Point incompatible override error to argument rather than method header

[dhalenok]

Possibly closes #8298.

[dhalenok]

@JukkaL

While I was working on #8298, I've stumbled upon a different issue: arguments always had the same line as the FuncDef.

I've tracked it down to this method in FuncItem:

mypy/mypy/nodes.py

Lines 627 to 633 in 83012da

	def set_line(self,
	target: Union[Context, int],
	column: Optional[int] = None,
	end_line: Optional[int] = None) -> None:
	super().set_line(target, column, end_line)
	for arg in self.arguments:
	arg.set_line(self.line, self.column, self.end_line)

Which gets called while parsing FuncDef:

mypy/mypy/fastparse.py

Line 621 in 83012da

func_def.set_line(lineno, n.col_offset, end_lineno)

This was basically always overwriting arg's line.

However, removing

mypy/mypy/nodes.py

Lines 632 to 633 in 83012da

	for arg in self.arguments:
	arg.set_line(self.line, self.column, self.end_line)

didn't completely solve the problem. At this point, the argument's line was always -1.
I've modified make_argument (in fastparse.py) by creating the argument variable and calling set_line on it before returning it.

[ethanhs]

This doesn't seem quite right. It seems that you are passing this to forward the correct context, but 1) you are passing the next argument as context? 2) arguments aren't contexts. You probably want to make sure the context is set correctly to begin with.

[97littleleaf11]

Thanks for your PR! But I'm going to close it due to inactive status. Feel free to reopen it if you still work on this!