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Merged
hishamhm merged 2 commits into from
Aug 26, 2026
Merged

compat: shadow numeric for control variables on 5.4+ #1165

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c7feb6d
compat: shadow numeric for control variables on 5.4+
JJH090501 Aug 26, 2026
d534e5f
compat: test numeric for control variable shadowing
JJH090501 Aug 26, 2026
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97 changes: 97 additions & 0 deletions spec/lang/code_gen/fornum_spec.lua
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Original file line number Diff line number Diff line change
@@ -0,0 +1,97 @@
local util = require("spec.util")

describe("fornum", function()
it("5.3: doesn't generate control variable that is local to the iteration", util.gen([[
local t: {string} = { "a", "b", "c" }

for i = 1, #t do
i = i + 1
print(t[i])
end
]], [[
local t = { "a", "b", "c" }

for i = 1, #t do
i = i + 1
print(t[i])
end
]], "5.3"))

it("5.4: generates control variable that is local to the iteration", util.gen([[
local t: {string} = { "a", "b", "c" }

for i = 1, #t do
i = i + 1
print(t[i])
end
]], [[
local t = { "a", "b", "c" }

for i = 1, #t do local i = i
i = i + 1
print(t[i])
end
]], "5.4"))

it("5.4: does not generate control variable if not assigned to", util.gen([[
local t: {string} = { "a", "b", "c" }

for i = 1, #t do
local j = i + 1
print(t[j])
end
]], [[
local t = { "a", "b", "c" }

for i = 1, #t do
local j = i + 1
print(t[j])
end
]], "5.4"))

it("5.4: generates control variable for a loop with a step", util.gen([[
for i = 10, 1, -2 do
i = i // 2
print(i)
end
]], [[
for i = 10, 1, -2 do local i = i
i = i // 2
print(i)
end
]], "5.4"))

it("5.4: detects an assignment made from a nested function", util.gen([[
for i = 1, 3 do
local function bump()
i = i + 1
end
bump()
print(i)
end
]], [[
for i = 1, 3 do local i = i
local function bump()
i = i + 1
end
bump()
print(i)
end
]], "5.4"))

it("5.4: only shadows the loops that are assigned to", util.gen([[
for i = 1, 3 do
for j = 1, 3 do
j = j + 1
print(i, j)
end
end
]], [[
for i = 1, 3 do
for j = 1, 3 do local j = j
j = j + 1
print(i, j)
end
end
]], "5.4"))
end)
54 changes: 36 additions & 18 deletions teal.lua
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Original file line number Diff line number Diff line change
Expand Up @@ -236,6 +236,7 @@ local parse_typeargs_if_any






local ast = {}
Expand Down Expand Up @@ -8486,7 +8487,14 @@ visit_node.cbs = {
"number"
self:add_var(node.var, node.var.tk, a_type(node.var, typename, {}))
end,
after = end_scope_and_none_type,
after = function(self, node, _children)
local var = self:find_var(node.var.tk)
if var and var.has_been_written_to then
node.fornum_modifies_control_var = true
end
self:end_scope(node)
return NONE
end,
},
["return"] = {
before = function(self, node)
Expand Down Expand Up @@ -11154,6 +11162,25 @@ local bit_operators = {
["<<"] = "lshift",
}


local function shadow_control_var(node, control_var)
if #node.body == 0 then
return
end
local stmt = node_at(node, {
kind = "local_declaration",
vars = node_at(node, {
kind = "variable_list",
node_at(node, { kind = "variable", is_lvalue = true, tk = control_var }),
}),
exps = node_at(node, {
kind = "expression_list",
node_at(node, { kind = "variable", tk = control_var }),
}),
})
table.insert(node.body, 1, stmt)
end

local function adjust_code(ast, needs_compat, gen_compat, gen_target)
local visit = false

Expand Down Expand Up @@ -11283,24 +11310,15 @@ local function adjust_code(ast, needs_compat, gen_compat, gen_target)
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 loc_at = node
local stmt = node_at(loc_at, {
kind = "local_declaration",
vars = node_at(loc_at, {
kind = "variable_list",
node_at(loc_at, { kind = "variable", is_lvalue = true, tk = control_var }),
}),
exps = node_at(loc_at, {
kind = "expression_list",
node_at(loc_at, { kind = "variable", tk = control_var }),
}),
})
table.insert(node.body, 1, stmt)
shadow_control_var(node, node.vars[1].tk)
end
end,
}
visit_node.cbs["fornum"] = {
after = function(_, node, _children)
if node.fornum_modifies_control_var then
shadow_control_var(node, node.var.tk)
end
end,
}
Expand Down
1 change: 1 addition & 0 deletions teal/ast.lua
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Original file line number Diff line number Diff line change
Expand Up @@ -234,6 +234,7 @@ local parse_typeargs_if_any






local ast = {}
Expand Down
1 change: 1 addition & 0 deletions teal/ast.tl
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Original file line number Diff line number Diff line change
Expand Up @@ -162,6 +162,7 @@ local record Node
from: Node
to: Node
step: Node
fornum_modifies_control_var: boolean

-- forin
vars: Node
Expand Down
9 changes: 8 additions & 1 deletion teal/check/visitors.lua
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Original file line number Diff line number Diff line change
Expand Up @@ -1217,7 +1217,14 @@ visit_node.cbs = {
"number"
self:add_var(node.var, node.var.tk, a_type(node.var, typename, {}))
end,
after = end_scope_and_none_type,
after = function(self, node, _children)
local var = self:find_var(node.var.tk)
if var and var.has_been_written_to then
node.fornum_modifies_control_var = true
end
self:end_scope(node)
return NONE
end,
},
["return"] = {
before = function(self, node)
Expand Down
9 changes: 8 additions & 1 deletion teal/check/visitors.tl
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Original file line number Diff line number Diff line change
Expand Up @@ -1217,7 +1217,14 @@ visit_node.cbs = {
or "number"
self:add_var(node.var, node.var.tk, a_type(node.var, typename, {}))
end,
after = end_scope_and_none_type,
after = function(self: Context, node: Node, _children: {Type}): Type
local var = self:find_var(node.var.tk)
if var and var.has_been_written_to then
node.fornum_modifies_control_var = true
end
self:end_scope(node)
return NONE
end,
},
["return"] = {
before = function(self: Context, node: Node)
Expand Down
44 changes: 27 additions & 17 deletions teal/gen/lua_compat.lua
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Original file line number Diff line number Diff line change
Expand Up @@ -117,6 +117,25 @@ local bit_operators = {
["<<"] = "lshift",
}


local function shadow_control_var(node, control_var)
if #node.body == 0 then
return
end
local stmt = node_at(node, {
kind = "local_declaration",
vars = node_at(node, {
kind = "variable_list",
node_at(node, { kind = "variable", is_lvalue = true, tk = control_var }),
}),
exps = node_at(node, {
kind = "expression_list",
node_at(node, { kind = "variable", tk = control_var }),
}),
})
table.insert(node.body, 1, stmt)
end

local function adjust_code(ast, needs_compat, gen_compat, gen_target)
local visit = false

Expand Down Expand Up @@ -246,24 +265,15 @@ local function adjust_code(ast, needs_compat, gen_compat, gen_target)
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 loc_at = node
local stmt = node_at(loc_at, {
kind = "local_declaration",
vars = node_at(loc_at, {
kind = "variable_list",
node_at(loc_at, { kind = "variable", is_lvalue = true, tk = control_var }),
}),
exps = node_at(loc_at, {
kind = "expression_list",
node_at(loc_at, { kind = "variable", tk = control_var }),
}),
})
table.insert(node.body, 1, stmt)
shadow_control_var(node, node.vars[1].tk)
end
end,
}
visit_node.cbs["fornum"] = {
after = function(_, node, _children)
if node.fornum_modifies_control_var then
shadow_control_var(node, node.var.tk)
end
end,
}
Expand Down
44 changes: 27 additions & 17 deletions teal/gen/lua_compat.tl
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -117,6 +117,25 @@ local bit_operators: {string:string} = {
["<<"] = "lshift",
}

-- shadow var function
local function shadow_control_var(node: Node, control_var: string)
if #node.body == 0 then
return
end
local stmt = node_at(node, {
kind = "local_declaration",
vars = node_at(node, {
kind = "variable_list",
node_at(node, { kind = "variable", is_lvalue = true, tk = control_var }),
}),
exps = node_at(node, {
kind = "expression_list",
node_at(node, { kind = "variable", tk = control_var }),
}),
})
table.insert(node.body, 1, stmt)
end

local function adjust_code(ast: Node, needs_compat: {string:boolean}, gen_compat: GenCompat, gen_target: string)
local visit = false

Expand Down Expand Up @@ -246,24 +265,15 @@ local function adjust_code(ast: Node, needs_compat: {string:boolean}, gen_compat
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 loc_at = node
local stmt = node_at(loc_at, {
kind = "local_declaration",
vars = node_at(loc_at, {
kind = "variable_list",
node_at(loc_at, { kind = "variable", is_lvalue = true, tk = control_var }),
}),
exps = node_at(loc_at, {
kind = "expression_list",
node_at(loc_at, { kind = "variable", tk = control_var }),
}),
})
table.insert(node.body, 1, stmt)
shadow_control_var(node, node.vars[1].tk)
end
end,
}
visit_node.cbs["fornum"] = {
after = function(_: nil, node: Node, _children: {nil}): nil
if node.fornum_modifies_control_var then
shadow_control_var(node, node.var.tk)
end
end,
}
Expand Down
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