Function expand_deriving_partial_eq 

pub(crate) fn expand_deriving_partial_eq(
    cx: &ExtCtxt<'_>,
    span: Span,
    item: &Item,
    push: &mut dyn FnMut(Box<Item>),
    is_const: bool,
)

Expands a #[derive(PartialEq)] attribute into an implementation for the target item.