rename rustc_attr to rustc_attr_parsing and create rustc_attr_data_structures

compiler/rustc_attr_parsing/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
+    })
+}

compiler/rustc_attr_parsing/src/attributes/cfg.rs

@@ -0,0 +1,254 @@
+//! 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_attr_data_structures::RustcVersion;
+use rustc_feature::{Features, GatedCfg, find_gated_cfg};
+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::util::UnsupportedLiteralReason;
+use crate::{fluent_generated, parse_version, session_diagnostics};
+
+#[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_parsing_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,
+            })
+        }
+    }
+}

compiler/rustc_attr_parsing/src/attributes/confusables.rs

@@ -0,0 +1,21 @@
+//! Parsing and validation of builtin attributes
+
+use rustc_ast::MetaItemInner;
+use rustc_ast::attr::AttributeExt;
+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)
+}

compiler/rustc_attr_parsing/src/attributes/deprecation.rs

@@ -0,0 +1,149 @@
+//! Parsing and validation of builtin attributes
+
+use rustc_ast::attr::AttributeExt;
+use rustc_ast::{MetaItem, MetaItemInner};
+use rustc_ast_pretty::pprust;
+use rustc_attr_data_structures::{DeprecatedSince, Deprecation};
+use rustc_feature::Features;
+use rustc_session::Session;
+use rustc_span::Span;
+use rustc_span::symbol::{Symbol, sym};
+
+use super::util::UnsupportedLiteralReason;
+use crate::{parse_version, session_diagnostics};
+
+/// 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
+}

compiler/rustc_attr_parsing/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::*;

compiler/rustc_attr_parsing/src/attributes/repr.rs

@@ -0,0 +1,215 @@
+//! Parsing and validation of builtin attributes
+
+use rustc_abi::Align;
+use rustc_ast::attr::AttributeExt;
+use rustc_ast::{self as ast, MetaItemKind};
+use rustc_attr_data_structures::IntType;
+use rustc_attr_data_structures::ReprAttr::*;
+use rustc_session::Session;
+use rustc_span::symbol::{Symbol, sym};
+
+use crate::ReprAttr;
+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 rustc_attr_data_structures::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")
+    }
+}

compiler/rustc_attr_parsing/src/attributes/stability.rs

@@ -0,0 +1,385 @@
+//! Parsing and validation of builtin attributes
+
+use std::num::NonZero;
+
+use rustc_ast::MetaItem;
+use rustc_ast::attr::AttributeExt;
+use rustc_ast_pretty::pprust;
+use rustc_attr_data_structures::{
+    ConstStability, DefaultBodyStability, Stability, StabilityLevel, StableSince, UnstableReason,
+    VERSION_PLACEHOLDER,
+};
+use rustc_errors::ErrorGuaranteed;
+use rustc_session::Session;
+use rustc_span::Span;
+use rustc_span::symbol::{Symbol, sym};
+
+use crate::attributes::util::UnsupportedLiteralReason;
+use crate::{parse_version, session_diagnostics};
+
+/// 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,
+    }
+}

compiler/rustc_attr_parsing/src/attributes/transparency.rs

@@ -0,0 +1,36 @@
+use rustc_ast::attr::AttributeExt;
+use rustc_attr_data_structures::TransparencyError;
+use rustc_span::hygiene::Transparency;
+use rustc_span::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)
+}

compiler/rustc_attr_parsing/src/attributes/util.rs

@@ -0,0 +1,36 @@
+use rustc_ast::attr::{AttributeExt, first_attr_value_str_by_name};
+use rustc_attr_data_structures::RustcVersion;
+use rustc_feature::is_builtin_attr_name;
+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 })
+}

compiler/rustc_attr_parsing/src/lib.rs

@@ -0,0 +1,22 @@
+//! Functions and types dealing with attributes and meta items.
+//!
+//! 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.
+
+// tidy-alphabetical-start
+#![allow(internal_features)]
+#![doc(rust_logo)]
+#![feature(let_chains)]
+#![feature(rustdoc_internals)]
+#![warn(unreachable_pub)]
+// tidy-alphabetical-end
+
+mod attributes;
+mod session_diagnostics;
+
+pub use attributes::*;
+pub use rustc_attr_data_structures::*;
+pub use util::{find_crate_name, is_builtin_attr, parse_version};
+
+rustc_fluent_macro::fluent_messages! { "../messages.ftl" }

compiler/rustc_attr_parsing/src/session_diagnostics.rs

@@ -0,0 +1,419 @@
+use std::num::IntErrorKind;
+
+use rustc_ast as ast;
+use rustc_errors::codes::*;
+use rustc_errors::{Applicability, Diag, DiagCtxtHandle, Diagnostic, EmissionGuarantee, Level};
+use rustc_macros::{Diagnostic, Subdiagnostic};
+use rustc_span::{Span, Symbol};
+
+use crate::attributes::util::UnsupportedLiteralReason;
+use crate::fluent_generated as fluent;
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_expected_one_cfg_pattern, code = E0536)]
+pub(crate) struct ExpectedOneCfgPattern {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_invalid_predicate, code = E0537)]
+pub(crate) struct InvalidPredicate {
+    #[primary_span]
+    pub span: Span,
+
+    pub predicate: String,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_multiple_item, code = E0538)]
+pub(crate) struct MultipleItem {
+    #[primary_span]
+    pub span: Span,
+
+    pub item: String,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_incorrect_meta_item, code = E0539)]
+pub(crate) struct IncorrectMetaItem {
+    #[primary_span]
+    pub span: Span,
+}
+
+/// Error code: E0541
+pub(crate) struct UnknownMetaItem<'a> {
+    pub span: Span,
+    pub item: String,
+    pub expected: &'a [&'a str],
+}
+
+// Manual implementation to be able to format `expected` items correctly.
+impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for UnknownMetaItem<'_> {
+    fn into_diag(self, dcx: DiagCtxtHandle<'a>, level: Level) -> Diag<'a, G> {
+        let expected = self.expected.iter().map(|name| format!("`{name}`")).collect::<Vec<_>>();
+        Diag::new(dcx, level, fluent::attr_parsing_unknown_meta_item)
+            .with_span(self.span)
+            .with_code(E0541)
+            .with_arg("item", self.item)
+            .with_arg("expected", expected.join(", "))
+            .with_span_label(self.span, fluent::attr_parsing_label)
+    }
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_missing_since, code = E0542)]
+pub(crate) struct MissingSince {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_missing_note, code = E0543)]
+pub(crate) struct MissingNote {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_multiple_stability_levels, code = E0544)]
+pub(crate) struct MultipleStabilityLevels {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_invalid_issue_string, code = E0545)]
+pub(crate) struct InvalidIssueString {
+    #[primary_span]
+    pub span: Span,
+
+    #[subdiagnostic]
+    pub cause: Option<InvalidIssueStringCause>,
+}
+
+// The error kinds of `IntErrorKind` are duplicated here in order to allow the messages to be
+// translatable.
+#[derive(Subdiagnostic)]
+pub(crate) enum InvalidIssueStringCause {
+    #[label(attr_parsing_must_not_be_zero)]
+    MustNotBeZero {
+        #[primary_span]
+        span: Span,
+    },
+
+    #[label(attr_parsing_empty)]
+    Empty {
+        #[primary_span]
+        span: Span,
+    },
+
+    #[label(attr_parsing_invalid_digit)]
+    InvalidDigit {
+        #[primary_span]
+        span: Span,
+    },
+
+    #[label(attr_parsing_pos_overflow)]
+    PosOverflow {
+        #[primary_span]
+        span: Span,
+    },
+
+    #[label(attr_parsing_neg_overflow)]
+    NegOverflow {
+        #[primary_span]
+        span: Span,
+    },
+}
+
+impl InvalidIssueStringCause {
+    pub(crate) fn from_int_error_kind(span: Span, kind: &IntErrorKind) -> Option<Self> {
+        match kind {
+            IntErrorKind::Empty => Some(Self::Empty { span }),
+            IntErrorKind::InvalidDigit => Some(Self::InvalidDigit { span }),
+            IntErrorKind::PosOverflow => Some(Self::PosOverflow { span }),
+            IntErrorKind::NegOverflow => Some(Self::NegOverflow { span }),
+            IntErrorKind::Zero => Some(Self::MustNotBeZero { span }),
+            _ => None,
+        }
+    }
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_missing_feature, code = E0546)]
+pub(crate) struct MissingFeature {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_non_ident_feature, code = E0546)]
+pub(crate) struct NonIdentFeature {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_missing_issue, code = E0547)]
+pub(crate) struct MissingIssue {
+    #[primary_span]
+    pub span: Span,
+}
+
+// FIXME: Why is this the same error code as `InvalidReprHintNoParen` and `InvalidReprHintNoValue`?
+// It is more similar to `IncorrectReprFormatGeneric`.
+#[derive(Diagnostic)]
+#[diag(attr_parsing_incorrect_repr_format_packed_one_or_zero_arg, code = E0552)]
+pub(crate) struct IncorrectReprFormatPackedOneOrZeroArg {
+    #[primary_span]
+    pub span: Span,
+}
+#[derive(Diagnostic)]
+#[diag(attr_parsing_incorrect_repr_format_packed_expect_integer, code = E0552)]
+pub(crate) struct IncorrectReprFormatPackedExpectInteger {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_invalid_repr_hint_no_paren, code = E0552)]
+pub(crate) struct InvalidReprHintNoParen {
+    #[primary_span]
+    pub span: Span,
+
+    pub name: String,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_invalid_repr_hint_no_value, code = E0552)]
+pub(crate) struct InvalidReprHintNoValue {
+    #[primary_span]
+    pub span: Span,
+
+    pub name: String,
+}
+
+/// Error code: E0565
+pub(crate) struct UnsupportedLiteral {
+    pub span: Span,
+    pub reason: UnsupportedLiteralReason,
+    pub is_bytestr: bool,
+    pub start_point_span: Span,
+}
+
+impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for UnsupportedLiteral {
+    fn into_diag(self, dcx: DiagCtxtHandle<'a>, level: Level) -> Diag<'a, G> {
+        let mut diag = Diag::new(dcx, level, match self.reason {
+            UnsupportedLiteralReason::Generic => fluent::attr_parsing_unsupported_literal_generic,
+            UnsupportedLiteralReason::CfgString => {
+                fluent::attr_parsing_unsupported_literal_cfg_string
+            }
+            UnsupportedLiteralReason::CfgBoolean => {
+                fluent::attr_parsing_unsupported_literal_cfg_boolean
+            }
+            UnsupportedLiteralReason::DeprecatedString => {
+                fluent::attr_parsing_unsupported_literal_deprecated_string
+            }
+            UnsupportedLiteralReason::DeprecatedKvPair => {
+                fluent::attr_parsing_unsupported_literal_deprecated_kv_pair
+            }
+        });
+        diag.span(self.span);
+        diag.code(E0565);
+        if self.is_bytestr {
+            diag.span_suggestion(
+                self.start_point_span,
+                fluent::attr_parsing_unsupported_literal_suggestion,
+                "",
+                Applicability::MaybeIncorrect,
+            );
+        }
+        diag
+    }
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_invalid_repr_align_need_arg, code = E0589)]
+pub(crate) struct InvalidReprAlignNeedArg {
+    #[primary_span]
+    #[suggestion(code = "align(...)", applicability = "has-placeholders")]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_invalid_repr_generic, code = E0589)]
+pub(crate) struct InvalidReprGeneric<'a> {
+    #[primary_span]
+    pub span: Span,
+
+    pub repr_arg: String,
+    pub error_part: &'a str,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_incorrect_repr_format_align_one_arg, code = E0693)]
+pub(crate) struct IncorrectReprFormatAlignOneArg {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_incorrect_repr_format_expect_literal_integer, code = E0693)]
+pub(crate) struct IncorrectReprFormatExpectInteger {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_incorrect_repr_format_generic, code = E0693)]
+pub(crate) struct IncorrectReprFormatGeneric<'a> {
+    #[primary_span]
+    pub span: Span,
+
+    pub repr_arg: &'a str,
+
+    #[subdiagnostic]
+    pub cause: Option<IncorrectReprFormatGenericCause<'a>>,
+}
+
+#[derive(Subdiagnostic)]
+pub(crate) enum IncorrectReprFormatGenericCause<'a> {
+    #[suggestion(
+        attr_parsing_suggestion,
+        code = "{name}({int})",
+        applicability = "machine-applicable"
+    )]
+    Int {
+        #[primary_span]
+        span: Span,
+
+        #[skip_arg]
+        name: &'a str,
+
+        #[skip_arg]
+        int: u128,
+    },
+
+    #[suggestion(
+        attr_parsing_suggestion,
+        code = "{name}({symbol})",
+        applicability = "machine-applicable"
+    )]
+    Symbol {
+        #[primary_span]
+        span: Span,
+
+        #[skip_arg]
+        name: &'a str,
+
+        #[skip_arg]
+        symbol: Symbol,
+    },
+}
+
+impl<'a> IncorrectReprFormatGenericCause<'a> {
+    pub(crate) fn from_lit_kind(span: Span, kind: &ast::LitKind, name: &'a str) -> Option<Self> {
+        match kind {
+            ast::LitKind::Int(int, ast::LitIntType::Unsuffixed) => {
+                Some(Self::Int { span, name, int: int.get() })
+            }
+            ast::LitKind::Str(symbol, _) => Some(Self::Symbol { span, name, symbol: *symbol }),
+            _ => None,
+        }
+    }
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_rustc_promotable_pairing, code = E0717)]
+pub(crate) struct RustcPromotablePairing {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_rustc_const_stable_indirect_pairing)]
+pub(crate) struct RustcConstStableIndirectPairing {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_rustc_allowed_unstable_pairing, code = E0789)]
+pub(crate) struct RustcAllowedUnstablePairing {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_cfg_predicate_identifier)]
+pub(crate) struct CfgPredicateIdentifier {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_deprecated_item_suggestion)]
+pub(crate) struct DeprecatedItemSuggestion {
+    #[primary_span]
+    pub span: Span,
+
+    #[help]
+    pub is_nightly: bool,
+
+    #[note]
+    pub details: (),
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_expected_single_version_literal)]
+pub(crate) struct ExpectedSingleVersionLiteral {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_expected_version_literal)]
+pub(crate) struct ExpectedVersionLiteral {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_expects_feature_list)]
+pub(crate) struct ExpectsFeatureList {
+    #[primary_span]
+    pub span: Span,
+
+    pub name: String,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_expects_features)]
+pub(crate) struct ExpectsFeatures {
+    #[primary_span]
+    pub span: Span,
+
+    pub name: String,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_invalid_since)]
+pub(crate) struct InvalidSince {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_soft_no_args)]
+pub(crate) struct SoftNoArgs {
+    #[primary_span]
+    pub span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(attr_parsing_unknown_version_literal)]
+pub(crate) struct UnknownVersionLiteral {
+    #[primary_span]
+    pub span: Span,
+}