use relpaths for module resolve

Cargo.lock

@@ -674,6 +674,7 @@ dependencies = [
 name = "ra_hir"
 version = "0.1.0"
 dependencies = [
+ "arrayvec 0.4.9 (registry+https://github.com/rust-lang/crates.io-index)",
  "id-arena 2.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.6.4 (registry+https://github.com/rust-lang/crates.io-index)",

crates/ra_db/src/input.rs

@@ -1,6 +1,7 @@
 use std::sync::Arc;
 
 use rustc_hash::{FxHashSet, FxHashMap};
+use relative_path::RelativePathBuf;
 use ra_syntax::SmolStr;
 use salsa;
 
@@ -85,10 +86,23 @@ salsa::query_group! {
             type FileTextQuery;
             storage input;
         }
+        /// Path to a file, relative to the root of its source root.
+        fn file_relative_path(file_id: FileId) -> RelativePathBuf {
+            type FileRelativePathQuery;
+            storage input;
+        }
         fn file_source_root(file_id: FileId) -> SourceRootId {
             type FileSourceRootQuery;
             storage input;
         }
+        fn source_root_files(id: SourceRootId) -> Arc<FxHashSet<FileId>> {
+            type SourceRootFilesQuery;
+            storage input;
+        }
+        fn source_root_file_by_path(id: SourceRootId, path: RelativePathBuf) -> Option<FileId> {
+            type SourceRootFilesByPathQuery;
+            storage input;
+        }
         fn source_root(id: SourceRootId) -> Arc<SourceRoot> {
             type SourceRootQuery;
             storage input;

crates/ra_hir/Cargo.toml

@@ -5,6 +5,7 @@ version = "0.1.0"
 authors = ["Aleksey Kladov <aleksey.kladov@gmail.com>"]
 
 [dependencies]
+arrayvec = "0.4.9"
 log = "0.4.5"
 relative-path = "0.4.0"
 salsa = "0.8.0"

crates/ra_hir/src/module/imp.rs

@@ -4,9 +4,9 @@ use ra_syntax::{
     ast::{self, NameOwner},
     SmolStr,
 };
-use relative_path::RelativePathBuf;
 use rustc_hash::{FxHashMap, FxHashSet};
-use ra_db::{SourceRoot, SourceRootId, FileResolverImp, Cancelable, FileId,};
+use arrayvec::ArrayVec;
+use ra_db::{SourceRoot, SourceRootId, Cancelable, FileId};
 
 use crate::{
     HirDatabase,
@@ -110,8 +110,7 @@ fn build_subtree(
 
         let (points_to, problem) = match sub {
             Submodule::Declaration(name) => {
-                let (points_to, problem) =
-                    resolve_submodule(source, &name, &source_root.file_resolver);
+                let (points_to, problem) = resolve_submodule(db, source, &name);
                 let points_to = points_to
                     .into_iter()
                     .map(|file_id| match roots.remove(&file_id) {
@@ -153,30 +152,32 @@ fn build_subtree(
 }
 
 fn resolve_submodule(
+    db: &impl HirDatabase,
     source: ModuleSource,
     name: &SmolStr,
-    file_resolver: &FileResolverImp,
 ) -> (Vec<FileId>, Option<Problem>) {
-    // TODO: handle submodules of inline modules properly
+    // FIXME: handle submodules of inline modules properly
     let file_id = source.file_id();
-    let mod_name = file_resolver.file_stem(file_id);
+    let source_root_id = db.file_source_root(file_id);
+    let path = db.file_relative_path(file_id);
+    let dir_path = path.parent().unwrap();
+    let mod_name = path.file_stem().unwrap_or("unknown");
     let is_dir_owner = mod_name == "mod" || mod_name == "lib" || mod_name == "main";
 
-    let file_mod = RelativePathBuf::from(format!("../{}.rs", name));
-    let dir_mod = RelativePathBuf::from(format!("../{}/mod.rs", name));
-    let file_dir_mod = RelativePathBuf::from(format!("../{}/{}.rs", mod_name, name));
-    let tmp1;
-    let tmp2;
-    let candidates = if is_dir_owner {
-        tmp1 = [&file_mod, &dir_mod];
-        tmp1.iter()
+    let file_mod = dir_path.join(format!("{}.rs", name));
+    let dir_mod = dir_path.join(format!("{}/mod.rs", name));
+    let file_dir_mod = dir_path.join(format!("{}/{}.rs", mod_name, name));
+    let mut candidates = ArrayVec::<[_; 2]>::new();
+    if is_dir_owner {
+        candidates.push(file_mod.clone());
+        candidates.push(dir_mod);
     } else {
-        tmp2 = [&file_dir_mod];
-        tmp2.iter()
+        candidates.push(file_dir_mod.clone());
     };
 
     let points_to = candidates
-        .filter_map(|path| file_resolver.resolve(file_id, path))
+        .into_iter()
+        .filter_map(|path| db.source_root_file_by_path(source_root_id, path))
         .collect::<Vec<_>>();
     let problem = if points_to.is_empty() {
         Some(Problem::UnresolvedModule {