[pushed] c++: add fixed test [PR118482]

[Marek Polacek]

Tested x86_64-pc-linux-gnu, applying to trunk.

-- >8 --
Fixed by r15-9362.

        PR c++/118482

gcc/testsuite/ChangeLog:

        * g++.dg/cpp2a/lambda-uneval31.C: New test.
---
 gcc/testsuite/g++.dg/cpp2a/lambda-uneval31.C | 12 ++++++++++++
 1 file changed, 12 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/cpp2a/lambda-uneval31.C

diff --git a/gcc/testsuite/g++.dg/cpp2a/lambda-uneval31.C 
b/gcc/testsuite/g++.dg/cpp2a/lambda-uneval31.C
new file mode 100644
index 00000000000..4fedaf81104
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/lambda-uneval31.C
@@ -0,0 +1,12 @@
+// PR c++/118482
+// { dg-do compile { target c++20 } }
+
+using what_type = decltype(
+    [](auto&& self,
+        decltype([](decltype(self)&){}) x = {}){ return x; });
+
+what_type x;
+
+int main() {
+    if (x(x)) return 1;
+}

base-commit: a48fbdd6a803429ccf2eda7c9ba8ecdd975f8e35
-- 
2.53.0