contd

src/0_1_2_generators_pin.md

@@ -116,7 +116,7 @@ struct GeneratorA {
 impl FnMut<()> for GeneratorA {
     type Output = GeneratorState<i32, ()>;
     fn call_mut(&mut self) -> Self::Output {
-        
+        Generatorstate::Yielded(2)
     }
 }
 
@@ -130,6 +130,23 @@ impl FnMut<()> for GeneratorA {
 
 >The `yield` keyword was discussed first in [RFC#1823][rfc1823] and in [RFC#1832][rfc1832].
 
+
+pinning
+```ignore
+// If we borrow through yield points, we end up with this error
+
+  --> src\main.rs:12:11
+   |
+5  |     match gen.resume() {
+   |           --- first mutable borrow occurs here
+...
+12 |     match gen.resume() {
+   |           ^^^
+   |           |
+   |           second mutable borrow occurs here
+   |           first borrow later used here
+```
+
 [rfc2033]: https://github.com/rust-lang/rfcs/blob/master/text/2033-experimental-coroutines.md
 [greenthreads]: https://cfsamson.gitbook.io/green-threads-explained-in-200-lines-of-rust/
 [rfc1823]: https://github.com/rust-lang/rfcs/pull/1823