Mingun

I think this one is superseded by #1550 and can be closed in preference to it

Yes, this is duplicate of #1183

I cannot agree with such a question. For me, the runtime performance is much more important thing that compile-time performance. Things are written not for the pleasure of developers, but...

I've made some research and there is the results. I've created a library project with 1000 types and I've measured compilation time. I've noticed small increasing of the compilation time,...

I didn't measure it, maybe I should

For the optimized case yes, it should

What the table headers mean?

From the other hand a new struct attribute could be added, for example, `#[serde(strict_order)]` which would allow only the order that is defined in the struct

This should be easy to implement, need just introduce and use special `RefInto` trait, and existing `#[serde(into = "IntoType")]` should be enough: https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=4b5e87587edfb6e35952da321a1d72d9

I think, that using a json is a bad example to demonstrate absence of "lossy deserialization", because JSON contains some information about value type. Try some untyped format, like XML...