===================================================================
@@ -188,9 +188,9 @@
New_E : Entity_Id) return Boolean;
-- Enforce the rule given in 12.3(18): a private operation in an instance
-- overrides an inherited operation only if the corresponding operation
- -- was overriding in the generic. This can happen for primitive operations
- -- of types derived (in the generic unit) from formal private or formal
- -- derived types.
+ -- was overriding in the generic. This needs to be checked for primitive
+ -- operations of types derived (in the generic unit) from formal private
+ -- or formal derived types.
procedure Make_Inequality_Operator (S : Entity_Id);
-- Create the declaration for an inequality operator that is implicitly
@@ -7844,6 +7844,22 @@
-- If no match found, then the new subprogram does not
-- override in the generic (nor in the instance).
+ -- If the type in question is not abstract, and the subprogram
+ -- is, this will be an error if the new operation is in the
+ -- private part of the instance. Emit a warning now, which will
+ -- make the subsequent error message easier to understand.
+
+ if not Is_Abstract_Type (F_Typ)
+ and then Is_Abstract_Subprogram (Prev_E)
+ and then In_Private_Part (Current_Scope)
+ then
+ Error_Msg_Node_2 := F_Typ;
+ Error_Msg_NE
+ ("private operation& in generic unit does not override " &
+ "any primitive operation of& (RM 12.3 (18))?",
+ New_E, New_E);
+ end if;
+
return True;
end;
end if;
An operation declared in the private part of a generic package is overriding in an instane only if it was overriding in the generic. If an instantiation fails because a non-abstract type has a remaining abstract inherited operation it may be because of a failure to override. This patch produces a warning in this case, that clarifies the resulting error message. compiling inst.ads must yield: inst.ads:5:04: instantiation error at gen.ads:7 inst.ads:5:04: type must be declared abstract or "Change" overridden inst.ads:5:04: "Change" has been inherited at gen.ads:5, instance at line 5 inst.ads:5:04: "Change" has been inherited from subprogram at line 4 inst.ads:5:04: warning: in instantiation at gen.ads:8 inst.ads:5:04: warning: private operation "Change" in generic unit does not override any primitive operation of "Der" (RM 12.3 (18)) --- with P1; with Gen; package Inst is type Act is abstract new P1.Root with null record; procedure Change (Obj : Act) is abstract; package Prob is new Gen (Act); end Inst; --- package P1 is type Root is abstract tagged null record; end P1; --- with P1; generic type Ext is abstract new P1.Root with private; package Gen is type Der is new Ext with private; private type Der is new Ext with null record; procedure Change (Obj : Der); end Gen; Tested on x86_64-pc-linux-gnu, committed on trunk 2012-02-17 Ed Schonberg <schonberg@adacore.com> * sem_ch6.adb (Is_Non_Overriding_Operation): Add warning if the old operation is abstract, the relevant type is not abstract, and the new subprogram fails to override.