aaron.ballman added inline comments.
================
Comment at: clang/lib/Sema/SemaExpr.cpp:15783
+ // test for typesAreCompatible() will already properly consider those to
+ // be compatible types.
+ if (Context.getLangOpts().CPlusPlus && !PromoteType.isNull() &&
----------------
efriedma wrote:
> This explanation doesn't seem right. Signed and unsigned types are never
> considered "compatible".
>
> If I'm understanding correctly, the case this code addresses is promotion
> according to `[conv.prom]`p3: "A prvalue of an unscoped enumeration type
> whose underlying type is not fixed [...]". Somehow, the enum ends up with an
> unsigned underlying type, but we promote to int? And this doesn't happen in
> C somehow?
> This explanation doesn't seem right. Signed and unsigned types are never
> considered "compatible".
Good point, I think that comment is wrong.
> If I'm understanding correctly, the case this code addresses is promotion
> according to [conv.prom]p3: "A prvalue of an unscoped enumeration type whose
> underlying type is not fixed [...]". Somehow, the enum ends up with an
> unsigned underlying type, but we promote to int? And this doesn't happen in C
> somehow?
That's correct. What I am seeing is:
```
enum Unscoped { One = 0x7FFFFFFF };
```
C++:
`PromoteType` = Builtin (Int)
`UnderlyingType` = Builtin (UInt)
C:
`PromoteType` = Builtin (UInt)
`UnderlyingType` = Builtin (UInt)
`enum Unscoped { One = 0xFFFFFFFF };`
C++:
`PromoteType` = Builtin (UInt)
`UnderlyingType` = Builtin (UInt)
C:
`PromoteType` = Builtin (UInt)
`UnderlyingType` = Builtin (UInt)
At least on i386-pc-unknown.
So I think this code is almost correct for that test, but is over-constrained
by only doing this in C++. WDYT?
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D103611/new/
https://reviews.llvm.org/D103611
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