You could use
import 'dart:mirrors';
class A {
}
class B extends A {
}
class C extends A {
}
void main(args) {
var a = 1.1;
var b = 1;
var x = reflect(b);
print(x.type.isSubtypeOf(reflectType(num)));
print(x.type.isAssignableTo(reflectType(num)));
print(x.type.isAssignableTo(reflectType(double)));
var myb = new B();
print(reflect(myb).type.isSubtypeOf(reflectType(A)));
print(reflect(myb).type.isAssignableTo(reflectType(A)));
print(reflect(myb).type.isAssignableTo(reflectType(C)));
}