compat: Lua 5.3 semantics for control variables in Lua 5.4+

.github/workflows/ci.yml

@@ -10,7 +10,7 @@ jobs:
   Test:
     strategy:
       matrix:
-        lua-version: ["5.4", "5.3", "5.2", "5.1", "luajit"]
+        lua-version: ["5.5", "5.4", "5.3", "5.2", "5.1", "luajit"]
         os: ["ubuntu-latest"]
         include:
         - os: "macos-latest"

spec/lang/code_gen/forin_spec.lua

@@ -0,0 +1,67 @@
+local util = require("spec.util")
+
+describe("forin", function()
+   it("5.3: doesn't generate control variable that is local to the iteration", util.gen([[
+      local mypairs: function({string:string}): (function(string): (string, string))
+
+      local t: {string:string} = { k1 = "a", k2 = "b", k3 = "c" }
+
+      for k, v in mypairs(t) do
+         k = k .. "!"
+         print(k)
+         k = "yes"
+         print(k)
+      end
+   ]], [[
+      local mypairs
+
+      local t = { k1 = "a", k2 = "b", k3 = "c" }
+
+      for k, v in mypairs(t) do
+         k = k .. "!"
+         print(k)
+         k = "yes"
+         print(k)
+      end
+   ]], "5.3"))
+
+   it("5.4: generates control variable that is local to the iteration", util.gen([[
+      local t: {string:string} = { k1 = "a", k2 = "b", k3 = "c" }
+
+      for k, v in pairs(t) do
+         k = k .. "!"
+         print(k)
+         k = "yes"
+         print(k)
+      end
+   ]], [[
+      local t = { k1 = "a", k2 = "b", k3 = "c" }
+
+      for k, v in pairs(t) do local k = k
+         k = k .. "!"
+         print(k)
+         k = "yes"
+         print(k)
+      end
+   ]], "5.4"))
+
+   it("5.4: does not generate control variable if not assigned to", util.gen([[
+      local t: {string:string} = { k1 = "a", k2 = "b", k3 = "c" }
+
+      for k, v in pairs(t) do
+         local k2 = k .. "!"
+         print(k2)
+         k2 = "yes"
+         print(k2)
+      end
+   ]], [[
+      local t = { k1 = "a", k2 = "b", k3 = "c" }
+
+      for k, v in pairs(t) do
+         local k2 = k .. "!"
+         print(k2)
+         k2 = "yes"
+         print(k2)
+      end
+   ]], "5.4"))
+end)

teal/check/relations.lua

@@ -144,7 +144,7 @@ local function subtype_record(ck, a, b)
 
    if a.is_userdata ~= b.is_userdata then
       return false, { errors.new(a.is_userdata and "userdata is not a record" or
-"record is not a userdata"), }
+      "record is not a userdata"), }
    end
 
    local errs = {}
@@ -667,8 +667,8 @@ relations.subtype_relations = {
          for i = 1, math.min(#a.types, #b.types) do
             if not ck:is_a(a.types[i], b.types[i]) then
                return false, { types.error("in tuple entry " ..
-tostring(i) .. ": got %s, expected %s",
-a.types[i], b.types[i]), }
+               tostring(i) .. ": got %s, expected %s",
+               a.types[i], b.types[i]), }
             end
          end
          if #a.types > #b.types then

teal/check/visitors.lua

@@ -630,9 +630,9 @@ local function infer_table_literal(self, node, children)
    if is_array and is_map then
       self.errs:add(node, "cannot determine type of table literal")
       t = a_type(node, "map", { keys =
-self:expand_type(node, keys, a_type(node, "integer", {})), values =
+      self:expand_type(node, keys, a_type(node, "integer", {})), values =
 
-self:expand_type(node, values, elements) })
+      self:expand_type(node, values, elements) })
    elseif is_record and is_array then
       t = a_type(node, "record", {
          fields = fields,
@@ -1138,7 +1138,15 @@ visit_node.cbs = {
             end
          end
       end,
-      after = end_scope_and_none_type,
+      after = function(self, node, _children)
+         local control_var = node.vars[1]
+         local var = self:find_var(control_var.tk)
+         if var and var.has_been_written_to then
+            node.forin_modifies_control_var = true
+         end
+         self:end_scope(node)
+         return NONE
+      end,
    },
    ["fornum"] = {
       before_statements = function(self, node, children)

teal/check/visitors.tl

@@ -1138,7 +1138,15 @@ visit_node.cbs = {
             end
          end
       end,
-      after = end_scope_and_none_type,
+      after = function(self: Context, node: Node, _children: {Type}): Type
+         local control_var = node.vars[1]
+         local var = self:find_var(control_var.tk)
+         if var and var.has_been_written_to then
+            node.forin_modifies_control_var = true
+         end
+         self:end_scope(node)
+         return NONE
+      end
    },
    ["fornum"] = {
       before_statements = function(self: Context, node: Node, children: {Type})

teal/gen/lua_compat.lua

@@ -118,15 +118,14 @@ local bit_operators = {
 }
 
 local function adjust_code(ast, needs_compat, gen_compat, gen_target)
-   if gen_target == "5.4" then
-      return
-   end
+   local visit = false
 
    local visit_node = {
       cbs = {},
    }
 
-   if gen_compat ~= "off" then
+   if (gen_target == "5.1" or gen_target == "5.3") and gen_compat ~= "off" then
+      visit = true
       visit_node.cbs["op"] = {
          after = function(_, node, _children)
             if node.op.op == "is" then
@@ -174,6 +173,32 @@ local function adjust_code(ast, needs_compat, gen_compat, gen_target)
       }
    end
 
+   if gen_target == "5.4" then
+      visit = true
+      visit_node.cbs["forin"] = {
+         after = function(_, node, _children)
+            if #node.body == 0 then
+               return
+            end
+            if node.forin_modifies_control_var then
+               local control_var = node.vars[1].tk
+               local localization = parser.parse("local " .. control_var .. " = " .. control_var, "@<internal>.lua")
+               localization[1].y = node.y
+               localization[1].vars.y = node.y
+               localization[1].vars[1].y = node.y
+               localization[1].exps.y = node.y
+               localization[1].exps[1].y = node.y
+               table.insert(node.body, 1, localization[1])
+               node.body.y = node.y
+            end
+         end,
+      }
+   end
+
+   if not visit then
+      return
+   end
+
    traverse_nodes(nil, ast, visit_node, {})
 
    add_compat_entries(ast, needs_compat, gen_compat)

teal/gen/lua_compat.tl

@@ -118,15 +118,14 @@ local bit_operators: {string:string} = {
 }
 
 local function adjust_code(ast: Node, needs_compat: {string:boolean}, gen_compat: GenCompat, gen_target: string)
-   if gen_target == "5.4" then
-      return
-   end
+   local visit = false
 
    local visit_node: Visitor<nil, NodeKind, Node, nil> = {
       cbs = {}
    }
 
-   if gen_compat ~= "off" then
+   if (gen_target == "5.1" or gen_target == "5.3") and gen_compat ~= "off" then
+      visit = true
       visit_node.cbs["op"] = {
          after = function(_: nil, node: Node, _children: {nil}): nil
             if node.op.op == "is" then
@@ -174,6 +173,32 @@ local function adjust_code(ast: Node, needs_compat: {string:boolean}, gen_compat
       }
    end
 
+   if gen_target == "5.4" then
+      visit = true
+      visit_node.cbs["forin"] = {
+         after = function(_: nil, node: Node, _children: {nil}): nil
+            if #node.body == 0 then
+               return
+            end
+            if node.forin_modifies_control_var then
+               local control_var = node.vars[1].tk
+               local localization = parser.parse("local " .. control_var .. " = " .. control_var, "@<internal>.lua") as Node
+               localization[1].y = node.y
+               localization[1].vars.y = node.y
+               localization[1].vars[1].y = node.y
+               localization[1].exps.y = node.y
+               localization[1].exps[1].y = node.y
+               table.insert(node.body, 1, localization[1])
+               node.body.y = node.y
+            end
+         end,
+      }
+   end
+
+   if not visit then
+      return
+   end
+
    traverse_nodes(nil, ast, visit_node, {})
 
    add_compat_entries(ast, needs_compat, gen_compat)