Class LazyExpression

unittests/catch.hpp:1519–1534

    class RunContext;

    class LazyExpression {
        friend class AssertionHandler;
        friend struct AssertionStats;
        friend class RunContext;

        ITransientExpression const* m_transientExpression = nullptr;
        bool m_isNegated;
    public:
        LazyExpression( bool isNegated );
        LazyExpression( LazyExpression const& other );
        LazyExpression& operator = ( LazyExpression const& ) = delete;

        explicit operator bool() const;

        friend auto operator << ( std::ostream& os, LazyExpression const& lazyExpr ) -> std::ostream&;
    };

    struct AssertionReaction {
        bool shouldDebugBreak = false;