Decompiler cspec prototype optional "type" attribute

[Wall-AF]

Whilst trying to add a cspec prototype for a "far" equivalent to “thiscall”, I found there to be an attribute of the “<prototype …>” XML tag called “type”:
<prototype>

Attributes and Children
name	The name of the prototype model
extrapop	Amount stack pointer changes across a call or unknown
stackshift	Amount stack changes due to the call mechanism
type	(Optional) Generic calling convention type: stdcall, cdecl, fastcall, or thiscall
strategy	(Optional) Allocation strategy: standard or register

Presuming this to be the mechanism to ensure my new prototype followed existing rules of the in-built prototypes, I tried it.

When it came to the “Decompile" view I got no decompilation, just this error:

  Decompiler: Unable to initialize the DecompilerInterface: Could not register program:
  Low-level Error: Unknown prototype attribute: type

So, what’s happening?

[Wall-AF]

It seems that there's also an undocumented hasthis attribute which does this job, but the type one causes a LowLevelError exception from void ProtoModel::restoreXml(const Element *el) in file fspec.cc!