log inconsistent bitfield state

Cargo.toml

@@ -6,3 +6,4 @@ authors = ["Parity Technologies <admin@parity.io>"]
 
 [dependencies]
 parking_lot = "0.4"
+log = "0.4"

src/bitfield.rs

@@ -175,11 +175,13 @@ impl<Id: Eq> LiveBitfield<Id> {
 		let word_off = bit_idx / 64;
 		let bit_off = bit_idx % 64;
 
-		// TODO: if this isn't `Some`, something has gone really wrong.
-		// log it?
+		// If this isn't `Some`, something has gone really wrong.
 		if let Some(word) = self.bits.get_mut(word_off) {
 			// set bit starting from left.
 			*word |= 1 << (63 - bit_off)
+		} else {
+			warn!(target: "afg", "Could not set bit {}. Bitfield was meant to have 2 bits for each of {} validators.",
+				bit_idx, self.shared.n_validators);
 		}
 	}
 

src/lib.rs

@@ -19,6 +19,8 @@
 //! https://hackmd.io/iA4XazxWRJ21LqMxwPSEZg?view
 
 extern crate parking_lot;
+#[macro_use]
+extern crate log;
 
 pub mod bitfield;
 pub mod round;