[libcxx-commits] [libcxx] Add a regression test for recent regression in pair. (PR #97355)

[James Y Knight via libcxx-commits]

https://github.com/jyknight created https://github.com/llvm/llvm-project/pull/97355

PR #96165 broke code similar to this test, and was subsequently reverted. Add a test-case, to ensure the problem won't reoccur.

>From 832d98196ddd7902311fb12b85667543ca26e537 Mon Sep 17 00:00:00 2001
From: James Y Knight <jyknight at google.com>
Date: Mon, 1 Jul 2024 17:32:11 -0400
Subject: [PATCH] Add a regression test for recent regression in pair.

PR #96165 broke code similar to this test, and was subsequently
reverted. Add a test-case, to ensure the problem won't reoccur.
---
 .../pairs/pairs.pair/pair.incomplete.verify.cpp   | 15 +++++++++++++++
 1 file changed, 15 insertions(+)
 create mode 100644 libcxx/test/libcxx/utilities/utility/pairs/pairs.pair/pair.incomplete.verify.cpp

diff --git a/libcxx/test/libcxx/utilities/utility/pairs/pairs.pair/pair.incomplete.verify.cpp b/libcxx/test/libcxx/utilities/utility/pairs/pairs.pair/pair.incomplete.verify.cpp
new file mode 100644
index 0000000000000..d0832ea311690
--- /dev/null
+++ b/libcxx/test/libcxx/utilities/utility/pairs/pairs.pair/pair.incomplete.verify.cpp
@@ -0,0 +1,15 @@
+// Check that instantiating pair doesn't look up type traits "too early", before
+// the contained types have been completed.
+//
+// This is a regression test, to prevent a reoccurrance of the issue introduced in
+// 5e1de27f680591a870d78e9952b23f76aed7f456.
+
+// expected-no-diagnostics
+#include <utility>
+#include <vector>
+
+struct Test {
+  std::vector<std::pair<int, Test>> v;
+};
+
+std::pair<int, Test> p;