Clippy lints / Nursery
Clippy lint · Nursery · checked with Clippy 0.1.99
clippy::trait_duplication_in_bounds: this trait bound is already specified in the where clause
What it meansChecks for cases where generics or trait objects are being used and multiple syntax specifications for trait bounds are used simultaneously. It is in the nursery group and off by default.
What you see
warning: this trait bound is already specified in the where clause --> main.rs:3:12 | 3 | fn func<T: Clone + Default>(arg: T) where T: Clone + Default {} | ^^^^^ | = help: consider removing this trait bound = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#trait_duplication_in_bounds = note: `-W clippy::trait-duplication-in-bounds` implied by `-W clippy::nursery`
Real output of Clippy 0.1.99 (Rust 1.99) on the example below. Names and line numbers in yours will differ.
Does it matter?
Duplicate bounds makes the code less readable than specifying them only once.
New lints still being finished. Off by default and may have false positives.
How to fix it
Clippy can fix this one for you: run cargo clippy --fix (add --allow-dirty if you have uncommitted changes). Review the diff before you commit.
Flagged
fn func<T: Clone + Default>(arg: T) where T: Clone + Default {}
Write this instead
fn func<T: Clone + Default>(arg: T) {}
// or
fn func<T>(arg: T) where T: Clone + Default {}
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]
trait_duplication_in_bounds = "warn"In code
#![warn(clippy::trait_duplication_in_bounds)]One run
cargo clippy -- -W clippy::trait-duplication-in-boundsThe [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
Checks for cases where generics or trait objects are being used and multiple syntax specifications for trait bounds are used simultaneously.
Why is this bad?
Duplicate bounds makes the code less readable than specifying them only once.
Example
fn func<T: Clone + Default>(arg: T) where T: Clone + Default {}
Use instead:
fn func<T: Clone + Default>(arg: T) {}
// or
fn func<T>(arg: T) where T: Clone + Default {}
fn foo<T: Default + Default>(bar: T) {}
Use instead:
fn foo<T: Default>(bar: T) {}
fn foo<T>(bar: T) where T: Default + Default {}
Use instead:
fn foo<T>(bar: T) where T: Default {}
From the Clippy lint list (0.1.99), part of the Rust project, MIT or Apache-2.0. Official entry.
Related lints
- redundant_cloneChecks for a redundant clone() (and its relatives) which clones an owned value that is going to be dropped without further use
- suspicious_operation_groupingsthis sequence of operators looks suspiciously like a bug
- too_long_first_doc_paragraphChecks if the first paragraph in the documentation of items listed in the module page is too long
- trailing_empty_arraytrailing zero-sized array in a struct which is not marked with a `repr` attribute
- transmute_undefined_reprtransmute from `main::Foo<u32>` to `main::Foo<i32>`, both of which have an undefined layout
- trivial_regexChecks for trivial regex creation (with Regex::new, RegexBuilder::new, or RegexSet::new)
- tuple_array_conversionsit looks like you're trying to convert a tuple to an array
All 847 Clippy lints · Rust compiler errors · Cargo.toml checker
Up next
Related lintclippy::redundant_cloneChecks for a redundant clone() (and its relatives) which clones an owned value that is going to be dropped without further useRead it next →Did this answer your question?