New lint: map then unwrap

What it does

Detects usage of map(..).unwrap()

Categories (optional)

Kind: pedantic

What is the advantage of the recommended code over the original code

The unwrap effectively only applies to the value before .map(..), so putting it after .map(..) needlessly complicates the semantics of the code.

Drawbacks

None.

Example

opt.map(|n| n * 2).unwrap()

Could be written as:

opt.unwrap() * 2

This should also work with expect as well as maybe other Option and Result transformers like filter.

I think the name map_unwrap is good, even though other method combinations are applicable.