Enable overflow-checks and fix a bug that slipped through during their absence. (#231)

* Fixed bug in `average_higher`, due to wrong assumptions about operator precendence.

* Enable overflow checks in `--release` tests.

This will hardly impact test performance, as the heavy lifting is done in the threshold crypto crate. Rough benchmarks showed significant differences only when `overflow-checks` was enable for `[profile.release]` (instead of `[profile.bench]`), causing it to be applied to `threshold_crypto` as well.

Cargo.toml

@@ -47,3 +47,9 @@ name = "consensus-node"
 
 [[example]]
 name = "simulation"
+
+# This will turn on overflow checks in `cargo test --release` and
+# `cargo bench`. Dependencies will not be affected, as they use the
+# `[profile.release]` block in both cases.
+[profile.bench]
+overflow-checks = true

tests/net/proptest.rs

@@ -54,7 +54,7 @@ impl NetworkDimension {
         };
 
         // Reduce the number of faulty nodes, if we are outside our limits.
-        if !half.faulty * 3 <= half.size {
+        if !(half.faulty * 3 <= half.size) {
             half.faulty -= 1;
         }