Rollup merge of #34268 - zackmdavis:if_let_over_none_unit_arm, r=jseyfried

prefer `if let` to match with `None => ()` arm in some places

Casual grepping revealed some places in the codebase (some of which
antedated `if let`'s December 2014 stabilization in c200ae5a) where we
were using a match with a `None => ()` arm where (in the present
author's opinion) an `if let` conditional would be more readable. (Other
places where matching to the unit value did seem to better express the
intent were left alone.)

It's likely that we don't care about making such trivial,
non-functional, sheerly æsthetic changes.

But if we do, this is a patch.

1 files changed, 4 insertions, 6 deletions

diff --git a/src/libsyntax/util/interner.rs b/src/libsyntax/util/interner.rs
index 8e20358027b..7295b36af0f 100644
--- a/src/libsyntax/util/interner.rs
+++ b/src/libsyntax/util/interner.rs
@@ -47,9 +47,8 @@ impl<T: Eq + Hash + Clone + 'static> Interner<T> {
 
     pub fn intern(&self, val: T) -> Name {
         let mut map = self.map.borrow_mut();
-        match (*map).get(&val) {
-            Some(&idx) => return idx,
-            None => (),
+        if let Some(&idx) = (*map).get(&val) {
+            return idx;
         }
 
         let mut vect = self.vect.borrow_mut();
@@ -161,9 +160,8 @@ impl StrInterner {
 
     pub fn intern(&self, val: &str) -> Name {
         let mut map = self.map.borrow_mut();
-        match map.get(val) {
-            Some(&idx) => return idx,
-            None => (),
+        if let Some(&idx) = map.get(val) {
+            return idx;
         }
 
         let new_idx = Name(self.len() as u32);