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CWG2668 [expr.await] await-expression is forbidden to appear in the lambda-expression #195
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"outside of a handler" should also apply to the lambda-expression case.
- changed the title
[-][expr.await] await-expression is forbidden to appear in the lambda-expression[/-][+]CWG2668 [expr.await] await-expression is forbidden to appear in the lambda-expression[/+]on Dec 17, 2022 "outside of a handler" should also apply to the lambda-expression case.
Where does the handler appear in a lambda-expression? The original wording says
within the compound-statement of a function-body outside of a handler ([except.pre])
IIUC, it means that the await-expression can only appear within the compound-statement of a function-body, and shouldn't appear in the handler if the function-body is a function-try-block. In other words, the following example is forbidden
Task fun() try{}catch(...){ co_await Awaitable{}; // ill-formed }
Conversely, the below code is well-formed
Task fun(){ try{}catch(...){ co_await Awaitable{}; } }
Since lambda-expression itself does not have a handler component, I don't think "outside of a handler" should also apply to the lambda-expression case.
Or, does the original wording intend to mean both cases are ill-formed?
Or, does the original wording intend to mean both cases are ill-formed?
That's my reading. Both cases are "handlers", I think.
Or, does the original wording intend to mean both cases are ill-formed?
That's my reading. Both cases are "handlers", I think.
Thanks, you're right. I tested the code in GCC and Clang, and they all agree that the await-expression cannot appear within a handler, that is, "or..." is the proper reading.
Full name of submitter (unless configured in github; will be published with the issue): Jim X
[expr.await] p2 says
Consider this example
Grammarly, the await-expression appears in the compound-statement of a lambda-expression rather than the compound-statement of a function-body, even if [expr.prim.lambda.closure] p13
Anyway, they are not equivalent in grammar.
Suggested resolution