# Execute `mpropdef` for a `args` (where `args[0]` is the receiver).
	# Return a value if `mpropdef` is a function, or null if it is a procedure.
	# The call is direct/static. There is no message-sending/late-binding.
	fun call(mpropdef: MMethodDef, args: Array[Instance]): nullable Instance
	do
		if self.modelbuilder.toolcontext.opt_discover_call_trace.value and not self.discover_call_trace.has(mpropdef) then
			self.discover_call_trace.add mpropdef
			self.debug("Discovered {mpropdef}")
		end
		assert args.length == mpropdef.msignature.arity + 1 else debug("Invalid arity for {mpropdef}. {args.length} arguments given.")

		# Look for the AST node that implements the property
		var val = mpropdef.constant_value

		var node = modelbuilder.mpropdef2node(mpropdef)
		if mpropdef.is_abstract then
			if node != null then
				self.frames.unshift new_frame(node, mpropdef, args)
			end
			fatal("Abstract method `{mpropdef.mproperty.name}` called on `{args.first.mtype}`")
			abort
		end

		if node isa APropdef then
			self.parameter_check(node, mpropdef, args)
			return node.call(self, mpropdef, args)
		else if node isa AClassdef then
			self.parameter_check(node, mpropdef, args)
			return node.call(self, mpropdef, args)
		else if node != null then
			fatal("Fatal Error: method {mpropdef} associated to unexpected AST node {node.location}")
			abort
		else if val != null then
			return value_instance(val)
		else
			fatal("Fatal Error: method {mpropdef} not found in the AST")
			abort
		end
	end