Macros: match const { ... } with expr nonterminal in edition 2024

Co-authored-by: Eric Holk <eric@theincredibleholk.org>
Signed-off-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>

compiler/rustc_parse/src/parser/nonterminal.rs

@@ -3,6 +3,7 @@ use rustc_ast::token::{self, Delimiter, Nonterminal, Nonterminal::*, Nonterminal
 use rustc_ast::HasTokens;
 use rustc_ast_pretty::pprust;
 use rustc_errors::PResult;
+use rustc_span::edition::Edition;
 use rustc_span::symbol::{kw, Ident};
 
 use crate::errors::UnexpectedNonterminal;
@@ -37,13 +38,19 @@ impl<'a> Parser<'a> {
         }
 
         match kind {
-            NonterminalKind::Expr | NonterminalKind::Expr2021 => {
+            NonterminalKind::Expr2021 => {
                 token.can_begin_expr()
                 // This exception is here for backwards compatibility.
                 && !token.is_keyword(kw::Let)
                 // This exception is here for backwards compatibility.
                 && !token.is_keyword(kw::Const)
             }
+            NonterminalKind::Expr => {
+                token.can_begin_expr()
+                // This exception is here for backwards compatibility.
+                && !token.is_keyword(kw::Let)
+                && (token.span.edition() >= Edition::Edition2024 || !token.is_keyword(kw::Const))
+            }
             NonterminalKind::Ty => token.can_begin_type(),
             NonterminalKind::Ident => get_macro_ident(token).is_some(),
             NonterminalKind::Literal => token.can_begin_literal_maybe_minus(),

tests/ui/macros/expr_2021_inline_const.edi2021.stderr

@@ -0,0 +1,32 @@
+error: no rules expected the token `const`
+  --> $DIR/expr_2021_inline_const.rs:21:12
+   |
+LL | macro_rules! m2021 {
+   | ------------------ when calling this macro
+...
+LL |     m2021!(const { 1 });
+   |            ^^^^^ no rules expected this token in macro call
+   |
+note: while trying to match meta-variable `$e:expr_2021`
+  --> $DIR/expr_2021_inline_const.rs:10:6
+   |
+LL |     ($e:expr_2021) => {
+   |      ^^^^^^^^^^^^
+
+error: no rules expected the token `const`
+  --> $DIR/expr_2021_inline_const.rs:22:12
+   |
+LL | macro_rules! m2024 {
+   | ------------------ when calling this macro
+...
+LL |     m2024!(const { 1 });
+   |            ^^^^^ no rules expected this token in macro call
+   |
+note: while trying to match meta-variable `$e:expr`
+  --> $DIR/expr_2021_inline_const.rs:16:6
+   |
+LL |     ($e:expr) => {
+   |      ^^^^^^^
+
+error: aborting due to 2 previous errors
+

tests/ui/macros/expr_2021_inline_const.edi2024.stderr

@@ -0,0 +1,17 @@
+error: no rules expected the token `const`
+  --> $DIR/expr_2021_inline_const.rs:21:12
+   |
+LL | macro_rules! m2021 {
+   | ------------------ when calling this macro
+...
+LL |     m2021!(const { 1 });
+   |            ^^^^^ no rules expected this token in macro call
+   |
+note: while trying to match meta-variable `$e:expr_2021`
+  --> $DIR/expr_2021_inline_const.rs:10:6
+   |
+LL |     ($e:expr_2021) => {
+   |      ^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+

tests/ui/macros/expr_2021_inline_const.rs

@@ -0,0 +1,23 @@
+//@ revisions: edi2021 edi2024
+//@[edi2024]compile-flags: --edition=2024 -Z unstable-options
+//@[edi2021]compile-flags: --edition=2021
+
+// This test ensures that the inline const match only on edition 2024
+#![feature(expr_fragment_specifier_2024)]
+#![allow(incomplete_features)]
+
+macro_rules! m2021 {
+    ($e:expr_2021) => {
+        $e
+    };
+}
+
+macro_rules! m2024 {
+    ($e:expr) => {
+        $e
+    };
+}
+fn main() {
+    m2021!(const { 1 }); //~ ERROR: no rules expected the token `const`
+    m2024!(const { 1 }); //[edi2021]~ ERROR: no rules expected the token `const`
+}