Key lookup failure on save

[wz1000]

Steps to reproduce:

1. Edit a file
2. Save the file

DEBUG] Starting: (2,0):[DelayedAction: FileStoreTC,DelayedAction: ParentTC]
[DEBUG] finish shakeRun: batch (took 0.08s, exception: Error when running Shake build system:
  at error, called at ./Data/HashMap/Base.hs:631:16 in unordered-containers-0.2.10.0-dc6e10219c0a2baf381b92e75f02b1280582860e9675d123989f5554e67cf4d1:Data.HashMap.Base
* Raised the exception:
Data.HashMap.Base.(!): key not found

Seems to be mostly harmless, but concerning.

[fendor]

Just observed the same on latest hls.

[mpickering]

I think this is coming from the typecheckParents function.