Closed
Description
openedon Nov 14, 2021
I tried this code:
use std::mem;
pub fn minimum_total(triangle: Vec<Vec<i32>>) -> i32 {
let mut temp_cache = Vec::with_capacity(triangle.len());
let mut cache = Vec::with_capacity(triangle.len());
for row in triangle {
temp_cache.resize(row.len(), 0);
for (i, (target, source)) in temp_cache.iter_mut().zip(row).enumerate() {
*target = match (cache.get(i.wrapping_sub(1)), cache.get(i)) {
(None, None) => source,
(None, Some(val)) | (Some(val), None) => source + val,
(Some(left), Some(right)) => source + left.min(right),
};
}
mem::swap(&mut cache, &mut temp_cache);
}
cache.into_iter().min().unwrap()
}I expected to see this happen: The code compiles successfully.
Instead, this happened: The code failed to compile:
--> src/lib.rs:11:36
|
5 | let mut cache = Vec::with_capacity(triangle.len());
| --------- consider giving `cache` the explicit type `Vec<T>`, where the type parameter `T` is specified
...
11 | *target = match (cache.get(i.wrapping_sub(1)), cache.get(i)) {
| ^^^ cannot infer type for type parameter `T`
|
= note: type must be known at this point
For more information about this error, try `rustc --explain E0282`.
error: could not compile `playground` due to previous error
Playground link: https://play.rust-lang.org/?version=nightly&mode=debug&edition=2021&gist=446e975abb9c2a303485f483494a6512.
The code works fine with stable toolchain.
Meta
Rustc version: 1.58.0-nightly (2021-11-13 b416e38)
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