Remove #[rustc_macro_edition_2021].

It was only temporarily used by pin!(), which no longer needs it.

compiler/rustc_attr_data_structures/src/attributes.rs

@@ -191,7 +191,6 @@ pub enum AttributeKind {
     },
     MacroTransparency(Transparency),
     Repr(ThinVec<(ReprAttr, Span)>),
-    RustcMacroEdition2021,
     Stability {
         stability: Stability,
         /// Span of the `#[stable(...)]` or `#[unstable(...)]` attribute

compiler/rustc_attr_parsing/src/attributes/mod.rs

@@ -28,7 +28,6 @@ pub(crate) mod cfg;
 pub(crate) mod confusables;
 pub(crate) mod deprecation;
 pub(crate) mod repr;
-pub(crate) mod rustc;
 pub(crate) mod stability;
 pub(crate) mod transparency;
 pub(crate) mod util;

compiler/rustc_attr_parsing/src/attributes/rustc.rs

@@ -1,19 +0,0 @@
-use rustc_attr_data_structures::AttributeKind;
-use rustc_span::sym;
-
-use super::{AcceptContext, SingleAttributeParser};
-use crate::parser::ArgParser;
-
-pub(crate) struct RustcMacroEdition2021Parser;
-
-// FIXME(jdonszelmann): make these proper diagnostics
-impl SingleAttributeParser for RustcMacroEdition2021Parser {
-    const PATH: &'static [rustc_span::Symbol] = &[sym::rustc_macro_edition_2021];
-
-    fn on_duplicate(_cx: &crate::context::AcceptContext<'_>, _first_span: rustc_span::Span) {}
-
-    fn convert(_cx: &AcceptContext<'_>, args: &ArgParser<'_>) -> Option<AttributeKind> {
-        assert!(args.no_args());
-        Some(AttributeKind::RustcMacroEdition2021)
-    }
-}

compiler/rustc_attr_parsing/src/context.rs

@@ -15,7 +15,6 @@ use crate::attributes::allow_unstable::{AllowConstFnUnstableParser, AllowInterna
 use crate::attributes::confusables::ConfusablesParser;
 use crate::attributes::deprecation::DeprecationParser;
 use crate::attributes::repr::ReprParser;
-use crate::attributes::rustc::RustcMacroEdition2021Parser;
 use crate::attributes::stability::{
     BodyStabilityParser, ConstStabilityIndirectParser, ConstStabilityParser, StabilityParser,
 };
@@ -77,7 +76,6 @@ attribute_groups!(
         // tidy-alphabetical-start
         Single<ConstStabilityIndirectParser>,
         Single<DeprecationParser>,
-        Single<RustcMacroEdition2021Parser>,
         Single<TransparencyParser>,
         // tidy-alphabetical-end
     ];

compiler/rustc_feature/src/builtin_attrs.rs

@@ -676,14 +676,6 @@ pub static BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
         "`rustc_never_type_options` is used to experiment with never type fallback and work on \
          never type stabilization, and will never be stable"
     ),
-    rustc_attr!(
-        rustc_macro_edition_2021,
-        Normal,
-        template!(Word),
-        ErrorFollowing,
-        EncodeCrossCrate::No,
-        "makes spans in this macro edition 2021"
-    ),
 
     // ==========================================================================
     // Internal attributes: Runtime related:

compiler/rustc_resolve/src/macros.rs

@@ -8,7 +8,7 @@ use std::sync::Arc;
 use rustc_ast::expand::StrippedCfgItem;
 use rustc_ast::{self as ast, Crate, NodeId, attr};
 use rustc_ast_pretty::pprust;
-use rustc_attr_parsing::{AttributeKind, StabilityLevel, find_attr};
+use rustc_attr_parsing::StabilityLevel;
 use rustc_data_structures::intern::Interned;
 use rustc_errors::{Applicability, DiagCtxtHandle, StashKey};
 use rustc_expand::base::{
@@ -1128,13 +1128,6 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             edition,
         );
 
-        // The #[rustc_macro_edition_2021] attribute is used by the pin!() macro
-        // as a temporary workaround for a regression in expressiveness in Rust 2024.
-        // See https://github.com/rust-lang/rust/issues/138718.
-        if find_attr!(attrs.iter(), AttributeKind::RustcMacroEdition2021) {
-            ext.edition = Edition::Edition2021;
-        }
-
         if let Some(builtin_name) = ext.builtin_name {
             // The macro was marked with `#[rustc_builtin_macro]`.
             if let Some(builtin_ext_kind) = self.builtin_macros.get(&builtin_name) {

compiler/rustc_span/src/symbol.rs

@@ -1824,7 +1824,6 @@ symbols! {
         rustc_lint_opt_ty,
         rustc_lint_query_instability,
         rustc_lint_untracked_query_information,
-        rustc_macro_edition_2021,
         rustc_macro_transparency,
         rustc_main,
         rustc_mir,