5 files changed, 90 insertions, 42 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 385e7a7bc..242fca700 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1020,7 +1020,6 @@ dependencies = [
  "ra_prof",
  "ra_syntax",
  "ra_tt",
- "relative-path",
  "rustc-hash",
  "salsa",
  "stdx",
@@ -1409,12 +1408,6 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "26412eb97c6b088a6997e05f69403a802a92d520de2f8e63c2b65f9e0f47c4e8"
 
 [[package]]
-name = "relative-path"
-version = "1.2.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c602122c47b382cd045b10866a084b184035d45d8c2609cdd3762852ddfae2a1"
-
-[[package]]
 name = "remove_dir_all"
 version = "0.5.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
diff --git a/crates/ra_db/Cargo.toml b/crates/ra_db/Cargo.toml
index ef85266db..889142442 100644
--- a/crates/ra_db/Cargo.toml
+++ b/crates/ra_db/Cargo.toml
@@ -9,7 +9,6 @@ doctest = false
 
 [dependencies]
 salsa = "0.15.0"
-relative-path = "1.0.0"
 rustc-hash = "1.1.0"
 
 ra_syntax = { path = "../ra_syntax" }
diff --git a/crates/ra_db/src/lib.rs b/crates/ra_db/src/lib.rs
index 3a8fd44c4..f25be24fe 100644
--- a/crates/ra_db/src/lib.rs
+++ b/crates/ra_db/src/lib.rs
@@ -16,7 +16,6 @@ pub use crate::{
         SourceRoot, SourceRootId,
     },
 };
-pub use relative_path::{RelativePath, RelativePathBuf};
 pub use salsa;
 pub use vfs::{file_set::FileSet, VfsPath};
 
diff --git a/crates/ra_hir_def/src/nameres/mod_resolution.rs b/crates/ra_hir_def/src/nameres/mod_resolution.rs
index 39e9a6d97..953961632 100644
--- a/crates/ra_hir_def/src/nameres/mod_resolution.rs
+++ b/crates/ra_hir_def/src/nameres/mod_resolution.rs
@@ -1,23 +1,24 @@
 //! This module resolves `mod foo;` declaration to file.
 use hir_expand::name::Name;
-use ra_db::{FileId, RelativePathBuf};
+use ra_db::FileId;
 use ra_syntax::SmolStr;
 
 use crate::{db::DefDatabase, HirFileId};
 
 #[derive(Clone, Debug)]
 pub(super) struct ModDir {
-    /// `.` for `mod.rs`, `lib.rs`
-    /// `./foo` for `foo.rs`
-    /// `./foo/bar` for `mod bar { mod x; }` nested in `foo.rs`
-    path: RelativePathBuf,
+    /// `` for `mod.rs`, `lib.rs`
+    /// `foo/` for `foo.rs`
+    /// `foo/bar/` for `mod bar { mod x; }` nested in `foo.rs`
+    /// Invariant: path.is_empty() || path.ends_with('/')
+    dir_path: DirPath,
     /// inside `./foo.rs`, mods with `#[path]` should *not* be relative to `./foo/`
     root_non_dir_owner: bool,
 }
 
 impl ModDir {
     pub(super) fn root() -> ModDir {
-        ModDir { path: RelativePathBuf::default(), root_non_dir_owner: false }
+        ModDir { dir_path: DirPath::empty(), root_non_dir_owner: false }
     }
 
     pub(super) fn descend_into_definition(
@@ -25,17 +26,21 @@ impl ModDir {
         name: &Name,
         attr_path: Option<&SmolStr>,
     ) -> ModDir {
-        let mut path = self.path.clone();
-        match attr_to_path(attr_path) {
-            None => path.push(&name.to_string()),
+        let path = match attr_path.map(|it| it.as_str()) {
+            None => {
+                let mut path = self.dir_path.clone();
+                path.push(&name.to_string());
+                path
+            }
             Some(attr_path) => {
-                if self.root_non_dir_owner {
-                    assert!(path.pop());
+                let mut path = self.dir_path.join_attr(attr_path, self.root_non_dir_owner);
+                if !(path.is_empty() || path.ends_with('/')) {
+                    path.push('/')
                 }
-                path.push(attr_path);
+                DirPath::new(path)
             }
-        }
-        ModDir { path, root_non_dir_owner: false }
+        };
+        ModDir { dir_path: path, root_non_dir_owner: false }
     }
 
     pub(super) fn resolve_declaration(
@@ -48,34 +53,87 @@ impl ModDir {
         let file_id = file_id.original_file(db.upcast());
 
         let mut candidate_files = Vec::new();
-        match attr_to_path(attr_path) {
+        match attr_path {
             Some(attr_path) => {
-                let base =
-                    if self.root_non_dir_owner { self.path.parent().unwrap() } else { &self.path };
-                candidate_files.push(base.join(attr_path).to_string())
+                candidate_files.push(self.dir_path.join_attr(attr_path, self.root_non_dir_owner))
             }
             None => {
-                candidate_files.push(self.path.join(&format!("{}.rs", name)).to_string());
-                candidate_files.push(self.path.join(&format!("{}/mod.rs", name)).to_string());
+                candidate_files.push(format!("{}{}.rs", self.dir_path.0, name));
+                candidate_files.push(format!("{}{}/mod.rs", self.dir_path.0, name));
             }
         };
 
         for candidate in candidate_files.iter() {
             if let Some(file_id) = db.resolve_path(file_id, candidate.as_str()) {
-                let mut root_non_dir_owner = false;
-                let mut mod_path = RelativePathBuf::new();
                 let is_mod_rs = candidate.ends_with("mod.rs");
-                if !(is_mod_rs || attr_path.is_some()) {
-                    root_non_dir_owner = true;
-                    mod_path.push(&name.to_string());
-                }
-                return Ok((file_id, is_mod_rs, ModDir { path: mod_path, root_non_dir_owner }));
+
+                let (dir_path, root_non_dir_owner) = if is_mod_rs || attr_path.is_some() {
+                    (DirPath::empty(), false)
+                } else {
+                    (DirPath::new(format!("{}/", name)), true)
+                };
+                return Ok((file_id, is_mod_rs, ModDir { dir_path, root_non_dir_owner }));
             }
         }
         Err(candidate_files.remove(0))
     }
 }
 
-fn attr_to_path(attr: Option<&SmolStr>) -> Option<RelativePathBuf> {
-    attr.and_then(|it| RelativePathBuf::from_path(&it.replace("\\", "/")).ok())
+#[derive(Clone, Debug)]
+struct DirPath(String);
+
+impl DirPath {
+    fn assert_invariant(&self) {
+        assert!(self.0.is_empty() || self.0.ends_with('/'));
+    }
+    fn new(repr: String) -> DirPath {
+        let res = DirPath(repr);
+        res.assert_invariant();
+        res
+    }
+    fn empty() -> DirPath {
+        DirPath::new(String::new())
+    }
+    fn push(&mut self, name: &str) {
+        self.0.push_str(name);
+        self.0.push('/');
+        self.assert_invariant();
+    }
+    fn parent(&self) -> Option<&str> {
+        if self.0.is_empty() {
+            return None;
+        };
+        let idx =
+            self.0[..self.0.len() - '/'.len_utf8()].rfind('/').map_or(0, |it| it + '/'.len_utf8());
+        Some(&self.0[..idx])
+    }
+    /// So this is the case which doesn't really work I think if we try to be
+    /// 100% platform agnostic:
+    ///
+    /// ```
+    /// mod a {
+    ///     #[path="C://sad/face"]
+    ///     mod b { mod c; }
+    /// }
+    /// ```
+    ///
+    /// Here, we need to join logical dir path to a string path from an
+    /// attribute. Ideally, we should somehow losslessly communicate the whole
+    /// construction to `FileLoader`.
+    fn join_attr(&self, mut attr: &str, relative_to_parent: bool) -> String {
+        let base = if relative_to_parent { self.parent().unwrap() } else { &self.0 };
+
+        if attr.starts_with("./") {
+            attr = &attr["./".len()..];
+        }
+        let tmp;
+        let attr = if attr.contains('\\') {
+            tmp = attr.replace('\\', "/");
+            &tmp
+        } else {
+            attr
+        };
+        let res = format!("{}{}", base, attr);
+        res
+    }
 }
diff --git a/crates/ra_ide_db/src/change.rs b/crates/ra_ide_db/src/change.rs
index 84c6f40ff..d1a255dcf 100644
--- a/crates/ra_ide_db/src/change.rs
+++ b/crates/ra_ide_db/src/change.rs
@@ -5,8 +5,7 @@ use std::{fmt, sync::Arc, time};
 
 use ra_db::{
     salsa::{Database, Durability, SweepStrategy},
-    CrateGraph, FileId, RelativePathBuf, SourceDatabase, SourceDatabaseExt, SourceRoot,
-    SourceRootId,
+    CrateGraph, FileId, SourceDatabase, SourceDatabaseExt, SourceRoot, SourceRootId,
 };
 use ra_prof::{memory_usage, profile, Bytes};
 use rustc_hash::FxHashSet;
@@ -57,14 +56,14 @@ impl AnalysisChange {
 #[derive(Debug)]
 struct AddFile {
     file_id: FileId,
-    path: RelativePathBuf,
+    path: String,
     text: Arc<String>,
 }
 
 #[derive(Debug)]
 struct RemoveFile {
     file_id: FileId,
-    path: RelativePathBuf,
+    path: String,
 }
 
 #[derive(Default)]