1 files changed, 84 insertions, 0 deletions
diff --git a/script/core/diagnostics/missing-return.lua b/script/core/diagnostics/missing-return.lua
new file mode 100644
index 00000000..08932c83
--- /dev/null
+++ b/script/core/diagnostics/missing-return.lua
@@ -0,0 +1,84 @@
+local files  = require 'files'
+local guide  = require 'parser.guide'
+local vm     = require 'vm'
+local lang   = require 'language'
+
+---@param uri uri
+---@param func parser.object
+local function hasDocReturn(uri, func)
+    if not func.bindDocs then
+        return false
+    end
+    for _, doc in ipairs(func.bindDocs) do
+        if doc.type == 'doc.return' then
+            -- don't need return with only one `any`
+            local lastReturn = doc.returns[#doc.returns]
+            if lastReturn.returnIndex ~= 1
+            or vm.getInfer(lastReturn):view(uri) ~= 'any' then
+                return true
+            end
+        end
+    end
+    return false
+end
+
+---@param block parser.object
+---@return boolean
+local function hasReturn(block)
+    if block.hasReturn or block.hasError then
+        return true
+    end
+    if block.type == 'if' then
+        local hasElse
+        for _, subBlock in ipairs(block) do
+            if not hasReturn(subBlock) then
+                return false
+            end
+            if subBlock.type == 'elseblock' then
+                hasElse = true
+            end
+        end
+        return hasElse == true
+    else
+        if block.type == 'while' then
+            if vm.testCondition(block.filter) then
+                return true
+            end
+        end
+        for _, action in ipairs(block) do
+            if guide.isBlockType(action) then
+                if hasReturn(action) then
+                    return true
+                end
+            end
+        end
+    end
+    return false
+end
+
+return function (uri, callback)
+    local state = files.getState(uri)
+    if not state then
+        return
+    end
+
+    guide.eachSourceType(state.ast, 'function', function (source)
+        -- check declare only
+        if #source == 0 then
+            return
+        end
+        if not hasDocReturn(uri, source) then
+            return
+        end
+        if hasReturn(source) then
+            return
+        end
+        local lastAction = source[#source]
+        local finish = lastAction.range or lastAction.finish
+        callback {
+            start   = finish,
+            finish  = finish,
+            message = lang.script('DIAG_MISSING_RETURN'),
+        }
+    end)
+end