Temporarily fix rust-lang/rust#89658

src/windows.rs

@@ -143,11 +143,27 @@ fn get_prefix(base: &BasePath) -> PrefixComponent<'_> {
 }
 
 fn push_separator(base: &mut BasePathBuf) {
+    // https://github.com/rust-lang/rust/issues/89658
+    /*
     base.replace_with(|mut base| {
         // Add a separator if necessary.
         base.push("");
         base
     });
+    */
+
+    const SEPARATOR: &str = "\\";
+
+    if let Some(Component::Prefix(prefix)) = base.components().next_back() {
+        if matches!(prefix.kind(), Prefix::Disk(_) | Prefix::VerbatimDisk(_)) {
+            return;
+        }
+    }
+    // This inefficient implementation must be used until the above issue is
+    // resolved.
+    if !base.0.to_string_lossy().ends_with(SEPARATOR) {
+        base.0.push(SEPARATOR);
+    }
 }
 
 pub(super) fn push(base: &mut BasePathBuf, initial_path: &Path) {

tests/edge_cases.rs

@@ -0,0 +1,21 @@
+mod common;
+
+#[cfg(windows)]
+#[test]
+fn test_edge_cases() {
+    use std::path::Path;
+
+    use normpath::BasePath;
+    use normpath::PathExt;
+
+    // https://github.com/dylni/normpath/pull/4#issuecomment-938596259
+    tj(r"X:\X:", r"ABC", r"X:\X:\ABC");
+    tj(r"\\?\X:\X:", r"ABC", r"\\?\X:\X:\ABC");
+
+    #[rustversion::attr(since(1.46.0), track_caller)]
+    fn tj(base: &str, path: &str, joined_path: &str) {
+        let joined_path = Path::new(joined_path);
+        assert_eq!(joined_path, BasePath::try_new(base).unwrap().join(path));
+        common::assert_eq(joined_path, joined_path.normalize_virtually());
+    }
+}