Fix regression in Range.int-bounds

Yesterday's fix[^1] to the method assumed an .Int on endpoints will be
False only if the conversion returns a Failure, but it's possible to
construct a non-int Range with `0` as one of the end-points, whose
.Int is False.

Fix by adding additional type checks that .Int's are Int

[1] 79f2681004224108b2acd18bec2

src/core/Range.pm

@@ -382,7 +382,8 @@ my class Range is Cool does Iterable does Positional {
             nqp::istype($!min,Real)
               && $!min.floor == $!min
               && nqp::istype($!max,Real)
-              && $!min.Int && $!max.Int, # exclude NaN and Infs, who will fail() here
+              && nqp::istype($!min.Int, Int)  # exclude NaN and Infs, who will fail() here
+              && nqp::istype($!max.Int, Int),
             nqp::stmts(
               ($from = $!min.floor + $!excludes-min),
               ($to   = $!max.floor - ($!excludes-max && $!max.Int == $!max))
@@ -395,7 +396,8 @@ my class Range is Cool does Iterable does Positional {
         $!is-int
           ?? ($!min + $!excludes-min, $!max - $!excludes-max)
           !! nqp::istype($!min,Real) && $!min.floor == $!min && nqp::istype($!max,Real)
-                && $!min.Int && $!max.Int # exclude NaN and Infs, who will fail() here
+                && nqp::istype($!min.Int, Int) # exclude NaN and Infs, who will fail() here
+                && nqp::istype($!max.Int, Int)
             ?? ($!min.floor + $!excludes-min, $!max.floor - ($!excludes-max && $!max.Int == $!max))
             !! Failure.new("Cannot determine integer bounds")
     }