C++: Fix bad magic on Element.getFile when running on InconsistentCheckReturnNull.qll:

Evaluated non-recursive predicate Element::Element.getFile/0#dispred#536cb5f3#bb@f6f5329i in 182326ms (size: 50437).
Evaluated relational algebra for predicate Element::Element.getFile/0#dispred#536cb5f3#bb@f6f5329i with tuple counts:
           2029351   ~0%    {2} r1 = SCAN `Expr::Expr.getLocation/0#dispred#0a3d90c6` OUTPUT In.1, In.0
           2029351   ~0%    {2}    | JOIN WITH `Location::Location.getStartLine/0#d54f9e6c` ON FIRST 1 OUTPUT Rhs.1, Lhs.1
           1168789   ~0%    {2}    | JOIN WITH `InconsistentCheckReturnNull::assertInvocation/2#b2a4c9e3_10#join_rhs` ON FIRST 1 OUTPUT Rhs.1, Lhs.1
        5533128288   ~0%    {3}    | JOIN WITH `Location::Location.getContainer/0#9edabfb6_10#join_rhs` ON FIRST 1 OUTPUT Lhs.1, Rhs.1, Lhs.0
             50413   ~0%    {2}    | JOIN WITH `Element::Element.getLocation/0#dispred#6c3f5b09#bf` ON FIRST 2 OUTPUT Lhs.0, Lhs.2

              3043   ~0%    {2} r2 = JOIN `project#InconsistentCheckReturnNull::relevantFunctionCall/2#d18cd566` WITH `Expr::Expr.getLocation/0#dispred#0a3d90c6` ON FIRST 1 OUTPUT Rhs.1, Lhs.0

              3043   ~0%    {2} r3 = JOIN r2 WITH locations_default ON FIRST 1 OUTPUT Rhs.4, Lhs.1
              1945   ~3%    {2}    | JOIN WITH `InconsistentCheckReturnNull::assertInvocation/2#b2a4c9e3_10#join_rhs` ON FIRST 1 OUTPUT Rhs.1, Lhs.1
           9106248   ~2%    {3}    | JOIN WITH `Location::Location.getContainer/0#9edabfb6_10#join_rhs` ON FIRST 1 OUTPUT Lhs.1, Rhs.1, Lhs.0
                 0   ~0%    {2}    | JOIN WITH `Element::Element.getLocation/0#dispred#6c3f5b09#bf` ON FIRST 2 OUTPUT Lhs.0, Lhs.2

              3043   ~0%    {3} r4 = JOIN r2 WITH locations_default ON FIRST 1 OUTPUT _, Lhs.1, Rhs.4
              3043   ~0%    {2}    | REWRITE WITH Tmp.0 := 1, Out.0 := (In.2 + Tmp.0) KEEPING 2
              2013   ~0%    {2}    | JOIN WITH `InconsistentCheckReturnNull::assertInvocation/2#b2a4c9e3_10#join_rhs` ON FIRST 1 OUTPUT Rhs.1, Lhs.1
           9621327   ~0%    {3}    | JOIN WITH `Location::Location.getContainer/0#9edabfb6_10#join_rhs` ON FIRST 1 OUTPUT Lhs.1, Rhs.1, Lhs.0
                24   ~3%    {2}    | JOIN WITH `Element::Element.getLocation/0#dispred#6c3f5b09#bf` ON FIRST 2 OUTPUT Lhs.0, Lhs.2

             50437   ~0%    {2} r5 = r1 UNION r3 UNION r4
                            return r5

Author: MathiasVP

cpp/ql/lib/semmle/code/cpp/Element.qll

@@ -87,6 +87,7 @@ class ElementBase extends @element {
  */
 class Element extends ElementBase {
   /** Gets the primary file where this element occurs. */
+  pragma[nomagic]
   File getFile() { result = this.getLocation().getFile() }
 
   /**