recover mark before return

fix #2004

Author: sumneko

changelog.md

@@ -3,10 +3,12 @@
 ## 3.6.18
 * `FIX` [#1943]
 * `FIX` [#1996]
+* `FIX` [#2004]
 * `FIX` [#2013]
 
 [#1943]: https://github.com/LuaLS/lua-language-server/issues/1943
 [#1996]: https://github.com/LuaLS/lua-language-server/issues/1996
+[#2004]: https://github.com/LuaLS/lua-language-server/issues/2004
 [#2013]: https://github.com/LuaLS/lua-language-server/issues/2013
 
 ## 3.6.17

script/vm/type.lua

@@ -466,6 +466,7 @@ function vm.isSubType(uri, child, parent, mark, errs)
                         if  ext.type == 'doc.extends.name'
                         and (not isBasicType or guide.isBasicType(ext[1]))
                         and vm.isSubType(uri, ext[1], parent, mark, errs) == true then
+                            mark[childName] = nil
                             return true
                         end
                     end

test/diagnostics/type-check.lua

@@ -1238,6 +1238,23 @@ local arr2 = {
 }
 ]]
 
+TEST [[
+---@class A
+
+---@class B : A
+
+---@class C : B
+
+---@class D : B
+
+---@param x A
+local function func(x) end
+
+---@type C|D
+local var
+func(var)
+]]
+
 config.remove(nil, 'Lua.diagnostics.disable', 'unused-local')
 config.remove(nil, 'Lua.diagnostics.disable', 'unused-function')
 config.remove(nil, 'Lua.diagnostics.disable', 'undefined-global')