fix #1346

Author: sumneko

changelog.md

@@ -69,6 +69,7 @@
 * `FIX` [#1317](https://github.com/sumneko/lua-language-server/issues/1317)
 * `FIX` [#1320](https://github.com/sumneko/lua-language-server/issues/1320)
 * `FIX` [#1330](https://github.com/sumneko/lua-language-server/issues/1330)
+* `FIX` [#1346](https://github.com/sumneko/lua-language-server/issues/1346)
 
 ## 3.4.2
 `2022-7-6`

script/vm/type.lua

@@ -105,13 +105,16 @@ function vm.isSubType(uri, child, parent, mark)
         child = global
     elseif child.type == 'vm.node' then
         if config.get(uri, 'Lua.type.weakUnionCheck') then
+            local hasKnownType
             for n in child:eachObject() do
-                if  getNodeName(n)
-                and vm.isSubType(uri, n, parent, mark) then
-                    return true
+                if getNodeName(n) then
+                    hasKnownType = true
+                    if vm.isSubType(uri, n, parent, mark) then
+                        return true
+                    end
                 end
             end
-            return false
+            return not hasKnownType
         else
             local weakNil   = config.get(uri, 'Lua.type.weakNilCheck')
             for n in child:eachObject() do

test/diagnostics/type-check.lua

@@ -1,6 +1,7 @@
 local config = require 'config'
 
 config.add(nil, 'Lua.diagnostics.disable', 'unused-local')
+config.add(nil, 'Lua.diagnostics.disable', 'unused-function')
 config.add(nil, 'Lua.diagnostics.disable', 'undefined-global')
 
 TEST [[
@@ -727,6 +728,15 @@ TEST [[
 ---@type number
 local x = G
 ]]
+
+TEST [[
+---@generic T
+---@param x T
+---@return T
+local function f(x)
+    return x
+end
+]]
 config.set(nil, 'Lua.type.weakUnionCheck', false)
 
 TEST [[
@@ -765,4 +775,5 @@ f(<!3!>)
 ]]
 
 config.remove(nil, 'Lua.diagnostics.disable', 'unused-local')
+config.remove(nil, 'Lua.diagnostics.disable', 'unused-function')
 config.remove(nil, 'Lua.diagnostics.disable', 'undefined-global')