Add tests and comments

compiler/noirc_errors/src/position.rs

@@ -94,6 +94,9 @@ impl Span {
         self.start() <= other.start() && self.end() >= other.end()
     }
 
+    /// Returns `true` if any point of `self` intersects a point of `other`.
+    /// If either span is empty, the point where the span is empty is considered
+    /// to be part of the span (so, for example, `1..1` intersects `1..3`).
     pub fn intersects(&self, other: &Span) -> bool {
         self.end() >= other.start() && self.start() <= other.end()
     }
@@ -140,3 +143,37 @@ impl Location {
         self.file == other.file && self.span.contains(&other.span)
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use crate::Span;
+
+    #[test]
+    fn test_intersects() {
+        assert!(Span::from(5..10).intersects(&Span::from(5..10)));
+
+        assert!(Span::from(5..10).intersects(&Span::from(5..5)));
+        assert!(Span::from(5..5).intersects(&Span::from(5..10)));
+
+        assert!(Span::from(10..10).intersects(&Span::from(5..10)));
+        assert!(Span::from(5..10).intersects(&Span::from(10..10)));
+
+        assert!(Span::from(5..10).intersects(&Span::from(6..9)));
+        assert!(Span::from(6..9).intersects(&Span::from(5..10)));
+
+        assert!(Span::from(5..10).intersects(&Span::from(4..11)));
+        assert!(Span::from(4..11).intersects(&Span::from(5..10)));
+
+        assert!(Span::from(5..10).intersects(&Span::from(4..6)));
+        assert!(Span::from(4..6).intersects(&Span::from(5..10)));
+
+        assert!(Span::from(5..10).intersects(&Span::from(9..11)));
+        assert!(Span::from(9..11).intersects(&Span::from(5..10)));
+
+        assert!(!Span::from(5..10).intersects(&Span::from(3..4)));
+        assert!(!Span::from(3..4).intersects(&Span::from(5..10)));
+
+        assert!(!Span::from(5..10).intersects(&Span::from(11..12)));
+        assert!(!Span::from(11..12).intersects(&Span::from(5..10)));
+    }
+}