Auto merge of #53824 - ljedrz:begone_onevector, r=michaelwoerister

Remove OneVector, increase related SmallVec capacities

Removes the `OneVector` type alias (equivalent to `SmallVec<[T; 1]>`); it is used in scenarios where the capacity of 1 is often exceeded, which might be nullifying the performance wins (due to spilling to the heap) expected when using `SmallVec` instead of `Vec`.

The numbers I used in this PR are very rough estimates - it would probably be a good idea to adjust some/all of them, which is what this proposal is all about.

It might be a good idea to additionally create some local type aliases for the `SmallVec`s in the `Folder` trait, as they are repeated in quite a few spots; I'd be happy to apply this sort of adjustments.

1 files changed, 4 insertions, 4 deletions

diff --git a/src/libsyntax/ext/source_util.rs b/src/libsyntax/ext/source_util.rs
index e4b9e3216b1..f5d1bd6255e 100644
--- a/src/libsyntax/ext/source_util.rs
+++ b/src/libsyntax/ext/source_util.rs
@@ -17,7 +17,7 @@ use parse::{token, DirectoryOwnership};
 use parse;
 use print::pprust;
 use ptr::P;
-use OneVector;
+use smallvec::SmallVec;
 use symbol::Symbol;
 use tokenstream;
 
@@ -110,9 +110,9 @@ pub fn expand_include<'cx>(cx: &'cx mut ExtCtxt, sp: Span, tts: &[tokenstream::T
         fn make_expr(mut self: Box<ExpandResult<'a>>) -> Option<P<ast::Expr>> {
             Some(panictry!(self.p.parse_expr()))
         }
-        fn make_items(mut self: Box<ExpandResult<'a>>)
-                      -> Option<OneVector<P<ast::Item>>> {
-            let mut ret = OneVector::new();
+
+        fn make_items(mut self: Box<ExpandResult<'a>>) -> Option<SmallVec<[P<ast::Item>; 1]>> {
+            let mut ret = SmallVec::new();
             while self.p.token != token::Eof {
                 match panictry!(self.p.parse_item()) {
                     Some(item) => ret.push(item),