[libcxx-commits] [libcxx] [libc++][ratio] Avoids accepting unrelated types. (PR #80491)

[Louis Dionne via libcxx-commits]

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@@ -0,0 +1,65 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// <ratio>
+//
+// [ratio.general]/2
+//   Throughout subclause [ratio], the names of template parameters are
+//   used to express type requirements. If a template parameter is named
+//   R1 or R2, and the template argument is not a specialization of the
+//   ratio template, the program is ill-formed.
+//
+// Since std::ratio_xxx_v uses the same instantiations only one error
+// will be generated. These values are tested in a separate test.
+
+#include <ratio>
+
+struct R {
+  static const int num = 1;
+  static const int den = 1;
+};
+
+using r = std::ratio<1, 1>;
+
+namespace equal {
+using r_r = std::ratio_equal<r, r>::type;
+using R_r = std::ratio_equal<R, r>::type; // expected-error@*:* {{R1 to be a specialisation of the ratio template}}
+using r_R = std::ratio_equal<r, R>::type; // expected-error@*:* {{R2 to be a specialisation of the ratio template}}
+} // namespace equal
+
+namespace not_equal {
+using r_r = std::ratio_not_equal<r, r>::type;
----------------
ldionne wrote:

You could also do a function and block scopes here, that way you simplify the namespaces.

https://github.com/llvm/llvm-project/pull/80491