Check call receiver is a function

2 files changed, 10 insertions, 1 deletions

diff --git a/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java b/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
index 83285f07..e89bdd61 100644
--- a/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
+++ b/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
@@ -74,7 +74,14 @@ public class TypeChecker {
         TypeCheckerContext context
     ) {
         var typedReceiver = typeCheckExpression(untyped.receiver(), context);
-        var receiverType = (FunctionType) typedReceiver.type();
+
+        if (!(typedReceiver.type() instanceof FunctionType receiverType)) {
+            throw new UnexpectedTypeError(
+                TypeSets.FUNCTION,
+                typedReceiver.type(),
+                typedReceiver.source()
+            );
+        }
 
         return new TypedCallNode(
             typedReceiver,
diff --git a/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSets.java b/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSets.java
index 4f5f1848..b783a5ef 100644
--- a/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSets.java
+++ b/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSets.java
@@ -6,6 +6,8 @@ public class TypeSets {
     private TypeSets() {
     }
 
+    public static final TypeSet FUNCTION = TypeSetFunction.INSTANCE;
+
     public static TypeSet type(Type type) {
         return new TypeSetType(type);
     }