look into unions for operators

fix #1996

changelog.md

@@ -2,8 +2,10 @@
 
 ## 3.6.18
 * `FIX` [#1943]
+* `FIX` [#1996]
 
 [#1943]: https://github.com/LuaLS/lua-language-server/issues/1943
+[#1996]: https://github.com/LuaLS/lua-language-server/issues/1996
 
 ## 3.6.17
 `2023-3-9`

script/vm/operator.lua

@@ -73,15 +73,22 @@ local function checkOperators(operators, op, value, result)
             local valueNode = vm.compileNode(value)
             local expNode   = vm.compileNode(operator.exp)
             local uri       = guide.getUri(operator)
-            if not vm.isSubType(uri, valueNode, expNode) then
-                goto CONTINUE
+            for vo in valueNode:eachObject() do
+                if vm.isSubType(uri, vo, expNode) then
+                    if not result then
+                        result = vm.createNode()
+                    end
+                    result:merge(vm.compileNode(operator.extends))
+                    return result
+                end
             end
+        else
+            if not result then
+                result = vm.createNode()
+            end
+            result:merge(vm.compileNode(operator.extends))
+            return result
         end
-        if not result then
-            result = vm.createNode()
-        end
-        result:merge(vm.compileNode(operator.extends))
-        break
         ::CONTINUE::
     end
     return result

test/type_inference/init.lua

@@ -4239,3 +4239,18 @@ TEST 'number' [[
 local n
 local <?v?> = n or error('')
 ]]
+
+TEST 'Foo' [[
+---@class Foo
+---@operator mul(Foo): Foo
+---@operator mul(Bar): Foo
+---@class Bar
+
+---@type Foo
+local foo
+
+---@type Foo|Bar
+local fooOrBar
+
+local <?b?> = foo * fooOrBar
+]]