diff --git a/nac3core/src/codegen/expr.rs b/nac3core/src/codegen/expr.rs
index 0a7b5da..5569b30 100644
--- a/nac3core/src/codegen/expr.rs
+++ b/nac3core/src/codegen/expr.rs
@@ -14,7 +14,7 @@ use inkwell::{
 use itertools::{chain, izip, zip, Itertools};
 use rustpython_parser::ast::{self, Boolop, Constant, Expr, ExprKind, Operator, StrRef};
 
-pub fn assert_int_val<'ctx>(val: BasicValueEnum<'ctx>) -> IntValue<'ctx> {
+pub fn assert_int_val(val: BasicValueEnum<'_>) -> IntValue<'_> {
     if let BasicValueEnum::IntValue(v) = val {
         v
     } else {
@@ -22,7 +22,7 @@ pub fn assert_int_val<'ctx>(val: BasicValueEnum<'ctx>) -> IntValue<'ctx> {
     }
 }
 
-pub fn assert_pointer_val<'ctx>(val: BasicValueEnum<'ctx>) -> PointerValue<'ctx> {
+pub fn assert_pointer_val(val: BasicValueEnum<'_>) -> PointerValue<'_> {
     if let BasicValueEnum::PointerValue(v) = val {
         v
     } else {
@@ -189,7 +189,7 @@ impl<'ctx, 'a> CodeGenContext<'ctx, 'a> {
                             .args
                             .iter()
                             .map(|arg| FuncArg {
-                                name: arg.name.clone(),
+                                name: arg.name,
                                 ty: unifier.copy_from(&mut self.unifier, arg.ty, &mut type_cache),
                                 default_value: arg.default_value.clone(),
                             })
@@ -645,7 +645,7 @@ impl<'ctx, 'a> CodeGenContext<'ctx, 'a> {
                     args.iter().map(|arg| (None, self.gen_expr(arg).unwrap())).collect_vec();
                 let kw_iter = keywords.iter().map(|kw| {
                     (
-                        Some(kw.node.arg.as_ref().unwrap().clone()),
+                        Some(*kw.node.arg.as_ref().unwrap()),
                         self.gen_expr(&kw.node.value).unwrap(),
                     )
                 });
diff --git a/nac3core/src/codegen/mod.rs b/nac3core/src/codegen/mod.rs
index b32733d..a78f1a4 100644
--- a/nac3core/src/codegen/mod.rs
+++ b/nac3core/src/codegen/mod.rs
@@ -320,7 +320,7 @@ pub fn gen_func<'ctx>(
             &arg.name.to_string(),
         );
         builder.build_store(alloca, param);
-        var_assignment.insert(arg.name.clone(), alloca);
+        var_assignment.insert(arg.name, alloca);
     }
     builder.build_unconditional_branch(body_bb);
     builder.position_at_end(body_bb);
diff --git a/nac3core/src/codegen/stmt.rs b/nac3core/src/codegen/stmt.rs
index b8ce89a..69d9735 100644
--- a/nac3core/src/codegen/stmt.rs
+++ b/nac3core/src/codegen/stmt.rs
@@ -25,7 +25,7 @@ impl<'ctx, 'a> CodeGenContext<'ctx, 'a> {
             ExprKind::Name { id, .. } => {
                 self.var_assignment.get(id).cloned().unwrap_or_else(|| {
                     let ptr = self.gen_var(pattern.custom.unwrap());
-                    self.var_assignment.insert(id.clone(), ptr);
+                    self.var_assignment.insert(*id, ptr);
                     ptr
                 })
             }
diff --git a/nac3core/src/location.rs b/nac3core/src/location.rs
index 424336f..6e9021c 100644
--- a/nac3core/src/location.rs
+++ b/nac3core/src/location.rs
@@ -10,15 +10,12 @@ pub enum Location {
     Builtin,
 }
 
+#[derive(Default)]
 pub struct FileRegistry {
     files: Vec<String>,
 }
 
 impl FileRegistry {
-    pub fn new() -> FileRegistry {
-        FileRegistry { files: Vec::new() }
-    }
-
     pub fn add_file(&mut self, path: &str) -> FileID {
         let index = self.files.len() as u32;
         self.files.push(path.to_owned());
diff --git a/nac3core/src/toplevel/composer.rs b/nac3core/src/toplevel/composer.rs
index dc67db4..f57016f 100644
--- a/nac3core/src/toplevel/composer.rs
+++ b/nac3core/src/toplevel/composer.rs
@@ -89,8 +89,8 @@ impl TopLevelComposer {
 
         for (name, sig) in builtins {
             let fun_sig = unifier.add_ty(TypeEnum::TFunc(RefCell::new(sig)));
-            built_in_ty.insert(name.clone(), fun_sig);
-            built_in_id.insert(name.clone(), DefinitionId(definition_ast_list.len()));
+            built_in_ty.insert(name, fun_sig);
+            built_in_id.insert(name, DefinitionId(definition_ast_list.len()));
             definition_ast_list.push((
                 Arc::new(RwLock::new(TopLevelDef::Function {
                     name: name.into(),
@@ -161,7 +161,7 @@ impl TopLevelComposer {
                     return Err("duplicate definition of class".into());
                 }
 
-                let class_name = class_name.clone();
+                let class_name = *class_name;
                 let class_def_id = self.definition_ast_list.len();
 
                 // since later when registering class method, ast will still be used,
@@ -221,10 +221,10 @@ impl TopLevelComposer {
                         // dummy method define here
                         let dummy_method_type = self.unifier.get_fresh_var();
                         class_method_name_def_ids.push((
-                            method_name.clone(),
+                            *method_name,
                             RwLock::new(Self::make_top_level_function_def(
                                 global_class_method_name,
-                                method_name.clone(),
+                                *method_name,
                                 // later unify with parsed type
                                 dummy_method_type.0,
                                 resolver.clone(),
@@ -246,7 +246,7 @@ impl TopLevelComposer {
                 for (name, _, id, ty, ..) in &class_method_name_def_ids {
                     let mut class_def = class_def_ast.0.write();
                     if let TopLevelDef::Class { methods, .. } = class_def.deref_mut() {
-                        methods.push((name.clone(), *ty, *id));
+                        methods.push((*name, *ty, *id));
                         self.method_class.insert(*id, DefinitionId(class_def_id));
                     } else {
                         unreachable!()
@@ -705,7 +705,7 @@ impl TopLevelComposer {
                                 )?;
 
                                 Ok(FuncArg {
-                                    name: x.node.arg.clone(),
+                                    name: x.node.arg,
                                     ty,
                                     default_value: Default::default(),
                                 })
@@ -809,7 +809,7 @@ impl TopLevelComposer {
             if let ast::StmtKind::ClassDef { name, bases, body, .. } = &class_ast {
                 (
                     *object_id,
-                    name.clone(),
+                    *name,
                     bases,
                     body,
                     ancestors,
@@ -851,7 +851,7 @@ impl TopLevelComposer {
                         let mut defined_paramter_name: HashSet<_> = HashSet::new();
                         let zelf: StrRef = "self".into();
                         let have_unique_fuction_parameter_name = args.args.iter().all(|x| {
-                            defined_paramter_name.insert(x.node.arg.clone())
+                            defined_paramter_name.insert(x.node.arg)
                                 && (!keyword_list.contains(&x.node.arg) || x.node.arg == zelf)
                         });
                         if !have_unique_fuction_parameter_name {
@@ -1310,7 +1310,7 @@ impl TopLevelComposer {
                             let unifier = &mut self.unifier;
                             args.iter()
                                 .map(|a| FuncArg {
-                                    name: a.name.clone(),
+                                    name: a.name,
                                     ty: unifier.subst(a.ty, &subst).unwrap_or(a.ty),
                                     default_value: a.default_value.clone(),
                                 })
@@ -1328,7 +1328,7 @@ impl TopLevelComposer {
                             if self_type.is_some() {
                                 result.insert("self".into());
                             }
-                            result.extend(inst_args.iter().map(|x| x.name.clone()));
+                            result.extend(inst_args.iter().map(|x| x.name));
                             result
                         };
                         let mut calls: HashMap<CodeLocation, CallId> = HashMap::new();
@@ -1356,7 +1356,7 @@ impl TopLevelComposer {
                                 if let Some(self_ty) = self_type {
                                     result.insert("self".into(), self_ty);
                                 }
-                                result.extend(inst_args.iter().map(|x| (x.name.clone(), x.ty)));
+                                result.extend(inst_args.iter().map(|x| (x.name, x.ty)));
                                 result
                             },
                             primitives: &self.primitives_ty,
diff --git a/nac3core/src/toplevel/helper.rs b/nac3core/src/toplevel/helper.rs
index 3d585c9..411ec67 100644
--- a/nac3core/src/toplevel/helper.rs
+++ b/nac3core/src/toplevel/helper.rs
@@ -296,7 +296,7 @@ impl TopLevelComposer {
                         if let ast::ExprKind::Attribute { value, attr, .. } = &t.node {
                             if let ast::ExprKind::Name { id, .. } = &value.node {
                                 if id == &"self".into() {
-                                    result.insert(attr.clone());
+                                    result.insert(*attr);
                                 }
                             }
                         }
diff --git a/nac3core/src/typecheck/function_check.rs b/nac3core/src/typecheck/function_check.rs
index 6c2085a..fce0589 100644
--- a/nac3core/src/typecheck/function_check.rs
+++ b/nac3core/src/typecheck/function_check.rs
@@ -14,7 +14,7 @@ impl<'a> Inferencer<'a> {
         match &pattern.node {
             ExprKind::Name { id, .. } => {
                 if !defined_identifiers.contains(id) {
-                    defined_identifiers.insert(id.clone());
+                    defined_identifiers.insert(*id);
                 }
                 Ok(())
             }
@@ -58,7 +58,7 @@ impl<'a> Inferencer<'a> {
             ExprKind::Name { id, .. } => {
                 if !defined_identifiers.contains(id) {
                     if self.function_data.resolver.get_identifier_def(*id).is_some() {
-                        defined_identifiers.insert(id.clone());
+                        defined_identifiers.insert(*id);
                     } else {
                         return Err(format!(
                             "unknown identifier {} (use before def?) at {}",
@@ -107,7 +107,7 @@ impl<'a> Inferencer<'a> {
                 let mut defined_identifiers = defined_identifiers.clone();
                 for arg in args.args.iter() {
                     if !defined_identifiers.contains(&arg.node.arg) {
-                        defined_identifiers.insert(arg.node.arg.clone());
+                        defined_identifiers.insert(arg.node.arg);
                     }
                 }
                 self.check_expr(body, &mut defined_identifiers)?;
@@ -167,7 +167,7 @@ impl<'a> Inferencer<'a> {
 
                 for ident in body_identifiers.iter() {
                     if !defined_identifiers.contains(ident) && orelse_identifiers.contains(ident) {
-                        defined_identifiers.insert(ident.clone());
+                        defined_identifiers.insert(*ident);
                     }
                 }
                 Ok(body_returned && orelse_returned)
diff --git a/nac3core/src/typecheck/type_inferencer/mod.rs b/nac3core/src/typecheck/type_inferencer/mod.rs
index bc761d7..110acf4 100644
--- a/nac3core/src/typecheck/type_inferencer/mod.rs
+++ b/nac3core/src/typecheck/type_inferencer/mod.rs
@@ -164,7 +164,7 @@ impl<'a> fold::Fold<()> for Inferencer<'a> {
             ast::ExprKind::Name { id, .. } => {
                 if !self.defined_identifiers.contains(id) {
                     if self.function_data.resolver.get_identifier_def(*id).is_some() {
-                        self.defined_identifiers.insert(id.clone());
+                        self.defined_identifiers.insert(*id);
                     } else {
                         return Err(format!(
                             "unknown identifier {} (use before def?) at {}",
@@ -220,7 +220,7 @@ impl<'a> Inferencer<'a> {
         match &pattern.node {
             ExprKind::Name { id, .. } => {
                 if !self.defined_identifiers.contains(id) {
-                    self.defined_identifiers.insert(id.clone());
+                    self.defined_identifiers.insert(*id);
                 }
                 Ok(())
             }
@@ -312,13 +312,13 @@ impl<'a> Inferencer<'a> {
         for arg in args.args.iter() {
             let name = &arg.node.arg;
             if !defined_identifiers.contains(name) {
-                defined_identifiers.insert(name.clone());
+                defined_identifiers.insert(*name);
             }
         }
         let fn_args: Vec<_> = args
             .args
             .iter()
-            .map(|v| (v.node.arg.clone(), self.unifier.get_fresh_var().0))
+            .map(|v| (v.node.arg, self.unifier.get_fresh_var().0))
             .collect();
         let mut variable_mapping = self.variable_mapping.clone();
         variable_mapping.extend(fn_args.iter().cloned());
@@ -337,7 +337,7 @@ impl<'a> Inferencer<'a> {
         let fun = FunSignature {
             args: fn_args
                 .iter()
-                .map(|(k, ty)| FuncArg { name: k.clone(), ty: *ty, default_value: None })
+                .map(|(k, ty)| FuncArg { name: *k, ty: *ty, default_value: None })
                 .collect(),
             ret,
             vars: Default::default(),
@@ -503,7 +503,7 @@ impl<'a> Inferencer<'a> {
                     posargs: args.iter().map(|v| v.custom.unwrap()).collect(),
                     kwargs: keywords
                         .iter()
-                        .map(|v| (v.node.arg.as_ref().unwrap().clone(), v.custom.unwrap()))
+                        .map(|v| (*v.node.arg.as_ref().unwrap(), v.custom.unwrap()))
                         .collect(),
                     fun: RefCell::new(None),
                     ret: sign.ret,
@@ -531,7 +531,7 @@ impl<'a> Inferencer<'a> {
             posargs: args.iter().map(|v| v.custom.unwrap()).collect(),
             kwargs: keywords
                 .iter()
-                .map(|v| (v.node.arg.as_ref().unwrap().clone(), v.custom.unwrap()))
+                .map(|v| (*v.node.arg.as_ref().unwrap(), v.custom.unwrap()))
                 .collect(),
             fun: RefCell::new(None),
             ret,
diff --git a/nac3core/src/typecheck/typedef/mod.rs b/nac3core/src/typecheck/typedef/mod.rs
index fbbf776..70c9984 100644
--- a/nac3core/src/typecheck/typedef/mod.rs
+++ b/nac3core/src/typecheck/typedef/mod.rs
@@ -107,6 +107,12 @@ pub struct Unifier {
     var_id: u32,
 }
 
+impl Default for Unifier {
+    fn default() -> Self {
+        Unifier::new()
+    }
+}
+
 impl Unifier {
     /// Get an empty unifier
     pub fn new() -> Unifier {
@@ -454,7 +460,7 @@ impl Unifier {
                             if let Some(ty) = fields2.get(key) {
                                 self.unify(*ty, *value)?;
                             } else {
-                                fields2.insert(key.clone(), *value);
+                                fields2.insert(*key, *value);
                             }
                         }
                     }
diff --git a/nac3core/src/typecheck/unification_table.rs b/nac3core/src/typecheck/unification_table.rs
index 619c23a..b126e09 100644
--- a/nac3core/src/typecheck/unification_table.rs
+++ b/nac3core/src/typecheck/unification_table.rs
@@ -12,6 +12,12 @@ pub struct UnificationTable<V> {
     values: Vec<Option<V>>,
 }
 
+impl<V> Default for UnificationTable<V> {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
 impl<V> UnificationTable<V> {
     pub fn new() -> UnificationTable<V> {
         UnificationTable { parents: Vec::new(), ranks: Vec::new(), values: Vec::new() }
diff --git a/nac3standalone/src/main.rs b/nac3standalone/src/main.rs
index ec4c0d7..d48f82b 100644
--- a/nac3standalone/src/main.rs
+++ b/nac3standalone/src/main.rs
@@ -78,7 +78,7 @@ fn main() {
             "__main__".into(),
         ).unwrap();
 
-        internal_resolver.add_id_def(name.clone(), def_id);
+        internal_resolver.add_id_def(name, def_id);
         if let Some(ty) = ty {
             internal_resolver.add_id_type(name, ty);
         }