Clippy lints / Style
Clippy lint · Style · checked with Clippy 0.1.99
clippy::builtin_type_shadow: this generic shadows the built-in type `u32`
What it meansWarns if a generic shadows a built-in type. It is in the style group and warns by default.
What you see
warning: this generic shadows the built-in type `u32` --> main.rs:3:6 | 3 | impl<u32> Foo<u32> { | ^^^ | = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#builtin_type_shadow = note: `#[warn(clippy::builtin_type_shadow)]` on by default
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?
This gives surprising type errors.
Code that works but is not idiomatic Rust. Warns by default.
How to fix it
Clippy does not fix this one automatically. Change the code by hand:
Flagged
impl<u32> Foo<u32> {
fn impl_func(&self) -> u32 {
42
}
}
Turn it off, or on
Allow it where it does not fit your code, as narrowly as you can:
On one item
#[allow(clippy::builtin_type_shadow)]
fn my_function() { /* ... */ }Whole crate (Cargo.toml)
[lints.clippy]
builtin_type_shadow = "allow"One run
cargo clippy -- -A clippy::builtin-type-shadowThe [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
Warns if a generic shadows a built-in type.
Why is this bad?
This gives surprising type errors.
Example
impl<u32> Foo<u32> {
fn impl_func(&self) -> u32 {
42
}
}
From the Clippy lint list (0.1.99), part of the Rust project, MIT or Apache-2.0. Official entry.
Related lints
- needless_returnunneeded `return` statement
- new_without_defaultChecks for public types with a pub fn new() -> Self method and no implementation of Default
- len_zeroChecks for getting the length of something via .len() just to compare to zero, and suggests using .is_empty() where applicable
- bool_assert_comparisonused `assert_eq!` with a literal bool
- borrow_interior_mutable_constborrow of a named constant with interior mutability
- box_default`Box::new(_)` of default value
- byte_char_slicescan be more succinctly written as a byte str
- bytes_nthcalled `.bytes().nth()` on a `str`
- chars_last_cmpChecks for usage of _.chars().last() or _.chars().next_back() on a str to check if it ends with a given char
All 847 Clippy lints · Rust compiler errors · Cargo.toml checker
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