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Rollup merge of #149215 - JonathanBrouwer:cfg_lints2, r=jdonszelmann

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Emit `check-cfg` lints during attribute parsing rather than evaluation

The goal of this PR is to make the `eval_config_entry` not have any side effects, by moving the check-cfg lints to the attribute parsing. This also helps ensure we do emit the lint in situations where the attribute happens to be parsed, but never evaluated.

cc ``@jdonszelmann`` ``@Urgau`` for a vibe check if you feel like it
This commit is contained in:
Matthias Krüger 2025-12-09 06:17:22 +01:00 • committed by GitHub
commit ece99775da
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GPG key ID: B5690EEEBB952194
21 changed files with 139 additions and 133 deletions
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82
compiler/rustc_attr_parsing/src/attributes/cfg.rs
View file

@ -2,16 +2,16 @@ use std::convert::identity;
use rustc_ast::token::Delimiter;
use rustc_ast::tokenstream::DelimSpan;
use rustc_ast::{AttrItem, Attribute, CRATE_NODE_ID, LitKind, NodeId, ast, token};
use rustc_ast::{AttrItem, Attribute, CRATE_NODE_ID, LitKind, ast, token};
use rustc_errors::{Applicability, PResult};
use rustc_feature::{AttrSuggestionStyle, AttributeTemplate, Features, template};
use rustc_hir::attrs::CfgEntry;
use rustc_hir::lints::AttributeLintKind;
use rustc_hir::{AttrPath, RustcVersion};
use rustc_parse::parser::{ForceCollect, Parser};
use rustc_parse::{exp, parse_in};
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::{ParseSess, feature_err};
use rustc_span::{ErrorGuaranteed, Span, Symbol, sym};
@ -23,10 +23,7 @@ use crate::session_diagnostics::{
AttributeParseError, AttributeParseErrorReason, CfgAttrBadDelim, MetaBadDelimSugg,
ParsedDescription,
};
use crate::{
AttributeParser, CfgMatchesLintEmitter, fluent_generated, parse_version, session_diagnostics,
try_gate_cfg,
};
use crate::{AttributeParser, fluent_generated, parse_version, session_diagnostics, try_gate_cfg};
pub const CFG_TEMPLATE: AttributeTemplate = template!(
List: &["predicate"],
@ -195,43 +192,46 @@ fn parse_name_value<S: Stage>(
}
};
Ok(CfgEntry::NameValue { name, name_span, value, span })
match cx.sess.psess.check_config.expecteds.get(&name) {
Some(ExpectedValues::Some(values)) if !values.contains(&value.map(|(v, _)| v)) => cx
.emit_lint(
UNEXPECTED_CFGS,
AttributeLintKind::UnexpectedCfgValue((name, name_span), value),
span,
),
None if cx.sess.psess.check_config.exhaustive_names => cx.emit_lint(
UNEXPECTED_CFGS,
AttributeLintKind::UnexpectedCfgName((name, name_span), value),
span,
),
_ => { /* not unexpected */ }
}
Ok(CfgEntry::NameValue { name, value: value.map(|(v, _)| v), span })
}
pub fn eval_config_entry(
sess: &Session,
cfg_entry: &CfgEntry,
id: NodeId,
emit_lints: ShouldEmit,
) -> EvalConfigResult {
pub fn eval_config_entry(sess: &Session, cfg_entry: &CfgEntry) -> EvalConfigResult {
match cfg_entry {
CfgEntry::All(subs, ..) => {
let mut all = None;
for sub in subs {
let res = eval_config_entry(sess, sub, id, emit_lints);
// We cannot short-circuit because `eval_config_entry` emits some lints
let res = eval_config_entry(sess, sub);
if !res.as_bool() {
all.get_or_insert(res);
return res;
}
}
all.unwrap_or_else(|| EvalConfigResult::True)
EvalConfigResult::True
}
CfgEntry::Any(subs, span) => {
let mut any = None;
for sub in subs {
let res = eval_config_entry(sess, sub, id, emit_lints);
// We cannot short-circuit because `eval_config_entry` emits some lints
let res = eval_config_entry(sess, sub);
if res.as_bool() {
any.get_or_insert(res);
return res;
}
}
any.unwrap_or_else(|| EvalConfigResult::False {
reason: cfg_entry.clone(),
reason_span: *span,
})
EvalConfigResult::False { reason: cfg_entry.clone(), reason_span: *span }
}
CfgEntry::Not(sub, span) => {
if eval_config_entry(sess, sub, id, emit_lints).as_bool() {
if eval_config_entry(sess, sub).as_bool() {
EvalConfigResult::False { reason: cfg_entry.clone(), reason_span: *span }
} else {
EvalConfigResult::True
@ -244,32 +244,8 @@ pub fn eval_config_entry(
EvalConfigResult::False { reason: cfg_entry.clone(), reason_span: *span }
}
}
CfgEntry::NameValue { name, name_span, value, span } => {
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 */ }
}
}
if sess.psess.config.contains(&(*name, value.map(|(v, _)| v))) {
CfgEntry::NameValue { name, value, span } => {
if sess.psess.config.contains(&(*name, *value)) {
EvalConfigResult::True
} else {
EvalConfigResult::False { reason: cfg_entry.clone(), reason_span: *span }

9
compiler/rustc_attr_parsing/src/attributes/cfg_old.rs
View file

@ -2,6 +2,7 @@ use rustc_ast::{LitKind, MetaItem, MetaItemInner, MetaItemKind, MetaItemLit, Nod
use rustc_ast_pretty::pprust;
use rustc_feature::{Features, GatedCfg, find_gated_cfg};
use rustc_hir::RustcVersion;
use rustc_hir::lints::AttributeLintKind;
use rustc_session::Session;
use rustc_session::config::ExpectedValues;
use rustc_session::lint::builtin::UNEXPECTED_CFGS;
@ -51,10 +52,10 @@ pub fn cfg_matches(
sess,
UNEXPECTED_CFGS,
cfg.span,
BuiltinLintDiag::UnexpectedCfgValue(
BuiltinLintDiag::AttributeLint(AttributeLintKind::UnexpectedCfgValue(
(cfg.name, cfg.name_span),
cfg.value.map(|v| (v, cfg.value_span.unwrap())),
),
)),
);
}
None if sess.psess.check_config.exhaustive_names => {
@ -62,10 +63,10 @@ pub fn cfg_matches(
sess,
UNEXPECTED_CFGS,
cfg.span,
BuiltinLintDiag::UnexpectedCfgName(
BuiltinLintDiag::AttributeLint(AttributeLintKind::UnexpectedCfgName(
(cfg.name, cfg.name_span),
cfg.value.map(|v| (v, cfg.value_span.unwrap())),
),
)),
);
}
_ => { /* not unexpected */ }

8
compiler/rustc_builtin_macros/src/cfg.rs
View file

@ -26,13 +26,7 @@ pub(crate) fn expand_cfg(
ExpandResult::Ready(match parse_cfg(cx, sp, tts) {
Ok(cfg) => {
let matches_cfg = attr::eval_config_entry(
cx.sess,
&cfg,
cx.current_expansion.lint_node_id,
ShouldEmit::ErrorsAndLints,
)
.as_bool();
let matches_cfg = attr::eval_config_entry(cx.sess, &cfg).as_bool();
MacEager::expr(cx.expr_bool(sp, matches_cfg))
}

16
compiler/rustc_builtin_macros/src/cfg_select.rs
View file

@ -1,7 +1,7 @@
use rustc_ast::tokenstream::TokenStream;
use rustc_attr_parsing as attr;
use rustc_attr_parsing::{
CfgSelectBranches, CfgSelectPredicate, EvalConfigResult, ShouldEmit, parse_cfg_select,
CfgSelectBranches, CfgSelectPredicate, EvalConfigResult, parse_cfg_select,
};
use rustc_expand::base::{DummyResult, ExpandResult, ExtCtxt, MacroExpanderResult};
use rustc_span::{Ident, Span, sym};
@ -10,21 +10,13 @@ use crate::errors::{CfgSelectNoMatches, CfgSelectUnreachable};
/// Selects the first arm whose predicate evaluates to true.
fn select_arm(ecx: &ExtCtxt<'_>, branches: CfgSelectBranches) -> Option<(TokenStream, Span)> {
let mut result = None;
for (cfg, tt, arm_span) in branches.reachable {
if let EvalConfigResult::True = attr::eval_config_entry(
&ecx.sess,
&cfg,
ecx.current_expansion.lint_node_id,
ShouldEmit::ErrorsAndLints,
) {
// FIXME(#149215) Ideally we should short-circuit here, but `eval_config_entry` currently emits lints so we cannot do this yet.
result.get_or_insert((tt, arm_span));
if let EvalConfigResult::True = attr::eval_config_entry(&ecx.sess, &cfg) {
return Some((tt, arm_span));
}
}
let wildcard = branches.wildcard.map(|(_, tt, span)| (tt, span));
result.or(wildcard)
branches.wildcard.map(|(_, tt, span)| (tt, span))
}
pub(super) fn expand_cfg_select<'cx>(

7
compiler/rustc_codegen_ssa/src/back/link.rs
View file

@ -13,8 +13,7 @@ use find_msvc_tools;
use itertools::Itertools;
use regex::Regex;
use rustc_arena::TypedArena;
use rustc_ast::CRATE_NODE_ID;
use rustc_attr_parsing::{ShouldEmit, eval_config_entry};
use rustc_attr_parsing::eval_config_entry;
use rustc_data_structures::fx::FxIndexSet;
use rustc_data_structures::memmap::Mmap;
use rustc_data_structures::temp_dir::MaybeTempDir;
@ -3029,9 +3028,7 @@ fn add_dynamic_crate(cmd: &mut dyn Linker, sess: &Session, cratepath: &Path) {
fn relevant_lib(sess: &Session, lib: &NativeLib) -> bool {
match lib.cfg {
Some(ref cfg) => {
eval_config_entry(sess, cfg, CRATE_NODE_ID, ShouldEmit::ErrorsAndLints).as_bool()
}
Some(ref cfg) => eval_config_entry(sess, cfg).as_bool(),
None => true,
}
}

32
compiler/rustc_expand/src/config.rs
View file

@ -163,10 +163,7 @@ pub fn pre_configure_attrs(sess: &Session, attrs: &[Attribute]) -> ast::AttrVec
.iter()
.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, ShouldEmit::Nothing)
.as_bool()
!is_cfg(attr) || strip_unconfigured.cfg_true(attr, ShouldEmit::Nothing).as_bool()
})
.collect()
}
@ -309,14 +306,7 @@ impl<'a> StripUnconfigured<'a> {
);
}
if !attr::eval_config_entry(
self.sess,
&cfg_predicate,
ast::CRATE_NODE_ID,
ShouldEmit::ErrorsAndLints,
)
.as_bool()
{
if !attr::eval_config_entry(self.sess, &cfg_predicate).as_bool() {
return vec![trace_attr];
}
@ -400,23 +390,17 @@ 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, ShouldEmit::ErrorsAndLints).as_bool()
})
attrs
.iter()
.all(|attr| !is_cfg(attr) || self.cfg_true(attr, ShouldEmit::ErrorsAndLints).as_bool())
}
pub(crate) fn cfg_true(
&self,
attr: &Attribute,
node: NodeId,
emit_errors: ShouldEmit,
) -> EvalConfigResult {
pub(crate) fn cfg_true(&self, attr: &Attribute, emit_errors: ShouldEmit) -> EvalConfigResult {
let Some(cfg) = AttributeParser::parse_single(
self.sess,
attr,
attr.span,
node,
self.lint_node_id,
self.features,
emit_errors,
parse_cfg,
@ -426,7 +410,7 @@ impl<'a> StripUnconfigured<'a> {
return EvalConfigResult::True;
};
eval_config_entry(self.sess, &cfg, self.lint_node_id, emit_errors)
eval_config_entry(self.sess, &cfg)
}
/// If attributes are not allowed on expressions, emit an error for `attr`

2
compiler/rustc_expand/src/expand.rs
View file

@ -2213,7 +2213,7 @@ impl<'a, 'b> InvocationCollector<'a, 'b> {
attr: ast::Attribute,
pos: usize,
) -> EvalConfigResult {
let res = self.cfg().cfg_true(&attr, node.node_id(), ShouldEmit::ErrorsAndLints);
let res = self.cfg().cfg_true(&attr, 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.

2
compiler/rustc_hir/src/attrs/data_structures.rs
View file

@ -190,7 +190,7 @@ pub enum CfgEntry {
Any(ThinVec<CfgEntry>, Span),
Not(Box<CfgEntry>, Span),
Bool(bool, Span),
NameValue { name: Symbol, name_span: Span, value: Option<(Symbol, Span)>, span: Span },
NameValue { name: Symbol, value: Option<Symbol>, span: Span },
Version(Option<RustcVersion>, Span),
}

16
compiler/rustc_lint/src/early/diagnostics.rs
View file

@ -169,12 +169,6 @@ pub fn decorate_builtin_lint(
}
.decorate_lint(diag);
}
BuiltinLintDiag::UnexpectedCfgName(name, value) => {
check_cfg::unexpected_cfg_name(sess, tcx, name, value).decorate_lint(diag);
}
BuiltinLintDiag::UnexpectedCfgValue(name, value) => {
check_cfg::unexpected_cfg_value(sess, tcx, name, value).decorate_lint(diag);
}
BuiltinLintDiag::DeprecatedWhereclauseLocation(left_sp, sugg) => {
let suggestion = match sugg {
Some((right_sp, sugg)) => lints::DeprecatedWhereClauseLocationSugg::MoveToEnd {
@ -310,8 +304,8 @@ pub fn decorate_builtin_lint(
}
pub fn decorate_attribute_lint(
_sess: &Session,
_tcx: Option<TyCtxt<'_>>,
sess: &Session,
tcx: Option<TyCtxt<'_>>,
kind: &AttributeLintKind,
diag: &mut Diag<'_, ()>,
) {
@ -367,5 +361,11 @@ pub fn decorate_attribute_lint(
suggestion: lints::UnsafeAttrOutsideUnsafeSuggestion { left, right },
}
.decorate_lint(diag),
&AttributeLintKind::UnexpectedCfgName(name, value) => {
check_cfg::unexpected_cfg_name(sess, tcx, name, value).decorate_lint(diag)
}
&AttributeLintKind::UnexpectedCfgValue(name, value) => {
check_cfg::unexpected_cfg_value(sess, tcx, name, value).decorate_lint(diag)
}
}
}

4
compiler/rustc_lint_defs/src/lib.rs
View file

@ -636,8 +636,6 @@ pub enum BuiltinLintDiag {
},
BreakWithLabelAndLoop(Span),
UnicodeTextFlow(Span, String),
UnexpectedCfgName((Symbol, Span), Option<(Symbol, Span)>),
UnexpectedCfgValue((Symbol, Span), Option<(Symbol, Span)>),
DeprecatedWhereclauseLocation(Span, Option<(Span, String)>),
SingleUseLifetime {
/// Span of the parameter which declares this lifetime.
@ -733,6 +731,8 @@ pub enum AttributeLintKind {
attribute_name_span: Span,
sugg_spans: (Span, Span),
},
UnexpectedCfgName((Symbol, Span), Option<(Symbol, Span)>),
UnexpectedCfgValue((Symbol, Span), Option<(Symbol, Span)>),
}
pub type RegisteredTools = FxIndexSet<Ident>;

7
compiler/rustc_metadata/src/native_libs.rs
View file

@ -2,8 +2,7 @@ use std::ops::ControlFlow;
use std::path::{Path, PathBuf};
use rustc_abi::ExternAbi;
use rustc_ast::CRATE_NODE_ID;
use rustc_attr_parsing::{ShouldEmit, eval_config_entry};
use rustc_attr_parsing::eval_config_entry;
use rustc_data_structures::fx::FxHashSet;
use rustc_hir::attrs::{AttributeKind, NativeLibKind, PeImportNameType};
use rustc_hir::find_attr;
@ -188,9 +187,7 @@ pub(crate) fn collect(tcx: TyCtxt<'_>, LocalCrate: LocalCrate) -> Vec<NativeLib>
pub(crate) fn relevant_lib(sess: &Session, lib: &NativeLib) -> bool {
match lib.cfg {
Some(ref cfg) => {
eval_config_entry(sess, cfg, CRATE_NODE_ID, ShouldEmit::ErrorsAndLints).as_bool()
}
Some(ref cfg) => eval_config_entry(sess, cfg).as_bool(),
None => true,
}
}

2
compiler/rustc_resolve/src/diagnostics.rs
View file

@ -3070,7 +3070,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
continue;
}
let item_was = if let CfgEntry::NameValue { value: Some((feature, _)), .. } = cfg.0 {
let item_was = if let CfgEntry::NameValue { value: Some(feature), .. } = cfg.0 {
errors::ItemWas::BehindFeature { feature, span: cfg.1 }
} else {
errors::ItemWas::CfgOut { span: cfg.1 }

8
tests/ui/check-cfg/nested-cfg.rs Normal file
View file

@ -0,0 +1,8 @@
//@ check-pass
#[cfg(unknown)] //~ WARN unexpected `cfg` condition name
#[cfg(false)]
#[cfg(unknown)] // Should not warn
fn foo() {}
fn main() {}

23
tests/ui/check-cfg/nested-cfg.stderr Normal file
View file

@ -0,0 +1,23 @@
warning: unexpected `cfg` condition name: `unknown`
--> $DIR/nested-cfg.rs:3:7
|
LL | #[cfg(unknown)]
| ^^^^^^^
|
= help: expected names are: `FALSE` and `test` and 31 more
= help: to expect this configuration use `--check-cfg=cfg(unknown)`
= note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
= note: `#[warn(unexpected_cfgs)]` on by default
help: found config with similar value
|
LL - #[cfg(unknown)]
LL + #[cfg(target_os = "unknown")]
|
help: found config with similar value
|
LL - #[cfg(unknown)]
LL + #[cfg(target_vendor = "unknown")]
|
warning: 1 warning emitted

2
tests/ui/feature-gates/feature-gate-link_cfg.rs
View file

@ -1,4 +1,4 @@
#[link(name = "foo", cfg(foo))]
#[link(name = "foo", cfg(false))]
//~^ ERROR: is unstable
extern "C" {}

4
tests/ui/feature-gates/feature-gate-link_cfg.stderr
View file

@ -1,8 +1,8 @@
error[E0658]: link cfg is unstable
--> $DIR/feature-gate-link_cfg.rs:1:22
|
LL | #[link(name = "foo", cfg(foo))]
| ^^^^^^^^
LL | #[link(name = "foo", cfg(false))]
| ^^^^^^^^^^
|
= help: add `#![feature(link_cfg)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

2
tests/ui/link-native-libs/link-cfg-works.rs
View file

@ -7,7 +7,7 @@
extern crate link_cfg_works_transitive_dylib;
extern crate link_cfg_works_transitive_rlib;
#[link(name = "foo", cfg(foo))]
#[link(name = "foo", cfg(false))]
extern "C" {}
fn main() {}

3
tests/ui/macros/cfg.rs
View file

@ -2,5 +2,6 @@ fn main() {
cfg!(); //~ ERROR macro requires a cfg-pattern
cfg!(123); //~ ERROR malformed `cfg` macro input
cfg!(foo = 123); //~ ERROR malformed `cfg` macro input
cfg!(foo, bar); //~ ERROR expected 1 cfg-pattern
cfg!(false, false); //~ ERROR expected 1 cfg-pattern
cfg!(foo); //~ WARN unexpected `cfg` condition name: `foo`
}

17
tests/ui/macros/cfg.stderr
View file

@ -29,9 +29,20 @@ LL | cfg!(foo = 123);
error: expected 1 cfg-pattern
--> $DIR/cfg.rs:5:5
|
LL | cfg!(foo, bar);
| ^^^^^^^^^^^^^^
LL | cfg!(false, false);
| ^^^^^^^^^^^^^^^^^^
error: aborting due to 4 previous errors
warning: unexpected `cfg` condition name: `foo`
--> $DIR/cfg.rs:6:10
|
LL | cfg!(foo);
| ^^^
|
= help: expected names are: `FALSE` and `test` and 31 more
= help: to expect this configuration use `--check-cfg=cfg(foo)`
= note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
= note: `#[warn(unexpected_cfgs)]` on by default
error: aborting due to 4 previous errors; 1 warning emitted
For more information about this error, try `rustc --explain E0539`.

2
tests/ui/macros/cfg_select.rs
View file

@ -89,9 +89,11 @@ cfg_select! {
cfg_select! {
a + 1 => {}
//~^ ERROR expected one of `(`, `::`, `=>`, or `=`, found `+`
//~| WARN unexpected `cfg` condition name
}
cfg_select! {
cfg!() => {}
//~^ ERROR expected one of `(`, `::`, `=>`, or `=`, found `!`
//~| WARN unexpected `cfg` condition name
}

24
tests/ui/macros/cfg_select.stderr
View file

@ -60,12 +60,32 @@ LL | a + 1 => {}
| ^ expected one of `(`, `::`, `=>`, or `=`
error: expected one of `(`, `::`, `=>`, or `=`, found `!`
--> $DIR/cfg_select.rs:95:8
--> $DIR/cfg_select.rs:96:8
|
LL | cfg!() => {}
| ^ expected one of `(`, `::`, `=>`, or `=`
error: aborting due to 9 previous errors; 1 warning emitted
warning: unexpected `cfg` condition name: `a`
--> $DIR/cfg_select.rs:90:5
|
LL | a + 1 => {}
| ^ help: found config with similar value: `target_feature = "a"`
|
= help: expected names are: `FALSE` and `test` and 31 more
= help: to expect this configuration use `--check-cfg=cfg(a)`
= note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
= note: `#[warn(unexpected_cfgs)]` on by default
warning: unexpected `cfg` condition name: `cfg`
--> $DIR/cfg_select.rs:96:5
|
LL | cfg!() => {}
| ^^^
|
= help: to expect this configuration use `--check-cfg=cfg(cfg)`
= note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration
error: aborting due to 9 previous errors; 3 warnings emitted
Some errors have detailed explanations: E0537, E0539.
For more information about an error, try `rustc --explain E0537`.