Incorrect type recursion warning on assert

[joshua-cooper]

When using assert on an optional recursive type, the language server returns a warning.

For example:

---@alias Value string | Value[]

---@return Value?
function get_value() end

assert(get_value())

Gives me this diagnostic:

expected `(string|Value[])?` but found `(string|Value[])?`. type recursion [param-type-mismatch]

[CppCXY]

This is to prevent recursion. We cannot handle recursive definitions, so they are all treated as errors.

[joshua-cooper]

The type checking does seem to work fine without the assert though.

For example, this has no warnings:

---@alias Value string | Value[]

---@return Value
function get_value_1()
	return "string"
end

---@return Value
function get_value_2()
	return { "array" }
end

local value_1 = get_value_1()
local value_2 = get_value_2()

print(value_1)
print(value_2)

And this does have a (correct) return-type-mismatch warning:

---@alias Value string | Value[]

---@return Value
function get_value()
	return { 1 }
end

local value = get_value()

print(value)

Both cases will return that type recursion warning if I assert any of the value variables.

[joshua-cooper]

I can also narrow the types manually using if without getting warnings.

---@alias Value string | Value[]

---@return Value?
function get_value() end

local value = get_value()

if not value then
	error("no value")
end

-- Narrowed to (string|Value[]) here.
print(value)