Cleanup fold code and split logic to fold single elements

crates/ra_syntax/src/ast/generated.rs

@@ -2193,3 +2193,21 @@ impl<'a> WhileExpr<'a> {
     }
 }
 
+// Whitespace
+#[derive(Debug, Clone, Copy)]
+pub struct Whitespace<'a> {
+    syntax: SyntaxNodeRef<'a>,
+}
+
+impl<'a> AstNode<'a> for Whitespace<'a> {
+    fn cast(syntax: SyntaxNodeRef<'a>) -> Option<Self> {
+        match syntax.kind() {
+            WHITESPACE => Some(Whitespace { syntax }),
+            _ => None,
+        }
+    }
+    fn syntax(self) -> SyntaxNodeRef<'a> { self.syntax }
+}
+
+impl<'a> Whitespace<'a> {}
+

crates/ra_syntax/src/ast/mod.rs

@@ -100,8 +100,8 @@ impl<'a> Lifetime<'a> {
 }
 
 impl<'a> Comment<'a> {
-    pub fn text(&self) -> SmolStr {
-        self.syntax().leaf_text().unwrap().clone()
+    pub fn text(&self) -> &SmolStr {
+        self.syntax().leaf_text().unwrap()
     }
 
     pub fn flavor(&self) -> CommentFlavor {
@@ -120,6 +120,14 @@ impl<'a> Comment<'a> {
     pub fn prefix(&self) -> &'static str {
         self.flavor().prefix()
     }
+
+    pub fn count_newlines_lazy(&self) -> impl Iterator<Item = &()> {
+        self.text().chars().filter(|&c| c == '\n').map(|_| &())
+    }
+
+    pub fn has_newlines(&self) -> bool {
+        self.count_newlines_lazy().count() > 0
+    }
 }
 
 #[derive(Debug)]
@@ -142,6 +150,20 @@ impl CommentFlavor {
     }
 }
 
+impl<'a> Whitespace<'a> {
+    pub fn text(&self) -> &SmolStr {
+        &self.syntax().leaf_text().unwrap()
+    }
+
+    pub fn count_newlines_lazy(&self) -> impl Iterator<Item = &()> {
+        self.text().chars().filter(|&c| c == '\n').map(|_| &())
+    }
+
+    pub fn has_newlines(&self) -> bool {
+        self.count_newlines_lazy().count() > 0
+    }
+}
+
 impl<'a> Name<'a> {
     pub fn text(&self) -> SmolStr {
         let ident = self.syntax().first_child()