Utilize ? instead of return None.

src/libcore/num/flt2dec/mod.rs

@@ -239,10 +239,8 @@ impl<'a> Formatted<'a> {
 
         let mut written = self.sign.len();
         for part in self.parts {
-            match part.write(&mut out[written..]) {
-                Some(len) => { written += len; }
-                None => { return None; }
-            }
+            let len = part.write(&mut out[written..])?;
+            written += len;
         }
         Some(written)
     }

src/librustc/traits/util.rs

@@ -292,11 +292,7 @@ impl<'cx, 'gcx, 'tcx> Iterator for SupertraitDefIds<'cx, 'gcx, 'tcx> {
     type Item = DefId;
 
     fn next(&mut self) -> Option<DefId> {
-        let def_id = match self.stack.pop() {
-            Some(def_id) => def_id,
-            None => { return None; }
-        };
-
+        let def_id = self.stack.pop()?;
         let predicates = self.tcx.super_predicates_of(def_id);
         let visited = &mut self.visited;
         self.stack.extend(

src/librustc_typeck/check/mod.rs

@@ -5318,10 +5318,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
     ) -> Option<Span> {
         // Be helpful when the user wrote `{... expr;}` and
         // taking the `;` off is enough to fix the error.
-        let last_stmt = match blk.stmts.last() {
-            Some(s) => s,
-            None => return None,
-        };
+        let last_stmt = blk.stmts.last()?;
         let last_expr = match last_stmt.node {
             hir::StmtKind::Semi(ref e) => e,
             _ => return None,