first local of for .. in can not be nil

Author: sumneko

script/vm/compiler.lua

@@ -1228,6 +1228,9 @@ local compilerSwitch = util.switch()
             for i, loc in ipairs(source.keys) do
                 local node = getReturn(source._iterator, i, source._iterArgs)
                 if node then
+                    if i == 1 then
+                        node:removeOptional()
+                    end
                     vm.setNode(loc, node)
                 end
             end

test/type_inference/init.lua

@@ -2048,3 +2048,11 @@ end
 
 print(<?x?>)
 ]]
+
+TEST 'integer' [[
+---@type fun():integer?
+local iter
+
+for <?x?> in iter do
+end
+]]