Fix is_valid_interval

Author: OlivierHnt

src/intervals/flavor.jl

@@ -91,5 +91,8 @@ contains_infinity(x::BareInterval) = contains_infinity(default_flavor(), x)
 For the given flavor `F`, test whether ``[a, b]`` is a valid interval.
 """
 is_valid_interval(::Flavor{:set_based}, a::Real, b::Real) = b - a ≥ 0
+# to prevent issues with division by zero, e.g. `is_valid_interval(1//0, 1//0)`
+is_valid_interval(::Flavor{:set_based}, a::Rational, b::Rational) =
+    !((a > b) | (a == typemax(typeof(a))) | (b == typemin(typeof(b))))
 
 is_valid_interval(a::Real, b::Real) = is_valid_interval(default_flavor(), a, b)