Document and fix code style

src/LambdaLifter.hs

@@ -15,6 +15,10 @@ import           TypeCheckerIr
 
 
 -- | Lift lambdas and let expression into supercombinators.
+-- Three phases:
+-- @freeVars@ annotatss all the free variables.
+-- @abstract@ converts lambdas into let expressions.
+-- @collectScs@ moves every non-constant let expression to a top-level function.
 lambdaLift :: Program -> Program
 lambdaLift = collectScs . abstract . freeVars
 
@@ -27,7 +31,6 @@ freeVars (Program ds) = [ (n, xs, freeVarsExp (Set.fromList xs) e)
 
 freeVarsExp :: Set Id -> Exp -> AnnExp
 freeVarsExp localVars = \case
-
     EId  n  | Set.member n localVars -> (Set.singleton n, AId n)
             | otherwise              -> (mempty, AId n)