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This program is derived from #16376 (closed):

{-# LANGUAGE TypeApplications #-}
module Bug where

h x = let f = id @Maybe
      in Just f

If you compile with -fdefer-type-errors -dcore-lint you'll get

*** Core Lint errors : in result of Desugar (before optimization) ***
<no location info>: warning:
    In the expression: f_arZ @ a_at1
    Out of scope: f_arZ :: forall a. a
                  [LclId]
*** Offending Program ***
Rec {
$trModule :: Module
[LclIdX]
$trModule = Module (TrNameS "main"#) (TrNameS "T16376"#)

h :: forall p a. p -> Maybe a
[LclIdX]
h = \ (@ p_asV) (@ a_at1) ->
      case typeError
             @ ('TupleRep '[])
             @ ((* -> *) ~# *)
             "T16376.hs:4:19: error:\n\
             \    \\226\\128\\162 Expecting one more argument to \\226\\128\\152Maybe\\226\\128\\153\n\
             \      Expected a type, but \\226\\128\\152Maybe\\226\\128\\153 has kind \\226\\128\\152* -> *\\226\\128\\153\n\
             \    \\226\\128\\162 In the type \\226\\128\\152Maybe\\226\\128\\153\n\
             \      In the expression: id @Maybe\n\
             \      In an equation for \\226\\128\\152f\\226\\128\\153: f = id @Maybe\n\
             \(deferred type error)"#
      of co_asZ
      { __DEFAULT ->
      letrec {
        h_at5 :: p_asV -> Maybe a_at1
        [LclId]
        h_at5 = \ (x_arY :: p_asV) -> Just @ a_at1 (f_arZ @ a_at1); } in
      h_at5
      }
end Rec }

Without Lint it just squeezes by, because that `case typeError of ..." discards the "..." since it is unreachable