Auto merge of #138907 - GuillaumeGomez:rfc-3631, r=fmease,camelid,Manishearth,lolbinarycat

Implement RFC 3631: add rustdoc doc_cfg features

Implementation of rust-lang/rfcs#3631.

This implementation actually resulted in a lot of simplifications:
 * All `cfg` computation is now done in one place: `propagate_doc_cfg.rs`. Because (trait) `impl`s are not retrieved at the same time as the other items, we cannot perform this computation in the clean process, it needs to be after.
 * Because there is `cfg` inheritance, we can keep track of them in one place (in `propagate_doc_cfg.rs`), meaning we don't need to copy an item's attributes to its children anymore. Only exception: impl items. For them we clone only `cfg` attributes.
 * `propagate_doc_cfg.rs` is also now much simpler, much less need to keep track of parents, since everything we need is handled by the new `CfgInfo` type.
 * I also suspect that `Cfg::simplify_with` could either be removed or at least used directly into `propagate_doc_cfg.rs` when we compute `cfg`s. Considering how big the PR already is, I'll do it in a follow-up.

I didn't remove the `doc_cfg*` features in this PR because some dependencies used in `rustc` (like `stdarch`) are using it, so we need to have a nightly released with this PR before I can switch to the new feature.

r? ghost

Author: bors

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -183,7 +183,7 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
                 gate_doc!(
                     "experimental" {
                         cfg => doc_cfg
-                        cfg_hide => doc_cfg_hide
+                        auto_cfg => doc_cfg
                         masked => doc_masked
                         notable_trait => doc_notable_trait
                     }

compiler/rustc_feature/src/removed.rs

@@ -101,6 +101,10 @@ declare_features! (
      Some("never properly implemented; requires significant design work"), 127655),
     /// Allows deriving traits as per `SmartPointer` specification
     (removed, derive_smart_pointer, "1.84.0", Some(123430), Some("replaced by `CoercePointee`"), 131284),
+    /// Tells rustdoc to automatically generate `#[doc(cfg(...))]`.
+    (removed, doc_auto_cfg, "1.58.0", Some(43781), Some("merged into `doc_cfg`"), 138907),
+    /// Allows `#[doc(cfg_hide(...))]`.
+    (removed, doc_cfg_hide, "1.57.0", Some(43781), Some("merged into `doc_cfg`"), 138907),
     /// Allows using `#[doc(keyword = "...")]`.
     (removed, doc_keyword, "1.58.0", Some(51315),
      Some("merged into `#![feature(rustdoc_internals)]`"), 90420),

compiler/rustc_feature/src/unstable.rs

@@ -472,12 +472,8 @@ declare_features! (
     (incomplete, deref_patterns, "1.79.0", Some(87121)),
     /// Allows deriving the From trait on single-field structs.
     (unstable, derive_from, "1.91.0", Some(144889)),
-    /// Tells rustdoc to automatically generate `#[doc(cfg(...))]`.
-    (unstable, doc_auto_cfg, "1.58.0", Some(43781)),
     /// Allows `#[doc(cfg(...))]`.
     (unstable, doc_cfg, "1.21.0", Some(43781)),
-    /// Allows `#[doc(cfg_hide(...))]`.
-    (unstable, doc_cfg_hide, "1.57.0", Some(43781)),
     /// Allows `#[doc(masked)]`.
     (unstable, doc_masked, "1.21.0", Some(44027)),
     /// Allows features to allow target_feature to better interact with traits.

compiler/rustc_passes/messages.ftl

@@ -140,8 +140,17 @@ passes_doc_attribute_not_attribute =
     nonexistent builtin attribute `{$attribute}` used in `#[doc(attribute = "...")]`
     .help = only existing builtin attributes are allowed in core/std
 
-passes_doc_cfg_hide_takes_list =
-    `#[doc(cfg_hide(...))]` takes a list of attributes
+passes_doc_auto_cfg_expects_hide_or_show =
+    only `hide` or `show` are allowed in `#[doc(auto_cfg(...))]`
+
+passes_doc_auto_cfg_hide_show_expects_list =
+    `#![doc(auto_cfg({$attr_name}(...)))]` expects a list of items
+
+passes_doc_auto_cfg_hide_show_unexpected_item =
+    `#![doc(auto_cfg({$attr_name}(...)))]` only accepts identifiers or key/value items
+
+passes_doc_auto_cfg_wrong_literal =
+    expected boolean for `#[doc(auto_cfg = ...)]`
 
 passes_doc_expect_str =
     doc {$attr_name} attribute expects a string: #[doc({$attr_name} = "a")]

compiler/rustc_passes/src/check_attr.rs

@@ -10,7 +10,7 @@ use std::collections::hash_map::Entry;
 use std::slice;
 
 use rustc_abi::{Align, ExternAbi, Size};
-use rustc_ast::{AttrStyle, LitKind, MetaItemInner, MetaItemKind, ast};
+use rustc_ast::{AttrStyle, LitKind, MetaItem, MetaItemInner, MetaItemKind, ast};
 use rustc_attr_parsing::{AttributeParser, Late};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::{Applicability, DiagCtxtHandle, IntoDiagArg, MultiSpan, StashKey};
@@ -1160,16 +1160,59 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
         }
     }
 
-    /// Check that the `#![doc(cfg_hide(...))]` attribute only contains a list of attributes.
-    ///
-    fn check_doc_cfg_hide(&self, meta: &MetaItemInner, hir_id: HirId) {
-        if meta.meta_item_list().is_none() {
-            self.tcx.emit_node_span_lint(
-                INVALID_DOC_ATTRIBUTES,
-                hir_id,
-                meta.span(),
-                errors::DocCfgHideTakesList,
-            );
+    /// Check that the `#![doc(auto_cfg)]` attribute has the expected input.
+    fn check_doc_auto_cfg(&self, meta: &MetaItem, hir_id: HirId) {
+        match &meta.kind {
+            MetaItemKind::Word => {}
+            MetaItemKind::NameValue(lit) => {
+                if !matches!(lit.kind, LitKind::Bool(_)) {
+                    self.tcx.emit_node_span_lint(
+                        INVALID_DOC_ATTRIBUTES,
+                        hir_id,
+                        meta.span,
+                        errors::DocAutoCfgWrongLiteral,
+                    );
+                }
+            }
+            MetaItemKind::List(list) => {
+                for item in list {
+                    let Some(attr_name @ (sym::hide | sym::show)) = item.name() else {
+                        self.tcx.emit_node_span_lint(
+                            INVALID_DOC_ATTRIBUTES,
+                            hir_id,
+                            meta.span,
+                            errors::DocAutoCfgExpectsHideOrShow,
+                        );
+                        continue;
+                    };
+                    if let Some(list) = item.meta_item_list() {
+                        for item in list {
+                            let valid = item.meta_item().is_some_and(|meta| {
+                                meta.path.segments.len() == 1
+                                    && matches!(
+                                        &meta.kind,
+                                        MetaItemKind::Word | MetaItemKind::NameValue(_)
+                                    )
+                            });
+                            if !valid {
+                                self.tcx.emit_node_span_lint(
+                                    INVALID_DOC_ATTRIBUTES,
+                                    hir_id,
+                                    item.span(),
+                                    errors::DocAutoCfgHideShowUnexpectedItem { attr_name },
+                                );
+                            }
+                        }
+                    } else {
+                        self.tcx.emit_node_span_lint(
+                            INVALID_DOC_ATTRIBUTES,
+                            hir_id,
+                            meta.span,
+                            errors::DocAutoCfgHideShowExpectsList { attr_name },
+                        );
+                    }
+                }
+            }
         }
     }
 
@@ -1245,10 +1288,8 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                             self.check_attr_crate_level(attr, style, meta, hir_id);
                         }
 
-                        Some(sym::cfg_hide) => {
-                            if self.check_attr_crate_level(attr, style, meta, hir_id) {
-                                self.check_doc_cfg_hide(meta, hir_id);
-                            }
+                        Some(sym::auto_cfg) => {
+                            self.check_doc_auto_cfg(i_meta, hir_id);
                         }
 
                         Some(sym::inline | sym::no_inline) => {

compiler/rustc_passes/src/errors.rs

@@ -309,8 +309,24 @@ pub(crate) struct DocTestLiteral;
 pub(crate) struct DocTestTakesList;
 
 #[derive(LintDiagnostic)]
-#[diag(passes_doc_cfg_hide_takes_list)]
-pub(crate) struct DocCfgHideTakesList;
+#[diag(passes_doc_auto_cfg_wrong_literal)]
+pub(crate) struct DocAutoCfgWrongLiteral;
+
+#[derive(LintDiagnostic)]
+#[diag(passes_doc_auto_cfg_expects_hide_or_show)]
+pub(crate) struct DocAutoCfgExpectsHideOrShow;
+
+#[derive(LintDiagnostic)]
+#[diag(passes_doc_auto_cfg_hide_show_expects_list)]
+pub(crate) struct DocAutoCfgHideShowExpectsList {
+    pub attr_name: Symbol,
+}
+
+#[derive(LintDiagnostic)]
+#[diag(passes_doc_auto_cfg_hide_show_unexpected_item)]
+pub(crate) struct DocAutoCfgHideShowUnexpectedItem {
+    pub attr_name: Symbol,
+}
 
 #[derive(LintDiagnostic)]
 #[diag(passes_doc_test_unknown_any)]

compiler/rustc_span/src/symbol.rs

@@ -545,6 +545,7 @@ symbols! {
         attributes,
         audit_that,
         augmented_assignments,
+        auto_cfg,
         auto_traits,
         autodiff,
         autodiff_forward,
@@ -628,7 +629,6 @@ symbols! {
         cfg_emscripten_wasm_eh,
         cfg_eval,
         cfg_fmt_debug,
-        cfg_hide,
         cfg_overflow_checks,
         cfg_panic,
         cfg_relocation_model,
@@ -1149,6 +1149,7 @@ symbols! {
         hashset_iter_ty,
         hexagon_target_feature,
         hidden,
+        hide,
         hint,
         homogeneous_aggregate,
         host,
@@ -1987,6 +1988,7 @@ symbols! {
         shl_assign,
         shorter_tail_lifetimes,
         should_panic,
+        show,
         shr,
         shr_assign,
         sig_dfl,

library/alloc/src/lib.rs

@@ -64,14 +64,7 @@
     issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/",
     test(no_crate_inject, attr(allow(unused_variables), deny(warnings)))
 )]
-#![doc(cfg_hide(
-    not(test),
-    no_global_oom_handling,
-    not(no_global_oom_handling),
-    not(no_rc),
-    not(no_sync),
-    target_has_atomic = "ptr"
-))]
+#![doc(auto_cfg(hide(no_global_oom_handling, no_rc, no_sync, target_has_atomic = "ptr")))]
 #![doc(rust_logo)]
 #![feature(rustdoc_internals)]
 #![no_std]
@@ -195,7 +188,6 @@
 //
 // Rustdoc features:
 #![feature(doc_cfg)]
-#![feature(doc_cfg_hide)]
 // Technically, this is a bug in rustdoc: rustdoc sees the documentation on `#[lang = slice_alloc]`
 // blocks is for `&[T]`, which also has documentation using this feature in `core`, and gets mad
 // that the feature-gate isn't enabled. Ideally, it wouldn't check for the feature gate for docs

library/core/src/lib.rs

@@ -51,7 +51,7 @@
     test(attr(allow(dead_code, deprecated, unused_variables, unused_mut)))
 )]
 #![doc(rust_logo)]
-#![doc(cfg_hide(
+#![doc(auto_cfg(hide(
     no_fp_fmt_parse,
     target_pointer_width = "16",
     target_pointer_width = "32",
@@ -71,7 +71,7 @@
     target_has_atomic_load_store = "32",
     target_has_atomic_load_store = "64",
     target_has_atomic_load_store = "ptr",
-))]
+)))]
 #![no_core]
 #![rustc_coherence_is_core]
 #![rustc_preserve_ub_checks]
@@ -149,7 +149,6 @@
 #![feature(deprecated_suggestion)]
 #![feature(derive_const)]
 #![feature(doc_cfg)]
-#![feature(doc_cfg_hide)]
 #![feature(doc_notable_trait)]
 #![feature(extern_types)]
 #![feature(f16)]

library/std/src/lib.rs

@@ -235,7 +235,7 @@
     test(attr(allow(dead_code, deprecated, unused_variables, unused_mut)))
 )]
 #![doc(rust_logo)]
-#![doc(cfg_hide(not(test), no_global_oom_handling, not(no_global_oom_handling)))]
+#![doc(auto_cfg(hide(no_global_oom_handling)))]
 // Don't link to std. We are std.
 #![no_std]
 // Tell the compiler to link to either panic_abort or panic_unwind
@@ -285,7 +285,6 @@
 #![feature(decl_macro)]
 #![feature(deprecated_suggestion)]
 #![feature(doc_cfg)]
-#![feature(doc_cfg_hide)]
 #![feature(doc_masked)]
 #![feature(doc_notable_trait)]
 #![feature(dropck_eyepatch)]