Variable lost when printing leftist heap representation

[jazullo]

Here is a leftist heap implementation in gibbon:

data LHeap = E | H Int LHeap LHeap

rank :: LHeap -> Int
rank x = case x of
  E -> 0
  H y z r -> rank r + 1

merge :: LHeap -> LHeap -> LHeap
merge g h = 
  case g of
    E -> h
    H a l r -> case h of
      E -> g
      H b z0 z1 -> 
        let
          s = merge r h
        in
        if a > b then merge h g
        else if rank s > rank l then H a s l
        else H a l s

add :: Int -> LHeap -> LHeap
add x h = merge h (H x E E)

pop :: LHeap -> (Int, LHeap)
pop z = case z of
  H x l r -> (x, merge l r)
  E -> (-1, E)

gibbon_main = 
  let
    _ = printPacked (add 0 E)
  in ()

When gibbon is invoked this gives the following error:

cabal v2-exec gibbon -- --packed --no-gc --to-exe ../lheap/lheap.hs
gibbon: Var l_44_118_170_238_248 not found. Checking:
: VarE "l_44_118_170_238_248"
CallStack (from HasCallStack):
  error, called at src/Gibbon/L1/Typecheck.hs:746:21 in gibbon-0.2-inplace:Gibbon.L1.Typecheck

To the right of _ = printPacked, replacing (add 0 E) with just E is able to compile and produce the correct representation:

./lheap.exe
(E )'#()

This error was produced in branch issue_191.

[vidsinghal]

This Hack seems to work

data LHeap = E | H Int LHeap LHeap

rank :: LHeap -> Int
rank x = case x of
  E -> 0
  H y z r -> rank r + 1

merge :: LHeap -> LHeap -> LHeap
merge g h = 
  case g of
    E -> h
    H a l r -> case h of
      E -> g
      H b z0 z1 -> 
        let
          s = merge r h
        in mergeIf a b l s h g

mergeIf :: Int -> Int -> LHeap -> LHeap -> LHeap -> LHeap -> LHeap 
mergeIf a b l s h g = if (a > b) then merge h g
                      else if (rank s > rank l) then mergeIfElse a b s l h g
                      else H a l s 

mergeIfElse :: Int -> Int -> LHeap -> LHeap -> LHeap -> LHeap -> LHeap 
mergeIfElse a b s l h g = H a s l

add :: Int -> LHeap -> LHeap
add x h = merge h (H x E E)

pop :: LHeap -> (Int, LHeap)
pop z = case z of
  H x l r -> (x, merge l r)
  E -> (-1, E)

gibbon_main = 
  let
    _ = printPacked (add 0 E)
  in ()

[jazullo]

Here's a simpler example that I believe is broken by the same bug.

data I = I Int
data A = A I I

swap :: A -> A
swap x = case x of
  A i1 i2 -> A i2 i1

gibbon_main = 
  let
    _ = printPacked (swap (A (I 0) (I 1)))
  in ()

gibbon: Var i1_13_57_104_141 not found. Checking: 
: VarE "i1_13_57_104_141"
CallStack (from HasCallStack):
  error, called at src/Gibbon/L1/Typecheck.hs:746:21 in gibbon-0.2-inplace:Gibbon.L1.Typecheck

Note the following works:

data A = A Int Int

swap :: A -> A
swap x = case x of
  A i1 i2 -> A i2 i1

gibbon_main = 
  let
    _ = printPacked (swap (A 0 1))
  in ()