Janitor: Fix clippy::len_without_is_empty

sixtyfps_runtime/corelib/model.rs

@@ -687,6 +687,11 @@ impl<C: RepeatedComponent> Repeater<C> {
         self.inner.borrow().borrow().components.len()
     }
 
+    /// Return true if the Repeater is empty
+    pub fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
+
     /// Returns a vector containing all components
     pub fn components_vec(&self) -> Vec<ComponentRc<C>> {
         self.inner.borrow().borrow().components.iter().flat_map(|x| x.1.clone()).collect()

sixtyfps_runtime/corelib/sharedvector.rs

@@ -138,6 +138,11 @@ impl<T> SharedVector<T> {
         unsafe { self.inner.cast::<SharedVectorHeader>().as_ref().size }
     }
 
+    /// Return true if the SharedVector is empty
+    pub fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
+
     /// Return a slice to the array
     pub fn as_slice(&self) -> &[T] {
         if self.len() == 0 {

sixtyfps_runtime/corelib/string.rs

@@ -41,6 +41,11 @@ impl SharedString {
         self.inner.header.header
     }
 
+    /// Return true if the String is empty
+    pub fn is_empty(&self) -> bool {
+        self.len() == 0
+    }
+
     /// Return a slice to the string
     pub fn as_str(&self) -> &str {
         unsafe {