This patch adds a clarifying message info when subtype conformance fails, due
to a missing null exclusion indicatar in a formal that must match a controlling
access formal. This Ada 2005 rule was checked partially in the context of
subprogram renamings but not for 'Access attribute references.
Compiling alpha.adb in gnat05 mode must be rejected with:
alpha.adb:6:19: not subtype conformant with declaration at beta.ads:3
alpha.adb:6:19: controlling formal "Ref" of "Updated" excludes null,
declaration must exclude null as well
---
with Beta;
package Alpha is
type Object is tagged limited null record;
procedure Start;
procedure Updated (Ref : access Object) is null;
end Alpha;
---
package body Alpha is
procedure Start is
begin
Beta.Set (Updated'Access);
end Start;
end Alpha;
---
limited with Alpha;
package Beta is
type Callback is access procedure (Ref : access Alpha.Object);
procedure Set (Proc : in Callback) is null;
end Beta;
Tested on x86_64-pc-linux-gnu, committed on trunk
2012-10-03 Ed Schonberg <[email protected]>
* sem_ch6.adb (Check_Conformance): Additional info when subtype
conformance fails, due to a missing null exclusion indicatar in
a formal that must match a controlling access formal.
Index: sem_ch6.adb
===================================================================
--- sem_ch6.adb (revision 192025)
+++ sem_ch6.adb (working copy)
@@ -5756,14 +5756,31 @@
declare
TSS_Name : constant TSS_Name_Type := Get_TSS_Name (New_Id);
+
begin
if TSS_Name /= TSS_Stream_Read
and then TSS_Name /= TSS_Stream_Write
and then TSS_Name /= TSS_Stream_Input
and then TSS_Name /= TSS_Stream_Output
then
- Conformance_Error
- ("\type of & does not match!", New_Formal);
+ -- Here we have a definite conformance error. It is worth
+ -- special casesing the error message for the case of a
+ -- controlling formal (which excludes null).
+
+ if Is_Controlling_Formal (New_Formal) then
+ Error_Msg_Node_2 := Scope (New_Formal);
+ Conformance_Error
+ ("\controlling formal& of& excludes null, "
+ & "declaration must exclude null as well",
+ New_Formal);
+
+ -- Normal case (couldn't we give more detail here???)
+
+ else
+ Conformance_Error
+ ("\type of & does not match!", New_Formal);
+ end if;
+
return;
end if;
end;
