===================================================================
@@ -9086,6 +9086,21 @@
end loop;
end;
end if;
+
+ -- RM 4.5.2 (28.1/3) specifies that for types other than records or
+ -- limited types, evaluation of a membership test uses the predefined
+ -- equality for the type. This may be confusing to users, and the
+ -- following warning appears useful for the most common case.
+
+ if Is_Scalar_Type (Ltyp)
+ and then Present (Get_User_Defined_Eq (Ltyp))
+ then
+ Error_Msg_NE
+ ("membership test on& uses predefined equality?", N, Ltyp);
+ Error_Msg_N
+ ("\even if user-defined equality exists (RM 4.5.2 (28.1/3)?", N);
+ end if;
+
end Resolve_Set_Membership;
-- Start of processing for Resolve_Membership_Op
RM 4.5.3 (28) specifies that (except for records and limited types) a membership operation uses the predefined equality, regardless of whether user-defined equality for the type is available. This can be confusing and deserves a new warning. Compiling code.adb must yield: code.adb:19:42: warning: membership test on "Var" uses predefined equality code.adb:19:42: warning: even if user-defined equality exists (RM 4.5.2 (28.1/3) -- with Ada.Characters.Handling; with Ada.Text_IO; use Ada.Text_IO; procedure Code is type Var is new Character; function "=" (C1, C2 : Var) return Boolean; function "=" (C1, C2 : Var) return Boolean is use Ada.Characters.Handling; begin return To_Lower (Character (C1)) = To_Lower (Character (C2)); end "="; V : Var := 'A'; begin Put_Line ("equal " & Boolean'Image (V = 'a')); Put_Line ("in " & Boolean'Image (V in 'a' | 'o')); end Code; Tested on x86_64-pc-linux-gnu, committed on trunk 2017-12-15 Ed Schonberg <schonberg@adacore.com> * sem_res.adb (Resolve_Membership_Op): Add warning on a membership operation on a scalar type for which there is a user-defined equality operator.