Idris：由于“ rewrite__impl”而导致类型检查失败

Question

我是Idris的初学者，我正在尝试编写一个使用Vect n Type并返回{a : Vect n Type} -> type_1 -> ... -> type_n -> HVect (reverse a)的函数。我已经将其类型检查下来，直到最后的递归步骤，在该步骤中，由于rewrite__impl函数卡在类型中而使它失败。到目前为止，这是代码：

total funcGenerator : (Vect n Type) -> Type -> Type
funcGenerator []      out = out
funcGenerator (x::xs) out = x -> funcGenerator xs out

-- Reverse first argument, append second argument to it
total pileOn : Vect n Type -> Vect k Type -> Vect (plus n k) Type
pileOn               []      y = y
pileOn {n=S len} {k} (x::xs) y = rewrite plusSuccRightSucc len k in
                                     pileOn xs (x::y)

fetchArgsReverse : {h : Vect m Type} -> (b : Vect n Type) -> 
                   HVect h -> funcGenerator (HVect (pileOn b h))
fetchArgsReverse               [x]     y = (\p => p::y)
fetchArgsReverse {n=S len} {m} (x::xs) y = (\p => fetchArgsReverse xs (p::y))

类型检查器抱怨如下：

|
| fetchArgsReverse {n=S len} {m} (x::xs) y = (\p => fetchArgsReverse xs (p::y))
|                                            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
When checking right hand side of fetchArgsReverse with expected type
    funcGenerator (x::xs) (HVect (pileOn (x::xs) h))

Type mismatch between
    funcGenerator xs (HVect (pileOn xs (x::h)))
        (Type of fetchArgsReverse xs (p::y))
and
    funcGenerator xs 
        (HVect (rewrite__impl (\replaced => Vect replaced Type)
        (plusSuccRightSucc len m) (pileOn xs (x::h)))) 
        (Expected Type)

（我增加了一些间距。）

该rewrite__impl以预期的类型如何处理？我该如何解决这个问题？如果没有重写，pileOn函数将无法正常工作。