Stabilize attributes on closure and method call expressions

compiler/rustc_expand/src/config.rs

@@ -401,9 +401,25 @@ impl<'a> StripUnconfigured<'a> {
         eval_config_entry(self.sess, &cfg)
     }
 
-    /// If attributes are not allowed on expressions, emit an error for `attr`
+    /// Whether `expr` is a closure or method call, possibly parenthesized, on which outer
+    /// attributes are stable.
+    fn is_outer_attr_stable_on_closure_or_method_call_expr(expr: &ast::Expr) -> bool {
+        match &expr.kind {
+            ast::ExprKind::Closure(..) | ast::ExprKind::MethodCall(..) => true,
+            ast::ExprKind::Paren(inner) => {
+                Self::is_outer_attr_stable_on_closure_or_method_call_expr(inner)
+            }
+            _ => false,
+        }
+    }
+
+    /// If attributes are not allowed on `expr`, emit an error for `attr`.
     #[instrument(level = "trace", skip(self))]
-    pub(crate) fn maybe_emit_expr_attr_err(&self, attr: &Attribute) {
+    pub(crate) fn maybe_emit_expr_attr_err(&self, expr: &ast::Expr, attr: &Attribute) {
+        if Self::is_outer_attr_stable_on_closure_or_method_call_expr(expr) {
+            return;
+        }
+
         if self.features.is_some_and(|features| !features.stmt_expr_attributes())
             && !attr.span.allows_unstable(sym::stmt_expr_attributes)
         {
@@ -430,7 +446,7 @@ impl<'a> StripUnconfigured<'a> {
     pub fn configure_expr(&self, expr: &mut ast::Expr, method_receiver: bool) {
         if !method_receiver {
             for attr in expr.attrs.iter() {
-                self.maybe_emit_expr_attr_err(attr);
+                self.maybe_emit_expr_attr_err(expr, attr);
             }
         }
 

compiler/rustc_expand/src/expand.rs

@@ -1252,7 +1252,12 @@ trait InvocationCollectorNode: HasAttrs + HasNodeId + Sized {
     fn flatten_outputs(_outputs: impl Iterator<Item = Self::OutputTy>) -> Self::OutputTy {
         unreachable!()
     }
-    fn pre_flat_map_node_collect_attr(_cfg: &StripUnconfigured<'_>, _attr: &ast::Attribute) {}
+    fn pre_flat_map_node_collect_attr(
+        _cfg: &StripUnconfigured<'_>,
+        _node: &Self,
+        _attr: &ast::Attribute,
+    ) {
+    }
     fn post_flat_map_node_collect_bang(_output: &mut Self::OutputTy, _add_semicolon: AddSemicolon) {
     }
     fn wrap_flat_map_node_walk_flat_map(
@@ -1962,8 +1967,12 @@ impl InvocationCollectorNode for AstNodeWrapper<Box<ast::Expr>, OptExprTag> {
             _ => unreachable!(),
         }
     }
-    fn pre_flat_map_node_collect_attr(cfg: &StripUnconfigured<'_>, attr: &ast::Attribute) {
-        cfg.maybe_emit_expr_attr_err(attr);
+    fn pre_flat_map_node_collect_attr(
+        cfg: &StripUnconfigured<'_>,
+        node: &Self,
+        attr: &ast::Attribute,
+    ) {
+        cfg.maybe_emit_expr_attr_err(&node.wrapped, attr);
     }
     fn as_target(&self) -> Target {
         Target::Expression
@@ -2333,7 +2342,7 @@ impl<'a, 'b> InvocationCollector<'a, 'b> {
                         continue;
                     }
                     _ => {
-                        Node::pre_flat_map_node_collect_attr(&self.cfg(), &attr);
+                        Node::pre_flat_map_node_collect_attr(&self.cfg(), &node, &attr);
                         self.collect_attr((attr, pos, derives), node.to_annotatable(), Node::KIND)
                             .make_ast::<Node>()
                     }
@@ -2554,7 +2563,7 @@ impl<'a, 'b> MutVisitor for InvocationCollector<'a, 'b> {
     fn visit_expr(&mut self, node: &mut ast::Expr) {
         // FIXME: Feature gating is performed inconsistently between `Expr` and `OptExpr`.
         if let Some(attr) = node.attrs.first() {
-            self.cfg().maybe_emit_expr_attr_err(attr);
+            self.cfg().maybe_emit_expr_attr_err(node, attr);
         }
         ensure_sufficient_stack(|| self.visit_node(node))
     }

tests/ui/attributes/attributes-on-closure-and-method-call-cfg-eval.rs

@@ -0,0 +1,16 @@
+//@ check-pass
+
+#![feature(cfg_eval)]
+
+struct Value;
+
+impl Value {
+    fn method(self) -> usize {
+        0
+    }
+}
+
+fn main() {
+    let _ = #[cfg_eval] #[inline] || {};
+    let _ = #[cfg_eval] #[allow(unused)] Value.method();
+}

tests/ui/attributes/attributes-on-method-calls.rs

@@ -0,0 +1,19 @@
+//@ check-pass
+
+struct Value;
+
+impl Value {
+    fn first(self) -> Self {
+        self
+    }
+
+    fn second(self) -> usize {
+        0
+    }
+}
+
+fn main() {
+    let _ = #[allow(unused)] Value.first();
+    let _ = #[allow(unused)] Value.first().second();
+    let _ = #[allow(unused)] (Value.first().second());
+}

tests/ui/attributes/inline-attribute-on-closure.rs

@@ -1,10 +1,10 @@
 //! Regression test for https://github.com/rust-lang/rust/issues/49632
 
 //@ run-pass
-#![feature(stmt_expr_attributes)]
 
 pub fn main() {
     let _x = #[inline(always)] || {};
     let _y = #[inline(never)] || {};
     let _z = #[inline] || {};
+    let _cold = #[cold] || {};
 }

tests/ui/attributes/instrument_fn.rs

@@ -47,5 +47,4 @@ fn instrument_closure() {
     let _x = #[instrument_fn = "on"]
     || {};
     //~^^ ERROR attribute cannot be used on
-    //~^^^ ERROR attributes on expressions are experimental
 }

tests/ui/attributes/instrument_fn.stderr

@@ -8,16 +8,6 @@ LL |         #[instrument_fn = "off"]
    = help: add `#![feature(stmt_expr_attributes)]` to the crate attributes to enable
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
-error[E0658]: attributes on expressions are experimental
-  --> $DIR/instrument_fn.rs:47:14
-   |
-LL |     let _x = #[instrument_fn = "on"]
-   |              ^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #15701 <https://github.com/rust-lang/rust/issues/15701> for more information
-   = help: add `#![feature(stmt_expr_attributes)]` to the crate attributes to enable
-   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
-
 error: `#[instrument_fn]` attribute cannot be used on crates
   --> $DIR/instrument_fn.rs:2:1
    |
@@ -121,7 +111,7 @@ LL |     let _x = #[instrument_fn = "on"]
    |
    = help: `#[instrument_fn]` can be applied to functions and methods
 
-error: aborting due to 13 previous errors
+error: aborting due to 12 previous errors
 
 Some errors have detailed explanations: E0539, E0658, E0805.
 For more information about an error, try `rustc --explain E0539`.

tests/ui/closures/2229_closure_analysis/arrays-completely-captured.rs

@@ -6,9 +6,6 @@ fn main() {
     let mut m = [1, 2, 3, 4, 5];
 
     let mut c = #[rustc_capture_analysis]
-    //~^ ERROR: attributes on expressions are experimental
-    //~| NOTE: see issue #15701 <https://github.com/rust-lang/rust/issues/15701>
-    //~| NOTE: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
     || {
     //~^ ERROR: First Pass analysis includes:
     //~| ERROR: Min Capture analysis includes:

tests/ui/closures/2229_closure_analysis/arrays-completely-captured.stderr

@@ -1,15 +1,5 @@
-error[E0658]: attributes on expressions are experimental
-  --> $DIR/arrays-completely-captured.rs:8:17
-   |
-LL |     let mut c = #[rustc_capture_analysis]
-   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #15701 <https://github.com/rust-lang/rust/issues/15701> for more information
-   = help: add `#![feature(stmt_expr_attributes)]` to the crate attributes to enable
-   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
-
 error: First Pass analysis includes:
-  --> $DIR/arrays-completely-captured.rs:12:5
+  --> $DIR/arrays-completely-captured.rs:9:5
    |
 LL | /     || {
 LL | |
@@ -20,18 +10,18 @@ LL | |     };
    | |_____^
    |
 note: Capturing m[] -> Mutable
-  --> $DIR/arrays-completely-captured.rs:15:9
+  --> $DIR/arrays-completely-captured.rs:12:9
    |
 LL |         m[0] += 10;
    |         ^
 note: Capturing m[] -> Mutable
-  --> $DIR/arrays-completely-captured.rs:18:9
+  --> $DIR/arrays-completely-captured.rs:15:9
    |
 LL |         m[1] += 40;
    |         ^
 
 error: Min Capture analysis includes:
-  --> $DIR/arrays-completely-captured.rs:12:5
+  --> $DIR/arrays-completely-captured.rs:9:5
    |
 LL | /     || {
 LL | |
@@ -42,11 +32,10 @@ LL | |     };
    | |_____^
    |
 note: Min Capture m[] -> Mutable
-  --> $DIR/arrays-completely-captured.rs:15:9
+  --> $DIR/arrays-completely-captured.rs:12:9
    |
 LL |         m[0] += 10;
    |         ^
 
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0658`.

tests/ui/closures/2229_closure_analysis/by_value.rs

@@ -16,9 +16,6 @@ fn big_box() {
     let t = (b, 10);
 
     let c = #[rustc_capture_analysis]
-    //~^ ERROR: attributes on expressions are experimental
-    //~| NOTE: see issue #15701 <https://github.com/rust-lang/rust/issues/15701>
-    //~| NOTE: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
     || {
     //~^ ERROR First Pass analysis includes:
     //~| ERROR Min Capture analysis includes:

tests/ui/closures/2229_closure_analysis/by_value.stderr

@@ -1,15 +1,5 @@
-error[E0658]: attributes on expressions are experimental
-  --> $DIR/by_value.rs:18:13
-   |
-LL |     let c = #[rustc_capture_analysis]
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #15701 <https://github.com/rust-lang/rust/issues/15701> for more information
-   = help: add `#![feature(stmt_expr_attributes)]` to the crate attributes to enable
-   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
-
 error: First Pass analysis includes:
-  --> $DIR/by_value.rs:22:5
+  --> $DIR/by_value.rs:19:5
    |
 LL | /     || {
 LL | |
@@ -20,18 +10,18 @@ LL | |     };
    | |_____^
    |
 note: Capturing t[(0, 0),Deref,(0, 0)] -> ByValue
-  --> $DIR/by_value.rs:25:17
+  --> $DIR/by_value.rs:22:17
    |
 LL |         let p = t.0.0;
    |                 ^^^^^
 note: Capturing t[(1, 0)] -> Immutable
-  --> $DIR/by_value.rs:28:29
+  --> $DIR/by_value.rs:25:29
    |
 LL |         println!("{} {:?}", t.1, p);
    |                             ^^^
 
 error: Min Capture analysis includes:
-  --> $DIR/by_value.rs:22:5
+  --> $DIR/by_value.rs:19:5
    |
 LL | /     || {
 LL | |
@@ -42,16 +32,15 @@ LL | |     };
    | |_____^
    |
 note: Min Capture t[(0, 0)] -> ByValue
-  --> $DIR/by_value.rs:25:17
+  --> $DIR/by_value.rs:22:17
    |
 LL |         let p = t.0.0;
    |                 ^^^^^
 note: Min Capture t[(1, 0)] -> Immutable
-  --> $DIR/by_value.rs:28:29
+  --> $DIR/by_value.rs:25:29
    |
 LL |         println!("{} {:?}", t.1, p);
    |                             ^^^
 
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0658`.

tests/ui/closures/2229_closure_analysis/capture-analysis-1.rs

@@ -13,9 +13,6 @@ fn main() {
     let q = Point { x: 10, y: 10 };
 
     let c = #[rustc_capture_analysis]
-    //~^ ERROR: attributes on expressions are experimental
-    //~| NOTE: see issue #15701 <https://github.com/rust-lang/rust/issues/15701>
-    //~| NOTE: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
     || {
     //~^ ERROR First Pass analysis includes:
     //~| ERROR Min Capture analysis includes:

tests/ui/closures/2229_closure_analysis/capture-analysis-1.stderr

@@ -1,15 +1,5 @@
-error[E0658]: attributes on expressions are experimental
-  --> $DIR/capture-analysis-1.rs:15:13
-   |
-LL |     let c = #[rustc_capture_analysis]
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: see issue #15701 <https://github.com/rust-lang/rust/issues/15701> for more information
-   = help: add `#![feature(stmt_expr_attributes)]` to the crate attributes to enable
-   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
-
 error: First Pass analysis includes:
-  --> $DIR/capture-analysis-1.rs:19:5
+  --> $DIR/capture-analysis-1.rs:16:5
    |
 LL | /     || {
 LL | |
@@ -20,28 +10,28 @@ LL | |     };
    | |_____^
    |
 note: Capturing p[] -> Immutable
-  --> $DIR/capture-analysis-1.rs:22:26
+  --> $DIR/capture-analysis-1.rs:19:26
    |
 LL |         println!("{:?}", p);
    |                          ^
 note: Capturing p[(0, 0)] -> Immutable
-  --> $DIR/capture-analysis-1.rs:25:26
+  --> $DIR/capture-analysis-1.rs:22:26
    |
 LL |         println!("{:?}", p.x);
    |                          ^^^
 note: Capturing q[(0, 0)] -> Immutable
-  --> $DIR/capture-analysis-1.rs:28:26
+  --> $DIR/capture-analysis-1.rs:25:26
    |
 LL |         println!("{:?}", q.x);
    |                          ^^^
 note: Capturing q[] -> Immutable
-  --> $DIR/capture-analysis-1.rs:30:26
+  --> $DIR/capture-analysis-1.rs:27:26
    |
 LL |         println!("{:?}", q);
    |                          ^
 
 error: Min Capture analysis includes:
-  --> $DIR/capture-analysis-1.rs:19:5
+  --> $DIR/capture-analysis-1.rs:16:5
    |
 LL | /     || {
 LL | |
@@ -52,16 +42,15 @@ LL | |     };
    | |_____^
    |
 note: Min Capture p[] -> Immutable
-  --> $DIR/capture-analysis-1.rs:22:26
+  --> $DIR/capture-analysis-1.rs:19:26
    |
 LL |         println!("{:?}", p);
    |                          ^
 note: Min Capture q[] -> Immutable
-  --> $DIR/capture-analysis-1.rs:30:26
+  --> $DIR/capture-analysis-1.rs:27:26
    |
 LL |         println!("{:?}", q);
    |                          ^
 
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0658`.

tests/ui/closures/2229_closure_analysis/capture-analysis-2.rs

@@ -12,9 +12,6 @@ fn main() {
     let mut p = Point { x: String::new(), y: 10 };
 
     let c = #[rustc_capture_analysis]
-    //~^ ERROR: attributes on expressions are experimental
-    //~| NOTE: see issue #15701 <https://github.com/rust-lang/rust/issues/15701>
-    //~| NOTE: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
     || {
     //~^ ERROR First Pass analysis includes:
     //~| ERROR Min Capture analysis includes: