feat: let Shared: Send + Sync

Cargo.lock

@@ -117,10 +117,13 @@ dependencies = [
 name = "erg_common"
 version = "0.6.13"
 dependencies = [
+ "backtrace",
  "backtrace-on-stack-overflow",
  "crossterm",
  "hermit-abi",
  "libc",
+ "once_cell",
+ "parking_lot",
  "winapi",
 ]
 
@@ -276,6 +279,12 @@ dependencies = [
  "memchr",
 ]
 
+[[package]]
+name = "once_cell"
+version = "1.17.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b7e5500299e16ebb147ae15a00a942af264cf3688f47923b8fc2cd5858f23ad3"
+
 [[package]]
 name = "parking_lot"
 version = "0.12.1"

crates/els/completion.rs

@@ -4,11 +4,11 @@ use serde_json::Value;
 
 use erg_common::config::{ErgConfig, Input};
 use erg_common::dict::Dict;
-use erg_common::env::erg_pystd_path;
+use erg_common::env::ERG_PYSTD_PATH;
 use erg_common::impl_u8_enum;
 use erg_common::python_util::BUILTIN_PYTHON_MODS;
 use erg_common::set::Set;
-use erg_common::shared::AtomicShared;
+use erg_common::shared::Shared;
 use erg_common::traits::Locational;
 
 use erg_compiler::artifact::{BuildRunnable, Buildable};
@@ -174,7 +174,7 @@ impl<'b> CompletionOrderSetter<'b> {
     }
 }
 
-type Cache = AtomicShared<Dict<String, Vec<CompletionItem>>>;
+type Cache = Shared<Dict<String, Vec<CompletionItem>>>;
 
 #[derive(Debug)]
 pub struct CompletionCache {
@@ -296,7 +296,7 @@ fn load_modules(cfg: ErgConfig, cache: Cache) {
     if cache.get("<module>").is_none() {
         cache.insert("<module>".into(), module_completions());
     }
-    let std_path = erg_pystd_path().display().to_string().replace('\\', "/");
+    let std_path = ERG_PYSTD_PATH.display().to_string().replace('\\', "/");
     for (path, entry) in shared.py_mod_cache.iter() {
         let dir = entry.module.context.local_dir();
         let mod_name = path.display().to_string().replace('\\', "/");
@@ -316,7 +316,7 @@ fn load_modules(cfg: ErgConfig, cache: Cache) {
 
 impl CompletionCache {
     pub fn new(cfg: ErgConfig) -> Self {
-        let cache = AtomicShared::new(Dict::default());
+        let cache = Shared::new(Dict::default());
         let clone = cache.clone();
         std::thread::spawn(move || {
             crate::_log!("load_modules");

crates/els/file_cache.rs

@@ -12,7 +12,7 @@ use lsp_types::{
 };
 
 use erg_common::dict::Dict;
-use erg_common::shared::AtomicShared;
+use erg_common::shared::Shared;
 use erg_common::traits::DequeStream;
 use erg_compiler::erg_parser::lex::Lexer;
 use erg_compiler::erg_parser::token::{Token, TokenStream};
@@ -50,13 +50,13 @@ impl FileCacheEntry {
 /// This struct can save changes in real-time & incrementally.
 #[derive(Debug, Clone)]
 pub struct FileCache {
-    pub files: AtomicShared<Dict<NormalizedUrl, FileCacheEntry>>,
+    pub files: Shared<Dict<NormalizedUrl, FileCacheEntry>>,
 }
 
 impl FileCache {
     pub fn new() -> Self {
         Self {
-            files: AtomicShared::new(Dict::new()),
+            files: Shared::new(Dict::new()),
         }
     }
 

crates/els/server.rs

@@ -14,7 +14,7 @@ use serde_json::Value;
 
 use erg_common::config::ErgConfig;
 use erg_common::dict::Dict;
-use erg_common::env::erg_path;
+use erg_common::env::ERG_PATH;
 use erg_common::normalize_path;
 
 use erg_compiler::artifact::{BuildRunnable, IncompleteArtifact};
@@ -224,7 +224,7 @@ impl<Checker: BuildRunnable> Server<Checker> {
             comp_cache: CompletionCache::new(cfg.copy()),
             cfg,
             home: normalize_path(std::env::current_dir().unwrap_or_default()),
-            erg_path: erg_path(), // already normalized
+            erg_path: ERG_PATH.clone(), // already normalized
             client_capas: ClientCapabilities::default(),
             disabled_features: vec![],
             opt_features: vec![],

crates/erg_common/Cargo.toml

@@ -33,7 +33,10 @@ version = "0.3"
 features = ["consoleapi"]
 
 [dependencies]
+backtrace = "0.3"
+once_cell = "1.17"
 crossterm = { optional = true, version = "0.25.0" }
+parking_lot = "0.12"
 
 [lib]
 path = "lib.rs"

crates/erg_common/cache.rs

@@ -1,15 +1,15 @@
 use std::borrow::{Borrow, ToOwned};
-use std::cell::RefCell;
 use std::hash::Hash;
 use std::sync::Arc;
 use std::thread::LocalKey;
 
 use crate::dict::Dict;
 use crate::set::Set;
+use crate::shared::Shared;
 use crate::{ArcArray, Str};
 
 #[derive(Debug)]
-pub struct CacheSet<T: ?Sized>(RefCell<Set<Arc<T>>>);
+pub struct CacheSet<T: ?Sized>(Shared<Set<Arc<T>>>);
 
 impl<T: ?Sized> Default for CacheSet<T> {
     fn default() -> Self {
@@ -19,7 +19,7 @@ impl<T: ?Sized> Default for CacheSet<T> {
 
 impl<T: ?Sized> CacheSet<T> {
     pub fn new() -> Self {
-        Self(RefCell::new(Set::new()))
+        Self(Shared::new(Set::new()))
     }
 }
 
@@ -72,6 +72,6 @@ impl<T: Hash + Eq> CacheSet<T> {
     }
 }
 
-pub struct CacheDict<K, V: ?Sized>(RefCell<Dict<K, Arc<V>>>);
+pub struct CacheDict<K, V: ?Sized>(Shared<Dict<K, Arc<V>>>);
 
-pub struct GlobalCacheDict<K: 'static, V: ?Sized + 'static>(LocalKey<RefCell<CacheDict<K, V>>>);
+pub struct GlobalCacheDict<K: 'static, V: ?Sized + 'static>(LocalKey<Shared<CacheDict<K, V>>>);

crates/erg_common/config.rs

@@ -11,7 +11,7 @@ use std::process;
 use std::str::FromStr;
 
 use crate::consts::ERG_MODE;
-use crate::env::{erg_py_external_lib_path, erg_pystd_path, erg_std_path, python_site_packages};
+use crate::env::{ERG_EXTERNAL_LIB_PATH, ERG_PYSTD_PATH, ERG_STD_PATH, PYTHON_SITE_PACKAGES};
 use crate::help_messages::{command_message, mode_message, OPTIONS};
 use crate::levenshtein::get_similar_name;
 use crate::pathutil::add_postfix_foreach;
@@ -581,12 +581,12 @@ impl Input {
     pub fn resolve_real_path(&self, path: &Path) -> Option<PathBuf> {
         if let Ok(path) = self.resolve_local(path) {
             Some(path)
-        } else if let Ok(path) = erg_std_path()
+        } else if let Ok(path) = ERG_STD_PATH
             .join(format!("{}.er", path.display()))
             .canonicalize()
         {
             Some(normalize_path(path))
-        } else if let Ok(path) = erg_std_path()
+        } else if let Ok(path) = ERG_STD_PATH
             .join(format!("{}", path.display()))
             .join("__init__.er")
             .canonicalize()
@@ -612,13 +612,12 @@ impl Input {
         if let Ok(path) = self.resolve_local_decl(path) {
             Some(path)
         } else {
-            let py_roots = [erg_pystd_path, erg_py_external_lib_path];
+            for root in [ERG_PYSTD_PATH.clone(), ERG_EXTERNAL_LIB_PATH.clone()] {
-            for root in py_roots {
+                if let Some(path) = Self::resolve_std_decl_path(root, path) {
-                if let Some(path) = Self::resolve_std_decl_path(root(), path) {
                     return Some(path);
                 }
             }
-            for site_packages in python_site_packages() {
+            for site_packages in PYTHON_SITE_PACKAGES.clone() {
                 if let Some(path) = Self::resolve_site_pkgs_decl_path(site_packages, path) {
                     return Some(path);
                 }

crates/erg_common/env.rs

@@ -1,6 +1,8 @@
 use std::env::var;
 use std::path::{Path, PathBuf};
 
+use once_cell::sync::Lazy;
+
 use crate::normalize_path;
 use crate::python_util::get_sys_path;
 use crate::style::colors::*;
@@ -66,43 +68,19 @@ fn _python_site_packages() -> impl Iterator<Item = PathBuf> {
         })
 }
 
-thread_local! {
+pub static ERG_PATH: Lazy<PathBuf> = Lazy::new(|| normalize_path(_erg_path()));
-    pub static ERG_PATH: PathBuf = normalize_path(_erg_path());
+pub static ERG_STD_PATH: Lazy<PathBuf> = Lazy::new(|| normalize_path(_erg_std_path()));
-    pub static ERG_STD_PATH: PathBuf = normalize_path(_erg_std_path());
+pub static ERG_STD_DECL_PATH: Lazy<PathBuf> = Lazy::new(|| normalize_path(_erg_std_decl_path()));
-    pub static ERG_STD_DECL_PATH: PathBuf = normalize_path(_erg_std_decl_path());
+pub static ERG_PYSTD_PATH: Lazy<PathBuf> = Lazy::new(|| normalize_path(_erg_pystd_path()));
-    pub static ERG_PYSTD_PATH: PathBuf = normalize_path(_erg_pystd_path());
+pub static ERG_EXTERNAL_LIB_PATH: Lazy<PathBuf> =
-    pub static ERG_EXTERNAL_LIB_PATH: PathBuf = normalize_path(_erg_external_lib_path());
+    Lazy::new(|| normalize_path(_erg_external_lib_path()));
-    pub static PYTHON_SITE_PACKAGES: Vec<PathBuf> = _python_site_packages().collect();
+pub static PYTHON_SITE_PACKAGES: Lazy<Vec<PathBuf>> =
-}
+    Lazy::new(|| _python_site_packages().collect());
-
-pub fn erg_path() -> PathBuf {
-    ERG_PATH.with(|s| s.clone())
-}
-
-pub fn erg_std_path() -> PathBuf {
-    ERG_STD_PATH.with(|s| s.clone())
-}
-
-pub fn erg_std_decl_path() -> PathBuf {
-    ERG_STD_DECL_PATH.with(|s| s.clone())
-}
-
-pub fn erg_pystd_path() -> PathBuf {
-    ERG_PYSTD_PATH.with(|s| s.clone())
-}
-
-pub fn erg_py_external_lib_path() -> PathBuf {
-    ERG_EXTERNAL_LIB_PATH.with(|s| s.clone())
-}
-
-pub fn python_site_packages() -> Vec<PathBuf> {
-    PYTHON_SITE_PACKAGES.with(|s| s.clone())
-}
 
 pub fn is_std_decl_path(path: &Path) -> bool {
-    path.starts_with(erg_pystd_path())
+    path.starts_with(ERG_PYSTD_PATH.as_path())
-        || path.starts_with(erg_std_decl_path())
+        || path.starts_with(ERG_STD_DECL_PATH.as_path())
-        || path.starts_with(erg_py_external_lib_path())
+        || path.starts_with(ERG_EXTERNAL_LIB_PATH.as_path())
 }
 
 pub fn is_pystd_main_module(path: &Path) -> bool {
@@ -113,6 +91,6 @@ pub fn is_pystd_main_module(path: &Path) -> bool {
     } else {
         path.pop();
     }
-    let pystd_path = erg_pystd_path();
+    // let pystd_path = erg_pystd_path();
-    path == pystd_path
+    path == ERG_PYSTD_PATH.as_path()
 }

crates/erg_common/fresh.rs

@@ -1,21 +1,17 @@
 use crate::shared::Shared;
 
-thread_local! {
+use once_cell::sync::Lazy;
-    static VAR_ID: Shared<usize> = Shared::new(0);
+
-}
+pub static VAR_ID: Lazy<Shared<usize>> = Lazy::new(|| Shared::new(0));
 
 pub fn fresh_varname() -> String {
-    VAR_ID.with(|id| {
+    *VAR_ID.borrow_mut() += 1;
-        *id.borrow_mut() += 1;
+    let i = *VAR_ID.borrow();
-        let i = *id.borrow();
     format!("%v{i}")
-    })
 }
 
 pub fn fresh_param_name() -> String {
-    VAR_ID.with(|id| {
+    *VAR_ID.borrow_mut() += 1;
-        *id.borrow_mut() += 1;
+    let i = *VAR_ID.borrow();
-        let i = *id.borrow();
     format!("%p{i}")
-    })
 }

crates/erg_common/shared.rs

@@ -1,10 +1,13 @@
-use std::cell::{Ref, RefCell, RefMut};
+// use std::cell::{Ref, RefCell, RefMut};
 use std::fmt;
 use std::hash::{Hash, Hasher};
-use std::rc::Rc;
+// use std::rc::Rc;
-use std::sync::{Arc, Mutex, MutexGuard};
+pub use parking_lot::{
+    MappedRwLockReadGuard, MappedRwLockWriteGuard, RwLock, RwLockReadGuard, RwLockWriteGuard,
+};
+use std::sync::Arc;
 
-#[derive(Debug)]
+/*#[derive(Debug)]
 pub struct Shared<T: ?Sized>(Rc<RefCell<T>>);
 
 impl<T: PartialEq> PartialEq for Shared<T> {
@@ -108,14 +111,14 @@ impl<T: Clone> Shared<T> {
     pub fn clone_inner(&self) -> T {
         self.borrow().clone()
     }
-}
+}*/
 
 #[derive(Debug)]
-pub struct AtomicShared<T: ?Sized>(Arc<Mutex<T>>);
+pub struct Shared<T: ?Sized>(Arc<RwLock<T>>);
 
-impl<T: PartialEq> PartialEq for AtomicShared<T>
+impl<T: PartialEq> PartialEq for Shared<T>
 where
-    Mutex<T>: PartialEq,
+    RwLock<T>: PartialEq,
 {
     #[inline]
     fn eq(&self, other: &Self) -> bool {
@@ -123,35 +126,35 @@ where
     }
 }
 
-impl<T: ?Sized> Clone for AtomicShared<T> {
+impl<T: ?Sized> Clone for Shared<T> {
-    fn clone(&self) -> AtomicShared<T> {
+    fn clone(&self) -> Shared<T> {
         Self(Arc::clone(&self.0))
     }
 }
 
-impl<T: Eq> Eq for AtomicShared<T> where Mutex<T>: Eq {}
+impl<T: Eq> Eq for Shared<T> where RwLock<T>: Eq {}
 
-impl<T: Hash> Hash for AtomicShared<T> {
+impl<T: Hash> Hash for Shared<T> {
     fn hash<H: Hasher>(&self, state: &mut H) {
         self.borrow_mut().hash(state);
     }
 }
 
-impl<T: Default> Default for AtomicShared<T> {
+impl<T: Default> Default for Shared<T> {
     fn default() -> Self {
         Self::new(Default::default())
     }
 }
 
-impl<T: fmt::Display> fmt::Display for AtomicShared<T> {
+impl<T: fmt::Display> fmt::Display for Shared<T> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(f, "{}", self.borrow_mut())
     }
 }
 
-impl<T> AtomicShared<T> {
+impl<T> Shared<T> {
     pub fn new(t: T) -> Self {
-        Self(Arc::new(Mutex::new(t)))
+        Self(Arc::new(RwLock::new(t)))
     }
 
     #[inline]
@@ -160,27 +163,56 @@ impl<T> AtomicShared<T> {
             Ok(mutex) => mutex,
             Err(_rc) => panic!("unwrapping failed"),
         };
-        Mutex::into_inner(mutex).unwrap()
+        RwLock::into_inner(mutex)
     }
 }
 
-impl<T: ?Sized> AtomicShared<T> {
+impl<T: ?Sized> Shared<T> {
     #[inline]
     pub fn copy(&self) -> Self {
         Self(self.0.clone())
     }
 
     #[inline]
-    pub fn borrow_mut(&self) -> MutexGuard<'_, T> {
+    pub fn borrow(&self) -> RwLockReadGuard<'_, T> {
-        self.0.lock().unwrap()
+        println!("borrowing {}", std::any::type_name::<T>());
+        let res = self.0.read();
+        println!("borrowed successfully");
+        res
+    }
+
+    #[inline]
+    pub fn borrow_mut(&self) -> RwLockWriteGuard<'_, T> {
+        println!("borrowing mut {}", std::any::type_name::<T>());
+        let res = self.0.write();
+        println!("borrowed mut successfully");
+        res
     }
 
     pub fn get_mut(&mut self) -> Option<&mut T> {
-        Arc::get_mut(&mut self.0).map(|mutex| mutex.get_mut().unwrap())
+        Arc::get_mut(&mut self.0).map(|mutex| mutex.get_mut())
+    }
+
+    pub fn as_ptr(&self) -> *mut T {
+        Arc::as_ptr(&self.0) as *mut T
+    }
+
+    pub fn can_borrow(&self) -> bool {
+        self.0.try_read().is_some()
+    }
+
+    pub fn can_borrow_mut(&self) -> bool {
+        self.0.try_write().is_some()
+    }
+
+    /// # Safety
+    /// don't call this except you need to handle cyclic references.
+    pub unsafe fn force_unlock_write(&self) {
+        self.0.force_unlock_write();
     }
 }
 
-impl<T: Clone> AtomicShared<T> {
+impl<T: Clone> Shared<T> {
     #[inline]
     pub fn clone_inner(&self) -> T {
         self.borrow_mut().clone()

crates/erg_common/stdin.rs

@@ -1,5 +1,5 @@
-use std::cell::RefCell;
+// use std::cell::RefCell;
-use std::thread::LocalKey;
+// use std::thread::LocalKey;
 
 #[cfg(not(feature = "full-repl"))]
 use std::io::{stdin, BufRead, BufReader};
@@ -261,57 +261,52 @@ impl StdinReader {
     }
 }
 
-thread_local! {
+static READER: crate::shared::RwLock<StdinReader> = crate::shared::RwLock::new(StdinReader {
-    static READER: RefCell<StdinReader> = RefCell::new(StdinReader{
     block_begin: 1,
     lineno: 1,
     buf: vec![],
     #[cfg(feature = "full-repl")]
     history_input_position: 1,
-        indent: 1
+    indent: 1,
 });
-}
 
 #[derive(Debug)]
-pub struct GlobalStdin(LocalKey<RefCell<StdinReader>>);
+pub struct GlobalStdin(&'static crate::shared::RwLock<StdinReader>);
 
-pub static GLOBAL_STDIN: GlobalStdin = GlobalStdin(READER);
+pub static GLOBAL_STDIN: GlobalStdin = GlobalStdin(&READER);
 
 impl GlobalStdin {
     pub fn read(&'static self) -> String {
-        self.0.with(|s| s.borrow_mut().read())
+        self.0.write().read()
     }
 
     pub fn reread(&'static self) -> String {
-        self.0.with(|s| s.borrow().reread())
+        self.0.read().reread()
     }
 
     pub fn reread_lines(&'static self, ln_begin: usize, ln_end: usize) -> Vec<String> {
-        self.0
+        self.0.read().reread_lines(ln_begin, ln_end)
-            .with(|s| s.borrow_mut().reread_lines(ln_begin, ln_end))
     }
 
     pub fn lineno(&'static self) -> usize {
-        self.0.with(|s| s.borrow().lineno)
+        self.0.read().lineno
     }
 
     pub fn block_begin(&'static self) -> usize {
-        self.0.with(|s| s.borrow().block_begin)
+        self.0.read().block_begin
     }
 
     pub fn set_block_begin(&'static self, n: usize) {
-        self.0.with(|s| s.borrow_mut().block_begin = n);
+        self.0.write().block_begin = n;
     }
 
     pub fn set_indent(&'static self, n: usize) {
-        self.0.with(|s| s.borrow_mut().indent = n as u16);
+        self.0.write().indent = n as u16;
     }
 
     pub fn insert_whitespace(&'static self, whitespace: &str) {
-        self.0.with(|s| {
+        if let Some(line) = self.0.write().last_line() {
-            if let Some(line) = s.borrow_mut().last_line() {
             line.insert_str(0, whitespace);
         }
-        })
     }
 }

crates/erg_compiler/codegen.rs

@@ -8,7 +8,7 @@ use crate::ty::codeobj::{CodeObj, CodeObjFlags, MakeFunctionFlags};
 use crate::ty::value::GenTypeObj;
 use erg_common::cache::CacheSet;
 use erg_common::config::{ErgConfig, Input};
-use erg_common::env::erg_std_path;
+use erg_common::env::ERG_STD_PATH;
 use erg_common::error::{ErrorDisplay, Location};
 use erg_common::opcode::{CommonOpcode, CompareOp};
 use erg_common::opcode308::Opcode308;
@@ -3120,7 +3120,7 @@ impl PyCodeGenerator {
         );
         self.emit_load_name_instr(Identifier::private("#path"));
         self.emit_load_method_instr(Identifier::public("append"));
-        self.emit_load_const(erg_std_path().to_str().unwrap());
+        self.emit_load_const(ERG_STD_PATH.to_str().unwrap());
         self.emit_call_instr(1, Method);
         self.stack_dec();
         self.emit_pop_top();

crates/erg_compiler/context/initialize/mod.rs

@@ -15,6 +15,7 @@ use std::path::PathBuf;
 use erg_common::config::ErgConfig;
 use erg_common::consts::{DEBUG_MODE, ERG_MODE, PYTHON_MODE};
 use erg_common::dict;
+use erg_common::env::{ERG_PYSTD_PATH, ERG_STD_DECL_PATH};
 use erg_common::error::Location;
 use erg_common::fresh::fresh_varname;
 #[allow(unused_imports)]
@@ -513,11 +514,11 @@ const KW_OFFSET: &str = "offset";
 const KW_WHENCE: &str = "whence";
 
 pub fn builtins_path() -> PathBuf {
-    erg_common::env::erg_pystd_path().join("builtins.d.er")
+    ERG_PYSTD_PATH.join("builtins.d.er")
 }
 
 pub fn std_decl_path() -> PathBuf {
-    erg_common::env::erg_std_decl_path()
+    ERG_STD_DECL_PATH.clone()
 }
 
 impl Context {
@@ -772,7 +773,8 @@ impl Context {
             );
             self.consts.insert(name.clone(), val);
             for impl_trait in ctx.super_traits.iter() {
-                if let Some(impls) = self.trait_impls().get_mut(&impl_trait.qual_name()) {
+                if self.trait_impls().get(&impl_trait.qual_name()).is_some() {
+                    let mut impls = self.trait_impls().get_mut(&impl_trait.qual_name());
                     impls.insert(TraitImpl::new(t.clone(), impl_trait.clone()));
                 } else {
                     self.trait_impls().register(
@@ -848,7 +850,8 @@ impl Context {
             }
             self.consts.insert(name.clone(), val);
             for impl_trait in ctx.super_traits.iter() {
-                if let Some(impls) = self.trait_impls().get_mut(&impl_trait.qual_name()) {
+                if self.trait_impls().get(&impl_trait.qual_name()).is_some() {
+                    let mut impls = self.trait_impls().get_mut(&impl_trait.qual_name());
                     impls.insert(TraitImpl::new(t.clone(), impl_trait.clone()));
                 } else {
                     self.trait_impls().register(
@@ -912,7 +915,12 @@ impl Context {
                 }
             }
             if let ContextKind::GluePatch(tr_impl) = &ctx.kind {
-                if let Some(impls) = self.trait_impls().get_mut(&tr_impl.sup_trait.qual_name()) {
+                if self
+                    .trait_impls()
+                    .get(&tr_impl.sup_trait.qual_name())
+                    .is_some()
+                {
+                    let mut impls = self.trait_impls().get_mut(&tr_impl.sup_trait.qual_name());
                     impls.insert(tr_impl.clone());
                 } else {
                     self.trait_impls()

crates/erg_compiler/context/register.rs

@@ -1653,7 +1653,8 @@ impl Context {
             self.decls.insert(name.clone(), vi);
             self.consts.insert(name.clone(), val);
             for impl_trait in ctx.super_traits.iter() {
-                if let Some(impls) = self.trait_impls().get_mut(&impl_trait.qual_name()) {
+                if self.trait_impls().get(&impl_trait.qual_name()).is_some() {
+                    let mut impls = self.trait_impls().get_mut(&impl_trait.qual_name());
                     impls.insert(TraitImpl::new(t.clone(), impl_trait.clone()));
                 } else {
                     self.trait_impls().register(
@@ -1733,7 +1734,8 @@ impl Context {
             self.consts
                 .insert(name.clone(), ValueObj::Type(TypeObj::Generated(gen)));
             for impl_trait in ctx.super_traits.iter() {
-                if let Some(impls) = self.trait_impls().get_mut(&impl_trait.qual_name()) {
+                if self.trait_impls().get(&impl_trait.qual_name()).is_some() {
+                    let mut impls = self.trait_impls().get_mut(&impl_trait.qual_name());
                     impls.insert(TraitImpl::new(t.clone(), impl_trait.clone()));
                 } else {
                     self.trait_impls().register(

crates/erg_compiler/lower.rs

@@ -1892,12 +1892,18 @@ impl ASTLowerer {
         trait_loc: &impl Locational,
     ) -> LowerResult<()> {
         // TODO: polymorphic trait
-        if let Some(impls) = self
+        if self
             .module
             .context
             .trait_impls()
-            .get_mut(&trait_.qual_name())
+            .get(&trait_.qual_name())
+            .is_some()
         {
+            let mut impls = self
+                .module
+                .context
+                .trait_impls()
+                .get_mut(&trait_.qual_name());
             impls.insert(TraitImpl::new(class.clone(), trait_.clone()));
         } else {
             self.module.context.trait_impls().register(

crates/erg_compiler/module/cache.rs

@@ -2,7 +2,7 @@ use std::borrow::Borrow;
 use std::fmt;
 use std::hash::Hash;
 use std::path::PathBuf;
-use std::rc::Rc;
+use std::sync::Arc;
 
 use erg_common::config::ErgConfig;
 use erg_common::dict::Dict;
@@ -32,7 +32,7 @@ impl ModId {
 pub struct ModuleEntry {
     pub id: ModId, // builtin == 0, __main__ == 1
     pub hir: Option<HIR>,
-    pub module: Rc<ModuleContext>,
+    pub module: Arc<ModuleContext>,
 }
 
 impl fmt::Display for ModuleEntry {
@@ -50,7 +50,7 @@ impl ModuleEntry {
         Self {
             id,
             hir,
-            module: Rc::new(ctx),
+            module: Arc::new(ctx),
         }
     }
 
@@ -58,7 +58,7 @@ impl ModuleEntry {
         Self {
             id: ModId::builtin(),
             hir: None,
-            module: Rc::new(ctx),
+            module: Arc::new(ctx),
         }
     }
 
@@ -189,7 +189,7 @@ impl SharedModuleCache {
         ref_.get_mut(path)
     }
 
-    pub fn get_ctx<Q: Eq + Hash + ?Sized>(&self, path: &Q) -> Option<Rc<ModuleContext>>
+    pub fn get_ctx<Q: Eq + Hash + ?Sized>(&self, path: &Q) -> Option<Arc<ModuleContext>>
     where
         PathBuf: Borrow<Q>,
     {
@@ -236,7 +236,7 @@ impl SharedModuleCache {
         for path in self.keys() {
             self.remove(&path);
         }
-        self.register(builtin_path, None, Rc::try_unwrap(builtin.module).unwrap());
+        self.register(builtin_path, None, Arc::try_unwrap(builtin.module).unwrap());
     }
 
     pub fn rename_path(&self, path: &PathBuf, new: PathBuf) {

crates/erg_compiler/module/impls.rs

@@ -4,7 +4,7 @@ use std::hash::Hash;
 
 use erg_common::dict::Dict;
 use erg_common::set::Set;
-use erg_common::shared::Shared;
+use erg_common::shared::{MappedRwLockWriteGuard, RwLockWriteGuard, Shared};
 use erg_common::Str;
 
 use crate::context::TraitImpl;
@@ -84,12 +84,13 @@ impl SharedTraitImpls {
         ref_.get(path)
     }
 
-    pub fn get_mut<Q: Eq + Hash + ?Sized>(&self, path: &Q) -> Option<&mut Set<TraitImpl>>
+    pub fn get_mut<Q: Eq + Hash + ?Sized>(&self, path: &Q) -> MappedRwLockWriteGuard<Set<TraitImpl>>
     where
         Str: Borrow<Q>,
     {
-        let ref_ = unsafe { self.0.as_ptr().as_mut().unwrap() };
+        // let ref_ = unsafe { self.0.as_ptr().as_mut().unwrap() };
-        ref_.get_mut(path)
+        // ref_.get_mut(path)
+        RwLockWriteGuard::map(self.0.borrow_mut(), |tis| tis.get_mut(path).unwrap())
     }
 
     pub fn register(&self, name: Str, impls: Set<TraitImpl>) {

crates/erg_compiler/ty/free.rs

@@ -1,8 +1,9 @@
-use std::cell::{Ref, RefMut};
+// use std::cell::{Ref, RefMut};
 use std::fmt;
 use std::hash::{Hash, Hasher};
 use std::mem;
 
+use erg_common::fresh::VAR_ID;
 use erg_common::shared::Shared;
 use erg_common::traits::{LimitedDisplay, StructuralEq};
 use erg_common::Str;
@@ -17,10 +18,6 @@ pub type Id = usize;
 /// HACK: see doc/compiler/inference.md for details
 pub const GENERIC_LEVEL: usize = usize::MAX;
 
-thread_local! {
-    static UNBOUND_ID: Shared<usize> = Shared::new(0);
-}
-
 pub trait HasLevel {
     fn level(&self) -> Option<Level>;
     fn set_level(&self, lev: Level);
@@ -429,14 +426,12 @@ impl<T> FreeKind<T> {
     }
 
     pub fn new_unbound(lev: Level, constraint: Constraint) -> Self {
-        UNBOUND_ID.with(|id| {
+        *VAR_ID.borrow_mut() += 1;
-            *id.borrow_mut() += 1;
         Self::Unbound {
-                id: *id.borrow(),
+            id: *VAR_ID.borrow(),
             lev,
             constraint,
         }
-        })
     }
 
     pub const fn named_unbound(name: Str, lev: Level, constraint: Constraint) -> Self {
@@ -601,10 +596,10 @@ impl<T: LimitedDisplay> LimitedDisplay for Free<T> {
 }
 
 impl<T> Free<T> {
-    pub fn borrow(&self) -> Ref<'_, FreeKind<T>> {
+    pub fn borrow(&self) -> erg_common::shared::RwLockReadGuard<'_, FreeKind<T>> {
         self.0.borrow()
     }
-    pub fn borrow_mut(&self) -> RefMut<'_, FreeKind<T>> {
+    pub fn borrow_mut(&self) -> erg_common::shared::RwLockWriteGuard<'_, FreeKind<T>> {
         self.0.borrow_mut()
     }
     /// very unsafe, use `force_replace` instead whenever possible
@@ -620,8 +615,9 @@ impl<T> Free<T> {
             return;
         }
         unsafe {
-            *self.0.as_ptr() = new;
+            self.0.force_unlock_write();
         }
+        *self.0.borrow_mut() = new;
     }
     pub fn can_borrow(&self) -> bool {
         self.0.can_borrow()
@@ -650,7 +646,7 @@ impl Free<TyParam> {
     }
 }
 
-impl<T: StructuralEq + CanbeFree + Clone + Default> StructuralEq for Free<T> {
+impl<T: StructuralEq + CanbeFree + Clone + Default + fmt::Debug> StructuralEq for Free<T> {
     fn structural_eq(&self, other: &Self) -> bool {
         if let (Some((l, r)), Some((l2, r2))) = (self.get_subsup(), other.get_subsup()) {
             self.dummy_link();
@@ -736,14 +732,12 @@ impl<T> Free<T> {
     }
 
     pub fn new_unbound(level: Level, constraint: Constraint) -> Self {
-        UNBOUND_ID.with(|id| {
+        *VAR_ID.borrow_mut() += 1;
-            *id.borrow_mut() += 1;
         Self(Shared::new(FreeKind::unbound(
-                *id.borrow(),
+            *VAR_ID.borrow(),
             level,
             constraint,
         )))
-        })
     }
 
     pub fn new_named_unbound(name: Str, level: Level, constraint: Constraint) -> Self {
@@ -766,8 +760,8 @@ impl<T> Free<T> {
 
     /// returns linked type (panic if self is unbounded)
     /// NOTE: check by `.is_linked` before call
-    pub fn crack(&self) -> Ref<'_, T> {
+    pub fn crack(&self) -> erg_common::shared::MappedRwLockReadGuard<'_, T> {
-        Ref::map(self.borrow(), |f| match f {
+        erg_common::shared::RwLockReadGuard::map(self.borrow(), |f| match f {
             FreeKind::Linked(t) | FreeKind::UndoableLinked { t, .. } => t,
             FreeKind::Unbound { .. } | FreeKind::NamedUnbound { .. } => {
                 panic!("the value is unbounded")
@@ -775,8 +769,8 @@ impl<T> Free<T> {
         })
     }
 
-    pub fn crack_constraint(&self) -> Ref<'_, Constraint> {
+    pub fn crack_constraint(&self) -> erg_common::shared::MappedRwLockReadGuard<'_, Constraint> {
-        Ref::map(self.borrow(), |f| match f {
+        erg_common::shared::RwLockReadGuard::map(self.borrow(), |f| match f {
             FreeKind::Linked(_) | FreeKind::UndoableLinked { .. } => panic!("the value is linked"),
             FreeKind::Unbound { constraint, .. } | FreeKind::NamedUnbound { constraint, .. } => {
                 constraint
@@ -814,7 +808,7 @@ impl<T> Free<T> {
     }
 }
 
-impl<T: Clone> Free<T> {
+impl<T: Clone + fmt::Debug> Free<T> {
     /// SAFETY: use `Type/TyParam::link` instead of this.
     /// This method may cause circular references.
     pub(super) fn link(&self, to: &T) {
@@ -871,7 +865,7 @@ impl<T: Clone> Free<T> {
                 let prev = *previous.clone();
                 self.force_replace(prev);
             }
-            _other => panic!("cannot undo"),
+            _other => panic!("cannot undo: {_other:?}"),
         }
     }
 
@@ -920,7 +914,7 @@ impl<T: Clone> Free<T> {
     }
 }
 
-impl<T: Default + Clone> Free<T> {
+impl<T: Default + Clone + fmt::Debug> Free<T> {
     pub fn dummy_link(&self) {
         self.forced_undoable_link(&T::default());
     }