impl PartialEq for Option forces both sides to contain the same T

[nagisa]

The current impl PartialEq for Option looks like this:

impl<T> PartialEq<Option<T>> for Option<T> where
    T: PartialEq<T> { ... }

It could be more general and look like this instead:

impl<A, B> PartialEq<Option<A>> for Option<B> where
    A: PartialEq<B> { ... }

[nagisa]

Specific use-case where I wanted this to work was:

if path.file_stem() == Some("foo") { ... }

[ollie27]

Duplicate of #20063?