diff --git a/compiler/erg_common/traits.rs b/compiler/erg_common/traits.rs
index 37798e09..56646c85 100644
--- a/compiler/erg_common/traits.rs
+++ b/compiler/erg_common/traits.rs
@@ -298,9 +298,7 @@ pub trait ImmutableStream<T>: Sized {
 
 // for Runnable::run
 fn expect_block(src: &str) -> bool {
-    src.ends_with(&['=', ':'])
-        || src.ends_with("->")
-        || src.ends_with("=>")
+    src.ends_with(&['=', ':']) || src.ends_with("->") || src.ends_with("=>")
 }
 
 /// This trait implements REPL (Read-Eval-Print-Loop) automatically
@@ -331,9 +329,7 @@ pub trait Runnable: Sized {
     fn run(cfg: ErgConfig) {
         let mut instance = Self::new(cfg);
         let res = match instance.input() {
-            Input::File(_) | Input::Pipe(_) | Input::Str(_) => {
-                instance.exec()
-            }
+            Input::File(_) | Input::Pipe(_) | Input::Str(_) => instance.exec(),
             Input::REPL => {
                 let output = stdout();
                 let mut output = BufWriter::new(output.lock());
diff --git a/compiler/erg_common/tsort.rs b/compiler/erg_common/tsort.rs
index 9cb7ba7f..fe232844 100644
--- a/compiler/erg_common/tsort.rs
+++ b/compiler/erg_common/tsort.rs
@@ -42,7 +42,12 @@ fn reorder_by_key<T: Eq, U>(mut g: Graph<T, U>, idx: Vec<T>) -> Graph<T, U> {
     g
 }
 
-fn dfs<T: Eq + Hash + Clone, U>(g: &Graph<T, U>, v: T, used: &mut Set<T>, idx: &mut Vec<T>) -> Result<(), ()> {
+fn dfs<T: Eq + Hash + Clone, U>(
+    g: &Graph<T, U>,
+    v: T,
+    used: &mut Set<T>,
+    idx: &mut Vec<T>,
+) -> Result<(), ()> {
     used.insert(v.clone());
     for node_id in g.iter().find(|n| n.id == v).unwrap().depends_on.iter() {
         // detecting cycles
diff --git a/compiler/erg_common/ty.rs b/compiler/erg_common/ty.rs
index a5c89b69..6f22ab72 100644
--- a/compiler/erg_common/ty.rs
+++ b/compiler/erg_common/ty.rs
@@ -94,7 +94,10 @@ pub enum Constraint {
     /// <: T
     SubtypeOf(Type),
     /// :> Sub, <: Sup
-    Sandwiched { sub: Type, sup: Type },
+    Sandwiched {
+        sub: Type,
+        sup: Type,
+    },
     /// : T
     TypeOf(Type),
     Uninited,
@@ -311,8 +314,14 @@ impl<T: Clone + HasLevel> Free<T> {
     pub fn unwrap_unbound(self) -> (Option<Str>, usize, Constraint) {
         match self.0.clone_inner() {
             FreeKind::Linked(_) => panic!("the value is linked"),
-            FreeKind::Unbound { constraint, lev, .. } => (None, lev, constraint),
-            | FreeKind::NamedUnbound { name, lev, constraint } => (Some(name), lev, constraint),
+            FreeKind::Unbound {
+                constraint, lev, ..
+            } => (None, lev, constraint),
+            FreeKind::NamedUnbound {
+                name,
+                lev,
+                constraint,
+            } => (Some(name), lev, constraint),
         }
     }
 
@@ -339,8 +348,9 @@ impl<T: Clone + HasLevel> Free<T> {
     pub fn crack_constraint(&self) -> Ref<'_, Constraint> {
         Ref::map(self.0.borrow(), |f| match f {
             FreeKind::Linked(_) => panic!("the value is linked"),
-            FreeKind::Unbound { constraint, .. }
-            | FreeKind::NamedUnbound { constraint, .. } => constraint,
+            FreeKind::Unbound { constraint, .. } | FreeKind::NamedUnbound { constraint, .. } => {
+                constraint
+            }
         })
     }
 
@@ -902,7 +912,7 @@ impl TyParam {
 
     pub fn update_constraint(&self, new_constraint: Constraint) {
         match self {
-            Self::Type(t) => { t.update_constraint(new_constraint) },
+            Self::Type(t) => t.update_constraint(new_constraint),
             _ => {}
         }
     }
@@ -2861,8 +2871,10 @@ impl Type {
 
     pub fn update_constraint(&self, new_constraint: Constraint) {
         match self {
-            Self::FreeVar(fv) => { fv.update_constraint(new_constraint); },
-            _ => {},
+            Self::FreeVar(fv) => {
+                fv.update_constraint(new_constraint);
+            }
+            _ => {}
         }
     }
 }
diff --git a/compiler/erg_compiler/context.rs b/compiler/erg_compiler/context.rs
index 400ba04f..e79cd02e 100644
--- a/compiler/erg_compiler/context.rs
+++ b/compiler/erg_compiler/context.rs
@@ -55,16 +55,16 @@ pub enum TyParamIdx {
 impl TyParamIdx {
     pub fn search(search_from: &Type, target: &Type) -> Option<Self> {
         match search_from {
-            Type::Poly{ params, .. } => {
+            Type::Poly { params, .. } => {
                 for (i, tp) in params.iter().enumerate() {
                     match tp {
-                        TyParam::Type(t) if t.rec_eq(target) => { return Some(Self::Nth(i)) },
-                        TyParam::Type(t) if t.is_monomorphic() => {},
+                        TyParam::Type(t) if t.rec_eq(target) => return Some(Self::Nth(i)),
+                        TyParam::Type(t) if t.is_monomorphic() => {}
                         other => todo!("{other:?}"),
                     }
                 }
                 None
-            },
+            }
             _ => todo!(),
         }
     }
@@ -81,7 +81,7 @@ impl TyParamIdx {
                     TyParam::Type(t) => *t.clone(),
                     _ => todo!(),
                 }
-            },
+            }
             Self::Nested(_, _) => todo!(),
         }
     }
@@ -192,23 +192,26 @@ impl TyVarContext {
         self_
     }
 
-    fn instantiate_const_template(&mut self, var_name: &str, _callee_name: &Str, ct: &ConstTemplate) -> TyParam {
+    fn instantiate_const_template(
+        &mut self,
+        var_name: &str,
+        _callee_name: &Str,
+        ct: &ConstTemplate,
+    ) -> TyParam {
         match ct {
-            ConstTemplate::Obj(o) => {
-                match o {
-                    ConstObj::Type(t) if t.is_mono_q() => {
-                        if t.name() == "Self" {
-                            let constraint = Constraint::TypeOf(Type);
-                            let t = Type::named_free_var(Str::rc(var_name), self.level, constraint);
-                            TyParam::t(t)
-                        } else {
-                            todo!()
-                        }
-                    },
-                    ConstObj::Type(t) => TyParam::t(*t.clone()),
-                    v @ ConstObj::Value(_) => TyParam::ConstObj(v.clone()),
-                    other => todo!("{other}"),
+            ConstTemplate::Obj(o) => match o {
+                ConstObj::Type(t) if t.is_mono_q() => {
+                    if t.name() == "Self" {
+                        let constraint = Constraint::TypeOf(Type);
+                        let t = Type::named_free_var(Str::rc(var_name), self.level, constraint);
+                        TyParam::t(t)
+                    } else {
+                        todo!()
+                    }
                 }
+                ConstObj::Type(t) => TyParam::t(*t.clone()),
+                v @ ConstObj::Value(_) => TyParam::ConstObj(v.clone()),
+                other => todo!("{other}"),
             },
             ConstTemplate::App { .. } => {
                 todo!()
@@ -216,22 +219,32 @@ impl TyVarContext {
         }
     }
 
-    fn instantiate_poly(&mut self, tvar_name: &str, name: &Str, params: Vec<TyParam>, ctx: &Context) -> Type {
+    fn instantiate_poly(
+        &mut self,
+        tvar_name: &str,
+        name: &Str,
+        params: Vec<TyParam>,
+        ctx: &Context,
+    ) -> Type {
         if let Some(temp_defaults) = ctx.rec_get_const_param_defaults(&name) {
-            let c = ctx.rec_type_ctx_by_name(name).unwrap_or_else(|| panic!("{} not found", name));
+            let c = ctx
+                .rec_type_ctx_by_name(name)
+                .unwrap_or_else(|| panic!("{} not found", name));
             let defined_params_len = c.params.len();
             let given_params_len = params.len();
-            if defined_params_len < given_params_len { panic!() }
+            if defined_params_len < given_params_len {
+                panic!()
+            }
             let inst_non_defaults = params.into_iter().map(|p| self.instantiate_tp(p)).collect();
             let mut inst_defaults = vec![];
-            for c in temp_defaults.into_iter().take(defined_params_len - given_params_len) {
+            for c in temp_defaults
+                .into_iter()
+                .take(defined_params_len - given_params_len)
+            {
                 let c = self.instantiate_const_template(tvar_name, name, c);
                 inst_defaults.push(c);
             }
-            Type::poly(
-                name,
-                [inst_non_defaults, inst_defaults].concat(),
-            )
+            Type::poly(name, [inst_non_defaults, inst_defaults].concat())
         } else {
             Type::poly(
                 name,
@@ -257,7 +270,10 @@ impl TyVarContext {
                     tp.update_constraint(constraint);
                 } else {
                     let name = Str::rc(sub.name());
-                    self.push_tyvar(name.clone(), Type::named_free_var(name, self.level, constraint));
+                    self.push_tyvar(
+                        name.clone(),
+                        Type::named_free_var(name, self.level, constraint),
+                    );
                 }
             }
             TyBound::Supertype { sup, sub } => {
@@ -275,7 +291,10 @@ impl TyVarContext {
                     tp.update_constraint(constraint);
                 } else {
                     let name = Str::rc(sup.name());
-                    self.push_tyvar(name.clone(), Type::named_free_var(name, self.level, constraint));
+                    self.push_tyvar(
+                        name.clone(),
+                        Type::named_free_var(name, self.level, constraint),
+                    );
                 }
             }
             TyBound::Sandwiched { sub, mid, sup } => {
@@ -300,7 +319,10 @@ impl TyVarContext {
                     tp.update_constraint(constraint);
                 } else {
                     let name = Str::rc(mid.name());
-                    self.push_tyvar(name.clone(), Type::named_free_var(name, self.level, constraint));
+                    self.push_tyvar(
+                        name.clone(),
+                        Type::named_free_var(name, self.level, constraint),
+                    );
                 }
             }
             TyBound::Instance { name, t } => {
@@ -327,7 +349,10 @@ impl TyVarContext {
                     if let Some(tp) = self.typaram_instances.get(&name) {
                         tp.update_constraint(constraint);
                     } else {
-                        self.push_typaram(name.clone(), TyParam::named_free_var(name, self.level, t));
+                        self.push_typaram(
+                            name.clone(),
+                            TyParam::named_free_var(name, self.level, t),
+                        );
                     }
                 }
             }
@@ -421,11 +446,19 @@ impl TyVarContext {
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub enum ConstTemplate {
     Obj(ConstObj),
-    App{ name: Str, non_default_args: Vec<Type>, default_args: Vec<ConstTemplate> },
+    App {
+        name: Str,
+        non_default_args: Vec<Type>,
+        default_args: Vec<ConstTemplate>,
+    },
 }
 
 impl ConstTemplate {
-    pub const fn app(name: &'static str, non_default_args: Vec<Type>, default_args: Vec<ConstTemplate>) -> Self {
+    pub const fn app(
+        name: &'static str,
+        non_default_args: Vec<Type>,
+        default_args: Vec<ConstTemplate>,
+    ) -> Self {
         ConstTemplate::App {
             name: Str::ever(name),
             non_default_args,
@@ -1564,25 +1597,25 @@ impl Context {
                 for (param_ty, pos_arg) in params.clone().zip(pos_args) {
                     let arg_t = pos_arg.expr.ref_t();
                     let param_t = &param_ty.ty;
-                    self.sub_unify(
-                        arg_t,
-                        param_t,
-                        None,
-                        Some(pos_arg.loc()),
-                    )
-                    .map_err(|e| {
-                        // REVIEW:
-                        let name = callee.var_full_name().unwrap_or_else(|| "".to_string());
-                        let name =
-                            name + "::" + param_ty.name.as_ref().map(|s| readable_name(&s[..])).unwrap_or("");
-                        TyCheckError::type_mismatch_error(
-                            e.core.loc,
-                            e.caused_by,
-                            &name[..],
-                            param_t,
-                            arg_t,
-                        )
-                    })?;
+                    self.sub_unify(arg_t, param_t, None, Some(pos_arg.loc()))
+                        .map_err(|e| {
+                            // REVIEW:
+                            let name = callee.var_full_name().unwrap_or_else(|| "".to_string());
+                            let name = name
+                                + "::"
+                                + param_ty
+                                    .name
+                                    .as_ref()
+                                    .map(|s| readable_name(&s[..]))
+                                    .unwrap_or("");
+                            TyCheckError::type_mismatch_error(
+                                e.core.loc,
+                                e.caused_by,
+                                &name[..],
+                                param_t,
+                                arg_t,
+                            )
+                        })?;
                     if let Some(name) = &param_ty.name {
                         if passed_params.contains(name) {
                             return Err(TyCheckError::multiple_args_error(
@@ -1628,10 +1661,10 @@ impl Context {
             TyParam::FreeVar(fv) if fv.is_linked() => {
                 let inner = fv.unwrap_linked();
                 self.deref_tp(inner)
-            },
+            }
             TyParam::FreeVar(_fv) if self.level == 0 => {
                 Err(TyCheckError::dummy_infer_error(fn_name!(), line!()))
-            },
+            }
             TyParam::Type(t) => Ok(TyParam::t(self.deref_tyvar(*t)?)),
             TyParam::App { name, mut args } => {
                 for param in args.iter_mut() {
@@ -1645,25 +1678,24 @@ impl Context {
             TyParam::MonoProj { .. }
             | TyParam::MonoQVar(_)
             | TyParam::PolyQVar { .. }
-            | TyParam::Failure if self.level == 0 => Err(TyCheckError::dummy_infer_error(fn_name!(), line!())),
+            | TyParam::Failure
+                if self.level == 0 =>
+            {
+                Err(TyCheckError::dummy_infer_error(fn_name!(), line!()))
+            }
             t => Ok(t),
         }
     }
 
     fn deref_constraint(&self, constraint: Constraint) -> TyCheckResult<Constraint> {
         match constraint {
-            Constraint::SubtypeOf(sup) => {
-                Ok(Constraint::SubtypeOf(self.deref_tyvar(sup)?))
-            },
-            Constraint::Sandwiched { sub, sup } => {
-                Ok(Constraint::sandwiched(self.deref_tyvar(sub)?, self.deref_tyvar(sup)?))
-            },
-            Constraint::SupertypeOf(sub) => {
-                Ok(Constraint::SupertypeOf(self.deref_tyvar(sub)?))
-            },
-            Constraint::TypeOf(t) => {
-                Ok(Constraint::TypeOf(self.deref_tyvar(t)?))
-            },
+            Constraint::SubtypeOf(sup) => Ok(Constraint::SubtypeOf(self.deref_tyvar(sup)?)),
+            Constraint::Sandwiched { sub, sup } => Ok(Constraint::sandwiched(
+                self.deref_tyvar(sub)?,
+                self.deref_tyvar(sup)?,
+            )),
+            Constraint::SupertypeOf(sub) => Ok(Constraint::SupertypeOf(self.deref_tyvar(sub)?)),
+            Constraint::TypeOf(t) => Ok(Constraint::TypeOf(self.deref_tyvar(t)?)),
             _ => unreachable!(),
         }
     }
@@ -1682,17 +1714,16 @@ impl Context {
                 } else {
                     Ok(Type::FreeVar(fv))
                 }
-            },
+            }
             // ?T(<: Add(?R(<: T), ?O(<: U)) => ?T(<: Add(T, U))
             Type::FreeVar(fv) if fv.is_unbound() => {
                 if self.level == 0 {
                     match &*fv.crack_constraint() {
-                        Constraint::SupertypeOf(t)
-                        | Constraint::SubtypeOf(t) => Ok(t.clone()),
+                        Constraint::SupertypeOf(t) | Constraint::SubtypeOf(t) => Ok(t.clone()),
                         Constraint::Sandwiched { sub, .. } => Ok(sub.clone()),
                         Constraint::TypeOf(_) => {
                             Err(TyCheckError::dummy_infer_error(fn_name!(), line!()))
-                        },
+                        }
                         _ => unreachable!(),
                     }
                 } else {
@@ -1701,11 +1732,11 @@ impl Context {
                     fv.update_constraint(new_constraint);
                     Ok(Type::FreeVar(fv))
                 }
-            },
+            }
             Type::FreeVar(fv) if fv.is_linked() => {
                 let t = fv.unwrap_linked();
                 self.deref_tyvar(t)
-            },
+            }
             Type::Poly { name, mut params } => {
                 for param in params.iter_mut() {
                     *param = self.deref_tp(mem::take(param))?;
@@ -1761,14 +1792,14 @@ impl Context {
                     _ => todo!(),
                 }
                 Ok(())
-            },
+            }
             hir::Expr::Array(array) => {
                 array.t = self.deref_tyvar(mem::take(&mut array.t))?;
                 for elem in array.elems.pos_args.iter_mut() {
                     self.deref_expr_t(&mut elem.expr)?;
                 }
                 Ok(())
-            },
+            }
             hir::Expr::Dict(_dict) => {
                 todo!()
             }
@@ -1778,13 +1809,13 @@ impl Context {
                 self.deref_expr_t(&mut binop.lhs)?;
                 self.deref_expr_t(&mut binop.rhs)?;
                 Ok(())
-            },
+            }
             hir::Expr::UnaryOp(unaryop) => {
                 let t = unaryop.signature_mut_t().unwrap();
                 *t = self.deref_tyvar(mem::take(t))?;
                 self.deref_expr_t(&mut unaryop.expr)?;
                 Ok(())
-            },
+            }
             hir::Expr::Call(call) => {
                 let t = call.signature_mut_t().unwrap();
                 *t = self.deref_tyvar(mem::take(t))?;
@@ -1796,15 +1827,15 @@ impl Context {
             hir::Expr::Decl(decl) => {
                 decl.t = self.deref_tyvar(mem::take(&mut decl.t))?;
                 Ok(())
-            },
+            }
             hir::Expr::Def(def) => {
                 match &mut def.sig {
                     hir::Signature::Var(var) => {
                         var.t = self.deref_tyvar(mem::take(&mut var.t))?;
-                    },
+                    }
                     hir::Signature::Subr(subr) => {
                         subr.t = self.deref_tyvar(mem::take(&mut subr.t))?;
-                    },
+                    }
                 }
                 for chunk in def.body.block.iter_mut() {
                     self.deref_expr_t(chunk)?;
@@ -2311,7 +2342,7 @@ impl Context {
                                     sub_loc,
                                     sup_loc,
                                     self.caused_by(),
-                                ))
+                                ));
                             } else {
                                 *constraint = Constraint::sandwiched(l.clone(), mem::take(sup));
                             }
@@ -2328,7 +2359,7 @@ impl Context {
                                     sub_loc,
                                     sup_loc,
                                     self.caused_by(),
-                                ))
+                                ));
                             } else {
                                 let union = self.union(l, sub);
                                 *constraint = Constraint::sandwiched(union, mem::take(sub));
@@ -2336,7 +2367,7 @@ impl Context {
                         }
                         Constraint::TypeOf(_t) => {
                             *constraint = Constraint::SupertypeOf(l.clone());
-                        },
+                        }
                         _ => {}
                     },
                     _ => {}
@@ -2358,7 +2389,7 @@ impl Context {
                                     sub_loc,
                                     sup_loc,
                                     self.caused_by(),
-                                ))
+                                ));
                             } else {
                                 *constraint = Constraint::sandwiched(sub.clone(), r.clone());
                             }
@@ -2366,9 +2397,7 @@ impl Context {
                         // sub_unify(?T(<: Int), Nat): (?T(<: Nat))
                         // sub_unify(?T(<: Nat), Int): (/* OK */)
                         // sub_unify(?T(<: Str), Int): (/* Error */) // TODO:
-                        Constraint::SubtypeOf(sup)
-                            if self.rec_full_supertype_of(sup, r) =>
-                        {
+                        Constraint::SubtypeOf(sup) if self.rec_full_supertype_of(sup, r) => {
                             *constraint = Constraint::SubtypeOf(r.clone());
                         }
                         // sub_unify((Int <: ?T <: Ratio), Nat): (/* Error */)
@@ -2388,13 +2417,13 @@ impl Context {
                         // sub_unify(?T(: Type), Int): (?T(<: Int))
                         Constraint::TypeOf(_t) => {
                             *constraint = Constraint::SubtypeOf(r.clone());
-                        },
+                        }
                         _ => {}
                     },
                     _ => {}
                 }
                 return Ok(());
-            },
+            }
             (Type::FreeVar(_fv), _r) => todo!(),
             (l @ Refinement(_), r @ Refinement(_)) => return self.unify(l, r, sub_loc, sup_loc),
             _ => {}
@@ -3299,9 +3328,7 @@ impl Context {
                         }
                         // `(?T :> X) :> Y` is true
                         // `(?T :> Str) :> Int` is true (?T :> Str or Int)
-                        Constraint::SupertypeOf(_sub) => {
-                            true
-                        },
+                        Constraint::SupertypeOf(_sub) => true,
                         // `(Nat <: ?T <: Ratio) :> Nat` can be true
                         Constraint::Sandwiched { sup, .. } => {
                             self.formal_supertype_of(sup, rhs, bounds, lhs_variance)
@@ -3331,8 +3358,8 @@ impl Context {
                         // `Str :> (?T <: Int)` is false
                         Constraint::SubtypeOf(sup) => {
                             self.formal_supertype_of(lhs, sup, bounds, lhs_variance)
-                            || self.formal_subtype_of(lhs, sup, bounds, lhs_variance)
-                        },
+                                || self.formal_subtype_of(lhs, sup, bounds, lhs_variance)
+                        }
                         // `Int :> (?T :> Nat)` can be true, `Nat :> (?T :> Int)` is false
                         Constraint::SupertypeOf(sub) => {
                             self.formal_supertype_of(lhs, sub, bounds, lhs_variance)
@@ -3386,9 +3413,7 @@ impl Context {
             // Int :> {I: Int | ...} == true
             // Real :> {I: Int | ...} == false
             // Int :> {I: Str| ...} == false
-            (l, Refinement(r)) => {
-                self.formal_supertype_of(l, &r.t, bounds, lhs_variance)
-            },
+            (l, Refinement(r)) => self.formal_supertype_of(l, &r.t, bounds, lhs_variance),
             // ({I: Int | True} :> Int) == true, ({N: Nat | ...} :> Int) == false, ({I: Int | I >= 0} :> Int) == false
             (Refinement(l), r) => {
                 if l.preds
@@ -3991,7 +4016,9 @@ impl Context {
         ctxs.sort_by(|(lhs, _), (rhs, _)| {
             // HACK: Equal for unrelated types
             // This doesn't work with [Int, Str, Nat] for example
-            self.cmp_t(lhs, rhs).try_into().unwrap_or_else(|_| panic!("{lhs}, {rhs}")) // _or(Ordering::Equal)
+            self.cmp_t(lhs, rhs)
+                .try_into()
+                .unwrap_or_else(|_| panic!("{lhs}, {rhs}")) // _or(Ordering::Equal)
         });
         ctxs.into_iter().map(|(_, ctx)| ctx)
     }
@@ -4041,14 +4068,8 @@ impl Context {
         }
     }
 
-    pub(crate) fn rec_type_ctx_by_name<'a>(
-        &'a self,
-        t_name: &'a str,
-    ) -> Option<&'a Context> {
-        if let Some((_, ctx)) = self.types
-            .iter()
-            .find(|(t, _ctx)| t.name() == t_name)
-        {
+    pub(crate) fn rec_type_ctx_by_name<'a>(&'a self, t_name: &'a str) -> Option<&'a Context> {
+        if let Some((_, ctx)) = self.types.iter().find(|(t, _ctx)| t.name() == t_name) {
             return Some(ctx);
         }
         if let Some(outer) = &self.outer {
@@ -4060,11 +4081,13 @@ impl Context {
 
     fn rec_get_const_param_defaults(&self, name: &str) -> Option<&Vec<ConstTemplate>> {
         if let Some(impls) = self.const_param_defaults.get(name) {
-            return Some(impls)
+            return Some(impls);
         }
         if let Some(outer) = &self.outer {
             outer.rec_get_const_param_defaults(name)
-        } else { None }
+        } else {
+            None
+        }
     }
 
     // 再帰サブルーチン/型の推論を可能にするため、予め登録しておく
diff --git a/compiler/erg_compiler/error.rs b/compiler/erg_compiler/error.rs
index 2a62f2fe..c2f45080 100644
--- a/compiler/erg_compiler/error.rs
+++ b/compiler/erg_compiler/error.rs
@@ -455,7 +455,6 @@ impl TyCheckError {
         Self::new(ErrorCore::unreachable(fn_name, line), "".into())
     }
 
-
     pub fn reassign_error(loc: Location, caused_by: Str, name: &str) -> Self {
         let name = readable_name(name);
         Self::new(
diff --git a/compiler/erg_compiler/eval.rs b/compiler/erg_compiler/eval.rs
index d44b54a1..da6c9547 100644
--- a/compiler/erg_compiler/eval.rs
+++ b/compiler/erg_compiler/eval.rs
@@ -38,7 +38,13 @@ impl SubstContext {
         }
     }
 
-    fn substitute(&self, quant_t: Type, ty_ctx: &Context, level: usize, ctx: &Context) -> TyCheckResult<Type> {
+    fn substitute(
+        &self,
+        quant_t: Type,
+        ty_ctx: &Context,
+        level: usize,
+        ctx: &Context,
+    ) -> TyCheckResult<Type> {
         let bounds = ty_ctx.type_params_bounds();
         let tv_ctx = TyVarContext::new(level, bounds, ctx);
         let (inst, _) = Context::instantiate_t(quant_t, tv_ctx);
@@ -366,7 +372,10 @@ impl Evaluator {
                 if let Some(outer) = &ctx.outer {
                     self.eval_t_params(Type::MonoProj { lhs, rhs }, outer, level)
                 } else {
-                    todo!("{lhs}.{rhs} not found in {}", erg_common::fmt_iter(ctx.rec_sorted_type_ctxs(&lhs)))
+                    todo!(
+                        "{lhs}.{rhs} not found in {}",
+                        erg_common::fmt_iter(ctx.rec_sorted_type_ctxs(&lhs))
+                    )
                 }
             }
             Type::Ref(l) => Ok(Type::ref_(self.eval_t_params(*l, ctx, level)?)),
diff --git a/compiler/erg_compiler/initialize.rs b/compiler/erg_compiler/initialize.rs
index c13007bd..8d51a778 100644
--- a/compiler/erg_compiler/initialize.rs
+++ b/compiler/erg_compiler/initialize.rs
@@ -10,7 +10,7 @@ use Type::*;
 
 use erg_parser::ast::VarName;
 
-use crate::context::{Context, DefaultInfo, ParamSpec, ConstTemplate};
+use crate::context::{ConstTemplate, Context, DefaultInfo, ParamSpec};
 use crate::varinfo::{Mutability, VarInfo, VarKind, Visibility};
 use DefaultInfo::*;
 use Mutability::*;
@@ -66,8 +66,10 @@ impl Context {
                     if let Some(impls) = self.poly_trait_impls.get_mut(impl_trait.name()) {
                         impls.push((t.clone(), impl_trait.clone()));
                     } else {
-                        self.poly_trait_impls
-                            .insert(Str::rc(impl_trait.name()), vec![(t.clone(), impl_trait.clone())]);
+                        self.poly_trait_impls.insert(
+                            Str::rc(impl_trait.name()),
+                            vec![(t.clone(), impl_trait.clone())],
+                        );
                     }
                 }
             }
@@ -153,7 +155,10 @@ impl Context {
         );
         let self_t = mono_q("Self");
         let t = fn0_met(self_t.clone(), Nat);
-        let t = quant(t, set! {subtype(self_t.clone(), poly("Seq", vec![TyParam::erased(Type)]))});
+        let t = quant(
+            t,
+            set! {subtype(self_t.clone(), poly("Seq", vec![TyParam::erased(Type)]))},
+        );
         seq.register_decl("__len__", t, Public);
         let t = Type::fn1_met(self_t.clone(), Nat, mono_q("T"));
         let t = quant(
@@ -169,43 +174,69 @@ impl Context {
         let r_bound = static_instance("R", Type);
         let params = vec![PS::t("R", WithDefault)];
         let ty_params = vec![ty_tp(mono_q("R"))];
-        let mut add = Self::poly_trait("Add", params.clone(), vec![
-            poly("Output", vec![ty_tp(mono_q("R"))]),
-        ], Self::TOP_LEVEL);
-        let self_bound = subtype(
-            mono_q("Self"),
-            poly("Add", ty_params.clone()),
+        let mut add = Self::poly_trait(
+            "Add",
+            params.clone(),
+            vec![poly("Output", vec![ty_tp(mono_q("R"))])],
+            Self::TOP_LEVEL,
+        );
+        let self_bound = subtype(mono_q("Self"), poly("Add", ty_params.clone()));
+        let op_t = fn1_met(
+            poly_q("Self", ty_params.clone()),
+            r.clone(),
+            mono_proj(mono_q("Self"), "AddO"),
         );
-        let op_t = fn1_met(poly_q("Self", ty_params.clone()), r.clone(), mono_proj(mono_q("Self"), "AddO"));
         let op_t = quant(op_t, set! {r_bound.clone(), self_bound});
         add.register_decl("__add__", op_t, Public);
         add.register_decl("AddO", Type, Public);
-        let mut sub = Self::poly_trait("Sub", params.clone(), vec![
-            poly("Output", vec![ty_tp(mono_q("R"))]),
-        ], Self::TOP_LEVEL);
-        let self_bound = subtype(
-            mono_q("Self"),
-            poly("Sub", ty_params.clone()),
+        let mut sub = Self::poly_trait(
+            "Sub",
+            params.clone(),
+            vec![poly("Output", vec![ty_tp(mono_q("R"))])],
+            Self::TOP_LEVEL,
+        );
+        let self_bound = subtype(mono_q("Self"), poly("Sub", ty_params.clone()));
+        let op_t = fn1_met(
+            poly_q("Self", ty_params.clone()),
+            r.clone(),
+            mono_proj(mono_q("Self"), "SubO"),
         );
-        let op_t = fn1_met(poly_q("Self", ty_params.clone()), r.clone(), mono_proj(mono_q("Self"), "SubO"));
         let op_t = quant(op_t, set! {r_bound.clone(), self_bound});
         sub.register_decl("__sub__", op_t, Public);
         sub.register_decl("SubO", Type, Public);
-        let mut mul = Self::poly_trait("Mul", params.clone(), vec![
-            poly("Output", vec![ty_tp(mono_q("R"))]),
-        ], Self::TOP_LEVEL);
-        let op_t = fn1_met(poly("Mul", ty_params.clone()), r.clone(), mono_proj(mono_q("Self"), "MulO"));
+        let mut mul = Self::poly_trait(
+            "Mul",
+            params.clone(),
+            vec![poly("Output", vec![ty_tp(mono_q("R"))])],
+            Self::TOP_LEVEL,
+        );
+        let op_t = fn1_met(
+            poly("Mul", ty_params.clone()),
+            r.clone(),
+            mono_proj(mono_q("Self"), "MulO"),
+        );
         mul.register_decl("__mul__", op_t, Public);
         mul.register_decl("MulO", Type, Public);
-        let mut div = Self::poly_trait("Div", params.clone(), vec![
-            poly("Output", vec![ty_tp(mono_q("R"))]),
-        ], Self::TOP_LEVEL);
-        let op_t = fn1_met(poly("Div", ty_params.clone()), r, mono_proj(mono_q("Self"), "DivO"));
+        let mut div = Self::poly_trait(
+            "Div",
+            params.clone(),
+            vec![poly("Output", vec![ty_tp(mono_q("R"))])],
+            Self::TOP_LEVEL,
+        );
+        let op_t = fn1_met(
+            poly("Div", ty_params.clone()),
+            r,
+            mono_proj(mono_q("Self"), "DivO"),
+        );
         div.register_decl("__div__", op_t, Public);
         div.register_decl("DivO", Type, Public);
         self.register_type(mono("Named"), named, Const);
         self.register_type(poly("Eq", vec![ty_tp(mono_q("R"))]), eq, Const);
-        self.register_type(poly("PartialOrd", vec![ty_tp(mono_q("R"))]), partial_ord, Const);
+        self.register_type(
+            poly("PartialOrd", vec![ty_tp(mono_q("R"))]),
+            partial_ord,
+            Const,
+        );
         self.register_type(mono("Ord"), ord, Const);
         self.register_type(poly("Seq", vec![ty_tp(mono_q("T"))]), seq, Const);
         self.register_type(poly("Input", vec![ty_tp(mono_q("T"))]), input, Const);
@@ -215,12 +246,30 @@ impl Context {
         self.register_type(poly("Mul", ty_params.clone()), mul, Const);
         self.register_type(poly("Div", ty_params), div, Const);
         // self.register_type(mono("Num"), num, Const);
-        self.register_const_param_defaults("Eq", vec![ConstTemplate::Obj(ConstObj::t(mono_q("Self")))]);
-        self.register_const_param_defaults("PartialOrd", vec![ConstTemplate::app("Self", vec![], vec![])]);
-        self.register_const_param_defaults("Add", vec![ConstTemplate::Obj(ConstObj::t(mono_q("Self")))]);
-        self.register_const_param_defaults("Sub", vec![ConstTemplate::Obj(ConstObj::t(mono_q("Self")))]);
-        self.register_const_param_defaults("Mul", vec![ConstTemplate::Obj(ConstObj::t(mono_q("Self")))]);
-        self.register_const_param_defaults("Div", vec![ConstTemplate::Obj(ConstObj::t(mono_q("Self")))]);
+        self.register_const_param_defaults(
+            "Eq",
+            vec![ConstTemplate::Obj(ConstObj::t(mono_q("Self")))],
+        );
+        self.register_const_param_defaults(
+            "PartialOrd",
+            vec![ConstTemplate::app("Self", vec![], vec![])],
+        );
+        self.register_const_param_defaults(
+            "Add",
+            vec![ConstTemplate::Obj(ConstObj::t(mono_q("Self")))],
+        );
+        self.register_const_param_defaults(
+            "Sub",
+            vec![ConstTemplate::Obj(ConstObj::t(mono_q("Self")))],
+        );
+        self.register_const_param_defaults(
+            "Mul",
+            vec![ConstTemplate::Obj(ConstObj::t(mono_q("Self")))],
+        );
+        self.register_const_param_defaults(
+            "Div",
+            vec![ConstTemplate::Obj(ConstObj::t(mono_q("Self")))],
+        );
     }
 
     fn init_builtin_classes(&mut self) {
@@ -394,7 +443,7 @@ impl Context {
                 mono("Mutate"),
                 poly("Seq", vec![ty_tp(Str)]),
                 poly("Add", vec![ty_tp(Str)]),
-                poly("Mul", vec![ty_tp(Nat)])
+                poly("Mul", vec![ty_tp(Nat)]),
             ],
             Self::TOP_LEVEL,
         );
@@ -417,7 +466,13 @@ impl Context {
             vec![PS::t_nd("T"), PS::named_nd("N", Nat)],
             vec![Obj],
             vec![
-                poly("Eq", vec![ty_tp(Type::poly("Array", vec![ty_tp(mono_q("T")), mono_q_tp("N")]))]),
+                poly(
+                    "Eq",
+                    vec![ty_tp(Type::poly(
+                        "Array",
+                        vec![ty_tp(mono_q("T")), mono_q_tp("N")],
+                    ))],
+                ),
                 mono("Mutate"),
                 poly("Seq", vec![ty_tp(mono_q("T"))]),
                 poly("Output", vec![ty_tp(mono_q("T"))]),
@@ -447,10 +502,7 @@ impl Context {
         let mut type_ = Self::mono_class(
             "Type",
             vec![Obj],
-            vec![
-                poly("Eq", vec![ty_tp(Type)]),
-                mono("Named")
-            ],
+            vec![poly("Eq", vec![ty_tp(Type)]), mono("Named")],
             Self::TOP_LEVEL,
         );
         type_.register_impl(
@@ -462,10 +514,7 @@ impl Context {
         let module = Self::mono_class(
             "Module",
             vec![Obj],
-            vec![
-                poly("Eq", vec![ty_tp(Module)]),
-                mono("Named")
-            ],
+            vec![poly("Eq", vec![ty_tp(Module)]), mono("Named")],
             Self::TOP_LEVEL,
         );
         let array_mut_t = Type::poly("Array!", vec![ty_tp(mono_q("T")), mono_q_tp("N")]);
@@ -473,10 +522,7 @@ impl Context {
             "Array!",
             vec![PS::t_nd("T"), PS::named_nd("N", NatMut)],
             vec![poly("Range", vec![ty_tp(mono_q("T")), mono_q_tp("N")]), Obj],
-            vec![
-                mono("Mutate"),
-                poly("Seq", vec![ty_tp(mono_q("T"))]),
-            ],
+            vec![mono("Mutate"), poly("Seq", vec![ty_tp(mono_q("T"))])],
             Self::TOP_LEVEL,
         );
         let t = Type::pr_met(
@@ -500,7 +546,10 @@ impl Context {
             vec![PS::t_nd("T")],
             vec![Obj],
             vec![
-                poly("Eq", vec![ty_tp(Type::poly("Range", vec![ty_tp(mono_q("T"))]))]),
+                poly(
+                    "Eq",
+                    vec![ty_tp(Type::poly("Range", vec![ty_tp(mono_q("T"))]))],
+                ),
                 mono("Mutate"),
                 poly("Seq", vec![ty_tp(mono_q("T"))]),
                 poly("Output", vec![ty_tp(mono_q("T"))]),
@@ -635,16 +684,22 @@ impl Context {
         );
         self.register_impl("__sub__", op_t, Const, Private);
         let op_t = Type::func2(l.clone(), r.clone(), mono_proj(mono_q("L"), "MulO"));
-        let op_t = quant(op_t, set! {
-            static_instance("R", Type),
-            subtype(l.clone(), poly("Mul", params.clone()))
-        });
+        let op_t = quant(
+            op_t,
+            set! {
+                static_instance("R", Type),
+                subtype(l.clone(), poly("Mul", params.clone()))
+            },
+        );
         self.register_impl("__mul__", op_t, Const, Private);
         let op_t = Type::func2(l.clone(), r.clone(), mono_proj(mono_q("L"), "DivO"));
-        let op_t = quant(op_t, set! {
-            static_instance("R", Type),
-            subtype(l, poly("Mul", params.clone()))
-        });
+        let op_t = quant(
+            op_t,
+            set! {
+                static_instance("R", Type),
+                subtype(l, poly("Mul", params.clone()))
+            },
+        );
         self.register_impl("__div__", op_t, Const, Private);
         let m = mono_q("M");
         let op_t = Type::func2(m.clone(), m.clone(), m.clone());
@@ -705,14 +760,8 @@ impl Context {
             params,
             vec![Type::from(&m..=&n)],
             vec![
-                poly(
-                    "Add",
-                    vec![TyParam::from(&o..=&p)],
-                ),
-                poly(
-                    "Sub",
-                    vec![TyParam::from(&o..=&p)],
-                ),
+                poly("Add", vec![TyParam::from(&o..=&p)]),
+                poly("Sub", vec![TyParam::from(&o..=&p)]),
             ],
             Self::TOP_LEVEL,
         );
@@ -728,7 +777,10 @@ impl Context {
             Type::from(m.clone() - p.clone()..=n.clone() - o.clone()),
         );
         interval.register_impl("__sub__", op_t, Const, Public);
-        interval.register_const("AddO", ConstObj::t(Type::from(m.clone() + o.clone()..=n.clone() + p.clone())));
+        interval.register_const(
+            "AddO",
+            ConstObj::t(Type::from(m.clone() + o.clone()..=n.clone() + p.clone())),
+        );
         interval.register_const("SubO", ConstObj::t(Type::from(m - p..=n - o)));
         self.register_patch("Interval", interval, Const);
         // eq.register_impl("__ne__", op_t,         Const, Public);
diff --git a/compiler/erg_compiler/lower.rs b/compiler/erg_compiler/lower.rs
index 5dff2a27..f15d0bde 100644
--- a/compiler/erg_compiler/lower.rs
+++ b/compiler/erg_compiler/lower.rs
@@ -171,12 +171,9 @@ impl ASTLowerer {
             ));
         }
         let obj = self.lower_expr(*call.obj, false)?;
-        let t = self.ctx.get_call_t(
-            &obj,
-            &hir_args.pos_args,
-            &hir_args.kw_args,
-            &self.ctx.name,
-        )?;
+        let t = self
+            .ctx
+            .get_call_t(&obj, &hir_args.pos_args, &hir_args.kw_args, &self.ctx.name)?;
         Ok(hir::Call::new(obj, hir_args, t))
     }
 
diff --git a/src/dummy.rs b/src/dummy.rs
index 3541bd3c..f010f0af 100644
--- a/src/dummy.rs
+++ b/src/dummy.rs
@@ -36,9 +36,11 @@ impl Runnable for DummyVM {
             loop {
                 match TcpStream::connect(&addr) {
                     Ok(stream) => {
-                        stream.set_read_timeout(Some(Duration::from_secs(cfg.py_server_timeout))).unwrap();
-                        break Some(stream)
-                    },
+                        stream
+                            .set_read_timeout(Some(Duration::from_secs(cfg.py_server_timeout)))
+                            .unwrap();
+                        break Some(stream);
+                    }
                     Err(_) => {
                         println!("Retrying to connect to the REPL server...");
                         sleep(Duration::from_millis(500));
@@ -46,7 +48,9 @@ impl Runnable for DummyVM {
                     }
                 }
             }
-        } else { None };
+        } else {
+            None
+        };
         Self {
             compiler: Compiler::new(cfg.copy()),
             cfg,
@@ -115,7 +119,7 @@ impl Runnable for DummyVM {
             Result::Err(e) => {
                 self.finish();
                 panic!("{}", format!("Sending error: {e}"))
-            },
+            }
         };
         if res.ends_with("None") {
             res.truncate(res.len() - 5);