Call serialisation schema is broken

[mark-koch]

Following #906, the Call op is now defined as

hugr/hugr/src/ops/dataflow.rs

Lines 154 to 159 in d69198e

	pub struct Call {
	/// Signature of function being called
	func_sig: PolyFuncType,
	type_args: Vec<TypeArg>,
	instantiation: FunctionType, // Cache, so we can fail in try_new() not in signature()
	}

However, the corresponding pydantic model doesn't match up:

hugr/hugr-py/src/hugr/serialization/ops.py

Lines 246 to 264 in d69198e

	class Call(DataflowOp):
	"""
	Call a function directly.
	The first port is connected to the def/declare of the function being called
	directly, with a `ConstE<Graph>` edge. The signature of the remaining ports matches
	the function being called.
	"""
	op: Literal["Call"] = "Call"
	signature: FunctionType = Field(default_factory=FunctionType.empty)
	def insert_port_types(self, in_types: TypeRow, out_types: TypeRow) -> None:
	# The constE edge comes after the value inputs
	fun_ty = in_types[-1]
	assert isinstance(fun_ty, PolyFuncType)
	poly_func = cast(PolyFuncType, fun_ty)
	assert len(poly_func.params) == 0
	self.signature = poly_func.body

Also, the assert isinstance(fun_ty, PolyFuncType) will always fail since fun_ty is a Type, which can never contain a PolyFuncType.

[mark-koch]

Fixed by #982