[PATCH] D98971: [C++20] [P1825] Fix bugs with implicit-move from variables of reference type

[Matheus Izvekov via Phabricator via cfe-commits]

mizvekov added inline comments.


================
Comment at: clang/lib/Sema/SemaStmt.cpp:3095
 
-  // ...non-volatile...
-  if (VD->getType().isVolatileQualified())
-    return false;
-
-  // C++20 [class.copy.elision]p3:
-  // ...rvalue reference to a non-volatile...
-  if (VD->getType()->isRValueReferenceType() &&
-      (!(CESK & CES_AllowRValueReferenceType) ||
-       VD->getType().getNonReferenceType().isVolatileQualified()))
+  if (VD->getType()->isObjectType()) {
+    // C++17 [class.copy.elision]p3:
----------------
mizvekov wrote:
> mizvekov wrote:
> > A drive by fix here would be that we already have a VDType in this context, might as well use it even though original for some reason missed it in this part.
> This whole block is also logically equivalent to the much simpler:
> ```
> if (VDType.isReferenceType()) {
>     if (!(CESK & CES_AllowRValueReferenceType) || !VDType.isRValueReferenceType())
>       return false;
>     VDType = VDType.getNonReferenceType()
> }
> if (!VDType.isObjectType() || VDType.isVolatileQualified()) 
>   return false;
> ```
> But you do have to adjust the comments there and adjust the rest to use VDType consistently :)
> Also, I think it might be possible to even remove the `!VDType.isObjectType() || ` part from my suggestion above, because it might be the only option left if it is not a reference anyway.
```
  bool isObjectType() const {
    // C++ [basic.types]p8:
    //   An object type is a (possibly cv-qualified) type that is not a
    //   function type, not a reference type, and not a void type.
    return !isReferenceType() && !isFunctionType() && !isVoidType();
  }
```
So yeah I think you can just make my suggestion be:
```
if (VDType.isReferenceType()) {
    if (!(CESK & CES_AllowRValueReferenceType) || !VDType.isRValueReferenceType())
      return false;
    VDType = VDType.getNonReferenceType()
}
if (VDType.isVolatileQualified()) 
  return false;
```




Repository:
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  https://reviews.llvm.org/D98971/new/

https://reviews.llvm.org/D98971