Support piecewise function definition

[Ailrun]

Current retrie picks the first piece of a piecewise function definition when trying to unfold the funciton. For example, with this code

module Test where

piece :: Bool -> Int
piece True = 1
piece False = 0

usePiece :: Bool -> Int
usePiece b = piece b

if I execute retrie -u "Test.piece" --target-file Test.hs, it returns

module Test where

piece :: Bool -> Int
piece True = 1
piece False = 0

usePiece :: Bool -> Int
usePiece b = (\ True -> 1) b

which is not semantically same.

[xich]

So we used to have something to handle this. From the single definition, it would generate three rewrites:

  piece True = 1

  piece False = 0

  forall x. piece x = case x of
    True -> 1
    False -> 0

I removed it at some point because the function-to-case conversion was buggy and lead to some strange stuff. Things are more mature now, so I could try adding it back.

Does that seem like the behavior you would expect?

[Ailrun]

Yes, handling the example using case sounds reasonable for me.