Auto merge of #34638 - zackmdavis:if_let_over_none_empty_block_arm, r=jseyfried

prefer `if let` to match with `None => {}` arm in some places

This is a spiritual succesor to #34268 / 8531d581, in which we replaced a
number of matches of None to the unit value with `if let` conditionals
where it was judged that this made for clearer/simpler code (as would be
recommended by Manishearth/rust-clippy's `single_match` lint). The same
rationale applies to matches of None to the empty block.

----

r? @jseyfried

2 files changed, 5 insertions, 9 deletions

diff --git a/src/libsyntax/ext/base.rs b/src/libsyntax/ext/base.rs
index ca38ef068d0..92670cd9def 100644
--- a/src/libsyntax/ext/base.rs
+++ b/src/libsyntax/ext/base.rs
@@ -944,9 +944,8 @@ impl SyntaxEnv {
 
     pub fn find(&self, k: Name) -> Option<Rc<SyntaxExtension>> {
         for frame in self.chain.iter().rev() {
-            match frame.map.get(&k) {
-                Some(v) => return Some(v.clone()),
-                None => {}
+            if let Some(v) = frame.map.get(&k) {
+                return Some(v.clone());
             }
         }
         None
diff --git a/src/libsyntax/ext/tt/transcribe.rs b/src/libsyntax/ext/tt/transcribe.rs
index 58328eb4246..40944a9a1c2 100644
--- a/src/libsyntax/ext/tt/transcribe.rs
+++ b/src/libsyntax/ext/tt/transcribe.rs
@@ -225,12 +225,9 @@ pub fn tt_next_token(r: &mut TtReader) -> TokenAndSpan {
         } else { /* repeat */
             *r.repeat_idx.last_mut().unwrap() += 1;
             r.stack.last_mut().unwrap().idx = 0;
-            match r.stack.last().unwrap().sep.clone() {
-                Some(tk) => {
-                    r.cur_tok = tk; /* repeat same span, I guess */
-                    return ret_val;
-                }
-                None => {}
+            if let Some(tk) = r.stack.last().unwrap().sep.clone() {
+                r.cur_tok = tk; // repeat same span, I guess
+                return ret_val;
             }
         }
     }