fix incorrect type check for generic with nil

Author: sumneko

changelog.md

@@ -1,7 +1,9 @@
 # changelog
 
 ## 3.6.2
+* `FIX` incorrect type check for generic with nil
 * `FIX` [#1676]
+
 [#1676]: https://github.com/sumneko/lua-language-server/issues/1676
 
 ## 3.6.1

script/vm/generic.lua

@@ -36,11 +36,12 @@ local function cloneObject(source, resolved)
     end
     if source.type == 'doc.type' then
         local newType = {
-            type   = source.type,
-            start  = source.start,
-            finish = source.finish,
-            parent = source.parent,
-            types  = {},
+            type     = source.type,
+            start    = source.start,
+            finish   = source.finish,
+            parent   = source.parent,
+            optional = source.optional,
+            types    = {},
         }
         for i, typeUnit in ipairs(source.types) do
             local newObj     = cloneObject(typeUnit, resolved)

script/vm/type.lua

@@ -355,6 +355,9 @@ function vm.isSubType(uri, child, parent, mark, errs)
                     return true
                 end
             end
+            if n.type == 'doc.generic.name' then
+                return true
+            end
         end
         if parent:isOptional() then
             if vm.isSubType(uri, child, 'nil', mark, errs) == true then

test/diagnostics/type-check.lua

@@ -1088,6 +1088,32 @@ end
 func('hello', 'world')
 ]]
 
+TEST [[
+---@generic T1, T2, T3, T4, T5
+---@param f fun(): T1?, T2?, T3?, T4?, T5?
+---@return T1?, T2?, T3?, T4?, T5?
+local function foo(f)
+    return f()
+end
+
+local a, b = foo(function()
+    return 1
+end)
+]]
+
+TEST [[
+---@generic T1, T2, T3, T4, T5
+---@param f fun(): T1|nil, T2|nil, T3|nil, T4|nil, T5|nil
+---@return T1?, T2?, T3?, T4?, T5?
+local function foo(f)
+    return f()
+end
+
+local a, b = foo(function()
+    return 1
+end)
+]]
+
 config.remove(nil, 'Lua.diagnostics.disable', 'unused-local')
 config.remove(nil, 'Lua.diagnostics.disable', 'unused-function')
 config.remove(nil, 'Lua.diagnostics.disable', 'undefined-global')