Rollup merge of #103430 - cjgillot:receiver-attrs, r=petrochenkov

Workaround unstable stmt_expr_attributes for method receiver expressions

Fixes https://github.com/rust-lang/rust/issues/103244

cc ``@Mark-Simulacrum`` ``@ehuss``

src/test/ui/cfg/cfg-method-receiver-ok.rs

@@ -0,0 +1,14 @@
+// check-pass
+
+macro_rules! foo {
+    () => {
+        #[allow(unreachable_patterns)]
+        {
+            123i32
+        }
+    };
+}
+
+fn main() {
+    let _ = foo!().abs();
+}

src/test/ui/cfg/cfg-method-receiver.rs

@@ -7,6 +7,5 @@ macro_rules! cbor_map {
 
 fn main() {
     cbor_map! { #[cfg(test)] 4};
-    //~^ ERROR attributes on expressions are experimental
-    //~| ERROR removing an expression is not supported in this position
+    //~^ ERROR removing an expression is not supported in this position
 }

src/test/ui/cfg/cfg-method-receiver.stderr

@@ -1,12 +1,3 @@
-error[E0658]: attributes on expressions are experimental
-  --> $DIR/cfg-method-receiver.rs:9:17
-   |
-LL |     cbor_map! { #[cfg(test)] 4};
-   |                 ^^^^^^^^^^^^
-   |
-   = 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
-
 error: removing an expression is not supported in this position
   --> $DIR/cfg-method-receiver.rs:9:17
    |
@@ -28,7 +19,6 @@ help: you must specify a concrete type for this numeric value, like `i32`
 LL |     cbor_map! { #[cfg(test)] 4_i32};
    |                              ~~~~~
 
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 
-Some errors have detailed explanations: E0658, E0689.
-For more information about an error, try `rustc --explain E0658`.
+For more information about this error, try `rustc --explain E0689`.