ambiguous names

[Maxim Reznik <max1@mbank.com.ua>]

Trying to understand paragraph 4.1.3.13 of ARM:

* If the prefix does not denote a package, then it shall be a 
*direct_name or an expanded name, and it shall resolve to denote a 
*program unit (other than a package), the current instance of a type, a 
*block_statement, a loop_statement, or an accept_statement (in the case 
*of an accept_statement or entry_body, no family index is allowed); the 
*expanded name shall occur within the declarative region of this 
*construct. Further, if this construct is a callable construct and the 
*prefix denotes more than one such enclosing callable construct, then 
*the expanded name is ambiguous, independently of the selector_name.

I wroute a program:

procedure A is
    B : Boolean;
    X : Integer;

    procedure A is
       B : Integer;
    begin
       X := A.B;  -- ambiguous ?
    end A;

begin
    null;
end A;

I think there is an ambiguous name A.B in assignment statement.
"A" denotes two procedures and they are callable constructs.
But GNAT doesnt complain.

Could Ada lawyers explain me my fault and/or give me an example
of ambiguity of a prefix?

Please