C++: Add missing overrides.

Author: MathiasVP

cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/SsaImpl.qll

@@ -1357,6 +1357,16 @@ class PhiNode extends Definition instanceof SsaImpl::PhiNode {
   final predicate hasInputFromBlock(Definition input, IRBlock bb) {
     phiHasInputFromBlock(this, input, bb)
   }
+
+  override int getIndirection() { result = this.getSourceVariable().getIndirection() }
+
+  override predicate isCertain() {
+    forex(Definition inp | inp = this.getAnInput() | inp.isCertain())
+  }
+
+  final override Declaration getFunction() {
+    result = SsaImpl::PhiNode.super.getBasicBlock().getEnclosingFunction()
+  }
 }
 
 /** An static single assignment (SSA) definition. */

cpp/ql/test/library-tests/dataflow/certain/test.cpp

@@ -28,7 +28,7 @@ void test2(bool b) { // $ certain="SSA def(&b)" certain="SSA def(b)"
   } else {
     x = 1; // $ certain="SSA def(x)"
   }
-  use(x); // $ uncertain="SSA phi(x)"
+  use(x); // $ certain="SSA phi(x)"
   }
 
   {
@@ -38,7 +38,7 @@ void test2(bool b) { // $ certain="SSA def(&b)" certain="SSA def(b)"
   } else {
 
   }
-  use(x); // $ uncertain="SSA phi(x)"
+  use(x); // $ certain="SSA phi(x)"
   }
 
   {