Rust API Guideline: Functions minimize assumptions about parameters by using generics

[mcarton]

As per Functions minimize assumptions about parameters by using generics.

This is a step further from ptr_arg.

[killercup]

Would you see this as a general lint that tries to cover all cases or a few lints that cover common cases?

General lint:

• For each parameter x of type Type:
  • skip if a non-trait method is called on x
  • collect traits whose methods are called on x as traits (e.g., Debug + ToOwned)
  • suggest to replace Type with a generic type GenericType and add a type parameter GenericType: traits

Common use cases lint (example):

• For each parameter x of type Type, check if it's only used in a for loop and suggest to replace Type with IntoIterator<_>