C++: Implement Function::hasErrors()

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

@@ -500,6 +500,14 @@ class Function extends Declaration, ControlFlowNode, AccessHolder, @function {
    * Gets the nearest enclosing AccessHolder.
    */
   override AccessHolder getEnclosingAccessHolder() { result = this.getDeclaringType() }
+
+  /**
+   * Holds if this function has extraction errors that create an `ErrorExpr`.
+   */
+  predicate hasErrors() {
+    // Exclude allocator call arguments because they are are always extracted as `ErrorExpr`.
+    exists(ErrorExpr e | e.getEnclosingFunction() = this and not e.isFirstAllocatorCallArgument())
+  }
 }
 
 pragma[noinline]

cpp/ql/lib/semmle/code/cpp/exprs/Expr.qll

@@ -744,6 +744,13 @@ class ErrorExpr extends Expr, @errorexpr {
   override string toString() { result = "<error expr>" }
 
   override string getAPrimaryQlClass() { result = "ErrorExpr" }
+
+  /**
+   * Holds if this error expression is the first argument to a `new` allocation call.
+   */
+  predicate isFirstAllocatorCallArgument() { 
+    this = any(NewOrNewArrayExpr new).getAllocatorCall().getArgument(0)
+  }
 }
 
 /**