1: split rustc_attr/builtins.rs to work on individual attributes with fewer conflicts

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
+    })
+}

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,
+            })
+        }
+    }
+}

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)
+}