more idiomatic syntax

src/evaluator.rs

@@ -93,7 +93,7 @@ fn evaluate_node(ast_node: &AstNode) -> Result<Number, String> {
   let children = &ast_node.children;
   match token {
     Token::Number(number) => {
-      Ok(Number::new(number.clone(), Unit::NoUnit))
+      Ok(Number::new(*number, Unit::NoUnit))
     },
     Token::Constant(constant) => {
       match constant {
@@ -192,7 +192,7 @@ fn evaluate_node(ast_node: &AstNode) -> Result<Number, String> {
     Token::Unit(unit) => {
       let child_node = children.get(0).ok_or("Unit has no child[0]")?;
       let child_answer = evaluate_node(child_node)?;
-      Ok(Number::new(child_answer.value, unit.clone()))
+      Ok(Number::new(child_answer.value, *unit))
     },
     Token::Negative => {
       let child_node = children.get(0).ok_or("Negative has no child[0]")?;

src/lexer.rs

@@ -642,7 +642,7 @@ pub fn lex(input: &str, remove_trailing_operator: bool, default_degree: Unit) ->
   }
 
   if tokens.is_empty() {
-    Err("Input was empty".to_string())
+    return Err("Input was empty".to_string());
   }
 
   let mut token_index = 0;

src/parser.rs

@@ -17,7 +17,7 @@ impl AstNode {
   pub fn new(token: Token) -> AstNode {
     AstNode {
       children: Vec::new(),
-      token: token,
+      token,
     }
   }
 }

src/units.rs

@@ -494,7 +494,7 @@ pub fn to_ideal_joule_unit(number: Number) -> Number {
 /// - If you multiply [`ElectricCurrent`] with [`Resistance`], the result has a unit of [`Voltage`]
 /// - If you multiply [`Power`] with [`Time`], the result has a unit of [`Energy`]
 pub fn multiply(left: Number, right: Number) -> Result<Number, String> {
-  Ok(actual_multiply(left, right, false)?)
+  actual_multiply(left, right, false)
 }
 
 fn actual_multiply(left: Number, right: Number, swapped: bool) -> Result<Number, String> {