Fix tools

compiler/rustc_middle/src/ty/mod.rs

@@ -1257,11 +1257,11 @@ impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for ParamEnv<'tcx> {
 
 impl<'tcx> TypeFoldable<'tcx> for ParamEnv<'tcx> {
     fn super_fold_with<F: ty::fold::TypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
-        ParamEnv::new(
+        Ok(ParamEnv::new(
             self.caller_bounds().fold_with(folder)?,
             self.reveal().fold_with(folder)?,
             self.constness().fold_with(folder)?,
-        )
+        ))
     }
 
     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {