And while some features in other languages might have seen an implementation first in D, claiming first to the finish line as it usually comes up, even on this thread, hardly does anything for language adoption.
On the contrary, it is one reason less leave those languages, as eventually they get the features, and already have the ecosystem.
Most of the stuff that interested me back in 2007, is now available across in C#, F#, JVM languages, Swift, OCaml, Haskell, with a better ecosystem and IDE tooling.
And then there is C++26 and Rust 2024.
You achieved a lot as language designer, but it is still not clear how the community would keep the language going forward in lets say 10 years from now.
GCC (and possibly other compilers) had typeof in the '90s well before D was first released. Macros in the form:
#define TYPEOF(name, expr) typeof(expr) name = expr
I'm sure that C++ borrowed concepts from D, but type deduction (not inference BTW) is not one of them.
It's a prototype to gauge the interest in having a borrow checker in the language. I did not continue with it because the interest is not there.
And funny, C++ has been copying many features that DLang have for many time ago. Beginning with the type inference (ie using "auto" to declare vars). And now, contractual programing and static reflection.
I really loved the language, but it's very sad that never manages to take off and become more popular and well maintained.