From 45022f09c44fbbd1683cac279ccf53f9ea650446 Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Fri, 26 Jun 2026 11:39:51 +0100
Subject: Check variant field types

---
 .../hobgoblin/compiler/typechecker/TypeChecker.java     | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

(limited to 'src/main')

diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/TypeChecker.java b/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/TypeChecker.java
index c6f8721..408a0b2 100644
--- a/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/TypeChecker.java
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/TypeChecker.java
@@ -313,6 +313,9 @@ public class TypeChecker {
                 // TODO: set source appropriately.
                 throw new SubtypeIsMissingFieldError(sumType, variantType, sumTypeField.name(), NullSource.INSTANCE);
             }
+
+            // TODO: set source appropriately.
+            checkIsSubtype(variantTypeField.get().type(), sumTypeField.type(), NullSource.INSTANCE);
         }
     }
 
@@ -385,4 +388,18 @@ public class TypeChecker {
 
         return value;
     }
+
+    private static void checkIsSubtype(Type subtype, Type supertype, Source source) {
+        if (!isSubtype(subtype, supertype)) {
+            throw new UnexpectedTypeError(
+                new TypeSet.SingleType(supertype),
+                subtype,
+                source
+            );
+        }
+    }
+
+    private static boolean isSubtype(Type subtype, Type supertype) {
+        return subtype.equals(supertype);
+    }
 }
-- 
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