fix: consider varargs the same as tableexp for iterating (#2906)

Co-authored-by: Tom Lau <tomandfatboy@gmail.com>

changelog.md

@@ -3,6 +3,7 @@
 ## Unreleased
 <!-- Add all new changes here. They will be moved under a version at release -->
 * `FIX` A regression related to type narrow and generic param introduced since `v3.10.1`
+* `FIX` Determine that the index of `{...}` is an integer when iterating
 
 ## 3.11.1
 `2024-10-9`

script/vm/type.lua

@@ -721,7 +721,7 @@ function vm.getTableKey(uri, tnode, vnode, reverse)
                 if field.type == 'tablefield' then
                     result:merge(vm.declareGlobal('type', 'string'))
                 end
-                if field.type == 'tableexp' then
+                if field.type == 'tableexp' or field.type == 'varargs' then
                     result:merge(vm.declareGlobal('type', 'integer'))
                 end
             end

test/type_inference/common.lua

@@ -4591,3 +4591,11 @@ local function f(v) end
 
 local <?r?> = f('')
 ]]
+
+TEST 'integer' [[
+local function F(...)
+    local t = {...}
+    for <?k?> in pairs(t) do
+    end
+end
+]]