From 0db2eb7734633fe55dacbb05dbc677a079301cab Mon Sep 17 00:00:00 2001
From: Jana Dönszelmann <jana@donsz.nl>
Date: Sun, 24 Aug 2025 11:15:09 +0200
Subject: port `#[no_std]` to the new attribute parsing infrastructure

---
 compiler/rustc_attr_parsing/src/attributes/crate_level.rs | 11 +++++++++++
 compiler/rustc_attr_parsing/src/context.rs                |  3 ++-
 compiler/rustc_hir/src/attrs/data_structures.rs           |  3 +++
 compiler/rustc_hir/src/attrs/encode_cross_crate.rs        |  3 ++-
 compiler/rustc_passes/src/check_attr.rs                   |  1 +
 5 files changed, 19 insertions(+), 2 deletions(-)

(limited to 'compiler')

diff --git a/compiler/rustc_attr_parsing/src/attributes/crate_level.rs b/compiler/rustc_attr_parsing/src/attributes/crate_level.rs
index d2e28ed97aa..3ec847bcaae 100644
--- a/compiler/rustc_attr_parsing/src/attributes/crate_level.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/crate_level.rs
@@ -188,3 +188,14 @@ impl<S: Stage> NoArgsAttributeParser<S> for NoCoreParser {
     const CREATE: fn(Span) -> AttributeKind = AttributeKind::NoCore;
     const TYPE: AttributeType = AttributeType::CrateLevel;
 }
+
+pub(crate) struct NoStdParser;
+impl<S: Stage> NoArgsAttributeParser<S> for NoStdParser {
+    const PATH: &[Symbol] = &[sym::no_std];
+    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Warn;
+    // FIXME: recursion limit is allowed on all targets and ignored,
+    //        even though it should only be valid on crates of course
+    const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(ALL_TARGETS);
+    const CREATE: fn(Span) -> AttributeKind = AttributeKind::NoStd;
+    const TYPE: AttributeType = AttributeType::CrateLevel;
+}
diff --git a/compiler/rustc_attr_parsing/src/context.rs b/compiler/rustc_attr_parsing/src/context.rs
index 3d532d432b5..2e6d840ab51 100644
--- a/compiler/rustc_attr_parsing/src/context.rs
+++ b/compiler/rustc_attr_parsing/src/context.rs
@@ -25,7 +25,7 @@ use crate::attributes::codegen_attrs::{
 };
 use crate::attributes::confusables::ConfusablesParser;
 use crate::attributes::crate_level::{
-    CrateNameParser, MoveSizeLimitParser, NoCoreParser, PatternComplexityLimitParser,
+    CrateNameParser, MoveSizeLimitParser, NoCoreParser, NoStdParser, PatternComplexityLimitParser,
     RecursionLimitParser, TypeLengthLimitParser,
 };
 use crate::attributes::deprecation::DeprecationParser;
@@ -225,6 +225,7 @@ attribute_parsers!(
         Single<WithoutArgs<NoCoreParser>>,
         Single<WithoutArgs<NoImplicitPreludeParser>>,
         Single<WithoutArgs<NoMangleParser>>,
+        Single<WithoutArgs<NoStdParser>>,
         Single<WithoutArgs<NonExhaustiveParser>>,
         Single<WithoutArgs<ParenSugarParser>>,
         Single<WithoutArgs<PassByValueParser>>,
diff --git a/compiler/rustc_hir/src/attrs/data_structures.rs b/compiler/rustc_hir/src/attrs/data_structures.rs
index c2a3844af02..ea11a99efbc 100644
--- a/compiler/rustc_hir/src/attrs/data_structures.rs
+++ b/compiler/rustc_hir/src/attrs/data_structures.rs
@@ -588,6 +588,9 @@ pub enum AttributeKind {
     /// Represents `#[no_mangle]`
     NoMangle(Span),
 
+    /// Represents `#[no_std]`
+    NoStd(Span),
+
     /// Represents `#[non_exhaustive]`
     NonExhaustive(Span),
 
diff --git a/compiler/rustc_hir/src/attrs/encode_cross_crate.rs b/compiler/rustc_hir/src/attrs/encode_cross_crate.rs
index d46e8abf937..55521c15854 100644
--- a/compiler/rustc_hir/src/attrs/encode_cross_crate.rs
+++ b/compiler/rustc_hir/src/attrs/encode_cross_crate.rs
@@ -66,7 +66,8 @@ impl AttributeKind {
             Naked(..) => No,
             NoCore(..) => No,
             NoImplicitPrelude(..) => No,
-            NoMangle(..) => Yes,      // Needed for rustdoc
+            NoMangle(..) => Yes, // Needed for rustdoc
+            NoStd(..) => No,
             NonExhaustive(..) => Yes, // Needed for rustdoc
             Optimize(..) => No,
             ParenSugar(..) => No,
diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs
index cecc8b7fa6b..3b744acbca6 100644
--- a/compiler/rustc_passes/src/check_attr.rs
+++ b/compiler/rustc_passes/src/check_attr.rs
@@ -275,6 +275,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                     | AttributeKind::TypeLengthLimit { .. }
                     | AttributeKind::PatternComplexityLimit { .. }
                     | AttributeKind::NoCore { .. }
+                    | AttributeKind::NoStd { .. }
                 ) => { /* do nothing  */ }
                 Attribute::Unparsed(attr_item) => {
                     style = Some(attr_item.style);
-- 
cgit 1.4.1-3-g733a5