clippy::redundant_pattern_matching: Lint for redundant pattern matching over Result, Option, std::task::Poll, std::net::IpAddr or bools

if let Ok(_) = Ok::<i32, i32>(42) {}
if let Err(_) = Err::<i32, i32>(42) {}
if let None = None::<()> {}
if let Some(_) = Some(42) {}
if let Poll::Pending = Poll::Pending::<()> {}
if let Poll::Ready(_) = Poll::Ready(42) {}
if let IpAddr::V4(_) = IpAddr::V4(Ipv4Addr::LOCALHOST) {}
if let IpAddr::V6(_) = IpAddr::V6(Ipv6Addr::LOCALHOST) {}
match Ok::<i32, i32>(42) {
    Ok(_) => true,
    Err(_) => false,
};

let cond = true;
if let true = cond {}
matches!(cond, true);

if Ok::<i32, i32>(42).is_ok() {}
if Err::<i32, i32>(42).is_err() {}
if None::<()>.is_none() {}
if Some(42).is_some() {}
if Poll::Pending::<()>.is_pending() {}
if Poll::Ready(42).is_ready() {}
if IpAddr::V4(Ipv4Addr::LOCALHOST).is_ipv4() {}
if IpAddr::V6(Ipv6Addr::LOCALHOST).is_ipv6() {}
Ok::<i32, i32>(42).is_ok();

let cond = true;
if cond {}
cond;

#[allow(clippy::redundant_pattern_matching)]
fn my_function() { /* ... */ }

[lints.clippy]
redundant_pattern_matching = "allow"

cargo clippy -- -A clippy::redundant-pattern-matching

Clippy's own documentation

What it does

Lint for redundant pattern matching over Result, Option, std::task::Poll, std::net::IpAddr or bools

Why is this bad?

It’s more concise and clear to just use the proper utility function or using the condition directly

Known problems

For suggestions involving bindings in patterns, this will change the drop order for the matched type. Both if let and while let will drop the value at the end of the block, both if and while will drop the value before entering the block. For most types this change will not matter, but for a few types this will not be an acceptable change (e.g. locks). See the reference for more about drop order.

Example

if let Ok(_) = Ok::<i32, i32>(42) {}
if let Err(_) = Err::<i32, i32>(42) {}
if let None = None::<()> {}
if let Some(_) = Some(42) {}
if let Poll::Pending = Poll::Pending::<()> {}
if let Poll::Ready(_) = Poll::Ready(42) {}
if let IpAddr::V4(_) = IpAddr::V4(Ipv4Addr::LOCALHOST) {}
if let IpAddr::V6(_) = IpAddr::V6(Ipv6Addr::LOCALHOST) {}
match Ok::<i32, i32>(42) {
    Ok(_) => true,
    Err(_) => false,
};

let cond = true;
if let true = cond {}
matches!(cond, true);

The more idiomatic use would be:

if Ok::<i32, i32>(42).is_ok() {}
if Err::<i32, i32>(42).is_err() {}
if None::<()>.is_none() {}
if Some(42).is_some() {}
if Poll::Pending::<()>.is_pending() {}
if Poll::Ready(42).is_ready() {}
if IpAddr::V4(Ipv4Addr::LOCALHOST).is_ipv4() {}
if IpAddr::V6(Ipv6Addr::LOCALHOST).is_ipv6() {}
Ok::<i32, i32>(42).is_ok();

let cond = true;
if cond {}
cond;

Past names

• if_let_redundant_pattern_matching

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
• redundant_closureChecks for closures which just call another function where the function can be called directly
• redundant_field_namesredundant field names in struct initialization
• redundant_patternthe `y @ _` pattern can be written as just `y`
• redundant_static_lifetimesconstants have by default a `'static` lifetime
• result_map_or_into_optionChecks for usage of _.map_or(None, Some)
• result_unit_errthis returns a `Result<_, ()>`

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