Represent Pin<P> in syntax tree
diff --git a/syntax/mod.rs b/syntax/mod.rs
index 94c2cc8..72e815b 100644
--- a/syntax/mod.rs
+++ b/syntax/mod.rs
@@ -170,10 +170,12 @@
 }
 
 pub struct Ref {
+    pub pinned: bool,
     pub ampersand: Token![&],
     pub lifetime: Option<Lifetime>,
     pub mutability: Option<Token![mut]>,
     pub inner: Type,
+    pub pin_tokens: Option<(kw::Pin, Token![<], Token![>])>,
 }
 
 pub struct Slice {