3

I'm having trouble with importing rand crate from crates.io. After adding the line rand="0.8.3" and then running command cargo build for the project, it keeps displaying the same errors:

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

the cargo.toml file

[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"

Basically the simplest reproducible example is this single line of code:

 use rand::Rng;

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

What's wrong with it?


Just in case:
The **cargo.lock**file: 
# 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"
Nantarand
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  • Can you provide a [minimal, reproducible example](https://stackoverflow.com/help/minimal-reproducible-example)? The next thing is that for `rand 0.8.3` the function signature for `.gen_range` has changed. It now takes a range, e.g. `.gen_range(0..=42)`. – Jason Feb 25 '21 at 11:09
  • @Nantarand: there is a line of code, yes. But it's too minimal. So minimal that it's not reproducible. One needs to wrap it in `fn main` and add that import on top, I think. – Sergio Tulentsev Feb 25 '21 at 11:49
  • Thank you for pointing the signature change out though I didn't reflect it in the code – Nantarand Feb 25 '21 at 11:49
  • @SergioTulentsev oh I thought that the existence the main function was implicit in this case but I'm adding it – Nantarand Feb 25 '21 at 11:53
  • With the examples you provided I cannot reproduce these warnings in Rust 1.50.0. What compiler version are you using? – Johann150 Feb 25 '21 at 12:10
  • @Johann150 I'm using the same version – Nantarand Feb 25 '21 at 12:19
  • Also why's this peculiarity that the linter will show possible choices when I type 't' after "rand::" but won't show the same after typing 'g' after "thread_rng()." – Nantarand Feb 25 '21 at 12:22
  • You seem to be doing everything right. This is all you need to use a package. I suggest deleting your binary and doing a new `cargo new`. – Hadus Feb 25 '21 at 12:23
  • You might also try to restart whatever editor you are using or even your computer.. – Hadus Feb 25 '21 at 12:26
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    @Nantarand: well yes, it is normally kind of assumed, but given you seem to have problems with importing a package, it's better to post your main.rs in full. For all we know, you _are_ trying to compile that file with only this line in it. That's an extra clarification from us and waste of time all around. – Sergio Tulentsev Feb 25 '21 at 12:30
  • I'll post the full files in the question's body guys! It seems such a trivial error and a minor inconvenience that's simply wasting time as Sergio said. I'm prob gonna try it with another editor and if not, well, guess won't engage into any randomness-needing project with Rust – Nantarand Feb 25 '21 at 12:33
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    Which version of the Rust compiler are you using? `rustc --version` or `cargo --version`. Implicit crate imports (as part of the 2018 edition) are only available since 1.31.0. – E_net4 Feb 25 '21 at 14:26
  • Update: It works on IntelliJ's Rust Plugin – Nantarand Mar 01 '21 at 07:59

3 Answers3

5

In file Cargo.toml add lines:

[dependencies]
rand="0.3.14"

And rebuild project!

It worked with these versions:

  • rustc 1.53.0

  • cargo 1.53.0

Took answer from here https://github.com/rust-lang/rust/issues/34616

rlandster
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Kity Sypo
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1

got the same error when I run it with vs code(rust-analyzer).

When you press the run button rustic main.rs this command is called in terminal, it will cause error.

Type this in terminal,

cargo build
cargo run

It works well

Shuang Zhou
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-1

If you think that you did everything right and get a strange unable to import error like this then you could try cargo clean.

That will allow you to fully re-build your binary/library after that.

Hadus
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