RS.CLIPPY.DISALLOWED_TYPES

Use of disallowed types

This checker is a Clippy lint created by The Rust Project Contributors. The documentation shown here is a copy of the original documentation for: disallowed_types. Copyright ©2025 The Rust Team. All rights reserved.

What it does

Denies 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.

Why is this bad?

Some types are undesirable in certain contexts.

Example:

An example clippy.toml configuration:

disallowed-types = [
    # Can use a string as the path of the disallowed type.
    "std::collections::BTreeMap",
    # Can also use an inline table with a `path` key.
    { path = "std::net::TcpListener" },
    # When using an inline table, can add a `reason` for why the type
    # is disallowed.
    { path = "std::net::Ipv4Addr", reason = "no IPv4 allowed" },
    # Can also add a `replacement` that will be offered as a suggestion.
    { path = "std::sync::Mutex", reason = "prefer faster & simpler non-poisonable mutex", replacement = "parking_lot::Mutex" },
]

use std::collections::BTreeMap;
// or its use
let x = std::collections::BTreeMap::new();

Use instead:

// A similar type that is allowed by the config
use std::collections::HashMap;

Past names

disallowed_type

Configuration

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

(default: [])