[bitc-dev] Accurate static typing vs. Dependent Types
david.hopwood at industrial-designers.co.uk
Mon Dec 8 23:35:13 CST 2008
Jonathan S. Shapiro wrote:
> The rule in Java is that exception declarations must be exhaustive, but only
> if they are present.
That's not correct. Exception declarations must always be exhaustive, except
that subclasses of Error and RuntimeException are implicitly throwable.
This doesn't really affect your conclusions, though.
> In Java, the workaround for all of this rests in the
> object hierarchy, and the common fix is to declare that a procedure throws
> the Exception superclass, which serves as a catch-all.
> Note that the existence of a catch-all eliminates the possibility of more
> efficient compilation.
It's never feasible to compile under the assumption that exceptions are
not thrown, because many common primitive operations (e.g. array index,
referencing a field or method of a nullable variable, etc.) can implicitly
throw exceptions. Whether exceptions are declared has nothing to do with
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