`Cannot read property 'length' of undefined` when concatenating largeish arrays

[pseudonom]

I've defined concat as

concat = A.foldl (\x acc -> log "step" <| x `A.append` acc) A.empty

Using this,

concat << A.repeat 4 <| A.repeat 4 ()

produces

step: Array.fromList [(),(),(),()]
step: Array.fromList [(),(),(),(),(),(),(),()]
step: Array.fromList [(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),()]
step: Array.fromList [(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),()]
Array.fromList [(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),()]
 : Array.Array ()

as expected.

concat << A.repeat 4 <| A.repeat 5 ()

produces

step: Array.fromList [(),(),(),(),()]
step: Array.fromList [(),(),(),(),(),(),(),(),(),()]
step: Array.fromList [(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),(),()]
TypeError: Cannot read property 'length' of undefined

The line producing the error is https://github.com/elm-lang/core/blob/master/src/Native/Array.js#L477

[pseudonom]

Fixed by https://github.com/elm-lang/core/blob/master/src/Native/Array.js#L393 in 0.14.

[pseudonom]

Fixed by https://github.com/elm-lang/core/blob/master/src/Native/Array.js#L393 in 0.14.