use &'a lifetime rather than &'self

this simplifies things and eliminates a usage of `unsafe`.

core/src/identifier.rs

@@ -258,12 +258,8 @@ mod interner {
  ///
  /// This operation cannot fails since the only way to have a [Symbol] is to have
  /// [interned](Interner::intern) the corresponding string first.
- pub(crate) fn lookup<'slf>(&'slf self, sym: Symbol) -> &'slf str {
- // SAFETY: We are making the returned &str lifetime the same as our struct,
- // which is okay here since the InnerInterner uses a typed_arena which prevents
- // deallocations, so the reference will be valid while the InnerInterner exists,
- // hence while the struct exists.
- unsafe { std::mem::transmute::<&'_ str, &'slf str>(self.0.read().unwrap().lookup(sym)) }
+ pub(crate) fn lookup(&self, sym: Symbol) -> &'a str {
+ self.0.read().unwrap().lookup(sym)
  }
  }
 
@@ -315,7 +311,7 @@ mod interner {
  ///
  /// This operation cannot fails since the only way to have a [Symbol]
  /// is to have [interned](InnerInterner::intern) the corresponding string first.
- fn lookup<'slf>(&'slf self, sym: Symbol) -> &'slf str {
+ fn lookup(&self, sym: Symbol) -> &'a str {
  self.vec[sym.0 as usize]
  }
  }