解决 Rust 中的导入问题

Question

我在从 crates.io 导入 rand 箱时遇到问题。添加行 rand="0.8.3" 然后为项目运行命令 cargo build 后，它不断显示相同的错误：

error[E0432]: unresolved import `rand`
 --> main.rs:1:5
  |
1 | use rand::Rng;
  |     ^^^^ maybe a missing crate `rand`?

error[E0433]: failed to resolve: use of undeclared crate or module `rand`
 --> main.rs:4:25
  |
4 |     let secret_number = rand::thread_rng().gen_range(1..=11);
  |                         ^^^^ use of undeclared crate or module `rand`

error: aborting due to 2 previous errors

cargo.toml 文件

[package]
name = "roller"
version = "0.1.0"
authors = ["User"]
edition = "2018"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]
rand = "0.8.3"

基本上最简单的可重现示例就是这行代码：

 use rand::Rng;

 fn main(){
    let secret_number = rand::thread_rng().gen_range(1..=11);
    print!("{}",secret_number);
 }

有什么问题吗？

万一：
**cargo.lock**文件：

# This file is automatically @generated by Cargo.
# It is not intended for manual editing.
[[package]]
name = "cfg-if"
version = "1.0.0"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"

[[package]]
name = "getrandom"
version = "0.2.2"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "c9495705279e7140bf035dde1f6e750c162df8b625267cd52cc44e0b156732c8"
dependencies = [
 "cfg-if",
 "libc",
 "wasi",
]

[[package]]
name = "libc"
version = "0.2.86"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "b7282d924be3275cec7f6756ff4121987bc6481325397dde6ba3e7802b1a8b1c"

[[package]]
name = "ppv-lite86"
version = "0.2.10"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "ac74c624d6b2d21f425f752262f42188365d7b8ff1aff74c82e45136510a4857"

[[package]]
name = "rand"
version = "0.8.3"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "0ef9e7e66b4468674bfcb0c81af8b7fa0bb154fa9f28eb840da5c447baeb8d7e"
dependencies = [
 "libc",
 "rand_chacha",
 "rand_core",
 "rand_hc",
]

[[package]]
name = "rand_chacha"
version = "0.3.0"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "e12735cf05c9e10bf21534da50a147b924d555dc7a547c42e6bb2d5b6017ae0d"
dependencies = [
 "ppv-lite86",
 "rand_core",
]

[[package]]
name = "rand_core"
version = "0.6.2"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "34cf66eb183df1c5876e2dcf6b13d57340741e8dc255b48e40a26de954d06ae7"
dependencies = [
 "getrandom",
]

[[package]]
name = "rand_hc"
version = "0.3.0"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "3190ef7066a446f2e7f42e239d161e905420ccab01eb967c9eb27d21b2322a73"
dependencies = [
 "rand_core",
]

[[package]]
name = "roller"
version = "0.1.0"
dependencies = [
 "rand",
]

[[package]]
name = "wasi"
version = "0.10.2+wasi-snapshot-preview1"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "fd6fbd9a79829dd1ad0cc20627bf1ed606756a7f77edff7b66b7064f9cb327c6"

Answer 1

在文件 Cargo.toml 中添加行：

[dependencies]
rand="0.3.14"

并重建项目！

它适用于这些版本：

• rustc 1.53.0

• 货物1.53.0

从这里获取答案https://github.com/rust-lang/rust/issues/34616

Answer 2

当我使用 vs code(rust-analyzer) 运行它时遇到同样的错误。

当您按下运行按钮时

rustic main.rs

这个命令在终端中调用，会导致错误。

在终端中输入此内容，

cargo build
cargo run

效果很好

Answer 3

我是生锈新手。我在阅读 Rust Lang 书籍教程时遇到了同样的问题。我已将行

rand = "0.8.5"

添加到

cargo.toml

文件中，但我无法理解为什么它仍然无法编译。

问题是我在顶部添加了这一行。它需要位于依赖项部分：

[dependencies]
rand = "0.8.5"

Answer 4

如果您认为自己做的一切都是正确的，但却遇到了这样的奇怪的无法导入错误，那么您可以尝试

cargo clean

。

这将允许您在此之后完全重新构建您的二进制文件/库。