16 files changed, 130 insertions, 72 deletions

diff --git a/crates/base_db/src/lib.rs b/crates/base_db/src/lib.rs
index 5571af495..595f28ada 100644
--- a/crates/base_db/src/lib.rs
+++ b/crates/base_db/src/lib.rs
@@ -18,7 +18,7 @@ pub use crate::{
     },
 };
 pub use salsa;
-pub use vfs::{file_set::FileSet, FileId, VfsPath};
+pub use vfs::{file_set::FileSet, AnchoredPath, AnchoredPathBuf, FileId, VfsPath};
 
 #[macro_export]
 macro_rules! impl_intern_key {
@@ -91,12 +91,7 @@ pub const DEFAULT_LRU_CAP: usize = 128;
 pub trait FileLoader {
     /// Text of the file.
     fn file_text(&self, file_id: FileId) -> Arc<String>;
-    /// Note that we intentionally accept a `&str` and not a `&Path` here. This
-    /// method exists to handle `#[path = "/some/path.rs"] mod foo;` and such,
-    /// so the input is guaranteed to be utf-8 string. One might be tempted to
-    /// introduce some kind of "utf-8 path with / separators", but that's a bad idea. Behold
-    /// `#[path = "C://no/way"]`
-    fn resolve_path(&self, anchor: FileId, path: &str) -> Option<FileId>;
+    fn resolve_path(&self, path: AnchoredPath) -> Option<FileId>;
     fn relevant_crates(&self, file_id: FileId) -> Arc<FxHashSet<CrateId>>;
 }
 
@@ -155,11 +150,11 @@ impl<T: SourceDatabaseExt> FileLoader for FileLoaderDelegate<&'_ T> {
     fn file_text(&self, file_id: FileId) -> Arc<String> {
         SourceDatabaseExt::file_text(self.0, file_id)
     }
-    fn resolve_path(&self, anchor: FileId, path: &str) -> Option<FileId> {
+    fn resolve_path(&self, path: AnchoredPath) -> Option<FileId> {
         // FIXME: this *somehow* should be platform agnostic...
-        let source_root = self.0.file_source_root(anchor);
+        let source_root = self.0.file_source_root(path.anchor);
         let source_root = self.0.source_root(source_root);
-        source_root.file_set.resolve_path(anchor, path)
+        source_root.file_set.resolve_path(path)
     }
 
     fn relevant_crates(&self, file_id: FileId) -> Arc<FxHashSet<CrateId>> {
diff --git a/crates/hir_def/src/nameres/mod_resolution.rs b/crates/hir_def/src/nameres/mod_resolution.rs
index c0c789cae..b4ccd4488 100644
--- a/crates/hir_def/src/nameres/mod_resolution.rs
+++ b/crates/hir_def/src/nameres/mod_resolution.rs
@@ -1,5 +1,5 @@
 //! This module resolves `mod foo;` declaration to file.
-use base_db::FileId;
+use base_db::{AnchoredPath, FileId};
 use hir_expand::name::Name;
 use syntax::SmolStr;
 use test_utils::mark;
@@ -77,7 +77,8 @@ impl ModDir {
         };
 
         for candidate in candidate_files.iter() {
-            if let Some(file_id) = db.resolve_path(file_id, candidate.as_str()) {
+            let path = AnchoredPath { anchor: file_id, path: candidate.as_str() };
+            if let Some(file_id) = db.resolve_path(path) {
                 let is_mod_rs = candidate.ends_with("mod.rs");
 
                 let (dir_path, root_non_dir_owner) = if is_mod_rs || attr_path.is_some() {
diff --git a/crates/hir_def/src/test_db.rs b/crates/hir_def/src/test_db.rs
index f8b150850..574c0201a 100644
--- a/crates/hir_def/src/test_db.rs
+++ b/crates/hir_def/src/test_db.rs
@@ -5,8 +5,8 @@ use std::{
     sync::{Arc, Mutex},
 };
 
-use base_db::SourceDatabase;
 use base_db::{salsa, CrateId, FileId, FileLoader, FileLoaderDelegate, Upcast};
+use base_db::{AnchoredPath, SourceDatabase};
 use hir_expand::db::AstDatabase;
 use hir_expand::diagnostics::Diagnostic;
 use hir_expand::diagnostics::DiagnosticSinkBuilder;
@@ -63,8 +63,8 @@ impl FileLoader for TestDB {
     fn file_text(&self, file_id: FileId) -> Arc<String> {
         FileLoaderDelegate(self).file_text(file_id)
     }
-    fn resolve_path(&self, anchor: FileId, path: &str) -> Option<FileId> {
-        FileLoaderDelegate(self).resolve_path(anchor, path)
+    fn resolve_path(&self, path: AnchoredPath) -> Option<FileId> {
+        FileLoaderDelegate(self).resolve_path(path)
     }
     fn relevant_crates(&self, file_id: FileId) -> Arc<FxHashSet<CrateId>> {
         FileLoaderDelegate(self).relevant_crates(file_id)
diff --git a/crates/hir_expand/src/builtin_macro.rs b/crates/hir_expand/src/builtin_macro.rs
index 79b970850..f60666a54 100644
--- a/crates/hir_expand/src/builtin_macro.rs
+++ b/crates/hir_expand/src/builtin_macro.rs
@@ -4,7 +4,7 @@ use crate::{
     MacroDefId, MacroDefKind, TextSize,
 };
 
-use base_db::FileId;
+use base_db::{AnchoredPath, FileId};
 use either::Either;
 use mbe::{parse_to_token_tree, ExpandResult};
 use parser::FragmentKind;
@@ -324,7 +324,8 @@ fn relative_file(
     allow_recursion: bool,
 ) -> Option<FileId> {
     let call_site = call_id.as_file().original_file(db);
-    let res = db.resolve_path(call_site, path)?;
+    let path = AnchoredPath { anchor: call_site, path };
+    let res = db.resolve_path(path)?;
     // Prevent include itself
     if res == call_site && !allow_recursion {
         None
diff --git a/crates/hir_expand/src/test_db.rs b/crates/hir_expand/src/test_db.rs
index fca501e1f..7168a9462 100644
--- a/crates/hir_expand/src/test_db.rs
+++ b/crates/hir_expand/src/test_db.rs
@@ -5,7 +5,7 @@ use std::{
     sync::{Arc, Mutex},
 };
 
-use base_db::{salsa, CrateId, FileId, FileLoader, FileLoaderDelegate};
+use base_db::{salsa, AnchoredPath, CrateId, FileId, FileLoader, FileLoaderDelegate};
 use rustc_hash::FxHashSet;
 
 #[salsa::database(
@@ -40,8 +40,8 @@ impl FileLoader for TestDB {
     fn file_text(&self, file_id: FileId) -> Arc<String> {
         FileLoaderDelegate(self).file_text(file_id)
     }
-    fn resolve_path(&self, anchor: FileId, path: &str) -> Option<FileId> {
-        FileLoaderDelegate(self).resolve_path(anchor, path)
+    fn resolve_path(&self, path: AnchoredPath) -> Option<FileId> {
+        FileLoaderDelegate(self).resolve_path(path)
     }
     fn relevant_crates(&self, file_id: FileId) -> Arc<FxHashSet<CrateId>> {
         FileLoaderDelegate(self).relevant_crates(file_id)
diff --git a/crates/hir_ty/src/test_db.rs b/crates/hir_ty/src/test_db.rs
index 22254b765..646e16bbe 100644
--- a/crates/hir_ty/src/test_db.rs
+++ b/crates/hir_ty/src/test_db.rs
@@ -5,7 +5,9 @@ use std::{
     sync::{Arc, Mutex},
 };
 
-use base_db::{salsa, CrateId, FileId, FileLoader, FileLoaderDelegate, SourceDatabase, Upcast};
+use base_db::{
+    salsa, AnchoredPath, CrateId, FileId, FileLoader, FileLoaderDelegate, SourceDatabase, Upcast,
+};
 use hir_def::{db::DefDatabase, ModuleId};
 use hir_expand::db::AstDatabase;
 use rustc_hash::{FxHashMap, FxHashSet};
@@ -67,8 +69,8 @@ impl FileLoader for TestDB {
     fn file_text(&self, file_id: FileId) -> Arc<String> {
         FileLoaderDelegate(self).file_text(file_id)
     }
-    fn resolve_path(&self, anchor: FileId, path: &str) -> Option<FileId> {
-        FileLoaderDelegate(self).resolve_path(anchor, path)
+    fn resolve_path(&self, path: AnchoredPath) -> Option<FileId> {
+        FileLoaderDelegate(self).resolve_path(path)
     }
     fn relevant_crates(&self, file_id: FileId) -> Arc<FxHashSet<CrateId>> {
         FileLoaderDelegate(self).relevant_crates(file_id)
diff --git a/crates/ide/src/diagnostics.rs b/crates/ide/src/diagnostics.rs
index c8453edb3..d09f3a0a1 100644
--- a/crates/ide/src/diagnostics.rs
+++ b/crates/ide/src/diagnostics.rs
@@ -610,10 +610,12 @@ fn test_fn() {
                                     source_file_edits: [],
                                     file_system_edits: [
                                         CreateFile {
-                                            anchor: FileId(
-                                                0,
-                                            ),
-                                            dst: "foo.rs",
+                                            dst: AnchoredPathBuf {
+                                                anchor: FileId(
+                                                    0,
+                                                ),
+                                                path: "foo.rs",
+                                            },
                                         },
                                     ],
                                     is_snippet: false,
diff --git a/crates/ide/src/diagnostics/fixes.rs b/crates/ide/src/diagnostics/fixes.rs
index 24d08651e..29c7a040b 100644
--- a/crates/ide/src/diagnostics/fixes.rs
+++ b/crates/ide/src/diagnostics/fixes.rs
@@ -8,7 +8,7 @@ use hir::{
     },
     HasSource, HirDisplay, Semantics, VariantDef,
 };
-use ide_db::base_db::FileId;
+use ide_db::base_db::{AnchoredPathBuf, FileId};
 use ide_db::{
     source_change::{FileSystemEdit, SourceFileEdit},
     RootDatabase,
@@ -36,8 +36,10 @@ impl DiagnosticWithFix for UnresolvedModule {
         Some(Fix::new(
             "Create module",
             FileSystemEdit::CreateFile {
-                anchor: self.file.original_file(sema.db),
-                dst: self.candidate.clone(),
+                dst: AnchoredPathBuf {
+                    anchor: self.file.original_file(sema.db),
+                    path: self.candidate.clone(),
+                },
             }
             .into(),
             unresolved_module.syntax().text_range(),
diff --git a/crates/ide/src/references/rename.rs b/crates/ide/src/references/rename.rs
index 64fe8bd65..44081f210 100644
--- a/crates/ide/src/references/rename.rs
+++ b/crates/ide/src/references/rename.rs
@@ -6,7 +6,7 @@ use std::{
 };
 
 use hir::{Module, ModuleDef, ModuleSource, Semantics};
-use ide_db::base_db::{FileRange, SourceDatabaseExt};
+use ide_db::base_db::{AnchoredPathBuf, FileRange, SourceDatabaseExt};
 use ide_db::{
     defs::{Definition, NameClass, NameRefClass},
     RootDatabase,
@@ -182,12 +182,13 @@ fn rename_mod(
     match src.value {
         ModuleSource::SourceFile(..) => {
             // mod is defined in path/to/dir/mod.rs
-            let dst = if module.is_mod_rs(sema.db) {
+            let path = if module.is_mod_rs(sema.db) {
                 format!("../{}/mod.rs", new_name)
             } else {
                 format!("{}.rs", new_name)
             };
-            let move_file = FileSystemEdit::MoveFile { src: file_id, anchor: file_id, dst };
+            let dst = AnchoredPathBuf { anchor: file_id, path };
+            let move_file = FileSystemEdit::MoveFile { src: file_id, dst };
             file_system_edits.push(move_file);
         }
         ModuleSource::Module(..) => {}
@@ -771,10 +772,12 @@ mod foo<|>;
                                 src: FileId(
                                     2,
                                 ),
-                                anchor: FileId(
-                                    2,
-                                ),
-                                dst: "foo2.rs",
+                                dst: AnchoredPathBuf {
+                                    anchor: FileId(
+                                        2,
+                                    ),
+                                    path: "foo2.rs",
+                                },
                             },
                         ],
                         is_snippet: false,
@@ -837,10 +840,12 @@ use crate::foo<|>::FooContent;
                                 src: FileId(
                                     1,
                                 ),
-                                anchor: FileId(
-                                    1,
-                                ),
-                                dst: "quux.rs",
+                                dst: AnchoredPathBuf {
+                                    anchor: FileId(
+                                        1,
+                                    ),
+                                    path: "quux.rs",
+                                },
                             },
                         ],
                         is_snippet: false,
@@ -884,10 +889,12 @@ mod fo<|>o;
                                 src: FileId(
                                     1,
                                 ),
-                                anchor: FileId(
-                                    1,
-                                ),
-                                dst: "../foo2/mod.rs",
+                                dst: AnchoredPathBuf {
+                                    anchor: FileId(
+                                        1,
+                                    ),
+                                    path: "../foo2/mod.rs",
+                                },
                             },
                         ],
                         is_snippet: false,
@@ -932,10 +939,12 @@ mod outer { mod fo<|>o; }
                                 src: FileId(
                                     1,
                                 ),
-                                anchor: FileId(
-                                    1,
-                                ),
-                                dst: "bar.rs",
+                                dst: AnchoredPathBuf {
+                                    anchor: FileId(
+                                        1,
+                                    ),
+                                    path: "bar.rs",
+                                },
                             },
                         ],
                         is_snippet: false,
@@ -1016,10 +1025,12 @@ pub mod foo<|>;
                                 src: FileId(
                                     2,
                                 ),
-                                anchor: FileId(
-                                    2,
-                                ),
-                                dst: "foo2.rs",
+                                dst: AnchoredPathBuf {
+                                    anchor: FileId(
+                                        2,
+                                    ),
+                                    path: "foo2.rs",
+                                },
                             },
                         ],
                         is_snippet: false,
diff --git a/crates/ide_db/src/lib.rs b/crates/ide_db/src/lib.rs
index fceaa089a..118c090d7 100644
--- a/crates/ide_db/src/lib.rs
+++ b/crates/ide_db/src/lib.rs
@@ -19,8 +19,8 @@ use std::{fmt, sync::Arc};
 
 use base_db::{
     salsa::{self, Durability},
-    Canceled, CheckCanceled, CrateId, FileId, FileLoader, FileLoaderDelegate, SourceDatabase,
-    Upcast,
+    AnchoredPath, Canceled, CheckCanceled, CrateId, FileId, FileLoader, FileLoaderDelegate,
+    SourceDatabase, Upcast,
 };
 use hir::db::{AstDatabase, DefDatabase, HirDatabase};
 use rustc_hash::FxHashSet;
@@ -72,8 +72,8 @@ impl FileLoader for RootDatabase {
     fn file_text(&self, file_id: FileId) -> Arc<String> {
         FileLoaderDelegate(self).file_text(file_id)
     }
-    fn resolve_path(&self, anchor: FileId, path: &str) -> Option<FileId> {
-        FileLoaderDelegate(self).resolve_path(anchor, path)
+    fn resolve_path(&self, path: AnchoredPath) -> Option<FileId> {
+        FileLoaderDelegate(self).resolve_path(path)
     }
     fn relevant_crates(&self, file_id: FileId) -> Arc<FxHashSet<CrateId>> {
         FileLoaderDelegate(self).relevant_crates(file_id)
diff --git a/crates/ide_db/src/source_change.rs b/crates/ide_db/src/source_change.rs
index f1590ec66..e87d98dad 100644
--- a/crates/ide_db/src/source_change.rs
+++ b/crates/ide_db/src/source_change.rs
@@ -3,7 +3,7 @@
 //!
 //! It can be viewed as a dual for `AnalysisChange`.
 
-use base_db::FileId;
+use base_db::{AnchoredPathBuf, FileId};
 use text_edit::TextEdit;
 
 #[derive(Default, Debug, Clone)]
@@ -44,8 +44,8 @@ impl From<Vec<SourceFileEdit>> for SourceChange {
 
 #[derive(Debug, Clone)]
 pub enum FileSystemEdit {
-    CreateFile { anchor: FileId, dst: String },
-    MoveFile { src: FileId, anchor: FileId, dst: String },
+    CreateFile { dst: AnchoredPathBuf },
+    MoveFile { src: FileId, dst: AnchoredPathBuf },
 }
 
 impl From<FileSystemEdit> for SourceChange {
diff --git a/crates/rust-analyzer/src/global_state.rs b/crates/rust-analyzer/src/global_state.rs
index a27495d0d..71dc56915 100644
--- a/crates/rust-analyzer/src/global_state.rs
+++ b/crates/rust-analyzer/src/global_state.rs
@@ -13,6 +13,7 @@ use lsp_types::{SemanticTokens, Url};
 use parking_lot::{Mutex, RwLock};
 use project_model::{CargoWorkspace, ProcMacroClient, ProjectWorkspace, Target};
 use rustc_hash::FxHashMap;
+use vfs::AnchoredPathBuf;
 
 use crate::{
     config::Config,
@@ -268,10 +269,10 @@ impl GlobalStateSnapshot {
         Some(self.mem_docs.get(&path)?.version)
     }
 
-    pub(crate) fn anchored_path(&self, file_id: FileId, path: &str) -> Url {
-        let mut base = self.vfs.read().0.file_path(file_id);
+    pub(crate) fn anchored_path(&self, path: &AnchoredPathBuf) -> Url {
+        let mut base = self.vfs.read().0.file_path(path.anchor);
         base.pop();
-        let path = base.join(path).unwrap();
+        let path = base.join(&path.path).unwrap();
         let path = path.as_path().unwrap();
         url_from_abs_path(&path)
     }
diff --git a/crates/rust-analyzer/src/to_proto.rs b/crates/rust-analyzer/src/to_proto.rs
index 01eabe852..715f8927a 100644
--- a/crates/rust-analyzer/src/to_proto.rs
+++ b/crates/rust-analyzer/src/to_proto.rs
@@ -628,17 +628,17 @@ pub(crate) fn resource_op(
     file_system_edit: FileSystemEdit,
 ) -> lsp_types::ResourceOp {
     match file_system_edit {
-        FileSystemEdit::CreateFile { anchor, dst } => {
-            let uri = snap.anchored_path(anchor, &dst);
+        FileSystemEdit::CreateFile { dst } => {
+            let uri = snap.anchored_path(&dst);
             lsp_types::ResourceOp::Create(lsp_types::CreateFile {
                 uri,
                 options: None,
                 annotation: None,
             })
         }
-        FileSystemEdit::MoveFile { src, anchor, dst } => {
+        FileSystemEdit::MoveFile { src, dst } => {
             let old_uri = snap.file_id_to_url(src);
-            let new_uri = snap.anchored_path(anchor, &dst);
+            let new_uri = snap.anchored_path(&dst);
             lsp_types::ResourceOp::Rename(lsp_types::RenameFile {
                 old_uri,
                 new_uri,
diff --git a/crates/vfs/src/anchored_path.rs b/crates/vfs/src/anchored_path.rs
new file mode 100644
index 000000000..02720a32e
--- /dev/null
+++ b/crates/vfs/src/anchored_path.rs
@@ -0,0 +1,39 @@
+//! 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;
+
+#[derive(Clone, PartialEq, Eq, Debug)]
+pub struct AnchoredPathBuf {
+    pub anchor: FileId,
+    pub path: String,
+}
+
+#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+pub struct AnchoredPath<'a> {
+    pub anchor: FileId,
+    pub path: &'a str,
+}
diff --git a/crates/vfs/src/file_set.rs b/crates/vfs/src/file_set.rs
index 9093fbd97..49ca593ac 100644
--- a/crates/vfs/src/file_set.rs
+++ b/crates/vfs/src/file_set.rs
@@ -7,7 +7,7 @@ use std::fmt;
 use fst::{IntoStreamer, Streamer};
 use rustc_hash::FxHashMap;
 
-use crate::{FileId, Vfs, VfsPath};
+use crate::{AnchoredPath, FileId, Vfs, VfsPath};
 
 #[derive(Default, Clone, Eq, PartialEq)]
 pub struct FileSet {
@@ -19,10 +19,10 @@ impl FileSet {
     pub fn len(&self) -> usize {
         self.files.len()
     }
-    pub fn resolve_path(&self, anchor: FileId, path: &str) -> Option<FileId> {
-        let mut base = self.paths[&anchor].clone();
+    pub fn resolve_path(&self, path: AnchoredPath<'_>) -> Option<FileId> {
+        let mut base = self.paths[&path.anchor].clone();
         base.pop();
-        let path = base.join(path)?;
+        let path = base.join(path.path)?;
         self.files.get(&path).copied()
     }
 
diff --git a/crates/vfs/src/lib.rs b/crates/vfs/src/lib.rs
index cdf6f1fd0..a3be579a7 100644
--- a/crates/vfs/src/lib.rs
+++ b/crates/vfs/src/lib.rs
@@ -36,6 +36,7 @@
 //! have a single `FileSet` which unions the two sources.
 mod vfs_path;
 mod path_interner;
+mod anchored_path;
 pub mod file_set;
 pub mod loader;
 
@@ -43,7 +44,10 @@ use std::{fmt, mem};
 
 use crate::path_interner::PathInterner;
 
-pub use crate::vfs_path::VfsPath;
+pub use crate::{
+    anchored_path::{AnchoredPath, AnchoredPathBuf},
+    vfs_path::VfsPath,
+};
 pub use paths::{AbsPath, AbsPathBuf};
 
 #[derive(Copy, Clone, Debug, Ord, PartialOrd, Eq, PartialEq, Hash)]