Fix ice for feature-gated cfg attributes applied to the crate

JonathanBrouwer · JonathanBrouwer · commit 8e400f97e592 · 2025-07-15T23:28:15.000+02:00
Signed-off-by: Jonathan Brouwer &lt;jonathantbrouwer@gmail.com&gt;
diff --git a/compiler/rustc_attr_parsing/src/attributes/cfg.rs b/compiler/rustc_attr_parsing/src/attributes/cfg.rs
@@ -9,7 +9,7 @@ use rustc_session::parse::feature_err;
 use rustc_span::{Span, Symbol, sym};
 use thin_vec::ThinVec;
 
-use crate::context::{AcceptContext, Stage};
+use crate::context::{AcceptContext, ShouldEmit, Stage};
 use crate::parser::{ArgParser, MetaItemListParser, MetaItemOrLitParser, NameValueParser};
 use crate::{
     CfgMatchesLintEmitter, fluent_generated, parse_version, session_diagnostics, try_gate_cfg,
@@ -90,7 +90,7 @@ fn parse_cfg_entry_version<S: Stage>(
     list: &MetaItemListParser<'_>,
     meta_span: Span,
 ) -> Option<CfgEntry> {
-    try_gate_cfg(sym::version, meta_span, cx.sess(), Some(cx.features()));
+    try_gate_cfg(sym::version, meta_span, cx.sess(), cx.features_option());
     let Some(version) = list.single() else {
         cx.emit_err(session_diagnostics::ExpectedSingleVersionLiteral { span: list.span });
         return None;
@@ -119,7 +119,9 @@ fn parse_cfg_entry_target<S: Stage>(
     list: &MetaItemListParser<'_>,
     meta_span: Span,
 ) -> Option<CfgEntry> {
-    if !cx.features().cfg_target_compact() {
+    if let Some(features) = cx.features_option()
+        && !features.cfg_target_compact()
+    {
         feature_err(
             cx.sess(),
             sym::cfg_target_compact,
@@ -186,12 +188,13 @@ pub fn eval_config_entry(
     cfg_entry: &CfgEntry,
     id: NodeId,
     features: Option<&Features>,
+    emit_lints: ShouldEmit,
 ) -> EvalConfigResult {
     match cfg_entry {
         CfgEntry::All(subs, ..) => {
             let mut all = None;
             for sub in subs {
-                let res = eval_config_entry(sess, sub, id, features);
+                let res = eval_config_entry(sess, sub, id, features, emit_lints);
                 // We cannot short-circuit because `eval_config_entry` emits some lints
                 if !res.as_bool() {
                     all.get_or_insert(res);
@@ -202,7 +205,7 @@ pub fn eval_config_entry(
         CfgEntry::Any(subs, span) => {
             let mut any = None;
             for sub in subs {
-                let res = eval_config_entry(sess, sub, id, features);
+                let res = eval_config_entry(sess, sub, id, features, emit_lints);
                 // We cannot short-circuit because `eval_config_entry` emits some lints
                 if res.as_bool() {
                     any.get_or_insert(res);
@@ -214,7 +217,7 @@ pub fn eval_config_entry(
             })
         }
         CfgEntry::Not(sub, span) => {
-            if eval_config_entry(sess, sub, id, features).as_bool() {
+            if eval_config_entry(sess, sub, id, features, emit_lints).as_bool() {
                 EvalConfigResult::False { reason: cfg_entry.clone(), reason_span: *span }
             } else {
                 EvalConfigResult::True
@@ -228,24 +231,28 @@ pub fn eval_config_entry(
             }
         }
         CfgEntry::NameValue { name, name_span, value, span } => {
-            match sess.psess.check_config.expecteds.get(name) {
-                Some(ExpectedValues::Some(values)) if !values.contains(&value.map(|(v, _)| v)) => {
-                    id.emit_span_lint(
-                        sess,
-                        UNEXPECTED_CFGS,
-                        *span,
-                        BuiltinLintDiag::UnexpectedCfgValue((*name, *name_span), *value),
-                    );
+            if let ShouldEmit::ErrorsAndLints = emit_lints {
+                match sess.psess.check_config.expecteds.get(name) {
+                    Some(ExpectedValues::Some(values))
+                        if !values.contains(&value.map(|(v, _)| v)) =>
+                    {
+                        id.emit_span_lint(
+                            sess,
+                            UNEXPECTED_CFGS,
+                            *span,
+                            BuiltinLintDiag::UnexpectedCfgValue((*name, *name_span), *value),
+                        );
+                    }
+                    None if sess.psess.check_config.exhaustive_names => {
+                        id.emit_span_lint(
+                            sess,
+                            UNEXPECTED_CFGS,
+                            *span,
+                            BuiltinLintDiag::UnexpectedCfgName((*name, *name_span), *value),
+                        );
+                    }
+                    _ => { /* not unexpected */ }
                 }
-                None if sess.psess.check_config.exhaustive_names => {
-                    id.emit_span_lint(
-                        sess,
-                        UNEXPECTED_CFGS,
-                        *span,
-                        BuiltinLintDiag::UnexpectedCfgName((*name, *name_span), *value),
-                    );
-                }
-                _ => { /* not unexpected */ }
             }
 
             if sess.psess.config.contains(&(*name, value.map(|(v, _)| v))) {
diff --git a/compiler/rustc_attr_parsing/src/context.rs b/compiler/rustc_attr_parsing/src/context.rs
@@ -223,7 +223,7 @@ impl Stage for Early {
         sess: &'sess Session,
         diag: impl for<'x> Diagnostic<'x>,
     ) -> ErrorGuaranteed {
-        if self.emit_errors {
+        if self.emit_errors.should_emit() {
             sess.dcx().emit_err(diag)
         } else {
             sess.dcx().create_err(diag).delay_as_bug()
@@ -254,7 +254,7 @@ pub struct Early {
     /// Whether to emit errors or delay them as a bug
     /// For most attributes, the attribute will be parsed again in the `Late` stage and in this case the errors should be delayed
     /// But for some, such as `cfg`, the attribute will be removed before the `Late` stage so errors must be emitted
-    pub emit_errors: bool,
+    pub emit_errors: ShouldEmit,
 }
 /// used when parsing attributes during ast lowering
 pub struct Late;
@@ -555,6 +555,25 @@ pub enum OmitDoc {
     Skip,
 }
 
+#[derive(Copy, Clone)]
+pub enum ShouldEmit {
+    /// The operation will emit errors and lints.
+    /// This is usually what you need.
+    ErrorsAndLints,
+    /// The operation will emit *not* errors and lints.
+    /// Use this if you are *sure* that this operation will be called at a different time with `ShouldEmit::Emit`.
+    Nothing,
+}
+
+impl ShouldEmit {
+    pub fn should_emit(&self) -> bool {
+        match self {
+            ShouldEmit::ErrorsAndLints => true,
+            ShouldEmit::Nothing => false,
+        }
+    }
+}
+
 /// Context created once, for example as part of the ast lowering
 /// context, through which all attributes can be lowered.
 pub struct AttributeParser<'sess, S: Stage = Late> {
@@ -597,7 +616,7 @@ impl<'sess> AttributeParser<'sess, Early> {
             tools: Vec::new(),
             parse_only: Some(sym),
             sess,
-            stage: Early { emit_errors: false },
+            stage: Early { emit_errors: ShouldEmit::Nothing },
         };
         let mut parsed = p.parse_attribute_list(
             attrs,
@@ -620,7 +639,7 @@ impl<'sess> AttributeParser<'sess, Early> {
         target_span: Span,
         target_node_id: NodeId,
         features: Option<&'sess Features>,
-        emit_errors: bool,
+        emit_errors: ShouldEmit,
         parse_fn: fn(cx: &mut AcceptContext<'_, '_, Early>, item: &ArgParser<'_>) -> T,
         template: &AttributeTemplate,
     ) -> T {
diff --git a/compiler/rustc_attr_parsing/src/lib.rs b/compiler/rustc_attr_parsing/src/lib.rs
@@ -95,7 +95,7 @@ pub use attributes::cfg_old::*;
 pub use attributes::util::{
     find_crate_name, is_builtin_attr, is_doc_alias_attrs_contain_symbol, parse_version,
 };
-pub use context::{AttributeParser, Early, Late, OmitDoc};
+pub use context::{AttributeParser, Early, Late, OmitDoc, ShouldEmit};
 pub use lints::emit_attribute_lint;
 
 rustc_fluent_macro::fluent_messages! { "../messages.ftl" }
diff --git a/compiler/rustc_expand/src/config.rs b/compiler/rustc_expand/src/config.rs
@@ -12,7 +12,7 @@ use rustc_ast::{
 };
 use rustc_attr_parsing as attr;
 use rustc_attr_parsing::{
-    AttributeParser, CFG_TEMPLATE, EvalConfigResult, eval_config_entry, parse_cfg_attr,
+    AttributeParser, CFG_TEMPLATE, EvalConfigResult, ShouldEmit, eval_config_entry, parse_cfg_attr,
 };
 use rustc_data_structures::flat_map_in_place::FlatMapInPlace;
 use rustc_feature::{
@@ -167,7 +167,9 @@ pub fn pre_configure_attrs(sess: &Session, attrs: &[Attribute]) -> ast::AttrVec
         .flat_map(|attr| strip_unconfigured.process_cfg_attr(attr))
         .take_while(|attr| {
             !is_cfg(attr)
-                || strip_unconfigured.cfg_true(attr, strip_unconfigured.lint_node_id).as_bool()
+                || strip_unconfigured
+                    .cfg_true(attr, strip_unconfigured.lint_node_id, ShouldEmit::Nothing)
+                    .as_bool()
         })
         .collect()
 }
@@ -401,10 +403,18 @@ impl<'a> StripUnconfigured<'a> {
 
     /// Determines if a node with the given attributes should be included in this configuration.
     fn in_cfg(&self, attrs: &[Attribute]) -> bool {
-        attrs.iter().all(|attr| !is_cfg(attr) || self.cfg_true(attr, self.lint_node_id).as_bool())
+        attrs.iter().all(|attr| {
+            !is_cfg(attr)
+                || self.cfg_true(attr, self.lint_node_id, ShouldEmit::ErrorsAndLints).as_bool()
+        })
     }
 
-    pub(crate) fn cfg_true(&self, attr: &Attribute, node: NodeId) -> EvalConfigResult {
+    pub(crate) fn cfg_true(
+        &self,
+        attr: &Attribute,
+        node: NodeId,
+        emit_errors: ShouldEmit,
+    ) -> EvalConfigResult {
         // We need to run this to do basic validation of the attribute, such as that lits are valid, etc
         // FIXME(jdonszelmann) this should not be necessary in the future
         match validate_attr::parse_meta(&self.sess.psess, attr) {
@@ -428,15 +438,15 @@ impl<'a> StripUnconfigured<'a> {
             attr.span,
             node,
             self.features,
-            true,
+            emit_errors,
             parse_cfg_attr,
             &CFG_TEMPLATE,
         ) else {
             // Cfg attribute was not parsable, give up
             return EvalConfigResult::True;
         };
 
-        eval_config_entry(self.sess, &cfg, self.lint_node_id, self.features)
+        eval_config_entry(self.sess, &cfg, self.lint_node_id, self.features, emit_errors)
     }
 
     /// If attributes are not allowed on expressions, emit an error for `attr`
diff --git a/compiler/rustc_expand/src/expand.rs b/compiler/rustc_expand/src/expand.rs
@@ -13,7 +13,7 @@ use rustc_ast::{
     MetaItemKind, ModKind, NodeId, PatKind, StmtKind, TyKind, token,
 };
 use rustc_ast_pretty::pprust;
-use rustc_attr_parsing::EvalConfigResult;
+use rustc_attr_parsing::{EvalConfigResult, ShouldEmit};
 use rustc_data_structures::flat_map_in_place::FlatMapInPlace;
 use rustc_errors::PResult;
 use rustc_feature::Features;
@@ -2171,7 +2171,7 @@ impl<'a, 'b> InvocationCollector<'a, 'b> {
         attr: ast::Attribute,
         pos: usize,
     ) -> EvalConfigResult {
-        let res = self.cfg().cfg_true(&attr, node.node_id());
+        let res = self.cfg().cfg_true(&attr, node.node_id(), ShouldEmit::ErrorsAndLints);
         if res.as_bool() {
             // A trace attribute left in AST in place of the original `cfg` attribute.
             // It can later be used by lints or other diagnostics.
diff --git a/compiler/rustc_resolve/src/def_collector.rs b/compiler/rustc_resolve/src/def_collector.rs
@@ -2,7 +2,7 @@ use std::mem;
 
 use rustc_ast::visit::FnKind;
 use rustc_ast::*;
-use rustc_attr_parsing::{AttributeParser, Early, OmitDoc};
+use rustc_attr_parsing::{AttributeParser, Early, OmitDoc, ShouldEmit};
 use rustc_expand::expand::AstFragment;
 use rustc_hir as hir;
 use rustc_hir::def::{CtorKind, CtorOf, DefKind};
@@ -132,7 +132,7 @@ impl<'a, 'ra, 'tcx> visit::Visitor<'a> for DefCollector<'a, 'ra, 'tcx> {
                     &self.resolver.tcx.sess,
                     self.resolver.tcx.features(),
                     Vec::new(),
-                    Early { emit_errors: false },
+                    Early { emit_errors: ShouldEmit::Nothing },
                 );
                 let attrs = parser.parse_attribute_list(
                     &i.attrs,
