[Ada] Reporting complex ambiguities

[Arnaud Charlet <charlet at adacore dot com>]

This patch diagnoses properly ambiguous procedure calls written in prefixed
notation, when the prefix is itself an overloaded function call.

Compiling test1.adb must yield:

test1.adb:11:26: ambiguous call to "Get"
test1.adb:11:26: interpretation (inherited) at objs.ads:23
test1.adb:11:26: interpretation at objs.ads:27
test1.adb:11:30: ambiguous expression (cannot resolve "Op")
test1.adb:11:30: possible interpretation at objs.ads:6
test1.adb:11:30: possible interpretation at objs.ads:21

---
with Objs;
procedure Test1 is
   My_Base_Ptr_Wrapper    : Objs.p1.Base_Ptr_Wrapper;
   My_Derived_Ptr_Wrapper : Objs.p2.Derived_Ptr_Wrapper;

begin
   My_Base_Ptr_Wrapper.Base_Obj_Ptr := new Objs.p2.Derived_Obj;
   My_Derived_Ptr_Wrapper.Base_Obj_Ptr := new Objs.p2.Derived_Obj;
   My_Derived_Ptr_Wrapper.Derived_Obj_Ptr := new Objs.p2.Derived_Obj;

   My_Derived_Ptr_Wrapper.Get.Op;     -- (2)   --  Ambiguous
end;
---
package Objs is
   package p1 is
      type Base_Obj is tagged null record;
      type Base_Obj_Class_Access is access all Base_Obj'Class;

      procedure Op (Self : in Base_Obj);

      type Base_Ptr_Wrapper is tagged record
         Base_Obj_Ptr : Base_Obj_Class_Access;
      end record;

      function Get (Self : in Base_Ptr_Wrapper) return access Base_Obj'Class;

   end p1;

   package p2 is
      type Derived_Obj is new p1.Base_Obj with null record;
      type Derived_Obj_Class_Access is access all Derived_Obj'Class;

      overriding
      procedure Op (Self : in Derived_Obj);

      type Derived_Ptr_Wrapper is new p1.Base_Ptr_Wrapper with record
         Derived_Obj_Ptr : Derived_Obj_Class_Access;
      end record;

      function Get
         (Self : in Derived_Ptr_Wrapper) return access Derived_Obj'Class;
   end p2;
end;

Tested on x86_64-pc-linux-gnu, committed on trunk

2010-06-14  Ed Schonberg  <schonberg@adacore.com>

	* sem_ch4.adb (Analyze_One_Call): If the call has been rewritten from a
	prefixed form, do not re-analyze first actual, which may need an
	implicit dereference.
	* sem_ch6.adb (Analyze_Procedure_Call): If the call is given in
	prefixed notation, the analysis will rewrite the node, and possible
	errors appear in the rewritten name of the node.
	* sem_res.adb: If a call is ambiguous because its first parameter is
	an overloaded call, report list of candidates, to clarify ambiguity of
	enclosing call.

Attachment: difs
Description: Text document