mention invoking method in top-level statement situation

Author: RexJaeschke

standard/attributes.md

@@ -847,7 +847,7 @@ The file path may be affected by `#line` directives ([§6.5.8](lexical-structure
 
 The attribute `System.Runtime.CompilerServices.CallerMemberNameAttribute` is allowed on optional parameters when there is a standard implicit conversion ([§10.4.2](conversions.md#1042-standard-implicit-conversions)) from `string` to the parameter’s type.
 
-If a function invocation from a location within the body of a function member or within an attribute applied to the function member itself or its return type, parameters or type parameters in source code omits an optional parameter with the `CallerMemberNameAttribute`, then a string literal representing the name of that member is used as an argument to the invocation instead of the default parameter value.
+If a function invocation from a location within the body of a function member or within an attribute applied to the function member itself or its return type, parameters or type parameters in source code omits an optional parameter with the `CallerMemberNameAttribute`, then a string literal representing the name of that member is used as an argument to the invocation instead of the default parameter value. (In the case of a function invocation from a top-level statement (§top-level-statements), the member name is that generated by the implementation.)
 
 For invocations that occur within generic methods, only the method name itself is used, without the type parameter list.