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Lints

Note: Cargo’s linting system is unstable and can only be used on nightly toolchains

Warn-by-default

These lints are all set to the ‘warn’ level by default.

blanket_hint_mostly_unused

Set to warn by default

What it does

Checks if hint-mostly-unused being applied to all dependencies.

Why it is bad

hint-mostly-unused indicates that most of a crate’s API surface will go unused by anything depending on it; this hint can speed up the build by attempting to minimize compilation time for items that aren’t used at all. Misapplication to crates that don’t fit that criteria will slow down the build rather than speeding it up. It should be selectively applied to dependencies that meet these criteria. Applying it globally is always a misapplication and will likely slow down the build.

Example

[profile.dev.package."*"]
hint-mostly-unused = true

Should instead be:

[profile.dev.package.huge-mostly-unused-dependency]
hint-mostly-unused = true

unknown_lints

Set to warn by default

What it does

Checks for unknown lints in the [lints.cargo] table

Why it is bad

  • The lint name could be misspelled, leading to confusion as to why it is not working as expected
  • The unknown lint could end up causing an error if cargo decides to make a lint with the same name in the future

Example

[lints.cargo]
this-lint-does-not-exist = "warn"