implement valtrees as the type-system representation for constant values

compiler/rustc_middle/src/ty/instance.rs

@@ -369,7 +369,6 @@ impl<'tcx> Instance<'tcx> {
     }
 
     // This should be kept up to date with `resolve`.
-    #[instrument(level = "debug", skip(tcx))]
     pub fn resolve_opt_const_arg(
         tcx: TyCtxt<'tcx>,
         param_env: ty::ParamEnv<'tcx>,