2 files changed, 12 insertions, 1 deletions
diff --git a/src/main/java/org/shedlang/compiler/types/SumType.java b/src/main/java/org/shedlang/compiler/types/SumType.java
new file mode 100644
index 00000000..8c293fca
--- /dev/null
+++ b/src/main/java/org/shedlang/compiler/types/SumType.java
@@ -0,0 +1,11 @@
+package org.shedlang.compiler.types;
+
+/**
+ * A discriminated union of several different types.
+ */
+public record SumType(NamespaceName namespaceName, String name) implements Type {
+    @Override
+    public String describe() {
+        return namespaceName.toString() + "." + name;
+    }
+}
diff --git a/src/main/java/org/shedlang/compiler/types/Type.java b/src/main/java/org/shedlang/compiler/types/Type.java
index b88cf42b..a1de4068 100644
--- a/src/main/java/org/shedlang/compiler/types/Type.java
+++ b/src/main/java/org/shedlang/compiler/types/Type.java
@@ -6,5 +6,5 @@ package org.shedlang.compiler.types;
  * found through auxiliary data.
  */
 public sealed interface Type extends TypeLevelValue
-    permits BoolType, BottomType, FunctionType, IntType, NamespaceType, StringType, StructType, TopType, TupleType, TypeLevelValueType, UnitType {
+    permits BoolType, BottomType, FunctionType, IntType, NamespaceType, StringType, StructType, SumType, TopType, TupleType, TypeLevelValueType, UnitType {
 }