Address compilation issue with FunctionType.

Author: lcartey

cpp/common/src/codingstandards/cpp/Call.qll

@@ -1,5 +1,6 @@
 import cpp
 import codingstandards.cpp.types.Type
+import codingstandards.cpp.types.FunctionType
 
 /**
  * Gets the `FunctionType` of an expression call.

cpp/common/src/codingstandards/cpp/types/Compatible.qll

@@ -527,7 +527,6 @@ module FunctionDeclarationTypeEquivalence<
 private class LeafType extends Type {
   LeafType() {
     not this instanceof DerivedType and
-    not this instanceof FunctionType and
     not this instanceof FunctionType
   }
 }

cpp/common/src/codingstandards/cpp/types/Type.qll

@@ -124,21 +124,3 @@ int sizeOfInt() {
       size
     )
 }
-
-/**
- * Convenience class to reduce the awkwardness of how `RoutineType` and `FunctionPointerIshType`
- * don't have a common ancestor.
- */
-class FunctionType extends Type {
-  FunctionType() { this instanceof RoutineType or this instanceof FunctionPointerIshType }
-
-  Type getReturnType() {
-    result = this.(RoutineType).getReturnType() or
-    result = this.(FunctionPointerIshType).getReturnType()
-  }
-
-  Type getParameterType(int i) {
-    result = this.(RoutineType).getParameterType(i) or
-    result = this.(FunctionPointerIshType).getParameterType(i)
-  }
-}