[libcxx-commits] [libcxx] [libc++][test] Fixes for `hash<Emplaceable>` and value discarding (PR #126566)

[A. Jiang via libcxx-commits]

https://github.com/frederick-vs-ja created https://github.com/llvm/llvm-project/pull/126566

Currently `std::hash<Emplaceable>::operator()` relies implicit conversion from `int` to `size_t`, which makes MSVC compelling. This PR switches to use `static_cast`.

In `flat.map/flat.map.access/at_transparent.pass.cpp`, there's one value-discarding use of `at` that wasn't marked `TEST_IGNORE_NODISCARD`. This PR adds the missing `TEST_IGNORE_NODISCARD`.

>From e7b6840a75f657ae4ffe8b3932fb578ff293140d Mon Sep 17 00:00:00 2001
From: "A. Jiang" <de34 at live.cn>
Date: Tue, 11 Feb 2025 01:43:18 +0800
Subject: [PATCH] [libc++][test] Fixes for `hash<Emplaceable>` and value
 discarding

Currently `std::hash<Emplaceable>::operator()` relies implicit
conversion from `int` to `size_t`, which makes MSVC compelling. This PR
switches to use `static_cast`.

In `flat.map/flat.map.access/at_transparent.pass.cpp`, there's one
value-discarding use of `at` that wasn't marked `TEST_IGNORE_NODISCARD`.
This PR adds the missing `TEST_IGNORE_NODISCARD`.
---
 libcxx/test/std/containers/Emplaceable.h                        | 2 +-
 .../flat.map/flat.map.access/at_transparent.pass.cpp            | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/libcxx/test/std/containers/Emplaceable.h b/libcxx/test/std/containers/Emplaceable.h
index 1a4e14505fb21ed..001886eece7d75e 100644
--- a/libcxx/test/std/containers/Emplaceable.h
+++ b/libcxx/test/std/containers/Emplaceable.h
@@ -45,7 +45,7 @@ struct std::hash<Emplaceable> {
   typedef Emplaceable argument_type;
   typedef std::size_t result_type;
 
-  std::size_t operator()(const Emplaceable& x) const { return x.get(); }
+  std::size_t operator()(const Emplaceable& x) const { return static_cast<std::size_t>(x.get()); }
 };
 
 #endif // TEST_STD_VER >= 11
diff --git a/libcxx/test/std/containers/container.adaptors/flat.map/flat.map.access/at_transparent.pass.cpp b/libcxx/test/std/containers/container.adaptors/flat.map/flat.map.access/at_transparent.pass.cpp
index 13edca915fd005c..456f12e0c0d29ff 100644
--- a/libcxx/test/std/containers/container.adaptors/flat.map/flat.map.access/at_transparent.pass.cpp
+++ b/libcxx/test/std/containers/container.adaptors/flat.map/flat.map.access/at_transparent.pass.cpp
@@ -103,7 +103,7 @@ int main(int, char**) {
     TransparentComparator c(transparent_used);
     std::flat_map<int, int, TransparentComparator> m(std::sorted_unique, {{1, 1}, {2, 2}, {3, 3}}, c);
     assert(!transparent_used);
-    m.at(Transparent<int>{3});
+    TEST_IGNORE_NODISCARD m.at(Transparent<int>{3});
     assert(transparent_used);
   }