR-1562 / rdar://problem/26370984.