From 2b108133ac35b6886c0bd2c7e7bda83e18ba3b79 Mon Sep 17 00:00:00 2001
From: Aleksey Kladov <aleksey.kladov@gmail.com>
Date: Wed, 4 Nov 2020 15:31:35 +0100
Subject: Don't stack overflow on circular modules

closes #6453
---
 crates/hir_def/src/nameres/mod_resolution.rs | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

(limited to 'crates/hir_def/src/nameres/mod_resolution.rs')

diff --git a/crates/hir_def/src/nameres/mod_resolution.rs b/crates/hir_def/src/nameres/mod_resolution.rs
index e8389b484..c0c789cae 100644
--- a/crates/hir_def/src/nameres/mod_resolution.rs
+++ b/crates/hir_def/src/nameres/mod_resolution.rs
@@ -2,9 +2,12 @@
 use base_db::FileId;
 use hir_expand::name::Name;
 use syntax::SmolStr;
+use test_utils::mark;
 
 use crate::{db::DefDatabase, HirFileId};
 
+const MOD_DEPTH_LIMIT: u32 = 32;
+
 #[derive(Clone, Debug)]
 pub(super) struct ModDir {
     /// `` for `mod.rs`, `lib.rs`
@@ -14,18 +17,28 @@ pub(super) struct ModDir {
     dir_path: DirPath,
     /// inside `./foo.rs`, mods with `#[path]` should *not* be relative to `./foo/`
     root_non_dir_owner: bool,
+    depth: u32,
 }
 
 impl ModDir {
     pub(super) fn root() -> ModDir {
-        ModDir { dir_path: DirPath::empty(), root_non_dir_owner: false }
+        ModDir { dir_path: DirPath::empty(), root_non_dir_owner: false, depth: 0 }
+    }
+    fn child(&self, dir_path: DirPath, root_non_dir_owner: bool) -> Option<ModDir> {
+        let depth = self.depth + 1;
+        if depth > MOD_DEPTH_LIMIT {
+            log::error!("MOD_DEPTH_LIMIT exceeded");
+            mark::hit!(circular_mods);
+            return None;
+        }
+        Some(ModDir { dir_path, root_non_dir_owner, depth })
     }
 
     pub(super) fn descend_into_definition(
         &self,
         name: &Name,
         attr_path: Option<&SmolStr>,
-    ) -> ModDir {
+    ) -> Option<ModDir> {
         let path = match attr_path.map(|it| it.as_str()) {
             None => {
                 let mut path = self.dir_path.clone();
@@ -40,7 +53,7 @@ impl ModDir {
                 DirPath::new(path)
             }
         };
-        ModDir { dir_path: path, root_non_dir_owner: false }
+        self.child(path, false)
     }
 
     pub(super) fn resolve_declaration(
@@ -72,7 +85,9 @@ impl ModDir {
                 } else {
                     (DirPath::new(format!("{}/", name)), true)
                 };
-                return Ok((file_id, is_mod_rs, ModDir { dir_path, root_non_dir_owner }));
+                if let Some(mod_dir) = self.child(dir_path, root_non_dir_owner) {
+                    return Ok((file_id, is_mod_rs, mod_dir));
+                }
             }
         }
         Err(candidate_files.remove(0))
-- 
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