Simplify parsing by expecting the tokens stream will never be exhausted.

src/optimize.rs

@@ -178,7 +178,7 @@ fn optimize_stmt<'a>(stmt: Stmt, state: &mut State<'a>, preserve_result: bool) -
                 Box::new(optimize_expr(expr, state)),
                 Box::new(optimize_stmt(*if_block, state, true)),
                 match optimize_stmt(*else_block, state, true) {
-                    stmt if matches!(stmt, Stmt::Noop(_)) => None, // Noop -> no else block
+                    Stmt::Noop(_) => None, // Noop -> no else block
                     stmt => Some(Box::new(stmt)),
                 },
             ),

src/parser.rs

@@ -508,7 +508,8 @@ impl Expr {
 
 /// Consume a particular token, checking that it is the expected one.
 fn eat_token(input: &mut Peekable<TokenIterator>, token: Token) -> Position {
-    if let Some((t, pos)) = input.next() {
+    let (t, pos) = input.next().unwrap();
+
     if t != token {
         panic!(
             "expecting {} (found {}) at {}",
@@ -518,9 +519,6 @@ fn eat_token(input: &mut Peekable<TokenIterator>, token: Token) -> Position {
         );
     }
     pos
-    } else {
-        panic!("expecting {} but already EOF", token.syntax());
-    }
 }
 
 /// Match a particular token, consuming it if matched.
@@ -1269,14 +1267,11 @@ fn parse_binary_op<'a>(
             return Ok(current_lhs);
         }
 
-        if let Some((op_token, pos)) = input.next() {
+        let (op_token, pos) = input.next().unwrap();
+
         let rhs = parse_unary(input, allow_stmt_expr)?;
 
-            let next_precedence = if let Some((next_op, _)) = input.peek() {
+        let next_precedence = input.peek().unwrap().0.precedence();
-                next_op.precedence()
-            } else {
-                0
-            };
 
         // Bind to right if the next operator has higher precedence
         // If same precedence, then check if the operator binds right
@@ -1292,17 +1287,11 @@ fn parse_binary_op<'a>(
         current_lhs = match op_token {
             Token::Plus => Expr::FunctionCall("+".into(), vec![current_lhs, rhs], None, pos),
             Token::Minus => Expr::FunctionCall("-".into(), vec![current_lhs, rhs], None, pos),
-                Token::Multiply => {
+            Token::Multiply => Expr::FunctionCall("*".into(), vec![current_lhs, rhs], None, pos),
-                    Expr::FunctionCall("*".into(), vec![current_lhs, rhs], None, pos)
-                }
             Token::Divide => Expr::FunctionCall("/".into(), vec![current_lhs, rhs], None, pos),
 
-                Token::LeftShift => {
+            Token::LeftShift => Expr::FunctionCall("<<".into(), vec![current_lhs, rhs], None, pos),
-                    Expr::FunctionCall("<<".into(), vec![current_lhs, rhs], None, pos)
+            Token::RightShift => Expr::FunctionCall(">>".into(), vec![current_lhs, rhs], None, pos),
-                }
-                Token::RightShift => {
-                    Expr::FunctionCall(">>".into(), vec![current_lhs, rhs], None, pos)
-                }
             Token::Modulo => Expr::FunctionCall("%".into(), vec![current_lhs, rhs], None, pos),
             Token::PowerOf => Expr::FunctionCall("~".into(), vec![current_lhs, rhs], None, pos),
 
@@ -1328,9 +1317,7 @@ fn parse_binary_op<'a>(
 
             Token::Or => Expr::Or(Box::new(current_lhs), Box::new(rhs), pos),
             Token::And => Expr::And(Box::new(current_lhs), Box::new(rhs), pos),
-                Token::Ampersand => {
+            Token::Ampersand => Expr::FunctionCall("&".into(), vec![current_lhs, rhs], None, pos),
-                    Expr::FunctionCall("&".into(), vec![current_lhs, rhs], None, pos)
-                }
             Token::Pipe => Expr::FunctionCall("|".into(), vec![current_lhs, rhs], None, pos),
             Token::XOr => Expr::FunctionCall("^".into(), vec![current_lhs, rhs], None, pos),
 
@@ -1366,7 +1353,6 @@ fn parse_binary_op<'a>(
             token => return Err(PERR::UnknownOperator(token.syntax().into()).into_err(pos)),
         };
     }
-    }
 }
 
 /// Parse an expression.
@@ -1439,7 +1425,7 @@ fn parse_if<'a>(
 
     // if guard { if_body } else ...
     let else_body = if match_token(input, Token::Else).unwrap_or(false) {
-        Some(Box::new(if matches!(input.peek(), Some((Token::If, _))) {
+        Some(Box::new(if let (Token::If, _) = input.peek().unwrap() {
             // if guard { if_body } else if ...
             parse_if(input, breakable, allow_stmt_expr)?
         } else {
@@ -1676,9 +1662,9 @@ fn parse_stmt<'a>(
         Token::Return | Token::Throw => {
             let pos = *pos;
 
-            let return_type = match input.next() {
+            let return_type = match input.next().unwrap() {
-                Some((Token::Return, _)) => ReturnType::Return,
+                (Token::Return, _) => ReturnType::Return,
-                Some((Token::Throw, _)) => ReturnType::Exception,
+                (Token::Throw, _) => ReturnType::Exception,
                 _ => panic!("token should be return or throw"),
             };
 
@@ -1819,7 +1805,7 @@ fn parse_global_level<'a>(
         // Collect all the function definitions
         #[cfg(not(feature = "no_function"))]
         {
-            if matches!(input.peek().expect("should not be None"), (Token::Fn, _)) {
+            if let (Token::Fn, _) = input.peek().unwrap() {
                 let f = parse_fn(input, true)?;
                 functions.insert(calc_fn_def(&f.name, f.params.len()), f);
                 continue;

src/token.rs

@@ -991,6 +991,8 @@ impl<'a> TokenIterator<'a> {
                 }
                 ('~', _) => return Some((Token::PowerOf, pos)),
 
+                ('\0', _) => panic!("should not be EOF"),
+
                 (ch, _) if ch.is_whitespace() => (),
                 (ch, _) => return Some((Token::LexError(Box::new(LERR::UnexpectedChar(ch))), pos)),
             }