Added stmt_expr_attribute feature gate
@@ -2368,6 +2368,9 @@ The currently implemented features of the reference compiler are:
influence type inference.
* - `braced_empty_structs` - Allows use of empty structs and enum variants with braces.
+* - `stmt_expr_attributes` - Allows attributes on expressions and
+ non-item statements.
+
If a feature is promoted to a language feature, then all existing programs will
start to receive compilation warnings about `#![feature]` directives which enabled
the new feature (because the directive is no longer necessary). However, if a
