C++: Use underlyingElement for QualifiedName calls

Since the types in `QualifiedName.qll` are raw db types, callers need to
use `underlyingElement` and `unresolveElement` as appropriate. This has
no effect right now but will be needed when we switch the AST type
hierarchy to `newtype`s.

cpp/ql/src/semmle/code/cpp/Declaration.qll

@@ -31,7 +31,7 @@ abstract class Declaration extends Locatable, @declaration {
    * namespace of the structure.
    */
   Namespace getNamespace() {
-    result = this.(Q::Declaration).getNamespace()
+    result = underlyingElement(this).(Q::Declaration).getNamespace()
     or
     exists (Parameter p
     | p = this and result = p.getFunction().getNamespace())
@@ -53,7 +53,7 @@ abstract class Declaration extends Locatable, @declaration {
    * "namespace1::namespace2::TemplateClass1<int>::Class2::memberName"`.
    */
   string getQualifiedName() {
-    result = this.(Q::Declaration).getQualifiedName()
+    result = underlyingElement(this).(Q::Declaration).getQualifiedName()
   }
 
   /**
@@ -84,7 +84,8 @@ abstract class Declaration extends Locatable, @declaration {
    * `hasQualifiedName("std", "vector", "size")`.
    */
   predicate hasQualifiedName(string namespaceQualifier, string typeQualifier, string baseName) {
-    this.(Q::Declaration).hasQualifiedName(namespaceQualifier, typeQualifier, baseName)
+    underlyingElement(this).(Q::Declaration)
+      .hasQualifiedName(namespaceQualifier, typeQualifier, baseName)
   }
 
   /**
@@ -115,7 +116,7 @@ abstract class Declaration extends Locatable, @declaration {
    * To test whether this declaration has a particular name in the global
    * namespace, use `hasGlobalName`.
    */
-  string getName() { result = this.(Q::Declaration).getName() }
+  string getName() { result = underlyingElement(this).(Q::Declaration).getName() }
 
   /** Holds if this declaration has the given name. */
   predicate hasName(string name) { name = this.getName() }

cpp/ql/src/semmle/code/cpp/Parameter.qll

@@ -55,7 +55,9 @@ class Parameter extends LocalScopeVariable, @parameter {
    * In other words, this predicate holds precisely when the result of
    * `getName()` is not "p#i" (where `i` is the index of the parameter).
    */
-  predicate isNamed() { exists(this.(Q::Parameter).getANamedDeclarationEntry()) }
+  predicate isNamed() {
+    exists(underlyingElement(this).(Q::Parameter).getANamedDeclarationEntry())
+  }
 
   /**
    * Gets the function to which this parameter belongs, if it is a function
@@ -96,12 +98,12 @@ class Parameter extends LocalScopeVariable, @parameter {
    */
   override Location getLocation() {
     exists(VariableDeclarationEntry vde |
-      vde = this.(Q::Parameter).getAnEffectiveDeclarationEntry() and
+      vde = underlyingElement(this).(Q::Parameter).getAnEffectiveDeclarationEntry() and
       result = vde.getLocation()
     |
       vde.isDefinition()
       or
-      not this.(Q::Parameter).getAnEffectiveDeclarationEntry().isDefinition()
+      not underlyingElement(this).(Q::Parameter).getAnEffectiveDeclarationEntry().isDefinition()
     )
   }
 }