Use Option::map instead of open-coding it

Author: LingMan

compiler/rustc_codegen_llvm/src/llvm_util.rs

@@ -254,8 +254,6 @@ pub fn handle_native_features(sess: &Session) -> Vec<String> {
 }
 
 pub fn tune_cpu(sess: &Session) -> Option<&str> {
-    match sess.opts.debugging_opts.tune_cpu {
-        Some(ref s) => Some(handle_native(&**s)),
-        None => None,
-    }
+    let name = sess.opts.debugging_opts.tune_cpu.as_ref()?;
+    Some(handle_native(name))
 }

compiler/rustc_mir/src/borrow_check/type_check/input_output.rs

@@ -39,10 +39,8 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             user_provided_sig = None;
         } else {
             let typeck_results = self.tcx().typeck(mir_def_id);
-            user_provided_sig = match typeck_results.user_provided_sigs.get(&mir_def_id.to_def_id())
-            {
-                None => None,
-                Some(user_provided_poly_sig) => {
+            user_provided_sig = typeck_results.user_provided_sigs.get(&mir_def_id.to_def_id()).map(
+                |user_provided_poly_sig| {
                     // Instantiate the canonicalized variables from
                     // user-provided signature (e.g., the `_` in the code
                     // above) with fresh variables.
@@ -54,18 +52,16 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                     // Replace the bound items in the fn sig with fresh
                     // variables, so that they represent the view from
                     // "inside" the closure.
-                    Some(
-                        self.infcx
-                            .replace_bound_vars_with_fresh_vars(
-                                body.span,
-                                LateBoundRegionConversionTime::FnCall,
-                                poly_sig,
-                            )
-                            .0,
-                    )
-                }
-            }
-        };
+                    self.infcx
+                        .replace_bound_vars_with_fresh_vars(
+                            body.span,
+                            LateBoundRegionConversionTime::FnCall,
+                            poly_sig,
+                        )
+                        .0
+                },
+            );
+        }
 
         debug!(
             "equate_inputs_and_outputs: normalized_input_tys = {:?}, local_decls = {:?}",

compiler/rustc_typeck/src/check/compare_method.rs

@@ -365,12 +365,10 @@ fn check_region_bounds_on_impl_item<'tcx>(
         let item_kind = assoc_item_kind_str(impl_m);
         let def_span = tcx.sess.source_map().guess_head_span(span);
         let span = tcx.hir().get_generics(impl_m.def_id).map_or(def_span, |g| g.span);
-        let generics_span = if let Some(sp) = tcx.hir().span_if_local(trait_m.def_id) {
+        let generics_span = tcx.hir().span_if_local(trait_m.def_id).map(|sp| {
             let def_sp = tcx.sess.source_map().guess_head_span(sp);
-            Some(tcx.hir().get_generics(trait_m.def_id).map_or(def_sp, |g| g.span))
-        } else {
-            None
-        };
+            tcx.hir().get_generics(trait_m.def_id).map_or(def_sp, |g| g.span)
+        });
 
         tcx.sess.emit_err(LifetimesOrBoundsMismatchOnTrait {
             span,