Internal compiler error

[FluxusMagna]

This is the most reduced code that reproduces the error that I've come up with.

def fun [k] (n:i64)
    (op:[k]f32 -> [k]f32) (_:[k]f32)
    =
    let process (Q:*[n+1][k]f32) i =
        let q = op Q[i]
        let q = map (+1) q
        in Q with [i+1] = q
    let (i, Q) =
        loop (i, Q) =
            ( 0, replicate (n+1) (replicate k 0))
        while i < n do
            let Q = process Q i
            in (i, Q)
    in i

entry test n k = fun n (map (+1)) (replicate k 0)

The error I get is

Internal compiler error (unhandled IO exception).
Please report this at https://github.com/diku-dk/futhark/issues
defuncApplyArg: cannot apply StaticVal
Dynamic (Scalar (Prim (Signed Int64)))
Function name: defunc_0_+
CallStack (from HasCallStack):
  error, called at src/Futhark/Internalise/Defunctionalise.hs:979:3 in futhark-0.26.0-HXLlDtoyvtTB3lobWyH4uu:Futhark.Internalise.Defunctionalise

The code (or rather what was reduced to this code) works fine in the interpreter.

[athas]

Slightly smaller:

def fun [k] (n:i64) (op:[k]f32 -> *[k]f32) (_:[k]f32) =
  let process (Q:*[n+1][k]f32) i =
    let q = op Q[i]
    in Q with [i+1] = q
  let Q = replicate (n+1) (replicate k 0)
  let Q = process Q 0
  in Q

entry test n k = fun n copy (replicate k 0)

Strange failure. This program does not do anything odd.

[athas]

Defunctionalisation was naive and shadowed the + intrinsic.