Generic return can be optional.

Author: TIMONz1535

changelog.md

@@ -13,6 +13,7 @@
   ```
 * `NEW` Test CLI: `--name=<testname>` `-n=<testname>`: run specify unit test
 * `FIX` Fixed the error that the configuration file pointed to by the `--configpath` option was not read and loaded.
+* `FIX` Generic return can be optional.
 
 ## 3.13.5
 `2024-12-20`

script/vm/generic.lua

@@ -136,6 +136,9 @@ function mt:resolve(uri, args)
             end
         end
     end
+    if protoNode:isOptional() then
+        result:addOptional()
+    end
     return result
 end
 

test/diagnostics/missing-return.lua

@@ -156,3 +156,21 @@ function F()
 
 end
 ]]
+
+TEST [[
+---@generic T
+---@param t T
+---@return T
+function F(t)
+	return t
+end
+]]
+
+TEST [[
+---@generic T
+---@param t T
+---@return T?
+function F(t)
+
+end
+]]

test/type_inference/common.lua

@@ -359,8 +359,32 @@ end
 local _, _, _, <?b?>, _ = x(nil, true, 1, 'yy')
 ]]
 
+TEST 'nil' [[
+local <?k?>, <?v?> = next()
+local <?k?>, <?v?> = next({})
+]]
+
+TEST 'integer?' [[
+local <?k?>, <?v?> = next({1})
+]]
+
+TEST 'integer?' [[
+local a
+local <?k?>, v = next({a})
+]]
+
+-- probably explicit unknown generic should be unknown
+TEST 'nil' [[
+local a
+local k, <?v?> = next({a})
+]]
+
 TEST 'unknown' [[
-local <?x?> = next()
+---@generic T
+---@param t T?
+---@return T
+local function F(t) end
+local <?x?> = F()
 ]]
 
 TEST 'unknown' [[