Is there a D IDE with good code completion and refactoring support? Last time I tried it, all that I've seen were pretty bad at it - handling the simple stuff fine, but breaking down on more complicated stuff, metaprogramming especially (kinda like most C++ IDEs did 8 years ago or so).
Code completion yes. (DCD provides this as a library). d-mode for emacs is nice, both of the plugins for vs-code I know work. There are plugins/extensions for (i think) xcode and (i know) Jetbrains's stuff (I don't use it so i can't really comment.
Refactoring, no.
Edit: There is also a D-specific IDE called coedit, which is pretty good AFAIK