From f5ba39cf70de72ae727c23df49b842a608dd4aaf Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Sat, 13 Jan 2024 17:31:04 +0000
Subject: Add TypeInfos.subtypes()

---
 .../java/org/shedlang/compiler/typechecker/TypeInfos.java | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

(limited to 'src/main/java')

diff --git a/src/main/java/org/shedlang/compiler/typechecker/TypeInfos.java b/src/main/java/org/shedlang/compiler/typechecker/TypeInfos.java
index 22f68b38..4547c895 100644
--- a/src/main/java/org/shedlang/compiler/typechecker/TypeInfos.java
+++ b/src/main/java/org/shedlang/compiler/typechecker/TypeInfos.java
@@ -145,6 +145,21 @@ public class TypeInfos {
         return supertypes;
     }
 
+    /**
+     * Get the subtypes of a type, from most specific to least specific.
+     */
+    public Set<Type> subtypes(Type type) {
+        var subtypes = P.orderedSet(type);
+        if (type instanceof SumType sumType) {
+            var sumTypeInfo = sumTypeInfo(sumType);
+            subtypes = subtypes.plusAll(
+                sumTypeInfo.orElseThrow().variants()
+            );
+        }
+        subtypes = subtypes.plus(Types.BOTTOM);
+        return subtypes;
+    }
+
     private Optional<SumTypeInfo> simpleSumTypeInfo(SimpleSumType type) {
         return Optional.ofNullable(sumTypeInfos.get(type));
     }
-- 
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