@@ -247,10 +247,12 @@ fn intersect(
     vec1: &[(Expr, Expr)],
     vec2: &[(Expr, Expr)],
 ) {
-    for x1 in vec1.iter() {
-        for x2 in vec2.iter() {
-            if x1.0 == x2.0 && x1.1 == x2.1 || x1.1 == x2.0 && x1.0 == x2.1 {
-                accum.push((x1.0.clone(), x1.1.clone()));
+    if !(vec1.is_empty() || vec2.is_empty()) {
+        for x1 in vec1.iter() {
+            for x2 in vec2.iter() {
+                if x1.0 == x2.0 && x1.1 == x2.1 || x1.1 == x2.0 && x1.0 == x2.1 {
+                    accum.push((x1.0.clone(), x1.1.clone()));
+                }
             }
         }
     }
Original file line number	Diff line number	Diff line change
`@@ -247,10 +247,12 @@ fn intersect(`
`247`	`247`	`vec1: &[(Expr, Expr)],`
`248`	`248`	`vec2: &[(Expr, Expr)],`
`249`	`249`	`) {`
`250`		`- for x1 in vec1.iter() {`
`251`		`- for x2 in vec2.iter() {`
`252`		`- if x1.0 == x2.0 && x1.1 == x2.1 \|\| x1.1 == x2.0 && x1.0 == x2.1 {`
`253`		`- accum.push((x1.0.clone(), x1.1.clone()));`
	`250`	`+ if !(vec1.is_empty() \|\| vec2.is_empty()) {`
	`251`	`+ for x1 in vec1.iter() {`
	`252`	`+ for x2 in vec2.iter() {`
	`253`	`+ if x1.0 == x2.0 && x1.1 == x2.1 \|\| x1.1 == x2.0 && x1.0 == x2.1 {`
	`254`	`+ accum.push((x1.0.clone(), x1.1.clone()));`
	`255`	`+ }`
`254`	`256`	`}`
`255`	`257`	`}`
`256`	`258`	`}`