为什么 rustc 说变量 "totalSplitInv" 超出范围？

Question

我运行下面的程序经过 rustc:

#![feature(slicing_syntax)]
fn sortAndCountInv(arr: &mut [i64]) -> i64 {
    return sortAndCountInv_(arr, 0, arr.length - 1)
}

fn sortAndCountInv_(arr: &mut [i64], start: i64, finish: i64) {
    let lengthOfSubarray = finish - start + 1;
    if (lengthOfSubarray == 0) || (lengthOfSubarray == 1) {
        return totalSplitInv
    }
    else {
        let half = (start + finish) / 2;
        let leftInv = sortAndCountInv_(arr, start, half);
        let rightInv = sortAndCountInv_(arr, half + 1, finish);
        let splitInv = mergeAndCountSplitInv(arr, start, finish, half);
        return leftInv + rightInv + splitInv
    }
}
fn mergeAndCountSplitInv(arr: &mut [i64], start: i64, finish: i64, half: i64) -> i64 {
    let aux = arr[start..finish + 1];
    let divider = half - start;
    let mut i = 0;
    let mut j = divider + 1;
    let mut totalSplitInv = 0;
    let lastIndex = aux.length - 1;
    for k in range(start, finish + 1) {
        if i > divider {
            arr[k] = aux[j];
            j += 1
        } else if j > lastIndex {
            arr[k] = aux[i];
            i += 1
        } else if aux[i] < aux[j] {
            arr[k] = aux[i];
            i += 1
        } else {
            arr[k] = aux[j];
            j += 1;
            totalSplitInv += (divider - i) + 1; 
        }
    }
    return totalSplitInv
}

当我尝试使用 rustc v-0.12.0-dev 编译它时，出现以下范围错误：

inversions.rs:9:16: 9:29 error: unresolved name `totalSplitInv`.
inversions.rs:9         return totalSplitInv

也就是说，在函数mergeAndCountSplitInv中，return totalSplitInv行是无效的，因为totalSplitInv超出了范围？为什么会这样？

Answer 1

我认为错误指向 sortAndCountInv_ 中的 return totalSplitInv，而不是 mergeAndCountSplitInv。

fn sortAndCountInv_(arr: &mut [i64], start: i64, finish: i64) {
    let lengthOfSubarray = finish - start + 1;
    if (lengthOfSubarray == 0) || (lengthOfSubarray == 1) {
        return totalSplitInv // here
...

为什么 rustc 说变量 "totalSplitInv" 超出范围？

Why does rustc say that the variable "totalSplitInv" is out of scope?

scope

rust