Detect redundant always successful `assert_eq!`

What it does

Detect if assert_eq! always returns succeeds because the same expression is on the left and right side, such as with assert_eq!(a,a).

These type of cases can happen when refactoring and search'n'replacing code, for example we've recently saw a case of this recently:

   assert_eq!(mem::size_of::<usize>(), mem::size_of::<usize>());

It would however be important that it only lints on the expressions being exactly identical, so if using a type alias in the above example that should not trigger this lint, example:

   type MyType = usize;
   assert_eq!(mem::size_of::<usize>(), mem::size_of::<MyType>());

Lint Name

redundant_assert

Category

pedantic

Advantage

Keeping an assert that has no effect is a code smell and negative value as can leave a false sense of safety in tests / coverage and is additional cognitive overhead without any positive effects.

Drawbacks

Likely none.

Probably not that common occurrence, but does happen.

Example

assert_eq!(mem::size_of::<usize>(), mem::size_of::<usize>());

Assert should simply be removed as it has no effect.

Begin by locating existing assert_eq! lint handling and test coverage in rust-clippy; the issue names the intended lint as redundant_assert. Confirm that it reports only exactly identical expressions, not equivalent expressions using a type alias, and that the redundant assertion can be removed.