通用Lua运行时是否优化表查找？

Question

Can tables used like namespaces expand their fields before running, to avoid indexing tables ? I plan to use Lua's 5.3.3 compiler. For example:

local Types = {
    A = 1,
    B = 2,
    C = 3
};

print(Types.A);

Could this turn into:

print(1);

or something like (but probably better):

local A = 1;
print(A);

directly?

Answer 1

No, Lua will run the code as is. That's the cost of compiler's simplicity.
See the output from luac :

main <2.lua:0,0> (8 instructions at 0x235bb10)
0+ params, 3 slots, 1 upvalue, 1 local, 7 constants, 0 functions
    1   [1] NEWTABLE    0 0 3
    2   [2] SETTABLE    0 -1 -2 ; "A" 1
    3   [3] SETTABLE    0 -3 -4 ; "B" 2
    4   [4] SETTABLE    0 -5 -6 ; "C" 3
    5   [7] GETTABUP    1 0 -7  ; _ENV "print"
    6   [7] GETTABLE    2 0 -1  ; "A"
    7   [7] CALL        1 2 1
    8   [7] RETURN      0 1

Answer 2

You can set Types as a temporary table to resolve global names:

local Types = {
    A = 1,
    B = 2,
    C = 3
}

do
    local print = print
    local _ENV = Types
    print(A)
end

But do ponder on why you want this. Note the need for saving print before setting _ENV .