$vasplat was allowed inside of a function when passed as an argument to a function.

releasenotes.md

@@ -47,6 +47,7 @@
 - `$defined` in a global scope should accept testing normal macros.
 - Assert on add to uninitialized ct variable #1765.
 - Dynamic function lookup fails after changing type without dummy anycast #1761
+- $vasplat was allowed inside of a function when passed as an argument to a function.
 
 ### Stdlib changes
 - Increase BitWriter.write_bits limit up to 32 bits.

src/compiler/sema_expr.c

@@ -1586,7 +1586,7 @@ INLINE bool sema_call_evaluate_arguments(SemaContext *context, CalledDecl *calle
 		Expr *arg = args[i];
 		if (i > 0) last = args[i - 1];
 		ASSERT0(expr_ok(arg));
-		if (arg->expr_kind == EXPR_VASPLAT)
+		if (arg->expr_kind == EXPR_VASPLAT && context->current_macro)
 		{
 			Expr **new_args = sema_vasplat_insert(context, args, arg, i);
 			if (!new_args) return false;

test/test_suite/macros/vasplat_function_call.c3

@@ -0,0 +1,18 @@
+import std;
+
+def IList = List(<int>);
+fn IList IList.new(...) @operator(construct)
+{
+  IList l;
+  l.new_init($vasplat); // #error: can only be used inside
+  return l;
+}
+
+
+fn void main()
+{
+  IList a = IList.new(123, 123, 123, 123, 123, 123, 123, 134);
+  a.push(567);
+
+  io::printfn("%s", a[0]);
+}