From 2d3d2c5f27a38c25e6d697c8635c38655f1a9728 Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Sun, 7 Jan 2024 18:05:55 +0000
Subject: Update commonSupertype to handle supertype of sum and its variants

---
 .../compiler/types/CommonSupertypeTests.java       | 25 ++++++++++++++++++++++
 1 file changed, 25 insertions(+)

(limited to 'src/test/java')

diff --git a/src/test/java/org/shedlang/compiler/types/CommonSupertypeTests.java b/src/test/java/org/shedlang/compiler/types/CommonSupertypeTests.java
index 1b9873a6..fb9a14c5 100644
--- a/src/test/java/org/shedlang/compiler/types/CommonSupertypeTests.java
+++ b/src/test/java/org/shedlang/compiler/types/CommonSupertypeTests.java
@@ -83,4 +83,29 @@ public class CommonSupertypeTests {
 
         assertThat(result, equalTo(sumType));
     }
+
+    @Test
+    public void commonSupertypeOfSumTypeAndVariantOfThatSumTypeIsThatSumType() {
+        var namespaceName = NamespaceName.of("Example");
+        var variantType1 = Types.struct(namespaceName, "Variant1");
+        var variantType2 = Types.struct(namespaceName, "Variant2");
+        var sumType = Types.sum(namespaceName, "Sum");
+        var typeInfos = TypeInfos.EMPTY
+            .addSumTypeInfo(sumType, new SumTypeInfo(P.orderedSet(
+                variantType1,
+                variantType2
+            )));
+
+        var result1 = Types.commonSupertype(
+            List.of(sumType, variantType2),
+            typeInfos
+        );
+        var result2 = Types.commonSupertype(
+            List.of(variantType2, sumType),
+            typeInfos
+        );
+
+        assertThat(result1, equalTo(sumType));
+        assertThat(result2, equalTo(sumType));
+    }
 }
-- 
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