/
visitor.d
78 lines (67 loc) · 2.28 KB
/
visitor.d
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module visitor;
U fastCast(U, T)(T t) if(is(T == class) && is(U == class) && is(U : T)) in {
assert(cast(U) t);
} body {
return *(cast(U*) &t);
}
auto dispatch(
alias unhandled = function void(t) {
throw new Exception(typeid(t).toString() ~ " is not supported.");
// XXX: Buggy for some reason.
// throw new Exception(typeid(t).toString() ~ " is not supported by visitor " ~ typeid(V).toString() ~ " .");
}, V, T, Args...
)(ref V visitor, Args args, T t) if(is(V == struct) && (is(T == class) || is(T == interface))) {
return dispatchImpl!(unhandled)(visitor, args, t);
}
auto dispatch(
alias unhandled = function void(t) {
throw new Exception(typeid(t).toString() ~ " is not supported.");
// XXX: Buggy for some reason.
// throw new Exception(typeid(t).toString() ~ " is not supported by visitor " ~ typeid(V).toString() ~ " .");
}, V, T, Args...
)(V visitor, Args args, T t) if((is(V == class) || is(V == interface)) && (is(T == class) || is(T == interface))) {
return dispatchImpl!(unhandled)(visitor, args, t);
}
// XXX: is @trusted if visitor.visit is @safe .
private auto dispatchImpl(
alias unhandled, V, T, Args...
)(auto ref V visitor, Args args, T t) in {
assert(t, "You can't dispatch null");
} body {
static if(is(T == class)) {
alias o = t;
} else {
auto o = cast(Object) t;
}
auto tid = typeid(o);
import std.traits;
static if(is(V == struct)) {
import std.typetuple;
alias Members = TypeTuple!(__traits(getOverloads, V, "visit"));
} else {
alias Members = MemberFunctionsTuple!(V, "visit");
}
foreach(visit; Members) {
alias parameters = ParameterTypeTuple!visit;
static if(parameters.length == args.length + 1) {
alias parameter = parameters[args.length];
// FIXME: ensure call is correctly done when args exists.
static if(is(parameter == class) && !__traits(isAbstractClass, parameter) && is(parameter : T)) {
if(tid is typeid(parameter)) {
return visitor.visit(args, () @trusted {
// Fast cast can be trusted in this case, we already did the check.
return fastCast!parameter(o);
} ());
}
}
}
}
// Dispatch isn't possible.
enum returnVoid = is(typeof(return) == void);
static if(returnVoid || is(typeof(unhandled(t)) == void)) {
unhandled(t);
assert(returnVoid);
} else {
return unhandled(t);
}
}