From f20705b9d152a1656c7496e18fb0d69942d597a5 Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Fri, 12 Jun 2026 16:28:00 +0100
Subject: Introduce JavaTypeArg

---
 .../hobgoblin/compiler/output/lang/java/JavaWriter.java   |  6 +++++-
 .../compiler/output/lang/java/ast/JavaTypeArg.java        |  7 +++++++
 .../compiler/output/lang/java/ast/JavaTypeRef.java        | 15 +++++++++++----
 3 files changed, 23 insertions(+), 5 deletions(-)
 create mode 100644 src/main/java/org/zwobble/hobgoblin/compiler/output/lang/java/ast/JavaTypeArg.java

(limited to 'src/main/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 bcb2778..656636d 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
@@ -405,6 +405,10 @@ public class JavaWriter implements AutoCloseable {
         this.writer.write("\"");
     }
 
+    private static void writeTypeArg(JavaTypeArg arg, WriteString writer) throws IOException {
+        writeTypeRef(arg.type(), writer);
+    }
+
     void writeTypeRef(JavaTypeRef type) throws IOException {
         writeTypeRef(type, writer::write);
     }
@@ -425,7 +429,7 @@ public class JavaWriter implements AutoCloseable {
             writer.write("<");
             writeWithSeparator(
                 type.args(),
-                arg -> writeTypeRef(arg, writer),
+                arg -> writeTypeArg(arg, writer),
                 () -> writer.write(", ")
             );
             writer.write(">");
diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/java/ast/JavaTypeArg.java b/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/java/ast/JavaTypeArg.java
new file mode 100644
index 0000000..0d1b290
--- /dev/null
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/java/ast/JavaTypeArg.java
@@ -0,0 +1,7 @@
+package org.zwobble.hobgoblin.compiler.output.lang.java.ast;
+
+public record JavaTypeArg(JavaTypeRef type) {
+    public static JavaTypeArg invariant(JavaTypeRef type) {
+        return new JavaTypeArg(type);
+    }
+}
diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/java/ast/JavaTypeRef.java b/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/java/ast/JavaTypeRef.java
index 74dbbfb..55b8546 100644
--- a/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/java/ast/JavaTypeRef.java
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/output/lang/java/ast/JavaTypeRef.java
@@ -3,7 +3,7 @@ package org.zwobble.hobgoblin.compiler.output.lang.java.ast;
 import java.util.Arrays;
 import java.util.List;
 
-public record JavaTypeRef(List<String> packageName, List<String> typeNames, List<JavaTypeRef> args) {
+public record JavaTypeRef(List<String> packageName, List<String> typeNames, List<JavaTypeArg> args) {
     private static JavaTypeRef primitive(String name) {
         return new JavaTypeRef(List.of(), List.of(name), List.of());
     }
@@ -21,14 +21,17 @@ public record JavaTypeRef(List<String> packageName, List<String> typeNames, List
         String name,
         List<JavaTypeRef> args
     ) {
-        return new JavaTypeRef(packageName, List.of(name), args);
+        return generic(packageName, List.of(name), args);
     }
 
     public static JavaTypeRef generic(
         List<String> packageName,
         List<String> typeNames,
-        List<JavaTypeRef> args
+        List<JavaTypeRef> argTypes
     ) {
+        var args = argTypes.stream()
+            .map(arg -> JavaTypeArg.invariant(arg))
+            .toList();
         return new JavaTypeRef(packageName, typeNames, args);
     }
 
@@ -40,7 +43,11 @@ public record JavaTypeRef(List<String> packageName, List<String> typeNames, List
     public static final JavaTypeRef LIST = topLevel(List.of("java", "util"), "List");
 
     public static JavaTypeRef list(JavaTypeRef elementType) {
-        return new JavaTypeRef(LIST.packageName, LIST.typeNames, List.of(elementType));
+        return new JavaTypeRef(
+            LIST.packageName,
+            LIST.typeNames,
+            List.of(JavaTypeArg.invariant(elementType))
+        );
     }
 
     public static final JavaTypeRef OBJECT = topLevel(List.of("java", "lang"), "Object");
-- 
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