[clang] [Clang] Allow __is_nothrow_convertible to be used as an identifier (PR #80476)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Nikolas Klauser (philnik777)

<details>
<summary>Changes</summary>

`__is_nothrow_convertible` has been used by libstdc++ previously as an identifier.


---
Full diff: https://github.com/llvm/llvm-project/pull/80476.diff


2 Files Affected:

- (modified) clang/lib/Parse/ParseDeclCXX.cpp (+1) 
- (added) clang/test/SemaCXX/libstdcxx_is_nothrow_convertible_hack.cpp (+14) 


``````````diff
diff --git a/clang/lib/Parse/ParseDeclCXX.cpp b/clang/lib/Parse/ParseDeclCXX.cpp
index cdbfbb1bc9fff..79928ddb5af59 100644
--- a/clang/lib/Parse/ParseDeclCXX.cpp
+++ b/clang/lib/Parse/ParseDeclCXX.cpp
@@ -1725,6 +1725,7 @@ void Parser::ParseClassSpecifier(tok::TokenKind TagTokKind,
           tok::kw___is_member_pointer,
           tok::kw___is_nothrow_assignable,
           tok::kw___is_nothrow_constructible,
+          tok::kw___is_nothrow_convertible,
           tok::kw___is_nothrow_destructible,
           tok::kw___is_nullptr,
           tok::kw___is_object,
diff --git a/clang/test/SemaCXX/libstdcxx_is_nothrow_convertible_hack.cpp b/clang/test/SemaCXX/libstdcxx_is_nothrow_convertible_hack.cpp
new file mode 100644
index 0000000000000..9e84f0ab1c081
--- /dev/null
+++ b/clang/test/SemaCXX/libstdcxx_is_nothrow_convertible_hack.cpp
@@ -0,0 +1,14 @@
+// RUN: %clang_cc1 -triple x86_64-apple-darwin10 -fsyntax-only -verify -std=gnu++20 -fms-extensions -Wno-microsoft %s
+// RUN: %clang_cc1 -triple x86_64-apple-darwin10 -fsyntax-only -verify -std=gnu++23 -fms-extensions -Wno-microsoft %s
+
+template <class T, class U>
+struct Same {
+  static constexpr auto value = __is_same(T, U);
+};
+
+template <class T>
+struct __is_nothrow_convertible { // expected-warning{{keyword '__is_nothrow_convertible' will be made available as an identifier for the remainder of the translation unit}}
+  using type = T;
+};
+
+using A = Same<__is_nothrow_convertible<int>::type, __is_nothrow_convertible<int>::type>;

``````````

</details>


https://github.com/llvm/llvm-project/pull/80476