Distinguish references from pointers.

Using a custom attribute.

Author: adetaylor

src/codegen/error.rs

@@ -11,6 +11,9 @@ pub enum Error {
     /// definition that is too difficult for us to understand (like a partial
     /// template specialization).
     InstantiationOfOpaqueType,
+
+    /// Type was a reference not a pointer, but we had nowhere to record that fact.
+    ReferenceButCouldNotRecord,
 }
 
 impl fmt::Display for Error {
@@ -23,6 +26,9 @@ impl fmt::Display for Error {
                 "Instantiation of opaque template type or partial template \
                  specialization"
             }
+            Error::ReferenceButCouldNotRecord => {
+                "Type was a reference in a context where we only expected other types"
+            }
         })
     }
 }

src/codegen/helpers.rs

@@ -74,6 +74,18 @@ pub mod attributes {
             #[bindgen_original_name(#name)]
         }
     }
+
+    pub fn ret_type_reference() -> TokenStream {
+        quote! {
+            #[bindgen_ret_type_reference]
+        }
+    }
+
+    pub fn arg_type_reference(arg_name: &Ident) -> TokenStream {
+        quote! {
+            #[bindgen_arg_type_reference(#arg_name)]
+        }
+    }
 }
 
 /// Generates a proper type for a field or type with a given `Layout`, that is,