[Bug c++/88628] lambda expression in static_assert in if constexpr is not evaluated

[merukun1125 at docomo dot ne.jp]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88628

--- Comment #3 from merukun1125 at docomo dot ne.jp ---
(In reply to Jakub Jelinek from comment #2)
> clang++ agrees with g++ here.  The lambda expression needs to be
> instantiated so that it can be evaluated and expressions in discarded
> statements are not instantiated.

#include <type_traits>

template<typename T>
constexpr bool false_v = false;

template<typename T>
T get() {
    if constexpr (std::is_same_v<int, T>) return 0;
    else static_assert(false_v<T>, "...");
}

int main() {
    get<int>();
}

This code does not fail to compile.
https://wandbox.org/permlink/jQB3P93GWTA2b4xs

But

#include <type_traits>

template<typename T>
T get() {
    if constexpr (std::is_same_v<int, T>) return 0;
    else static_assert(std::false_type{}, "...");
}

int main() {
    get<int>();
}

This code fail to compile.
https://wandbox.org/permlink/MyyxwVGorihFGW2G

So, I think that constexpr if is a function to suppress instantiation of
templates of unselected branches. In other words, the first phase of two-phase
name lookup is supposed to be executed.

So, I thought that lambda expressions without dependency names should be
evaluated.