z4.hs:11:28: error: Not in scope: type variable ‘a’
   |
11 |   case eqTypeRep (typeRep @a) (typeRep @b) of
   |                            ^

z4.hs:11:41: error: Not in scope: type variable ‘b’
   |
11 |   case eqTypeRep (typeRep @a) (typeRep @b) of
   |