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Port cfg!() macro to the new attribute parsing system #147945

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Merged
merged 3 commits into from
Nov 4, 2025
Merged

Port cfg!() macro to the new attribute parsing system #147945

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001be2f
Make `parse_cfg_entry` output `ErrorGuaranteed` on failure
JonathanBrouwer Oct 21, 2025
b78800f
Port `cfg!()` macro to the new attribute parsing system
JonathanBrouwer Oct 21, 2025
a628e71
Add `ParsedDescription` to the attribute parsers
JonathanBrouwer Oct 29, 2025
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73 changes: 37 additions & 36 deletions compiler/rustc_attr_parsing/src/attributes/cfg.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -12,13 +12,14 @@ 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::{Span, Symbol, sym};
use rustc_span::{ErrorGuaranteed, Span, Symbol, sym};
use thin_vec::ThinVec;

use crate::context::{AcceptContext, ShouldEmit, Stage};
use crate::parser::{ArgParser, MetaItemListParser, MetaItemOrLitParser, NameValueParser};
use crate::session_diagnostics::{
AttributeParseError, AttributeParseErrorReason, CfgAttrBadDelim, MetaBadDelimSugg,
ParsedDescription,
};
use crate::{
AttributeParser, CfgMatchesLintEmitter, fluent_generated, parse_version, session_diagnostics,
Expand Down Expand Up @@ -47,20 +48,19 @@ pub fn parse_cfg<'c, S: Stage>(
cx.expected_single_argument(list.span);
return None;
};
parse_cfg_entry(cx, single)
parse_cfg_entry(cx, single).ok()
}

pub(crate) fn parse_cfg_entry<S: Stage>(
pub fn parse_cfg_entry<S: Stage>(
cx: &mut AcceptContext<'_, '_, S>,
item: &MetaItemOrLitParser<'_>,
) -> Option<CfgEntry> {
Some(match item {
) -> Result<CfgEntry, ErrorGuaranteed> {
Ok(match item {
MetaItemOrLitParser::MetaItemParser(meta) => match meta.args() {
ArgParser::List(list) => match meta.path().word_sym() {
Some(sym::not) => {
let Some(single) = list.single() else {
cx.expected_single_argument(list.span);
return None;
return Err(cx.expected_single_argument(list.span));
};
CfgEntry::Not(Box::new(parse_cfg_entry(cx, single)?), list.span)
}
Expand All @@ -75,49 +75,47 @@ pub(crate) fn parse_cfg_entry<S: Stage>(
Some(sym::target) => parse_cfg_entry_target(cx, list, meta.span())?,
Some(sym::version) => parse_cfg_entry_version(cx, list, meta.span())?,
_ => {
cx.emit_err(session_diagnostics::InvalidPredicate {
return Err(cx.emit_err(session_diagnostics::InvalidPredicate {
span: meta.span(),
predicate: meta.path().to_string(),
});
return None;
}));
}
},
a @ (ArgParser::NoArgs | ArgParser::NameValue(_)) => {
let Some(name) = meta.path().word_sym() else {
cx.expected_identifier(meta.path().span());
return None;
return Err(cx.expected_identifier(meta.path().span()));
};
parse_name_value(name, meta.path().span(), a.name_value(), meta.span(), cx)?
}
},
MetaItemOrLitParser::Lit(lit) => match lit.kind {
LitKind::Bool(b) => CfgEntry::Bool(b, lit.span),
_ => {
cx.expected_identifier(lit.span);
return None;
}
_ => return Err(cx.expected_identifier(lit.span)),
},
MetaItemOrLitParser::Err(_, _) => return None,
MetaItemOrLitParser::Err(_, err) => return Err(*err),
})
}

fn parse_cfg_entry_version<S: Stage>(
cx: &mut AcceptContext<'_, '_, S>,
list: &MetaItemListParser<'_>,
meta_span: Span,
) -> Option<CfgEntry> {
) -> Result<CfgEntry, ErrorGuaranteed> {
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;
return Err(
cx.emit_err(session_diagnostics::ExpectedSingleVersionLiteral { span: list.span })
);
};
let Some(version_lit) = version.lit() else {
cx.emit_err(session_diagnostics::ExpectedVersionLiteral { span: version.span() });
return None;
return Err(
cx.emit_err(session_diagnostics::ExpectedVersionLiteral { span: version.span() })
);
};
let Some(version_str) = version_lit.value_str() else {
cx.emit_err(session_diagnostics::ExpectedVersionLiteral { span: version_lit.span });
return None;
return Err(
cx.emit_err(session_diagnostics::ExpectedVersionLiteral { span: version_lit.span })
);
};

let min_version = parse_version(version_str).or_else(|| {
Expand All @@ -127,14 +125,14 @@ fn parse_cfg_entry_version<S: Stage>(
None
});

Some(CfgEntry::Version(min_version, list.span))
Ok(CfgEntry::Version(min_version, list.span))
}

fn parse_cfg_entry_target<S: Stage>(
cx: &mut AcceptContext<'_, '_, S>,
list: &MetaItemListParser<'_>,
meta_span: Span,
) -> Option<CfgEntry> {
) -> Result<CfgEntry, ErrorGuaranteed> {
if let Some(features) = cx.features_option()
&& !features.cfg_target_compact()
{
Expand All @@ -161,17 +159,16 @@ fn parse_cfg_entry_target<S: Stage>(

// Then, parse it as a name-value item
let Some(name) = sub_item.path().word_sym() else {
cx.expected_identifier(sub_item.path().span());
return None;
return Err(cx.expected_identifier(sub_item.path().span()));
};
let name = Symbol::intern(&format!("target_{name}"));
if let Some(cfg) =
if let Ok(cfg) =
parse_name_value(name, sub_item.path().span(), Some(nv), sub_item.span(), cx)
{
result.push(cfg);
}
}
Some(CfgEntry::All(result, list.span))
Ok(CfgEntry::All(result, list.span))
}

fn parse_name_value<S: Stage>(
Expand All @@ -180,21 +177,22 @@ fn parse_name_value<S: Stage>(
value: Option<&NameValueParser>,
span: Span,
cx: &mut AcceptContext<'_, '_, S>,
) -> Option<CfgEntry> {
) -> Result<CfgEntry, ErrorGuaranteed> {
try_gate_cfg(name, span, cx.sess(), cx.features_option());

let value = match value {
None => None,
Some(value) => {
let Some(value_str) = value.value_as_str() else {
cx.expected_string_literal(value.value_span, Some(value.value_as_lit()));
return None;
return Err(
cx.expected_string_literal(value.value_span, Some(value.value_as_lit()))
);
};
Some((value_str, value.value_span))
}
};

Some(CfgEntry::NameValue { name, name_span, value, span })
Ok(CfgEntry::NameValue { name, name_span, value, span })
}

pub fn eval_config_entry(
Expand Down Expand Up @@ -355,7 +353,8 @@ pub fn parse_cfg_attr(
span,
attr_span: cfg_attr.span,
template: CFG_ATTR_TEMPLATE,
attribute: AttrPath::from_ast(&cfg_attr.get_normal_item().path),
path: AttrPath::from_ast(&cfg_attr.get_normal_item().path),
description: ParsedDescription::Attribute,
reason,
suggestions: CFG_ATTR_TEMPLATE.suggestions(Some(cfg_attr.style), sym::cfg_attr),
});
Expand Down Expand Up @@ -398,6 +397,7 @@ fn parse_cfg_attr_internal<'a>(
.into_boxed_slice(),
span: attribute.span,
},
ParsedDescription::Attribute,
pred_span,
CRATE_NODE_ID,
features,
Expand All @@ -406,7 +406,8 @@ fn parse_cfg_attr_internal<'a>(
parse_cfg_entry,
&CFG_ATTR_TEMPLATE,
)
.ok_or_else(|| {
.map_err(|_err: ErrorGuaranteed| {
// We have an `ErrorGuaranteed` so this delayed bug cannot fail, but we need a `Diag` for the `PResult` so we make one anyways
let mut diag = sess.dcx().struct_err(
"cfg_entry parsing failing with `ShouldEmit::ErrorsAndLints` should emit a error.",
);
Expand Down
2 changes: 1 addition & 1 deletion compiler/rustc_attr_parsing/src/attributes/link_attrs.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -396,7 +396,7 @@ impl LinkParser {
)
.emit();
}
*cfg = parse_cfg_entry(cx, link_cfg);
*cfg = parse_cfg_entry(cx, link_cfg).ok();
true
}

Expand Down
47 changes: 33 additions & 14 deletions compiler/rustc_attr_parsing/src/context.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -71,7 +71,9 @@ use crate::attributes::traits::{
use crate::attributes::transparency::TransparencyParser;
use crate::attributes::{AttributeParser as _, Combine, Single, WithoutArgs};
use crate::parser::{ArgParser, PathParser};
use crate::session_diagnostics::{AttributeParseError, AttributeParseErrorReason, UnknownMetaItem};
use crate::session_diagnostics::{
AttributeParseError, AttributeParseErrorReason, ParsedDescription, UnknownMetaItem,
};
use crate::target_checking::AllowedTargets;

type GroupType<S> = LazyLock<GroupTypeInner<S>>;
Expand Down Expand Up @@ -353,6 +355,10 @@ pub struct AcceptContext<'f, 'sess, S: Stage> {
/// Whether it is an inner or outer attribute
pub(crate) attr_style: AttrStyle,

/// A description of the thing we are parsing using this attribute parser
/// We are not only using these parsers for attributes, but also for macros such as the `cfg!()` macro.
pub(crate) parsed_description: ParsedDescription,

/// The expected structure of the attribute.
///
/// Used in reporting errors to give a hint to users what the attribute *should* look like.
Expand Down Expand Up @@ -431,7 +437,8 @@ impl<'f, 'sess: 'f, S: Stage> AcceptContext<'f, 'sess, S> {
span,
attr_span: self.attr_span,
template: self.template.clone(),
attribute: self.attr_path.clone(),
path: self.attr_path.clone(),
description: self.parsed_description,
reason: AttributeParseErrorReason::ExpectedStringLiteral {
byte_string: actual_literal.and_then(|i| {
i.kind.is_bytestr().then(|| self.sess().source_map().start_point(i.span))
Expand All @@ -446,7 +453,8 @@ impl<'f, 'sess: 'f, S: Stage> AcceptContext<'f, 'sess, S> {
span,
attr_span: self.attr_span,
template: self.template.clone(),
attribute: self.attr_path.clone(),
path: self.attr_path.clone(),
description: self.parsed_description,
reason: AttributeParseErrorReason::ExpectedIntegerLiteral,
suggestions: self.suggestions(),
})
Expand All @@ -457,7 +465,8 @@ impl<'f, 'sess: 'f, S: Stage> AcceptContext<'f, 'sess, S> {
span,
attr_span: self.attr_span,
template: self.template.clone(),
attribute: self.attr_path.clone(),
path: self.attr_path.clone(),
description: self.parsed_description,
reason: AttributeParseErrorReason::ExpectedList,
suggestions: self.suggestions(),
})
Expand All @@ -468,7 +477,8 @@ impl<'f, 'sess: 'f, S: Stage> AcceptContext<'f, 'sess, S> {
span: args_span,
attr_span: self.attr_span,
template: self.template.clone(),
attribute: self.attr_path.clone(),
path: self.attr_path.clone(),
description: self.parsed_description,
reason: AttributeParseErrorReason::ExpectedNoArgs,
suggestions: self.suggestions(),
})
Expand All @@ -480,7 +490,8 @@ impl<'f, 'sess: 'f, S: Stage> AcceptContext<'f, 'sess, S> {
span,
attr_span: self.attr_span,
template: self.template.clone(),
attribute: self.attr_path.clone(),
path: self.attr_path.clone(),
description: self.parsed_description,
reason: AttributeParseErrorReason::ExpectedIdentifier,
suggestions: self.suggestions(),
})
Expand All @@ -493,7 +504,8 @@ impl<'f, 'sess: 'f, S: Stage> AcceptContext<'f, 'sess, S> {
span,
attr_span: self.attr_span,
template: self.template.clone(),
attribute: self.attr_path.clone(),
path: self.attr_path.clone(),
description: self.parsed_description,
reason: AttributeParseErrorReason::ExpectedNameValue(name),
suggestions: self.suggestions(),
})
Expand All @@ -505,7 +517,8 @@ impl<'f, 'sess: 'f, S: Stage> AcceptContext<'f, 'sess, S> {
span,
attr_span: self.attr_span,
template: self.template.clone(),
attribute: self.attr_path.clone(),
path: self.attr_path.clone(),
description: self.parsed_description,
reason: AttributeParseErrorReason::DuplicateKey(key),
suggestions: self.suggestions(),
})
Expand All @@ -518,7 +531,8 @@ impl<'f, 'sess: 'f, S: Stage> AcceptContext<'f, 'sess, S> {
span,
attr_span: self.attr_span,
template: self.template.clone(),
attribute: self.attr_path.clone(),
path: self.attr_path.clone(),
description: self.parsed_description,
reason: AttributeParseErrorReason::UnexpectedLiteral,
suggestions: self.suggestions(),
})
Expand All @@ -529,7 +543,8 @@ impl<'f, 'sess: 'f, S: Stage> AcceptContext<'f, 'sess, S> {
span,
attr_span: self.attr_span,
template: self.template.clone(),
attribute: self.attr_path.clone(),
path: self.attr_path.clone(),
description: self.parsed_description,
reason: AttributeParseErrorReason::ExpectedSingleArgument,
suggestions: self.suggestions(),
})
Expand All @@ -540,7 +555,8 @@ impl<'f, 'sess: 'f, S: Stage> AcceptContext<'f, 'sess, S> {
span,
attr_span: self.attr_span,
template: self.template.clone(),
attribute: self.attr_path.clone(),
path: self.attr_path.clone(),
description: self.parsed_description,
reason: AttributeParseErrorReason::ExpectedAtLeastOneArgument,
suggestions: self.suggestions(),
})
Expand All @@ -556,7 +572,8 @@ impl<'f, 'sess: 'f, S: Stage> AcceptContext<'f, 'sess, S> {
span,
attr_span: self.attr_span,
template: self.template.clone(),
attribute: self.attr_path.clone(),
path: self.attr_path.clone(),
description: self.parsed_description,
reason: AttributeParseErrorReason::ExpectedSpecificArgument {
possibilities,
strings: false,
Expand All @@ -577,7 +594,8 @@ impl<'f, 'sess: 'f, S: Stage> AcceptContext<'f, 'sess, S> {
span,
attr_span: self.attr_span,
template: self.template.clone(),
attribute: self.attr_path.clone(),
path: self.attr_path.clone(),
description: self.parsed_description,
reason: AttributeParseErrorReason::ExpectedSpecificArgument {
possibilities,
strings: false,
Expand All @@ -597,7 +615,8 @@ impl<'f, 'sess: 'f, S: Stage> AcceptContext<'f, 'sess, S> {
span,
attr_span: self.attr_span,
template: self.template.clone(),
attribute: self.attr_path.clone(),
path: self.attr_path.clone(),
description: self.parsed_description,
reason: AttributeParseErrorReason::ExpectedSpecificArgument {
possibilities,
strings: true,
Expand Down
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