[Ada] Spurious error on overriding controlled primitive

2019-12-13  Justin Squirek  <squirek@adacore.com>

gcc/ada/

	* sem_ch6.adb (Check_Overriding_Indicator): Modify condition to
	take into account the modification of the Is_Hidden flag within
	generic instances.
	(Verify_Overriding_Indicator): Add an exception for controlled
	primitives within an instance.

From-SVN: r279340

2 files changed, 31 insertions, 6 deletions

diff --git a/gcc/ada/ChangeLog b/gcc/ada/ChangeLog
index 1c5d5bc..1941a3d 100644
--- a/gcc/ada/ChangeLog
+++ b/gcc/ada/ChangeLog
@@ -1,3 +1,11 @@
+2019-12-13  Justin Squirek  <squirek@adacore.com>
+
+	* sem_ch6.adb (Check_Overriding_Indicator): Modify condition to
+	take into account the modification of the Is_Hidden flag within
+	generic instances.
+	(Verify_Overriding_Indicator): Add an exception for controlled
+	primitives within an instance.
+
 2019-12-13  Ed Schonberg  <schonberg@adacore.com>
 
 	* sinfo.ads, sinfo.adb (Aspect_On_Partial_View,
diff --git a/gcc/ada/sem_ch6.adb b/gcc/ada/sem_ch6.adb
index 988edc6..386332c 100644
--- a/gcc/ada/sem_ch6.adb
+++ b/gcc/ada/sem_ch6.adb
@@ -3304,7 +3304,18 @@ package body Sem_Ch6 is
             then
                null;
 
-            elsif not Present (Overridden_Operation (Spec_Id)) then
+            --  Overridden controlled primitives may have had their
+            --  Overridden_Operation field cleared according to the setting of
+            --  the Is_Hidden flag. An issue arises, however, when analyzing
+            --  an instance that may have manipulated the flag during
+            --  expansion. As a result, we add an exception for this case.
+
+            elsif not Present (Overridden_Operation (Spec_Id))
+              and then not (Nam_In (Chars (Spec_Id), Name_Adjust,
+                                                     Name_Finalize,
+                                                     Name_Initialize)
+                             and then In_Instance)
+            then
                Error_Msg_NE
                  ("subprogram& is not overriding", Body_Spec, Spec_Id);
 
@@ -6427,13 +6438,18 @@ package body Sem_Ch6 is
 
       --  If there is an overridden subprogram, then check that there is no
       --  "not overriding" indicator, and mark the subprogram as overriding.
+
       --  This is not done if the overridden subprogram is marked as hidden,
       --  which can occur for the case of inherited controlled operations
       --  (see Derive_Subprogram), unless the inherited subprogram's parent
-      --  subprogram is not itself hidden. (Note: This condition could probably
-      --  be simplified, leaving out the testing for the specific controlled
-      --  cases, but it seems safer and clearer this way, and echoes similar
-      --  special-case tests of this kind in other places.)
+      --  subprogram is not itself hidden or we are within a generic instance,
+      --  in which case the hidden flag may have been modified for the
+      --  expansion of the instance.
+
+      --  (Note: This condition could probably be simplified, leaving out the
+      --  testing for the specific controlled cases, but it seems safer and
+      --  clearer this way, and echoes similar special-case tests of this
+      --  kind in other places.)
 
       if Present (Overridden_Subp)
         and then (not Is_Hidden (Overridden_Subp)
@@ -6442,7 +6458,8 @@ package body Sem_Ch6 is
                                                        Name_Adjust,
                                                        Name_Finalize)
                       and then Present (Alias (Overridden_Subp))
-                      and then not Is_Hidden (Alias (Overridden_Subp))))
+                      and then (not Is_Hidden (Alias (Overridden_Subp))
+                                 or else In_Instance)))
       then
          if Must_Not_Override (Spec) then
             Error_Msg_Sloc := Sloc (Overridden_Subp);