Add rescue to support streamline error handling #7038
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This implements inline `rescue` like those in Ruby [1], but more powerful in that users can specify the exception to be handled. The `rescue` method will be very convenient in scripting. [1] https://stackoverflow.com/questions/15396791/ruby-oneline-rescue
smarter
reviewed
Aug 14, 2019
Without the change, exceptions other than the following will not be propagated.
Instead, users will get `scala.MatchError`.
op rescue {
case ex: NullPointerException => 4
case ex: ArithmeticException => 3
}
smarter
reviewed
Aug 14, 2019
However, with explict cases, user may match fatal errors except for non-local returns, which users should not catch.
| // case ex: ReturnThrowable[_] => throw ex // bug #7041 | ||
| case ex: E => | ||
| // user should never match `ReturnThrowable`, which breaks semantics of non-local return | ||
| if (fallback.isDefinedAt(ex) && !ex.isInstanceOf[ReturnThrowable[_]]) fallback(ex) else throw ex |
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Maybe E should b a subtype of Exception to avoid catching other Throwables like ReturnThrowable.
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This is open to discussion --- this is the case where users specify handled exceptions explicitly, but indeed ReturnThrowable should never be handled by user programs.
nicolasstucki
approved these changes
Aug 27, 2019
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This implements inline
rescuelike those in Ruby [1], but more powerfulin that users can specify the exception to be handled.
The
rescuemethod will be very convenient in scripting.[1] https://stackoverflow.com/questions/15396791/ruby-oneline-rescue
[2] https://bugs.ruby-lang.org/issues/6739