From e7fea8c7e63cd60aa583e6ee761716bef9a7cc1a Mon Sep 17 00:00:00 2001
From: Deadbeef <ent3rm4n@gmail.com>
Date: Wed, 21 Dec 2022 14:51:02 +0000
Subject: [PATCH] gate const closures

---
 compiler/rustc_ast_passes/src/feature_gate.rs        |  8 ++++++++
 compiler/rustc_feature/src/active.rs                 |  4 +++-
 compiler/rustc_span/src/symbol.rs                    |  1 +
 .../rfc-2632-const-trait-impl/const_closures/gate.rs |  4 ++++
 .../const_closures/gate.stderr                       | 12 ++++++++++++
 5 files changed, 28 insertions(+), 1 deletion(-)
 create mode 100644 src/test/ui/rfc-2632-const-trait-impl/const_closures/gate.rs
 create mode 100644 src/test/ui/rfc-2632-const-trait-impl/const_closures/gate.stderr

diff --git a/compiler/rustc_ast_passes/src/feature_gate.rs b/compiler/rustc_ast_passes/src/feature_gate.rs
index 039338f543c..89ba6f936d1 100644
--- a/compiler/rustc_ast_passes/src/feature_gate.rs
+++ b/compiler/rustc_ast_passes/src/feature_gate.rs
@@ -385,6 +385,14 @@ fn visit_expr(&mut self, e: &'a ast::Expr) {
             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)
diff --git a/compiler/rustc_feature/src/active.rs b/compiler/rustc_feature/src/active.rs
index 691c0955cad..d6eda08f662 100644
--- a/compiler/rustc_feature/src/active.rs
+++ b/compiler/rustc_feature/src/active.rs
@@ -342,7 +342,9 @@ pub fn set(&self, features: &mut Features, span: Span) {
     (active, collapse_debuginfo, "1.65.0", Some(100758), None),
     /// Allows `async {}` expressions in const contexts.
     (active, const_async_blocks, "1.53.0", Some(85368), None),
-    // Allows limiting the evaluation steps of const expressions
+    /// Allows `const || {}` closures in const contexts.
+    (incomplete, const_closures, "CURRENT_RUSTC_VERSION", Some(106003), None),
+    /// Allows limiting the evaluation steps of const expressions
     (active, const_eval_limit, "1.43.0", Some(67217), None),
     /// Allows the definition of `const extern fn` and `const unsafe extern fn`.
     (active, const_extern_fn, "1.40.0", Some(64926), None),
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index fbb12701d96..706002f79b1 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -498,6 +498,7 @@
         console,
         const_allocate,
         const_async_blocks,
+        const_closures,
         const_compare_raw_pointers,
         const_constructor,
         const_deallocate,
diff --git a/src/test/ui/rfc-2632-const-trait-impl/const_closures/gate.rs b/src/test/ui/rfc-2632-const-trait-impl/const_closures/gate.rs
new file mode 100644
index 00000000000..89551121ad2
--- /dev/null
+++ b/src/test/ui/rfc-2632-const-trait-impl/const_closures/gate.rs
@@ -0,0 +1,4 @@
+fn main() {
+    (const || {})();
+    //~^ ERROR: const closures are experimental
+}
diff --git a/src/test/ui/rfc-2632-const-trait-impl/const_closures/gate.stderr b/src/test/ui/rfc-2632-const-trait-impl/const_closures/gate.stderr
new file mode 100644
index 00000000000..94a7fe9e62c
--- /dev/null
+++ b/src/test/ui/rfc-2632-const-trait-impl/const_closures/gate.stderr
@@ -0,0 +1,12 @@
+error[E0658]: const closures are experimental
+  --> $DIR/gate.rs:2:6
+   |
+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
+
+For more information about this error, try `rustc --explain E0658`.