Escape 'type' keyword in generated Rust code

Use raw identifiers for fields named "type" to avoid conflicts with the
Rust keyword. Fix field number indexing in tests.

src/generator.rs

@@ -224,11 +224,12 @@ pub fn generate_rust_code(set: &FileDescriptorSet) -> String {
             // Field Accessors
             for (field_name, tag, f_type, f_label) in fields_info {
                 let (rust_type, logic) = map_type_to_rust_accessor(f_type, f_label);
+                let safe_name = if field_name == "type" { format!("r#{}", field_name) } else { field_name.clone() };
 
                 if f_label == 3 {
                     output.push_str(&format!(
                         "    pub fn {}(&self) -> {} {{\n",
-                        field_name, rust_type
+                        safe_name, rust_type
                     ));
                     output.push_str(&format!(
                         "        match (self.{}_start, self.{}_end) {{\n",
@@ -246,7 +247,7 @@ pub fn generate_rust_code(set: &FileDescriptorSet) -> String {
                 } else {
                     output.push_str(&format!(
                         "    pub fn {}(&self) -> Result<{}> {{\n",
-                        field_name, rust_type
+                        safe_name, rust_type
                     ));
                     output.push_str(&format!(
                         "        let offset = self.{}_offset.ok_or(RotoError::FieldNotFound)?;\n",
@@ -275,6 +276,7 @@ pub fn generate_rust_code(set: &FileDescriptorSet) -> String {
                 let (field_data, _) = field_res.expect("Failed to iterate field");
                 let field_proto = FieldDescriptorProto::new(field_data).expect("Failed to parse FieldDescriptorProto");
                 let field_name = field_proto.name().unwrap();
+                let safe_name = if field_name == "type" { format!("r#{}", field_name) } else { field_name.to_string() };
 
                 let tag = field_proto.number().unwrap();
                 let f_type = field_proto.field_type().unwrap() as i32;
@@ -283,7 +285,7 @@ pub fn generate_rust_code(set: &FileDescriptorSet) -> String {
 
                 output.push_str(&format!(
                     "    pub fn {}(mut self, value: {}) -> Result<Self> {{\n        self.builder.{}({}, value)?;\n        Ok(self)\n    }}\n\n",
-                    field_name, rust_type, method, tag
+                    safe_name, rust_type, method, tag
                 ));
             }
 

src/lib.rs

@@ -520,7 +520,7 @@ mod tests {
 
         // Validate that fields appear in the expected relative order
         let field_numbers: Vec<u32> = acc.fields()
-            .map(|r| r.expect("Failed to decode field").0.field_number)
+            .map(|r| r.expect("Failed to decode field").1.field_number)
             .collect();
 
         let essential_fields = [1, 2, 3, 14, 16, 20];