@@ -252,16 +252,16 @@ impl ListMatcherBuilder {
         self.submatchers.last_mut().unwrap().new_or_condition(arg)
     }
 
-    pub fn check_new_and_condition(&mut self) -> Result<(), Box<dyn Error>> {
+    pub fn check_new_and_condition(&mut self, arg: &str) -> Result<(), Box<dyn Error>> {
         {
             let child_or_matcher = &self.submatchers.last().unwrap();
             let grandchild_and_matcher = &child_or_matcher.submatchers.last().unwrap();
 
             if grandchild_and_matcher.submatchers.is_empty() {
-                return Err(From::from(
-                    "invalid expression; you have used a binary operator '-a' \
-                     with nothing before it.",
-                ));
+                return Err(From::from(format!(
+                    "invalid expression; you have used a binary operator \
+                     '{arg}' with nothing before it."
+                )));
             }
         }
         Ok(())
Original file line number	Diff line number	Diff line change
`@@ -252,16 +252,16 @@ impl ListMatcherBuilder {`
`252`	`252`	`self.submatchers.last_mut().unwrap().new_or_condition(arg)`
`253`	`253`	`}`
`254`	`254`
`255`		`- pub fn check_new_and_condition(&mut self) -> Result<(), Box<dyn Error>> {`
	`255`	`+ pub fn check_new_and_condition(&mut self, arg: &str) -> Result<(), Box<dyn Error>> {`
`256`	`256`	`{`
`257`	`257`	`let child_or_matcher = &self.submatchers.last().unwrap();`
`258`	`258`	`let grandchild_and_matcher = &child_or_matcher.submatchers.last().unwrap();`
`259`	`259`
`260`	`260`	`if grandchild_and_matcher.submatchers.is_empty() {`
`261`		`- return Err(From::from(`
`262`		`- "invalid expression; you have used a binary operator '-a' \`
`263`		`- with nothing before it.",`
`264`		`- ));`
	`261`	`+ return Err(From::from(format!(`
	`262`	`+ "invalid expression; you have used a binary operator \`
	`263`	`+ '{arg}' with nothing before it."`
	`264`	`+ )));`
`265`	`265`	`}`
`266`	`266`	`}`
`267`	`267`	`Ok(())`