Main.hs

{-# LANGUAGE OverloadedLists #-}
{-# LANGUAGE OverloadedStrings #-}

import Data.Map
import Data.Text

main :: IO ()
main = do
    let m = [("foo", 1), ("bar", 2)]
          :: Map Text Int
    putStrLn "My map looks like this:"
    print m

out.txt

root@b575c8a9c84b:~/overloaded_lists# cabal build
Building overloaded-lists-0.1.0.0...
Preprocessing executable 'overloaded-lists' for overloaded-lists-0.1.0.0...
[1 of 1] Compiling Main             ( src/Main.hs, dist/build/overloaded-lists/overloaded-lists-tmp/Main.o )

src/Main.hs:9:13:
    Couldn't match type `GHC.Exts.Item (Map Text Int)' with `(t0, t1)'
    The type variables `t0', `t1' are ambiguous
    Expected type: Int -> [(t0, t1)] -> Map Text Int
      Actual type: Int
                   -> [GHC.Exts.Item (Map Text Int)] -> Map Text Int
    In the expression: [("foo", 1), ("bar", 2)] :: Map Text Int
    In an equation for `m':
        m = [("foo", 1), ("bar", 2)] :: Map Text Int
    In the expression:
      do { let m = ...;
           putStrLn "My map looks like this:";
           print m }