BuiltinCasing crashes on GHC.Prim.Addr# when a join point exposes Data in its type

[Unisay]

The plugin crashes when compiling a function with datatypes=BuiltinCasing if the GHC Core contains a join point with PlutusCore.Data.Data in its type:

Context: Compiling type: PlutusCore.Data.Data
Context: Compiling data constructor type: PlutusCore.Data.B
Context: Compiling type: Data.ByteString.Internal.Type.ByteString
Context: Compiling data constructor type: Data.ByteString.Internal.Type.BS
Context: Compiling type: GHC.Prim.Addr#
Error: Unsupported feature: Type constructor: GHC.Prim.Addr#

What happens

BuiltinData wraps PlutusCore.Data.Data. Normally the plugin treats BuiltinData as a builtin and never looks inside. But GHC's simplifier can produce join points where Data appears naked in the type signature:

$j :: Data -> BuiltinUnit

The plugin with BuiltinCasing tries to compile Data as a regular ADT, follows B ByteString → BS Addr# Int, and crashes because Addr# has no Plutus Core equivalent.

Reproduction

Branch with a failing test: yura/builtin-casing-addr-joinpoint

Minimal trigger — caseList' applied twice to the same value in a separate module without BuiltinCasing:

failsToCompile :: BuiltinData -> BuiltinUnit
failsToCompile bd =
  case toBuiltinData (firstOf items) of
    _ -> case toBuiltinData (firstOf items) of
      _ -> unitval
  where
    items = unsafeFromBuiltinData bd
    firstOf = caseList' Nothing (\(h :: BuiltinData) _t -> Just h)

Compiled from Spec.hs (which has datatypes=BuiltinCasing) via $$(compile [||Lib.failsToCompile||]).

cabal build plutus-tx-plugin-tests

No dependencies beyond plutus-tx and plutus-tx-plugin.

Originally discovered as

A cross-library compilation failure: a Plinth validator using findOwnInput + getContinuingOutputs from plutus-ledger-api crashed when compiled with BuiltinCasing. getContinuingOutputs calls findOwnInput internally, producing the double-call pattern that triggers the join point.