[Ada] Crash on improper use of GNAT attribute Type_Key

[Pierre-Marie de Rodat via Gcc-patches]

This patch fixes a crash on a case statement whose expression is an
attribute reference Type_Key, which yields a String. The attribute
reference may have been fully analyzed, and the resolution against
Any_Discrete fails to detect the error.

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

gcc/ada/

        * sem_attr.adb (Analyze_Attribute, case Type_Key): Attribute can
        be applied to a formal type.
        * sem_ch5.adb (Analyze_Case_Statement): If Extensions_Allowed is
        not enabled, verify that the type of the expression is discrete.
diff --git a/gcc/ada/sem_attr.adb b/gcc/ada/sem_attr.adb
--- a/gcc/ada/sem_attr.adb
+++ b/gcc/ada/sem_attr.adb
@@ -6643,7 +6643,9 @@ package body Sem_Attr is
          Initialize (CRC);
          Compute_Type_Key (Entity (P));
 
-         if not Is_Frozen (Entity (P)) then
+         if not Is_Frozen (Entity (P))
+           and then not Is_Generic_Type (Entity (P))
+         then
             Error_Msg_N ("premature usage of Type_Key?", N);
          end if;
 


diff --git a/gcc/ada/sem_ch5.adb b/gcc/ada/sem_ch5.adb
--- a/gcc/ada/sem_ch5.adb
+++ b/gcc/ada/sem_ch5.adb
@@ -1681,6 +1681,13 @@ package body Sem_Ch5 is
          Error_Msg_N
            ("(Ada 83) case expression cannot be of a generic type", Exp);
          return;
+
+      elsif not Extensions_Allowed
+        and then not Is_Discrete_Type (Exp_Type)
+      then
+         Error_Msg_N
+           ("expression in case statement must be of a discrete_Type", Exp);
+         return;
       end if;
 
       --  If the case expression is a formal object of mode in out, then treat