Use to_option in various places

src/librustc/hir/map/blocks.rs

@@ -147,13 +147,7 @@ impl<'a> FnLikeNode<'a> {
             map::Node::Expr(e) => e.is_fn_like(),
             _ => false
         };
-        if fn_like {
-            Some(FnLikeNode {
-                node,
-            })
-        } else {
-            None
-        }
+        fn_like.to_option(FnLikeNode { node })
     }
 
     pub fn body(self) -> ast::BodyId {

src/librustc/infer/outlives/verify.rs

@@ -211,11 +211,7 @@ impl<'cx, 'tcx> VerifyBoundCx<'cx, 'tcx> {
                 (r, p)
             );
             let p_ty = p.to_ty(tcx);
-            if compare_ty(p_ty) {
-                Some(ty::OutlivesPredicate(p_ty, r))
-            } else {
-                None
-            }
+            compare_ty(p_ty).to_option(ty::OutlivesPredicate(p_ty, r))
         });
 
         param_bounds

src/librustc/lib.rs

@@ -29,6 +29,7 @@
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/")]
 
 #![feature(arbitrary_self_types)]
+#![feature(bool_to_option)]
 #![feature(box_patterns)]
 #![feature(box_syntax)]
 #![feature(const_fn)]

src/librustc/mir/mod.rs

@@ -242,11 +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);
-            if self.local_decls[local].is_user_variable() {
-                Some(local)
-            } else {
-                None
-            }
+            self.local_decls[local].is_user_variable().to_option(local)
         })
     }
 

src/librustc/traits/error_reporting.rs

@@ -363,11 +363,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
             return None
         };
 
-        if tcx.has_attr(impl_def_id, sym::rustc_on_unimplemented) {
-            Some(impl_def_id)
-        } else {
-            None
-        }
+        tcx.has_attr(impl_def_id, sym::rustc_on_unimplemented).to_option(impl_def_id)
     }
 
     fn describe_generator(&self, body_id: hir::BodyId) -> Option<&'static str> {

src/librustc/ty/mod.rs

@@ -2784,11 +2784,7 @@ impl<'tcx> TyCtxt<'tcx> {
             }
         };
 
-        if is_associated_item {
-            Some(self.associated_item(def_id))
-        } else {
-            None
-        }
+        is_associated_item.to_option_with(|| self.associated_item(def_id))
     }
 
     fn associated_item_from_trait_item_ref(self,
@@ -3253,7 +3249,7 @@ fn param_env(tcx: TyCtxt<'_>, def_id: DefId) -> ParamEnv<'_> {
     let unnormalized_env = ty::ParamEnv::new(
         tcx.intern_predicates(&predicates),
         traits::Reveal::UserFacing,
-        if tcx.sess.opts.debugging_opts.chalk { Some(def_id) } else { None }
+        tcx.sess.opts.debugging_opts.chalk.to_option(def_id),
     );
 
     let body_id = tcx.hir().as_local_hir_id(def_id).map_or(hir::DUMMY_HIR_ID, |id| {

src/librustc/ty/query/job.rs

@@ -303,13 +303,8 @@ fn connected_to_root<'tcx>(
         return true;
     }
 
-    visit_waiters(query, |_, successor| {
-        if connected_to_root(successor, visited) {
-            Some(None)
-        } else {
-            None
-        }
-    }).is_some()
+    visit_waiters(query, |_, successor| connected_to_root(successor, visited).to_option(None))
+        .is_some()
 }
 
 // Deterministically pick an query from a list