Implement type substitution for constructed types

2 files changed, 13 insertions, 3 deletions

diff --git a/src/main/java/org/shedlang/compiler/types/TypeSubstitution.java b/src/main/java/org/shedlang/compiler/types/TypeSubstitution.java
index 27111fd5..a6719d17 100644
--- a/src/main/java/org/shedlang/compiler/types/TypeSubstitution.java
+++ b/src/main/java/org/shedlang/compiler/types/TypeSubstitution.java
@@ -9,9 +9,12 @@ public class TypeSubstitution {
 
             case BottomType bottomType -> type;
 
-            case ConstructedType constructedType -> {
-                throw new UnsupportedOperationException("TODO");
-            }
+            case ConstructedType<?> constructedType -> new ConstructedType<>(
+                constructedType.constructor(),
+                constructedType.args().stream()
+                    .map(arg -> substitute(arg, map))
+                    .toList()
+            );
 
             case FunctionType functionType -> new FunctionType(
                 functionType.positionalParams().stream()
diff --git a/src/main/java/org/shedlang/compiler/types/Types.java b/src/main/java/org/shedlang/compiler/types/Types.java
index c3c25853..0e502249 100644
--- a/src/main/java/org/shedlang/compiler/types/Types.java
+++ b/src/main/java/org/shedlang/compiler/types/Types.java
@@ -49,6 +49,13 @@ public class Types {
         return new TypeConstructor<>(params, genericType);
     }
 
+    public static <T extends StructuredType> Type constructedType(
+        TypeConstructor<T> constructor,
+        List<Type> args
+    ) {
+        return new ConstructedType<>(constructor, args);
+    }
+
     public static Type commonSupertype(List<Type> subtypes) {
         var uniqueSubtypes = subtypes.stream()
             .filter(subtype -> subtype != Types.BOTTOM)