auto merge of #5182 : zslayton/servo/master, r=jdm

Opening this PR to invite feedback. 

Of the many `match` statement candidates for conversion to `if let`, several included `if` guards. Since `if let` doesn't support this syntax, I used nested if statements. If this is undesirable, say the word and I can revert those cases to `match`.

1 files changed, 14 insertions, 23 deletions

diff --git a/components/script/dom/virtualmethods.rs b/components/script/dom/virtualmethods.rs
index 707298ebdc5..a3e53f42bd3 100644
--- a/components/script/dom/virtualmethods.rs
+++ b/components/script/dom/virtualmethods.rs
@@ -71,18 +71,16 @@ pub trait VirtualMethods {
     /// Called when changing or adding attributes, after the attribute's value
     /// has been updated.
     fn after_set_attr(&self, attr: JSRef<Attr>) {
-        match self.super_type() {
-            Some(ref s) => s.after_set_attr(attr),
-            _ => (),
+        if let Some(ref s) = self.super_type() {
+            s.after_set_attr(attr);
         }
     }
 
     /// Called when changing or removing attributes, before any modification
     /// has taken place.
     fn before_remove_attr(&self, attr: JSRef<Attr>) {
-        match self.super_type() {
-            Some(ref s) => s.before_remove_attr(attr),
-            _ => (),
+        if let Some(ref s) = self.super_type() {
+            s.before_remove_attr(attr);
         }
     }
 
@@ -98,45 +96,38 @@ pub trait VirtualMethods {
     /// Called when a Node is appended to a tree, where 'tree_in_doc' indicates
     /// whether the tree is part of a Document.
     fn bind_to_tree(&self, tree_in_doc: bool) {
-        match self.super_type() {
-            Some(ref s) => s.bind_to_tree(tree_in_doc),
-            _ => (),
+        if let Some(ref s) = self.super_type() {
+            s.bind_to_tree(tree_in_doc);
         }
     }
 
     /// Called when a Node is removed from a tree, where 'tree_in_doc'
     /// indicates whether the tree is part of a Document.
     fn unbind_from_tree(&self, tree_in_doc: bool) {
-        match self.super_type() {
-            Some(ref s) => s.unbind_from_tree(tree_in_doc),
-            _ => (),
+        if let Some(ref s) = self.super_type() {
+            s.unbind_from_tree(tree_in_doc);
         }
     }
 
     /// Called on the parent when a node is added to its child list.
     fn child_inserted(&self, child: JSRef<Node>) {
-        match self.super_type() {
-            Some(ref s) => s.child_inserted(child),
-            _ => (),
+        if let Some(ref s) = self.super_type() {
+            s.child_inserted(child);
         }
     }
 
     /// Called during event dispatch after the bubbling phase completes.
     fn handle_event(&self, event: JSRef<Event>) {
-        match self.super_type() {
-            Some(s) => {
-                s.handle_event(event);
-            }
-            _ => (),
+        if let Some(s) = self.super_type() {
+            s.handle_event(event);
         }
     }
 
     /// https://dom.spec.whatwg.org/#concept-node-clone (step 5)
     fn cloning_steps(&self, copy: JSRef<Node>, maybe_doc: Option<JSRef<Document>>,
                      clone_children: CloneChildrenFlag) {
-        match self.super_type() {
-            Some(ref s) => s.cloning_steps(copy, maybe_doc, clone_children),
-            _ => (),
+        if let Some(ref s) = self.super_type() {
+            s.cloning_steps(copy, maybe_doc, clone_children);
         }
     }
 }