无法为要求 `rand = "^0.9.0"`选择版本

Question

我每次运行时都会收到此错误

cargo build

：

error: failed to select a version for the requirement `rand = "^0.9.0"`
candidate versions found which didn't match: 0.8.5, 0.8.4, 0.8.3, ...
location searched: crates.io index
required by package `guessing_game v0.1.0 (D:\Adwait\Rust\project\guessing_game)`

Cargo.toml

看起来像这样：

[package]
name = "guessing_game"
version = "0.1.0"
edition = "2021"

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

[dependencies]
rand = "0.9.0"

Answer 1

此错误是因为没有可用的版本

0.9.0

而导致的。将其更新为

0.8.0

。 Cargo.toml 应该看起来像这样。

[package]
name = "guessing_game"
version = "0.1.0"
edition = "2021"

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

[dependencies]
rand = "0.8.0"

Answer 2

我自己也经历过这一点，我相信这种困惑源于Rust 教程提到 0.9.0 作为示例来了解升级 Rust 板条箱。

我不确定他们为什么选择这个例子，因为它不存在。如果您是 Rust 新手并且想要尝试升级 Rust crate，那么将 0.7.x 升级到 0.8.0 是一个更好的主意。

Answer 3

出现此类错误的另一个可能原因是您的编译器已过时，并且新版本的库针对新编译器。使用

rustup update

更新您的工具链。

我有一个使用 clap 4.2 的项目，但它拒绝在另一台计算机上编译，并出现这样的错误。

Answer 4

我只是学习 Rust 的初学者，但从我所见，如果你使用

cargo search rand

你会得到这个输出：

username@PC:~/Projects/guessing_game$ cargo search rand
rand = "0.9.0-beta.1"        # Random number generators and other randomness functionality. 
bevy_rand = "0.8.0"          # A plugin to integrate rand for ECS optimised RNG for the Bevy game engine.
tinyrand = "0.5.0"           # Lightweight RNG specification and several ultrafast implementations in Rust.
rand-construct = "0.10.0"    # Encapsulates the random-constructible and random-constructible-derive crates which are used for cr…
random_derive = "0.0.0"      # Procedurally defined macro for automatically deriving rand::Rand for structs and enums
tera-rand = "0.2.0"          # A suite of random data generation functions for the Tera template engine
tera-rand-cli = "0.2.0"      # A CLI tool for generating a feed of random data from a Tera template
rands = "0.8.8"              # Random number generators and other randomness functionality. 
faker_rand = "0.1.1"         # Fake data generators for lorem ipsum, names, emails, and more
rand_derive2 = "0.1.21"      # Generate customizable random types with the rand crate
... and 1581 crates more (use --limit N to see more)
note: to learn more about a package, run `cargo info <name>`

如您所见，“0.9.0”是测试版本，这就是它给您错误的原因。如果你还想使用它，可以在 Cargo.toml 文件中写入

rand = { version = "0.9.0-beta.1" }

。

如果您只想要 rand 的最新稳定版本（或任何其他依赖项，从我到目前为止所看到的来看），您可以使用

cargo add rand

它将自动将“0.8.5”版本添加到 Cargo.toml文件。