fixed it :)

src/parser.rs

@@ -61,11 +61,17 @@ where
     )
 }
 
-fn identifier(input: &str) -> IResult<&str, &str> {
+fn identifier(i: &str) -> IResult<&str, &str> {
+    println!("identifier: {}", i);
     recognize(pair(
         alt((alpha1, tag("_"))),
         many0(alt((alphanumeric1, tag("_")))),
-    ))(input)
+    ))(i)
+}
+
+fn variable(i: &str) -> IResult<&str, Expr> {
+    println!("variable: {}", i);
+    map(identifier, |a| Expr::Var(a.to_string()))(i)
 }
 
 fn parse_str<'a>(i: &'a str) -> IResult<&'a str, &'a str> {
@@ -73,6 +79,7 @@ fn parse_str<'a>(i: &'a str) -> IResult<&'a str, &'a str> {
 }
 
 fn string<'a>(i: &'a str) -> IResult<&'a str, Expr> {
+    println!("string: {}", i);
     map(
         preceded(char('\"'), cut(terminated(parse_str, char('\"')))),
         |s| Expr::LStr(String::from(s)),
@@ -87,18 +94,22 @@ fn boolean<'a>(i: &'a str) -> IResult<&'a str, Expr> {
     ))(i)
 }
 
-fn call<'a>(i: &'a str) -> IResult<&'a str, (Identifier, Vec<Expr>)> {
+fn call<'a>(i: &'a str) -> IResult<&'a str, Expr> {
     println!("call: {}", i);
     map(
         tuple((
             identifier,
-            delimited(
-                char('('),
-                separated_list0(tuple((sc, tag(","), sc)), expr),
-                char(')'),
-            ),
+            sc,
+            alt((
+                value(vec![], tuple((char('('), sc, char(')')))),
+                delimited(
+                    char('('),
+                    separated_list0(tuple((sc, tag(","), sc)), expr),
+                    char(')'),
+                ),
+            )),
         )),
-        |(i, v)| (i.to_string(), v),
+        |(i, _, v)| Expr::Call(i.to_string(), v),
     )(i)
 }
 
@@ -112,7 +123,7 @@ fn literal(i: &str) -> IResult<&str, Expr> {
 }
 
 fn factor_bin(i: &str) -> IResult<&str, Expr> {
-    alt((delimited(space0, literal, space0), expr))(i)
+    alt((delimited(space0, term, space0), expr))(i)
 }
 
 fn bin_less_greater(i: &str) -> IResult<&str, Expr> {
@@ -177,25 +188,19 @@ fn binary<'a>(i: &'a str) -> IResult<&'a str, Expr> {
     )(i)
 }
 fn receive<'a>(i: &'a str) -> IResult<&'a str, Expr> {
+    println!("receive: {}", i);
     map(pair(tag("<-"), expr), |(_, expr)| {
         Expr::Receive(Box::new(expr))
     })(i)
 }
 
 pub fn expr<'a>(i: &'a str) -> IResult<&'a str, Expr> {
+    alt((receive, binary))(i)
+}
+
+fn term<'a>(i: &'a str) -> IResult<&'a str, Expr> {
     println!("expr: {}", i);
-    delimited(
-        sc,
-        alt((
-            parens(expr),
-            map(call, |(i, v)| Expr::Call(i, v)),
-            receive,
-            binary,
-            literal,
-            map(identifier, |i| Expr::Var(i.to_string())),
-        )),
-        sc,
-    )(i)
+    delimited(sc, alt((literal, call, variable, parens(expr))), sc)(i)
 }
 
 #[cfg(test)]
@@ -214,7 +219,7 @@ mod tests {
     #[test]
     fn can_parse_binary_op() {
         let a = "3 +3 +  6";
-        let (_rest, res) = binary(a).unwrap();
+        let (_rest, res) = expr(a).unwrap();
 
         assert_eq!(
             res,
@@ -233,7 +238,7 @@ mod tests {
     #[test]
     fn can_parse_binary_op_with_str() {
         let a = r#"3 +3 +  6 + "hey""#;
-        let (_rest, res) = binary(a).unwrap();
+        let (_rest, res) = expr(a).unwrap();
 
         assert_eq!(
             res,
@@ -253,6 +258,15 @@ mod tests {
         );
     }
 
+    #[test]
+    fn can_parse_var() {
+        let a = "hello";
+        let (rest, res) = expr(a).unwrap();
+
+        assert_eq!(res, Expr::Var("hello".to_string()));
+        assert_eq!(rest, "");
+    }
+
     #[test]
     fn can_parse_empty_call() {
         let a = "hello()";
@@ -262,6 +276,18 @@ mod tests {
         assert_eq!(rest, "");
     }
 
+    #[test]
+    fn can_parse_call_with_var() {
+        let a = "hello(hey)";
+        let (rest, res) = expr(a).unwrap();
+
+        assert_eq!(
+            res,
+            Expr::Call("hello".to_string(), vec![Expr::Var("hey".to_string())])
+        );
+        assert_eq!(rest, "");
+    }
+
     #[test]
     fn can_parse_call() {
         let a = "hello(1.0, 45 , yeah)";