diff --git a/src/librustc/mir/mod.rs b/src/librustc/mir/mod.rs
index f7bd1ac5501..814c244ecbc 100644
--- a/src/librustc/mir/mod.rs
+++ b/src/librustc/mir/mod.rs
@@ -242,7 +242,7 @@ impl<'tcx> Body<'tcx> {
     pub fn vars_iter<'a>(&'a self) -> impl Iterator<Item = Local> + 'a {
         (self.arg_count + 1..self.local_decls.len()).filter_map(move |index| {
             let local = Local::new(index);
-            self.local_decls[local].is_user_variable().to_option(local)
+            self.local_decls[local].is_user_variable().then_some(local)
         })
     }
 
diff --git a/src/librustc_mir/lib.rs b/src/librustc_mir/lib.rs
index df0f4e9a9c5..42b72b64f8a 100644
--- a/src/librustc_mir/lib.rs
+++ b/src/librustc_mir/lib.rs
@@ -28,7 +28,6 @@ Rust MIR: a lowered representation of Rust. Also: an experiment!
 #![feature(associated_type_bounds)]
 #![feature(range_is_empty)]
 #![feature(stmt_expr_attributes)]
-#![feature(bool_to_option)]
 #![feature(trait_alias)]
 #![feature(matches_macro)]
 
diff --git a/src/librustc_mir/transform/uninhabited_enum_branching.rs b/src/librustc_mir/transform/uninhabited_enum_branching.rs
index de070d75ad8..26081d93946 100644
--- a/src/librustc_mir/transform/uninhabited_enum_branching.rs
+++ b/src/librustc_mir/transform/uninhabited_enum_branching.rs
@@ -29,7 +29,7 @@ fn get_switched_on_type<'tcx>(
     // Only bother checking blocks which terminate by switching on a local.
     if let Some(local) = get_discriminant_local(&terminator.kind) {
         let stmt_before_term = (block_data.statements.len() > 0)
-            .then_with(|| &block_data.statements[block_data.statements.len() - 1].kind);
+            .then(|| &block_data.statements[block_data.statements.len() - 1].kind);
 
         if let Some(StatementKind::Assign(box (l, Rvalue::Discriminant(place)))) = stmt_before_term
         {
@@ -59,7 +59,7 @@ fn variant_discriminants<'tcx>(
             .iter_enumerated()
             .filter_map(|(idx, layout)| {
                 (layout.abi != Abi::Uninhabited)
-                    .then_with(|| ty.discriminant_for_variant(tcx, idx).unwrap().val)
+                    .then(|| ty.discriminant_for_variant(tcx, idx).unwrap().val)
             })
             .collect(),
     }
diff --git a/src/librustc_parse/lib.rs b/src/librustc_parse/lib.rs
index a222f3f00c4..69050534ee6 100644
--- a/src/librustc_parse/lib.rs
+++ b/src/librustc_parse/lib.rs
@@ -1,5 +1,6 @@
 //! The main parser interface.
 
+#![feature(bool_to_option)]
 #![feature(crate_visibility_modifier)]
 
 use syntax::ast;