[Ada] New No_Local_Tagged_Types restriction

Add new configuration restriction No_Local_Tagged_Types. This new
restriction ensures at compile time that all tagged types are only
declared at the library level.

gcc/ada/

	* libgnat/s-rident.ads (Restriction_Id): Add
	No_Local_Tagged_Types, update comment for adding new GNAT
	specific restriction.
	* restrict.ads (Implementation_Restriction): Add
	No_Local_Tagged_Types.
	* sem_ch3.adb (Analyze_Full_Type_Declaration): Add check for
	tagged type at library level.
	* doc/gnat_rm/standard_and_implementation_defined_restrictions.rst:
	Add No_Local_Tagged_Types description.
	* gnat_rm.texi: Regenerate.

gcc/ada/doc/gnat_rm/standard_and_implementation_defined_restrictions.rst

@@ -492,6 +492,13 @@ No_Local_Protected_Objects
 [RM D.7] This restriction ensures at compile time that protected objects are
 only declared at the library level.
 
+No_Local_Tagged_Types
+---------------------
+.. index:: No_Local_Tagged_Types
+
+[GNAT] This restriction ensures at compile time that tagged types are only
+declared at the library level.
+
 No_Local_Timing_Events
 ----------------------
 .. index:: No_Local_Timing_Events

gcc/ada/libgnat/s-rident.ads

@@ -81,7 +81,8 @@ package System.Rident is
 
    --  To add a new restriction identifier, add an entry with the name to be
    --  used in the pragma, and add calls to the Restrict.Check_Restriction
-   --  routine as appropriate.
+   --  routine as appropriate. If the new restriction is GNAT specific, also
+   --  add an entry in Restrict.Implementation_Restriction (restrict.ads).
 
    type Restriction_Id is
 
@@ -126,6 +127,7 @@ package System.Rident is
       No_Implicit_Task_Allocations,              -- GNAT
       No_Implicit_Protected_Object_Allocations,  -- GNAT
       No_Initialize_Scalars,                     -- GNAT
+      No_Local_Tagged_Types,                     -- GNAT
       No_Local_Allocators,                       -- (RM H.4(8))
       No_Local_Timing_Events,                    -- (RM D.7(10.2/2))
       No_Local_Protected_Objects,                -- Ada 2012 (D.7(10/1.3))

gcc/ada/restrict.ads

@@ -131,6 +131,7 @@ package Restrict is
       No_Implicit_Protected_Object_Allocations => True,
       No_Implicit_Task_Allocations             => True,
       No_Initialize_Scalars                    => True,
+      No_Local_Tagged_Types                    => True,
       No_Long_Long_Integers                    => True,
       No_Multiple_Elaboration                  => True,
       No_Secondary_Stack                       => True,

gcc/ada/sem_ch3.adb

@@ -3479,6 +3479,14 @@ package body Sem_Ch3 is
       then
          Check_Nonoverridable_Aspects;
       end if;
+
+      --  Check for tagged type declaration at library level
+
+      if Is_Tagged_Type (T)
+        and then not Is_Library_Level_Entity (T)
+      then
+         Check_Restriction (No_Local_Tagged_Types, T);
+      end if;
    end Analyze_Full_Type_Declaration;
 
    ----------------------------------