Convert a List of objects into a Dict (≈ Map) using an object's property as key, in a type safe way with ELM

propMap.elm

import Dict

-- The transformation function
listToDict : (a -> comparable) -> [a] -> Dict.Dict comparable a
listToDict getKey values = Dict.fromList (map (\v -> (getKey v, v)) values)
 
-- Demo type
type FooBar =
  { foo : String
  , bar : Int
  }
 
-- Demo data
fooBars : [FooBar]
fooBars = 
  [ { foo = "tata", bar =  1 }
  , { foo = "tete", bar =  2 }
  , FooBar "titi" 3
  , FooBar "toto" 4
  ]
 
-- Transform demo List to a Dict, using the `foo` property (String)
dict : Dict.Dict String FooBar
dict = listToDict .foo fooBars -- .foo is safe here
 
-- Transform demo List to a Dict, using the `bar` property (Int)
dict2 : Dict.Dict Int FooBar -- So is Int here !
dict2 = listToDict .bar fooBars

-- Won't compile:
-- err : Dict.Dict Boolean FooBar
-- err = listToDict .bar fooBars

-- err : Dict.Dict String FooBar
-- err = listToDict .bazzzzzzz fooBars
 
-- Render result
main = flow down [ (asText dict), (asText dict2) ]

An answer to : https://gist.github.com/srenault/3a8b08b73abb5bc520d3

Hey Warry, we're looking to use this snippet for something at work, and while it's a boring question, I have to ask—what code is this snippet license under?