standard library: special-case tuple support for table.unpack

Add special cases for tuples of sizes up to 5.

spec/call/generic_function_spec.lua

@@ -494,9 +494,9 @@ describe("generic function", function()
    ]]))
 
    it("generic function definitions do not leak type variables (#322)", util.check([[
-      local function my_unpack<T>(_list: {T}, _x: number, _y: number): T...
+      local function my_move<T>(_list: {T}, _a: integer, _b: integer, _c: integer, _t?: {T}): {T}
       end
-      local _tbl_unpack = my_unpack or table.unpack
+      local _tbl_move = my_move or table.move
       local _map: {string:number} = setmetatable(assert({}), { __mode = "k" })
    ]]))
 

spec/stdlib/table_spec.lua

@@ -10,6 +10,18 @@ describe("table", function()
          local b = b as string
          local c = c as number
       ]]))
+
+      -- standard library definition has special cases
+      -- for tuples of sizes up to 5
+      it("can unpack some tuples", util.check([[
+         local s = { 1234, "5678", 4566, "foo", 123 }
+         local a, b, c, d, e = table.unpack(s)
+         a = a + 1 -- number
+         b = b .. "!" -- string
+         c = c + 2 -- number
+         d = d .. "!" -- string
+         e = e + 3 -- number
+      ]]))
    end)
 
    describe("concat", function()

tl.lua

@@ -353,6 +353,10 @@ do
       remove: function<A>({A}, ? integer): A
       sort: function<A>({A}, ? SortFunction<A>)
 
+      unpack: function<A1, A2, A3, A4, A5>({A1, A2, A3, A4, A5}): A1, A2, A3, A4, A5 --[[needs_compat]]
+      unpack: function<A1, A2, A3, A4>({A1, A2, A3, A4}): A1, A2, A3, A4 --[[needs_compat]]
+      unpack: function<A1, A2, A3>({A1, A2, A3}): A1, A2, A3 --[[needs_compat]]
+      unpack: function<A1, A2>({A1, A2}): A1, A2 --[[needs_compat]]
       unpack: function<A>({A}, ? number, ? number): A... --[[needs_compat]]
    end
 

tl.tl

@@ -353,6 +353,10 @@ do
       remove: function<A>({A}, ? integer): A
       sort: function<A>({A}, ? SortFunction<A>)
 
+      unpack: function<A1, A2, A3, A4, A5>({A1, A2, A3, A4, A5}): A1, A2, A3, A4, A5 --[[needs_compat]]
+      unpack: function<A1, A2, A3, A4>({A1, A2, A3, A4}): A1, A2, A3, A4 --[[needs_compat]]
+      unpack: function<A1, A2, A3>({A1, A2, A3}): A1, A2, A3 --[[needs_compat]]
+      unpack: function<A1, A2>({A1, A2}): A1, A2 --[[needs_compat]]
       unpack: function<A>({A}, ? number, ? number): A... --[[needs_compat]]
    end