Fix clippy errors

Author: brendanzab

.github/workflows/ci.yml

@@ -75,7 +75,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        rust: ["1.42.0", "stable"]
+        rust: ["stable"]
         # rust: ["1.42.0", "stable", "beta", "nightly"]
     name: Clippy (${{ matrix.rust }})
     steps:

pikelet/src/pass/core_to_surface.rs

@@ -1,5 +1,7 @@
 //! Distill the core language into the surface language.
 
+#![allow(clippy::reversed_empty_ranges)]
+
 use std::collections::HashMap;
 
 use crate::lang::core::{Constant, Globals, Locals, Term, UniverseLevel, UniverseOffset};