[PATCH] D87565: [Sema] Improve const_cast conformance to N4261

[Richard Smith - zygoloid via Phabricator via cfe-commits]

rsmith added inline comments.


================
Comment at: clang/lib/Sema/SemaCast.cpp:1817-1819
+      NeedToMaterializeTemporary =
+          SrcType->isRecordType() || SrcType->isArrayType() ||
+          SrcType->isFunctionPointerType() || SrcType->isMemberPointerType();
----------------
It looks like GCC allowing a cast from `T*` to `T*&&` is just a bug in their implementation. Consider:

```
using T = int*;
T &&r1 = const_cast<T&&>(T{}); // GCC accepts
T &&r2 = const_cast<T&&>(T()); // GCC rejects
```

... and the same behavior seems to show up for all scalar types: they permit `const_cast` from `T{}` but not from `T()` when `T` is `int`, `int*`, .... This doesn't seem like good behavior to follow. I think we should either implement the current direction of 1965 (that is, only allow classes and arrays here) or leave the current behavior (following the standard as-is) alone.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D87565/new/

https://reviews.llvm.org/D87565