C++: Implement Expr::mayBeFromImplicitlyDeclaredFunction

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

@@ -300,6 +300,11 @@ class FunctionCall extends Call, @funbindexpr {
     this.isVirtual() or
     this.getTarget().getAnAttribute().getName() = "weak"
   }
+
+  override predicate mayBeFromImplicitlyDeclaredFunction() {
+    this.getType() instanceof IntType and
+    this.getTarget().getADeclarationEntry().isImplicit()
+  }
 }
 
 /** A _user-defined_ unary `operator*` function. */

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

@@ -534,6 +534,9 @@ class Expr extends StmtParent, @expr {
 
   /** Gets the function containing this control-flow node. */
   override Function getControlFlowScope() { result = this.getEnclosingFunction() }
+
+  /** Holds if this expression could be the return value of an implicitly declared function. */
+  predicate mayBeFromImplicitlyDeclaredFunction() { none() }
 }
 
 /**