https://dlang.org/spec/betterc.html

https://dlang.org/spec/importc.html

> Note: ImportC and BetterC are very different. ImportC is an actual C compiler. BetterC is a subset of D that relies only on the existence of the C Standard library. BetterC code can be linked with ImportC code, too.

D contains an actual C compiler because Walter Bright wrote one long ago and then incorporated it into D.

Zig also contains an actual C compiler, based on clang, and has a @cImport directive.