fix(errors): unexpected char errors were pointing one char too far

src/tokens.rs

@@ -216,11 +216,12 @@ impl Tokenizer {
                 } else if c.is_whitespace() {
                     self.advance();
                 } else {
-                    self.advance();
-                    return Err(ScanError {
+                    let result = Err(ScanError {
                         location: self.current_location(1),
                         kind: ScanErrorKind::UnexpectedChar(c),
                     });
+                    self.advance();
+                    return result;
                 }
             } else {
                 return Ok(None);