never executed always true always false

    1 module Main where
    2 
    3 import LI11718
    4 import qualified Tarefa1_2017li1g183 as T1
    5 
    6 import System.Environment
    7 import Text.Read
    8 
    9 main = do
   10     args <- getArgs
   11     case args of
   12         ["constroi"] -> do
   13             str <- getContents
   14             let caminho = readMaybe str
   15             case caminho of
   16                 Nothing -> error "caminho invalido"
   17                 Just c -> print $ T1.constroi c
   18         ["testes"] -> print $ T1.testesT1
   19         otherwise -> error "RunT1 argumentos invalidos"