handle fully qualified paths properly when linting

fixes #50970

src/test/ui/rust-2018/edition-lint-nested-empty-paths.rs

@@ -0,0 +1,40 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// run-rustfix
+
+#![feature(rust_2018_preview)]
+#![deny(absolute_path_not_starting_with_crate)]
+#![allow(unused_imports)]
+#![allow(dead_code)]
+
+crate mod foo {
+    crate mod bar {
+        crate mod baz { }
+        crate mod baz1 { }
+
+        crate struct XX;
+    }
+}
+
+use foo::{bar::{baz::{}}};
+//~^ ERROR absolute paths must start with
+//~| WARN this was previously accepted
+
+use foo::{bar::{XX, baz::{}}};
+//~^ ERROR absolute paths must start with
+//~| WARN this was previously accepted
+
+use foo::{bar::{baz::{}, baz1::{}}};
+//~^ ERROR absolute paths must start with
+//~| WARN this was previously accepted
+
+fn main() {
+}