Allow nested macro invocations

Closes #15

maud/src/lib.rs

@@ -79,16 +79,6 @@ pub mod rt {
         Markup { callback: f }
     }
 
-    /// rustc is a butt and doesn't let us quote macro invocations
-    /// directly. So we factor the `write!` call into a separate
-    /// function and use that instead.
-    ///
-    /// See <https://github.com/rust-lang/rust/issues/16617>
-    #[inline]
-    pub fn write_fmt<T: fmt::Display>(w: &mut fmt::Write, value: &T) -> fmt::Result {
-        write!(w, "{}", *value)
-    }
-
     pub struct Escaper<'a, 'b: 'a> {
         pub inner: &'a mut (fmt::Write + 'b),
     }

maud_macros/src/render.rs

@@ -59,6 +59,7 @@ impl<'cx> Renderer<'cx> {
         let Renderer { cx, w, stmts, .. } = { self.flush(); self };
         quote_expr!(cx,
             ::maud::rt::make_markup(|$w: &mut ::std::fmt::Write| -> Result<(), ::std::fmt::Error> {
+                use ::std::fmt::Write;
                 $stmts
                 Ok(())
             }))
@@ -96,12 +97,13 @@ impl<'cx> Renderer<'cx> {
         let w = self.w;
         let expr = match escape {
             Escape::PassThru =>
-                quote_expr!(self.cx, ::maud::rt::write_fmt($w, &$expr)),
+                quote_expr!(self.cx, write!($w, "{}", $expr)),
             Escape::Escape =>
                 quote_expr!(self.cx,
-                    ::maud::rt::write_fmt(
-                        &mut ::maud::rt::Escaper { inner: $w },
-                        &$expr)),
+                    write!(
+                        ::maud::rt::Escaper { inner: $w },
+                        "{}",
+                        $expr)),
         };
         let stmt = self.cx.stmt_expr(self.cx.expr_try(expr.span, expr));
         self.push(stmt);

maud_macros/tests/tests.rs

@@ -165,16 +165,12 @@ mod splices {
         assert_eq!(s, "Name: Pinkie Pie. Rating: 1");
     }
 
-    // FIXME: See <https://github.com/rust-lang/rust/issues/16617>
-    // for why this is commented out
-    /*
     #[test]
     fn nested_macro_invocation() {
         let best_pony = "Pinkie Pie";
         let s = html! { $(format!("{}", best_pony)) }.to_string();
         assert_eq!(s, "Pinkie Pie");
     }
-    */
 }
 
 #[test]