Move `cfg` -> `cfg_old`

3 files changed, 250 insertions, 1 deletions

diff --git a/compiler/rustc_attr_parsing/src/attributes/cfg_old.rs b/compiler/rustc_attr_parsing/src/attributes/cfg_old.rs
new file mode 100644
index 00000000000..c5025a8b6ea
--- /dev/null
+++ b/compiler/rustc_attr_parsing/src/attributes/cfg_old.rs
@@ -0,0 +1,247 @@
+use rustc_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::builtin::UNEXPECTED_CFGS;
+use rustc_session::lint::{BuiltinLintDiag, Lint};
+use rustc_session::parse::feature_err;
+use rustc_span::{Span, Symbol, sym};
+
+use crate::session_diagnostics::{self, UnsupportedLiteralReason};
+use crate::{fluent_generated, parse_version};
+
+/// Emitter of a builtin lint from `cfg_matches`.
+///
+/// Used to support emitting a lint (currently on check-cfg), either:
+///  - as an early buffered lint (in `rustc`)
+///  - or has a "normal" lint from HIR (in `rustdoc`)
+pub trait CfgMatchesLintEmitter {
+    fn emit_span_lint(&self, sess: &Session, lint: &'static Lint, sp: Span, diag: BuiltinLintDiag);
+}
+
+impl CfgMatchesLintEmitter for NodeId {
+    fn emit_span_lint(&self, sess: &Session, lint: &'static Lint, sp: Span, diag: BuiltinLintDiag) {
+        sess.psess.buffer_lint(lint, sp, *self, diag);
+    }
+}
+
+#[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: &MetaItemInner,
+    sess: &Session,
+    lint_emitter: impl CfgMatchesLintEmitter,
+    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) => {
+                lint_emitter.emit_span_lint(
+                    sess,
+                    UNEXPECTED_CFGS,
+                    cfg.span,
+                    BuiltinLintDiag::UnexpectedCfgValue(
+                        (cfg.name, cfg.name_span),
+                        cfg.value.map(|v| (v, cfg.value_span.unwrap())),
+                    ),
+                );
+            }
+            None if sess.psess.check_config.exhaustive_names => {
+                lint_emitter.emit_span_lint(
+                    sess,
+                    UNEXPECTED_CFGS,
+                    cfg.span,
+                    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))
+    })
+}
+
+pub 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: &MetaItemInner,
+    sess: &Session,
+    features: Option<&Features>,
+    eval: &mut impl FnMut(Condition) -> bool,
+) -> bool {
+    let dcx = sess.dcx();
+
+    let cfg = match cfg {
+        MetaItemInner::MetaItem(meta_item) => meta_item,
+        MetaItemInner::Lit(MetaItemLit { kind: LitKind::Bool(b), .. }) => {
+            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 {
+        MetaItemKind::List(mis) if cfg.has_name(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_overridable() > min_version
+            } else {
+                RustcVersion::current_overridable() >= min_version
+            }
+        }
+        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() {
+                Some(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)),
+                Some(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)),
+                Some(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)
+                }
+                Some(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(&MetaItemInner::MetaItem(mi), sess, features, eval)
+                    })
+                }
+                _ => {
+                    dcx.emit_err(session_diagnostics::InvalidPredicate {
+                        span: cfg.span,
+                        predicate: pprust::path_to_string(&cfg.path),
+                    });
+                    false
+                }
+            }
+        }
+        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
+        }
+        MetaItemKind::Word | 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_parsing/src/attributes/mod.rs b/compiler/rustc_attr_parsing/src/attributes/mod.rs
index 68c716d1a99..200f1381960 100644
--- a/compiler/rustc_attr_parsing/src/attributes/mod.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/mod.rs
@@ -27,6 +27,7 @@ use crate::session_diagnostics::UnusedMultiple;
 
 pub(crate) mod allow_unstable;
 pub(crate) mod cfg;
+pub(crate) mod cfg_old;
 pub(crate) mod codegen_attrs;
 pub(crate) mod confusables;
 pub(crate) mod deprecation;
diff --git a/compiler/rustc_attr_parsing/src/lib.rs b/compiler/rustc_attr_parsing/src/lib.rs
index 47eeb63bad3..2102a26108b 100644
--- a/compiler/rustc_attr_parsing/src/lib.rs
+++ b/compiler/rustc_attr_parsing/src/lib.rs
@@ -90,7 +90,8 @@ mod lints;
 pub mod parser;
 mod session_diagnostics;
 
-pub use attributes::cfg::*;
+pub use attributes::cfg::{CFG_TEMPLATE, EvalConfigResult, eval_config_entry, parse_cfg_attr};
+pub use attributes::cfg_old::*;
 pub use attributes::util::{
     find_crate_name, is_builtin_attr, is_doc_alias_attrs_contain_symbol, parse_version,
 };