internal: flatten module hierarchy

It seems that any crate can be made better by flattening the modules
down to a single layer?

crates/ide/src/lib.rs

@@ -39,6 +39,7 @@ macro_rules! eprintln {
 mod move_item;
 mod parent_module;
 mod references;
+mod rename;
 mod fn_references;
 mod runnables;
 mod ssr;
@@ -79,7 +80,8 @@ macro_rules! eprintln {
     markup::Markup,
     move_item::Direction,
     prime_caches::PrimeCachesProgress,
-    references::{rename::RenameError, ReferenceSearchResult},
+    references::ReferenceSearchResult,
+    rename::RenameError,
     runnables::{Runnable, RunnableKind, TestId},
     syntax_highlighting::{
         tags::{Highlight, HlMod, HlMods, HlOperator, HlPunct, HlTag},
@@ -591,14 +593,14 @@ pub fn rename(
         position: FilePosition,
         new_name: &str,
     ) -> Cancellable<Result<SourceChange, RenameError>> {
-        self.with_db(|db| references::rename::rename(db, position, new_name))
+        self.with_db(|db| rename::rename(db, position, new_name))
     }
 
     pub fn prepare_rename(
         &self,
         position: FilePosition,
     ) -> Cancellable<Result<RangeInfo<()>, RenameError>> {
-        self.with_db(|db| references::rename::prepare_rename(db, position))
+        self.with_db(|db| rename::prepare_rename(db, position))
     }
 
     pub fn will_rename_file(
@@ -606,7 +608,7 @@ pub fn will_rename_file(
         file_id: FileId,
         new_name_stem: &str,
     ) -> Cancellable<Option<SourceChange>> {
-        self.with_db(|db| references::rename::will_rename_file(db, file_id, new_name_stem))
+        self.with_db(|db| rename::will_rename_file(db, file_id, new_name_stem))
     }
 
     pub fn structural_search_replace(

crates/ide/src/references.rs

@@ -9,8 +9,6 @@
 //! at the index that the match starts at and its tree parent is
 //! resolved to the search element definition, we get a reference.
 
-pub(crate) mod rename;
-
 use hir::{PathResolution, Semantics};
 use ide_db::{
     base_db::FileId,

crates/ide/src/rename.rs

@@ -1,7 +1,8 @@
-//! Renaming functionality
+//! Renaming functionality.
 //!
-//! All reference and file rename requests go through here where the corresponding [`SourceChange`]s
-//! will be calculated.
+//! This is mostly front-end for [`ide_db::rename`], but it also includes the
+//! tests. This module also implements a couple of magic tricks, like renaming
+//! `self` and to `self` (to switch between associated function and method).
 use hir::{AsAssocItem, InFile, Semantics};
 use ide_db::{
     base_db::FileId,