On Wednesday, 19 March 2014 at 20:43:59 UTC, Frustrated wrote:
On Wednesday, 19 March 2014 at 16:57:38 UTC, dnspies wrote:
I have a function called at CTFE which includes the lines:
97 if(conjunction exp = cast(conjunction)this_exp) {
98 inner_substitutions!(first,conjunction)(exp, map);
99 } else if(disjunction exp = cast(disjunction)this_exp) {
100 inner_substitutions!(first,disjunction)(exp, map);
101 }
Here, this_exp is a reference of type "expression" to an
object whose CTFE-runtime-type is of type "disjunction".
conjunction and disjunction are both descendent classes of
expression.
This code produces the following compilation error:
source/cfgparse.d(97): Error: cannot cast [...] to
cfgparse.conjunction at compile time.
([...] stands in for a very long string which I think is some
sort of representation of this_exp)
Just for the hell of it, I tried moving the assignment out of
the conditional, and something very strange happens.
97 if(cast(conjunction)this_exp) {
98 conjunction exp = cast(conjunction)this_exp;
99 inner_substitutions!(first,conjunction)(exp, map);
100 } else if(cast(disjunction)this_exp) {
101 disjunction exp = cast(disjunction)this_exp;
102 inner_substitutions!(first,disjunction)(exp, map);
103 }
source/cfgparse.d(101): Error: cannot cast [...] to
cfgparse.disjunction at compile time
Both the conditions compile properly, and now only the
assignment fails. Why is this happening and how can I avoid
it?
I ran up to a similar situation when the thing trying to be
cast was not what I thought it was. I.e., the error is exactly
what it means. Try to create a this_exp that is a conjunction
explicitly to see if that is the problem.
Sorry, I don't understand. When I cast something to the wrong
type, I should just get a null reference, shouldn't I? It
shouldn't throw an error.
