1 files changed, 47 insertions, 11 deletions

diff --git a/net/src/macros.rs b/net/src/macros.rs
index caad17f5..26b79408 100644
--- a/net/src/macros.rs
+++ b/net/src/macros.rs
@@ -4,25 +4,25 @@
 ///
 /// For most types just call it after defining the type:
 ///
-/// ```
+/// ```ignore
 /// pub struct MyStruct {}
 /// assert_send_and_sync!(MyStruct);
 /// ```
 ///
 /// For types with lifetimes, use the anonymous lifetime:
 ///
-/// ```
-/// pub struct WithLifetime<'a> {}
-/// assert_send_and_sync!(MyStruct<'_>);
+/// ```ignore
+/// pub struct WithLifetime<'a> { _p: std::marker::PhantomData<&'a ()> }
+/// assert_send_and_sync!(WithLifetime<'_>);
 /// ```
 ///
 /// For a type generic over another type `W`,
 /// pass the type `W` as a where clause
 /// including a trait bound when needed:
 ///
-/// ```
-/// pub struct MyWriter<W: io::Write> {}
-/// assert_send_and_sync!(MyWriterStruct<W> where W: io::Write);
+/// ```ignore
+/// pub struct MyWriter<W: std::io::Write> { _p: std::marker::PhantomData<W> }
+/// assert_send_and_sync!(MyWriter<W> where W: std::io::Write);
 /// ```
 ///
 /// This will assert that `MyWriterStruct<W>` is `Send` and `Sync`
@@ -32,16 +32,22 @@
 /// Just make sure to list all the types - even those without additional
 /// trait bounds:
 ///
-/// ```
-/// pub struct MyWriterWithLifetime<'a, C, W: io::Write> {};
-/// assert_send_and_sync!(MyWriterStruct<'_, C, W> where C, W: io::Write);
+/// ```ignore
+/// pub struct MyWriterWithLifetime<'a, C, W: std::io::Write> {
+///     _p: std::marker::PhantomData<&'a (C, W)>,
+/// }
+/// assert_send_and_sync!(MyWriterWithLifetime<'_, C, W> where C, W: std::io::Write);
 /// ```
 ///
 /// If you need multiple additional trait bounds on a single type
 /// you can add them separated by `+` like in normal where clauses.
 /// However you have to make sure they are `Identifiers` like `Write`.
-/// In macro patterns `Paths` (like `io::Write`) may not be followed
+/// In macro patterns `Paths` (like `std::io::Write`) may not be followed
 /// by `+` characters.
+// Note: We cannot test the macro in doctests, because the macro is
+// not public.  We test the cases in the test module below, instead.
+// If you change the examples here, propagate the changes to the
+// module below.
 macro_rules! assert_send_and_sync {
     ( $x:ty where $( $g:ident$( : $a:path )? $(,)?)*) => {
         impl<$( $g ),*> crate::macros::Sendable for $x
@@ -67,3 +73,33 @@ macro_rules! assert_send_and_sync {
 
 pub(crate) trait Sendable : Send {}
 pub(crate) trait Syncable : Sync {}
+
+/// We cannot test the macro in doctests, because the macro is not
+/// public.  We test the cases here, instead.  If you change the
+/// examples here, propagate the changes to the docstring above.
+#[cfg(test)]
+mod test {
+    /// For most types just call it after defining the type:
+    pub struct MyStruct {}
+    assert_send_and_sync!(MyStruct);
+
+    /// For types with lifetimes, use the anonymous lifetime:
+    pub struct WithLifetime<'a> { _p: std::marker::PhantomData<&'a ()> }
+    assert_send_and_sync!(WithLifetime<'_>);
+
+    /// For a type generic over another type `W`, pass the type `W` as
+    /// a where clause including a trait bound when needed:
+    pub struct MyWriter<W: std::io::Write> { _p: std::marker::PhantomData<W> }
+    assert_send_and_sync!(MyWriter<W> where W: std::io::Write);
+
+    /// This will assert that `MyWriterStruct<W>` is `Send` and `Sync`
+    /// if `W` is `Send` and `Sync`.
+    ///
+    /// You can also combine the two and be generic over multiple
+    /// types.  Just make sure to list all the types - even those
+    /// without additional trait bounds:
+    pub struct MyWriterWithLifetime<'a, C, W: std::io::Write> {
+        _p: std::marker::PhantomData<&'a (C, W)>,
+    }
+    assert_send_and_sync!(MyWriterWithLifetime<'_, C, W> where C, W: std::io::Write);
+}