Collect directly into ThinVec

Author: notriddle

Diff for: src/librustdoc/clean/mod.rs

@@ -516,8 +516,7 @@ fn projection_to_path_segment<'tcx>(
                 ty.map_bound(|ty| &ty.args[generics.parent_count..]),
                 false,
                 def_id,
-            )
-            .into(),
+            ),
             constraints: Default::default(),
         },
     }
@@ -2202,8 +2201,7 @@ pub(crate) fn clean_middle_ty<'tcx>(
                             alias_ty.map_bound(|ty| ty.args.as_slice()),
                             true,
                             def_id,
-                        )
-                        .into(),
+                        ),
                         constraints: Default::default(),
                     },
                 },
@@ -2521,7 +2519,7 @@ fn clean_generic_args<'tcx>(
 ) -> GenericArgs {
     // FIXME(return_type_notation): Fix RTN parens rendering
     if let Some((inputs, output)) = generic_args.paren_sugar_inputs_output() {
-        let inputs = inputs.iter().map(|x| clean_ty(x, cx)).collect::<Vec<_>>().into();
+        let inputs = inputs.iter().map(|x| clean_ty(x, cx)).collect::<ThinVec<_>>().into();
         let output = match output.kind {
             hir::TyKind::Tup(&[]) => None,
             _ => Some(Box::new(clean_ty(output, cx))),
@@ -2542,7 +2540,7 @@ fn clean_generic_args<'tcx>(
                 }
                 hir::GenericArg::Infer(_inf) => GenericArg::Infer,
             })
-            .collect::<Vec<_>>()
+            .collect::<ThinVec<_>>()
             .into();
         let constraints = generic_args
             .constraints

Diff for: src/librustdoc/clean/utils.rs

@@ -81,11 +81,11 @@ pub(crate) fn clean_middle_generic_args<'tcx>(
     args: ty::Binder<'tcx, &'tcx [ty::GenericArg<'tcx>]>,
     mut has_self: bool,
     owner: DefId,
-) -> Vec<GenericArg> {
+) -> ThinVec<GenericArg> {
     let (args, bound_vars) = (args.skip_binder(), args.bound_vars());
     if args.is_empty() {
         // Fast path which avoids executing the query `generics_of`.
-        return Vec::new();
+        return ThinVec::new();
     }
 
     // If the container is a trait object type, the arguments won't contain the self type but the
@@ -144,7 +144,7 @@ pub(crate) fn clean_middle_generic_args<'tcx>(
     };
 
     let offset = if has_self { 1 } else { 0 };
-    let mut clean_args = Vec::with_capacity(args.len().saturating_sub(offset));
+    let mut clean_args = ThinVec::with_capacity(args.len().saturating_sub(offset));
     clean_args.extend(args.iter().enumerate().rev().filter_map(clean_arg));
     clean_args.reverse();
     clean_args