arity error with the return of table.unpack

[fperrad]

local function foo (a: string, b: string, c: string, d:string, e?: string)
   print(a, b, c, d, e)
end

local t = { 'a', 'b', 'c', 'd' }
assert(#t >= 4)
foo(table.unpack(t))  -- ERROR: wrong number of arguments (given 2, expects at least 4 and at most 5)

foo('bar', table.unpack(t))  -- ERROR: wrong number of arguments (given 3, expects at least 4 and at most 5)

note: #pragma arity on/off is a workaround.

[fperrad]

After more thinking, it is not an issue. I miss a cast.

foo(table.unpack(t) as (string, string, string, string))

But it could be nice to add in the doc/manual a list of functions that their return usually need a cast.

• pcall
• string.match
• string.unpack
• table.unpack
• ...

[catwell]

Note that this also works:

local t: {string, string, string, string} = { 'a', 'b', 'c', 'd' }
foo(table.unpack(t))

This makes me think about a few improvements that could be made to tuples, I will open a discussion thread for this.