diff --git a/crates/codegen/parser/runtime/src/diagnostic.rs b/crates/codegen/parser/runtime/src/diagnostic.rs
index 6e5facf296..049379da7f 100644
--- a/crates/codegen/parser/runtime/src/diagnostic.rs
+++ b/crates/codegen/parser/runtime/src/diagnostic.rs
@@ -1,5 +1,5 @@
+use std::borrow::Cow;
 use std::error::Error;
-use std::fmt::Display;
 
 use crate::text_index::TextRange;
 
@@ -13,7 +13,9 @@ pub enum Severity {
 
 pub trait Diagnostic: Error {
     fn range(&self) -> TextRange;
-    fn code(&self) -> Box<dyn Display>;
+    fn code(&self) -> Option<Cow<'_, str>> {
+        None
+    }
     fn severity(&self) -> Severity;
     fn message(&self) -> String;
 }
diff --git a/crates/codegen/parser/runtime/src/napi_interface/diagnostic.rs b/crates/codegen/parser/runtime/src/napi_interface/diagnostic.rs
index 2e35acd6b7..21ba249115 100644
--- a/crates/codegen/parser/runtime/src/napi_interface/diagnostic.rs
+++ b/crates/codegen/parser/runtime/src/napi_interface/diagnostic.rs
@@ -46,6 +46,6 @@ impl Diagnostic {
 
     #[napi]
     pub fn code(&self) -> String {
-        self.0.code().to_string()
+        self.0.code().unwrap_or_default().into_owned()
     }
 }
diff --git a/crates/codegen/parser/runtime/src/parse_error.rs b/crates/codegen/parser/runtime/src/parse_error.rs
index 54baa77530..c26f9a0e89 100644
--- a/crates/codegen/parser/runtime/src/parse_error.rs
+++ b/crates/codegen/parser/runtime/src/parse_error.rs
@@ -59,10 +59,6 @@ impl Diagnostic for ParseError {
         self.text_range.clone()
     }
 
-    fn code(&self) -> Box<dyn std::fmt::Display> {
-        Box::new("ParseError")
-    }
-
     fn severity(&self) -> diagnostic::Severity {
         diagnostic::Severity::Error
     }
diff --git a/crates/solidity/outputs/cargo/slang_solidity/src/generated/diagnostic.rs b/crates/solidity/outputs/cargo/slang_solidity/src/generated/diagnostic.rs
index 999c05589f..9ccea34247 100644
--- a/crates/solidity/outputs/cargo/slang_solidity/src/generated/diagnostic.rs
+++ b/crates/solidity/outputs/cargo/slang_solidity/src/generated/diagnostic.rs
@@ -1,7 +1,7 @@
 // This file is generated automatically by infrastructure scripts. Please don't edit by hand.
 
+use std::borrow::Cow;
 use std::error::Error;
-use std::fmt::Display;
 
 use crate::text_index::TextRange;
 
@@ -15,7 +15,9 @@ pub enum Severity {
 
 pub trait Diagnostic: Error {
     fn range(&self) -> TextRange;
-    fn code(&self) -> Box<dyn Display>;
+    fn code(&self) -> Option<Cow<'_, str>> {
+        None
+    }
     fn severity(&self) -> Severity;
     fn message(&self) -> String;
 }
diff --git a/crates/solidity/outputs/cargo/slang_solidity/src/generated/napi_interface/diagnostic.rs b/crates/solidity/outputs/cargo/slang_solidity/src/generated/napi_interface/diagnostic.rs
index 35830141cd..9659273c99 100644
--- a/crates/solidity/outputs/cargo/slang_solidity/src/generated/napi_interface/diagnostic.rs
+++ b/crates/solidity/outputs/cargo/slang_solidity/src/generated/napi_interface/diagnostic.rs
@@ -48,6 +48,6 @@ impl Diagnostic {
 
     #[napi]
     pub fn code(&self) -> String {
-        self.0.code().to_string()
+        self.0.code().unwrap_or_default().into_owned()
     }
 }
diff --git a/crates/solidity/outputs/cargo/slang_solidity/src/generated/parse_error.rs b/crates/solidity/outputs/cargo/slang_solidity/src/generated/parse_error.rs
index cc5c56f48c..b9a1a74eac 100644
--- a/crates/solidity/outputs/cargo/slang_solidity/src/generated/parse_error.rs
+++ b/crates/solidity/outputs/cargo/slang_solidity/src/generated/parse_error.rs
@@ -61,10 +61,6 @@ impl Diagnostic for ParseError {
         self.text_range.clone()
     }
 
-    fn code(&self) -> Box<dyn std::fmt::Display> {
-        Box::new("ParseError")
-    }
-
     fn severity(&self) -> diagnostic::Severity {
         diagnostic::Severity::Error
     }
diff --git a/crates/testlang/outputs/cargo/slang_testlang/src/generated/diagnostic.rs b/crates/testlang/outputs/cargo/slang_testlang/src/generated/diagnostic.rs
index 999c05589f..9ccea34247 100644
--- a/crates/testlang/outputs/cargo/slang_testlang/src/generated/diagnostic.rs
+++ b/crates/testlang/outputs/cargo/slang_testlang/src/generated/diagnostic.rs
@@ -1,7 +1,7 @@
 // This file is generated automatically by infrastructure scripts. Please don't edit by hand.
 
+use std::borrow::Cow;
 use std::error::Error;
-use std::fmt::Display;
 
 use crate::text_index::TextRange;
 
@@ -15,7 +15,9 @@ pub enum Severity {
 
 pub trait Diagnostic: Error {
     fn range(&self) -> TextRange;
-    fn code(&self) -> Box<dyn Display>;
+    fn code(&self) -> Option<Cow<'_, str>> {
+        None
+    }
     fn severity(&self) -> Severity;
     fn message(&self) -> String;
 }
diff --git a/crates/testlang/outputs/cargo/slang_testlang/src/generated/napi_interface/diagnostic.rs b/crates/testlang/outputs/cargo/slang_testlang/src/generated/napi_interface/diagnostic.rs
index 35830141cd..9659273c99 100644
--- a/crates/testlang/outputs/cargo/slang_testlang/src/generated/napi_interface/diagnostic.rs
+++ b/crates/testlang/outputs/cargo/slang_testlang/src/generated/napi_interface/diagnostic.rs
@@ -48,6 +48,6 @@ impl Diagnostic {
 
     #[napi]
     pub fn code(&self) -> String {
-        self.0.code().to_string()
+        self.0.code().unwrap_or_default().into_owned()
     }
 }
diff --git a/crates/testlang/outputs/cargo/slang_testlang/src/generated/parse_error.rs b/crates/testlang/outputs/cargo/slang_testlang/src/generated/parse_error.rs
index cc5c56f48c..b9a1a74eac 100644
--- a/crates/testlang/outputs/cargo/slang_testlang/src/generated/parse_error.rs
+++ b/crates/testlang/outputs/cargo/slang_testlang/src/generated/parse_error.rs
@@ -61,10 +61,6 @@ impl Diagnostic for ParseError {
         self.text_range.clone()
     }
 
-    fn code(&self) -> Box<dyn std::fmt::Display> {
-        Box::new("ParseError")
-    }
-
     fn severity(&self) -> diagnostic::Severity {
         diagnostic::Severity::Error
     }