Detect invalid cfg expressions, such as the cfg(feature_s_ = ...) typo #10224
Description
What it does
It's generally easy to mistakenly use features = "x" instead of feature = "x" in cfgs.
To my knowledge, features = "x" doesn't currently have meaning, so it's likely to be the result of a mistake, and not intentional.
The main thing to look out for when looking for this pattern is to ensure that we're within a cfg context.
This can be generalized to ensuring that cfg conditions are always looking at "variables" that actually exist, such as target_family, target_os, etc...
Lint Name
invalid-cfg-condition
Category
correctness, suspicious
Advantage
- Prevent accidental typos that fundamentally alter the behaviour
Drawbacks
- If/when new "variables" are added to cfg conditions, the lint will need to be updated.
Example
#[cfg(features = "std")]
pub use std::error::Error;
const fn std_support_enabled() -> bool { cfg!(features = "std") }Is highly likely to be an attempt at writing:
#[cfg(feature = "std")]
pub use std::error::Error;
const fn std_support_enabled() -> bool { cfg!(feature = "std") }