From a17c1e5fcbb159d9c6ef84058d8d10ae9567ffc8 Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Sun, 2 Aug 2026 14:03:46 +0100
Subject: Check number of type-level args

---
 .../compiler/typechecker/TypeChecker.java          | 11 +++++++++--
 .../errors/WrongNumberOfTypeLevelArgsError.java    | 23 ++++++++++++++++++++++
 2 files changed, 32 insertions(+), 2 deletions(-)
 create mode 100644 src/main/java/org/zwobble/hobgoblin/compiler/typechecker/errors/WrongNumberOfTypeLevelArgsError.java

(limited to 'src/main/java')

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 a12677e..2d496e5 100644
--- a/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/TypeChecker.java
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/TypeChecker.java
@@ -393,14 +393,21 @@ public class TypeChecker {
         TypeCheckerNamespaceContext context
     ) {
         var typedReceiver = typeCheckTypeLevelExpression(untyped.receiver(), context);
+        // TODO: check this properly
         var receiver = (TypeConstructor<SimpleNativeType>) typedReceiver.value();
 
+        if (untyped.args().size() != receiver.params().size()) {
+            throw new WrongNumberOfTypeLevelArgsError(
+                receiver.params().size(),
+                untyped.args().size(),
+                untyped.source()
+            );
+        }
+
         var args = untyped.args().stream()
             .map(untypedArg -> typeCheckMetaType(untypedArg, context).value())
             .toList();
 
-        // TODO: check number of args
-
         var constructedType = new ConstructedNativeType(receiver, args);
 
         return new TypedConstructedTypeNode(
diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/errors/WrongNumberOfTypeLevelArgsError.java b/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/errors/WrongNumberOfTypeLevelArgsError.java
new file mode 100644
index 0000000..86f57f2
--- /dev/null
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/errors/WrongNumberOfTypeLevelArgsError.java
@@ -0,0 +1,23 @@
+package org.zwobble.hobgoblin.compiler.typechecker.errors;
+
+import org.zwobble.hobgoblin.compiler.errors.SourceError;
+import org.zwobble.hobgoblin.compiler.sources.Source;
+
+public class WrongNumberOfTypeLevelArgsError extends SourceError {
+    private final int expectedArgCount;
+    private final int actualArgCount;
+
+    public WrongNumberOfTypeLevelArgsError(int expectedArgCount, int actualArgCount, Source source) {
+        super("expected " + expectedArgCount + " type-level args, but got " + actualArgCount, source);
+        this.expectedArgCount = expectedArgCount;
+        this.actualArgCount = actualArgCount;
+    }
+
+    public int expectedArgCount() {
+        return expectedArgCount;
+    }
+
+    public int actualArgCount() {
+        return actualArgCount;
+    }
+}
-- 
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