Check that receiver of type-level args is type constructor

2 files changed, 15 insertions, 2 deletions

diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/TypeChecker.java b/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/TypeChecker.java
index 9429313..eb47870 100644
--- a/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/TypeChecker.java
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/TypeChecker.java
@@ -393,8 +393,14 @@ public class TypeChecker {
         TypeCheckerNamespaceContext context
     ) {
         var typedReceiver = typeCheckTypeLevelExpression(untyped.receiver(), context);
-        // TODO: check this properly
-        var receiver = (TypeConstructor<?>) typedReceiver.value();
+
+        if (!(typedReceiver.value() instanceof TypeConstructor<?> receiver)) {
+            throw new UnexpectedTypeError(
+                new TypeSet.TypeConstructor(),
+                new TypeLevelValueType(typedReceiver.value()),
+                untyped.receiver().source()
+            );
+        }
 
         if (untyped.args().size() != receiver.params().size()) {
             throw new WrongNumberOfTypeLevelArgsError(
diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/types/TypeSet.java b/src/main/java/org/zwobble/hobgoblin/compiler/types/TypeSet.java
index f587897..c3896d9 100644
--- a/src/main/java/org/zwobble/hobgoblin/compiler/types/TypeSet.java
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/types/TypeSet.java
@@ -16,4 +16,11 @@ public sealed interface TypeSet {
             return "metatype";
         }
     }
+
+    record TypeConstructor() implements TypeSet {
+        @Override
+        public String describe() {
+            return "type constructor";
+        }
+    }
 }