clippy::disallowed_methods: Denies the configured methods and functions in clippy.toml Note: Even though this lint is warn-by-default, it will only trigger if methods are defined in the clippy.toml file

let xs = vec![1, 2, 3, 4];
xs.leak(); // Vec::leak is disallowed in the config.
// The diagnostic contains the message "no leaking memory".

let _now = Instant::now(); // Instant::now is disallowed in the config.

let _box = Box::new(3); // Box::new is disallowed in the config.

let mut xs = Vec::new(); // Vec::new is _not_ disallowed in the config.
xs.push(123); // Vec::push is _not_ disallowed in the config.

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

[lints.clippy]
disallowed_methods = "allow"

cargo clippy -- -A clippy::disallowed-methods

Clippy's own documentation

What it does

Denies the configured methods and functions in clippy.toml

Note: Even though this lint is warn-by-default, it will only trigger if methods are defined in the clippy.toml file.

Why is this bad?

Some methods are undesirable in certain contexts, and it’s beneficial to lint for them as needed.

Example

An example clippy.toml configuration:

disallowed-methods = [
    # Can use a string as the path of the disallowed method.
    "std::boxed::Box::new",
    # Can also use an inline table with a `path` key.
    { path = "std::time::Instant::now" },
    # When using an inline table, can add a `reason` for why the method
    # is disallowed.
    { path = "std::vec::Vec::leak", reason = "no leaking memory" },
    # Can also add a `replacement` that will be offered as a suggestion.
    { path = "std::sync::Mutex::new", reason = "prefer faster & simpler non-poisonable mutex", replacement = "parking_lot::Mutex::new" },
    # This would normally error if the path is incorrect, but with `allow-invalid` = `true`,
    # it will be silently ignored
    { path = "std::fs::InvalidPath", reason = "use alternative instead", allow-invalid = true },
]

let xs = vec![1, 2, 3, 4];
xs.leak(); // Vec::leak is disallowed in the config.
// The diagnostic contains the message "no leaking memory".

let _now = Instant::now(); // Instant::now is disallowed in the config.

let _box = Box::new(3); // Box::new is disallowed in the config.

Use instead:

let mut xs = Vec::new(); // Vec::new is _not_ disallowed in the config.
xs.push(123); // Vec::push is _not_ disallowed in the config.

Past names

• disallowed_method

Configuration

• disallowed-methods: The list of disallowed methods, written as fully qualified paths.

Fields:

• path (required): the fully qualified path to the method that should be disallowed

• reason (optional): explanation why this method is disallowed

• replacement (optional): suggested alternative method

• allow-invalid (optional, false by default): when set to true, it will ignore this entry if the path doesn’t exist, instead of emitting an error

  (default: [])

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
• default_instead_of_iter_empty`std::iter::empty()` is the more idiomatic way
• disallowed_fieldsDenies the configured fields in clippy.toml Note: Even though this lint is warn-by-default, it will only trigger if fields are defined in the clippy.toml file
• disallowed_macrosDenies the configured macros in clippy.toml Note: Even though this lint is warn-by-default, it will only trigger if macros are defined in the clippy.toml file
• disallowed_namesuse of a disallowed/placeholder name `foo`
• disallowed_typesDenies the configured types in clippy.toml. Note: Even though this lint is warn-by-default, it will only trigger if types are defined in the clippy.toml file
• doc_lazy_continuationdoc quote line without `>` marker

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