Not really. First argument (the object you are extending) needs to be marked with `this`, which is an annotation.

Ehh, ive been talking about whole lang and ecosystem

But I agree about "this" being similar concept

There are tons of annotations over the hood.

The "this" that GP mentions is for for extension methods similar to the article to be regcognizeed as such (never done if the annotation isn't present), they're written such as:

static int Foo( this Bar bar, int biz) => bar.xyz+biz;

Bar bar = new Bar() { xyz=123; };

int result = bar.Foo(456); // Works even if Foo wasn't a part of Bar initially

Elsewhere annotations(called attributes in C# land) can often be used in the same way as in Java to document serialization behaviour,etc. So in practice there aren't much differences apart from how library authors haven't embraced it entirely as much for automagic bindings (partly due to philosophy, partly due to other facilities being more appropriate).

There is a massive difference between a feature universally offered by the language and something only supported by using a specific library of compiler plugin...

What a weird take. Parent obviously meant @X meta-programming annotations, not language syntax and keywords with a specific definition.

The definition that includes it is so broad that it loses all meaning, it would make "private", "class" or "boolean" also annotations.

In .net world, the C# "this" syntax is itself just syntactic sugar over an annotation (attribute in .net parlance): https://learn.microsoft.com/en-us/dotnet/api/system.runtime....

offtopic: why is this link a broken redirect in chrome but not firefox?

My guess is that MSDN POs prioritize testing with Blink/Edge WebView2 over other engines.

Just to make it clear, Fluent does not use any annotations.

Isn't this just saying some languages do things others do not?

No, annotations are available in both, yet one community uses them more often

So, "some languages do this with annotations, others don't need it". My point stands.

I mean it's fine to not like annotations or the decision to use them, but that another language does things differently is almost a tautology and hardly worthy of note. IMO, reasonable people will disagree.