Fix ABI generation for struct return types

examples/nested_structs/abi.sol

@@ -11,7 +11,7 @@ interface INestedStructs {
 
     function addDogs(address user, Dog[] memory dogs) external;
 
-    function getUser(address _address) external view returns (User);
+    function getUser(address _address) external view returns (User memory);
 
     function getAllUsers() external view returns (User[] memory);
 

stylus-proc/src/macros/derive/abi_type/mod.rs

@@ -73,6 +73,8 @@ impl<E: DeriveAbiTypeExtension> DeriveAbiTypeGenerator<E> {
                         .concat(#fields_selector_abis)
                     )*
                     .concat(#ConstString::new(")"));
+
+                const EXPORT_ABI_RET: #ConstString = #ConstString::new(#name_str).concat(#ConstString::new(" memory"));
             }
         }
     }
@@ -136,6 +138,7 @@ mod tests {
                     .concat(stylus_sdk::abi::ConstString::new(","))
                     .concat(<T as stylus_sdk::abi::AbiType>::SELECTOR_ABI)
                     .concat(stylus_sdk::abi::ConstString::new(")"));
+                const EXPORT_ABI_RET: stylus_sdk::abi::ConstString = stylus_sdk::abi::ConstString::new("Foo").concat(stylus_sdk::abi::ConstString::new(" memory"));
             }
         };
         assert_ast_eq(result, expected);

stylus-proc/tests/contract_abi.rs

@@ -42,7 +42,7 @@ interface ICounter is ITrait1, ITrait2 {
 
     function mixed(MixedInput input) external;
 
-    function mixedResult() external view returns (MixedResult);
+    function mixedResult() external view returns (MixedResult memory);
 
     struct MixedResult {uint256 number;string text;uint256 number2;}
 }