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Compiling pandoc-2.9.2.1 on GHC HEAD panics (applyTypeToArgs)

Originally observed on a head.hackage CI build here.

Attempting to compile pandoc-2.9.2.1 on GHC HEAD will result in the following panic:

[106 of 166] Compiling Text.Pandoc.Writers.Docx
ghc: panic! (the 'impossible' happened)
  (GHC version 8.11.0.20200403:
	applyTypeToArgs
  Expression: wild_a3j6U ys_a1Q2
  Type: Element
  Args: [ys_a1Q2]
  Call stack:
      CallStack (from HasCallStack):
        callStackDoc, called at compiler/utils/Outputable.hs:1228:37 in ghc:Outputable
        pprPanic, called at compiler/GHC/Core/Utils.hs:237:14 in ghc:GHC.Core.Utils

Unfortunately, the code that triggers the panic is quite massive, and I have had no luck attempting to minimize it. I did confirm that the commit that caused this regression is b943b25d (Re-engineer the binder-swap transformation), however.

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