better function calls + cleanup

src/lexer.rs

@@ -63,7 +63,7 @@ pub enum Token {
 
     Literal(Literal),
 }
-#[derive(PartialEq, Eq, PartialOrd, Ord)]
+#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Copy)]
 pub enum Precedence {
     Min,
     Return,
@@ -112,12 +112,13 @@ pub enum LexError {
     UnexpectedCharacter(char),
     UnexpectedEnd,
 }
-trait Check {
+impl fmt::Display for LexError {
-    fn check(self) -> Result<char>;
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::UnexpectedEnd => write!(f, "unexpected end of source"),
+            Self::UnexpectedCharacter(c) => write!(f, "unexpected char '{c}'"),
+            Self::InvalidEscape(c) => write!(f, "\"\\{c}\" is not a valid string escape"),
         }
-impl Check for Option<char> {
-    fn check(self) -> Result<char> {
-        self.ok_or(LexError::UnexpectedEnd)
     }
 }
 
@@ -146,7 +147,6 @@ where
     fn next(&mut self) -> Option<char> {
         self.chars.next()
     }
-
     fn next_unwrap(&mut self) -> char {
         match self.next() {
             Some(c) => c,
@@ -154,15 +154,20 @@ where
         }
     }
 
+    fn try_peek(&mut self) -> Result<char> {
+        self.peek().ok_or(LexError::UnexpectedEnd)
+    }
+    fn try_eat_peek(&mut self) -> Result<char> {
+        self.eat_peek().ok_or(LexError::UnexpectedEnd)
+    }
+
     fn eat(&mut self) {
         self.next();
     }
-
     fn eat_to(&mut self, tk: Token) -> Option<Result<Token>> {
         self.eat();
         Some(Ok(tk))
     }
-
     fn eat_peek(&mut self) -> Option<char> {
         self.eat();
         self.peek()
@@ -216,11 +221,11 @@ where
         let mut str = String::new();
 
         loop {
-            match self.peek().check()? {
+            match self.try_peek()? {
-                '\\' => match self.eat_peek().check()? {
+                '\\' => match self.try_eat_peek()? {
                     'n' => {
                         self.eat();
-                        str.push('\n')
+                        str.push('\n');
                     }
                     c => {
                         break Err(LexError::InvalidEscape(c));

src/parser.rs

@@ -1,4 +1,4 @@
-use std::iter::Peekable;
+use std::{fmt, iter::Peekable};
 
 use crate::lexer::{Associativity, LexError, Literal, Precedence, Token};
 
@@ -51,6 +51,15 @@ impl From<LexError> for ParseError {
         Self::LexError(err)
     }
 }
+impl fmt::Display for ParseError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::UnexpectedEnd => write!(f, "unexpected end of token stream"),
+            Self::UnexpectedToken(t) => write!(f, "unexpected token: {t:?}"),
+            Self::LexError(err) => write!(f, "error while lexing: {err}"),
+        }
+    }
+}
 
 pub type Result<T> = std::result::Result<T, ParseError>;
 
@@ -109,10 +118,6 @@ where
                     _ => unreachable!(),
                 })
             }
-            // return
-            Token::Return => Box::new(Expr::Return(self.parse_expr(Precedence::Min, false)?)),
-            // not
-            Token::Not => Box::new(Expr::Not(self.parse_expr(Precedence::Min, false)?)),
             // unexpected token
             t => return Err(ParseError::UnexpectedToken(t)),
         };
@@ -127,12 +132,22 @@ where
                 Ok(Token::ParenOpen) => {
                     // eat opening paren
                     self.eat();
+
                     let mut exprs = Vec::new();
                     while !matches!(self.try_peek()?, Token::ParenClose) {
                         exprs.push(*self.parse_expr(Precedence::Min, false)?);
+
+                        // Continue if there is a comma,
+                        // ignore closing parens
+                        match self.try_peek()? {
+                            Token::Comma => self.eat(),
+                            Token::ParenClose => {}
+                            _ => return Err(ParseError::UnexpectedToken(self.next_unwrap())),
+                        }
                     }
                     // eat closing paren
                     self.eat();
+
                     lhs = Box::new(Expr::Call(lhs, exprs));
                     continue;
                 }