Caching last used table index

["Soni \"They/Them\" L." <fakedme@...>]

I often write code like:

local foo = t.foo
if not foo then foo = whatever t.foo = foo end
-- use foo here

but ideally I'd like to write it like:

if not t.foo then t.foo = whatever end
local foo = t.foo

and still have the same performance (or better).

does lua do any optimizations related to this?