Error message blames wrong line

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1

Actual error is in the line before the last one: let x4: Vec<f64> = x3.collect(); but compiler blames the last one, where it makes no sense, because I have specified explicitly type of x4. Is this a bug in type resolver?

fn main() {
    let v = vec![1_f64, 2.2_f64];
    let mut fft: Vec<Vec<f64>> = vec![];

    let x1: &[f64] = &v;
    let x2 = x1.into_iter();
    let x3 = x2.rev();
    let x4: Vec<f64> = x3.collect();    // <-- mistake is here
    fft.push(x4);                                  // <-- but error blames this line
}

 --> src/main.rs:9:14
  |
9 |     fft.push(x4);
  |              ^^ a collection of type `std::vec::Vec<f64>` cannot be built from `std::iter::Iterator<Item=&f64>`

And while we are on this, what is idiomatic way to copy slice in reverse order into vector?

2

This definitely looks like an error reporting bug to me. I've tried to find an existing issue documenting it, but I don't think there are any (or at least, none with this exact error). Could you possibly report this as a bug to https://github.com/rust-lang/rust/issues/?

As for copying a reverse slice, your way seems pretty good. I'd probably reach for [T]::to_vec and Vec::reverse, but both methods seem pretty obvious and without benchmarks it's hard to say if one would be any faster.

3

Done: Error message blames wrong line · Issue #66923 · rust-lang/rust · GitHub

4

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