new lint: infallible TryFrom

What it does

look for

impl TryFrom<TypeA> for TypeB {
  type Error = Infallible;

this is already a blanket implementation for impl From<TypeA> for TypeB, so it would be better to just implement From.

Advantage

• From is simpler and more obvious that it's infallible
• can be used in code which requires From impl

Drawbacks

No response

Example

impl TryFrom<TypeA> for TypeB {
  type Error = Infallible;

  fn try_from(value: TypeA) -> Result<Self, Self::Error> {
    ...
  }
}

Could be written as:

impl From<TypeA> for TypeB {
  fn from(value: bool) -> Self {
    ...
  }
}

No files, tests, or entry points are named. Use the TryFrom for TypeB examples and the Infallible error as the acceptance target: identify infallible TryFrom implementations and verify that the lint recommends an equivalent From implementation.