To prevent anomalies with enumeration types with holes and scalar types with
complex predicates, the attributes First, Last, and Range cannot be applied to
subtypes with predicates. This rule applies only to scalar types.
The following must compile quietly in Ada2012 mode:
package Pred is
type A is array (Integer range <>) of Integer
with Predicate => (for all J in A'Range =>
(for all K in A'Range =>
(if J /= K then A (J) /= A (K))));
end Pred;
Tested on x86_64-pc-linux-gnu, committed on trunk
2011-08-04 Ed Schonberg <schonb...@adacore.com>
* sem_attr.adb (Bad_Attribute_For_Predicate): flag illegal use of
attribute only if prefix type is scalar.
Index: sem_attr.adb
===================================================================
--- sem_attr.adb (revision 177351)
+++ sem_attr.adb (working copy)
@@ -217,6 +217,8 @@
-- actual, then the message is a warning, and we generate code to raise
-- program error with an appropriate reason. No error message is given
-- for internally generated uses of the attributes.
+ -- The legality rule only applies to scalar types, even though the
+ -- current AI mentions all subtypes.
procedure Check_Array_Or_Scalar_Type;
-- Common procedure used by First, Last, Range attribute to check
@@ -840,7 +842,9 @@
procedure Bad_Attribute_For_Predicate is
begin
- if Comes_From_Source (N) then
+ if Is_Scalar_Type (P_Type)
+ and then Comes_From_Source (N)
+ then
Error_Msg_Name_1 := Aname;
Bad_Predicated_Subtype_Use
("type& has predicates, attribute % not allowed", N, P_Type);
