Extract isVariantSubtype()

1 files changed, 15 insertions, 6 deletions

diff --git a/src/main/java/org/shedlang/compiler/typechecker/TypeCheckerSubTyping.java b/src/main/java/org/shedlang/compiler/typechecker/TypeCheckerSubTyping.java
index 49560f38..8e0fb017 100644
--- a/src/main/java/org/shedlang/compiler/typechecker/TypeCheckerSubTyping.java
+++ b/src/main/java/org/shedlang/compiler/typechecker/TypeCheckerSubTyping.java
@@ -24,18 +24,18 @@ public class TypeCheckerSubTyping {
 
         if (supertype instanceof SumType supertypeSum) {
             var superTypeInfo = context.sumTypeInfo(supertypeSum, Sources.NULL);
-            return superTypeInfo.variants().stream()
-                .anyMatch(supertypeVariant -> isSubType(subtype, supertypeVariant.type(), context));
+            return isVariantSubtype(subtype, superTypeInfo, context);
         }
 
         if (
             supertype instanceof ConstructedType<?> supertypeConstructedType &&
             supertypeConstructedType.genericType() instanceof SumType
         ) {
-            // TODO: merge with logic for plain sum types
-            var superTypeInfo = context.sumTypeInfo((ConstructedType<SumType>) supertypeConstructedType, Sources.NULL);
-            return superTypeInfo.variants().stream()
-                .anyMatch(supertypeVariant -> isSubType(subtype, supertypeVariant.type(), context));
+            var superTypeInfo = context.sumTypeInfo(
+                (ConstructedType<SumType>) supertypeConstructedType,
+                Sources.NULL
+            );
+            return isVariantSubtype(subtype, superTypeInfo, context);
         }
 
         if (
@@ -85,6 +85,15 @@ public class TypeCheckerSubTyping {
         return false;
     }
 
+    private static boolean isVariantSubtype(
+        Type subtype,
+        SumTypeInfo superTypeInfo,
+        TypeCheckerContext context
+    ) {
+        return superTypeInfo.variants().stream()
+            .anyMatch(supertypeVariant -> isSubType(subtype, supertypeVariant.type(), context));
+    }
+
     static boolean isSubEffect(Effect subEffect, Effect superEffect, TypeCheckerContext context) {
         if (subEffect == Effects.NONE) {
             return true;