Incorrect inference with nested table literal with union types

[ghost]

--!strict
type path = {[string]: {string?}}
local path_map: {[string]: path?} = {
	["outermost"] = {
		["exterior"] = {
			"first interior", -- This is incorrectly inferred as `string` instead of `string?`, and will warn.
			"second interior",
			"third interior",
		}
	}
}

Type Error: (3,1) Type 'path_map' could not be converted into '{| [string]: path? |}'
caused by:
  Property 'outermost' is not compatible. Type 'path?' could not be converted into '{ exterior: {string} }'
caused by:
  Not all union options are compatible. Type 'path' could not be converted into '{ exterior: {string} }'
caused by:
  Property 'exterior' is not compatible. Type '{string?}' could not be converted into '{string}'
caused by:
  Property '[indexer value]' is not compatible. Type 'string?' could not be converted into 'string'

As a workaround, "first interior" must be casted to string?, but "second interior" and "third interior" do not need to be casted.

--!strict
type path = {[string]: {string?}}
local path_map: {[string]: path?} = {
	["outermost"] = {
		["exterior"] = {
			"first interior" :: string?,
			"second interior",
			"third interior",
		}
	}
}

Another workaround is to define the path beforehand.

--!strict
type path = {[string]: {string?}}
local path: path = {
	["exterior"] = {
		"first interior",
		"second interior",
		"third interior",
	}
}
local path_map: {[string]: path?} = {
	["outermost"] = path,
}

If path_map has type {[string]: path}, this will not occur.

--!strict
type path = {[string]: {string?}}
local path_map: {[string]: path} = {
	["outermost"] = {
		["exterior"] = {
			"first interior",
			"second interior",
			"third interior",
		}
	}
}