rustdoc: Gate unstable doc(cfg()) predicates

Author: clubby789

src/librustdoc/clean/cfg.rs

@@ -8,7 +8,6 @@ use std::{mem, ops};
 
 use rustc_ast::{LitKind, MetaItem, MetaItemInner, MetaItemKind, MetaItemLit};
 use rustc_data_structures::fx::FxHashSet;
-use rustc_feature::Features;
 use rustc_session::parse::ParseSess;
 use rustc_span::Span;
 use rustc_span::symbol::{Symbol, sym};
@@ -132,18 +131,13 @@ impl Cfg {
     /// Checks whether the given configuration can be matched in the current session.
     ///
     /// Equivalent to `attr::cfg_matches`.
-    // FIXME: Actually make use of `features`.
-    pub(crate) fn matches(&self, psess: &ParseSess, features: Option<&Features>) -> bool {
+    pub(crate) fn matches(&self, psess: &ParseSess) -> bool {
         match *self {
             Cfg::False => false,
             Cfg::True => true,
-            Cfg::Not(ref child) => !child.matches(psess, features),
-            Cfg::All(ref sub_cfgs) => {
-                sub_cfgs.iter().all(|sub_cfg| sub_cfg.matches(psess, features))
-            }
-            Cfg::Any(ref sub_cfgs) => {
-                sub_cfgs.iter().any(|sub_cfg| sub_cfg.matches(psess, features))
-            }
+            Cfg::Not(ref child) => !child.matches(psess),
+            Cfg::All(ref sub_cfgs) => sub_cfgs.iter().all(|sub_cfg| sub_cfg.matches(psess)),
+            Cfg::Any(ref sub_cfgs) => sub_cfgs.iter().any(|sub_cfg| sub_cfg.matches(psess)),
             Cfg::Cfg(name, value) => psess.config.contains(&(name, value)),
         }
     }

src/librustdoc/clean/types.rs

@@ -1056,6 +1056,13 @@ pub(crate) fn extract_cfg_from_attrs<'a, I: Iterator<Item = &'a hir::Attribute>
                         .meta_item()
                         .and_then(|item| rustc_expand::config::parse_cfg(item, sess))
                     {
+                        // The result is unused here but we can gate unstable predicates
+                        rustc_attr_parsing::cfg_matches(
+                            cfg_mi,
+                            tcx.sess,
+                            rustc_ast::CRATE_NODE_ID,
+                            Some(tcx.features()),
+                        );
                         match Cfg::parse(cfg_mi) {
                             Ok(new_cfg) => cfg &= new_cfg,
                             Err(e) => {

src/librustdoc/doctest/rust.rs

@@ -98,7 +98,7 @@ impl HirCollector<'_> {
         let ast_attrs = self.tcx.hir().attrs(self.tcx.local_def_id_to_hir_id(def_id));
         if let Some(ref cfg) =
             extract_cfg_from_attrs(ast_attrs.iter(), self.tcx, &FxHashSet::default())
-            && !cfg.matches(&self.tcx.sess.psess, Some(self.tcx.features()))
+            && !cfg.matches(&self.tcx.sess.psess)
         {
             return;
         }

tests/rustdoc/doc-cfg-unstable.rs

@@ -0,0 +1,11 @@
+//@ should-fail
+
+// #138113: rustdoc didn't gate unstable predicates inside `doc(cfg(..))`
+
+#![feature(doc_cfg)]
+
+#[doc(cfg(false))]
+pub fn foo() {}
+
+#[doc(cfg(true))]
+pub fn bar() {}