Better handling of approval_stake == 0

primitives/arithmetic/src/rational.rs

@@ -17,7 +17,7 @@
 
 use sp_std::{cmp::Ordering, prelude::*};
 use crate::helpers_128bit;
-use num_traits::{Zero, One};
+use num_traits::{Zero, One, Bounded};
 use crate::biguint::BigUint;
 
 /// A wrapper for any rational number with infinitely large numerator and denominator.
@@ -209,6 +209,16 @@ impl Rational128 {
 	}
 }
 
+impl Bounded for Rational128 {
+	fn min_value() -> Self {
+		Self(0, 1)
+	}
+
+	fn max_value() -> Self {
+		Self(Bounded::max_value(), 1)
+	}
+}
+
 impl<T: Into<u128>> From<T> for Rational128 {
 	fn from(t: T) -> Self {
 		Self::from(t.into(), 1)

primitives/npos-elections/src/phragmen.rs

@@ -125,7 +125,7 @@ pub fn seq_phragmen_core<AccountId: IdentifierT>(
 				// 1 / approval_stake == (DEN / approval_stake) / DEN. If approval_stake is zero,
 				// then the ratio should be as large as possible, essentially `infinity`.
 				if candidate.approval_stake.is_zero() {
-					candidate.score = Rational128::from_unchecked(DEN, 0);
+					candidate.score = Bounded::max_value();
 				} else {
 					candidate.score = Rational128::from(DEN / candidate.approval_stake, DEN);
 				}