Don't go out of bounds when slicing

src/lib.rs

@@ -498,7 +498,7 @@ impl Url {
     /// as is typically the case of `data:` and `mailto:` URLs.
     #[inline]
     pub fn cannot_be_a_base(&self) -> bool {
-        self.byte_at(self.path_start) != b'/'
+        !self.slice(self.path_start..).starts_with('/')
     }
 
     /// Return the username for this URL (typically the empty string)

src/slicing.rs

@@ -26,14 +26,14 @@ impl Index<RangeFrom<Position>> for Url {
 impl Index<RangeTo<Position>> for Url {
     type Output = str;
     fn index(&self, range: RangeTo<Position>) -> &str {
-        &self.serialization[..self.index(range.end)]
+        &self.serialization[..self.clamp(self.index(range.end))]
     }
 }
 
 impl Index<Range<Position>> for Url {
     type Output = str;
     fn index(&self, range: Range<Position>) -> &str {
-        &self.serialization[self.index(range.start)..self.index(range.end)]
+        &self.serialization[self.index(range.start)..self.clamp(self.index(range.end))]
     }
 }
 
@@ -98,6 +98,19 @@ pub enum Position {
 }
 
 impl Url {
+    #[inline]
+    fn clamp(&self, index: usize) -> usize {
+        if index >= self.serialization.len() {
+            if self.serialization.len() == 0 {
+                0
+            } else {
+                self.serialization.len() - 1
+            }
+        } else {
+            index
+        }
+    }
+
     #[inline]
     fn index(&self, position: Position) -> usize {
         match position {