don't check duplicate-set-field in different if

script/core/diagnostics/duplicate-set-field.lua

@@ -11,13 +11,33 @@ local sourceTypes = {
     'setindex',
 }
 
+---@param source parser.object
+---@return parser.object?
+local function getTopFunctionOfIf(source)
+    while true do
+        if source.type == 'ifblock'
+        or source.type == 'elseifblock'
+        or source.type == 'elseblock'
+        or source.type == 'function'
+        or source.type == 'main' then
+            return source
+        end
+        source = source.parent
+    end
+    return nil
+end
+
 ---@async
 return function (uri, callback)
     local state = files.getState(uri)
     if not state then
         return
     end
 
+    if vm.isMetaFile(uri) then
+        return
+    end
+
     ---@async
     guide.eachSourceTypes(state.ast, sourceTypes, function (src)
         await.delay()
@@ -29,6 +49,7 @@ return function (uri, callback)
         if not value or value.type ~= 'function' then
             return
         end
+        local myTopBlock = getTopFunctionOfIf(src)
         local defs = vm.getDefs(src)
         for _, def in ipairs(defs) do
             if def == src then
@@ -39,6 +60,10 @@ return function (uri, callback)
             and def.type ~= 'setindex' then
                 goto CONTINUE
             end
+            local defTopBlock = getTopFunctionOfIf(def)
+            if uri == guide.getUri(def) and myTopBlock ~= defTopBlock then
+                goto CONTINUE
+            end
             local defValue = vm.getObjectValue(def)
             if not defValue or defValue.type ~= 'function' then
                 goto CONTINUE

test/diagnostics/common.lua

@@ -2231,3 +2231,34 @@ mt.init = function ()
     obj.x = 1
 end
 ]]
+
+TEST [[
+---@class A
+X = {}
+
+function <!X.f!>() end
+
+function <!X.f!>() end
+]]
+
+TEST [[
+---@meta
+
+---@class A
+X = {}
+
+function X.f() end
+
+function X.f() end
+]]
+
+TEST [[
+---@class A
+X = {}
+
+if true then
+    function X.f() end
+else
+    function X.f() end
+end
+]]