For practitioners of other languages it is useful to indicate that an access
value is not a legal operand of predefined concatenation.
Compiling foo.adb must yield:
foo.adb:5:33: invalid operand types for operator "&"
foo.adb:5:33: left operand is access type
foo.adb:6:35: invalid operand types for operator "&"
foo.adb:6:35: right operand is access type
with Ada.Text_IO; use Ada.Text_IO;
procedure Foo is
Prefix : access String := new String'("Hello ");
Suffix : String := Prefix & "world!";
Backwards : String := "world!" & Prefix;
begin
Put_Line (Suffix);
end Foo;
Tested on x86_64-pc-linux-gnu, committed on trunk
2014-01-22 Ed Schonberg <schonb...@adacore.com>
* sem_ch4.adb (Operator_Check): Improve error message when an
operand of concatenation is an access type.
Index: sem_ch4.adb
===================================================================
--- sem_ch4.adb (revision 206918)
+++ sem_ch4.adb (working copy)
@@ -6151,7 +6151,8 @@
-- In an instance a generic actual may be a numeric type even if
-- the formal in the generic unit was not. In that case, the
-- predefined operator was not a possible interpretation in the
- -- generic, and cannot be one in the instance.
+ -- generic, and cannot be one in the instance, unless the operator
+ -- is an actual of an instance.
if In_Instance
and then
@@ -6576,6 +6577,17 @@
if Nkind (N) /= N_Op_Concat then
Error_Msg_NE ("\left operand has}!", N, Etype (L));
Error_Msg_NE ("\right operand has}!", N, Etype (R));
+
+ -- For concatenation operators it is more difficult to
+ -- determine which is the wrong operand. It is worth
+ -- flagging explicitly an access type, for those who
+ -- might think that a dereference happens here.
+
+ elsif Is_Access_Type (Etype (L)) then
+ Error_Msg_N ("\left operand is access type", N);
+
+ elsif Is_Access_Type (Etype (R)) then
+ Error_Msg_N ("\right operand is access type", N);
end if;
end if;
end if;
