Use the now-idiomatic option? syntax

This works in Rust now:

    foo?;

as a replacement for:

    if foo.is_none() {
        return None;
    }

It's similar to ? for error handling and can only be used in functions
that return an Option.

The instance of this in a macro caused the problem to be reported a
lot of time, once per time the macro was used, but luckily it can
could be fixed in only one place. Magic!

Found by clippy lint question_mark:
https://rust-lang.github.io/rust-clippy/master/index.html#question_mark

1 files changed, 2 insertions, 4 deletions

diff --git a/ffi-macros/src/lib.rs b/ffi-macros/src/lib.rs
index 07093733..ab4e295f 100644
--- a/ffi-macros/src/lib.rs
+++ b/ffi-macros/src/lib.rs
@@ -584,11 +584,9 @@ fn derive_conversion_functions(mut st: syn::ItemStruct,
             crate::Maybe<#wrapper #generics>
         {
             fn ref_mut_raw(self) -> Option<& #ref_lifetime mut #wrapped> {
-                if self.is_none() {
-                    return None;
-                }
+                self?;
                 let wrapper = unsafe {
-                    &mut (*self.unwrap().as_ptr())
+                    &mut (*self?.as_ptr())
                 };
                 wrapper.assert_tag();
                 match wrapper.0 {