Why is FluidDataSet default constructor marked explicit?

[weefuzzy]

It doesn't seem like it would have any effect on anything. The purpose of explicit is to prevent accidental implicit conversions, which isn't an issue for a constructor with no arguments. 

[AlexHarker]

Just for fun it looks like it will do this:

https://godbolt.org/z/4xcMbqrno

and this:

https://godbolt.org/z/xccjGqxE8

Both of those compile without the explicit keyword. They are edge cases though, and I'm not sure if it's really useful to prevent these, but it doesn't have no effect.