T3395.hs:6:8: error:
    • Illegal last statement of a list comprehension:
        r1 <- undefined
      (It should be an expression.)
      When splicing a TH expression: [r1 <- undefined | undefined]
    • In the untyped splice:
        $(return
            $ CompE
                [NoBindS (VarE $ mkName "undefined"),
                 BindS (VarP $ mkName "r1") (VarE $ mkName "undefined")])