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.

1 files changed, 6 insertions, 12 deletions

diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index 94b71661bc2..ce30c3de759 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -1264,13 +1264,10 @@ impl<'a> State<'a> {
                     _ => {}
                 }
 
-                match *opt_trait {
-                    Some(ref t) => {
-                        try!(self.print_trait_ref(t));
-                        try!(space(&mut self.s));
-                        try!(self.word_space("for"));
-                    }
-                    None => {}
+                if let Some(ref t) = *opt_trait {
+                    try!(self.print_trait_ref(t));
+                    try!(space(&mut self.s));
+                    try!(self.word_space("for"));
                 }
 
                 try!(self.print_type(&ty));
@@ -1470,11 +1467,8 @@ impl<'a> State<'a> {
                     try!(self.print_tt(tt_elt));
                 }
                 try!(word(&mut self.s, ")"));
-                match seq.separator {
-                    Some(ref tk) => {
-                        try!(word(&mut self.s, &token_to_string(tk)));
-                    }
-                    None => {},
+                if let Some(ref tk) = seq.separator {
+                    try!(word(&mut self.s, &token_to_string(tk)));
                 }
                 match seq.op {
                     tokenstream::KleeneOp::ZeroOrMore => word(&mut self.s, "*"),