From ecd3bfddb74dee72b321992be26e3a7df670cfd9 Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Fri, 12 Jun 2026 18:03:27 +0100
Subject: Add method references to Java

---
 .../hobgoblin/compiler/output/lang/java/JavaWriter.java      | 10 ++++++++++
 .../compiler/output/lang/java/ast/JavaExpression.java        |  2 +-
 .../compiler/output/lang/java/ast/JavaMethodRef.java         |  4 ++++
 .../hobgoblin/compiler/output/lang/java/JavaWriterTests.java | 12 ++++++++++++
 4 files changed, 27 insertions(+), 1 deletion(-)
 create mode 100644 src/main/java/org/zwobble/hobgoblin/compiler/output/lang/java/ast/JavaMethodRef.java

diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/java/JavaWriter.java b/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/java/JavaWriter.java
index 6b5fd23..0299a31 100644
--- a/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/java/JavaWriter.java
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/java/JavaWriter.java
@@ -199,6 +199,10 @@ public class JavaWriter implements AutoCloseable {
                 writeMethodCall(methodCall);
             }
 
+            case JavaMethodRef methodRef -> {
+                writeMethodRef(methodRef);
+            }
+
             case JavaNewExpression newExpression -> {
                 writeNewExpression(newExpression);
             }
@@ -358,6 +362,12 @@ public class JavaWriter implements AutoCloseable {
         }
     }
 
+    private void writeMethodRef(JavaMethodRef methodRef) throws IOException {
+        this.writeTypeRef(methodRef.type());
+        this.writer.write("::");
+        this.writer.write(methodRef.methodName());
+    }
+
     private void writeNewExpression(JavaNewExpression newExpression) throws IOException {
         this.writer.write("new ");
         writeTypeRef(newExpression.type());
diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/java/ast/JavaExpression.java b/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/java/ast/JavaExpression.java
index f2d5f45..289b3e0 100644
--- a/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/java/ast/JavaExpression.java
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/java/ast/JavaExpression.java
@@ -1,4 +1,4 @@
 package org.zwobble.hobgoblin.compiler.output.lang.java.ast;
 
-public sealed interface JavaExpression permits JavaAssignment, JavaFieldAccess, JavaIntegerLiteral, JavaMethodCall, JavaNewExpression, JavaNullLiteral, JavaRef, JavaStaticFieldAccess, JavaStaticMethodCall, JavaStringLiteral {
+public sealed interface JavaExpression permits JavaAssignment, JavaFieldAccess, JavaIntegerLiteral, JavaMethodCall, JavaMethodRef, JavaNewExpression, JavaNullLiteral, JavaRef, JavaStaticFieldAccess, JavaStaticMethodCall, JavaStringLiteral {
 }
diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/java/ast/JavaMethodRef.java b/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/java/ast/JavaMethodRef.java
new file mode 100644
index 0000000..b100804
--- /dev/null
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/java/ast/JavaMethodRef.java
@@ -0,0 +1,4 @@
+package org.zwobble.hobgoblin.compiler.output.lang.java.ast;
+
+public record JavaMethodRef(JavaTypeRef type, String methodName) implements JavaExpression {
+}
diff --git a/src/test/java/org/zwobble/hobgoblin/compiler/output/lang/java/JavaWriterTests.java b/src/test/java/org/zwobble/hobgoblin/compiler/output/lang/java/JavaWriterTests.java
index 427d099..51e5f87 100644
--- a/src/test/java/org/zwobble/hobgoblin/compiler/output/lang/java/JavaWriterTests.java
+++ b/src/test/java/org/zwobble/hobgoblin/compiler/output/lang/java/JavaWriterTests.java
@@ -774,6 +774,18 @@ public class JavaWriterTests {
         assertThat(string, equalTo("one.Two.three"));
     }
 
+    @Test
+    public void referenceToMethodOnType() throws IOException {
+        var java = new JavaMethodRef(
+            JavaTypeRef.topLevel(List.of("one"), "Two"),
+            "three"
+        );
+
+        var string = write(writer -> writer.writeExpression(java));
+
+        assertThat(string, equalTo("one.Two::three"));
+    }
+
     @Test
     public void newExpression() throws IOException {
         var java = new JavaNewExpression(
-- 
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