[expr.unary.noexcept] Replace informative wording #6539
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source/expressions.tex
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| The \keyword{noexcept} operator yields \keyword{true} | ||
| unless the full-expression of the operand | ||
| is potentially-throwing\iref{except.spec}. | ||
| The operand of the \keyword{noexcept} operator | ||
| is an unevaluated operand\iref{term.unevaluated.operand}. | ||
| \begin{bnf} |
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I think there is some room for improvement in this subclause, but talking about "the operand" in detail before we've even introduced the grammar seems unhelpful.
My suggestion:
- grammar first
- then talk about the operand
- then talk about the result
- then have the note about constant expression
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I've implemented most of what you've suggested, but I don't understand what you mean by "note about constant expression". Neither the old wording nor the new wording talks about constant expressions.
Wouldn't adding a note be a topic for another PR?
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"[Note 1 : A noexcept-expression is an integral constant expression (7.7). — end note]"
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Ah yes, I wasn't looking at the second paragraph. I've moved it up now.
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Sorry, but that's not exactly what I had in mind. Since the change is a little larger, I've created CWG2792 to have CWG review the change. See there for my suggestion; feel free to continue to discuss here. |
Context and Problem with the Current Wording
I was briefly under the impression that
a + bcan throw for twointsaandb, because signed integer overflow is UB, and UB can result in throwing exceptions, and maybe thenoexceptoperator needs to consider that.Paragraph 1 in its current form says:
An unsuspecting reader like me might assume that this includes exceptions thrown as the result of UB. However, this isn't actually possible, and this wording is purely informative. Paragraph 3 contains the actual normative wording, explaining that the
noexceptoperator checks whether an expression is potentially-throwing.Suggested Solution
This PR moves the actual normative wording from p3 up into p1 to avoid any future confusion. The informative wording is removed.