Use Option::and_then instead of open-coding it

compiler/rustc_codegen_ssa/src/mir/block.rs

@@ -37,12 +37,9 @@ impl<'a, 'tcx> TerminatorCodegenHelper<'tcx> {
     /// `funclet_bb` member if it is not `None`.
     fn funclet<'b, Bx: BuilderMethods<'a, 'tcx>>(
         &self,
-        fx: &'b mut FunctionCx<'a, 'tcx, Bx>,
+        fx: &'b FunctionCx<'a, 'tcx, Bx>,
     ) -> Option<&'b Bx::Funclet> {
-        match self.funclet_bb {
-            Some(funcl) => fx.funclets[funcl].as_ref(),
-            None => None,
-        }
+        self.funclet_bb.and_then(|funcl| fx.funclets[funcl].as_ref())
     }
 
     fn lltarget<Bx: BuilderMethods<'a, 'tcx>>(