[Ada] Spurious error on precondition of subprogram instantiation

2019-12-13  Javier Miranda  <miranda@adacore.com>

gcc/ada/

	* sem_ch13.adb (Analyze_Aspect_Specification): Processing a
	precondition, if the expression is of the form A and then B, do
	not generate separate Pre/Post aspects for the separate clases
	when we are processing a generic unit. Required to avoid
	reporting spurious visibility errors on the instantiations.

From-SVN: r279365

gcc/ada/ChangeLog

+2019-12-13  Javier Miranda  <miranda@adacore.com>
+
+	* sem_ch13.adb (Analyze_Aspect_Specification): Processing a
+	precondition, if the expression is of the form A and then B, do
+	not generate separate Pre/Post aspects for the separate clases
+	when we are processing a generic unit. Required to avoid
+	reporting spurious visibility errors on the instantiations.
+
 2019-12-13  Eric Botcazou  <ebotcazou@adacore.com>
 
 	* sem_res.adb (Resolve_Actuals): Give canonical error for

gcc/ada/sem_ch13.adb

@@ -3479,11 +3479,14 @@ package body Sem_Ch13 is
                   --  don't do this in GNATprove mode, because it brings no
                   --  benefit for proof and causes annoynace for flow analysis,
                   --  which prefers to be as close to the original source code
-                  --  as possible.
+                  --  as possible. Also we don't do this when analyzing generic
+                  --  units since it causes spurious visibility errors in the
+                  --  preanalysis of instantiations.
 
                   if not (ASIS_Mode or GNATprove_Mode)
                     and then (Pname = Name_Postcondition
                                or else not Class_Present (Aspect))
+                    and then not Inside_A_Generic
                   then
                      while Nkind (Expr) = N_And_Then loop
                         Insert_After (Aspect,