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Why doesn't `use std:: self, … ;` compile?
How do I see the expanded macro code that's causing my compile error?Why doesn't println! work in Rust unit tests?Why doesn't this compile - use of undeclared type name `thread::scoped`Cannot compile code that uses std::io - There is no `File` in `std::io`Why do try!() and ? not compile when used in a function that doesn't return Option or Result?Why does Drop take &mut self instead of self?What's the difference between self and Self?Why is the `std` module undeclared?Why doesn't `Box::into_raw` take `self` as parameter?Why doesn't the Godbolt compiler explorer show any output for my function when compiled in release mode?Why does a plain match expression compile, while a map_err call doesn't?
.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty height:90px;width:728px;box-sizing:border-box;
I have no idea why this code can't be compiled with Rust 1.27.0.
This is test.rs as it is on my hard drive:
use std::
self,
io::prelude::*,
net:: TcpListener, TcpStream ,
;
fn main()
Output when trying to compile it with rustc test.rs:
error[E0254]: the name `std` is defined multiple times
--> test.rs:2:5
|
2 | self,
| ^^^^ `std` reimported here
|
= note: `std` must be defined only once in the type namespace of this module
help: you can use `as` to change the binding name of the import
|
2 | self as other_std,
| ^^^^^^^^^^^^^^^^^
warning: unused imports: `TcpListener`, `TcpStream`, `io::prelude::*`, `self`
--> test.rs:2:5
|
2 | self,
| ^^^^
3 | io::prelude::*,
| ^^^^^^^^^^^^^^
4 | net::TcpListener, TcpStream,
| ^^^^^^^^^^^ ^^^^^^^^^
|
= note: #[warn(unused_imports)] on by default
rust
edited Mar 24 at 12:33
Shepmaster
165k16345494
asked Mar 23 at 9:04
AnonymousAnonymous
85
add a comment |
I have no idea why this code can't be compiled with Rust 1.27.0.
This is test.rs as it is on my hard drive:
use std::
self,
io::prelude::*,
net:: TcpListener, TcpStream ,
;
fn main()
Output when trying to compile it with rustc test.rs:
error[E0254]: the name `std` is defined multiple times
--> test.rs:2:5
|
2 | self,
| ^^^^ `std` reimported here
|
= note: `std` must be defined only once in the type namespace of this module
help: you can use `as` to change the binding name of the import
|
2 | self as other_std,
| ^^^^^^^^^^^^^^^^^
warning: unused imports: `TcpListener`, `TcpStream`, `io::prelude::*`, `self`
--> test.rs:2:5
|
2 | self,
| ^^^^
3 | io::prelude::*,
| ^^^^^^^^^^^^^^
4 | net::TcpListener, TcpStream,
| ^^^^^^^^^^^ ^^^^^^^^^
|
= note: #[warn(unused_imports)] on by default
rust
edited Mar 24 at 12:33
Shepmaster
165k16345494
asked Mar 23 at 9:04
AnonymousAnonymous
85
Wild guess: std::self references std itself, so you import std twice with a single use statement. Is there a specific reason why you want to import std::self?
– Frank Schmitt
Mar 23 at 9:41
This works fine in a Rust 2018 project, not in a 2015. Please upgrade.
– Shepmaster
Mar 24 at 11:57
add a comment |
I have no idea why this code can't be compiled with Rust 1.27.0.
This is test.rs as it is on my hard drive:
use std::
self,
io::prelude::*,
net:: TcpListener, TcpStream ,
;
fn main()
Output when trying to compile it with rustc test.rs:
error[E0254]: the name `std` is defined multiple times
--> test.rs:2:5
|
2 | self,
| ^^^^ `std` reimported here
|
= note: `std` must be defined only once in the type namespace of this module
help: you can use `as` to change the binding name of the import
|
2 | self as other_std,
| ^^^^^^^^^^^^^^^^^
warning: unused imports: `TcpListener`, `TcpStream`, `io::prelude::*`, `self`
--> test.rs:2:5
|
2 | self,
| ^^^^
3 | io::prelude::*,
| ^^^^^^^^^^^^^^
4 | net::TcpListener, TcpStream,
| ^^^^^^^^^^^ ^^^^^^^^^
|
= note: #[warn(unused_imports)] on by default
rust
edited Mar 24 at 12:33
Shepmaster
165k16345494
asked Mar 23 at 9:04
AnonymousAnonymous
85
I have no idea why this code can't be compiled with Rust 1.27.0.
This is test.rs as it is on my hard drive:
use std::
self,
io::prelude::*,
net:: TcpListener, TcpStream ,
;
fn main()
Output when trying to compile it with rustc test.rs:
error[E0254]: the name `std` is defined multiple times
--> test.rs:2:5
|
2 | self,
| ^^^^ `std` reimported here
|
= note: `std` must be defined only once in the type namespace of this module
help: you can use `as` to change the binding name of the import
|
2 | self as other_std,
| ^^^^^^^^^^^^^^^^^
warning: unused imports: `TcpListener`, `TcpStream`, `io::prelude::*`, `self`
--> test.rs:2:5
|
2 | self,
| ^^^^
3 | io::prelude::*,
| ^^^^^^^^^^^^^^
4 | net::TcpListener, TcpStream,
| ^^^^^^^^^^^ ^^^^^^^^^
|
= note: #[warn(unused_imports)] on by default
rust
rust
edited Mar 24 at 12:33
Shepmaster
165k16345494
asked Mar 23 at 9:04
AnonymousAnonymous
85
edited Mar 24 at 12:33
Shepmaster
165k16345494
asked Mar 23 at 9:04
AnonymousAnonymous
85
edited Mar 24 at 12:33
Shepmaster
165k16345494
edited Mar 24 at 12:33
Shepmaster
165k16345494
edited Mar 24 at 12:33
Shepmaster
165k16345494
165k16345494
asked Mar 23 at 9:04
AnonymousAnonymous
85
asked Mar 23 at 9:04
AnonymousAnonymous
85
asked Mar 23 at 9:04
AnonymousAnonymous
85
85
Wild guess: std::self references std itself, so you import std twice with a single use statement. Is there a specific reason why you want to import std::self?
– Frank Schmitt
Mar 23 at 9:41
This works fine in a Rust 2018 project, not in a 2015. Please upgrade.
– Shepmaster
Mar 24 at 11:57
add a comment |
Wild guess: std::self references std itself, so you import std twice with a single use statement. Is there a specific reason why you want to import std::self?
– Frank Schmitt
Mar 23 at 9:41
This works fine in a Rust 2018 project, not in a 2015. Please upgrade.
– Shepmaster
Mar 24 at 11:57
Wild guess: std::self references std itself, so you import std twice with a single use statement. Is there a specific reason why you want to import std::self?
– Frank Schmitt
Mar 23 at 9:41
Wild guess: std::self references std itself, so you import std twice with a single use statement. Is there a specific reason why you want to import std::self?
– Frank Schmitt
Mar 23 at 9:41
This works fine in a Rust 2018 project, not in a 2015. Please upgrade.
– Shepmaster
Mar 24 at 11:57
This works fine in a Rust 2018 project, not in a 2015. Please upgrade.
– Shepmaster
Mar 24 at 11:57
add a comment |
1 Answer
1
active
oldest
votes
This works fine in Rust 2018. You probably just want to update by adding edition = "2018" to your Cargo.toml or --edition=2018 to your rustc invocation. Below is the answer for why this doesn't work in Rust 2015.
From the std::prelude documentation:
On a technical level, Rust inserts
extern crate std;
into the crate root of every crate, and
use std::prelude::v1::*;
into every module.
You can also see that in action when looking at your code after macro expansion (e.g. via cargo-expand). For your code this results in:
#![feature(prelude_import)]
#![no_std]
#[prelude_import]
use std::prelude::v1::*;
#[macro_use]
extern crate std;
// No external crates imports or anything else.
use std::
self,
net::TcpListener, TcpStream,
;
fn main()
// Empty.
As you can see, std is already in scope due to the extern crate std; statement. Thus, importing it another time results in this error.
answered Mar 23 at 9:48
Lukas KalbertodtLukas Kalbertodt
27.9k361127
add a comment |
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1 Answer
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1 Answer
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oldest
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active
oldest
votes
This works fine in Rust 2018. You probably just want to update by adding edition = "2018" to your Cargo.toml or --edition=2018 to your rustc invocation. Below is the answer for why this doesn't work in Rust 2015.
From the std::prelude documentation:
On a technical level, Rust inserts
extern crate std;
into the crate root of every crate, and
use std::prelude::v1::*;
into every module.
You can also see that in action when looking at your code after macro expansion (e.g. via cargo-expand). For your code this results in:
#![feature(prelude_import)]
#![no_std]
#[prelude_import]
use std::prelude::v1::*;
#[macro_use]
extern crate std;
// No external crates imports or anything else.
use std::
self,
net::TcpListener, TcpStream,
;
fn main()
// Empty.
As you can see, std is already in scope due to the extern crate std; statement. Thus, importing it another time results in this error.
answered Mar 23 at 9:48
Lukas KalbertodtLukas Kalbertodt
27.9k361127
add a comment |
This works fine in Rust 2018. You probably just want to update by adding edition = "2018" to your Cargo.toml or --edition=2018 to your rustc invocation. Below is the answer for why this doesn't work in Rust 2015.
From the std::prelude documentation:
On a technical level, Rust inserts
extern crate std;
into the crate root of every crate, and
use std::prelude::v1::*;
into every module.
You can also see that in action when looking at your code after macro expansion (e.g. via cargo-expand). For your code this results in:
#![feature(prelude_import)]
#![no_std]
#[prelude_import]
use std::prelude::v1::*;
#[macro_use]
extern crate std;
// No external crates imports or anything else.
use std::
self,
net::TcpListener, TcpStream,
;
fn main()
// Empty.
As you can see, std is already in scope due to the extern crate std; statement. Thus, importing it another time results in this error.
answered Mar 23 at 9:48
Lukas KalbertodtLukas Kalbertodt
27.9k361127
add a comment |
This works fine in Rust 2018. You probably just want to update by adding edition = "2018" to your Cargo.toml or --edition=2018 to your rustc invocation. Below is the answer for why this doesn't work in Rust 2015.
From the std::prelude documentation:
On a technical level, Rust inserts
extern crate std;
into the crate root of every crate, and
use std::prelude::v1::*;
into every module.
You can also see that in action when looking at your code after macro expansion (e.g. via cargo-expand). For your code this results in:
#![feature(prelude_import)]
#![no_std]
#[prelude_import]
use std::prelude::v1::*;
#[macro_use]
extern crate std;
// No external crates imports or anything else.
use std::
self,
net::TcpListener, TcpStream,
;
fn main()
// Empty.
As you can see, std is already in scope due to the extern crate std; statement. Thus, importing it another time results in this error.
answered Mar 23 at 9:48
Lukas KalbertodtLukas Kalbertodt
27.9k361127
This works fine in Rust 2018. You probably just want to update by adding edition = "2018" to your Cargo.toml or --edition=2018 to your rustc invocation. Below is the answer for why this doesn't work in Rust 2015.
From the std::prelude documentation:
On a technical level, Rust inserts
extern crate std;
into the crate root of every crate, and
use std::prelude::v1::*;
into every module.
You can also see that in action when looking at your code after macro expansion (e.g. via cargo-expand). For your code this results in:
#![feature(prelude_import)]
#![no_std]
#[prelude_import]
use std::prelude::v1::*;
#[macro_use]
extern crate std;
// No external crates imports or anything else.
use std::
self,
net::TcpListener, TcpStream,
;
fn main()
// Empty.
As you can see, std is already in scope due to the extern crate std; statement. Thus, importing it another time results in this error.
answered Mar 23 at 9:48
Lukas KalbertodtLukas Kalbertodt
27.9k361127
edited Mar 24 at 12:04
answered Mar 23 at 9:48
Lukas KalbertodtLukas Kalbertodt
27.9k361127
answered Mar 23 at 9:48
Lukas KalbertodtLukas Kalbertodt
27.9k361127
answered Mar 23 at 9:48
Lukas KalbertodtLukas Kalbertodt
27.9k361127
27.9k361127
add a comment |
add a comment |
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Wild guess: std::self references std itself, so you import std twice with a single use statement. Is there a specific reason why you want to import std::self?
– Frank Schmitt
Mar 23 at 9:41
This works fine in a Rust 2018 project, not in a 2015. Please upgrade.
– Shepmaster
Mar 24 at 11:57