Generics Super Issue

[carsakiller]

This "super issue" serves to organize and track all the issues relating to the implementation of generics.

Some of the following issues are likely duplicates, so some may just need to be marked duplicate and linked to other issues.

• [Feature request] generics in overload #723
• Support for generic classes #734
• Problem with generics #911
• Returning generics with T<X, Y> #1000
• feature: support generics in function type format #1170
• generic inheritance does not work #1272
• [Question] Prefixing/modifying a generic to get a different class #1322
• Cannot infer value type #1341
• How do I document a generic class (JS Promises) #1532
• Recursive expansion on hover of generic type #1853
• Generic class instanced in function should return as a concrete type #1856
• Generic Class Inheritance #1863
• Type inferencing of filter style functions #1883
• cannot extend generic class  #1929
• Allow to set named fields for generic class #1935

[bandaloo]

thanks for putting all these in one place. i found some more edge cases; maybe some of them are listed here already but i'll try to document them more diligently.

[jakitliang]

When will it get done?

[tmillr]

Here's another issue with generics that I don't believe has been documented yet?

---@class A
---@field k string

---@generic T: A
---@param p1 T
function f(p1) local m = p1.k end

^^^ here p1 should have a type of A within the function, but it doesn't, therefore m receives the type unknown

[checkraisefold]

Here's another issue with generics that I don't believe has been documented yet?

---@class A
---@field k string

---@generic T: A
---@param p1 T
function f(p1) local m = p1.k end

^^^ here p1 should have a type of A within the function, but it doesn't, so m receives the type unknown

This is odd since this use case works but you have to use the parameter capture for the generic to get its type and it also only works with base Lua types and not custom classes
see #2355 description

[tmillr]

Here's another issue with generics that I don't believe has been documented yet?

---@class A
---@field k string

---@generic T: A
---@param p1 T
function f(p1) local m = p1.k end

^^^ here p1 should have a type of A within the function, but it doesn't, so m receives the type unknown

This is odd since this use case works but you have to use the parameter capture for the generic to get its type and it also only works with base Lua types and not custom classes see #2355 description

I wouldn't really consider that to be "working". Passing strings at runtime just to get the LSP to work correctly is awkward. In theory this should be an easy fix, as the concrete type is literally right there and apart of the function's signature. It's not much different than getting/substituting the type of a concrete @param, there's just an extra layer of indirection (i.e. p1 -> T -> A instead of p1 -> T).

[checkraisefold]

Here's another issue with generics that I don't believe has been documented yet?

---@class A
---@field k string

---@generic T: A
---@param p1 T
function f(p1) local m = p1.k end

^^^ here p1 should have a type of A within the function, but it doesn't, so m receives the type unknown

This is odd since this use case works but you have to use the parameter capture for the generic to get its type and it also only works with base Lua types and not custom classes see #2355 description

I wouldn't really consider that to be "working". Passing strings at runtime just to get the LSP to work correctly is awkward. In theory this should be an easy fix, as the concrete type is literally right there and apart of the function's signature. It's not much different than getting/substituting the type of a concrete @param, there's just an extra layer of indirection (i.e. p1 -> T -> A instead of p1 -> T).

Oh yeah, definitely not "working" per se but very odd that it works with strings and only base Lua types. I would think it would literally be easier to implement the other way code wise

[AserJoker]

how to implement like

//  typescript interface
interface A<T>{
next<K>(callback:(value:T)=>K):A<K>;
};

or not support now