Use doc(hidden) instead of allow(missing_docs) in the test harness

So that it doesn't fail with `forbid(missing_docs)`

Fixes #130218

compiler/rustc_builtin_macros/src/test_harness.rs

@@ -326,8 +326,8 @@ fn mk_main(cx: &mut TestCtxt<'_>) -> P<ast::Item> {
     let main_attr = ecx.attr_word(sym::rustc_main, sp);
     // #[coverage(off)]
     let coverage_attr = ecx.attr_nested_word(sym::coverage, sym::off, sp);
-    // #[allow(missing_docs)]
-    let missing_docs_attr = ecx.attr_nested_word(sym::allow, sym::missing_docs, sp);
+    // #[doc(hidden)]
+    let doc_hidden_attr = ecx.attr_nested_word(sym::doc, sym::hidden, sp);
 
     // pub fn main() { ... }
     let main_ret_ty = ecx.ty(sp, ast::TyKind::Tup(ThinVec::new()));
@@ -357,7 +357,7 @@ fn mk_main(cx: &mut TestCtxt<'_>) -> P<ast::Item> {
 
     let main = P(ast::Item {
         ident: main_id,
-        attrs: thin_vec![main_attr, coverage_attr, missing_docs_attr],
+        attrs: thin_vec![main_attr, coverage_attr, doc_hidden_attr],
         id: ast::DUMMY_NODE_ID,
         kind: main,
         vis: ast::Visibility { span: sp, kind: ast::VisibilityKind::Public, tokens: None },

compiler/rustc_span/src/symbol.rs

@@ -1236,7 +1236,6 @@ symbols! {
         mir_unwind_unreachable,
         mir_variant,
         miri,
-        missing_docs,
         mmx_reg,
         modifiers,
         module,

tests/pretty/tests-are-sorted.pp

@@ -86,7 +86,7 @@
 fn a_test() {}
 #[rustc_main]
 #[coverage(off)]
-#[allow(missing_docs)]
+#[doc(hidden)]
 pub fn main() -> () {
     extern crate test;
     test::test_main_static(&[&a_test, &m_test, &z_test])

tests/ui/lint/lint-missing-doc-test.rs

@@ -2,7 +2,9 @@
 //! on the generated test harness.
 
 //@ check-pass
-//@ compile-flags: --test -Dmissing_docs
+//@ compile-flags: --test
+
+#![forbid(missing_docs)]
 
 #[test]
 fn test() {}