[Ada] SPARK_Mode Off now allowed inside subprogram

[Pierre-Marie de Rodat <derodat@adacore.com>]

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The rule on SPARK_Mode have been modified so that it is now possible to
have a subprogram or package declared with SPARK_Mode Off inside a
subprogram.

Tested on x86_64-pc-linux-gnu, committed on trunk

2019-07-04  Yannick Moy  <moy@adacore.com>

gcc/ada/

	* sem_prag.adb (Check_Library_Level_Entity): Update for new rule
	on SPARK_Mode.

gcc/testsuite/

	* gnat.dg/spark3.adb: New testcase.

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--- gcc/ada/sem_prag.adb
+++ gcc/ada/sem_prag.adb
@@ -23189,7 +23189,16 @@ package body Sem_Prag is
             --  Start of processing for Check_Library_Level_Entity
 
             begin
-               if not Is_Library_Level_Entity (E) then
+               --  A SPARK_Mode of On shall only apply to library-level
+               --  entities, except for those in generic instances, which are
+               --  ignored (even if the entity gets SPARK_Mode pragma attached
+               --  in the AST, its effect is not taken into account unless the
+               --  context already provides SPARK_Mode of On in GNATprove).
+
+               if Get_SPARK_Mode_From_Annotation (N) = On
+                 and then not Is_Library_Level_Entity (E)
+                 and then Instantiation_Location (Sloc (N)) = No_Location
+               then
                   Error_Msg_Name_1 := Pname;
                   Error_Msg_N (Fix_Error (Msg_1), N);
 

--- /dev/null
new file mode 100644
+++ gcc/testsuite/gnat.dg/spark3.adb
@@ -0,0 +1,20 @@
+--  { dg-do compile }
+
+procedure SPARK3 (X : in out Integer) with SPARK_Mode is
+
+   procedure Q (X : in out Integer) with SPARK_Mode => Off is
+   begin
+      X := X + 1;
+   end Q;
+
+   procedure R (X : in out Integer);
+
+   procedure R (X : in out Integer) with SPARK_Mode => Off is
+   begin
+      Q (X);
+   end R;
+
+begin
+   R (X);
+   X := X + 1;
+end SPARK3;