[Rust] impl Display for generate enum items

Author: wbprime

rust/tests/baseline_enum_to_str.rs

@@ -0,0 +1,14 @@
+use examples_baseline::{
+    boost_type::BoostType,
+};
+
+#[test]
+fn test_boost_type_from_str() -> Result<(), ()> {
+    assert_eq!(format!("{}", BoostType::TURBO), "TURBO", "Display \"TURBO\"");
+    assert_eq!(format!("{}", BoostType::SUPERCHARGER), "SUPERCHARGER", "Display \"SUPERCHARGER\"");
+    assert_eq!(format!("{}", BoostType::NITROUS), "NITROUS", "Display \"NITROUS\"");
+    assert_eq!(format!("{}", BoostType::KERS), "KERS", "Display \"KERS\"");
+    assert_eq!(format!("{}", BoostType::NullVal), "NullVal", "Display \"NullVal\"");
+
+    Ok(())
+}

sbe-tool/src/main/java/uk/co/real_logic/sbe/generation/rust/RustGenerator.java

@@ -1299,6 +1299,21 @@ private static void generateEnum(
         indent(writer, 2, "}\n");
         indent(writer, 1, "}\n");
         indent(writer, 0, "}\n");
+
+        // Display impl
+        indent(writer, 0, "impl core::fmt::Display for %s {\n", enumRustName);
+        indent(writer, 1, "#[inline]\n");
+        indent(writer, 1, "fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {\n", primitiveType);
+        indent(writer, 2, "match self {\n");
+        for (final Token token : messageBody)
+        {
+            indent(writer, 3, "Self::%1$s => write!(f, \"%1$s\"), \n", token.name());
+        }
+        // default => Err
+        indent(writer, 3, "Self::NullVal => write!(f, \"NullVal\"),\n");
+        indent(writer, 2, "}\n");
+        indent(writer, 1, "}\n");
+        indent(writer, 0, "}\n");
     }
 
     private static void generateComposites(