[New Solver] fails to track type state of explicitly assigned properties

[OverHash]

Consider this code example:

type Item = {
	specialAttributes: { string }?
}

local myItem: Item = {}
myItem.specialAttributes = {}
table.freeze(myItem.specialAttributes) -- errors!

This produces a type error today:

TypeError: Type '{string}?' could not be converted into '{-  -}'

this error is clearly wrong -- we have explicitly defined myItem.specialAttributes, and so it's not possible for it to be {string}? -- it would now be {string}.

Note that in my case, myItem was sourced after iterating over a table, and so the specialAttributes assignment (and freeze) occurs inside the loop. There are obvious workarounds (like using table.freeze to wrap the assignment), but the core issue remains.

[OverHash]

Note: this might be a dupe of #1970, but I'm not sure that it's exactly the same.