erichkeane added inline comments.
================
Comment at: clang/lib/AST/ExprConstant.cpp:13533
+
+ if (NumNegativeBits) {
+ unsigned NumBits = std::max(NumNegativeBits, NumPositiveBits + 1);
----------------
erichkeane wrote:
> So my reading of 'within the range of the enumeration values' is different
> here. Given:
>
> `enum F { -4, 4};`, the valid values for assignment I would say are -4, -3,
> -2, -1, 0, 1, 2, 3, 4. This error seems to be a bit more permissive here by
> making sure it is represent-able by the number of bits required to represent
> the enum.
>
>
Aaron pointed out off-line that I'm incorrect in what 'range of enumeration
values' means, and that the values comes from
https://eel.is/c++draft/dcl.enum#8.sentence-2.
So the logic here needs to be to find the smallest integer (regardless of the
power-of-2-ness of its bit-size) that can represent all of the values
(including a 1 bit value for empty I think?), and diagnose based on that.
================
Comment at: clang/test/SemaCXX/constant-expression-cxx2a.cpp:1477
+
+enum E { e1=-4, e2=4};
+void testValueInRangeOfEnumerationValues() {
----------------
erichkeane wrote:
> Theres likely quite a few more tests that need to be done. We should have
> one where it validates against a fixed underlying type, AND probably a pair
> of ones to check against scoped enums.
>
> I wouldn't expect a scoped enum to diagnose, but a test to make sure we're
> checking the right thing is likely valuable.
Another good test is the empty-enum case.
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D130058/new/
https://reviews.llvm.org/D130058
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