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[SR-12044] Mirror reflection returns zero children for nested single-case enum #54480

stephencelis opened this issue Jan 16, 2020 · 2 comments


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@stephencelis stephencelis commented Jan 16, 2020

Previous ID SR-12044
Radar rdar://problem/58861157
Original Reporter @stephencelis
Type Bug
Status Resolved
Resolution Done

Swift 5.2

Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels Bug, Reflection, Runtime
Assignee None
Priority Medium

md5: 134d940a232a6725abd31fd2b65b1e77

Issue Description:

If you nest a single-case enum in another enum and try to reflect on the outer enum case, you cannot reflect on this inner value. For example, the following prints an empty array:

enum Inner { case innermost }
enum Outer { case inner(Inner) }
print(Array(Mirror(reflecting: Outer.inner(.innermost)).children))
// prints "[]"

On the other hand, adding a case to the single-case enum restores the ability to reflect on it:

enum Inner { case innermost, innermost2 }
enum Outer { case inner(Inner) }
print(Array(Mirror(reflecting: Outer.inner(.innermost)).children))
// prints "[(label: Optional("inner"), value: Inner.innermost)]"

My current workaround involves checking the memory layout size of Inner and if it's zero then I unsafely bitcast a value of Void.

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@beccadax beccadax commented Jan 24, 2020

@swift-ci create

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@slavapestov slavapestov commented Feb 19, 2020

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
This issue was closed.
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