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:
----------------
aaronpuchert wrote:
> mizvekov wrote:
> > Quuxplusone wrote:
> > > mizvekov wrote:
> > > > 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;
> > > > ```
> > > >
> > > >
> > > Yeah but I //reaally// don't want to
> > > (1) change the meaning of `VDType` in the middle of this function
> > > (mantra: "one name = one meaning")
> > > (2) get "clever". I don't want to have to think about "Are there any
> > > types that are neither object types nor reference types?" (What about
> > > function types? What about block types? What about, I dunno, bit-fields?)
> > > I want the code to be //obviously correct//, and also to casewise match
> > > exactly what the standard says. It says object or rvalue reference type —
> > > let's write code that expresses that wording //exactly//.
> > How about:
> > ```
> > QualType VDObjType = VDType;
> > if (!VDType.isObjectType()) {
> > if (!(CESK & CES_AllowRValueReferenceType) ||
> > !VDType.isRValueReferenceType())
> > return false;
> > VDObjType = VDType.getNonReferenceType();
> > }
> > if (VDObjType .isVolatileQualified())
> > return false;
> > ```
> > And then `s/VDType/VDObjType/` from here on.
> > I think this expresses the meaning of the standard clearly.
> That seems like a sensible simplification, the proposed code is indeed a bit
> repetitive. I'd go with the original suggestion plus the new variable:
>
> ```
> QualType VDNonRefType = VDType;
> if (VDType.isReferenceType()) {
> if (!(CESK & CES_AllowRValueReferenceType) ||
> !VDType.isRValueReferenceType())
> return false;
> VDNonRefType = VDType.getNonReferenceType()
> }
> if (!VDNonRefType.isObjectType() || VDNonRefType.isVolatileQualified())
> return false;
> ```
>
> or whatever name you find appropriate. Actually it's the type of the
> `DeclRefExpr`, isn't it? So maybe `DREType`?
>
> The initialization might be a bit misleading, an alternative would be to not
> initialize and have an assignment `VDNonRefType = VDType` in the else branch
> instead.
@aaronpuchert Yeah that combination is good to me also, and I liked the name
you suggested better. So +1 :)
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D98971/new/
https://reviews.llvm.org/D98971
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