Metamethod __lt, __eq, __le show an error when not provided identical types

[CoderJoey (Joey)]

Metamethod __lt, __eq, __le show an error when not provided identical types even though the type implementation in the metatable allows for differing types.

Should allow for differing types. Our use case is a Big Integer class.

[Kampfkarren (boyned)]

Luau doesn’t support this. In order to compare two objects they need to have the same metatable method.

local x = setmetatable({}, {
	__lt = print,
})

local _ = x < x -- Will print something
local _ = x < 3 -- Error: attempt to compare table < number

[CoderJoey (Joey)]

Clearly. I am asking for support for it. The VM itself DOES support this behavior, however it is being incorrectly shown as an error in studio.

[Kampfkarren (boyned)]

That error is from the runtime. Check again.

The error Luau gives you also explains this:

The wiki as well:

[CoderJoey (Joey)]

You are correct, this is an error in runtime. Unfortunate.

--!strict

export type metatable_schema = {
	__eq: (self: schema, operand: schema | Vector2) -> boolean,
	__lt: (self: schema, operand: schema | Vector2) -> boolean,
	__le: (self: schema, operand: schema | Vector2) -> boolean,
}

export type raw_schema = {
	X: number,
	Y: number,
}

export type schema = typeof(setmetatable({}::raw_schema, {}::metatable_schema))

local metatable = {}

function metatable.__eq(self: schema, operand: schema | Vector2): boolean
	return self.X == operand.X and self.Y == operand.Y
end

function metatable.__lt(self: schema, operand: schema | Vector2): boolean
	return self.X * self.Y < operand.X * operand.Y
end

function metatable.__le(self: schema, operand: schema | Vector2): boolean
	return self.X * self.Y <= operand.X * operand.Y
end

function MyVector2(
	x: number,
	y: number
): schema
	return setmetatable({ X = x, Y = y }, metatable)
end

local a = Vector2.new(1, 2)
local b = MyVector2(1, 2)

pcall(function()
	print(b < a)
	print("b < a")
end)
pcall(function()
	print(b > a)
	print("b > a")
end)
pcall(function()
	print(b <= a)
	print("b <= a")
end)
pcall(function()
	print(b >= a)
	print("b >= a")
end)

pcall(function()
	print(a < b)
	print("a < b")
end)
pcall(function()
	print(a > b)
	print("a > b")
end)
pcall(function()
	print(a <= b)
	print("a <= b")
end)
pcall(function()
	print(a >= b)
	print("a >= b")
end)

pcall(function()
	print(a == b)
	print("a == b")
end)
pcall(function()
	print(b == a)
	print("b == a")
end)

return module