Fix fast lane delimiter detection

src/fast_lane.rs

@@ -162,7 +162,7 @@ impl TryFrom<&Opt> for FastOpt {
     type Error = &'static str;
 
     fn try_from(value: &Opt) -> Result<Self, Self::Error> {
-        if !value.delimiter.as_bytes().len() == 1 {
+        if value.delimiter.as_bytes().len() != 1 {
             return Err("Delimiter must be 1 byte wide for FastOpt");
         }
 
@@ -307,6 +307,20 @@ mod tests {
         assert_eq!(output, b"foo\n".as_slice());
     }
 
+    #[test]
+    fn fail_to_convert_opt_with_long_delimiter_to_fastopt() {
+        let opt = Opt {
+            delimiter: "foo".to_owned(),
+            ..Default::default()
+        };
+
+        assert!(FastOpt::try_from(&opt).is_err());
+        assert_eq!(
+            FastOpt::try_from(&opt).unwrap_err(),
+            "Delimiter must be 1 byte wide for FastOpt"
+        );
+    }
+
     fn make_cut_str_buffers() -> (Vec<u8>, Vec<Range<usize>>) {
         let output = Vec::new();
         let fields = Vec::new();

tests/cli.rs

@@ -42,6 +42,18 @@ fn it_cut_consecutive_delimiters() {
     assert.success().stdout("foobar\n");
 }
 
+#[test]
+fn it_cut_using_multibyte_delimiters() {
+    let mut cmd = Command::cargo_bin(env!("CARGO_PKG_NAME")).unwrap();
+
+    let assert = cmd
+        .args(["-d", "...", "-f", "2"])
+        .write_stdin("foo...bar")
+        .assert();
+
+    assert.success().stdout("bar\n");
+}
+
 #[test]
 fn it_works_on_multiple_lines() {
     let mut cmd = Command::cargo_bin(env!("CARGO_PKG_NAME")).unwrap();