add arg length check

src/frontend.rs

@@ -11,6 +11,7 @@ fn make_pubid(id: &str) -> String {
 #[derive(Debug)]
 pub enum CompileErrorKind {
     UndefinedReference(String),
+    BadArgCount{received: usize, expected: usize},
 }
 
 #[derive(Debug)]
@@ -83,6 +84,12 @@ fn lower_expression(
                     ))
                 })?;
 
+            if args_resolved.len() != callable.args.len() {
+                return Err(CompileError::new(CompileErrorKind::BadArgCount{
+                    expected: callable.args.len(), received: args_resolved.len()
+                }))
+            }
+
             let cell_id = module.make_genid(&callable.name);
 
             let cell = (*callable.instantiate)(&cell_id, args_resolved.as_slice(), &output_gen_id);