Visual Studio warning C4334 on assignment but not on initialization

问题

Why i got warning on this code:

#include <cstdint>

int main()
{
    int i = 1;
    int64_t i64;
    i64 = 1 << i;
}

warning C4334: '<<' : result of 32-bit shift implicitly converted to 64 bits (was 64-bit shift intended?)

but not on this:

#include <cstdint>

int main()
{
    int i = 1;
    int64_t i64 = 1 << i;
}

? Tested on vs2013/2015.

回答1:

I see the same discrepancy with vs2012. I don't think that there is a good reason for it - hopefully the warning will be emitted in both cases in a newer version of Visual C++.

回答2:

MSVS 2015 Upd.2: Second case (on initialization) will trigger C4334 warning.

来源：https://stackoverflow.com/questions/31558314/visual-studio-warning-c4334-on-assignment-but-not-on-initialization