message: Fix OSS build
  Summary:
  Pull Request resolved:
  Add the missing default ctor for
diff: @@ -62,6 +62,12 @@ class ConstNullnessDomain
  public:
  using ReducedProductAbstractDomain::ReducedProductAbstractDomain;
  + // Some older compilers complain that the class is not default
  + // constructible. We intended to use the default constructors of the base
  + // class (via the `using` declaration above), but some compilers fail to
  + // catch this. So we insert a redundant '= default'.
  + ConstNullnessDomain() = default;
  +
  explicit ConstNullnessDomain(Nullness nullness)
  : ConstNullnessDomain(
  std::make_tuple(ConstantDomain(0), NullnessDomain(nullness))) {}
  