return new struct DynRender from new(); add an example which uses it

markup/examples/dynamic.rs

@@ -0,0 +1,34 @@
+markup::define! {
+    Tabs<'a>(tabs: &'a [Tab<'a>]) {
+       @for tab in tabs.iter() {
+            @tab
+       }
+    }
+
+    Tab<'a>(
+        title: &'a str,
+        body: markup::DynRender<'a>,
+    ) {
+        h1 { @title }
+        div { @body }
+    }
+}
+
+fn main() {
+    let tabs = [
+        Tab {
+            title: "Home",
+            body: markup::new! {
+                p { "This is the home page." }
+            },
+        },
+        Tab {
+            title: "About",
+            body: markup::new! {
+                p { "This is the about page." }
+            },
+        },
+    ];
+
+    println!("{}", Tabs { tabs: &tabs })
+}

markup/src/lib.rs

@@ -191,31 +191,25 @@ tuple_impl! { A B C D E F G H }
 tuple_impl! { A B C D E F G H I }
 tuple_impl! { A B C D E F G H I J }
 
-struct Template<F> {
-    f: F,
+pub struct DynRender<'a> {
+    f: Box<dyn Fn(&mut dyn std::fmt::Write) -> std::fmt::Result + 'a>,
 }
 
-pub fn new<'a, F>(f: F) -> impl Render + std::fmt::Display + 'a
+pub fn new<'a, F>(f: F) -> DynRender<'a>
 where
     F: Fn(&mut dyn std::fmt::Write) -> std::fmt::Result + 'a,
 {
-    Template { f }
+    DynRender { f: Box::new(f) }
 }
 
-impl<F> Render for Template<F>
-where
-    F: Fn(&mut dyn std::fmt::Write) -> std::fmt::Result,
-{
+impl<'a> Render for DynRender<'a> {
     #[inline]
     fn render(&self, writer: &mut impl std::fmt::Write) -> std::fmt::Result {
         (self.f)(writer)
     }
 }
 
-impl<F> std::fmt::Display for Template<F>
-where
-    F: Fn(&mut dyn std::fmt::Write) -> std::fmt::Result,
-{
+impl<'a> std::fmt::Display for DynRender<'a> {
     #[inline]
     fn fmt(&self, fmt: &mut std::fmt::Formatter) -> std::fmt::Result {
         Render::render(self, fmt)