Port #[needs_allocator] to attribute parser

compiler/rustc_attr_parsing/src/attributes/link_attrs.rs

@@ -658,3 +658,12 @@ impl<S: Stage> SingleAttributeParser<S> for LinkageParser {
         Some(AttributeKind::Linkage(linkage, cx.attr_span))
     }
 }
+
+pub(crate) struct NeedsAllocatorParser;
+
+impl<S: Stage> NoArgsAttributeParser<S> for NeedsAllocatorParser {
+    const PATH: &[Symbol] = &[sym::needs_allocator];
+    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Error;
+    const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(&[Allow(Target::Crate)]);
+    const CREATE: fn(Span) -> AttributeKind = |_| AttributeKind::NeedsAllocator;
+}

compiler/rustc_attr_parsing/src/context.rs

@@ -41,7 +41,7 @@ use crate::attributes::inline::{InlineParser, RustcForceInlineParser};
 use crate::attributes::instruction_set::InstructionSetParser;
 use crate::attributes::link_attrs::{
     ExportStableParser, FfiConstParser, FfiPureParser, LinkNameParser, LinkOrdinalParser,
-    LinkParser, LinkSectionParser, LinkageParser, StdInternalSymbolParser,
+    LinkParser, LinkSectionParser, LinkageParser, NeedsAllocatorParser, StdInternalSymbolParser,
 };
 use crate::attributes::lint_helpers::{
     AsPtrParser, AutomaticallyDerivedParser, PassByValueParser, PubTransparentParser,
@@ -259,6 +259,7 @@ attribute_parsers!(
         Single<WithoutArgs<MacroEscapeParser>>,
         Single<WithoutArgs<MarkerParser>>,
         Single<WithoutArgs<MayDangleParser>>,
+        Single<WithoutArgs<NeedsAllocatorParser>>,
         Single<WithoutArgs<NoCoreParser>>,
         Single<WithoutArgs<NoImplicitPreludeParser>>,
         Single<WithoutArgs<NoLinkParser>>,

compiler/rustc_hir/src/attrs/data_structures.rs

@@ -840,6 +840,9 @@ pub enum AttributeKind {
     /// Represents `#[naked]`
     Naked(Span),
 
+    /// Represents `#[needs_allocator]`
+    NeedsAllocator,
+
     /// Represents `#[no_core]`
     NoCore(Span),
 

compiler/rustc_hir/src/attrs/encode_cross_crate.rs

@@ -75,6 +75,7 @@ impl AttributeKind {
             MustNotSupend { .. } => Yes,
             MustUse { .. } => Yes,
             Naked(..) => No,
+            NeedsAllocator => No,
             NoCore(..) => No,
             NoImplicitPrelude(..) => No,
             NoLink => No,

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -742,7 +742,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
                 proc_macro_data,
                 debugger_visualizers,
                 compiler_builtins: ast::attr::contains_name(attrs, sym::compiler_builtins),
-                needs_allocator: ast::attr::contains_name(attrs, sym::needs_allocator),
+                needs_allocator: find_attr!(attrs, AttributeKind::NeedsAllocator),
                 needs_panic_runtime: ast::attr::contains_name(attrs, sym::needs_panic_runtime),
                 no_builtins: ast::attr::contains_name(attrs, sym::no_builtins),
                 panic_runtime: ast::attr::contains_name(attrs, sym::panic_runtime),

compiler/rustc_passes/src/check_attr.rs

@@ -315,6 +315,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                     | AttributeKind::RustcDumpPredicates
                     | AttributeKind::RustcDumpDefParents
                     | AttributeKind::RustcDumpVtable(..)
+                    | AttributeKind::NeedsAllocator
                 ) => { /* do nothing  */ }
                 Attribute::Unparsed(attr_item) => {
                     style = Some(attr_item.style);
@@ -346,7 +347,6 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                             | sym::prelude_import
                             | sym::panic_handler
                             | sym::lang
-                            | sym::needs_allocator
                             | sym::default_lib_allocator
                             | sym::rustc_diagnostic_item
                             | sym::rustc_no_mir_inline