Don't collect() when size_hint is useless

1 files changed, 6 insertions, 1 deletions

diff --git a/src/librustc_data_structures/small_vec.rs b/src/librustc_data_structures/small_vec.rs
index 76b01beb4ba..e958fd7da61 100644
--- a/src/librustc_data_structures/small_vec.rs
+++ b/src/librustc_data_structures/small_vec.rs
@@ -210,7 +210,12 @@ 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| {
-            (0..len).map(|i| d.read_seq_elt(i, |d| Decodable::decode(d))).collect()
+            let mut vec = SmallVec::with_capacity(len);
+            // FIXME(#48994) - could just be collected into a Result<SmallVec, D::Error>
+            for i in 0..len {
+                vec.push(d.read_seq_elt(i, |d| Decodable::decode(d))?);
+            }
+            Ok(vec)
         })
     }
 }