fix: suppress undefined-doc-name warning for class generic parameters

When a generic class like Container<T> has methods that use T in their
annotations (e.g., @return T[]), the diagnostic was incorrectly warning
about T being undefined.

Added isClassGenericParam() function that checks:
1. bindGroup for inline class/alias with matching generic signs
2. Direct class reference for doc.field, doc.overload, doc.operator
3. Method binding via vm.getDefinedClass for methods on generic classes

Addresses maintainer feedback on PR #3330.

Author: ian-pascoe

script/core/diagnostics/undefined-doc-name.lua

@@ -3,6 +3,96 @@ local guide   = require 'parser.guide'
 local lang    = require 'language'
 local vm      = require 'vm'
 
+--- Check if name is a generic parameter from a class context
+---@param source parser.object  The doc.type.name source
+---@param name string  The type name to check
+---@param uri uri  The file URI
+---@return boolean
+local function isClassGenericParam(source, name, uri)
+    -- Find containing doc node
+    local doc = guide.getParentTypes(source, {
+        ['doc.return'] = true,
+        ['doc.param'] = true,
+        ['doc.type'] = true,
+        ['doc.field'] = true,
+        ['doc.overload'] = true,
+        ['doc.vararg'] = true,
+    })
+    if not doc then
+        return false
+    end
+
+    -- Walk up to find a doc node with bindGroup (intermediate doc.type nodes don't have it)
+    while doc and not doc.bindGroup do
+        doc = doc.parent
+    end
+    if not doc then
+        return false
+    end
+
+    -- Check bindGroup for class/alias with matching generic sign
+    local bindGroup = doc.bindGroup
+    if bindGroup then
+        for _, other in ipairs(bindGroup) do
+            if (other.type == 'doc.class' or other.type == 'doc.alias') and other.signs then
+                for _, sign in ipairs(other.signs) do
+                    if sign[1] == name then
+                        return true
+                    end
+                end
+            end
+        end
+    end
+
+    -- Check direct class reference (for doc.field, doc.overload, doc.operator)
+    if doc.class and doc.class.signs then
+        for _, sign in ipairs(doc.class.signs) do
+            if sign[1] == name then
+                return true
+            end
+        end
+    end
+
+    -- Check if bound to a method on a generic class
+    -- First, find the function from any doc in the bindGroup
+    local func = nil
+    if bindGroup then
+        for _, other in ipairs(bindGroup) do
+            local bindSource = other.bindSource
+            if bindSource then
+                if bindSource.type == 'function' then
+                    func = bindSource
+                    break
+                elseif bindSource.parent and bindSource.parent.type == 'function' then
+                    func = bindSource.parent
+                    break
+                end
+            end
+        end
+    end
+
+    -- If we found a function, check if it's a method on a generic class
+    if func and func.parent then
+        local parent = func.parent
+        if parent.type == 'setmethod' or parent.type == 'setfield' or parent.type == 'setindex' then
+            local classGlobal = vm.getDefinedClass(uri, parent.node)
+            if classGlobal then
+                for _, set in ipairs(classGlobal:getSets(uri)) do
+                    if set.type == 'doc.class' and set.signs then
+                        for _, sign in ipairs(set.signs) do
+                            if sign[1] == name then
+                                return true
+                            end
+                        end
+                    end
+                end
+            end
+        end
+    end
+
+    return false
+end
+
 return function (uri, callback)
     local state = files.getState(uri)
     if not state then
@@ -25,6 +115,9 @@ return function (uri, callback)
         if name == '...' or name == '_' or name == 'self' then
             return
         end
+        if isClassGenericParam(source, name, uri) then
+            return
+        end
         if #vm.getDocSets(uri, name) > 0 then
             return
         end

test/diagnostics/undefined-doc-name.lua

@@ -17,3 +17,42 @@ TEST [[
 TEST [[
 ---@alias B <!AAA!>
 ]]
+
+-- Generic class methods should not warn about class generic params
+TEST [[
+---@class Container<T>
+local Container = {}
+
+---@return T[]
+function Container:getAll()
+    return {}
+end
+]]
+
+-- Inline class fields with generics should not warn
+TEST [[
+---@class Box<T>
+---@field value T
+]]
+
+-- Multiple generic params should all be recognized
+TEST [[
+---@class Map<K, V>
+local Map = {}
+
+---@param key K
+---@return V
+function Map:get(key)
+end
+]]
+
+-- Undefined types SHOULD still warn (control case)
+TEST [[
+---@class Container<T>
+local Container = {}
+
+---@return <!UndefinedType!>
+function Container:getBad()
+    return {}
+end
+]]