Update SharedPtr target type check

These types were implemented in #563.
diff --git a/syntax/check.rs b/syntax/check.rs
index f43c1e2..52ee693 100644
--- a/syntax/check.rs
+++ b/syntax/check.rs
@@ -139,12 +139,10 @@
         }
 
         match Atom::from(&ident.rust) {
-            None => return,
-            Some(CxxString) => {
-                cx.error(ptr, "std::shared_ptr<std::string> is not supported yet");
-                return;
-            }
-            _ => {}
+            None | Some(U8) | Some(U16) | Some(U32) | Some(U64) | Some(Usize) | Some(I8)
+            | Some(I16) | Some(I32) | Some(I64) | Some(Isize) | Some(F32) | Some(F64)
+            | Some(CxxString) => return,
+            Some(Bool) | Some(Char) | Some(RustString) => {}
         }
     } else if let Type::CxxVector(_) = &ptr.inner {
         cx.error(ptr, "std::shared_ptr<std::vector> is not supported yet");