Add a test of rustdoc on macro-generated macro

Author: dtolnay

src/test/rustdoc/macro-generated-macro.rs

@@ -0,0 +1,14 @@
+macro_rules! outer {
+    ($($matcher:tt)*) => {
+        #[macro_export]
+        macro_rules! inner {
+            (<= $($matcher)* =>) => {};
+        }
+    }
+}
+
+// @has macro_generated_macro/macro.inner.html //pre 'macro_rules! inner {'
+// @has - //pre '(<= type $($i : ident) :: * + $e : expr =>) => { ... };'
+outer!(type $($i:ident)::* + $e:expr);
+
+inner!(<= type foo::bar + x.sort() =>);