nit: cleanups in Cfg::simplify_with

src/librustdoc/clean/cfg.rs

@@ -224,30 +224,28 @@ impl Cfg {
     /// `Cfg`.
     ///
     /// See `tests::test_simplify_with` for examples.
-    pub(crate) fn simplify_with(&self, assume: &Cfg) -> Option<Cfg> {
+    pub(crate) fn simplify_with(&self, assume: &Self) -> Option<Self> {
         if self == assume {
-            return None;
-        }
-
-        if let Cfg::All(a) = self {
+            None
+        } else if let Cfg::All(a) = self {
             let mut sub_cfgs: Vec<Cfg> = if let Cfg::All(b) = assume {
                 a.iter().filter(|a| !b.contains(a)).cloned().collect()
             } else {
                 a.iter().filter(|&a| a != assume).cloned().collect()
             };
             let len = sub_cfgs.len();
-            return match len {
+            match len {
                 0 => None,
                 1 => sub_cfgs.pop(),
                 _ => Some(Cfg::All(sub_cfgs)),
-            };
-        } else if let Cfg::All(b) = assume {
-            if b.contains(self) {
-                return None;
             }
+        } else if let Cfg::All(b) = assume
+            && b.contains(self)
+        {
+            None
+        } else {
+            Some(self.clone())
         }
-
-        Some(self.clone())
     }
 }