[expr.const] P2686R4 made it less clear that a prvalue constant expression must have an object type CWG3136
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Description
In C++23, it seemed clear to me that a prvalue constant expression was required to have an object type, because N4950 [expr.const] p13 explicitly listed permitted cases for various object types.
However, after P2686R4, [expr.const] p22 doesn't seem to require object types, and void expressions are arguably accepted. At least, a prvalue of an empty class type and a void prvalue don't seem distinguishable.
Should we clarify the wording to say a prvalue constant expression must have an object type, or, conversely, a void expression can be a prvalue constant expression?
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Research direction
Start with the cited [expr.const] paragraphs in N4950 and the current draft, then read P2686R4 and CWG3136. Compare the treatment of empty-class prvalues and void prvalues, and resolve whether the wording should require an object type or permit void; done means an agreed clarification in the standard wording.
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Assessment
- Tech stack
- cpp
- Domain
- compilers
- Issue type
- Documentation
- Difficulty
- 5/5
- Estimated time
- Over a week
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100