[Ada] Fix type conversion handling in validity checks

[Pierre-Marie de Rodat via Gcc-patches]

In case of a checked type conversion, correctly update Typ to match the
expression being validated and call Analyze_And_Resolve on the modified
expression.

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

gcc/ada/

        * checks.adb (Insert_Valid_Check): in case of checked type
        conversion, update Typ to match Exp's type and add call to
        Analyze_And_Resolve.
diff --git a/gcc/ada/checks.adb b/gcc/ada/checks.adb
--- a/gcc/ada/checks.adb
+++ b/gcc/ada/checks.adb
@@ -8077,7 +8077,7 @@ package body Checks is
       Is_High_Bound : Boolean   := False)
    is
       Loc : constant Source_Ptr := Sloc (Expr);
-      Typ : constant Entity_Id  := Etype (Expr);
+      Typ : Entity_Id           := Etype (Expr);
       Exp : Node_Id;
 
    begin
@@ -8137,6 +8137,7 @@ package body Checks is
       while Nkind (Exp) = N_Type_Conversion loop
          Exp := Expression (Exp);
       end loop;
+      Typ := Etype (Exp);
 
       --  Do not generate a check for a variable which already validates the
       --  value of an assignable object.
@@ -8217,6 +8218,14 @@ package body Checks is
                Set_Do_Range_Check (Validated_Object (Var_Id), False);
             end if;
 
+            --  In case of a type conversion, an expansion of the expr may be
+            --  needed (eg. fixed-point as actual).
+
+            if Exp /= Expr then
+               pragma Assert (Nkind (Expr) = N_Type_Conversion);
+               Analyze_And_Resolve (Expr);
+            end if;
+
             PV := New_Occurrence_Of (Var_Id, Loc);
 
          --  Otherwise the expression does not denote a variable. Force its