What's wrong with explicit(false)?

struct A { explicit(false) A(int); };

On Wed, 9 Jun 2021, 02:06 Walt Karas via Std-Proposals, <
std-proposals_at_[hidden]> wrote:

> For constructors that can be called with a single argument, and can be
> called implicitly. For example:
>
> struct A { auto A(int); };
>
> would be equivalent to simply:
>
> struct A { A(int); };
>
> This would allows compilers to support an option to require that
> constructors callable with one argument (other that copy/move constructors)
> be preceded by either "explicit" or "auto", otherwise a diagnostic is
> output. This would be helpful to me and presumably others, who on occasion
> forget to make a conversion constructor explicit when it should be.
>
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