[SR-8855] Runtime crash when Mirror attempts to access type metadata

[swift-ci]

Previous ID	SR-8855
Radar	rdar://problem/44797569
Original Reporter	xardas (JIRA User)
Type	Bug

Attachment: Download

Environment

Xcode 10.0 (10A255), macOS 10.13.6, Swift 4.2

Additional Detail from JIRA

Votes	0
Component/s	Standard Library
Labels	Bug, 4.2Regression, Runtime
Assignee	None
Priority	Medium

md5: 691b9dcf74ebd3cd90c21b42c5c53192

Issue Description:

There is EXC_BAD_ACCESS crash during attempt to access Mirror's child when mirror reflects generic with type constraints resolved to another generic type.

Crash is always reproducible on Xcode 10 but non-reproducible on Xcode 9.

Stacktrace and sample project is attached.

[belkadan]

@swift-ci create

[swift-ci]

Comment by Roman Ermolov (JIRA)

@belkadan it seems that the bug is fixed (checked it on Xcode 10.1 10B61).

[belkadan]

Thanks! @mikeash, @slavapestov, do you know what would have fixed it?