From 2f76934bf2aa59f78b671c722b73f0d69c7adbd3 Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Fri, 31 Jul 2026 10:57:39 +0100
Subject: Handle singleton structs in Rust

---
 .../compiler/output/lang/rust/RustWriterTests.java | 30 +++++++++++++++-------
 .../lang/rust/ast/RustStructStructMatcher.java     |  2 +-
 2 files changed, 22 insertions(+), 10 deletions(-)

(limited to 'src/test')

diff --git a/src/test/java/org/zwobble/hobgoblin/compiler/output/lang/rust/RustWriterTests.java b/src/test/java/org/zwobble/hobgoblin/compiler/output/lang/rust/RustWriterTests.java
index 4a81031..56d6d87 100644
--- a/src/test/java/org/zwobble/hobgoblin/compiler/output/lang/rust/RustWriterTests.java
+++ b/src/test/java/org/zwobble/hobgoblin/compiler/output/lang/rust/RustWriterTests.java
@@ -28,11 +28,9 @@ public class RustWriterTests {
         assertThat(string, equalTo("""
             // Generated by hobgoblin.
 
-            pub struct Rectangle {
-            }
+            pub struct Rectangle;
             
-            pub struct Square {
-            }
+            pub struct Square;
             """));
     }
 
@@ -111,9 +109,25 @@ public class RustWriterTests {
 
     // === Structs ===
 
+    @Test
+    public void unitLikeStruct() throws IOException {
+        var rust = RustStructStruct.arbitrary()
+            .withName(new RustIdentifier("Rectangle"))
+            .withFields(Optional.empty())
+            .build();
+
+        var string = write(writer -> writer.writeItem(rust));
+
+        assertThat(string, equalTo("""
+            pub struct Rectangle;"""));
+    }
+
     @Test
     public void emptyStruct() throws IOException {
-        var rust = RustStructStruct.arbitrary().withName(new RustIdentifier("Rectangle")).build();
+        var rust = RustStructStruct.arbitrary()
+            .withName(new RustIdentifier("Rectangle"))
+            .withFields(List.of())
+            .build();
 
         var string = write(writer -> writer.writeItem(rust));
 
@@ -137,8 +151,7 @@ public class RustWriterTests {
         assertThat(string, equalTo("""
             #[a::b::C]
             #[derive(Debug)]
-            pub struct Rectangle {
-            }"""));
+            pub struct Rectangle;"""));
     }
 
     @Test
@@ -171,8 +184,7 @@ public class RustWriterTests {
 
         assertThat(string, equalTo("""
             /// A 2D rectangle.
-            pub struct Rectangle {
-            }"""));
+            pub struct Rectangle;"""));
     }
 
     // === Enumerations ===
diff --git a/src/test/java/org/zwobble/hobgoblin/compiler/output/lang/rust/ast/RustStructStructMatcher.java b/src/test/java/org/zwobble/hobgoblin/compiler/output/lang/rust/ast/RustStructStructMatcher.java
index b2109c1..6f04455 100644
--- a/src/test/java/org/zwobble/hobgoblin/compiler/output/lang/rust/ast/RustStructStructMatcher.java
+++ b/src/test/java/org/zwobble/hobgoblin/compiler/output/lang/rust/ast/RustStructStructMatcher.java
@@ -42,7 +42,7 @@ public class RustStructStructMatcher implements org.zwobble.precisely.Matcher<ja
         return new org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStructMatcher(submatchers);
     }
 
-    public org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStructMatcher withFields(org.zwobble.precisely.Matcher<? super java.util.List<org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructField>> fields) {
+    public org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStructMatcher withFields(org.zwobble.precisely.Matcher<? super java.util.Optional<java.util.List<org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructField>>> fields) {
         var submatchers = new java.util.ArrayList<org.zwobble.precisely.Matcher<? super org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStruct>>(this.submatchers);
         submatchers.add(org.zwobble.precisely.Matchers.has("fields", org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStruct::fields, fields));
         return new org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStructMatcher(submatchers);
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