clippy::wildcard_imports: Checks for wildcard imports use _::*

use crate1::foo; // Imports a function named foo
use crate2::*; // Has a function named foo

foo(); // Calls crate1::foo

use crate1::*;

foo();

[lints.clippy]
wildcard_imports = "warn"

#![warn(clippy::wildcard_imports)]

cargo clippy -- -W clippy::wildcard-imports

Clippy's own documentation

What it does

Checks for wildcard imports use _::*.

Why is this bad?

wildcard imports can pollute the namespace. This is especially bad if you try to import something through a wildcard, that already has been imported by name from a different source:

use crate1::foo; // Imports a function named foo
use crate2::*; // Has a function named foo

foo(); // Calls crate1::foo

This can lead to confusing error messages at best and to unexpected behavior at worst.

Exceptions

Wildcard imports are allowed from modules that their name contains prelude. Many crates (including the standard library) provide modules named “prelude” specifically designed for wildcard import.

Wildcard imports reexported through pub use are also allowed.

use super::* is allowed in test modules. This is defined as any module with “test” in the name.

These exceptions can be disabled using the warn-on-all-wildcard-imports configuration flag.

Known problems

If macros are imported through the wildcard, this macro is not included by the suggestion and has to be added by hand.

Applying the suggestion when explicit imports of the things imported with a glob import exist, may result in unused_imports warnings.

Example

use crate1::*;

foo();

Use instead:

use crate1::foo;

foo();

Configuration

• allowed-wildcard-imports: List of path segments allowed to have wildcard imports.

Example

allowed-wildcard-imports = [ "utils", "common" ]

Noteworthy

1. This configuration has no effects if used with warn_on_all_wildcard_imports = true.
2. Paths with any segment that containing the word ‘prelude’ are already allowed by default.

(default: [])

• warn-on-all-wildcard-imports: Whether to emit warnings on all wildcard imports, including those from prelude, from super in tests, or for pub use reexports.

  (default: false)

From the Clippy lint list (0.1.99), part of the Rust project, MIT or Apache-2.0. Official entry.

Related lints

• too_many_linesChecks for functions with a large amount of lines
• missing_errors_docChecks the doc comments of publicly visible functions that return a Result type and warns if there is no # Errors section
• must_use_candidateChecks for public functions that have no #[must_use] attribute, but return something not already marked must-use, have no mutable arg and mutate no statics
• used_underscore_bindingused underscore-prefixed binding
• used_underscore_itemsused underscore-prefixed item
• verbose_bit_maskChecks for bit masks that can be replaced by a call to trailing_zeros
• with_capacity_zerocalling `with_capacity(0)` is equivalent to `new()`
• zero_sized_map_valuesChecks for maps with zero-sized value types anywhere in the code

All 847 Clippy lints · Rust compiler errors · Cargo.toml checker