Gate const closures even when they appear in macros

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -422,14 +422,6 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
             ast::ExprKind::TryBlock(_) => {
                 gate_feature_post!(&self, try_blocks, e.span, "`try` expression is experimental");
             }
-            ast::ExprKind::Closure(box ast::Closure { constness: ast::Const::Yes(_), .. }) => {
-                gate_feature_post!(
-                    &self,
-                    const_closures,
-                    e.span,
-                    "const closures are experimental"
-                );
-            }
             _ => {}
         }
         visit::walk_expr(self, e)
@@ -592,6 +584,7 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session) {
     gate_all!(associated_const_equality, "associated const equality is incomplete");
     gate_all!(yeet_expr, "`do yeet` expression is experimental");
     gate_all!(dyn_star, "`dyn*` trait objects are experimental");
+    gate_all!(const_closures, "const closures are experimental");
 
     // All uses of `gate_all!` below this point were added in #65742,
     // and subsequently disabled (with the non-early gating readded).

compiler/rustc_parse/src/parser/expr.rs

@@ -2105,7 +2105,7 @@ impl<'a> Parser<'a> {
             ClosureBinder::NotPresent
         };
 
-        let constness = self.parse_closure_constness(Case::Sensitive);
+        let constness = self.parse_closure_constness();
 
         let movability =
             if self.eat_keyword(kw::Static) { Movability::Static } else { Movability::Movable };

compiler/rustc_parse/src/parser/mod.rs

@@ -1196,9 +1196,13 @@ impl<'a> Parser<'a> {
         self.parse_constness_(case, false)
     }
 
-    /// Parses constness for closures
+    /// Parses constness for closures (case sensitive, feature-gated)
-    fn parse_closure_constness(&mut self, case: Case) -> Const {
+    fn parse_closure_constness(&mut self) -> Const {
-        self.parse_constness_(case, true)
+        let constness = self.parse_constness_(Case::Sensitive, true);
+        if let Const::Yes(span) = constness {
+            self.sess.gated_spans.gate(sym::const_closures, span);
+        }
+        constness
     }
 
     fn parse_constness_(&mut self, case: Case, is_closure: bool) -> Const {

tests/ui/rfc-2632-const-trait-impl/gate.rs

@@ -1,5 +1,13 @@
 // gate-test-const_closures
+
 fn main() {
     (const || {})();
     //~^ ERROR: const closures are experimental
 }
+
+macro_rules! e {
+    ($e:expr) => {}
+}
+
+e!((const || {}));
+//~^ ERROR const closures are experimental

tests/ui/rfc-2632-const-trait-impl/gate.stderr

@@ -1,12 +1,21 @@
 error[E0658]: const closures are experimental
-  --> $DIR/gate.rs:3:6
+  --> $DIR/gate.rs:4:6
    |
 LL |     (const || {})();
-   |      ^^^^^^^^^^^
+   |      ^^^^^
    |
    = note: see issue #106003 <https://github.com/rust-lang/rust/issues/106003> for more information
    = help: add `#![feature(const_closures)]` to the crate attributes to enable
 
-error: aborting due to previous error
+error[E0658]: const closures are experimental
+  --> $DIR/gate.rs:12:5
+   |
+LL | e!((const || {}));
+   |     ^^^^^
+   |
+   = note: see issue #106003 <https://github.com/rust-lang/rust/issues/106003> for more information
+   = help: add `#![feature(const_closures)]` to the crate attributes to enable
+
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0658`.