Rollup merge of #139039 - nnethercote:less-kw-Empty-4, r=petrochenkov

Reduce kw::Empty usage, part 4

Another step towards #137978.

r? `@petrochenkov`

4 files changed, 15 insertions, 10 deletions

diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs
index ada3151c3b8..cfc0369c598 100644
--- a/compiler/rustc_passes/src/check_attr.rs
+++ b/compiler/rustc_passes/src/check_attr.rs
@@ -35,7 +35,7 @@ use rustc_session::lint::builtin::{
     UNKNOWN_OR_MALFORMED_DIAGNOSTIC_ATTRIBUTES, UNUSED_ATTRIBUTES,
 };
 use rustc_session::parse::feature_err;
-use rustc_span::{BytePos, DUMMY_SP, Span, Symbol, kw, sym};
+use rustc_span::{BytePos, DUMMY_SP, Span, Symbol, edition, kw, sym};
 use rustc_trait_selection::error_reporting::InferCtxtErrorExt;
 use rustc_trait_selection::infer::{TyCtxtInferExt, ValuePairs};
 use rustc_trait_selection::traits::ObligationCtxt;
@@ -1038,14 +1038,14 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
             // FIXME: Once rustdoc can handle URL conflicts on case insensitive file systems, we
             // can remove the `SelfTy` case here, remove `sym::SelfTy`, and update the
             // `#[doc(keyword = "SelfTy")` attribute in `library/std/src/keyword_docs.rs`.
-            s <= kw::Union || s == sym::SelfTy
+            s.is_reserved(|| edition::LATEST_STABLE_EDITION) || s.is_weak() || s == sym::SelfTy
         }
 
-        let doc_keyword = meta.value_str().unwrap_or(kw::Empty);
-        if doc_keyword == kw::Empty {
-            self.doc_attr_str_error(meta, "keyword");
-            return;
-        }
+        let doc_keyword = match meta.value_str() {
+            Some(value) if value != kw::Empty => value,
+            _ => return self.doc_attr_str_error(meta, "keyword"),
+        };
+
         let item_kind = match self.tcx.hir_node(hir_id) {
             hir::Node::Item(item) => Some(&item.kind),
             _ => None,
diff --git a/compiler/rustc_resolve/src/diagnostics.rs b/compiler/rustc_resolve/src/diagnostics.rs
index 63ea8c4ced1..f7343b93281 100644
--- a/compiler/rustc_resolve/src/diagnostics.rs
+++ b/compiler/rustc_resolve/src/diagnostics.rs
@@ -1091,7 +1091,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                     ));
                 }
                 Scope::BuiltinAttrs => {
-                    let res = Res::NonMacroAttr(NonMacroAttrKind::Builtin(kw::Empty));
+                    let res = Res::NonMacroAttr(NonMacroAttrKind::Builtin(sym::dummy));
                     if filter_fn(res) {
                         suggestions.extend(
                             BUILTIN_ATTRIBUTES
diff --git a/compiler/rustc_span/src/hygiene.rs b/compiler/rustc_span/src/hygiene.rs
index e7a8dee27f5..9959e98e3dd 100644
--- a/compiler/rustc_span/src/hygiene.rs
+++ b/compiler/rustc_span/src/hygiene.rs
@@ -1440,7 +1440,8 @@ pub fn decode_syntax_context<D: Decoder, F: FnOnce(&mut D, u32) -> SyntaxContext
                 }
             }
             Entry::Vacant(entry) => {
-                // We are the first thread to start decoding. Mark the current thread as being progress.
+                // We are the first thread to start decoding. Mark the current thread as being
+                // progress.
                 context.local_in_progress.borrow_mut().insert(raw_id);
 
                 // Allocate and store SyntaxContext id *before* calling the decoder function,
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index 47dd80c432e..c6e570e524f 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -131,7 +131,7 @@ symbols! {
         // tidy-alphabetical-end
 
         // Weak keywords, have special meaning only in specific contexts.
-        // Matching predicates: none
+        // Matching predicates: `is_weak`
         // tidy-alphabetical-start
         Auto:               "auto",
         Builtin:            "builtin",
@@ -2725,6 +2725,10 @@ impl Symbol {
             || self.is_unused_keyword_conditional(edition)
     }
 
+    pub fn is_weak(self) -> bool {
+        self >= kw::Auto && self <= kw::Yeet
+    }
+
     /// A keyword or reserved identifier that can be used as a path segment.
     pub fn is_path_segment_keyword(self) -> bool {
         self == kw::Super