Lua - Local variable scope in function

Question

I have the following function

function test()
 local function test2()
 print(a)
 end
 local a = 1
 test2()
end
test()

This prints out nil

The following script

local a = 1
function test()
 local function test2()
 print(a)
 end
 test2()
end
test()

prints out 1.

I do not understand this. I thought declaring a local variable makes it valid in its entire block. Since the variable 'a' is declared in the test()-function scope, and the test2()-function is declared in the same scope, why does not test2() have access to test() local variable?

• Etan Reisner: lua is not javascript, it does not "hoist" variables.

Answer 1

test2 has has access to variables which have already been declared. Order matters. So, declare a before test2:

function test()
 local a; -- same scope, declared first
 local function test2()
 print(a);
 end
 a = 1;
 test2(); -- prints 1
end
test();

• Keith Thompson: "The scope of a local variable begins at the first statement after its declaration and lasts until the last non-void statement of the innermost block that includes the declaration." -- lua.org/manual/5.3/manual.html#3.5
• tonypdmtr: Actually, only the 'local a' part needs to come first, as the value assigned to it may not be known yet. So, the assignment can still follow the definition of the inner function.
• canon: @tonypdmtr True, though that's why I said, "declared".

Answer 2

You get nil in the first example because no declaration for a has been seen when a is used and so the compiler declares a to be a global. Setting a right before calling test will work. But it won't if you declare a as local.