util: Fix path truncation when the file name repeats in a parent dir

`PathWithPosition::parse_str` stripped the position suffix by searching
the whole path for the captured file name, so `foo/foo:10:2` was cut at
the first `foo` and parsed as `foo`. The same happened for
`main.rs-backup/src/main.rs:10:2`.

The captured file name is a slice of the last path component, so cut the
path right after it instead. Switching to `rsplit_once` would not work
either, since the last occurrence lands inside the position suffix for
numeric names like `1/1:1:1`.

Closes #64174

crates/util/src/paths.rs

@@ -662,8 +662,10 @@ impl PathWithPosition {
                 let row = maybe_row.parse::<u32>().ok();
                 let column = maybe_column.parse::<u32>().ok();
 
-                let (_, suffix) = trimmed.split_once(file_name).unwrap();
+                // `file_name` borrows from the last component of `trimmed`, so cut right after it
-                let path_without_suffix = &trimmed[..trimmed.len() - suffix.len()];
+                // instead of searching for its text, which may also appear in a parent directory.
+                let file_name_start = file_name.as_ptr() as usize - trimmed.as_ptr() as usize;
+                let path_without_suffix = &trimmed[..file_name_start + file_name.len()];
 
                 Self {
                     path: Path::new(path_without_suffix).to_path_buf(),
@@ -2512,6 +2514,54 @@ mod tests {
         );
     }
 
+    #[perf]
+    fn path_with_position_parse_file_name_repeated_in_path() {
+        assert_eq!(
+            PathWithPosition::parse_str("foo/foo:10:2"),
+            PathWithPosition {
+                path: PathBuf::from("foo/foo"),
+                row: Some(10),
+                column: Some(2),
+            }
+        );
+
+        assert_eq!(
+            PathWithPosition::parse_str("foo/foo(10,2)"),
+            PathWithPosition {
+                path: PathBuf::from("foo/foo"),
+                row: Some(10),
+                column: Some(2),
+            }
+        );
+
+        assert_eq!(
+            PathWithPosition::parse_str("main.rs-backup/src/main.rs:10:2"),
+            PathWithPosition {
+                path: PathBuf::from("main.rs-backup/src/main.rs"),
+                row: Some(10),
+                column: Some(2),
+            }
+        );
+
+        assert_eq!(
+            PathWithPosition::parse_str("1/1:1:1"),
+            PathWithPosition {
+                path: PathBuf::from("1/1"),
+                row: Some(1),
+                column: Some(1),
+            }
+        );
+
+        assert_eq!(
+            PathWithPosition::parse_str("日本/日本:3"),
+            PathWithPosition {
+                path: PathBuf::from("日本/日本"),
+                row: Some(3),
+                column: None,
+            }
+        );
+    }
+
     #[perf]
     #[cfg(target_os = "windows")]
     fn path_with_position_parse_windows_path() {