-fdefer-typed-holes will raise "(deferred type error)" exception, and that name looks wrong
with ghc-9.6.1,
:set -fdefer-typed-holes
ghci> x = [True,_] -- gives warning, as expected
ghci> print x
[True,*** Exception: <interactive>:11:11: error: [GHC-88464]
...
(deferred type error)
that last line looks wrong to me, since there is no type error. Documentation says "a hole ... will behave like undefined", and for that I would get no type error.