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-rw-r--r--compiler/rustc_attr/src/attributes/allow_unstable.rs49
-rw-r--r--compiler/rustc_attr/src/attributes/cfg.rs255
-rw-r--r--compiler/rustc_attr/src/attributes/confusables.rs22
-rw-r--r--compiler/rustc_attr/src/attributes/deprecation.rs149
-rw-r--r--compiler/rustc_attr/src/attributes/mod.rs17
-rw-r--r--compiler/rustc_attr/src/attributes/repr.rs216
-rw-r--r--compiler/rustc_attr/src/attributes/stability.rs385
-rw-r--r--compiler/rustc_attr/src/attributes/transparency.rs35
-rw-r--r--compiler/rustc_attr/src/attributes/util.rs36
-rw-r--r--compiler/rustc_attr/src/builtin.rs1349
-rw-r--r--compiler/rustc_attr/src/lib.rs35
-rw-r--r--compiler/rustc_attr/src/session_diagnostics.rs3
-rw-r--r--compiler/rustc_attr/src/types.rs262
-rw-r--r--compiler/rustc_codegen_ssa/src/base.rs5
-rw-r--r--compiler/rustc_codegen_ssa/src/codegen_attrs.rs3
-rw-r--r--compiler/rustc_expand/src/base.rs12
-rw-r--r--compiler/rustc_expand/src/config.rs2
-rw-r--r--compiler/rustc_expand/src/mbe/macro_rules.rs3
-rw-r--r--compiler/rustc_lint/src/levels.rs2
-rw-r--r--compiler/rustc_lint/src/nonstandard_style.rs9
-rw-r--r--compiler/rustc_metadata/src/rmeta/encoder.rs23
-rw-r--r--compiler/rustc_middle/src/middle/stability.rs4
-rw-r--r--compiler/rustc_passes/src/stability.rs26
-rw-r--r--compiler/rustc_resolve/src/build_reduced_graph.rs16
-rw-r--r--compiler/rustc_resolve/src/macros.rs3
-rw-r--r--compiler/rustc_resolve/src/rustdoc.rs2
-rw-r--r--src/librustdoc/clean/mod.rs8
-rw-r--r--src/librustdoc/clean/utils.rs3
-rw-r--r--src/tools/clippy/clippy_utils/src/msrvs.rs2
29 files changed, 1521 insertions, 1415 deletions
diff --git a/compiler/rustc_attr/src/attributes/allow_unstable.rs b/compiler/rustc_attr/src/attributes/allow_unstable.rs
new file mode 100644
index 00000000000..b9f841800ab
--- /dev/null
+++ b/compiler/rustc_attr/src/attributes/allow_unstable.rs
@@ -0,0 +1,49 @@
+use rustc_ast::attr::{AttributeExt, filter_by_name};
+use rustc_session::Session;
+use rustc_span::symbol::{Symbol, sym};
+
+use crate::session_diagnostics;
+
+pub fn allow_internal_unstable<'a>(
+    sess: &'a Session,
+    attrs: &'a [impl AttributeExt],
+) -> impl Iterator<Item = Symbol> + 'a {
+    allow_unstable(sess, attrs, sym::allow_internal_unstable)
+}
+
+pub fn rustc_allow_const_fn_unstable<'a>(
+    sess: &'a Session,
+    attrs: &'a [impl AttributeExt],
+) -> impl Iterator<Item = Symbol> + 'a {
+    allow_unstable(sess, attrs, sym::rustc_allow_const_fn_unstable)
+}
+
+fn allow_unstable<'a>(
+    sess: &'a Session,
+    attrs: &'a [impl AttributeExt],
+    symbol: Symbol,
+) -> impl Iterator<Item = Symbol> + 'a {
+    let attrs = filter_by_name(attrs, symbol);
+    let list = attrs
+        .filter_map(move |attr| {
+            attr.meta_item_list().or_else(|| {
+                sess.dcx().emit_err(session_diagnostics::ExpectsFeatureList {
+                    span: attr.span(),
+                    name: symbol.to_ident_string(),
+                });
+                None
+            })
+        })
+        .flatten();
+
+    list.into_iter().filter_map(move |it| {
+        let name = it.ident().map(|ident| ident.name);
+        if name.is_none() {
+            sess.dcx().emit_err(session_diagnostics::ExpectsFeatures {
+                span: it.span(),
+                name: symbol.to_ident_string(),
+            });
+        }
+        name
+    })
+}
diff --git a/compiler/rustc_attr/src/attributes/cfg.rs b/compiler/rustc_attr/src/attributes/cfg.rs
new file mode 100644
index 00000000000..2dfdb2e61b4
--- /dev/null
+++ b/compiler/rustc_attr/src/attributes/cfg.rs
@@ -0,0 +1,255 @@
+//! Parsing and validation of builtin attributes
+
+use rustc_ast::{self as ast, LitKind, MetaItem, MetaItemInner, MetaItemKind, MetaItemLit, NodeId};
+use rustc_ast_pretty::pprust;
+use rustc_feature::{Features, GatedCfg, find_gated_cfg};
+use rustc_session::RustcVersion;
+use rustc_session::Session;
+use rustc_session::config::ExpectedValues;
+use rustc_session::lint::BuiltinLintDiag;
+use rustc_session::lint::builtin::UNEXPECTED_CFGS;
+use rustc_session::parse::feature_err;
+use rustc_span::Span;
+use rustc_span::symbol::{Symbol, kw, sym};
+
+use crate::{fluent_generated, parse_version};
+use crate::session_diagnostics;
+use crate::util::UnsupportedLiteralReason;
+
+#[derive(Clone, Debug)]
+pub struct Condition {
+    pub name: Symbol,
+    pub name_span: Span,
+    pub value: Option<Symbol>,
+    pub value_span: Option<Span>,
+    pub span: Span,
+}
+
+/// Tests if a cfg-pattern matches the cfg set
+pub fn cfg_matches(
+    cfg: &ast::MetaItemInner,
+    sess: &Session,
+    lint_node_id: NodeId,
+    features: Option<&Features>,
+) -> bool {
+    eval_condition(cfg, sess, features, &mut |cfg| {
+        try_gate_cfg(cfg.name, cfg.span, sess, features);
+        match sess.psess.check_config.expecteds.get(&cfg.name) {
+            Some(ExpectedValues::Some(values)) if !values.contains(&cfg.value) => {
+                sess.psess.buffer_lint(
+                    UNEXPECTED_CFGS,
+                    cfg.span,
+                    lint_node_id,
+                    BuiltinLintDiag::UnexpectedCfgValue(
+                        (cfg.name, cfg.name_span),
+                        cfg.value.map(|v| (v, cfg.value_span.unwrap())),
+                    ),
+                );
+            }
+            None if sess.psess.check_config.exhaustive_names => {
+                sess.psess.buffer_lint(
+                    UNEXPECTED_CFGS,
+                    cfg.span,
+                    lint_node_id,
+                    BuiltinLintDiag::UnexpectedCfgName(
+                        (cfg.name, cfg.name_span),
+                        cfg.value.map(|v| (v, cfg.value_span.unwrap())),
+                    ),
+                );
+            }
+            _ => { /* not unexpected */ }
+        }
+        sess.psess.config.contains(&(cfg.name, cfg.value))
+    })
+}
+
+fn try_gate_cfg(name: Symbol, span: Span, sess: &Session, features: Option<&Features>) {
+    let gate = find_gated_cfg(|sym| sym == name);
+    if let (Some(feats), Some(gated_cfg)) = (features, gate) {
+        gate_cfg(gated_cfg, span, sess, feats);
+    }
+}
+
+#[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
+fn gate_cfg(gated_cfg: &GatedCfg, cfg_span: Span, sess: &Session, features: &Features) {
+    let (cfg, feature, has_feature) = gated_cfg;
+    if !has_feature(features) && !cfg_span.allows_unstable(*feature) {
+        let explain = format!("`cfg({cfg})` is experimental and subject to change");
+        feature_err(sess, *feature, cfg_span, explain).emit();
+    }
+}
+
+/// Evaluate a cfg-like condition (with `any` and `all`), using `eval` to
+/// evaluate individual items.
+pub fn eval_condition(
+    cfg: &ast::MetaItemInner,
+    sess: &Session,
+    features: Option<&Features>,
+    eval: &mut impl FnMut(Condition) -> bool,
+) -> bool {
+    let dcx = sess.dcx();
+
+    let cfg = match cfg {
+        ast::MetaItemInner::MetaItem(meta_item) => meta_item,
+        ast::MetaItemInner::Lit(MetaItemLit { kind: LitKind::Bool(b), .. }) => {
+            if let Some(features) = features {
+                // we can't use `try_gate_cfg` as symbols don't differentiate between `r#true`
+                // and `true`, and we want to keep the former working without feature gate
+                gate_cfg(
+                    &(
+                        if *b { kw::True } else { kw::False },
+                        sym::cfg_boolean_literals,
+                        |features: &Features| features.cfg_boolean_literals(),
+                    ),
+                    cfg.span(),
+                    sess,
+                    features,
+                );
+            }
+            return *b;
+        }
+        _ => {
+            dcx.emit_err(session_diagnostics::UnsupportedLiteral {
+                span: cfg.span(),
+                reason: UnsupportedLiteralReason::CfgBoolean,
+                is_bytestr: false,
+                start_point_span: sess.source_map().start_point(cfg.span()),
+            });
+            return false;
+        }
+    };
+
+    match &cfg.kind {
+        ast::MetaItemKind::List(mis) if cfg.name_or_empty() == sym::version => {
+            try_gate_cfg(sym::version, cfg.span, sess, features);
+            let (min_version, span) = match &mis[..] {
+                [MetaItemInner::Lit(MetaItemLit { kind: LitKind::Str(sym, ..), span, .. })] => {
+                    (sym, span)
+                }
+                [
+                    MetaItemInner::Lit(MetaItemLit { span, .. })
+                    | MetaItemInner::MetaItem(MetaItem { span, .. }),
+                ] => {
+                    dcx.emit_err(session_diagnostics::ExpectedVersionLiteral { span: *span });
+                    return false;
+                }
+                [..] => {
+                    dcx.emit_err(session_diagnostics::ExpectedSingleVersionLiteral {
+                        span: cfg.span,
+                    });
+                    return false;
+                }
+            };
+            let Some(min_version) = parse_version(*min_version) else {
+                dcx.emit_warn(session_diagnostics::UnknownVersionLiteral { span: *span });
+                return false;
+            };
+
+            // See https://github.com/rust-lang/rust/issues/64796#issuecomment-640851454 for details
+            if sess.psess.assume_incomplete_release {
+                RustcVersion::CURRENT > min_version
+            } else {
+                RustcVersion::CURRENT >= min_version
+            }
+        }
+        ast::MetaItemKind::List(mis) => {
+            for mi in mis.iter() {
+                if mi.meta_item_or_bool().is_none() {
+                    dcx.emit_err(session_diagnostics::UnsupportedLiteral {
+                        span: mi.span(),
+                        reason: UnsupportedLiteralReason::Generic,
+                        is_bytestr: false,
+                        start_point_span: sess.source_map().start_point(mi.span()),
+                    });
+                    return false;
+                }
+            }
+
+            // The unwraps below may look dangerous, but we've already asserted
+            // that they won't fail with the loop above.
+            match cfg.name_or_empty() {
+                sym::any => mis
+                    .iter()
+                    // We don't use any() here, because we want to evaluate all cfg condition
+                    // as eval_condition can (and does) extra checks
+                    .fold(false, |res, mi| res | eval_condition(mi, sess, features, eval)),
+                sym::all => mis
+                    .iter()
+                    // We don't use all() here, because we want to evaluate all cfg condition
+                    // as eval_condition can (and does) extra checks
+                    .fold(true, |res, mi| res & eval_condition(mi, sess, features, eval)),
+                sym::not => {
+                    let [mi] = mis.as_slice() else {
+                        dcx.emit_err(session_diagnostics::ExpectedOneCfgPattern { span: cfg.span });
+                        return false;
+                    };
+
+                    !eval_condition(mi, sess, features, eval)
+                }
+                sym::target => {
+                    if let Some(features) = features
+                        && !features.cfg_target_compact()
+                    {
+                        feature_err(
+                            sess,
+                            sym::cfg_target_compact,
+                            cfg.span,
+                            fluent_generated::attr_unstable_cfg_target_compact,
+                        )
+                        .emit();
+                    }
+
+                    mis.iter().fold(true, |res, mi| {
+                        let Some(mut mi) = mi.meta_item().cloned() else {
+                            dcx.emit_err(session_diagnostics::CfgPredicateIdentifier {
+                                span: mi.span(),
+                            });
+                            return false;
+                        };
+
+                        if let [seg, ..] = &mut mi.path.segments[..] {
+                            seg.ident.name = Symbol::intern(&format!("target_{}", seg.ident.name));
+                        }
+
+                        res & eval_condition(
+                            &ast::MetaItemInner::MetaItem(mi),
+                            sess,
+                            features,
+                            eval,
+                        )
+                    })
+                }
+                _ => {
+                    dcx.emit_err(session_diagnostics::InvalidPredicate {
+                        span: cfg.span,
+                        predicate: pprust::path_to_string(&cfg.path),
+                    });
+                    false
+                }
+            }
+        }
+        ast::MetaItemKind::Word | MetaItemKind::NameValue(..) if cfg.path.segments.len() != 1 => {
+            dcx.emit_err(session_diagnostics::CfgPredicateIdentifier { span: cfg.path.span });
+            true
+        }
+        MetaItemKind::NameValue(lit) if !lit.kind.is_str() => {
+            dcx.emit_err(session_diagnostics::UnsupportedLiteral {
+                span: lit.span,
+                reason: UnsupportedLiteralReason::CfgString,
+                is_bytestr: lit.kind.is_bytestr(),
+                start_point_span: sess.source_map().start_point(lit.span),
+            });
+            true
+        }
+        ast::MetaItemKind::Word | ast::MetaItemKind::NameValue(..) => {
+            let ident = cfg.ident().expect("multi-segment cfg predicate");
+            eval(Condition {
+                name: ident.name,
+                name_span: ident.span,
+                value: cfg.value_str(),
+                value_span: cfg.name_value_literal_span(),
+                span: cfg.span,
+            })
+        }
+    }
+}
diff --git a/compiler/rustc_attr/src/attributes/confusables.rs b/compiler/rustc_attr/src/attributes/confusables.rs
new file mode 100644
index 00000000000..988cb32f244
--- /dev/null
+++ b/compiler/rustc_attr/src/attributes/confusables.rs
@@ -0,0 +1,22 @@
+//! Parsing and validation of builtin attributes
+
+use rustc_ast::attr::AttributeExt;
+use rustc_ast::MetaItemInner;
+use rustc_span::symbol::Symbol;
+
+
+/// Read the content of a `rustc_confusables` attribute, and return the list of candidate names.
+pub fn parse_confusables(attr: &impl AttributeExt) -> Option<Vec<Symbol>> {
+    let metas = attr.meta_item_list()?;
+
+    let mut candidates = Vec::new();
+
+    for meta in metas {
+        let MetaItemInner::Lit(meta_lit) = meta else {
+            return None;
+        };
+        candidates.push(meta_lit.symbol);
+    }
+
+    Some(candidates)
+}
diff --git a/compiler/rustc_attr/src/attributes/deprecation.rs b/compiler/rustc_attr/src/attributes/deprecation.rs
new file mode 100644
index 00000000000..c7f13fef276
--- /dev/null
+++ b/compiler/rustc_attr/src/attributes/deprecation.rs
@@ -0,0 +1,149 @@
+//! Parsing and validation of builtin attributes
+
+use rustc_ast::attr::AttributeExt;
+use rustc_ast::{MetaItemInner, MetaItem};
+use rustc_ast_pretty::pprust;
+use rustc_feature::Features;
+use crate::types::{DeprecatedSince, Deprecation};
+use rustc_session::Session;
+use rustc_span::Span;
+use rustc_span::symbol::{Symbol, sym};
+use crate::{parse_version, session_diagnostics};
+
+use super::util::UnsupportedLiteralReason;
+
+/// Finds the deprecation attribute. `None` if none exists.
+pub fn find_deprecation(
+    sess: &Session,
+    features: &Features,
+    attrs: &[impl AttributeExt],
+) -> Option<(Deprecation, Span)> {
+    let mut depr: Option<(Deprecation, Span)> = None;
+    let is_rustc = features.staged_api();
+
+    'outer: for attr in attrs {
+        if !attr.has_name(sym::deprecated) {
+            continue;
+        }
+
+        let mut since = None;
+        let mut note = None;
+        let mut suggestion = None;
+
+        if attr.is_doc_comment() {
+            continue;
+        } else if attr.is_word() {
+        } else if let Some(value) = attr.value_str() {
+            note = Some(value)
+        } else if let Some(list) = attr.meta_item_list() {
+            let get = |meta: &MetaItem, item: &mut Option<Symbol>| {
+                if item.is_some() {
+                    sess.dcx().emit_err(session_diagnostics::MultipleItem {
+                        span: meta.span,
+                        item: pprust::path_to_string(&meta.path),
+                    });
+                    return false;
+                }
+                if let Some(v) = meta.value_str() {
+                    *item = Some(v);
+                    true
+                } else {
+                    if let Some(lit) = meta.name_value_literal() {
+                        sess.dcx().emit_err(session_diagnostics::UnsupportedLiteral {
+                            span: lit.span,
+                            reason: UnsupportedLiteralReason::DeprecatedString,
+                            is_bytestr: lit.kind.is_bytestr(),
+                            start_point_span: sess.source_map().start_point(lit.span),
+                        });
+                    } else {
+                        sess.dcx()
+                            .emit_err(session_diagnostics::IncorrectMetaItem { span: meta.span });
+                    }
+                    false
+                }
+            };
+
+            for meta in &list {
+                match meta {
+                    MetaItemInner::MetaItem(mi) => match mi.name_or_empty() {
+                        sym::since => {
+                            if !get(mi, &mut since) {
+                                continue 'outer;
+                            }
+                        }
+                        sym::note => {
+                            if !get(mi, &mut note) {
+                                continue 'outer;
+                            }
+                        }
+                        sym::suggestion => {
+                            if !features.deprecated_suggestion() {
+                                sess.dcx().emit_err(
+                                    session_diagnostics::DeprecatedItemSuggestion {
+                                        span: mi.span,
+                                        is_nightly: sess.is_nightly_build(),
+                                        details: (),
+                                    },
+                                );
+                            }
+
+                            if !get(mi, &mut suggestion) {
+                                continue 'outer;
+                            }
+                        }
+                        _ => {
+                            sess.dcx().emit_err(session_diagnostics::UnknownMetaItem {
+                                span: meta.span(),
+                                item: pprust::path_to_string(&mi.path),
+                                expected: if features.deprecated_suggestion() {
+                                    &["since", "note", "suggestion"]
+                                } else {
+                                    &["since", "note"]
+                                },
+                            });
+                            continue 'outer;
+                        }
+                    },
+                    MetaItemInner::Lit(lit) => {
+                        sess.dcx().emit_err(session_diagnostics::UnsupportedLiteral {
+                            span: lit.span,
+                            reason: UnsupportedLiteralReason::DeprecatedKvPair,
+                            is_bytestr: false,
+                            start_point_span: sess.source_map().start_point(lit.span),
+                        });
+                        continue 'outer;
+                    }
+                }
+            }
+        } else {
+            continue;
+        }
+
+        let since = if let Some(since) = since {
+            if since.as_str() == "TBD" {
+                DeprecatedSince::Future
+            } else if !is_rustc {
+                DeprecatedSince::NonStandard(since)
+            } else if let Some(version) = parse_version(since) {
+                DeprecatedSince::RustcVersion(version)
+            } else {
+                sess.dcx().emit_err(session_diagnostics::InvalidSince { span: attr.span() });
+                DeprecatedSince::Err
+            }
+        } else if is_rustc {
+            sess.dcx().emit_err(session_diagnostics::MissingSince { span: attr.span() });
+            DeprecatedSince::Err
+        } else {
+            DeprecatedSince::Unspecified
+        };
+
+        if is_rustc && note.is_none() {
+            sess.dcx().emit_err(session_diagnostics::MissingNote { span: attr.span() });
+            continue;
+        }
+
+        depr = Some((Deprecation { since, note, suggestion }, attr.span()));
+    }
+
+    depr
+}
diff --git a/compiler/rustc_attr/src/attributes/mod.rs b/compiler/rustc_attr/src/attributes/mod.rs
new file mode 100644
index 00000000000..a78e0b54b64
--- /dev/null
+++ b/compiler/rustc_attr/src/attributes/mod.rs
@@ -0,0 +1,17 @@
+mod allow_unstable;
+mod cfg;
+mod confusables;
+mod deprecation;
+mod repr;
+mod stability;
+mod transparency;
+
+pub mod util;
+
+pub use allow_unstable::*;
+pub use cfg::*;
+pub use confusables::*;
+pub use deprecation::*;
+pub use repr::*;
+pub use stability::*;
+pub use transparency::*;
diff --git a/compiler/rustc_attr/src/attributes/repr.rs b/compiler/rustc_attr/src/attributes/repr.rs
new file mode 100644
index 00000000000..803aeabaf18
--- /dev/null
+++ b/compiler/rustc_attr/src/attributes/repr.rs
@@ -0,0 +1,216 @@
+//! Parsing and validation of builtin attributes
+
+use rustc_abi::Align;
+use rustc_ast::attr::AttributeExt;
+use rustc_ast::{self as ast, MetaItemKind};
+use crate::types::{
+    IntType, ReprAttr::*,
+};
+use crate::ReprAttr;
+use rustc_session::Session;
+use rustc_span::symbol::{Symbol, sym};
+use crate::session_diagnostics::{self, IncorrectReprFormatGenericCause};
+
+
+/// Parse #[repr(...)] forms.
+///
+/// Valid repr contents: any of the primitive integral type names (see
+/// `int_type_of_word`, below) to specify enum discriminant type; `C`, to use
+/// the same discriminant size that the corresponding C enum would or C
+/// structure layout, `packed` to remove padding, and `transparent` to delegate representation
+/// concerns to the only non-ZST field.
+pub fn find_repr_attrs(sess: &Session, attr: &impl AttributeExt) -> Vec<ReprAttr> {
+    if attr.has_name(sym::repr) { parse_repr_attr(sess, attr) } else { Vec::new() }
+}
+
+pub fn parse_repr_attr(sess: &Session, attr: &impl AttributeExt) -> Vec<ReprAttr> {
+    assert!(attr.has_name(sym::repr), "expected `#[repr(..)]`, found: {attr:?}");
+    let mut acc = Vec::new();
+    let dcx = sess.dcx();
+
+    if let Some(items) = attr.meta_item_list() {
+        for item in items {
+            let mut recognised = false;
+            if item.is_word() {
+                let hint = match item.name_or_empty() {
+                    sym::Rust => Some(ReprRust),
+                    sym::C => Some(ReprC),
+                    sym::packed => Some(ReprPacked(Align::ONE)),
+                    sym::simd => Some(ReprSimd),
+                    sym::transparent => Some(ReprTransparent),
+                    sym::align => {
+                        sess.dcx().emit_err(session_diagnostics::InvalidReprAlignNeedArg {
+                            span: item.span(),
+                        });
+                        recognised = true;
+                        None
+                    }
+                    name => int_type_of_word(name).map(ReprInt),
+                };
+
+                if let Some(h) = hint {
+                    recognised = true;
+                    acc.push(h);
+                }
+            } else if let Some((name, value)) = item.singleton_lit_list() {
+                let mut literal_error = None;
+                let mut err_span = item.span();
+                if name == sym::align {
+                    recognised = true;
+                    match parse_alignment(&value.kind) {
+                        Ok(literal) => acc.push(ReprAlign(literal)),
+                        Err(message) => {
+                            err_span = value.span;
+                            literal_error = Some(message)
+                        }
+                    };
+                } else if name == sym::packed {
+                    recognised = true;
+                    match parse_alignment(&value.kind) {
+                        Ok(literal) => acc.push(ReprPacked(literal)),
+                        Err(message) => {
+                            err_span = value.span;
+                            literal_error = Some(message)
+                        }
+                    };
+                } else if matches!(name, sym::Rust | sym::C | sym::simd | sym::transparent)
+                    || int_type_of_word(name).is_some()
+                {
+                    recognised = true;
+                    sess.dcx().emit_err(session_diagnostics::InvalidReprHintNoParen {
+                        span: item.span(),
+                        name: name.to_ident_string(),
+                    });
+                }
+                if let Some(literal_error) = literal_error {
+                    sess.dcx().emit_err(session_diagnostics::InvalidReprGeneric {
+                        span: err_span,
+                        repr_arg: name.to_ident_string(),
+                        error_part: literal_error,
+                    });
+                }
+            } else if let Some(meta_item) = item.meta_item() {
+                match &meta_item.kind {
+                    MetaItemKind::NameValue(value) => {
+                        if meta_item.has_name(sym::align) || meta_item.has_name(sym::packed) {
+                            let name = meta_item.name_or_empty().to_ident_string();
+                            recognised = true;
+                            sess.dcx().emit_err(session_diagnostics::IncorrectReprFormatGeneric {
+                                span: item.span(),
+                                repr_arg: &name,
+                                cause: IncorrectReprFormatGenericCause::from_lit_kind(
+                                    item.span(),
+                                    &value.kind,
+                                    &name,
+                                ),
+                            });
+                        } else if matches!(
+                            meta_item.name_or_empty(),
+                            sym::Rust | sym::C | sym::simd | sym::transparent
+                        ) || int_type_of_word(meta_item.name_or_empty()).is_some()
+                        {
+                            recognised = true;
+                            sess.dcx().emit_err(session_diagnostics::InvalidReprHintNoValue {
+                                span: meta_item.span,
+                                name: meta_item.name_or_empty().to_ident_string(),
+                            });
+                        }
+                    }
+                    MetaItemKind::List(nested_items) => {
+                        if meta_item.has_name(sym::align) {
+                            recognised = true;
+                            if let [nested_item] = nested_items.as_slice() {
+                                sess.dcx().emit_err(
+                                    session_diagnostics::IncorrectReprFormatExpectInteger {
+                                        span: nested_item.span(),
+                                    },
+                                );
+                            } else {
+                                sess.dcx().emit_err(
+                                    session_diagnostics::IncorrectReprFormatAlignOneArg {
+                                        span: meta_item.span,
+                                    },
+                                );
+                            }
+                        } else if meta_item.has_name(sym::packed) {
+                            recognised = true;
+                            if let [nested_item] = nested_items.as_slice() {
+                                sess.dcx().emit_err(
+                                    session_diagnostics::IncorrectReprFormatPackedExpectInteger {
+                                        span: nested_item.span(),
+                                    },
+                                );
+                            } else {
+                                sess.dcx().emit_err(
+                                    session_diagnostics::IncorrectReprFormatPackedOneOrZeroArg {
+                                        span: meta_item.span,
+                                    },
+                                );
+                            }
+                        } else if matches!(
+                            meta_item.name_or_empty(),
+                            sym::Rust | sym::C | sym::simd | sym::transparent
+                        ) || int_type_of_word(meta_item.name_or_empty()).is_some()
+                        {
+                            recognised = true;
+                            sess.dcx().emit_err(session_diagnostics::InvalidReprHintNoParen {
+                                span: meta_item.span,
+                                name: meta_item.name_or_empty().to_ident_string(),
+                            });
+                        }
+                    }
+                    _ => (),
+                }
+            }
+            if !recognised {
+                // Not a word we recognize. This will be caught and reported by
+                // the `check_mod_attrs` pass, but this pass doesn't always run
+                // (e.g. if we only pretty-print the source), so we have to gate
+                // the `span_delayed_bug` call as follows:
+                if sess.opts.pretty.map_or(true, |pp| pp.needs_analysis()) {
+                    dcx.span_delayed_bug(item.span(), "unrecognized representation hint");
+                }
+            }
+        }
+    }
+    acc
+}
+
+fn int_type_of_word(s: Symbol) -> Option<IntType> {
+    use crate::types::IntType::*;
+
+    match s {
+        sym::i8 => Some(SignedInt(ast::IntTy::I8)),
+        sym::u8 => Some(UnsignedInt(ast::UintTy::U8)),
+        sym::i16 => Some(SignedInt(ast::IntTy::I16)),
+        sym::u16 => Some(UnsignedInt(ast::UintTy::U16)),
+        sym::i32 => Some(SignedInt(ast::IntTy::I32)),
+        sym::u32 => Some(UnsignedInt(ast::UintTy::U32)),
+        sym::i64 => Some(SignedInt(ast::IntTy::I64)),
+        sym::u64 => Some(UnsignedInt(ast::UintTy::U64)),
+        sym::i128 => Some(SignedInt(ast::IntTy::I128)),
+        sym::u128 => Some(UnsignedInt(ast::UintTy::U128)),
+        sym::isize => Some(SignedInt(ast::IntTy::Isize)),
+        sym::usize => Some(UnsignedInt(ast::UintTy::Usize)),
+        _ => None,
+    }
+}
+
+pub fn parse_alignment(node: &ast::LitKind) -> Result<Align, &'static str> {
+    if let ast::LitKind::Int(literal, ast::LitIntType::Unsuffixed) = node {
+        // `Align::from_bytes` accepts 0 as an input, check is_power_of_two() first
+        if literal.get().is_power_of_two() {
+            // Only possible error is larger than 2^29
+            literal
+                .get()
+                .try_into()
+                .ok()
+                .and_then(|v| Align::from_bytes(v).ok())
+                .ok_or("larger than 2^29")
+        } else {
+            Err("not a power of two")
+        }
+    } else {
+        Err("not an unsuffixed integer")
+    }
+}
diff --git a/compiler/rustc_attr/src/attributes/stability.rs b/compiler/rustc_attr/src/attributes/stability.rs
new file mode 100644
index 00000000000..01f10d927a3
--- /dev/null
+++ b/compiler/rustc_attr/src/attributes/stability.rs
@@ -0,0 +1,385 @@
+//! Parsing and validation of builtin attributes
+
+use std::num::NonZero;
+
+use rustc_ast::attr::AttributeExt;
+use rustc_ast::MetaItem;
+use rustc_ast_pretty::pprust;
+use rustc_errors::ErrorGuaranteed;
+use crate::types::{
+    ConstStability, DefaultBodyStability,
+    Stability, StabilityLevel, StableSince, UnstableReason, VERSION_PLACEHOLDER,
+};
+use rustc_session::Session;
+use rustc_span::Span;
+use rustc_span::symbol::{Symbol, sym};
+
+use crate::{parse_version, session_diagnostics};
+use crate::attributes::util::UnsupportedLiteralReason;
+
+/// Collects stability info from `stable`/`unstable`/`rustc_allowed_through_unstable_modules`
+/// attributes in `attrs`. Returns `None` if no stability attributes are found.
+pub fn find_stability(
+    sess: &Session,
+    attrs: &[impl AttributeExt],
+    item_sp: Span,
+) -> Option<(Stability, Span)> {
+    let mut stab: Option<(Stability, Span)> = None;
+    let mut allowed_through_unstable_modules = false;
+
+    for attr in attrs {
+        match attr.name_or_empty() {
+            sym::rustc_allowed_through_unstable_modules => allowed_through_unstable_modules = true,
+            sym::unstable => {
+                if stab.is_some() {
+                    sess.dcx().emit_err(session_diagnostics::MultipleStabilityLevels {
+                        span: attr.span(),
+                    });
+                    break;
+                }
+
+                if let Some((feature, level)) = parse_unstability(sess, attr) {
+                    stab = Some((Stability { level, feature }, attr.span()));
+                }
+            }
+            sym::stable => {
+                if stab.is_some() {
+                    sess.dcx().emit_err(session_diagnostics::MultipleStabilityLevels {
+                        span: attr.span(),
+                    });
+                    break;
+                }
+                if let Some((feature, level)) = parse_stability(sess, attr) {
+                    stab = Some((Stability { level, feature }, attr.span()));
+                }
+            }
+            _ => {}
+        }
+    }
+
+    if allowed_through_unstable_modules {
+        match &mut stab {
+            Some((
+                Stability {
+                    level: StabilityLevel::Stable { allowed_through_unstable_modules, .. },
+                    ..
+                },
+                _,
+            )) => *allowed_through_unstable_modules = true,
+            _ => {
+                sess.dcx()
+                    .emit_err(session_diagnostics::RustcAllowedUnstablePairing { span: item_sp });
+            }
+        }
+    }
+
+    stab
+}
+
+/// Collects stability info from `rustc_const_stable`/`rustc_const_unstable`/`rustc_promotable`
+/// attributes in `attrs`. Returns `None` if no stability attributes are found.
+pub fn find_const_stability(
+    sess: &Session,
+    attrs: &[impl AttributeExt],
+    item_sp: Span,
+) -> Option<(ConstStability, Span)> {
+    let mut const_stab: Option<(ConstStability, Span)> = None;
+    let mut promotable = false;
+    let mut const_stable_indirect = false;
+
+    for attr in attrs {
+        match attr.name_or_empty() {
+            sym::rustc_promotable => promotable = true,
+            sym::rustc_const_stable_indirect => const_stable_indirect = true,
+            sym::rustc_const_unstable => {
+                if const_stab.is_some() {
+                    sess.dcx().emit_err(session_diagnostics::MultipleStabilityLevels {
+                        span: attr.span(),
+                    });
+                    break;
+                }
+
+                if let Some((feature, level)) = parse_unstability(sess, attr) {
+                    const_stab = Some((
+                        ConstStability {
+                            level,
+                            feature,
+                            const_stable_indirect: false,
+                            promotable: false,
+                        },
+                        attr.span(),
+                    ));
+                }
+            }
+            sym::rustc_const_stable => {
+                if const_stab.is_some() {
+                    sess.dcx().emit_err(session_diagnostics::MultipleStabilityLevels {
+                        span: attr.span(),
+                    });
+                    break;
+                }
+                if let Some((feature, level)) = parse_stability(sess, attr) {
+                    const_stab = Some((
+                        ConstStability {
+                            level,
+                            feature,
+                            const_stable_indirect: false,
+                            promotable: false,
+                        },
+                        attr.span(),
+                    ));
+                }
+            }
+            _ => {}
+        }
+    }
+
+    // Merge promotable and const_stable_indirect into stability info
+    if promotable {
+        match &mut const_stab {
+            Some((stab, _)) => stab.promotable = promotable,
+            _ => {
+                _ = sess
+                    .dcx()
+                    .emit_err(session_diagnostics::RustcPromotablePairing { span: item_sp })
+            }
+        }
+    }
+    if const_stable_indirect {
+        match &mut const_stab {
+            Some((stab, _)) => {
+                if stab.is_const_unstable() {
+                    stab.const_stable_indirect = true;
+                } else {
+                    _ = sess.dcx().emit_err(session_diagnostics::RustcConstStableIndirectPairing {
+                        span: item_sp,
+                    })
+                }
+            }
+            _ => {
+                // This function has no const stability attribute, but has `const_stable_indirect`.
+                // We ignore that; unmarked functions are subject to recursive const stability
+                // checks by default so we do carry out the user's intent.
+            }
+        }
+    }
+
+    const_stab
+}
+
+/// Calculates the const stability for a const function in a `-Zforce-unstable-if-unmarked` crate
+/// without the `staged_api` feature.
+pub fn unmarked_crate_const_stab(
+    _sess: &Session,
+    attrs: &[impl AttributeExt],
+    regular_stab: Stability,
+) -> ConstStability {
+    assert!(regular_stab.level.is_unstable());
+    // The only attribute that matters here is `rustc_const_stable_indirect`.
+    // We enforce recursive const stability rules for those functions.
+    let const_stable_indirect =
+        attrs.iter().any(|a| a.name_or_empty() == sym::rustc_const_stable_indirect);
+    ConstStability {
+        feature: regular_stab.feature,
+        const_stable_indirect,
+        promotable: false,
+        level: regular_stab.level,
+    }
+}
+
+/// Collects stability info from `rustc_default_body_unstable` attributes in `attrs`.
+/// Returns `None` if no stability attributes are found.
+pub fn find_body_stability(
+    sess: &Session,
+    attrs: &[impl AttributeExt],
+) -> Option<(DefaultBodyStability, Span)> {
+    let mut body_stab: Option<(DefaultBodyStability, Span)> = None;
+
+    for attr in attrs {
+        if attr.has_name(sym::rustc_default_body_unstable) {
+            if body_stab.is_some() {
+                sess.dcx()
+                    .emit_err(session_diagnostics::MultipleStabilityLevels { span: attr.span() });
+                break;
+            }
+
+            if let Some((feature, level)) = parse_unstability(sess, attr) {
+                body_stab = Some((DefaultBodyStability { level, feature }, attr.span()));
+            }
+        }
+    }
+
+    body_stab
+}
+
+fn insert_or_error(sess: &Session, meta: &MetaItem, item: &mut Option<Symbol>) -> Option<()> {
+    if item.is_some() {
+        sess.dcx().emit_err(session_diagnostics::MultipleItem {
+            span: meta.span,
+            item: pprust::path_to_string(&meta.path),
+        });
+        None
+    } else if let Some(v) = meta.value_str() {
+        *item = Some(v);
+        Some(())
+    } else {
+        sess.dcx().emit_err(session_diagnostics::IncorrectMetaItem { span: meta.span });
+        None
+    }
+}
+
+/// Read the content of a `stable`/`rustc_const_stable` attribute, and return the feature name and
+/// its stability information.
+fn parse_stability(sess: &Session, attr: &impl AttributeExt) -> Option<(Symbol, StabilityLevel)> {
+    let metas = attr.meta_item_list()?;
+
+    let mut feature = None;
+    let mut since = None;
+    for meta in metas {
+        let Some(mi) = meta.meta_item() else {
+            sess.dcx().emit_err(session_diagnostics::UnsupportedLiteral {
+                span: meta.span(),
+                reason: UnsupportedLiteralReason::Generic,
+                is_bytestr: false,
+                start_point_span: sess.source_map().start_point(meta.span()),
+            });
+            return None;
+        };
+
+        match mi.name_or_empty() {
+            sym::feature => insert_or_error(sess, mi, &mut feature)?,
+            sym::since => insert_or_error(sess, mi, &mut since)?,
+            _ => {
+                sess.dcx().emit_err(session_diagnostics::UnknownMetaItem {
+                    span: meta.span(),
+                    item: pprust::path_to_string(&mi.path),
+                    expected: &["feature", "since"],
+                });
+                return None;
+            }
+        }
+    }
+
+    let feature = match feature {
+        Some(feature) if rustc_lexer::is_ident(feature.as_str()) => Ok(feature),
+        Some(_bad_feature) => {
+            Err(sess.dcx().emit_err(session_diagnostics::NonIdentFeature { span: attr.span() }))
+        }
+        None => Err(sess.dcx().emit_err(session_diagnostics::MissingFeature { span: attr.span() })),
+    };
+
+    let since = if let Some(since) = since {
+        if since.as_str() == VERSION_PLACEHOLDER {
+            StableSince::Current
+        } else if let Some(version) = parse_version(since) {
+            StableSince::Version(version)
+        } else {
+            sess.dcx().emit_err(session_diagnostics::InvalidSince { span: attr.span() });
+            StableSince::Err
+        }
+    } else {
+        sess.dcx().emit_err(session_diagnostics::MissingSince { span: attr.span() });
+        StableSince::Err
+    };
+
+    match feature {
+        Ok(feature) => {
+            let level = StabilityLevel::Stable { since, allowed_through_unstable_modules: false };
+            Some((feature, level))
+        }
+        Err(ErrorGuaranteed { .. }) => None,
+    }
+}
+
+/// Read the content of a `unstable`/`rustc_const_unstable`/`rustc_default_body_unstable`
+/// attribute, and return the feature name and its stability information.
+fn parse_unstability(sess: &Session, attr: &impl AttributeExt) -> Option<(Symbol, StabilityLevel)> {
+    let metas = attr.meta_item_list()?;
+
+    let mut feature = None;
+    let mut reason = None;
+    let mut issue = None;
+    let mut issue_num = None;
+    let mut is_soft = false;
+    let mut implied_by = None;
+    for meta in metas {
+        let Some(mi) = meta.meta_item() else {
+            sess.dcx().emit_err(session_diagnostics::UnsupportedLiteral {
+                span: meta.span(),
+                reason: UnsupportedLiteralReason::Generic,
+                is_bytestr: false,
+                start_point_span: sess.source_map().start_point(meta.span()),
+            });
+            return None;
+        };
+
+        match mi.name_or_empty() {
+            sym::feature => insert_or_error(sess, mi, &mut feature)?,
+            sym::reason => insert_or_error(sess, mi, &mut reason)?,
+            sym::issue => {
+                insert_or_error(sess, mi, &mut issue)?;
+
+                // These unwraps are safe because `insert_or_error` ensures the meta item
+                // is a name/value pair string literal.
+                issue_num = match issue.unwrap().as_str() {
+                    "none" => None,
+                    issue => match issue.parse::<NonZero<u32>>() {
+                        Ok(num) => Some(num),
+                        Err(err) => {
+                            sess.dcx().emit_err(
+                                session_diagnostics::InvalidIssueString {
+                                    span: mi.span,
+                                    cause: session_diagnostics::InvalidIssueStringCause::from_int_error_kind(
+                                        mi.name_value_literal_span().unwrap(),
+                                        err.kind(),
+                                    ),
+                                },
+                            );
+                            return None;
+                        }
+                    },
+                };
+            }
+            sym::soft => {
+                if !mi.is_word() {
+                    sess.dcx().emit_err(session_diagnostics::SoftNoArgs { span: mi.span });
+                }
+                is_soft = true;
+            }
+            sym::implied_by => insert_or_error(sess, mi, &mut implied_by)?,
+            _ => {
+                sess.dcx().emit_err(session_diagnostics::UnknownMetaItem {
+                    span: meta.span(),
+                    item: pprust::path_to_string(&mi.path),
+                    expected: &["feature", "reason", "issue", "soft", "implied_by"],
+                });
+                return None;
+            }
+        }
+    }
+
+    let feature = match feature {
+        Some(feature) if rustc_lexer::is_ident(feature.as_str()) => Ok(feature),
+        Some(_bad_feature) => {
+            Err(sess.dcx().emit_err(session_diagnostics::NonIdentFeature { span: attr.span() }))
+        }
+        None => Err(sess.dcx().emit_err(session_diagnostics::MissingFeature { span: attr.span() })),
+    };
+
+    let issue = issue.ok_or_else(|| {
+        sess.dcx().emit_err(session_diagnostics::MissingIssue { span: attr.span() })
+    });
+
+    match (feature, issue) {
+        (Ok(feature), Ok(_)) => {
+            let level = StabilityLevel::Unstable {
+                reason: UnstableReason::from_opt_reason(reason),
+                issue: issue_num,
+                is_soft,
+                implied_by,
+            };
+            Some((feature, level))
+        }
+        (Err(ErrorGuaranteed { .. }), _) | (_, Err(ErrorGuaranteed { .. })) => None,
+    }
+}
diff --git a/compiler/rustc_attr/src/attributes/transparency.rs b/compiler/rustc_attr/src/attributes/transparency.rs
new file mode 100644
index 00000000000..4d37df58cb6
--- /dev/null
+++ b/compiler/rustc_attr/src/attributes/transparency.rs
@@ -0,0 +1,35 @@
+use rustc_ast::attr::AttributeExt;
+use crate::types::TransparencyError;
+use rustc_span::{hygiene::Transparency, sym};
+
+pub fn find_transparency(
+    attrs: &[impl AttributeExt],
+    macro_rules: bool,
+) -> (Transparency, Option<TransparencyError>) {
+    let mut transparency = None;
+    let mut error = None;
+    for attr in attrs {
+        if attr.has_name(sym::rustc_macro_transparency) {
+            if let Some((_, old_span)) = transparency {
+                error = Some(TransparencyError::MultipleTransparencyAttrs(old_span, attr.span()));
+                break;
+            } else if let Some(value) = attr.value_str() {
+                transparency = Some((
+                    match value {
+                        sym::transparent => Transparency::Transparent,
+                        sym::semitransparent => Transparency::SemiTransparent,
+                        sym::opaque => Transparency::Opaque,
+                        _ => {
+                            error =
+                                Some(TransparencyError::UnknownTransparency(value, attr.span()));
+                            continue;
+                        }
+                    },
+                    attr.span(),
+                ));
+            }
+        }
+    }
+    let fallback = if macro_rules { Transparency::SemiTransparent } else { Transparency::Opaque };
+    (transparency.map_or(fallback, |t| t.0), error)
+}
diff --git a/compiler/rustc_attr/src/attributes/util.rs b/compiler/rustc_attr/src/attributes/util.rs
new file mode 100644
index 00000000000..8539a1370d2
--- /dev/null
+++ b/compiler/rustc_attr/src/attributes/util.rs
@@ -0,0 +1,36 @@
+use rustc_ast::attr::{AttributeExt, first_attr_value_str_by_name};
+use rustc_feature::is_builtin_attr_name;
+use rustc_session::RustcVersion;
+use rustc_span::symbol::{Symbol, sym};
+
+pub(crate) enum UnsupportedLiteralReason {
+    Generic,
+    CfgString,
+    CfgBoolean,
+    DeprecatedString,
+    DeprecatedKvPair,
+}
+
+pub fn is_builtin_attr(attr: &impl AttributeExt) -> bool {
+    attr.is_doc_comment() || attr.ident().is_some_and(|ident| is_builtin_attr_name(ident.name))
+}
+
+pub fn find_crate_name(attrs: &[impl AttributeExt]) -> Option<Symbol> {
+    first_attr_value_str_by_name(attrs, sym::crate_name)
+}
+
+/// Parse a rustc version number written inside string literal in an attribute,
+/// like appears in `since = "1.0.0"`. Suffixes like "-dev" and "-nightly" are
+/// not accepted in this position, unlike when parsing CFG_RELEASE.
+pub fn parse_version(s: Symbol) -> Option<RustcVersion> {
+    let mut components = s.as_str().split('-');
+    let d = components.next()?;
+    if components.next().is_some() {
+        return None;
+    }
+    let mut digits = d.splitn(3, '.');
+    let major = digits.next()?.parse().ok()?;
+    let minor = digits.next()?.parse().ok()?;
+    let patch = digits.next().unwrap_or("0").parse().ok()?;
+    Some(RustcVersion { major, minor, patch })
+}
diff --git a/compiler/rustc_attr/src/builtin.rs b/compiler/rustc_attr/src/builtin.rs
deleted file mode 100644
index d5ee03d2b68..00000000000
--- a/compiler/rustc_attr/src/builtin.rs
+++ /dev/null
@@ -1,1349 +0,0 @@
-//! Parsing and validation of builtin attributes
-
-use std::num::NonZero;
-
-use rustc_abi::Align;
-use rustc_ast::attr::AttributeExt;
-use rustc_ast::{self as ast, LitKind, MetaItem, MetaItemInner, MetaItemKind, MetaItemLit, NodeId};
-use rustc_ast_pretty::pprust;
-use rustc_errors::ErrorGuaranteed;
-use rustc_feature::{Features, GatedCfg, find_gated_cfg, is_builtin_attr_name};
-use rustc_macros::{Decodable, Encodable, HashStable_Generic};
-use rustc_session::config::ExpectedValues;
-use rustc_session::lint::BuiltinLintDiag;
-use rustc_session::lint::builtin::UNEXPECTED_CFGS;
-use rustc_session::parse::feature_err;
-use rustc_session::{RustcVersion, Session};
-use rustc_span::Span;
-use rustc_span::hygiene::Transparency;
-use rustc_span::symbol::{Symbol, kw, sym};
-
-use crate::session_diagnostics::{self, IncorrectReprFormatGenericCause};
-use crate::{filter_by_name, first_attr_value_str_by_name, fluent_generated};
-
-/// The version placeholder that recently stabilized features contain inside the
-/// `since` field of the `#[stable]` attribute.
-///
-/// For more, see [this pull request](https://github.com/rust-lang/rust/pull/100591).
-pub const VERSION_PLACEHOLDER: &str = "CURRENT_RUSTC_VERSION";
-
-pub fn is_builtin_attr(attr: &impl AttributeExt) -> bool {
-    attr.is_doc_comment() || attr.ident().is_some_and(|ident| is_builtin_attr_name(ident.name))
-}
-
-pub(crate) enum UnsupportedLiteralReason {
-    Generic,
-    CfgString,
-    CfgBoolean,
-    DeprecatedString,
-    DeprecatedKvPair,
-}
-
-#[derive(Copy, Clone, PartialEq, Encodable, Decodable, Debug, HashStable_Generic)]
-pub enum InlineAttr {
-    None,
-    Hint,
-    Always,
-    Never,
-}
-
-#[derive(Clone, Encodable, Decodable, Debug, PartialEq, Eq, HashStable_Generic)]
-pub enum InstructionSetAttr {
-    ArmA32,
-    ArmT32,
-}
-
-#[derive(Clone, Encodable, Decodable, Debug, HashStable_Generic)]
-pub enum OptimizeAttr {
-    None,
-    Speed,
-    Size,
-}
-
-/// Represents the following attributes:
-///
-/// - `#[stable]`
-/// - `#[unstable]`
-#[derive(Encodable, Decodable, Copy, Clone, Debug, PartialEq, Eq, Hash)]
-#[derive(HashStable_Generic)]
-pub struct Stability {
-    pub level: StabilityLevel,
-    pub feature: Symbol,
-}
-
-impl Stability {
-    pub fn is_unstable(&self) -> bool {
-        self.level.is_unstable()
-    }
-
-    pub fn is_stable(&self) -> bool {
-        self.level.is_stable()
-    }
-
-    pub fn stable_since(&self) -> Option<StableSince> {
-        self.level.stable_since()
-    }
-}
-
-/// Represents the `#[rustc_const_unstable]` and `#[rustc_const_stable]` attributes.
-#[derive(Encodable, Decodable, Copy, Clone, Debug, PartialEq, Eq, Hash)]
-#[derive(HashStable_Generic)]
-pub struct ConstStability {
-    pub level: StabilityLevel,
-    pub feature: Symbol,
-    /// This is true iff the `const_stable_indirect` attribute is present.
-    pub const_stable_indirect: bool,
-    /// whether the function has a `#[rustc_promotable]` attribute
-    pub promotable: bool,
-}
-
-impl ConstStability {
-    pub fn is_const_unstable(&self) -> bool {
-        self.level.is_unstable()
-    }
-
-    pub fn is_const_stable(&self) -> bool {
-        self.level.is_stable()
-    }
-}
-
-/// Represents the `#[rustc_default_body_unstable]` attribute.
-#[derive(Encodable, Decodable, Copy, Clone, Debug, PartialEq, Eq, Hash)]
-#[derive(HashStable_Generic)]
-pub struct DefaultBodyStability {
-    pub level: StabilityLevel,
-    pub feature: Symbol,
-}
-
-/// The available stability levels.
-#[derive(Encodable, Decodable, PartialEq, Copy, Clone, Debug, Eq, Hash)]
-#[derive(HashStable_Generic)]
-pub enum StabilityLevel {
-    /// `#[unstable]`
-    Unstable {
-        /// Reason for the current stability level.
-        reason: UnstableReason,
-        /// Relevant `rust-lang/rust` issue.
-        issue: Option<NonZero<u32>>,
-        is_soft: bool,
-        /// If part of a feature is stabilized and a new feature is added for the remaining parts,
-        /// then the `implied_by` attribute is used to indicate which now-stable feature previously
-        /// contained an item.
-        ///
-        /// ```pseudo-Rust
-        /// #[unstable(feature = "foo", issue = "...")]
-        /// fn foo() {}
-        /// #[unstable(feature = "foo", issue = "...")]
-        /// fn foobar() {}
-        /// ```
-        ///
-        /// ...becomes...
-        ///
-        /// ```pseudo-Rust
-        /// #[stable(feature = "foo", since = "1.XX.X")]
-        /// fn foo() {}
-        /// #[unstable(feature = "foobar", issue = "...", implied_by = "foo")]
-        /// fn foobar() {}
-        /// ```
-        implied_by: Option<Symbol>,
-    },
-    /// `#[stable]`
-    Stable {
-        /// Rust release which stabilized this feature.
-        since: StableSince,
-        /// Is this item allowed to be referred to on stable, despite being contained in unstable
-        /// modules?
-        allowed_through_unstable_modules: bool,
-    },
-}
-
-/// Rust release in which a feature is stabilized.
-#[derive(Encodable, Decodable, PartialEq, Copy, Clone, Debug, Eq, PartialOrd, Ord, Hash)]
-#[derive(HashStable_Generic)]
-pub enum StableSince {
-    Version(RustcVersion),
-    /// Stabilized in the upcoming version, whatever number that is.
-    Current,
-    /// Failed to parse a stabilization version.
-    Err,
-}
-
-impl StabilityLevel {
-    pub fn is_unstable(&self) -> bool {
-        matches!(self, StabilityLevel::Unstable { .. })
-    }
-    pub fn is_stable(&self) -> bool {
-        matches!(self, StabilityLevel::Stable { .. })
-    }
-    pub fn stable_since(&self) -> Option<StableSince> {
-        match *self {
-            StabilityLevel::Stable { since, .. } => Some(since),
-            StabilityLevel::Unstable { .. } => None,
-        }
-    }
-}
-
-#[derive(Encodable, Decodable, PartialEq, Copy, Clone, Debug, Eq, Hash)]
-#[derive(HashStable_Generic)]
-pub enum UnstableReason {
-    None,
-    Default,
-    Some(Symbol),
-}
-
-impl UnstableReason {
-    fn from_opt_reason(reason: Option<Symbol>) -> Self {
-        // UnstableReason::Default constructed manually
-        match reason {
-            Some(r) => Self::Some(r),
-            None => Self::None,
-        }
-    }
-
-    pub fn to_opt_reason(&self) -> Option<Symbol> {
-        match self {
-            Self::None => None,
-            Self::Default => Some(sym::unstable_location_reason_default),
-            Self::Some(r) => Some(*r),
-        }
-    }
-}
-
-/// Collects stability info from `stable`/`unstable`/`rustc_allowed_through_unstable_modules`
-/// attributes in `attrs`. Returns `None` if no stability attributes are found.
-pub fn find_stability(
-    sess: &Session,
-    attrs: &[impl AttributeExt],
-    item_sp: Span,
-) -> Option<(Stability, Span)> {
-    let mut stab: Option<(Stability, Span)> = None;
-    let mut allowed_through_unstable_modules = false;
-
-    for attr in attrs {
-        match attr.name_or_empty() {
-            sym::rustc_allowed_through_unstable_modules => allowed_through_unstable_modules = true,
-            sym::unstable => {
-                if stab.is_some() {
-                    sess.dcx().emit_err(session_diagnostics::MultipleStabilityLevels {
-                        span: attr.span(),
-                    });
-                    break;
-                }
-
-                if let Some((feature, level)) = parse_unstability(sess, attr) {
-                    stab = Some((Stability { level, feature }, attr.span()));
-                }
-            }
-            sym::stable => {
-                if stab.is_some() {
-                    sess.dcx().emit_err(session_diagnostics::MultipleStabilityLevels {
-                        span: attr.span(),
-                    });
-                    break;
-                }
-                if let Some((feature, level)) = parse_stability(sess, attr) {
-                    stab = Some((Stability { level, feature }, attr.span()));
-                }
-            }
-            _ => {}
-        }
-    }
-
-    if allowed_through_unstable_modules {
-        match &mut stab {
-            Some((
-                Stability {
-                    level: StabilityLevel::Stable { allowed_through_unstable_modules, .. },
-                    ..
-                },
-                _,
-            )) => *allowed_through_unstable_modules = true,
-            _ => {
-                sess.dcx()
-                    .emit_err(session_diagnostics::RustcAllowedUnstablePairing { span: item_sp });
-            }
-        }
-    }
-
-    stab
-}
-
-/// Collects stability info from `rustc_const_stable`/`rustc_const_unstable`/`rustc_promotable`
-/// attributes in `attrs`. Returns `None` if no stability attributes are found.
-pub fn find_const_stability(
-    sess: &Session,
-    attrs: &[impl AttributeExt],
-    item_sp: Span,
-) -> Option<(ConstStability, Span)> {
-    let mut const_stab: Option<(ConstStability, Span)> = None;
-    let mut promotable = false;
-    let mut const_stable_indirect = false;
-
-    for attr in attrs {
-        match attr.name_or_empty() {
-            sym::rustc_promotable => promotable = true,
-            sym::rustc_const_stable_indirect => const_stable_indirect = true,
-            sym::rustc_const_unstable => {
-                if const_stab.is_some() {
-                    sess.dcx().emit_err(session_diagnostics::MultipleStabilityLevels {
-                        span: attr.span(),
-                    });
-                    break;
-                }
-
-                if let Some((feature, level)) = parse_unstability(sess, attr) {
-                    const_stab = Some((
-                        ConstStability {
-                            level,
-                            feature,
-                            const_stable_indirect: false,
-                            promotable: false,
-                        },
-                        attr.span(),
-                    ));
-                }
-            }
-            sym::rustc_const_stable => {
-                if const_stab.is_some() {
-                    sess.dcx().emit_err(session_diagnostics::MultipleStabilityLevels {
-                        span: attr.span(),
-                    });
-                    break;
-                }
-                if let Some((feature, level)) = parse_stability(sess, attr) {
-                    const_stab = Some((
-                        ConstStability {
-                            level,
-                            feature,
-                            const_stable_indirect: false,
-                            promotable: false,
-                        },
-                        attr.span(),
-                    ));
-                }
-            }
-            _ => {}
-        }
-    }
-
-    // Merge promotable and const_stable_indirect into stability info
-    if promotable {
-        match &mut const_stab {
-            Some((stab, _)) => stab.promotable = promotable,
-            _ => {
-                _ = sess
-                    .dcx()
-                    .emit_err(session_diagnostics::RustcPromotablePairing { span: item_sp })
-            }
-        }
-    }
-    if const_stable_indirect {
-        match &mut const_stab {
-            Some((stab, _)) => {
-                if stab.is_const_unstable() {
-                    stab.const_stable_indirect = true;
-                } else {
-                    _ = sess.dcx().emit_err(session_diagnostics::RustcConstStableIndirectPairing {
-                        span: item_sp,
-                    })
-                }
-            }
-            _ => {
-                // This function has no const stability attribute, but has `const_stable_indirect`.
-                // We ignore that; unmarked functions are subject to recursive const stability
-                // checks by default so we do carry out the user's intent.
-            }
-        }
-    }
-
-    const_stab
-}
-
-/// Calculates the const stability for a const function in a `-Zforce-unstable-if-unmarked` crate
-/// without the `staged_api` feature.
-pub fn unmarked_crate_const_stab(
-    _sess: &Session,
-    attrs: &[impl AttributeExt],
-    regular_stab: Stability,
-) -> ConstStability {
-    assert!(regular_stab.level.is_unstable());
-    // The only attribute that matters here is `rustc_const_stable_indirect`.
-    // We enforce recursive const stability rules for those functions.
-    let const_stable_indirect =
-        attrs.iter().any(|a| a.name_or_empty() == sym::rustc_const_stable_indirect);
-    ConstStability {
-        feature: regular_stab.feature,
-        const_stable_indirect,
-        promotable: false,
-        level: regular_stab.level,
-    }
-}
-
-/// Collects stability info from `rustc_default_body_unstable` attributes in `attrs`.
-/// Returns `None` if no stability attributes are found.
-pub fn find_body_stability(
-    sess: &Session,
-    attrs: &[impl AttributeExt],
-) -> Option<(DefaultBodyStability, Span)> {
-    let mut body_stab: Option<(DefaultBodyStability, Span)> = None;
-
-    for attr in attrs {
-        if attr.has_name(sym::rustc_default_body_unstable) {
-            if body_stab.is_some() {
-                sess.dcx()
-                    .emit_err(session_diagnostics::MultipleStabilityLevels { span: attr.span() });
-                break;
-            }
-
-            if let Some((feature, level)) = parse_unstability(sess, attr) {
-                body_stab = Some((DefaultBodyStability { level, feature }, attr.span()));
-            }
-        }
-    }
-
-    body_stab
-}
-
-fn insert_or_error(sess: &Session, meta: &MetaItem, item: &mut Option<Symbol>) -> Option<()> {
-    if item.is_some() {
-        sess.dcx().emit_err(session_diagnostics::MultipleItem {
-            span: meta.span,
-            item: pprust::path_to_string(&meta.path),
-        });
-        None
-    } else if let Some(v) = meta.value_str() {
-        *item = Some(v);
-        Some(())
-    } else {
-        sess.dcx().emit_err(session_diagnostics::IncorrectMetaItem { span: meta.span });
-        None
-    }
-}
-
-/// Read the content of a `stable`/`rustc_const_stable` attribute, and return the feature name and
-/// its stability information.
-fn parse_stability(sess: &Session, attr: &impl AttributeExt) -> Option<(Symbol, StabilityLevel)> {
-    let metas = attr.meta_item_list()?;
-
-    let mut feature = None;
-    let mut since = None;
-    for meta in metas {
-        let Some(mi) = meta.meta_item() else {
-            sess.dcx().emit_err(session_diagnostics::UnsupportedLiteral {
-                span: meta.span(),
-                reason: UnsupportedLiteralReason::Generic,
-                is_bytestr: false,
-                start_point_span: sess.source_map().start_point(meta.span()),
-            });
-            return None;
-        };
-
-        match mi.name_or_empty() {
-            sym::feature => insert_or_error(sess, mi, &mut feature)?,
-            sym::since => insert_or_error(sess, mi, &mut since)?,
-            _ => {
-                sess.dcx().emit_err(session_diagnostics::UnknownMetaItem {
-                    span: meta.span(),
-                    item: pprust::path_to_string(&mi.path),
-                    expected: &["feature", "since"],
-                });
-                return None;
-            }
-        }
-    }
-
-    let feature = match feature {
-        Some(feature) if rustc_lexer::is_ident(feature.as_str()) => Ok(feature),
-        Some(_bad_feature) => {
-            Err(sess.dcx().emit_err(session_diagnostics::NonIdentFeature { span: attr.span() }))
-        }
-        None => Err(sess.dcx().emit_err(session_diagnostics::MissingFeature { span: attr.span() })),
-    };
-
-    let since = if let Some(since) = since {
-        if since.as_str() == VERSION_PLACEHOLDER {
-            StableSince::Current
-        } else if let Some(version) = parse_version(since) {
-            StableSince::Version(version)
-        } else {
-            sess.dcx().emit_err(session_diagnostics::InvalidSince { span: attr.span() });
-            StableSince::Err
-        }
-    } else {
-        sess.dcx().emit_err(session_diagnostics::MissingSince { span: attr.span() });
-        StableSince::Err
-    };
-
-    match feature {
-        Ok(feature) => {
-            let level = StabilityLevel::Stable { since, allowed_through_unstable_modules: false };
-            Some((feature, level))
-        }
-        Err(ErrorGuaranteed { .. }) => None,
-    }
-}
-
-/// Read the content of a `unstable`/`rustc_const_unstable`/`rustc_default_body_unstable`
-/// attribute, and return the feature name and its stability information.
-fn parse_unstability(sess: &Session, attr: &impl AttributeExt) -> Option<(Symbol, StabilityLevel)> {
-    let metas = attr.meta_item_list()?;
-
-    let mut feature = None;
-    let mut reason = None;
-    let mut issue = None;
-    let mut issue_num = None;
-    let mut is_soft = false;
-    let mut implied_by = None;
-    for meta in metas {
-        let Some(mi) = meta.meta_item() else {
-            sess.dcx().emit_err(session_diagnostics::UnsupportedLiteral {
-                span: meta.span(),
-                reason: UnsupportedLiteralReason::Generic,
-                is_bytestr: false,
-                start_point_span: sess.source_map().start_point(meta.span()),
-            });
-            return None;
-        };
-
-        match mi.name_or_empty() {
-            sym::feature => insert_or_error(sess, mi, &mut feature)?,
-            sym::reason => insert_or_error(sess, mi, &mut reason)?,
-            sym::issue => {
-                insert_or_error(sess, mi, &mut issue)?;
-
-                // These unwraps are safe because `insert_or_error` ensures the meta item
-                // is a name/value pair string literal.
-                issue_num = match issue.unwrap().as_str() {
-                    "none" => None,
-                    issue => match issue.parse::<NonZero<u32>>() {
-                        Ok(num) => Some(num),
-                        Err(err) => {
-                            sess.dcx().emit_err(
-                                session_diagnostics::InvalidIssueString {
-                                    span: mi.span,
-                                    cause: session_diagnostics::InvalidIssueStringCause::from_int_error_kind(
-                                        mi.name_value_literal_span().unwrap(),
-                                        err.kind(),
-                                    ),
-                                },
-                            );
-                            return None;
-                        }
-                    },
-                };
-            }
-            sym::soft => {
-                if !mi.is_word() {
-                    sess.dcx().emit_err(session_diagnostics::SoftNoArgs { span: mi.span });
-                }
-                is_soft = true;
-            }
-            sym::implied_by => insert_or_error(sess, mi, &mut implied_by)?,
-            _ => {
-                sess.dcx().emit_err(session_diagnostics::UnknownMetaItem {
-                    span: meta.span(),
-                    item: pprust::path_to_string(&mi.path),
-                    expected: &["feature", "reason", "issue", "soft", "implied_by"],
-                });
-                return None;
-            }
-        }
-    }
-
-    let feature = match feature {
-        Some(feature) if rustc_lexer::is_ident(feature.as_str()) => Ok(feature),
-        Some(_bad_feature) => {
-            Err(sess.dcx().emit_err(session_diagnostics::NonIdentFeature { span: attr.span() }))
-        }
-        None => Err(sess.dcx().emit_err(session_diagnostics::MissingFeature { span: attr.span() })),
-    };
-
-    let issue = issue.ok_or_else(|| {
-        sess.dcx().emit_err(session_diagnostics::MissingIssue { span: attr.span() })
-    });
-
-    match (feature, issue) {
-        (Ok(feature), Ok(_)) => {
-            let level = StabilityLevel::Unstable {
-                reason: UnstableReason::from_opt_reason(reason),
-                issue: issue_num,
-                is_soft,
-                implied_by,
-            };
-            Some((feature, level))
-        }
-        (Err(ErrorGuaranteed { .. }), _) | (_, Err(ErrorGuaranteed { .. })) => None,
-    }
-}
-
-pub fn find_crate_name(attrs: &[impl AttributeExt]) -> Option<Symbol> {
-    first_attr_value_str_by_name(attrs, sym::crate_name)
-}
-
-#[derive(Clone, Debug)]
-pub struct Condition {
-    pub name: Symbol,
-    pub name_span: Span,
-    pub value: Option<Symbol>,
-    pub value_span: Option<Span>,
-    pub span: Span,
-}
-
-/// Tests if a cfg-pattern matches the cfg set
-pub fn cfg_matches(
-    cfg: &ast::MetaItemInner,
-    sess: &Session,
-    lint_node_id: NodeId,
-    features: Option<&Features>,
-) -> bool {
-    eval_condition(cfg, sess, features, &mut |cfg| {
-        try_gate_cfg(cfg.name, cfg.span, sess, features);
-        match sess.psess.check_config.expecteds.get(&cfg.name) {
-            Some(ExpectedValues::Some(values)) if !values.contains(&cfg.value) => {
-                sess.psess.buffer_lint(
-                    UNEXPECTED_CFGS,
-                    cfg.span,
-                    lint_node_id,
-                    BuiltinLintDiag::UnexpectedCfgValue(
-                        (cfg.name, cfg.name_span),
-                        cfg.value.map(|v| (v, cfg.value_span.unwrap())),
-                    ),
-                );
-            }
-            None if sess.psess.check_config.exhaustive_names => {
-                sess.psess.buffer_lint(
-                    UNEXPECTED_CFGS,
-                    cfg.span,
-                    lint_node_id,
-                    BuiltinLintDiag::UnexpectedCfgName(
-                        (cfg.name, cfg.name_span),
-                        cfg.value.map(|v| (v, cfg.value_span.unwrap())),
-                    ),
-                );
-            }
-            _ => { /* not unexpected */ }
-        }
-        sess.psess.config.contains(&(cfg.name, cfg.value))
-    })
-}
-
-fn try_gate_cfg(name: Symbol, span: Span, sess: &Session, features: Option<&Features>) {
-    let gate = find_gated_cfg(|sym| sym == name);
-    if let (Some(feats), Some(gated_cfg)) = (features, gate) {
-        gate_cfg(gated_cfg, span, sess, feats);
-    }
-}
-
-#[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
-fn gate_cfg(gated_cfg: &GatedCfg, cfg_span: Span, sess: &Session, features: &Features) {
-    let (cfg, feature, has_feature) = gated_cfg;
-    if !has_feature(features) && !cfg_span.allows_unstable(*feature) {
-        let explain = format!("`cfg({cfg})` is experimental and subject to change");
-        feature_err(sess, *feature, cfg_span, explain).emit();
-    }
-}
-
-/// Parse a rustc version number written inside string literal in an attribute,
-/// like appears in `since = "1.0.0"`. Suffixes like "-dev" and "-nightly" are
-/// not accepted in this position, unlike when parsing CFG_RELEASE.
-pub fn parse_version(s: Symbol) -> Option<RustcVersion> {
-    let mut components = s.as_str().split('-');
-    let d = components.next()?;
-    if components.next().is_some() {
-        return None;
-    }
-    let mut digits = d.splitn(3, '.');
-    let major = digits.next()?.parse().ok()?;
-    let minor = digits.next()?.parse().ok()?;
-    let patch = digits.next().unwrap_or("0").parse().ok()?;
-    Some(RustcVersion { major, minor, patch })
-}
-
-/// Evaluate a cfg-like condition (with `any` and `all`), using `eval` to
-/// evaluate individual items.
-pub fn eval_condition(
-    cfg: &ast::MetaItemInner,
-    sess: &Session,
-    features: Option<&Features>,
-    eval: &mut impl FnMut(Condition) -> bool,
-) -> bool {
-    let dcx = sess.dcx();
-
-    let cfg = match cfg {
-        ast::MetaItemInner::MetaItem(meta_item) => meta_item,
-        ast::MetaItemInner::Lit(MetaItemLit { kind: LitKind::Bool(b), .. }) => {
-            if let Some(features) = features {
-                // we can't use `try_gate_cfg` as symbols don't differentiate between `r#true`
-                // and `true`, and we want to keep the former working without feature gate
-                gate_cfg(
-                    &(
-                        if *b { kw::True } else { kw::False },
-                        sym::cfg_boolean_literals,
-                        |features: &Features| features.cfg_boolean_literals(),
-                    ),
-                    cfg.span(),
-                    sess,
-                    features,
-                );
-            }
-            return *b;
-        }
-        _ => {
-            dcx.emit_err(session_diagnostics::UnsupportedLiteral {
-                span: cfg.span(),
-                reason: UnsupportedLiteralReason::CfgBoolean,
-                is_bytestr: false,
-                start_point_span: sess.source_map().start_point(cfg.span()),
-            });
-            return false;
-        }
-    };
-
-    match &cfg.kind {
-        ast::MetaItemKind::List(mis) if cfg.name_or_empty() == sym::version => {
-            try_gate_cfg(sym::version, cfg.span, sess, features);
-            let (min_version, span) = match &mis[..] {
-                [MetaItemInner::Lit(MetaItemLit { kind: LitKind::Str(sym, ..), span, .. })] => {
-                    (sym, span)
-                }
-                [
-                    MetaItemInner::Lit(MetaItemLit { span, .. })
-                    | MetaItemInner::MetaItem(MetaItem { span, .. }),
-                ] => {
-                    dcx.emit_err(session_diagnostics::ExpectedVersionLiteral { span: *span });
-                    return false;
-                }
-                [..] => {
-                    dcx.emit_err(session_diagnostics::ExpectedSingleVersionLiteral {
-                        span: cfg.span,
-                    });
-                    return false;
-                }
-            };
-            let Some(min_version) = parse_version(*min_version) else {
-                dcx.emit_warn(session_diagnostics::UnknownVersionLiteral { span: *span });
-                return false;
-            };
-
-            // See https://github.com/rust-lang/rust/issues/64796#issuecomment-640851454 for details
-            if sess.psess.assume_incomplete_release {
-                RustcVersion::CURRENT > min_version
-            } else {
-                RustcVersion::CURRENT >= min_version
-            }
-        }
-        ast::MetaItemKind::List(mis) => {
-            for mi in mis.iter() {
-                if mi.meta_item_or_bool().is_none() {
-                    dcx.emit_err(session_diagnostics::UnsupportedLiteral {
-                        span: mi.span(),
-                        reason: UnsupportedLiteralReason::Generic,
-                        is_bytestr: false,
-                        start_point_span: sess.source_map().start_point(mi.span()),
-                    });
-                    return false;
-                }
-            }
-
-            // The unwraps below may look dangerous, but we've already asserted
-            // that they won't fail with the loop above.
-            match cfg.name_or_empty() {
-                sym::any => mis
-                    .iter()
-                    // We don't use any() here, because we want to evaluate all cfg condition
-                    // as eval_condition can (and does) extra checks
-                    .fold(false, |res, mi| res | eval_condition(mi, sess, features, eval)),
-                sym::all => mis
-                    .iter()
-                    // We don't use all() here, because we want to evaluate all cfg condition
-                    // as eval_condition can (and does) extra checks
-                    .fold(true, |res, mi| res & eval_condition(mi, sess, features, eval)),
-                sym::not => {
-                    let [mi] = mis.as_slice() else {
-                        dcx.emit_err(session_diagnostics::ExpectedOneCfgPattern { span: cfg.span });
-                        return false;
-                    };
-
-                    !eval_condition(mi, sess, features, eval)
-                }
-                sym::target => {
-                    if let Some(features) = features
-                        && !features.cfg_target_compact()
-                    {
-                        feature_err(
-                            sess,
-                            sym::cfg_target_compact,
-                            cfg.span,
-                            fluent_generated::attr_unstable_cfg_target_compact,
-                        )
-                        .emit();
-                    }
-
-                    mis.iter().fold(true, |res, mi| {
-                        let Some(mut mi) = mi.meta_item().cloned() else {
-                            dcx.emit_err(session_diagnostics::CfgPredicateIdentifier {
-                                span: mi.span(),
-                            });
-                            return false;
-                        };
-
-                        if let [seg, ..] = &mut mi.path.segments[..] {
-                            seg.ident.name = Symbol::intern(&format!("target_{}", seg.ident.name));
-                        }
-
-                        res & eval_condition(
-                            &ast::MetaItemInner::MetaItem(mi),
-                            sess,
-                            features,
-                            eval,
-                        )
-                    })
-                }
-                _ => {
-                    dcx.emit_err(session_diagnostics::InvalidPredicate {
-                        span: cfg.span,
-                        predicate: pprust::path_to_string(&cfg.path),
-                    });
-                    false
-                }
-            }
-        }
-        ast::MetaItemKind::Word | MetaItemKind::NameValue(..) if cfg.path.segments.len() != 1 => {
-            dcx.emit_err(session_diagnostics::CfgPredicateIdentifier { span: cfg.path.span });
-            true
-        }
-        MetaItemKind::NameValue(lit) if !lit.kind.is_str() => {
-            dcx.emit_err(session_diagnostics::UnsupportedLiteral {
-                span: lit.span,
-                reason: UnsupportedLiteralReason::CfgString,
-                is_bytestr: lit.kind.is_bytestr(),
-                start_point_span: sess.source_map().start_point(lit.span),
-            });
-            true
-        }
-        ast::MetaItemKind::Word | ast::MetaItemKind::NameValue(..) => {
-            let ident = cfg.ident().expect("multi-segment cfg predicate");
-            eval(Condition {
-                name: ident.name,
-                name_span: ident.span,
-                value: cfg.value_str(),
-                value_span: cfg.name_value_literal_span(),
-                span: cfg.span,
-            })
-        }
-    }
-}
-
-#[derive(Copy, Debug, Encodable, Decodable, Clone, HashStable_Generic)]
-pub struct Deprecation {
-    pub since: DeprecatedSince,
-    /// The note to issue a reason.
-    pub note: Option<Symbol>,
-    /// A text snippet used to completely replace any use of the deprecated item in an expression.
-    ///
-    /// This is currently unstable.
-    pub suggestion: Option<Symbol>,
-}
-
-/// Release in which an API is deprecated.
-#[derive(Copy, Debug, Encodable, Decodable, Clone, HashStable_Generic)]
-pub enum DeprecatedSince {
-    RustcVersion(RustcVersion),
-    /// Deprecated in the future ("to be determined").
-    Future,
-    /// `feature(staged_api)` is off. Deprecation versions outside the standard
-    /// library are allowed to be arbitrary strings, for better or worse.
-    NonStandard(Symbol),
-    /// Deprecation version is unspecified but optional.
-    Unspecified,
-    /// Failed to parse a deprecation version, or the deprecation version is
-    /// unspecified and required. An error has already been emitted.
-    Err,
-}
-
-impl Deprecation {
-    /// Whether an item marked with #[deprecated(since = "X")] is currently
-    /// deprecated (i.e., whether X is not greater than the current rustc
-    /// version).
-    pub fn is_in_effect(&self) -> bool {
-        match self.since {
-            DeprecatedSince::RustcVersion(since) => since <= RustcVersion::CURRENT,
-            DeprecatedSince::Future => false,
-            // The `since` field doesn't have semantic purpose without `#![staged_api]`.
-            DeprecatedSince::NonStandard(_) => true,
-            // Assume deprecation is in effect if "since" field is absent or invalid.
-            DeprecatedSince::Unspecified | DeprecatedSince::Err => true,
-        }
-    }
-
-    pub fn is_since_rustc_version(&self) -> bool {
-        matches!(self.since, DeprecatedSince::RustcVersion(_))
-    }
-}
-
-/// Finds the deprecation attribute. `None` if none exists.
-pub fn find_deprecation(
-    sess: &Session,
-    features: &Features,
-    attrs: &[impl AttributeExt],
-) -> Option<(Deprecation, Span)> {
-    let mut depr: Option<(Deprecation, Span)> = None;
-    let is_rustc = features.staged_api();
-
-    'outer: for attr in attrs {
-        if !attr.has_name(sym::deprecated) {
-            continue;
-        }
-
-        let mut since = None;
-        let mut note = None;
-        let mut suggestion = None;
-
-        if attr.is_doc_comment() {
-            continue;
-        } else if attr.is_word() {
-        } else if let Some(value) = attr.value_str() {
-            note = Some(value)
-        } else if let Some(list) = attr.meta_item_list() {
-            let get = |meta: &MetaItem, item: &mut Option<Symbol>| {
-                if item.is_some() {
-                    sess.dcx().emit_err(session_diagnostics::MultipleItem {
-                        span: meta.span,
-                        item: pprust::path_to_string(&meta.path),
-                    });
-                    return false;
-                }
-                if let Some(v) = meta.value_str() {
-                    *item = Some(v);
-                    true
-                } else {
-                    if let Some(lit) = meta.name_value_literal() {
-                        sess.dcx().emit_err(session_diagnostics::UnsupportedLiteral {
-                            span: lit.span,
-                            reason: UnsupportedLiteralReason::DeprecatedString,
-                            is_bytestr: lit.kind.is_bytestr(),
-                            start_point_span: sess.source_map().start_point(lit.span),
-                        });
-                    } else {
-                        sess.dcx()
-                            .emit_err(session_diagnostics::IncorrectMetaItem { span: meta.span });
-                    }
-                    false
-                }
-            };
-
-            for meta in &list {
-                match meta {
-                    MetaItemInner::MetaItem(mi) => match mi.name_or_empty() {
-                        sym::since => {
-                            if !get(mi, &mut since) {
-                                continue 'outer;
-                            }
-                        }
-                        sym::note => {
-                            if !get(mi, &mut note) {
-                                continue 'outer;
-                            }
-                        }
-                        sym::suggestion => {
-                            if !features.deprecated_suggestion() {
-                                sess.dcx().emit_err(
-                                    session_diagnostics::DeprecatedItemSuggestion {
-                                        span: mi.span,
-                                        is_nightly: sess.is_nightly_build(),
-                                        details: (),
-                                    },
-                                );
-                            }
-
-                            if !get(mi, &mut suggestion) {
-                                continue 'outer;
-                            }
-                        }
-                        _ => {
-                            sess.dcx().emit_err(session_diagnostics::UnknownMetaItem {
-                                span: meta.span(),
-                                item: pprust::path_to_string(&mi.path),
-                                expected: if features.deprecated_suggestion() {
-                                    &["since", "note", "suggestion"]
-                                } else {
-                                    &["since", "note"]
-                                },
-                            });
-                            continue 'outer;
-                        }
-                    },
-                    MetaItemInner::Lit(lit) => {
-                        sess.dcx().emit_err(session_diagnostics::UnsupportedLiteral {
-                            span: lit.span,
-                            reason: UnsupportedLiteralReason::DeprecatedKvPair,
-                            is_bytestr: false,
-                            start_point_span: sess.source_map().start_point(lit.span),
-                        });
-                        continue 'outer;
-                    }
-                }
-            }
-        } else {
-            continue;
-        }
-
-        let since = if let Some(since) = since {
-            if since.as_str() == "TBD" {
-                DeprecatedSince::Future
-            } else if !is_rustc {
-                DeprecatedSince::NonStandard(since)
-            } else if let Some(version) = parse_version(since) {
-                DeprecatedSince::RustcVersion(version)
-            } else {
-                sess.dcx().emit_err(session_diagnostics::InvalidSince { span: attr.span() });
-                DeprecatedSince::Err
-            }
-        } else if is_rustc {
-            sess.dcx().emit_err(session_diagnostics::MissingSince { span: attr.span() });
-            DeprecatedSince::Err
-        } else {
-            DeprecatedSince::Unspecified
-        };
-
-        if is_rustc && note.is_none() {
-            sess.dcx().emit_err(session_diagnostics::MissingNote { span: attr.span() });
-            continue;
-        }
-
-        depr = Some((Deprecation { since, note, suggestion }, attr.span()));
-    }
-
-    depr
-}
-
-#[derive(PartialEq, Debug, Encodable, Decodable, Copy, Clone)]
-pub enum ReprAttr {
-    ReprInt(IntType),
-    ReprRust,
-    ReprC,
-    ReprPacked(Align),
-    ReprSimd,
-    ReprTransparent,
-    ReprAlign(Align),
-}
-
-#[derive(Eq, PartialEq, Debug, Copy, Clone)]
-#[derive(Encodable, Decodable, HashStable_Generic)]
-pub enum IntType {
-    SignedInt(ast::IntTy),
-    UnsignedInt(ast::UintTy),
-}
-
-impl IntType {
-    #[inline]
-    pub fn is_signed(self) -> bool {
-        use IntType::*;
-
-        match self {
-            SignedInt(..) => true,
-            UnsignedInt(..) => false,
-        }
-    }
-}
-
-/// Parse #[repr(...)] forms.
-///
-/// Valid repr contents: any of the primitive integral type names (see
-/// `int_type_of_word`, below) to specify enum discriminant type; `C`, to use
-/// the same discriminant size that the corresponding C enum would or C
-/// structure layout, `packed` to remove padding, and `transparent` to delegate representation
-/// concerns to the only non-ZST field.
-pub fn find_repr_attrs(sess: &Session, attr: &impl AttributeExt) -> Vec<ReprAttr> {
-    if attr.has_name(sym::repr) { parse_repr_attr(sess, attr) } else { Vec::new() }
-}
-
-pub fn parse_repr_attr(sess: &Session, attr: &impl AttributeExt) -> Vec<ReprAttr> {
-    assert!(attr.has_name(sym::repr), "expected `#[repr(..)]`, found: {attr:?}");
-    use ReprAttr::*;
-    let mut acc = Vec::new();
-    let dcx = sess.dcx();
-
-    if let Some(items) = attr.meta_item_list() {
-        for item in items {
-            let mut recognised = false;
-            if item.is_word() {
-                let hint = match item.name_or_empty() {
-                    sym::Rust => Some(ReprRust),
-                    sym::C => Some(ReprC),
-                    sym::packed => Some(ReprPacked(Align::ONE)),
-                    sym::simd => Some(ReprSimd),
-                    sym::transparent => Some(ReprTransparent),
-                    sym::align => {
-                        sess.dcx().emit_err(session_diagnostics::InvalidReprAlignNeedArg {
-                            span: item.span(),
-                        });
-                        recognised = true;
-                        None
-                    }
-                    name => int_type_of_word(name).map(ReprInt),
-                };
-
-                if let Some(h) = hint {
-                    recognised = true;
-                    acc.push(h);
-                }
-            } else if let Some((name, value)) = item.singleton_lit_list() {
-                let mut literal_error = None;
-                let mut err_span = item.span();
-                if name == sym::align {
-                    recognised = true;
-                    match parse_alignment(&value.kind) {
-                        Ok(literal) => acc.push(ReprAlign(literal)),
-                        Err(message) => {
-                            err_span = value.span;
-                            literal_error = Some(message)
-                        }
-                    };
-                } else if name == sym::packed {
-                    recognised = true;
-                    match parse_alignment(&value.kind) {
-                        Ok(literal) => acc.push(ReprPacked(literal)),
-                        Err(message) => {
-                            err_span = value.span;
-                            literal_error = Some(message)
-                        }
-                    };
-                } else if matches!(name, sym::Rust | sym::C | sym::simd | sym::transparent)
-                    || int_type_of_word(name).is_some()
-                {
-                    recognised = true;
-                    sess.dcx().emit_err(session_diagnostics::InvalidReprHintNoParen {
-                        span: item.span(),
-                        name: name.to_ident_string(),
-                    });
-                }
-                if let Some(literal_error) = literal_error {
-                    sess.dcx().emit_err(session_diagnostics::InvalidReprGeneric {
-                        span: err_span,
-                        repr_arg: name.to_ident_string(),
-                        error_part: literal_error,
-                    });
-                }
-            } else if let Some(meta_item) = item.meta_item() {
-                match &meta_item.kind {
-                    MetaItemKind::NameValue(value) => {
-                        if meta_item.has_name(sym::align) || meta_item.has_name(sym::packed) {
-                            let name = meta_item.name_or_empty().to_ident_string();
-                            recognised = true;
-                            sess.dcx().emit_err(session_diagnostics::IncorrectReprFormatGeneric {
-                                span: item.span(),
-                                repr_arg: &name,
-                                cause: IncorrectReprFormatGenericCause::from_lit_kind(
-                                    item.span(),
-                                    &value.kind,
-                                    &name,
-                                ),
-                            });
-                        } else if matches!(
-                            meta_item.name_or_empty(),
-                            sym::Rust | sym::C | sym::simd | sym::transparent
-                        ) || int_type_of_word(meta_item.name_or_empty()).is_some()
-                        {
-                            recognised = true;
-                            sess.dcx().emit_err(session_diagnostics::InvalidReprHintNoValue {
-                                span: meta_item.span,
-                                name: meta_item.name_or_empty().to_ident_string(),
-                            });
-                        }
-                    }
-                    MetaItemKind::List(nested_items) => {
-                        if meta_item.has_name(sym::align) {
-                            recognised = true;
-                            if let [nested_item] = nested_items.as_slice() {
-                                sess.dcx().emit_err(
-                                    session_diagnostics::IncorrectReprFormatExpectInteger {
-                                        span: nested_item.span(),
-                                    },
-                                );
-                            } else {
-                                sess.dcx().emit_err(
-                                    session_diagnostics::IncorrectReprFormatAlignOneArg {
-                                        span: meta_item.span,
-                                    },
-                                );
-                            }
-                        } else if meta_item.has_name(sym::packed) {
-                            recognised = true;
-                            if let [nested_item] = nested_items.as_slice() {
-                                sess.dcx().emit_err(
-                                    session_diagnostics::IncorrectReprFormatPackedExpectInteger {
-                                        span: nested_item.span(),
-                                    },
-                                );
-                            } else {
-                                sess.dcx().emit_err(
-                                    session_diagnostics::IncorrectReprFormatPackedOneOrZeroArg {
-                                        span: meta_item.span,
-                                    },
-                                );
-                            }
-                        } else if matches!(
-                            meta_item.name_or_empty(),
-                            sym::Rust | sym::C | sym::simd | sym::transparent
-                        ) || int_type_of_word(meta_item.name_or_empty()).is_some()
-                        {
-                            recognised = true;
-                            sess.dcx().emit_err(session_diagnostics::InvalidReprHintNoParen {
-                                span: meta_item.span,
-                                name: meta_item.name_or_empty().to_ident_string(),
-                            });
-                        }
-                    }
-                    _ => (),
-                }
-            }
-            if !recognised {
-                // Not a word we recognize. This will be caught and reported by
-                // the `check_mod_attrs` pass, but this pass doesn't always run
-                // (e.g. if we only pretty-print the source), so we have to gate
-                // the `span_delayed_bug` call as follows:
-                if sess.opts.pretty.map_or(true, |pp| pp.needs_analysis()) {
-                    dcx.span_delayed_bug(item.span(), "unrecognized representation hint");
-                }
-            }
-        }
-    }
-    acc
-}
-
-fn int_type_of_word(s: Symbol) -> Option<IntType> {
-    use IntType::*;
-
-    match s {
-        sym::i8 => Some(SignedInt(ast::IntTy::I8)),
-        sym::u8 => Some(UnsignedInt(ast::UintTy::U8)),
-        sym::i16 => Some(SignedInt(ast::IntTy::I16)),
-        sym::u16 => Some(UnsignedInt(ast::UintTy::U16)),
-        sym::i32 => Some(SignedInt(ast::IntTy::I32)),
-        sym::u32 => Some(UnsignedInt(ast::UintTy::U32)),
-        sym::i64 => Some(SignedInt(ast::IntTy::I64)),
-        sym::u64 => Some(UnsignedInt(ast::UintTy::U64)),
-        sym::i128 => Some(SignedInt(ast::IntTy::I128)),
-        sym::u128 => Some(UnsignedInt(ast::UintTy::U128)),
-        sym::isize => Some(SignedInt(ast::IntTy::Isize)),
-        sym::usize => Some(UnsignedInt(ast::UintTy::Usize)),
-        _ => None,
-    }
-}
-
-pub enum TransparencyError {
-    UnknownTransparency(Symbol, Span),
-    MultipleTransparencyAttrs(Span, Span),
-}
-
-pub fn find_transparency(
-    attrs: &[impl AttributeExt],
-    macro_rules: bool,
-) -> (Transparency, Option<TransparencyError>) {
-    let mut transparency = None;
-    let mut error = None;
-    for attr in attrs {
-        if attr.has_name(sym::rustc_macro_transparency) {
-            if let Some((_, old_span)) = transparency {
-                error = Some(TransparencyError::MultipleTransparencyAttrs(old_span, attr.span()));
-                break;
-            } else if let Some(value) = attr.value_str() {
-                transparency = Some((
-                    match value {
-                        sym::transparent => Transparency::Transparent,
-                        sym::semitransparent => Transparency::SemiTransparent,
-                        sym::opaque => Transparency::Opaque,
-                        _ => {
-                            error =
-                                Some(TransparencyError::UnknownTransparency(value, attr.span()));
-                            continue;
-                        }
-                    },
-                    attr.span(),
-                ));
-            }
-        }
-    }
-    let fallback = if macro_rules { Transparency::SemiTransparent } else { Transparency::Opaque };
-    (transparency.map_or(fallback, |t| t.0), error)
-}
-
-pub fn allow_internal_unstable<'a>(
-    sess: &'a Session,
-    attrs: &'a [impl AttributeExt],
-) -> impl Iterator<Item = Symbol> + 'a {
-    allow_unstable(sess, attrs, sym::allow_internal_unstable)
-}
-
-pub fn rustc_allow_const_fn_unstable<'a>(
-    sess: &'a Session,
-    attrs: &'a [impl AttributeExt],
-) -> impl Iterator<Item = Symbol> + 'a {
-    allow_unstable(sess, attrs, sym::rustc_allow_const_fn_unstable)
-}
-
-fn allow_unstable<'a>(
-    sess: &'a Session,
-    attrs: &'a [impl AttributeExt],
-    symbol: Symbol,
-) -> impl Iterator<Item = Symbol> + 'a {
-    let attrs = filter_by_name(attrs, symbol);
-    let list = attrs
-        .filter_map(move |attr| {
-            attr.meta_item_list().or_else(|| {
-                sess.dcx().emit_err(session_diagnostics::ExpectsFeatureList {
-                    span: attr.span(),
-                    name: symbol.to_ident_string(),
-                });
-                None
-            })
-        })
-        .flatten();
-
-    list.into_iter().filter_map(move |it| {
-        let name = it.ident().map(|ident| ident.name);
-        if name.is_none() {
-            sess.dcx().emit_err(session_diagnostics::ExpectsFeatures {
-                span: it.span(),
-                name: symbol.to_ident_string(),
-            });
-        }
-        name
-    })
-}
-
-pub fn parse_alignment(node: &ast::LitKind) -> Result<Align, &'static str> {
-    if let ast::LitKind::Int(literal, ast::LitIntType::Unsuffixed) = node {
-        // `Align::from_bytes` accepts 0 as an input, check is_power_of_two() first
-        if literal.get().is_power_of_two() {
-            // Only possible error is larger than 2^29
-            literal
-                .get()
-                .try_into()
-                .ok()
-                .and_then(|v| Align::from_bytes(v).ok())
-                .ok_or("larger than 2^29")
-        } else {
-            Err("not a power of two")
-        }
-    } else {
-        Err("not an unsuffixed integer")
-    }
-}
-
-/// Read the content of a `rustc_confusables` attribute, and return the list of candidate names.
-pub fn parse_confusables(attr: &impl AttributeExt) -> Option<Vec<Symbol>> {
-    let metas = attr.meta_item_list()?;
-
-    let mut candidates = Vec::new();
-
-    for meta in metas {
-        let MetaItemInner::Lit(meta_lit) = meta else {
-            return None;
-        };
-        candidates.push(meta_lit.symbol);
-    }
-
-    Some(candidates)
-}
diff --git a/compiler/rustc_attr/src/lib.rs b/compiler/rustc_attr/src/lib.rs
index bb207c5c952..d34ff02c7ed 100644
--- a/compiler/rustc_attr/src/lib.rs
+++ b/compiler/rustc_attr/src/lib.rs
@@ -1,8 +1,24 @@
-//! Functions and types dealing with attributes and meta items.
+//! Centralized logic for parsing and validating all attributes used after HIR.
 //!
-//! FIXME(Centril): For now being, much of the logic is still in `rustc_ast::attr`.
-//! The goal is to move the definition of `MetaItem` and things that don't need to be in `syntax`
-//! to this crate.
+//! History: Check out [#131229](https://github.com/rust-lang/rust/issues/131229).
+//! There used to be only one definition of attributes in the compiler: `ast::Attribute`.
+//! These were then parsed or validated or both in places distributed all over the compiler.
+//!
+//! Attributes are markers on items. Most are actually attribute-like proc-macros, and are expanded
+//! but some remain as the built-in attributes to guide compilation.
+//!
+//! In this crate, syntactical attributes (sequences of tokens that look like
+//! `#[something(something else)]`) are parsed into more semantic attributes, markers on items.
+//! Multiple syntactic attributes might influence a single semantic attribute. For example,
+//! `#[stable(...)]` and `#[unstable()]` cannot occur together, and both semantically define
+//! a "stability". Stability defines an [`AttributeExtractor`](attributes::AttributeExtractor)
+//! that recognizes both `#[stable()]` and `#[unstable()]` syntactic attributes, and at the end
+//! produce a single [`ParsedAttributeKind::Stability`].
+//!
+//! FIXME(jdonszelmann): update devguide for best practices on attributes
+//! FIXME(jdonszelmann): rename to `rustc_attr` in the future, integrating it into this crate.
+//!
+//! To define a new builtin, first add it
 
 // tidy-alphabetical-start
 #![allow(internal_features)]
@@ -12,14 +28,13 @@
 #![warn(unreachable_pub)]
 // tidy-alphabetical-end
 
-mod builtin;
+mod attributes;
 mod session_diagnostics;
+mod types;
 
-pub use IntType::*;
-pub use ReprAttr::*;
-pub use StabilityLevel::*;
-pub use builtin::*;
-pub use rustc_ast::attr::*;
+pub use attributes::*;
 pub(crate) use rustc_session::HashStableContext;
+pub use types::*;
+pub use util::{find_crate_name, is_builtin_attr, parse_version};
 
 rustc_fluent_macro::fluent_messages! { "../messages.ftl" }
diff --git a/compiler/rustc_attr/src/session_diagnostics.rs b/compiler/rustc_attr/src/session_diagnostics.rs
index 9d08a9f5754..245221e9729 100644
--- a/compiler/rustc_attr/src/session_diagnostics.rs
+++ b/compiler/rustc_attr/src/session_diagnostics.rs
@@ -6,7 +6,8 @@ use rustc_errors::{Applicability, Diag, DiagCtxtHandle, Diagnostic, EmissionGuar
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_span::{Span, Symbol};
 
-use crate::{UnsupportedLiteralReason, fluent_generated as fluent};
+use crate::attributes::util::UnsupportedLiteralReason;
+use crate::fluent_generated as fluent;
 
 #[derive(Diagnostic)]
 #[diag(attr_expected_one_cfg_pattern, code = E0536)]
diff --git a/compiler/rustc_attr/src/types.rs b/compiler/rustc_attr/src/types.rs
new file mode 100644
index 00000000000..243a70c0a21
--- /dev/null
+++ b/compiler/rustc_attr/src/types.rs
@@ -0,0 +1,262 @@
+use std::num::NonZero;
+
+use rustc_abi::Align;
+use rustc_ast as ast;
+use rustc_macros::{Encodable, Decodable, HashStable_Generic};
+use rustc_session::RustcVersion;
+use rustc_span::{sym, Span, Symbol};
+
+/// The version placeholder that recently stabilized features contain inside the
+/// `since` field of the `#[stable]` attribute.
+///
+/// For more, see [this pull request](https://github.com/rust-lang/rust/pull/100591).
+pub const VERSION_PLACEHOLDER: &str = "CURRENT_RUSTC_VERSION";
+
+#[derive(Copy, Clone, PartialEq, Encodable, Decodable, Debug, HashStable_Generic)]
+pub enum InlineAttr {
+    None,
+    Hint,
+    Always,
+    Never,
+}
+
+#[derive(Clone, Encodable, Decodable, Debug, PartialEq, Eq, HashStable_Generic)]
+pub enum InstructionSetAttr {
+    ArmA32,
+    ArmT32,
+}
+
+#[derive(Clone, Encodable, Decodable, Debug, HashStable_Generic)]
+pub enum OptimizeAttr {
+    None,
+    Speed,
+    Size,
+}
+
+#[derive(Clone, Debug, Encodable, Decodable)]
+pub enum DiagnosticAttribute {
+    // tidy-alphabetical-start
+    DoNotRecommend,
+    OnUnimplemented,
+    // tidy-alphabetical-end
+}
+
+#[derive(PartialEq, Debug, Encodable, Decodable, Copy, Clone)]
+pub enum ReprAttr {
+    ReprInt(IntType),
+    ReprRust,
+    ReprC,
+    ReprPacked(Align),
+    ReprSimd,
+    ReprTransparent,
+    ReprAlign(Align),
+}
+pub use ReprAttr::*;
+
+pub enum TransparencyError {
+    UnknownTransparency(Symbol, Span),
+    MultipleTransparencyAttrs(Span, Span),
+}
+
+#[derive(Eq, PartialEq, Debug, Copy, Clone)]
+#[derive(Encodable, Decodable)]
+pub enum IntType {
+    SignedInt(ast::IntTy),
+    UnsignedInt(ast::UintTy),
+}
+
+/// Represents the following attributes:
+///
+/// - `#[stable]`
+/// - `#[unstable]`
+#[derive(Encodable, Decodable, Copy, Clone, Debug, PartialEq, Eq, Hash)]
+#[derive(HashStable_Generic)]
+pub struct Stability {
+    pub level: StabilityLevel,
+    pub feature: Symbol,
+}
+
+impl Stability {
+    pub fn is_unstable(&self) -> bool {
+        self.level.is_unstable()
+    }
+
+    pub fn is_stable(&self) -> bool {
+        self.level.is_stable()
+    }
+
+    pub fn stable_since(&self) -> Option<StableSince> {
+        self.level.stable_since()
+    }
+}
+
+/// Represents the `#[rustc_const_unstable]` and `#[rustc_const_stable]` attributes.
+#[derive(Encodable, Decodable, Copy, Clone, Debug, PartialEq, Eq, Hash)]
+#[derive(HashStable_Generic)]
+pub struct ConstStability {
+    pub level: StabilityLevel,
+    pub feature: Symbol,
+    /// This is true iff the `const_stable_indirect` attribute is present.
+    pub const_stable_indirect: bool,
+    /// whether the function has a `#[rustc_promotable]` attribute
+    pub promotable: bool,
+}
+
+impl ConstStability {
+    pub fn is_const_unstable(&self) -> bool {
+        self.level.is_unstable()
+    }
+
+    pub fn is_const_stable(&self) -> bool {
+        self.level.is_stable()
+    }
+}
+
+/// Represents the `#[rustc_default_body_unstable]` attribute.
+#[derive(Encodable, Decodable, Copy, Clone, Debug, PartialEq, Eq, Hash)]
+#[derive(HashStable_Generic)]
+pub struct DefaultBodyStability {
+    pub level: StabilityLevel,
+    pub feature: Symbol,
+}
+
+/// The available stability levels.
+#[derive(Encodable, Decodable, PartialEq, Copy, Clone, Debug, Eq, Hash)]
+#[derive(HashStable_Generic)]
+pub enum StabilityLevel {
+    /// `#[unstable]`
+    Unstable {
+        /// Reason for the current stability level.
+        reason: UnstableReason,
+        /// Relevant `rust-lang/rust` issue.
+        issue: Option<NonZero<u32>>,
+        is_soft: bool,
+        /// If part of a feature is stabilized and a new feature is added for the remaining parts,
+        /// then the `implied_by` attribute is used to indicate which now-stable feature previously
+        /// contained an item.
+        ///
+        /// ```pseudo-Rust
+        /// #[unstable(feature = "foo", issue = "...")]
+        /// fn foo() {}
+        /// #[unstable(feature = "foo", issue = "...")]
+        /// fn foobar() {}
+        /// ```
+        ///
+        /// ...becomes...
+        ///
+        /// ```pseudo-Rust
+        /// #[stable(feature = "foo", since = "1.XX.X")]
+        /// fn foo() {}
+        /// #[unstable(feature = "foobar", issue = "...", implied_by = "foo")]
+        /// fn foobar() {}
+        /// ```
+        implied_by: Option<Symbol>,
+    },
+    /// `#[stable]`
+    Stable {
+        /// Rust release which stabilized this feature.
+        since: StableSince,
+        /// Is this item allowed to be referred to on stable, despite being contained in unstable
+        /// modules?
+        allowed_through_unstable_modules: bool,
+    },
+}
+
+/// Rust release in which a feature is stabilized.
+#[derive(Encodable, Decodable, PartialEq, Copy, Clone, Debug, Eq, PartialOrd, Ord, Hash)]
+#[derive(HashStable_Generic)]
+pub enum StableSince {
+    Version(RustcVersion),
+    /// Stabilized in the upcoming version, whatever number that is.
+    Current,
+    /// Failed to parse a stabilization version.
+    Err,
+}
+
+impl StabilityLevel {
+    pub fn is_unstable(&self) -> bool {
+        matches!(self, StabilityLevel::Unstable { .. })
+    }
+    pub fn is_stable(&self) -> bool {
+        matches!(self, StabilityLevel::Stable { .. })
+    }
+    pub fn stable_since(&self) -> Option<StableSince> {
+        match *self {
+            StabilityLevel::Stable { since, .. } => Some(since),
+            StabilityLevel::Unstable { .. } => None,
+        }
+    }
+}
+
+#[derive(Encodable, Decodable, PartialEq, Copy, Clone, Debug, Eq, Hash)]
+#[derive(HashStable_Generic)]
+pub enum UnstableReason {
+    None,
+    Default,
+    Some(Symbol),
+}
+
+impl UnstableReason {
+    pub(crate) fn from_opt_reason(reason: Option<Symbol>) -> Self {
+        // UnstableReason::Default constructed manually
+        match reason {
+            Some(r) => Self::Some(r),
+            None => Self::None,
+        }
+    }
+
+    pub fn to_opt_reason(&self) -> Option<Symbol> {
+        match self {
+            Self::None => None,
+            Self::Default => Some(sym::unstable_location_reason_default),
+            Self::Some(r) => Some(*r),
+        }
+    }
+}
+
+#[derive(Copy, Debug, Encodable, Decodable, Clone, HashStable_Generic)]
+pub struct Deprecation {
+    pub since: DeprecatedSince,
+    /// The note to issue a reason.
+    pub note: Option<Symbol>,
+    /// A text snippet used to completely replace any use of the deprecated item in an expression.
+    ///
+    /// This is currently unstable.
+    pub suggestion: Option<Symbol>,
+}
+
+/// Release in which an API is deprecated.
+#[derive(Copy, Debug, Encodable, Decodable, Clone, HashStable_Generic)]
+pub enum DeprecatedSince {
+    RustcVersion(RustcVersion),
+    /// Deprecated in the future ("to be determined").
+    Future,
+    /// `feature(staged_api)` is off. Deprecation versions outside the standard
+    /// library are allowed to be arbitrary strings, for better or worse.
+    NonStandard(Symbol),
+    /// Deprecation version is unspecified but optional.
+    Unspecified,
+    /// Failed to parse a deprecation version, or the deprecation version is
+    /// unspecified and required. An error has already been emitted.
+    Err,
+}
+
+impl Deprecation {
+    /// Whether an item marked with #[deprecated(since = "X")] is currently
+    /// deprecated (i.e., whether X is not greater than the current rustc
+    /// version).
+    pub fn is_in_effect(&self) -> bool {
+        match self.since {
+            DeprecatedSince::RustcVersion(since) => since <= RustcVersion::CURRENT,
+            DeprecatedSince::Future => false,
+            // The `since` field doesn't have semantic purpose without `#![staged_api]`.
+            DeprecatedSince::NonStandard(_) => true,
+            // Assume deprecation is in effect if "since" field is absent or invalid.
+            DeprecatedSince::Unspecified | DeprecatedSince::Err => true,
+        }
+    }
+
+    pub fn is_since_rustc_version(&self) -> bool {
+        matches!(self.since, DeprecatedSince::RustcVersion(_))
+    }
+}
diff --git a/compiler/rustc_codegen_ssa/src/base.rs b/compiler/rustc_codegen_ssa/src/base.rs
index 27c9cb0b31e..828f82ddde3 100644
--- a/compiler/rustc_codegen_ssa/src/base.rs
+++ b/compiler/rustc_codegen_ssa/src/base.rs
@@ -5,7 +5,6 @@ use std::time::{Duration, Instant};
 use itertools::Itertools;
 use rustc_abi::FIRST_VARIANT;
 use rustc_ast::expand::allocator::{ALLOCATOR_METHODS, AllocatorKind, global_fn_name};
-use rustc_attr as attr;
 use rustc_data_structures::fx::{FxHashMap, FxIndexSet};
 use rustc_data_structures::profiling::{get_resident_set_size, print_time_passes_entry};
 use rustc_data_structures::sync::{Lrc, par_map};
@@ -31,6 +30,7 @@ use rustc_trait_selection::infer::at::ToTrace;
 use rustc_trait_selection::infer::{BoundRegionConversionTime, TyCtxtInferExt};
 use rustc_trait_selection::traits::{ObligationCause, ObligationCtxt};
 use tracing::{debug, info};
+use {rustc_ast as ast, rustc_attr as attr};
 
 use crate::assert_module_sources::CguReuse;
 use crate::back::link::are_upstream_rust_objects_already_included;
@@ -873,7 +873,8 @@ impl CrateInfo {
             crate_types.iter().map(|&c| (c, crate::back::linker::linked_symbols(tcx, c))).collect();
         let local_crate_name = tcx.crate_name(LOCAL_CRATE);
         let crate_attrs = tcx.hir().attrs(rustc_hir::CRATE_HIR_ID);
-        let subsystem = attr::first_attr_value_str_by_name(crate_attrs, sym::windows_subsystem);
+        let subsystem =
+            ast::attr::first_attr_value_str_by_name(crate_attrs, sym::windows_subsystem);
         let windows_subsystem = subsystem.map(|subsystem| {
             if subsystem != sym::windows && subsystem != sym::console {
                 tcx.dcx().emit_fatal(errors::InvalidWindowsSubsystem { subsystem });
diff --git a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
index 5edd18bd3f4..c88b625060e 100644
--- a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
+++ b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
@@ -1,5 +1,6 @@
+use rustc_ast::attr::list_contains_name;
 use rustc_ast::{MetaItemInner, attr};
-use rustc_attr::{InlineAttr, InstructionSetAttr, OptimizeAttr, list_contains_name};
+use rustc_attr::{InlineAttr, InstructionSetAttr, OptimizeAttr};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::codes::*;
 use rustc_errors::{DiagMessage, SubdiagMessage, struct_span_code_err};
diff --git a/compiler/rustc_expand/src/base.rs b/compiler/rustc_expand/src/base.rs
index 8e42afb60d8..9f2765718b5 100644
--- a/compiler/rustc_expand/src/base.rs
+++ b/compiler/rustc_expand/src/base.rs
@@ -809,7 +809,7 @@ impl SyntaxExtension {
     /// | yes           | yes | yes           | yes      | yes |
     fn get_collapse_debuginfo(sess: &Session, attrs: &[impl AttributeExt], ext: bool) -> bool {
         let flag = sess.opts.cg.collapse_macro_debuginfo;
-        let attr = attr::find_by_name(attrs, sym::collapse_debuginfo)
+        let attr = ast::attr::find_by_name(attrs, sym::collapse_debuginfo)
             .and_then(|attr| {
                 Self::collapse_debuginfo_by_name(attr)
                     .map_err(|span| {
@@ -818,7 +818,7 @@ impl SyntaxExtension {
                     .ok()
             })
             .unwrap_or_else(|| {
-                if attr::contains_name(attrs, sym::rustc_builtin_macro) {
+                if ast::attr::contains_name(attrs, sym::rustc_builtin_macro) {
                     CollapseMacroDebuginfo::Yes
                 } else {
                     CollapseMacroDebuginfo::Unspecified
@@ -850,14 +850,14 @@ impl SyntaxExtension {
         let allow_internal_unstable =
             rustc_attr::allow_internal_unstable(sess, attrs).collect::<Vec<Symbol>>();
 
-        let allow_internal_unsafe = attr::contains_name(attrs, sym::allow_internal_unsafe);
-        let local_inner_macros = attr::find_by_name(attrs, sym::macro_export)
+        let allow_internal_unsafe = ast::attr::contains_name(attrs, sym::allow_internal_unsafe);
+        let local_inner_macros = ast::attr::find_by_name(attrs, sym::macro_export)
             .and_then(|macro_export| macro_export.meta_item_list())
-            .is_some_and(|l| attr::list_contains_name(&l, sym::local_inner_macros));
+            .is_some_and(|l| ast::attr::list_contains_name(&l, sym::local_inner_macros));
         let collapse_debuginfo = Self::get_collapse_debuginfo(sess, attrs, !is_local);
         tracing::debug!(?name, ?local_inner_macros, ?collapse_debuginfo, ?allow_internal_unsafe);
 
-        let (builtin_name, helper_attrs) = attr::find_by_name(attrs, sym::rustc_builtin_macro)
+        let (builtin_name, helper_attrs) = ast::attr::find_by_name(attrs, sym::rustc_builtin_macro)
             .map(|attr| {
                 // Override `helper_attrs` passed above if it's a built-in macro,
                 // marking `proc_macro_derive` macros as built-in is not a realistic use case.
diff --git a/compiler/rustc_expand/src/config.rs b/compiler/rustc_expand/src/config.rs
index dc6aa110f45..12298d43b89 100644
--- a/compiler/rustc_expand/src/config.rs
+++ b/compiler/rustc_expand/src/config.rs
@@ -362,7 +362,7 @@ impl<'a> StripUnconfigured<'a> {
         ));
 
         let tokens = Some(LazyAttrTokenStream::new(AttrTokenStream::new(trees)));
-        let attr = attr::mk_attr_from_item(
+        let attr = ast::attr::mk_attr_from_item(
             &self.sess.psess.attr_id_generator,
             item,
             tokens,
diff --git a/compiler/rustc_expand/src/mbe/macro_rules.rs b/compiler/rustc_expand/src/mbe/macro_rules.rs
index f7e3403cd28..c666078fa3b 100644
--- a/compiler/rustc_expand/src/mbe/macro_rules.rs
+++ b/compiler/rustc_expand/src/mbe/macro_rules.rs
@@ -3,13 +3,14 @@ use std::collections::hash_map::Entry;
 use std::{mem, slice};
 
 use ast::token::IdentIsRaw;
+use rustc_ast::attr::AttributeExt;
 use rustc_ast::token::NtPatKind::*;
 use rustc_ast::token::TokenKind::*;
 use rustc_ast::token::{self, Delimiter, NonterminalKind, Token, TokenKind};
 use rustc_ast::tokenstream::{DelimSpan, TokenStream};
 use rustc_ast::{self as ast, DUMMY_NODE_ID, NodeId};
 use rustc_ast_pretty::pprust;
-use rustc_attr::{self as attr, AttributeExt, TransparencyError};
+use rustc_attr::{self as attr, TransparencyError};
 use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
 use rustc_errors::{Applicability, ErrorGuaranteed};
 use rustc_feature::Features;
diff --git a/compiler/rustc_lint/src/levels.rs b/compiler/rustc_lint/src/levels.rs
index 7ea6c63dbe6..04099cd9001 100644
--- a/compiler/rustc_lint/src/levels.rs
+++ b/compiler/rustc_lint/src/levels.rs
@@ -1,5 +1,5 @@
+use rustc_ast::attr::AttributeExt;
 use rustc_ast_pretty::pprust;
-use rustc_attr::AttributeExt;
 use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_errors::{Diag, LintDiagnostic, MultiSpan};
 use rustc_feature::{Features, GateIssue};
diff --git a/compiler/rustc_lint/src/nonstandard_style.rs b/compiler/rustc_lint/src/nonstandard_style.rs
index ff464b76c0d..7d1c8139518 100644
--- a/compiler/rustc_lint/src/nonstandard_style.rs
+++ b/compiler/rustc_lint/src/nonstandard_style.rs
@@ -342,8 +342,8 @@ impl<'tcx> LateLintPass<'tcx> for NonSnakeCase {
         let crate_ident = if let Some(name) = &cx.tcx.sess.opts.crate_name {
             Some(Ident::from_str(name))
         } else {
-            attr::find_by_name(cx.tcx.hir().attrs(hir::CRATE_HIR_ID), sym::crate_name).and_then(
-                |attr| {
+            ast::attr::find_by_name(cx.tcx.hir().attrs(hir::CRATE_HIR_ID), sym::crate_name)
+                .and_then(|attr| {
                     if let AttrKind::Normal(n) = &attr.kind
                         && let AttrItem { args: AttrArgs::Eq { eq_span: _, expr: ref lit }, .. } =
                             n.as_ref()
@@ -371,8 +371,7 @@ impl<'tcx> LateLintPass<'tcx> for NonSnakeCase {
                     } else {
                         None
                     }
-                },
-            )
+                })
         };
 
         if let Some(ident) = &crate_ident {
@@ -503,7 +502,7 @@ impl<'tcx> LateLintPass<'tcx> for NonUpperCaseGlobals {
     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
         let attrs = cx.tcx.hir().attrs(it.hir_id());
         match it.kind {
-            hir::ItemKind::Static(..) if !attr::contains_name(attrs, sym::no_mangle) => {
+            hir::ItemKind::Static(..) if !ast::attr::contains_name(attrs, sym::no_mangle) => {
                 NonUpperCaseGlobals::check_upper_case(cx, "static variable", &it.ident);
             }
             hir::ItemKind::Const(..) => {
diff --git a/compiler/rustc_metadata/src/rmeta/encoder.rs b/compiler/rustc_metadata/src/rmeta/encoder.rs
index 92c0e8c3a50..88906d71597 100644
--- a/compiler/rustc_metadata/src/rmeta/encoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/encoder.rs
@@ -710,15 +710,18 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
                 has_global_allocator: tcx.has_global_allocator(LOCAL_CRATE),
                 has_alloc_error_handler: tcx.has_alloc_error_handler(LOCAL_CRATE),
                 has_panic_handler: tcx.has_panic_handler(LOCAL_CRATE),
-                has_default_lib_allocator: attr::contains_name(attrs, sym::default_lib_allocator),
+                has_default_lib_allocator: ast::attr::contains_name(
+                    attrs,
+                    sym::default_lib_allocator,
+                ),
                 proc_macro_data,
                 debugger_visualizers,
-                compiler_builtins: attr::contains_name(attrs, sym::compiler_builtins),
-                needs_allocator: attr::contains_name(attrs, sym::needs_allocator),
-                needs_panic_runtime: attr::contains_name(attrs, sym::needs_panic_runtime),
-                no_builtins: attr::contains_name(attrs, sym::no_builtins),
-                panic_runtime: attr::contains_name(attrs, sym::panic_runtime),
-                profiler_runtime: attr::contains_name(attrs, sym::profiler_runtime),
+                compiler_builtins: ast::attr::contains_name(attrs, sym::compiler_builtins),
+                needs_allocator: ast::attr::contains_name(attrs, sym::needs_allocator),
+                needs_panic_runtime: ast::attr::contains_name(attrs, sym::needs_panic_runtime),
+                no_builtins: ast::attr::contains_name(attrs, sym::no_builtins),
+                panic_runtime: ast::attr::contains_name(attrs, sym::panic_runtime),
+                profiler_runtime: ast::attr::contains_name(attrs, sym::profiler_runtime),
                 symbol_mangling_version: tcx.sess.opts.get_symbol_mangling_version(),
 
                 crate_deps,
@@ -1917,11 +1920,11 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
                 // Proc-macros may have attributes like `#[allow_internal_unstable]`,
                 // so downstream crates need access to them.
                 let attrs = hir.attrs(proc_macro);
-                let macro_kind = if attr::contains_name(attrs, sym::proc_macro) {
+                let macro_kind = if ast::attr::contains_name(attrs, sym::proc_macro) {
                     MacroKind::Bang
-                } else if attr::contains_name(attrs, sym::proc_macro_attribute) {
+                } else if ast::attr::contains_name(attrs, sym::proc_macro_attribute) {
                     MacroKind::Attr
-                } else if let Some(attr) = attr::find_by_name(attrs, sym::proc_macro_derive) {
+                } else if let Some(attr) = ast::attr::find_by_name(attrs, sym::proc_macro_derive) {
                     // This unwrap chain should have been checked by the proc-macro harness.
                     name = attr.meta_item_list().unwrap()[0]
                         .meta_item()
diff --git a/compiler/rustc_middle/src/middle/stability.rs b/compiler/rustc_middle/src/middle/stability.rs
index 94d13021612..eda53ce2e9f 100644
--- a/compiler/rustc_middle/src/middle/stability.rs
+++ b/compiler/rustc_middle/src/middle/stability.rs
@@ -392,7 +392,7 @@ impl<'tcx> TyCtxt<'tcx> {
 
         match stability {
             Some(Stability {
-                level: attr::Unstable { reason, issue, is_soft, implied_by },
+                level: attr::StabilityLevel::Unstable { reason, issue, is_soft, implied_by },
                 feature,
                 ..
             }) => {
@@ -475,7 +475,7 @@ impl<'tcx> TyCtxt<'tcx> {
 
         match stability {
             Some(DefaultBodyStability {
-                level: attr::Unstable { reason, issue, is_soft, .. },
+                level: attr::StabilityLevel::Unstable { reason, issue, is_soft, .. },
                 feature,
             }) => {
                 if span.allows_unstable(feature) {
diff --git a/compiler/rustc_passes/src/stability.rs b/compiler/rustc_passes/src/stability.rs
index 2809ad453ff..72705b43d6f 100644
--- a/compiler/rustc_passes/src/stability.rs
+++ b/compiler/rustc_passes/src/stability.rs
@@ -6,7 +6,7 @@ use std::num::NonZero;
 
 use rustc_attr::{
     self as attr, ConstStability, DeprecatedSince, Stability, StabilityLevel, StableSince,
-    Unstable, UnstableReason, VERSION_PLACEHOLDER,
+    UnstableReason, VERSION_PLACEHOLDER,
 };
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_data_structures::unord::{ExtendUnord, UnordMap, UnordSet};
@@ -199,7 +199,7 @@ impl<'a, 'tcx> Annotator<'a, 'tcx> {
             // this is *almost surely* an accident.
             if let (
                 &Some(DeprecatedSince::RustcVersion(dep_since)),
-                &attr::Stable { since: stab_since, .. },
+                &attr::StabilityLevel::Stable { since: stab_since, .. },
             ) = (&depr.as_ref().map(|(d, _)| d.since), &stab.level)
             {
                 match stab_since {
@@ -224,15 +224,17 @@ impl<'a, 'tcx> Annotator<'a, 'tcx> {
 
             // Stable *language* features shouldn't be used as unstable library features.
             // (Not doing this for stable library features is checked by tidy.)
-            if let Stability { level: Unstable { .. }, feature } = stab {
+            if let Stability { level: StabilityLevel::Unstable { .. }, feature } = stab {
                 if ACCEPTED_LANG_FEATURES.iter().find(|f| f.name == feature).is_some() {
                     self.tcx
                         .dcx()
                         .emit_err(errors::UnstableAttrForAlreadyStableFeature { span, item_sp });
                 }
             }
-            if let Stability { level: Unstable { implied_by: Some(implied_by), .. }, feature } =
-                stab
+            if let Stability {
+                level: StabilityLevel::Unstable { implied_by: Some(implied_by), .. },
+                feature,
+            } = stab
             {
                 self.index.implications.insert(implied_by, feature);
             }
@@ -278,8 +280,10 @@ impl<'a, 'tcx> Annotator<'a, 'tcx> {
 
         // Stable *language* features shouldn't be used as unstable library features.
         // (Not doing this for stable library features is checked by tidy.)
-        if let Some((ConstStability { level: Unstable { .. }, feature, .. }, const_span)) =
-            const_stab
+        if let Some((
+            ConstStability { level: StabilityLevel::Unstable { .. }, feature, .. },
+            const_span,
+        )) = const_stab
         {
             if ACCEPTED_LANG_FEATURES.iter().find(|f| f.name == feature).is_some() {
                 self.tcx.dcx().emit_err(errors::UnstableAttrForAlreadyStableFeature {
@@ -314,7 +318,7 @@ impl<'a, 'tcx> Annotator<'a, 'tcx> {
         });
 
         if let Some(ConstStability {
-            level: Unstable { implied_by: Some(implied_by), .. },
+            level: StabilityLevel::Unstable { implied_by: Some(implied_by), .. },
             feature,
             ..
         }) = const_stab
@@ -780,7 +784,11 @@ impl<'tcx> Visitor<'tcx> for Checker<'tcx> {
                     // error if all involved types and traits are stable, because
                     // it will have no effect.
                     // See: https://github.com/rust-lang/rust/issues/55436
-                    if let Some((Stability { level: attr::Unstable { .. }, .. }, span)) = stab {
+                    if let Some((
+                        Stability { level: attr::StabilityLevel::Unstable { .. }, .. },
+                        span,
+                    )) = stab
+                    {
                         let mut c = CheckTraitImplStable { tcx: self.tcx, fully_stable: true };
                         c.visit_ty(self_ty);
                         c.visit_trait_ref(t);
diff --git a/compiler/rustc_resolve/src/build_reduced_graph.rs b/compiler/rustc_resolve/src/build_reduced_graph.rs
index 924b8afa329..e18c7edec30 100644
--- a/compiler/rustc_resolve/src/build_reduced_graph.rs
+++ b/compiler/rustc_resolve/src/build_reduced_graph.rs
@@ -634,7 +634,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
             }
             ast::UseTreeKind::Glob => {
                 let kind = ImportKind::Glob {
-                    is_prelude: attr::contains_name(&item.attrs, sym::prelude_import),
+                    is_prelude: ast::attr::contains_name(&item.attrs, sym::prelude_import),
                     max_vis: Cell::new(None),
                     id,
                 };
@@ -777,7 +777,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
                     expansion.to_expn_id(),
                     item.span,
                     parent.no_implicit_prelude
-                        || attr::contains_name(&item.attrs, sym::no_implicit_prelude),
+                        || ast::attr::contains_name(&item.attrs, sym::no_implicit_prelude),
                 );
                 self.r.define(parent, ident, TypeNS, (module, vis, sp, expansion));
 
@@ -835,7 +835,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
                     // If the structure is marked as non_exhaustive then lower the visibility
                     // to within the crate.
                     let mut ctor_vis = if vis.is_public()
-                        && attr::contains_name(&item.attrs, sym::non_exhaustive)
+                        && ast::attr::contains_name(&item.attrs, sym::non_exhaustive)
                     {
                         ty::Visibility::Restricted(CRATE_DEF_ID)
                     } else {
@@ -1176,11 +1176,11 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
     }
 
     fn proc_macro_stub(&self, item: &ast::Item) -> Option<(MacroKind, Ident, Span)> {
-        if attr::contains_name(&item.attrs, sym::proc_macro) {
+        if ast::attr::contains_name(&item.attrs, sym::proc_macro) {
             return Some((MacroKind::Bang, item.ident, item.span));
-        } else if attr::contains_name(&item.attrs, sym::proc_macro_attribute) {
+        } else if ast::attr::contains_name(&item.attrs, sym::proc_macro_attribute) {
             return Some((MacroKind::Attr, item.ident, item.span));
-        } else if let Some(attr) = attr::find_by_name(&item.attrs, sym::proc_macro_derive) {
+        } else if let Some(attr) = ast::attr::find_by_name(&item.attrs, sym::proc_macro_derive) {
             if let Some(meta_item_inner) =
                 attr.meta_item_list().and_then(|list| list.get(0).cloned())
             {
@@ -1233,7 +1233,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
         if macro_rules {
             let ident = ident.normalize_to_macros_2_0();
             self.r.macro_names.insert(ident);
-            let is_macro_export = attr::contains_name(&item.attrs, sym::macro_export);
+            let is_macro_export = ast::attr::contains_name(&item.attrs, sym::macro_export);
             let vis = if is_macro_export {
                 ty::Visibility::Public
             } else {
@@ -1507,7 +1507,7 @@ impl<'a, 'ra, 'tcx> Visitor<'a> for BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
 
         // If the variant is marked as non_exhaustive then lower the visibility to within the crate.
         let ctor_vis =
-            if vis.is_public() && attr::contains_name(&variant.attrs, sym::non_exhaustive) {
+            if vis.is_public() && ast::attr::contains_name(&variant.attrs, sym::non_exhaustive) {
                 ty::Visibility::Restricted(CRATE_DEF_ID)
             } else {
                 vis
diff --git a/compiler/rustc_resolve/src/macros.rs b/compiler/rustc_resolve/src/macros.rs
index 6e2af9aae23..891bc494d0c 100644
--- a/compiler/rustc_resolve/src/macros.rs
+++ b/compiler/rustc_resolve/src/macros.rs
@@ -4,10 +4,11 @@
 use std::cell::Cell;
 use std::mem;
 
+use rustc_ast::attr::AttributeExt;
 use rustc_ast::expand::StrippedCfgItem;
 use rustc_ast::{self as ast, Crate, Inline, ItemKind, ModKind, NodeId, attr};
 use rustc_ast_pretty::pprust;
-use rustc_attr::{AttributeExt, StabilityLevel};
+use rustc_attr::StabilityLevel;
 use rustc_data_structures::intern::Interned;
 use rustc_data_structures::sync::Lrc;
 use rustc_errors::{Applicability, StashKey};
diff --git a/compiler/rustc_resolve/src/rustdoc.rs b/compiler/rustc_resolve/src/rustdoc.rs
index 8b14fe31d8c..ed421da0241 100644
--- a/compiler/rustc_resolve/src/rustdoc.rs
+++ b/compiler/rustc_resolve/src/rustdoc.rs
@@ -5,8 +5,8 @@ use pulldown_cmark::{
     BrokenLink, BrokenLinkCallback, CowStr, Event, LinkType, Options, Parser, Tag,
 };
 use rustc_ast as ast;
+use rustc_ast::attr::AttributeExt;
 use rustc_ast::util::comments::beautify_doc_string;
-use rustc_attr::AttributeExt;
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_middle::ty::TyCtxt;
 use rustc_span::def_id::DefId;
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index 9903d0faf43..9e52f6884a4 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -55,7 +55,7 @@ use rustc_trait_selection::traits::wf::object_region_bounds;
 use thin_vec::ThinVec;
 use tracing::{debug, instrument};
 use utils::*;
-use {rustc_ast as ast, rustc_attr as attr, rustc_hir as hir};
+use {rustc_ast as ast, rustc_hir as hir};
 
 pub(crate) use self::types::*;
 pub(crate) use self::utils::{krate, register_res, synthesize_auto_trait_and_blanket_impls};
@@ -2895,7 +2895,7 @@ fn clean_extern_crate<'tcx>(
         && attrs.iter().any(|a| {
             a.has_name(sym::doc)
                 && match a.meta_item_list() {
-                    Some(l) => attr::list_contains_name(&l, sym::inline),
+                    Some(l) => ast::attr::list_contains_name(&l, sym::inline),
                     None => false,
                 }
         })
@@ -3000,8 +3000,8 @@ fn clean_use_statement_inner<'tcx>(
             a.has_name(sym::doc)
                 && match a.meta_item_list() {
                     Some(l) => {
-                        attr::list_contains_name(&l, sym::no_inline)
-                            || attr::list_contains_name(&l, sym::hidden)
+                        ast::attr::list_contains_name(&l, sym::no_inline)
+                            || ast::attr::list_contains_name(&l, sym::hidden)
                     }
                     None => false,
                 }
diff --git a/src/librustdoc/clean/utils.rs b/src/librustdoc/clean/utils.rs
index 617a7ab8097..8aeebdde7bb 100644
--- a/src/librustdoc/clean/utils.rs
+++ b/src/librustdoc/clean/utils.rs
@@ -581,8 +581,7 @@ pub(crate) fn attrs_have_doc_flag<'a>(
     mut attrs: impl Iterator<Item = &'a hir::Attribute>,
     flag: Symbol,
 ) -> bool {
-    attrs
-        .any(|attr| attr.meta_item_list().is_some_and(|l| rustc_attr::list_contains_name(&l, flag)))
+    attrs.any(|attr| attr.meta_item_list().is_some_and(|l| ast::attr::list_contains_name(&l, flag)))
 }
 
 /// A link to `doc.rust-lang.org` that includes the channel name. Use this instead of manual links
diff --git a/src/tools/clippy/clippy_utils/src/msrvs.rs b/src/tools/clippy/clippy_utils/src/msrvs.rs
index 5b1c3465d05..55986acea3d 100644
--- a/src/tools/clippy/clippy_utils/src/msrvs.rs
+++ b/src/tools/clippy/clippy_utils/src/msrvs.rs
@@ -1,4 +1,4 @@
-use rustc_attr::AttributeExt;
+use rustc_ast::attr::AttributeExt;
 use rustc_attr::parse_version;
 use rustc_session::{RustcVersion, Session};
 use rustc_span::{Symbol, sym};