return diagnostics are inaccurate or I use it wrongly

[dkuettel]

Hi,

I don't manage to get accurate diagnostics when enforcing return types, consider these examples:

---@return integer result
local function test1()
    return 12
end

---@return integer result
local function test2()
    return 12.3
end

---@return integer result
local function test3()
    return "test"  -- this is the only one that triggers a diagnostic
end

---@return {value: integer} result
local function test4()
    return { value = "test" }
end

---@return {value: integer} result
local function test5()
    return { wrong = "test" }
end

As noted, only the string instead of integer gives a diagnostics. All others pass for me. Especially I can't make it check my table returns to validate keys and types.

Any ideas?

Cheers, Daniel.

[tomlau10]

For the 2nd case, there is a type.castNumberToInteger config which allowing assigning number to integer type.
https://luals.github.io/wiki/settings/#typecastnumbertointeger
It defaults to true as opposed to what stated on the wiki though.

---@return integer result
local function test2()
    return 12.3 --[[
Annotations specify that return value #1 has a type of `integer`, returning value of type `number` here instead.
- `number` cannot match `integer`
- The number `12.3` cannot be converted to an integer
]]
end

---

For the table type checking I am not sure 😕
However I do know that there is an undocumented type.checkTableShape config (default to false) which will check table type if the required type is defined as @class, not just literal table doc:

--- enable in your config, "type.checkTableShape": true

---@class test.ret
---@field value integer

---@return test.ret result
local function test4()
    return { value = "" } --[[
    Annotations specify that return value #1 has a type of `test.ret`, returning value of type `table` here instead.
    - `table` cannot match `test.ret`
    - `string` cannot match any subtypes in `integer`
    - `string` cannot match `integer`
    - Type `string` cannot match `integer`
    ]]
end

---@return test.ret result
local function test5()
    return { wrong = "test" } --[[
    Annotations specify that return value #1 has a type of `test.ret`, returning value of type `table` here instead.
    - `table` cannot match `test.ret`
    - Missing required fields in type `test.ret`: "`value`"
    ]]
end

=> this way will have warnings 🤔

---

a similar issue reported: #2802 (comment)