Type checker widens number into number? when multiple assignment is involved with a function call

[melindatrace]

I expect variable b to remain number in all three function variants (fa, fb, and fc).

--!strict

local function n(x: number): number return x end

local function fa(x: number): (number, number)
	local a, b = 0, 0
	for i = 1, x do
		a, b = x, n(b * a)
	end
	return a, b -- number, number?
end

local function fb(x: number): (number, number)
	local a, b = 0, 0
	for i = 1, x do
		a = x
		b = n(b * a)
	end
	return a, b -- number, number
end

local function fc(x: number): (number, number)
	local a, b = 0, 0
	for i = 1, x do
		a, b = x, b * a
	end
	return a, b -- number, number
end

Luau 0.703 (new solver)