check: named vararg table is <const>

Fixes #1160

Author: hishamhm

spec/lang/declaration/local_function_spec.lua

@@ -129,7 +129,7 @@ describe("local function", function()
       ]]))
    end)
 
-   describe("Lua 5.5 named variadic arguments", function()
+   describe("Lua 5.5-style named variadic arguments", function()
       it("works in a type annotation", util.check([[
          local _: function(a: integer, ...b: integer)
       ]]))
@@ -166,6 +166,16 @@ describe("local function", function()
 
          f(1, 2, 3, 4)
       ]])
+
+      it("the named vararg table is <const>", util.check_type_error([[
+         local function test(...args: boolean): integer, boolean
+            args[1] = false
+            args = { true }
+            return args.n, args[1]
+         end
+      ]], {
+         { y = 3, msg = "cannot assign to <const> variable" }
+      }))
    end)
 
    it("declaration", util.check([[

teal.lua

@@ -9597,7 +9597,7 @@ visit_node.cbs = {
                local generic_pack_table = (table_t.fields["PackTable"]).def
                local pack_table = self:apply_generic(node, generic_pack_table, { t })
 
-               self:add_var(node, node.name.tk, pack_table).is_func_arg = true
+               self:add_var(node, node.name.tk, pack_table, "const").is_func_arg = true
                is_named_vararg = true
             end
             t = a_vararg(node, { t })

teal/check/visitors.lua

@@ -2328,7 +2328,7 @@ visit_node.cbs = {
                local generic_pack_table = (table_t.fields["PackTable"]).def
                local pack_table = self:apply_generic(node, generic_pack_table, { t })
 
-               self:add_var(node, node.name.tk, pack_table).is_func_arg = true
+               self:add_var(node, node.name.tk, pack_table, "const").is_func_arg = true
                is_named_vararg = true
             end
             t = a_vararg(node, { t })

teal/check/visitors.tl

@@ -2328,7 +2328,7 @@ visit_node.cbs = {
                local generic_pack_table <const> = (table_t.fields["PackTable"] as types.TypeDeclType).def as types.GenericType
                local pack_table <const> = self:apply_generic(node, generic_pack_table, { t })
 
-               self:add_var(node, node.name.tk, pack_table).is_func_arg = true
+               self:add_var(node, node.name.tk, pack_table, "const").is_func_arg = true
                is_named_vararg = true
             end
             t = a_vararg(node, { t })

tl.lua

@@ -9851,7 +9851,7 @@ visit_node.cbs = {
                local generic_pack_table = (table_t.fields["PackTable"]).def
                local pack_table = self:apply_generic(node, generic_pack_table, { t })
 
-               self:add_var(node, node.name.tk, pack_table).is_func_arg = true
+               self:add_var(node, node.name.tk, pack_table, "const").is_func_arg = true
                is_named_vararg = true
             end
             t = a_vararg(node, { t })