This sounds like a solution to a problem that probably shouldn't exist because there is a solution that shouldn't exist to start with which has caused a problem that doesn't need to occur.

The slightly overbearing complexity of the solution matches the linguistic complexity of the statement above :)

I don't see how these are significantly different than .PDBs which allow Windows developers to step through their source code when debugging compiled binaries.

It is similar to PDB files, which is fine but that is not the issue. The issue is that the abstraction is criminally tall. We're talking a tower of:

Process: C# --(compiler)--> Js --(parser)--> IL --(compiler)--> machine code/interpreter.

Type conversions: Static --> dynamic --> static --> none.

That's just too much to go wrong in my mind. I wouldn't touch it with a barge pole.

They do come in handy, if only they were supported everywhere. Right now it's just Chrome and a small number of tools.