diff --git a/crates/erg_compiler/context/initialize/mod.rs b/crates/erg_compiler/context/initialize/mod.rs
index cba74156d..f3ec9aba9 100644
--- a/crates/erg_compiler/context/initialize/mod.rs
+++ b/crates/erg_compiler/context/initialize/mod.rs
@@ -34,7 +34,8 @@ use crate::ty::constructors::*;
 use crate::ty::free::Constraint;
 use crate::ty::value::ValueObj;
 use crate::ty::{
-    BuiltinConstSubr, ConstSubr, GenConstSubr, ParamTy, Predicate, TyParam, Type, Visibility,
+    BuiltinConstSubr, ClosureData, ConstSubr, GenConstSubr, ParamTy, Predicate, TyParam, Type,
+    Visibility,
 };
 use crate::varinfo::{AbsLocation, Mutability, VarInfo, VarKind};
 use Mutability::*;
@@ -798,28 +799,33 @@ impl Context {
                 .iter()
                 .filter_map(|ps| (!ps.has_default()).then_some(ParamTy::from(ps)))
                 .collect::<Vec<_>>();
-            let num_nd = nd_params.len();
             let d_params = ctx
                 .params_spec
                 .iter()
                 .filter_map(|ps| ps.has_default().then_some(ParamTy::from(ps)))
                 .collect::<Vec<_>>();
-            let num_d = d_params.len();
-            let meta_t =
-                func(nd_params, None, d_params.clone(), v_enum(set! { ret_val })).quantify();
-            let subr = move |args, _ctx: &Context| {
+            let meta_t = func(
+                nd_params.clone(),
+                None,
+                d_params.clone(),
+                v_enum(set! { ret_val }),
+            )
+            .quantify();
+            let subr = move |data: ClosureData, args, _ctx: &Context| {
                 let passed = Vec::<TyParam>::from(args);
-                let lack = num_nd + num_d - passed.len();
-                let erased = d_params
+                let lack = data.nd_params.len() + data.d_params.len() - passed.len();
+                let erased = data
+                    .d_params
                     .clone()
                     .into_iter()
                     .take(lack)
                     .map(|pt| TyParam::erased(pt.typ().clone()));
                 let params = passed.into_iter().chain(erased).collect::<Vec<_>>();
-                Ok(ValueObj::builtin_type(poly(qual_name.clone(), params)))
+                Ok(ValueObj::builtin_type(poly(data.qual_name, params)))
             };
             let subr = ConstSubr::Gen(GenConstSubr::new(
                 t.local_name(),
+                ClosureData::new(nd_params, d_params, qual_name),
                 subr,
                 meta_t.clone(),
                 Some(t.clone()),
diff --git a/crates/erg_compiler/ty/const_subr.rs b/crates/erg_compiler/ty/const_subr.rs
index 42928b133..bc1ef6534 100644
--- a/crates/erg_compiler/ty/const_subr.rs
+++ b/crates/erg_compiler/ty/const_subr.rs
@@ -1,5 +1,4 @@
 use std::fmt;
-use std::sync::Arc;
 
 use erg_common::dict::Dict;
 #[allow(unused_imports)]
@@ -10,7 +9,7 @@ use erg_parser::ast::{Block, ConstBlock, Params};
 
 use super::constructors::subr_t;
 use super::value::{EvalValueResult, ValueObj};
-use super::{Predicate, TyParam, Type};
+use super::{ParamTy, Predicate, TyParam, Type};
 
 use crate::context::Context;
 
@@ -122,18 +121,33 @@ impl BuiltinConstSubr {
     }
 }
 
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct ClosureData {
+    pub(crate) nd_params: Vec<ParamTy>,
+    pub(crate) d_params: Vec<ParamTy>,
+    pub(crate) qual_name: Str,
+}
+
+impl ClosureData {
+    pub const fn new(nd_params: Vec<ParamTy>, d_params: Vec<ParamTy>, qual_name: Str) -> Self {
+        Self {
+            nd_params,
+            d_params,
+            qual_name,
+        }
+    }
+}
+
 #[allow(clippy::type_complexity)]
 #[derive(Clone)]
 pub struct GenConstSubr {
     name: Str,
-    subr: Arc<dyn Fn(ValueArgs, &Context) -> EvalValueResult<ValueObj>>,
+    data: ClosureData,
+    subr: fn(ClosureData, ValueArgs, &Context) -> EvalValueResult<ValueObj>,
     sig_t: Type,
     as_type: Option<Type>,
 }
 
-unsafe impl Send for GenConstSubr {}
-unsafe impl Sync for GenConstSubr {}
-
 impl std::fmt::Debug for GenConstSubr {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         f.debug_struct("BuiltinConstSubr")
@@ -167,20 +181,22 @@ impl fmt::Display for GenConstSubr {
 impl GenConstSubr {
     pub fn new<S: Into<Str>>(
         name: S,
-        subr: impl Fn(ValueArgs, &Context) -> EvalValueResult<ValueObj> + 'static,
+        data: ClosureData,
+        subr: fn(ClosureData, ValueArgs, &Context) -> EvalValueResult<ValueObj>,
         sig_t: Type,
         as_type: Option<Type>,
     ) -> Self {
         Self {
             name: name.into(),
-            subr: Arc::new(subr),
+            data,
+            subr,
             sig_t,
             as_type,
         }
     }
 
     pub fn call(&self, args: ValueArgs, ctx: &Context) -> EvalValueResult<ValueObj> {
-        (self.subr)(args, ctx)
+        (self.subr)(self.data.clone(), args, ctx)
     }
 }