drustdoc-search: make unboxing a special-case type feature

Author: notriddle

Diff for: compiler/rustc_ast_passes/src/feature_gate.rs

@@ -218,6 +218,7 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
                     "meant for internal use only" {
                         keyword => rustdoc_internals
                         fake_variadic => rustdoc_internals
+                        search_unbox => rustdoc_internals
                     }
                 );
             }

Diff for: compiler/rustc_passes/messages.ftl

@@ -222,6 +222,9 @@ passes_doc_masked_only_extern_crate =
     .not_an_extern_crate_label = not an `extern crate` item
     .note = read <https://doc.rust-lang.org/unstable-book/language-features/doc-masked.html> for more information
 
+passes_doc_search_unbox_invalid =
+    `#[doc(search_unbox)]` should be used on generic structs and enums
+
 passes_doc_test_literal = `#![doc(test(...)]` does not take a literal
 
 passes_doc_test_takes_list =

Diff for: compiler/rustc_passes/src/check_attr.rs

@@ -11,11 +11,12 @@ use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::{Applicability, IntoDiagArg, MultiSpan};
 use rustc_errors::{DiagCtxtHandle, StashKey};
 use rustc_feature::{AttributeDuplicates, AttributeType, BuiltinAttribute, BUILTIN_ATTRIBUTE_MAP};
+use rustc_hir as hir;
 use rustc_hir::def_id::LocalModDefId;
 use rustc_hir::intravisit::{self, Visitor};
-use rustc_hir::{self as hir};
 use rustc_hir::{
-    self, FnSig, ForeignItem, HirId, Item, ItemKind, TraitItem, CRATE_HIR_ID, CRATE_OWNER_ID,
+    self, AssocItemKind, FnSig, ForeignItem, HirId, Item, ItemKind, TraitItem, CRATE_HIR_ID,
+    CRATE_OWNER_ID,
 };
 use rustc_hir::{MethodKind, Safety, Target};
 use rustc_macros::LintDiagnostic;
@@ -875,6 +876,30 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
         true
     }
 
+    fn check_doc_search_unbox(&self, meta: &NestedMetaItem, hir_id: HirId) -> bool {
+        let hir::Node::Item(item) = self.tcx.hir_node(hir_id) else {
+            self.dcx().emit_err(errors::DocSearchUnboxInvalid { span: meta.span() });
+            return false;
+        };
+        match item.kind {
+            ItemKind::Enum(_, generics) | ItemKind::Struct(_, generics)
+                if generics.params.len() != 0 =>
+            {
+                true
+            }
+            ItemKind::Trait(_, _, generics, _, items)
+                if generics.params.len() != 0
+                    || items.iter().any(|item| matches!(item.kind, AssocItemKind::Type)) =>
+            {
+                true
+            }
+            _ => {
+                self.dcx().emit_err(errors::DocSearchUnboxInvalid { span: meta.span() });
+                false
+            }
+        }
+    }
+
     /// Checks `#[doc(inline)]`/`#[doc(no_inline)]` attributes. Returns `true` if valid.
     ///
     /// A doc inlining attribute is invalid if it is applied to a non-`use` item, or
@@ -1108,6 +1133,13 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                             is_valid = false
                         }
 
+                        sym::search_unbox
+                            if !self.check_attr_not_crate_level(meta, hir_id, "search_unbox")
+                                || !self.check_doc_search_unbox(meta, hir_id) =>
+                        {
+                            is_valid = false
+                        }
+
                         sym::html_favicon_url
                         | sym::html_logo_url
                         | sym::html_playground_url
@@ -1165,6 +1197,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                         | sym::notable_trait
                         | sym::passes
                         | sym::plugins
+                        | sym::search_unbox
                         | sym::fake_variadic => {}
 
                         sym::rust_logo => {

Diff for: compiler/rustc_passes/src/errors.rs

@@ -234,6 +234,13 @@ pub struct DocKeywordOnlyImpl {
     pub span: Span,
 }
 
+#[derive(Diagnostic)]
+#[diag(passes_doc_search_unbox_invalid)]
+pub struct DocSearchUnboxInvalid {
+    #[primary_span]
+    pub span: Span,
+}
+
 #[derive(Diagnostic)]
 #[diag(passes_doc_inline_conflict)]
 #[help]

Diff for: compiler/rustc_span/src/symbol.rs

@@ -1702,6 +1702,7 @@ symbols! {
         saturating_add,
         saturating_div,
         saturating_sub,
+        search_unbox,
         self_in_typedefs,
         self_struct_ctor,
         semitransparent,

Diff for: library/alloc/src/boxed.rs

@@ -233,6 +233,7 @@ mod thin;
 #[lang = "owned_box"]
 #[fundamental]
 #[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(not(bootstrap), doc(search_unbox))]
 // The declaration of the `Box` struct must be kept in sync with the
 // compiler or ICEs will happen.
 pub struct Box<

Diff for: library/core/src/future/future.rs

@@ -25,6 +25,7 @@ use crate::task::{Context, Poll};
 /// [`async`]: ../../std/keyword.async.html
 /// [`Waker`]: crate::task::Waker
 #[doc(notable_trait)]
+#[cfg_attr(not(bootstrap), doc(search_unbox))]
 #[must_use = "futures do nothing unless you `.await` or poll them"]
 #[stable(feature = "futures_api", since = "1.36.0")]
 #[lang = "future_trait"]

Diff for: library/core/src/option.rs

@@ -571,6 +571,7 @@ use crate::{
 #[lang = "Option"]
 #[stable(feature = "rust1", since = "1.0.0")]
 #[allow(clippy::derived_hash_with_manual_eq)] // PartialEq is manually implemented equivalently
+#[cfg_attr(not(bootstrap), doc(search_unbox))]
 pub enum Option<T> {
     /// No value.
     #[lang = "None"]

Diff for: library/core/src/result.rs

@@ -524,6 +524,7 @@ use crate::{convert, fmt, hint};
 #[must_use = "this `Result` may be an `Err` variant, which should be handled"]
 #[rustc_diagnostic_item = "Result"]
 #[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(not(bootstrap), doc(search_unbox))]
 pub enum Result<T, E> {
     /// Contains the success value
     #[lang = "Ok"]