It is illegal to return a dynamically tagged expression
from an expression function that returns a specific type. See
RM-3.9.2(9). This patch fixes a bug that caused the compiler
to fail to detect this illegality.
Tested on x86_64-pc-linux-gnu, committed on trunk
2017-09-12 Bob Duff <[email protected]>
* sem_ch6.adb (Analyze_Expression_Function): Call
Check_Dynamically_Tagged_Expression.
* sem_util.adb (Check_Dynamically_Tagged_Expression): Remove
"and then Is_Tagged_Type (Typ)" because there is an earlier
"Assert (Is_Tagged_Type (Typ))".
Index: sem_util.adb
===================================================================
--- sem_util.adb (revision 251998)
+++ sem_util.adb (working copy)
@@ -2022,7 +2022,6 @@
or else In_Generic_Actual (Expr))
and then (Is_Class_Wide_Type (Etype (Expr))
or else Is_Dynamically_Tagged (Expr))
- and then Is_Tagged_Type (Typ)
and then not Is_Class_Wide_Type (Typ)
then
Error_Msg_N ("dynamically tagged expression not allowed!", Expr);
Index: sem_ch6.adb
===================================================================
--- sem_ch6.adb (revision 251998)
+++ sem_ch6.adb (working copy)
@@ -741,6 +741,21 @@
end;
end if;
+ -- Check incorrect use of dynamically tagged expression. This doesn't
+ -- fall out automatically when analyzing the generated function body,
+ -- because Check_Dynamically_Tagged_Expression deliberately ignores
+ -- nodes that don't come from source.
+
+ if Present (Def_Id)
+ and then Nkind (Def_Id) in N_Has_Etype
+ and then Is_Tagged_Type (Etype (Def_Id))
+ then
+ Check_Dynamically_Tagged_Expression
+ (Expr => Expr,
+ Typ => Etype (Def_Id),
+ Related_Nod => Original_Node (N));
+ end if;
+
-- If the return expression is a static constant, we suppress warning
-- messages on unused formals, which in most cases will be noise.
