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diff --git a/src/tools/rust-analyzer/crates/vfs/src/anchored_path.rs b/src/tools/rust-analyzer/crates/vfs/src/anchored_path.rs
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+++ b/src/tools/rust-analyzer/crates/vfs/src/anchored_path.rs
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+//! Analysis-level representation of file-system paths.
+//!
+//! The primary goal of this is to losslessly represent paths like
+//!
+//! ```
+//! #[path = "./bar.rs"]
+//! mod foo;
+//! ```
+//!
+//! The first approach one might reach for is to use `PathBuf`. The problem here
+//! is that `PathBuf` depends on host target (windows or linux), but
+//! rust-analyzer should be capable to process `#[path = r"C:\bar.rs"]` on Unix.
+//!
+//! The second try is to use a `String`. This also fails, however. Consider a
+//! hypothetical scenario, where rust-analyzer operates in a
+//! networked/distributed mode. There's one global instance of rust-analyzer,
+//! which processes requests from different machines. Now, the semantics of
+//! `#[path = "/abs/path.rs"]` actually depends on which file-system we are at!
+//! That is, even absolute paths exist relative to a file system!
+//!
+//! A more realistic scenario here is virtual VFS paths we use for testing. More
+//! generally, there can be separate "universes" of VFS paths.
+//!
+//! That's why we use anchored representation -- each path carries an info about
+//! a file this path originates from. We can fetch fs/"universe" information
+//! from the anchor than.
+use crate::FileId;
+
+/// Path relative to a file.
+///
+/// Owned version of [`AnchoredPath`].
+#[derive(Clone, PartialEq, Eq, Debug)]
+pub struct AnchoredPathBuf {
+    /// File that this path is relative to.
+    pub anchor: FileId,
+    /// Path relative to `anchor`'s containing directory.
+    pub path: String,
+}
+
+/// Path relative to a file.
+///
+/// Borrowed version of [`AnchoredPathBuf`].
+#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+pub struct AnchoredPath<'a> {
+    /// File that this path is relative to.
+    pub anchor: FileId,
+    /// Path relative to `anchor`'s containing directory.
+    pub path: &'a str,
+}