using T = std::vector<std::unique_ptr<int>>;
Why std::is_copy_constructible<T> is true, but following does not compile:
using T = vector<unique_ptr<int>>;
T v1;
T v2 = v1;
(It does not compile in Clang, GCC and MSVC with C++17.)
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vladon
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Good question, this particular case was asked before. Basically, is_copy_constructible cannot "see" past the existence of the copy constructor that would ultimately fail when invoked. – GManNickG May 31 '20 at 02:30
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1@GManNickG see also interesting bug causes by this: https://stackoverflow.com/questions/62110426/why-code-with-stdvector-fails-to-compile-but-with-stdunique-ptr-does-not-if – vladon May 31 '20 at 02:32