[perf] rustdoc: Perform less work when cleaning parenthesized generic args

Author: fmease

src/librustdoc/clean/mod.rs

@@ -2119,7 +2119,7 @@ pub(crate) fn clean_middle_ty<'tcx>(
 })
 .collect::<Vec<_>>();
 
-letbindings = obj
+letconstraints = obj
 .projection_bounds()
 .map(|pb| AssocItemConstraint{
 assoc:projection_to_path_segment(
@@ -2155,7 +2155,7 @@ pub(crate) fn clean_middle_ty<'tcx>(
 .collect();
 let late_bound_regions = late_bound_regions.into_iter().collect();
 
-let path = clean_middle_path(cx, did,false,bindings, args);
+let path = clean_middle_path(cx, did,false,constraints, args);
  bounds.insert(0,PolyTrait{trait_: path,generic_params: late_bound_regions });
 
 DynTrait(bounds, lifetime)

src/librustdoc/clean/utils.rs

@@ -112,7 +112,6 @@ pub(crate) fn clean_middle_generic_args<'tcx>(
 returnNone;
 }
 
-// Elide internal host effect args.
 let param = generics.param_at(index, cx.tcx);
 let arg = ty::Binder::bind_with_vars(arg, bound_vars);
 
@@ -201,35 +200,30 @@ fn clean_middle_generic_args_with_constraints<'tcx>(
 cx:&mutDocContext<'tcx>,
 did:DefId,
 has_self:bool,
-constraints:ThinVec<AssocItemConstraint>,
-ty_args: ty::Binder<'tcx,GenericArgsRef<'tcx>>,
+mutconstraints:ThinVec<AssocItemConstraint>,
+args: ty::Binder<'tcx,GenericArgsRef<'tcx>>,
 ) -> GenericArgs{
-let args = clean_middle_generic_args(cx, ty_args.map_bound(|args| &args[..]), has_self, did);
-
-if cx.tcx.is_trait(did) && cx.tcx.trait_def(did).paren_sugar{
-let ty = ty_args
+if cx.tcx.is_trait(did)
+ && cx.tcx.trait_def(did).paren_sugar
+ && let ty::Tuple(tys) = args.skip_binder().type_at(has_self asusize).kind()
+{
+let inputs = tys
 .iter()
-.nth(if has_self {1}else{0})
-.unwrap()
-.map_bound(|arg| arg.expect_ty());
-let inputs =
-// The trait's first substitution is the one after self, if there is one.
-match ty.skip_binder().kind(){
- ty::Tuple(tys) => tys.iter().map(|t| clean_middle_ty(ty.rebind(t), cx,None,None)).collect::<Vec<_>>().into(),
- _ => returnGenericArgs::AngleBracketed{args: args.into(), constraints },
-};
-let output = constraints.into_iter().next().and_then(|binding| match binding.kind{
-AssocItemConstraintKind::Equality{term:Term::Type(ty)}
-if ty != Type::Tuple(Vec::new()) =>
-{
+.map(|ty| clean_middle_ty(args.rebind(ty), cx,None,None))
+.collect::<Vec<_>>()
+.into();
+let output = constraints.pop().and_then(|constraint| match constraint.kind{
+AssocItemConstraintKind::Equality{term:Term::Type(ty)}if !ty.is_unit() => {
 Some(Box::new(ty))
 }
  _ => None,
 });
-GenericArgs::Parenthesized{ inputs, output }
-}else{
-GenericArgs::AngleBracketed{args: args.into(), constraints }
+returnGenericArgs::Parenthesized{ inputs, output };
 }
+
+let args = clean_middle_generic_args(cx, args.map_bound(|args| &args[..]), has_self, did);
+
+GenericArgs::AngleBracketed{args: args.into(), constraints }
 }
 
 pub(super)fnclean_middle_path<'tcx>(