[meta.rel] is_­nothrow_­convertible does not clearly require nothrow destruction LWG 3400, LWG 2116

By @Dani-Hub , is_nothrow_convertible considers destruction of the converted object (if To is an object type) or the temporary (if To is a reference type and the temporary to bind would be created) by design. And known implementations (msvc, libc++, libstdc++) behave correctly.

For example, given a type Weird defined as

struct Weird {
  Weird(int) noexcept {}
  ~Weird() noexcept(false) {}
};

Then std::is_nothrow_convertible_v<int, Weird> is false.

However, I suspect that wording in [meta.rel]/5 only requires the well-formedness, and whether the destruction after the initialization of To is considered as part of the conversion is not mentioned.
So "the conversion, as defined by is_­convertible" in the specification of is_nothrow_convertible might not be precisely defined, and may lead to unintended comprehension, e.g. std::is_nothrow_convertible_v<int, Weird> can be true since the converting constructor itself is noexcept, although destruction of Weird is not.

Start with [meta.rel]/5 and compare the wording with LWG 3400 and LWG 2116, using the Weird example to check how destruction is treated. Done means the standard wording clearly specifies whether destruction is part of the conversion considered by is_nothrow_convertible.