From 0568d7e77dbe004864e19a75a2216e233fbfad2b Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Thu, 2 Jul 2026 10:07:12 +0100
Subject: Support translating enums into Rust types

---
 examples/07-enum/hobgoblin.json5                   |  4 +++
 examples/07-enum/output/rust/.gitignore            |  1 +
 examples/07-enum/output/rust/Cargo.lock            |  7 ++++++
 examples/07-enum/output/rust/Cargo.toml            |  6 +++++
 examples/07-enum/output/rust/rust-toolchain.toml   |  2 ++
 examples/07-enum/output/rust/src/main.rs           |  7 ++++++
 examples/07-enum/output/rust/src/numbers.rs        |  6 +++++
 .../generators/rusttypes/RustTypesGenerator.java   | 29 ++++++++++++++++++++--
 8 files changed, 60 insertions(+), 2 deletions(-)
 create mode 100644 examples/07-enum/output/rust/.gitignore
 create mode 100644 examples/07-enum/output/rust/Cargo.lock
 create mode 100644 examples/07-enum/output/rust/Cargo.toml
 create mode 100644 examples/07-enum/output/rust/rust-toolchain.toml
 create mode 100644 examples/07-enum/output/rust/src/main.rs
 create mode 100644 examples/07-enum/output/rust/src/numbers.rs

diff --git a/examples/07-enum/hobgoblin.json5 b/examples/07-enum/hobgoblin.json5
index 1ec9568..2bf59c3 100644
--- a/examples/07-enum/hobgoblin.json5
+++ b/examples/07-enum/hobgoblin.json5
@@ -5,5 +5,9 @@
       path: "output/java/src/gen/java",
       packageName: "org.zwobble.example.types"
     },
+    {
+      generator: "rust-types",
+      path: "output/rust/src",
+    },
   ],
 }
diff --git a/examples/07-enum/output/rust/.gitignore b/examples/07-enum/output/rust/.gitignore
new file mode 100644
index 0000000..ea8c4bf
--- /dev/null
+++ b/examples/07-enum/output/rust/.gitignore
@@ -0,0 +1 @@
+/target
diff --git a/examples/07-enum/output/rust/Cargo.lock b/examples/07-enum/output/rust/Cargo.lock
new file mode 100644
index 0000000..9dc6e3e
--- /dev/null
+++ b/examples/07-enum/output/rust/Cargo.lock
@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "example"
+version = "0.1.0"
diff --git a/examples/07-enum/output/rust/Cargo.toml b/examples/07-enum/output/rust/Cargo.toml
new file mode 100644
index 0000000..5d4c622
--- /dev/null
+++ b/examples/07-enum/output/rust/Cargo.toml
@@ -0,0 +1,6 @@
+[package]
+name = "example"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
diff --git a/examples/07-enum/output/rust/rust-toolchain.toml b/examples/07-enum/output/rust/rust-toolchain.toml
new file mode 100644
index 0000000..4fedb95
--- /dev/null
+++ b/examples/07-enum/output/rust/rust-toolchain.toml
@@ -0,0 +1,2 @@
+[toolchain]
+channel = "1.96"
diff --git a/examples/07-enum/output/rust/src/main.rs b/examples/07-enum/output/rust/src/main.rs
new file mode 100644
index 0000000..2201dcc
--- /dev/null
+++ b/examples/07-enum/output/rust/src/main.rs
@@ -0,0 +1,7 @@
+mod numbers;
+
+use numbers::SmallNumber;
+
+fn main() {
+    let small_number = SmallNumber::One;
+}
diff --git a/examples/07-enum/output/rust/src/numbers.rs b/examples/07-enum/output/rust/src/numbers.rs
new file mode 100644
index 0000000..b71f573
--- /dev/null
+++ b/examples/07-enum/output/rust/src/numbers.rs
@@ -0,0 +1,6 @@
+/// A small number.
+pub enum SmallNumber {
+    Zero,
+    One,
+    Two,
+}
diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/output/generators/rusttypes/RustTypesGenerator.java b/src/main/java/org/zwobble/hobgoblin/compiler/output/generators/rusttypes/RustTypesGenerator.java
index e681a3e..b71c9ed 100644
--- a/src/main/java/org/zwobble/hobgoblin/compiler/output/generators/rusttypes/RustTypesGenerator.java
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/output/generators/rusttypes/RustTypesGenerator.java
@@ -80,7 +80,7 @@ public class RustTypesGenerator implements Generator {
     ) {
         return switch (statement) {
             case TypedEnumDefinitionNode enumDefinition -> {
-                yield List.of();
+                yield generateEnumDefinition(enumDefinition, context);
             }
 
             case TypedNativeTypeDefinitionNode nativeTypeDefinition -> {
@@ -97,6 +97,28 @@ public class RustTypesGenerator implements Generator {
         };
     }
 
+    private List<RustItem> generateEnumDefinition(
+        TypedEnumDefinitionNode enumDefinition,
+        Context context
+    ) {
+        var rustEnumName = generateTypeName(enumDefinition.name());
+
+        var rustVariants = enumDefinition.variants().stream()
+            .map(variant -> new RustEnumVariant(
+                generateVariantName(variant.name()),
+                new RustEnumVariantNoFields()
+            ))
+            .toList();
+
+        var rustEnum = new RustEnum(
+            rustEnumName,
+            rustVariants,
+            enumDefinition.docComment()
+        );
+
+        return List.of(rustEnum);
+    }
+
     private List<RustItem> generateStructDefinition(
         TypedStructDefinitionNode structDefinition,
         Context context
@@ -216,13 +238,16 @@ public class RustTypesGenerator implements Generator {
         return new RustIdentifier(Casing.lowerCamelCaseToSnakeCase(part));
     }
 
+    private RustIdentifier generateVariantName(String enumVariantName) {
+        return generateTypeName(Casing.lowerCamelCaseToUpperCamelCase(enumVariantName));
+    }
+
     private RustIdentifier generateVariantName(Type type) {
         if (type instanceof StructType structType) {
             return generateTypeName(structType.name());
         } else {
             throw new UnsupportedOperationException("TODO");
         }
-
     }
 
     private static class Context {
-- 
cgit v1.2.3