Defining a function type as parameter

[ogsadmin]

Hi,

I am struggling to correctly define/annotate a callback function - I've searched the web (and here), but I did not find any way to define a function including its parameter annotations, then use this as part of another functions parameter.

Here is what is working:

---@alias CallbackFunctionType fun(p1 : string, p2 : string) : string

---Register a callback function
---@param callback CallbackFunctionType Function to be registered
function RegisterCallback(callback) end

However, this does not provide full parameter information (i.e. the individual parameter descriptions) when doing code completion or code hints for the RegisterCallback function. So I was trying to define the function normally, then use it as a type:

---This function is called whenever the condition is met, register it through RegisterCallback()
---@param p1 string first parameter
---@param p2 string second parameter
---@return string result Result string
function CallbackFunction(p1, p2) 
end

---Register a callback function
---@param callback CallbackFunction Function to be registered
function RegisterCallback(callback) end

This is (obviously) not working, as CallbackFunction is not a type - so it can't be used in the parameter list of the RegisterCallback function. But this describes the use case I have...

Here is what I can see in VSCode for the above try:

Any hint on how function parameters with full annotations can be defined would be highly appreciated!