Auto merge of #52697 - ljedrz:misc_data_structures, r=Mark-Simulacrum

Simplify a few functions in rustc_data_structures

- drop `try!()` where it's superfluous
- change `try!()` to `?`
- squash a `push` with `push_str`
- refactor a push loop into an iterator

Author: bors

src/librustc_data_structures/accumulate_vec.rs

@@ -224,7 +224,7 @@ impl<A> Encodable for AccumulateVec<A>
     fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
         s.emit_seq(self.len(), |s| {
             for (i, e) in self.iter().enumerate() {
-                try!(s.emit_seq_elt(i, |s| e.encode(s)));
+                s.emit_seq_elt(i, |s| e.encode(s))?;
             }
             Ok(())
         })
@@ -236,8 +236,7 @@ impl<A> Decodable for AccumulateVec<A>
           A::Element: Decodable {
     fn decode<D: Decoder>(d: &mut D) -> Result<AccumulateVec<A>, D::Error> {
         d.read_seq(|d, len| {
-            Ok(try!((0..len).map(|i| d.read_seq_elt(i, |d| Decodable::decode(d))).collect()))
+            (0..len).map(|i| d.read_seq_elt(i, |d| Decodable::decode(d))).collect()
         })
     }
 }
-

src/librustc_data_structures/bitslice.rs

@@ -95,8 +95,7 @@ pub fn bits_to_string(words: &[Word], bits: usize) -> String {
             assert!(mask <= 0xFF);
             let byte = v & mask;
 
-            result.push(sep);
-            result.push_str(&format!("{:02x}", byte));
+            result.push_str(&format!("{}{:02x}", sep, byte));
 
             if remain <= 8 { break; }
             v >>= 8;

src/librustc_data_structures/small_vec.rs

@@ -197,7 +197,7 @@ impl<A> Encodable for SmallVec<A>
     fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
         s.emit_seq(self.len(), |s| {
             for (i, e) in self.iter().enumerate() {
-                try!(s.emit_seq_elt(i, |s| e.encode(s)));
+                s.emit_seq_elt(i, |s| e.encode(s))?;
             }
             Ok(())
         })
@@ -209,11 +209,7 @@ impl<A> Decodable for SmallVec<A>
           A::Element: Decodable {
     fn decode<D: Decoder>(d: &mut D) -> Result<SmallVec<A>, D::Error> {
         d.read_seq(|d, len| {
-            let mut vec = SmallVec::with_capacity(len);
-            for i in 0..len {
-                vec.push(try!(d.read_seq_elt(i, |d| Decodable::decode(d))));
-            }
-            Ok(vec)
+            (0..len).map(|i| d.read_seq_elt(i, |d| Decodable::decode(d))).collect()
         })
     }
 }