diff --git a/src/ast/expression/if_expression.rs b/src/ast/expression/if_expression.rs
index 3a07364..613955e 100644
--- a/src/ast/expression/if_expression.rs
+++ b/src/ast/expression/if_expression.rs
@@ -42,8 +42,8 @@ impl If {
         &mut self.consequence
     }
 
-    pub fn condition_mut(&mut self) -> &mut Box<Expression> {
-        &mut self.condition
+    pub fn update_expression(&mut self, expression: Expression) {
+        self.condition = Box::new(expression);
     }
 }
 
diff --git a/src/ast/expression/infix.rs b/src/ast/expression/infix.rs
index 6d9faaa..4d8cc87 100644
--- a/src/ast/expression/infix.rs
+++ b/src/ast/expression/infix.rs
@@ -36,8 +36,8 @@ impl Infix {
         &self.right
     }
 
-    pub fn right_mut(&mut self) -> &mut Box<Expression> {
-        &mut self.right
+    pub fn update_expression(&mut self, right: Expression) {
+        self.right = Box::new(right);
     }
 }
 
diff --git a/src/ast/expression/integer.rs b/src/ast/expression/integer.rs
index 5c3744c..030b3a5 100644
--- a/src/ast/expression/integer.rs
+++ b/src/ast/expression/integer.rs
@@ -27,8 +27,8 @@ impl IntegerLiteral {
         self.value
     }
 
-    pub fn value_mut(&mut self) -> &mut isize {
-        &mut self.value
+    pub fn update_value(&mut self, value: isize) {
+        self.value = value;
     }
 }
 
diff --git a/src/ast/expression/prefix.rs b/src/ast/expression/prefix.rs
index 8f2ae3e..14ebabe 100644
--- a/src/ast/expression/prefix.rs
+++ b/src/ast/expression/prefix.rs
@@ -30,8 +30,8 @@ impl Prefix {
         &self.right
     }
 
-    pub fn right_mut(&mut self) -> &mut Box<Expression> {
-        &mut self.right
+    pub fn update_expression(&mut self, expression: Expression) {
+        self.right = Box::new(expression);
     }
 }
 
diff --git a/src/ast/statement/expression.rs b/src/ast/statement/expression.rs
index 6fc3984..44e5360 100644
--- a/src/ast/statement/expression.rs
+++ b/src/ast/statement/expression.rs
@@ -31,8 +31,8 @@ impl ExpressionStatement {
         &self.expression
     }
 
-    pub fn expression_mut(&mut self) -> &mut Expression {
-        &mut self.expression
+    pub fn update_expression(&mut self, expression: Expression) {
+        self.expression = expression;
     }
 }
 
diff --git a/src/ast/statement/let_statement.rs b/src/ast/statement/let_statement.rs
index 3e81b9c..6f77749 100644
--- a/src/ast/statement/let_statement.rs
+++ b/src/ast/statement/let_statement.rs
@@ -34,16 +34,16 @@ impl LetStatement {
         &self.value
     }
 
-    pub fn value_mut(&mut self) -> &mut Expression {
-        &mut self.value
+    pub fn update_expression(&mut self, value: Expression) {
+        self.value = Box::new(value);
     }
 
     pub fn name(&self) -> &Identifier {
         &self.name
     }
 
-    pub fn name_mut(&mut self) -> &mut Identifier {
-        &mut self.name
+    pub fn update_identifier(&mut self, name: Identifier) {
+        self.name = name;
     }
 }
 
diff --git a/src/ast/statement/return_statement.rs b/src/ast/statement/return_statement.rs
index 8431446..34ebfe8 100644
--- a/src/ast/statement/return_statement.rs
+++ b/src/ast/statement/return_statement.rs
@@ -29,8 +29,8 @@ impl ReturnStatement {
         &self.return_value
     }
 
-    pub fn return_value_mut(&mut self) -> &mut Box<Expression> {
-        &mut self.return_value
+    pub fn update_expression(&mut self, expression: Expression) {
+        self.return_value = Box::new(expression);
     }
 
     pub fn return_value_into(self) -> Expression {
diff --git a/src/parser/mod.rs b/src/parser/mod.rs
index 966ce2f..ff48569 100644
--- a/src/parser/mod.rs
+++ b/src/parser/mod.rs
@@ -171,10 +171,10 @@ impl<'a> Parser<'a> {
             }
             .into());
         }
-        *stmt.name_mut() = Identifier::new(
+        stmt.update_identifier(Identifier::new(
             self.current_token.clone(),
             self.current_token.literal().into(),
-        );
+        ));
         tracing::trace!("stmt = {stmt}");
         if self.expect_peek(TokenType::ASSIGN).is_err() {
             return Err(Error::CannotFindTokenType {
@@ -183,7 +183,7 @@ impl<'a> Parser<'a> {
             .into());
         }
         self.next_token()?;
-        *stmt.value_mut() = self.parse_expression(LOWEST)?;
+        stmt.update_expression(self.parse_expression(LOWEST)?);
         while !self.cur_token_is(TokenType::SEMICOLON) {
             self.next_token()?;
         }
@@ -198,7 +198,7 @@ impl<'a> Parser<'a> {
         let mut stmt = ReturnStatement::new(self.current_token.clone());
         self.next_token()?;
         // add equal expression
-        *stmt.return_value_mut() = self.parse_expression(LOWEST)?.into();
+        stmt.update_expression(self.parse_expression(LOWEST)?.into());
         while !self.cur_token_is(TokenType::SEMICOLON) {
             self.next_token()?;
         }
@@ -213,7 +213,7 @@ impl<'a> Parser<'a> {
         tracing::trace!("current_token = {:?}", self.current_token);
         let mut stmt = ExpressionStatement::new(self.current_token.clone());
         tracing::trace!("before ExpressionStatement = {stmt}");
-        *stmt.expression_mut() = self.parse_expression(LOWEST)?;
+        stmt.update_expression(self.parse_expression(LOWEST)?);
         if self.peek_token_is(TokenType::SEMICOLON) {
             self.next_token()?;
         }
@@ -314,7 +314,7 @@ impl<'a> Parser<'a> {
         let mut literal = IntegerLiteral::new(self.current_token.clone());
         let value = self.current_token.literal().parse::<isize>()?;
 
-        *literal.value_mut() = value;
+        literal.update_value(value);
         Ok(literal.into())
     }
 
@@ -326,7 +326,7 @@ impl<'a> Parser<'a> {
             self.current_token.literal().into(),
         );
         self.next_token()?;
-        *expression.right_mut() = Box::new(self.parse_expression(PREFIX)?);
+        expression.update_expression(self.parse_expression(PREFIX)?);
         Ok(expression.into())
     }
 
@@ -345,7 +345,7 @@ impl<'a> Parser<'a> {
 
         self.next_token()?;
 
-        *expression.right_mut() = Box::new(self.parse_expression(precedence)?);
+        expression.update_expression(self.parse_expression(precedence)?);
 
         tracing::trace!("after InfixExpression = {expression}");
 
@@ -383,7 +383,7 @@ impl<'a> Parser<'a> {
 
         self.next_token()?;
 
-        *expression.condition_mut() = Box::new(self.parse_expression(LOWEST)?);
+        expression.update_expression(self.parse_expression(LOWEST)?);
 
         if self.expect_peek(TokenType::RPAREN).is_err() {
             return Err(Error::CannotFindTokenType {