simplify Safety pretty-printing

No need to customize the Debug impl any more

Author: lqd

crates/formality-prove/src/decls.rs

@@ -1,5 +1,3 @@
-use std::fmt;
-
 use formality_core::{set, Set, Upcast};
 use formality_macros::term;
 use formality_types::grammar::{
@@ -144,23 +142,13 @@ pub struct NegImplDeclBoundData {
 
 /// Mark a trait or trait impl as `unsafe`.
 #[term]
-#[customize(debug)]
 #[derive(Default)]
 pub enum Safety {
     #[default]
     Safe,
     Unsafe,
 }
 
-impl fmt::Debug for Safety {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        match self {
-            Safety::Safe => write!(f, "safe"),
-            Safety::Unsafe => write!(f, "unsafe"),
-        }
-    }
-}
-
 /// A "trait declaration" declares a trait that exists, its generics, and its where-clauses.
 /// It doesn't capture the trait items, which will be transformed into other sorts of rules.
 ///