Fix panic in checker

checker/checker.go

@@ -804,6 +804,9 @@ func (v *visitor) checkArguments(name string, fn reflect.Type, method bool, argu
 
 func (v *visitor) ClosureNode(node *ast.ClosureNode) (reflect.Type, info) {
 	t, _ := v.visit(node.Node)
+	if t == nil {
+		return v.error(node.Node, "closure cannot be nil")
+	}
 	return reflect.FuncOf([]reflect.Type{anyType}, []reflect.Type{t}, false), info{}
 }
 

compiler/compiler_test.go

@@ -283,6 +283,7 @@ func TestCompile(t *testing.T) {
 func TestCompile_panic(t *testing.T) {
 	tests := []string{
 		`(TotalPosts.Profile[Authors > TotalPosts == get(nil, TotalLikes)] > Authors) ^ (TotalLikes / (Posts?.PublishDate[TotalPosts] < Posts))`,
+		`one(Posts, nil)`,
 	}
 	for _, test := range tests {
 		t.Run(test, func(t *testing.T) {