add UT and release note

Author: Backl1ght

clang/docs/ReleaseNotes.rst

@@ -432,6 +432,8 @@ Bug Fixes in This Version
 - Fixed a failed assertion with empty filename arguments in ``__has_embed``. (#GH159898)
 - Fixed a failed assertion with empty filename in ``#embed`` directive. (#GH162951)
 - Fixed a crash triggered by unterminated ``__has_embed``. (#GH162953)
+- Fixed a wrong diagnostic about a local variable inside a lambda in unevaluated
+  contexts need capture. (#GH163837)
 
 Bug Fixes to Compiler Builtins
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

clang/test/SemaCXX/lambda-unevaluated.cpp

@@ -282,3 +282,22 @@ static_assert(__is_same_as(int, helper<int>));
 
 
 } // namespace GH138018
+
+namespace GH163837 {
+
+template<int N>
+void f();
+
+template<class>
+struct X {
+    using type = decltype([](auto) {
+        f<[]{
+            int result = 0;
+            return result;
+        }()>();
+    }(0));
+};
+
+X<void> l;
+
+} // namespace GH163837