Macro parse_item_fn 

macro_rules! parse_item_fn {
    ($($args:tt)*) => { ... };
}

Parse an item fn

Example:

macro_rules! expect_item_fn {
    (
        item_fn {
            $(outer_attrs { #[cfg(..)] })? // present if there are outer attributes
            vis {$vis:tt}
            sig {
                                      // the following keywords are present if specified
                $(default {default})?
                $(const   {const}  )?
                $(async   {async}  )?
                $(unsafe  {unsafe} )?
                $(extern  {extern $($extern_name:literal)?})?

                fn { fn }
                ident { get }

                $(                                   // present if there is `<...>`
                    lt {<}
                    parsed_generics $parsed_generics:tt
                    gt {>}
                )?

                paren_inputs { (self) }
                output { $(-> $output_ty:ty)? }

                $(                                      // present if there is where clause
                    where_clause { where $($where_clause:tt)* }
                )?
            }
                                 // either block or semicolon will be present
            $(block { {..} })?   // present if there is a block as fn body
            $(semicolon { ; })?  // present if there is a semicolon
        }
        rest {}
    ) => {};
}

syn_lite::parse_item_fn! {
    on_finish { expect_item_fn! }
    input {
        #[cfg(..)]
        fn get<T>(self) -> Option<T>
        where
            Self: Sized,
        {
            ..
        }
    }
}