diff --git a/compiler/erg_common/codeobj.rs b/compiler/erg_common/codeobj.rs
index 8e8b3e64..913581fe 100644
--- a/compiler/erg_common/codeobj.rs
+++ b/compiler/erg_common/codeobj.rs
@@ -317,7 +317,7 @@ impl CodeObj {
     ) -> std::io::Result<()> {
         let mut file = File::create(path)?;
         let mut bytes = Vec::with_capacity(16);
-        let python_ver = python_ver.unwrap_or_else(|| detect_magic_number());
+        let python_ver = python_ver.unwrap_or_else(detect_magic_number);
         bytes.append(&mut get_magic_num_bytes(python_ver).to_vec());
         bytes.append(&mut vec![0; 4]); // padding
         bytes.append(&mut get_timestamp_bytes().to_vec());
diff --git a/compiler/erg_common/color.rs b/compiler/erg_common/color.rs
index 40052884..3fb6b402 100644
--- a/compiler/erg_common/color.rs
+++ b/compiler/erg_common/color.rs
@@ -1,9 +1,9 @@
 //! Escape sequences change the color of the terminal
 
-pub const RESET: &'static str = "\x1b[m";
-pub const DEEP_RED: &'static str = "\x1b[31m";
-pub const RED: &'static str = "\x1b[91m";
-pub const GREEN: &'static str = "\x1b[92m";
-pub const YELLOW: &'static str = "\x1b[93m";
-pub const BLUE: &'static str = "\x1b[94m";
-pub const CYAN: &'static str = "\x1b[96m";
+pub const RESET: &str = "\x1b[m";
+pub const DEEP_RED: &str = "\x1b[31m";
+pub const RED: &str = "\x1b[91m";
+pub const GREEN: &str = "\x1b[92m";
+pub const YELLOW: &str = "\x1b[93m";
+pub const BLUE: &str = "\x1b[94m";
+pub const CYAN: &str = "\x1b[96m";
diff --git a/compiler/erg_common/combinations.rs b/compiler/erg_common/combinations.rs
index 6dc55cdd..1194ba2f 100644
--- a/compiler/erg_common/combinations.rs
+++ b/compiler/erg_common/combinations.rs
@@ -44,7 +44,7 @@ where
     type Item = Vec<I::Item>;
     fn next(&mut self) -> Option<Self::Item> {
         if let Some(i) = self.combinations.next() {
-            return Some(i);
+            Some(i)
         } else {
             self.combinations.reset(self.combinations.k() + 1);
             self.len -= 1;
diff --git a/compiler/erg_common/config.rs b/compiler/erg_common/config.rs
index 8ac6238b..6445c552 100644
--- a/compiler/erg_common/config.rs
+++ b/compiler/erg_common/config.rs
@@ -96,7 +96,7 @@ impl Input {
             },
             Self::Pipe(s) | Self::Str(s) => s.split('\n').collect::<Vec<_>>()
                 [ln_begin - 1..=ln_end - 1]
-                .into_iter()
+                .iter()
                 .map(|s| Str::rc(*s))
                 .collect(),
             Self::REPL => stdin::reread_lines(ln_begin, ln_end),
diff --git a/compiler/erg_common/deserialize.rs b/compiler/erg_common/deserialize.rs
index 6d42aede..a339caec 100644
--- a/compiler/erg_common/deserialize.rs
+++ b/compiler/erg_common/deserialize.rs
@@ -84,6 +84,7 @@ impl DeserializeError {
 
 pub type DeserializeResult<T> = Result<T, DeserializeError>;
 
+#[derive(Default)]
 pub struct Deserializer {
     str_cache: Cache<str>,
     arr_cache: Cache<[ValueObj]>,
@@ -107,7 +108,7 @@ impl Deserializer {
             process::exit(1);
         };
         let codeobj =
-            CodeObj::from_pyc(&filename[..]).expect(&format!("failed to deserialize {filename}"));
+            CodeObj::from_pyc(&filename[..]).unwrap_or_else(|_| panic!("failed to deserialize {filename}"));
         println!("{}", codeobj.code_info());
     }
 
@@ -241,7 +242,7 @@ impl Deserializer {
     ) -> DeserializeResult<Vec<ValueObj>> {
         match self.deserialize_const(v, python_ver)? {
             ValueObj::Array(arr) => Ok(arr.to_vec()),
-            other => Err(DeserializeError::type_error(&Type::Str, &other.ref_t())),
+            other => Err(DeserializeError::type_error(&Type::Str, other.ref_t())),
         }
     }
 
@@ -252,18 +253,18 @@ impl Deserializer {
     ) -> DeserializeResult<RcArray<ValueObj>> {
         match self.deserialize_const(v, python_ver)? {
             ValueObj::Array(arr) => Ok(arr),
-            other => Err(DeserializeError::type_error(&Type::Str, &other.ref_t())),
+            other => Err(DeserializeError::type_error(&Type::Str, other.ref_t())),
         }
     }
 
     pub fn array_into_const(&mut self, arr: &[ValueObj]) -> ValueObj {
-        self.get_cached_arr(&arr)
+        self.get_cached_arr(arr)
     }
 
     pub fn try_into_str(&mut self, c: ValueObj) -> DeserializeResult<Str> {
         match c {
             ValueObj::Str(s) => Ok(s),
-            other => Err(DeserializeError::type_error(&Type::Str, &other.ref_t())),
+            other => Err(DeserializeError::type_error(&Type::Str, other.ref_t())),
         }
     }
 
@@ -275,14 +276,14 @@ impl Deserializer {
         match self.deserialize_const(v, python_ver)? {
             ValueObj::Array(arr) => {
                 let mut strs = Vec::with_capacity(arr.len());
-                for c in arr.to_vec().into_iter() {
+                for c in arr.iter().cloned() {
                     strs.push(self.try_into_str(c)?);
                 }
                 Ok(strs)
             }
             other => Err(DeserializeError::type_error(
                 &Type::array(Type::Str, TyParam::erased(Type::Nat)),
-                &other.ref_t(),
+                other.ref_t(),
             )),
         }
     }
@@ -290,7 +291,7 @@ impl Deserializer {
     pub fn deserialize_str(&mut self, v: &mut Vec<u8>, python_ver: u32) -> DeserializeResult<Str> {
         match self.deserialize_const(v, python_ver)? {
             ValueObj::Str(s) => Ok(s),
-            other => Err(DeserializeError::type_error(&Type::Str, &other.ref_t())),
+            other => Err(DeserializeError::type_error(&Type::Str, other.ref_t())),
         }
     }
 
diff --git a/compiler/erg_common/dict.rs b/compiler/erg_common/dict.rs
index d0acb8fb..2cd4c824 100644
--- a/compiler/erg_common/dict.rs
+++ b/compiler/erg_common/dict.rs
@@ -84,6 +84,11 @@ impl<K, V> Dict<K, V> {
         self.dict.len()
     }
 
+    #[inline]
+    pub fn is_empty(&self) -> bool {
+        self.dict.is_empty()
+    }
+
     #[inline]
     pub fn capacity(&self) -> usize {
         self.dict.capacity()
diff --git a/compiler/erg_common/error.rs b/compiler/erg_common/error.rs
index 20760019..31409fc0 100644
--- a/compiler/erg_common/error.rs
+++ b/compiler/erg_common/error.rs
@@ -359,7 +359,7 @@ pub trait ErrorDisplay {
     fn write_to_stderr(&self) {
         let mut writer = BufWriter::new(stderr());
         writer
-            .write(
+            .write_all(
                 format!(
                     "{}{}{}: {}{}\n",
                     self.format_header(),
@@ -379,9 +379,9 @@ pub trait ErrorDisplay {
 
     /// fmt::Display実装用
     fn format(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(
+        writeln!(
             f,
-            "{}{}{}: {}{}\n",
+            "{}{}{}: {}{}",
             self.format_header(),
             self.format_code_and_pointer(),
             self.core().kind,
diff --git a/compiler/erg_common/levenshtein.rs b/compiler/erg_common/levenshtein.rs
index 0ef1b671..385df8a1 100644
--- a/compiler/erg_common/levenshtein.rs
+++ b/compiler/erg_common/levenshtein.rs
@@ -26,5 +26,5 @@ pub fn levenshtein(lhs: &str, rhs: &str) -> usize {
             .unwrap();
         }
     }
-    return table[l_len][r_len];
+    table[l_len][r_len]
 }
diff --git a/compiler/erg_common/lib.rs b/compiler/erg_common/lib.rs
index 8b3132f6..ebd17ad3 100644
--- a/compiler/erg_common/lib.rs
+++ b/compiler/erg_common/lib.rs
@@ -85,7 +85,7 @@ pub fn fmt_iter_split_with<T: fmt::Display, I: Iterator<Item = T>>(i: I, splitte
 
 pub fn fmt_indent(s: String, depth: usize) -> String {
     let indent = " ".repeat(depth);
-    s.split("\n").map(|s| indent.clone() + s).collect()
+    s.split('\n').map(|s| indent.clone() + s).collect()
 }
 
 pub fn get_hash<T: std::hash::Hash>(t: &T) -> usize {
diff --git a/compiler/erg_common/python_util.rs b/compiler/erg_common/python_util.rs
index 3e964ea8..95ad997d 100644
--- a/compiler/erg_common/python_util.rs
+++ b/compiler/erg_common/python_util.rs
@@ -13,9 +13,9 @@ pub fn which_python() -> String {
         .expect("python not found");
     let res = String::from_utf8(out.stdout)
         .unwrap()
-        .replace("\n", "")
-        .replace("\r", "");
-    if res == "" {
+        .replace('\n', "")
+        .replace('\r', "");
+    if res.is_empty() {
         panic!("python not found");
     }
     res
diff --git a/compiler/erg_common/str.rs b/compiler/erg_common/str.rs
index 872ba230..654810e5 100644
--- a/compiler/erg_common/str.rs
+++ b/compiler/erg_common/str.rs
@@ -17,7 +17,7 @@ pub enum Str {
 impl PartialEq for Str {
     #[inline]
     fn eq(&self, other: &Str) -> bool {
-        &self[..] == &other[..]
+        self[..] == other[..]
     }
 }
 
diff --git a/compiler/erg_common/traits.rs b/compiler/erg_common/traits.rs
index a3150a4a..f98ef977 100644
--- a/compiler/erg_common/traits.rs
+++ b/compiler/erg_common/traits.rs
@@ -345,8 +345,8 @@ pub trait Runnable: Sized {
                 let output = stdout();
                 let mut output = BufWriter::new(output.lock());
                 log!(f output, "{GREEN}[DEBUG] The REPL has started.{RESET}\n");
-                output.write(instance.start_message().as_bytes()).unwrap();
-                output.write(instance.ps1().as_bytes()).unwrap();
+                output.write_all(instance.start_message().as_bytes()).unwrap();
+                output.write_all(instance.ps1().as_bytes()).unwrap();
                 output.flush().unwrap();
                 let mut lines = String::new();
                 loop {
@@ -359,20 +359,20 @@ pub trait Runnable: Sized {
                     lines.push_str(&line);
                     if expect_block(&line) || line.starts_with(' ') {
                         lines += "\n";
-                        output.write(instance.ps2().as_bytes()).unwrap();
+                        output.write_all(instance.ps2().as_bytes()).unwrap();
                         output.flush().unwrap();
                         continue;
                     }
                     match instance.eval(mem::take(&mut lines).into()) {
                         Ok(out) => {
-                            output.write((out + "\n").as_bytes()).unwrap();
+                            output.write_all((out + "\n").as_bytes()).unwrap();
                             output.flush().unwrap();
                         }
                         Err(e) => {
                             e.fmt_all_stderr();
                         }
                     }
-                    output.write(instance.ps1().as_bytes()).unwrap();
+                    output.write_all(instance.ps1().as_bytes()).unwrap();
                     output.flush().unwrap();
                     instance.clear();
                 }
diff --git a/compiler/erg_common/ty.rs b/compiler/erg_common/ty.rs
index 9faf64ea..4ea2bc7b 100644
--- a/compiler/erg_common/ty.rs
+++ b/compiler/erg_common/ty.rs
@@ -293,14 +293,14 @@ impl<T: Clone + HasLevel> Free<T> {
         self.0
             .borrow()
             .constraint()
-            .and_then(|c| c.typ().map(|t| t.clone()))
+            .and_then(|c| c.typ().cloned())
     }
 
     pub fn subtype_of(&self) -> Option<Type> {
         self.0
             .borrow()
             .constraint()
-            .and_then(|c| c.super_type().map(|t| t.clone()))
+            .and_then(|c| c.super_type().cloned())
     }
 
     pub fn is_unbound(&self) -> bool {
diff --git a/compiler/erg_common/value.rs b/compiler/erg_common/value.rs
index 16ec77cf..bf966db7 100644
--- a/compiler/erg_common/value.rs
+++ b/compiler/erg_common/value.rs
@@ -17,7 +17,7 @@ use crate::{RcArray, Str};
 
 /// 値オブジェクト
 /// コンパイル時評価ができ、シリアライズも可能
-#[derive(Clone, PartialEq)]
+#[derive(Clone)]
 pub enum ValueObj {
     Int(i32),
     Nat(u64),
@@ -92,6 +92,29 @@ impl Neg for ValueObj {
     }
 }
 
+impl PartialEq for ValueObj {
+    fn eq(&self, other: &ValueObj) -> bool {
+        match (self, other) {
+            (Self::Int(i), Self::Int(j)) => i == j,
+            (Self::Nat(n), Self::Nat(m)) => n == m,
+            (Self::Float(fl), Self::Float(fr)) => fl == fr,
+            (Self::Str(s), Self::Str(t)) => s == t,
+            (Self::True, Self::True) => true,
+            (Self::False, Self::False) => true,
+            (Self::Array(arr), Self::Array(arr2)) => arr == arr2,
+            (Self::Dict(dict), Self::Dict(dict2)) => dict == dict2,
+            (Self::Code(code), Self::Code(code2)) => code == code2,
+            (Self::None, Self::None) => true,
+            (Self::Ellipsis, Self::Ellipsis) => true,
+            (Self::NotImplemented, Self::NotImplemented) => true,
+            (Self::NegInf, Self::NegInf) => true,
+            (Self::Inf, Self::Inf) => true,
+            (Self::Illegal, Self::Illegal) => true,
+            _ => false,
+        }
+    }
+}
+
 // FIXME:
 impl Hash for ValueObj {
     fn hash<H: Hasher>(&self, state: &mut H) {