Clippy lints / Restriction
Clippy lint · Restriction · checked with Clippy 0.1.99
clippy::impl_trait_in_params: Lints when impl Trait is being used in a function’s parameters
What it meansLints when impl Trait is being used in a function’s parameters. It is in the restriction group and off by default.
Does it matter?
Turbofish syntax (::<>) cannot be used to specify the type of an impl Trait parameter, making impl Trait less powerful. Readability may also be a factor.
Lints that forbid language features for specific codebases (no unwrap, no indexing...). Off by default; pick them one by one, never the whole group.
How to fix it
Clippy does not fix this one automatically (its suggestion may change behaviour, so it only shows it). Change the code by hand:
Flagged
trait MyTrait {}
fn foo(a: impl MyTrait) {
// [...]
}
Write this instead
trait MyTrait {}
fn foo<T: MyTrait>(a: T) {
// [...]
}
Turn it off, or on
It is off by default. To use it, set it to warn or deny:
Whole crate (Cargo.toml)
[lints.clippy]
impl_trait_in_params = "warn"In code
#![warn(clippy::impl_trait_in_params)]One run
cargo clippy -- -W clippy::impl-trait-in-paramsThe [lints] table needs Rust 1.74 or newer. In a workspace, put it under [workspace.lints.clippy] and add [lints] workspace = true to each member.
Clippy's own documentation
What it does
Lints when impl Trait is being used in a function’s parameters.
Why restrict this?
Turbofish syntax (::<>) cannot be used to specify the type of an impl Trait parameter,
making impl Trait less powerful. Readability may also be a factor.
Example
trait MyTrait {}
fn foo(a: impl MyTrait) {
// [...]
}
Use instead:
trait MyTrait {}
fn foo<T: MyTrait>(a: T) {
// [...]
}
From the Clippy lint list (0.1.99), part of the Rust project, MIT or Apache-2.0. Official entry.
Related lints
- unwrap_usedChecks for .unwrap() or .unwrap_err() calls on Results and .unwrap() call on Options
- module_name_repetitionsDetects public item names that are prefixed or suffixed by the containing public module’s name
- expect_usedChecks for .expect() or .expect_err() calls on Results and .expect() call on Options
- get_unwrapcalled `.get().unwrap()` on a Vec
- host_endian_bytesuse of `to_ne_bytes`
- if_then_some_else_noneChecks for if-else that could be written using either bool::then or bool::then_some
- implicit_returnmissing `return` statement
- indexing_slicingindexing may panic
- infinite_loopinfinite loop detected
All 847 Clippy lints · Rust compiler errors · Cargo.toml checker
Up next
Related lintclippy::unwrap_usedChecks for .unwrap() or .unwrap_err() calls on Results and .unwrap() call on OptionsRead it next →Did this answer your question?