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STD-DISCUSSION |
Subject: Can static_assert(false) be ignored in if constexpr?
From: Yongwei Wu (wuyongwei_at_[hidden])
Date: 2021-01-13 08:07:05
I have tried writing code like the following:
template <typename T>
ReturnType Function(T&& arg)
{
if constexpr(condition_on_<T>) {
// Something to do
} else if constexpr(another_condition_on<T>) {
// Something else to do
} else {
static_assert(false, "T does not satisfy constraint");
}
// Some common processing regarding arg
}
Yet, even if the provided T goes to one of the first two constexpr
condition branches, the static assertion will fail....
Yes, I can rewrite the code above as:
template <typename T>
ReturnType Function(T&& arg)
{
static_assert(condition_on<T> && another_condition_on<T>);
if constexpr(condition_on_<T>) {
// Something to do
} else {
// Something else to do
}
}
But then I have the conditions duplicated. Code duplications are bad, right?
So my question is: Is there a reason that the static_assert(false) in an
unused if-constexpr branch must cause the whole compilation to fail? Is
there a way to achieve what I want without code duplications?
Thanks in advance.
Best regards,
-- Yongwei Wu URL: http://wyw.dcweb.cn/
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