special treate for return values of require

2nd should be unknown since Lua 5.3, otherwise should be nil

#1868

Author: sumneko

changelog.md

@@ -2,8 +2,10 @@
 
 ## 3.6.9
 * `FIX` [#1864]
+* `FIX` [#1868]
 
 [#1864]: https://github.com/sumneko/lua-language-server/issues/1864
+[#1868]: https://github.com/sumneko/lua-language-server/issues/1868
 
 ## 3.6.8
 `2023-1-31`

script/vm/compiler.lua

@@ -1484,6 +1484,21 @@ local compilerSwitch = util.switch()
             return
         end
         if func.special == 'require' then
+            if index == 2 then
+                local uri = guide.getUri(source)
+                local version = config.get(uri, 'Lua.runtime.version')
+                if version == 'Lua 5.3'
+                or version == 'Lua 5.4' then
+                    vm.setNode(source, vm.declareGlobal('type', 'unknown'))
+                else
+                    vm.setNode(source, vm.declareGlobal('type', 'nil'))
+                end
+                return
+            end
+            if index >= 3 then
+                vm.setNode(source, vm.declareGlobal('type', 'nil'))
+                return
+            end
             if not args then
                 return
             end

test/crossfile/infer.lua

@@ -133,3 +133,33 @@ print(<?X?>)
 ]], },
     infer = 'boolean|integer',
 }
+
+TEST {
+    { path = 'a.lua', content = [[
+return 1337, "string", true
+]], },
+    { path = 'b.lua', content = [[
+local <?a?>, b, c = require 'a
+]], },
+    infer = 'integer',
+}
+
+TEST {
+    { path = 'a.lua', content = [[
+return 1337, "string", true
+]], },
+    { path = 'b.lua', content = [[
+local a, <?b?>, c = require 'a
+]], },
+    infer = 'unknown',
+}
+
+TEST {
+    { path = 'a.lua', content = [[
+return 1337, "string", true
+]], },
+    { path = 'b.lua', content = [[
+local a, b, <?c?> = require 'a
+]], },
+    infer = 'nil',
+}