Handle singleton structs in Rust

5 files changed, 43 insertions, 36 deletions

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 8ed9d9e..39a0b8b 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
@@ -127,12 +127,14 @@ public class RustTypesGenerator implements Generator {
 
         var rustStructName = this.rustGenerator.generateTypeName(structDefinition.name());
 
-        var rustFields = structDefinition.fields().orElse(List.of()).stream()
-            .map(field -> new RustStructField(
-                this.rustGenerator.generateFieldName(field.name()),
-                generateRustTypeExpression(field.type(), context)
-            ))
-            .toList();
+        var rustFields = structDefinition.fields().map(
+            fields -> fields.stream()
+                .map(field -> new RustStructField(
+                    this.rustGenerator.generateFieldName(field.name()),
+                    generateRustTypeExpression(field.type(), context)
+                ))
+                .toList()
+        );
 
         var rustStruct = new RustStructStruct(
             rustAttributes,
diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/rust/RustWriter.java b/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/rust/RustWriter.java
index d0552ad..668cd75 100644
--- a/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/rust/RustWriter.java
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/rust/RustWriter.java
@@ -136,12 +136,14 @@ public class RustWriter implements AutoCloseable {
         this.writerOuterAttributes(structStruct.attributes());
         this.writer.write("pub struct ");
         this.writeIdentifier(structStruct.name());
-        this.writer.write(" {");
 
-        if (!structStruct.fields().isEmpty()) {
+        if (structStruct.fields().isEmpty()) {
+            this.writer.write(";");
+        } else {
+            this.writer.write(" {");
             this.writer.indent();
 
-            for (var field : structStruct.fields()) {
+            for (var field : structStruct.fields().get()) {
                 this.writer.newLine();
                 this.writer.write("pub ");
                 this.writeIdentifier(field.name());
@@ -151,10 +153,9 @@ public class RustWriter implements AutoCloseable {
             }
 
             this.writer.dedent();
+            this.writer.newLine();
+            this.writer.write("}");
         }
-
-        this.writer.newLine();
-        this.writer.write("}");
     }
 
     // === Enumerations ===
diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/rust/ast/RustStructStruct.java b/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/rust/ast/RustStructStruct.java
index 4bc3a1e..2838a68 100644
--- a/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/rust/ast/RustStructStruct.java
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/rust/ast/RustStructStruct.java
@@ -8,17 +8,17 @@ package org.zwobble.hobgoblin.compiler.output.lang.rust.ast;
 public record RustStructStruct(
     java.util.List<org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustOuterAttribute> attributes,
     org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustIdentifier name,
-    java.util.List<org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructField> fields,
+    java.util.Optional<java.util.List<org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructField>> fields,
     org.zwobble.hobgoblin.compiler.ast.DocComment docComment
 ) implements org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustItem {
     public static org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStruct.Builder arbitrary() {
-        return new org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStruct.Builder(java.util.List.of(), org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustIdentifier.arbitrary().build(), java.util.List.of(), org.zwobble.hobgoblin.compiler.ast.HobgoblinNativeAst.arbitraryDocComment());
+        return new org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStruct.Builder(java.util.List.of(), org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustIdentifier.arbitrary().build(), java.util.Optional.empty(), org.zwobble.hobgoblin.compiler.ast.HobgoblinNativeAst.arbitraryDocComment());
     }
 
     public record Builder(
         java.util.List<org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustOuterAttribute> attributes,
         org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustIdentifier name,
-        java.util.List<org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructField> fields,
+        java.util.Optional<java.util.List<org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructField>> fields,
         org.zwobble.hobgoblin.compiler.ast.DocComment docComment
     ) implements org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustItem.Builder {
         public org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStruct build() {
@@ -49,20 +49,12 @@ public record RustStructStruct(
             return new org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStruct.Builder(attributes, name.build(), fields, docComment);
         }
 
-        public org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStruct.Builder withFields(java.util.List<org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructField> fields) {
-            return new org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStruct.Builder(attributes, name, fields, docComment);
-        }
-
-        public org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStruct.Builder addField(org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructField field) {
-            var fields = new java.util.ArrayList<org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructField>(this.fields);
-            fields.add(field);
+        public org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStruct.Builder withFields(java.util.Optional<java.util.List<org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructField>> fields) {
             return new org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStruct.Builder(attributes, name, fields, docComment);
         }
 
-        public org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStruct.Builder addField(org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructField.Builder field) {
-            var fields = new java.util.ArrayList<org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructField>(this.fields);
-            fields.add(field.build());
-            return new org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStruct.Builder(attributes, name, fields, docComment);
+        public org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStruct.Builder withFields(java.util.List<org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructField> fields) {
+            return new org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStruct.Builder(attributes, name, java.util.Optional.of(fields), docComment);
         }
 
         public org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStruct.Builder withDocComment(org.zwobble.hobgoblin.compiler.ast.DocComment docComment) {
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;
             """));
     }
 
@@ -112,8 +110,24 @@ 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);