[Ada] Don't split AND THEN expressions in GNATprove_Mode

Splitting AND THEN expressions in contracts into separate pragma Check
is only useful for compilation when the error message points to a failed
conjunct. For proof it is of no use; for flow analysis it is annoying.
Also, it makes debugging harder. Now it is disabled in GNATprove_Mode.

Compilation is not affected, so no test provided.

2018-06-11  Piotr Trojanek  <trojanek@adacore.com>

gcc/ada/

	* sem_ch13.adb (Analyze_Aspect_Specifications): Don't split AND THEN
	expressions in Pre/Post contracts while in GNATprove_Mode.

From-SVN: r261411

gcc/ada/ChangeLog

 2018-06-11  Piotr Trojanek  <trojanek@adacore.com>
 
+	* sem_ch13.adb (Analyze_Aspect_Specifications): Don't split AND THEN
+	expressions in Pre/Post contracts while in GNATprove_Mode.
+
+2018-06-11  Piotr Trojanek  <trojanek@adacore.com>
+
 	* sem_util.adb (Is_Potentially_Unevaluated): Fix detection of contracts
 	with AND THEN expressions broken down into individual conjuncts.
 

gcc/ada/sem_ch13.adb

@@ -3443,9 +3443,13 @@ package body Sem_Ch13 is
 
                   --  We do not do this in ASIS mode, as ASIS relies on the
                   --  original node representing the complete expression, when
-                  --  retrieving it through the source aspect table.
+                  --  retrieving it through the source aspect table. Also, we
+                  --  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.
 
-                  if not ASIS_Mode
+                  if not (ASIS_Mode or GNATprove_Mode)
                     and then (Pname = Name_Postcondition
                                or else not Class_Present (Aspect))
                   then