Higher level languages inevitably come with built in semantics that the programmer takes for granted, but can't be synthesized directly to hardware. In C, it's the function call stack. In Haskell it's higher order types and recursive data structures (and more). You could in theory create some runtime package that you'd compile to hardware for your program to be synthesized to, or "run on".....but then you'd just be making a straight up computer, wouldn't you. ;-)
None of these things are relevant in most HDLs implemented as DSLs in high level languages. The point of most of the HDL work in Haskell (for example Lava, and Bluespec) is to provide primitives to talk about hardware and to use a sane language as a way to manipulate them to build larger specifications. It is embarrassing that people use tools that allow you to write un-synthesizable code.
