Add function pointer types to syntax tree
diff --git a/gen/write.rs b/gen/write.rs
index ff5670c..8883d9b 100644
--- a/gen/write.rs
+++ b/gen/write.rs
@@ -608,6 +608,7 @@
         Type::Str(_) => {
             write!(out, "::rust::Str");
         }
+        Type::Fn(_) => unimplemented!(),
         Type::Void(_) => unreachable!(),
     }
 }
@@ -617,6 +618,7 @@
     match ty {
         Type::Ident(_) | Type::RustBox(_) | Type::UniquePtr(_) | Type::Str(_) => write!(out, " "),
         Type::Ref(_) => {}
+        Type::Fn(_) => unimplemented!(),
         Type::Void(_) => unreachable!(),
     }
 }