From 6cb75452ad193e1e40a092478ab527513a7e2bda Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Tue, 14 Jul 2026 19:39:31 +0100
Subject: Add attributes to Rust structs

---
 hobgoblin/src/output/lang/rust/ast.hob             |  7 ++++
 .../generators/rusttypes/RustTypesGenerator.java   |  2 +-
 .../compiler/output/lang/rust/RustWriter.java      | 16 +++++++++
 .../output/lang/rust/ast/RustOuterAttribute.java   | 32 ++++++++++++++++++
 .../output/lang/rust/ast/RustStructStruct.java     | 36 ++++++++++++++------
 .../compiler/output/lang/rust/RustWriterTests.java | 19 +++++++++++
 .../lang/rust/ast/RustOuterAttributeMatcher.java   | 39 ++++++++++++++++++++++
 .../lang/rust/ast/RustStructStructMatcher.java     |  6 ++++
 8 files changed, 146 insertions(+), 11 deletions(-)
 create mode 100644 src/main/java/org/zwobble/hobgoblin/compiler/output/lang/rust/ast/RustOuterAttribute.java
 create mode 100644 src/test/java/org/zwobble/hobgoblin/compiler/output/lang/rust/ast/RustOuterAttributeMatcher.java

diff --git a/hobgoblin/src/output/lang/rust/ast.hob b/hobgoblin/src/output/lang/rust/ast.hob
index 83b504c..c633b42 100644
--- a/hobgoblin/src/output/lang/rust/ast.hob
+++ b/hobgoblin/src/output/lang/rust/ast.hob
@@ -33,6 +33,7 @@ struct RustFunctionParam {
 // === Structs ===
 
 struct RustStructStruct {
+    field attributes: List[RustOuterAttribute];
     field name: RustIdentifier;
     field fields: List[RustStructField];
     field docComment: DocComment;
@@ -91,6 +92,12 @@ sum RustAssociatedItem {
     variant RustFunction;
 }
 
+// == Attributes ==
+
+struct RustOuterAttribute {
+    field path: RustTypePath;
+}
+
 // == Statements ==
 
 sum RustStatement {
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 aab7284..28926a3 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
@@ -123,7 +123,7 @@ public class RustTypesGenerator implements Generator {
             ))
             .toList();
 
-        var rustStruct = new RustStructStruct(rustStructName, rustFields, structDefinition.docComment());
+        var rustStruct = new RustStructStruct(List.of(), rustStructName, rustFields, structDefinition.docComment());
 
         return List.of(rustStruct);
     }
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 3d85056..581d08a 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
@@ -118,6 +118,7 @@ public class RustWriter implements AutoCloseable {
 
     private void writeStructStruct(RustStructStruct structStruct) throws IOException {
         this.writeDocComment(structStruct.docComment());
+        this.writerOuterAttributes(structStruct.attributes());
         this.writer.write("pub struct ");
         this.writeIdentifier(structStruct.name());
         this.writer.write(" {");
@@ -248,6 +249,21 @@ public class RustWriter implements AutoCloseable {
         }
     }
 
+    // == Attributes ==
+
+    private void writerOuterAttributes(List<RustOuterAttribute> attributes) throws IOException {
+        for (var attribute : attributes) {
+            writeOuterAttribute(attribute);
+        }
+    }
+
+    private void writeOuterAttribute(RustOuterAttribute attribute) throws IOException {
+        this.writer.write("#[");
+        this.writeTypePath(attribute.path());
+        this.writer.write("]");
+        this.writer.newLine();
+    }
+
     // == Statements ==
 
     void writeStatement(RustStatement statement) throws IOException {
diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/rust/ast/RustOuterAttribute.java b/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/rust/ast/RustOuterAttribute.java
new file mode 100644
index 0000000..862685a
--- /dev/null
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/rust/ast/RustOuterAttribute.java
@@ -0,0 +1,32 @@
+// Generated by hobgoblin.
+
+package org.zwobble.hobgoblin.compiler.output.lang.rust.ast;
+
+// Custom area start: org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustOuterAttribute imports
+// Custom area end: org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustOuterAttribute imports
+
+public record RustOuterAttribute(org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustTypePath path) {
+    public static org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustOuterAttribute.Builder arbitrary() {
+        return new org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustOuterAttribute.Builder(org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustTypePath.arbitrary().build());
+    }
+
+    public record Builder(org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustTypePath path) {
+        public org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustOuterAttribute build() {
+            return new org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustOuterAttribute(path);
+        }
+
+        public org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustOuterAttribute.Builder withPath(org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustTypePath path) {
+            return new org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustOuterAttribute.Builder(path);
+        }
+
+        public org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustOuterAttribute.Builder withPath(org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustTypePath.Builder path) {
+            return new org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustOuterAttribute.Builder(path.build());
+        }
+
+        // Custom area start: org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustOuterAttribute.Builder body
+        // Custom area end: org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustOuterAttribute.Builder body
+    }
+
+    // Custom area start: org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustOuterAttribute body
+    // Custom area end: org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustOuterAttribute body
+}
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 4eba76a..0bb57b7 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
@@ -5,42 +5,58 @@ package org.zwobble.hobgoblin.compiler.output.lang.rust.ast;
 // Custom area start: org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStruct imports
 // Custom area end: org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStruct imports
 
-public record RustStructStruct(org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustIdentifier name, 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 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, 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(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.List.of(), org.zwobble.hobgoblin.compiler.ast.HobgoblinNativeAst.arbitraryDocComment());
     }
 
-    public record Builder(org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustIdentifier name, 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 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, 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() {
-            return new org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStruct(name, fields, docComment);
+            return new org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStruct(attributes, name, fields, docComment);
+        }
+
+        public org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStruct.Builder withAttributes(java.util.List<org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustOuterAttribute> attributes) {
+            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 addAttribute(org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustOuterAttribute attribute) {
+            var attributes = new java.util.ArrayList<org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustOuterAttribute>(this.attributes);
+            attributes.add(attribute);
+            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 addAttribute(org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustOuterAttribute.Builder attribute) {
+            var attributes = new java.util.ArrayList<org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustOuterAttribute>(this.attributes);
+            attributes.add(attribute.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 withName(org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustIdentifier name) {
-            return new org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStruct.Builder(name, fields, docComment);
+            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 withName(org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustIdentifier.Builder name) {
-            return new org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStruct.Builder(name.build(), fields, docComment);
+            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(name, fields, docComment);
+            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);
-            return new org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStruct.Builder(name, fields, docComment);
+            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(name, fields, docComment);
+            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 withDocComment(org.zwobble.hobgoblin.compiler.ast.DocComment docComment) {
-            return new org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStruct.Builder(name, fields, docComment);
+            return new org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStruct.Builder(attributes, name, fields, docComment);
         }
 
         // Custom area start: org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStruct.Builder body
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 33fa490..b591058 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
@@ -109,6 +109,25 @@ public class RustWriterTests {
             }"""));
     }
 
+    @Test
+    public void structWithAttributes() throws IOException {
+        var rust = RustStructStruct.arbitrary()
+            .withName(new RustIdentifier("Rectangle"))
+            .withAttributes(List.of(
+                new RustOuterAttribute(RustTypePath.of("a", "b", "C")),
+                new RustOuterAttribute(RustTypePath.of("Debug"))
+            ))
+            .build();
+
+        var string = write(writer -> writer.writeItem(rust));
+
+        assertThat(string, equalTo("""
+            #[a::b::C]
+            #[Debug]
+            pub struct Rectangle {
+            }"""));
+    }
+
     @Test
     public void structWithFields() throws IOException {
         var rust = RustStructStruct.arbitrary()
diff --git a/src/test/java/org/zwobble/hobgoblin/compiler/output/lang/rust/ast/RustOuterAttributeMatcher.java b/src/test/java/org/zwobble/hobgoblin/compiler/output/lang/rust/ast/RustOuterAttributeMatcher.java
new file mode 100644
index 0000000..6e1e930
--- /dev/null
+++ b/src/test/java/org/zwobble/hobgoblin/compiler/output/lang/rust/ast/RustOuterAttributeMatcher.java
@@ -0,0 +1,39 @@
+// Generated by hobgoblin.
+
+package org.zwobble.hobgoblin.compiler.output.lang.rust.ast;
+
+// Custom area start: org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustOuterAttributeMatcher imports
+// Custom area end: org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustOuterAttributeMatcher imports
+
+public class RustOuterAttributeMatcher implements org.zwobble.precisely.Matcher<java.lang.Object> {
+    public static org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustOuterAttributeMatcher isRustOuterAttribute() {
+        return new org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustOuterAttributeMatcher(java.util.List.of());
+    }
+
+    private final java.util.List<org.zwobble.precisely.Matcher<? super org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustOuterAttribute>> submatchers;
+
+    private RustOuterAttributeMatcher(java.util.List<org.zwobble.precisely.Matcher<? super org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustOuterAttribute>> submatchers) {
+        this.submatchers = submatchers;
+    }
+
+    public org.zwobble.precisely.MatchResult match(java.lang.Object actual) {
+        return this.toMatcher().match(actual);
+    }
+
+    public org.zwobble.precisely.TextTree describe() {
+        return this.toMatcher().describe();
+    }
+
+    private org.zwobble.precisely.Matcher<java.lang.Object> toMatcher() {
+        return org.zwobble.precisely.Matchers.instanceOf(org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustOuterAttribute.class, this.submatchers);
+    }
+
+    public org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustOuterAttributeMatcher withPath(org.zwobble.precisely.Matcher<? super org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustTypePath> path) {
+        var submatchers = new java.util.ArrayList<org.zwobble.precisely.Matcher<? super org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustOuterAttribute>>(this.submatchers);
+        submatchers.add(org.zwobble.precisely.Matchers.has("path", org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustOuterAttribute::path, path));
+        return new org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustOuterAttributeMatcher(submatchers);
+    }
+
+    // Custom area start: org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustOuterAttributeMatcher body
+    // Custom area end: org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustOuterAttributeMatcher body
+}
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 0301dbb..4c4aa6a 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
@@ -28,6 +28,12 @@ public class RustStructStructMatcher implements org.zwobble.precisely.Matcher<ja
         return org.zwobble.precisely.Matchers.instanceOf(org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStruct.class, this.submatchers);
     }
 
+    public org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStructMatcher withAttributes(org.zwobble.precisely.Matcher<? super java.util.List<org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustOuterAttribute>> attributes) {
+        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("attributes", org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStruct::attributes, attributes));
+        return new org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStructMatcher(submatchers);
+    }
+
     public org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStructMatcher withName(org.zwobble.precisely.Matcher<? super org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustIdentifier> name) {
         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("name", org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustStructStruct::name, name));
-- 
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