Auto merge of #107637 - fmease:rustdoc-reelide-x-crate-def-tr-obj-lt-…

…bnds, r=notriddle,cgillot,GuillaumeGomez

rustdoc: re-elide cross-crate default trait-object lifetime bounds

Hide trait-object lifetime bounds (re-exported from an external crate) if they coincide with [their default](https://doc.rust-lang.org/reference/lifetime-elision.html#default-trait-object-lifetimes).
Partially addresses #44306. Follow-up to #103885. [Zulip discussion](https://rust-lang.zulipchat.com/#narrow/stream/266220-rustdoc/topic/clean_middle_ty.3A.20I.20need.20to.20add.20a.20parameter/near/307143097).

Most notably, if `std` exported something from `core` containing a type like `Box<dyn Fn()>`, then it would now be rendered as `Box<dyn Fn(), Global>` instead of `Box<dyn Fn() + 'static, Global>` (hiding `+ 'static` as it is the default in this case). Showing `Global` here is a separate issue, #80379, which is on my agenda.

Note that I am not really fond of the fact that I had to add a parameter to such a widely used function (30+ call sites) to address such a niche bug.

CC `@GuillaumeGomez`
Requesting a review from a compiler contributor or team member as recommended on Zulip.
r? compiler

---

`@rustbot` label T-compiler T-rustdoc A-cross-crate-reexports

src/librustdoc/clean/auto_trait.rs

@@ -124,7 +124,7 @@ where
                 unsafety: hir::Unsafety::Normal,
                 generics: new_generics,
                 trait_: Some(clean_trait_ref_with_bindings(self.cx, trait_ref, ThinVec::new())),
-                for_: clean_middle_ty(ty::Binder::dummy(ty), self.cx, None),
+                for_: clean_middle_ty(ty::Binder::dummy(ty), self.cx, None, None),
                 items: Vec::new(),
                 polarity,
                 kind: ImplKind::Auto,

src/librustdoc/clean/blanket_impl.rs

@@ -107,7 +107,12 @@ impl<'a, 'tcx> BlanketImplFinder<'a, 'tcx> {
                             ty::Binder::dummy(trait_ref.subst_identity()),
                             ThinVec::new(),
                         )),
-                        for_: clean_middle_ty(ty::Binder::dummy(ty.subst_identity()), cx, None),
+                        for_: clean_middle_ty(
+                            ty::Binder::dummy(ty.subst_identity()),
+                            cx,
+                            None,
+                            None,
+                        ),
                         items: cx
                             .tcx
                             .associated_items(impl_def_id)
@@ -119,6 +124,7 @@ impl<'a, 'tcx> BlanketImplFinder<'a, 'tcx> {
                             ty::Binder::dummy(trait_ref.subst_identity().self_ty()),
                             cx,
                             None,
+                            None,
                         ))),
                     }))),
                     cfg: None,

src/librustdoc/clean/inline.rs

@@ -278,8 +278,12 @@ fn build_union(cx: &mut DocContext<'_>, did: DefId) -> clean::Union {
 
 fn build_type_alias(cx: &mut DocContext<'_>, did: DefId) -> Box<clean::Typedef> {
     let predicates = cx.tcx.explicit_predicates_of(did);
-    let type_ =
-        clean_middle_ty(ty::Binder::dummy(cx.tcx.type_of(did).subst_identity()), cx, Some(did));
+    let type_ = clean_middle_ty(
+        ty::Binder::dummy(cx.tcx.type_of(did).subst_identity()),
+        cx,
+        Some(did),
+        None,
+    );
 
     Box::new(clean::Typedef {
         type_,
@@ -386,9 +390,12 @@ pub(crate) fn build_impl(
 
     let for_ = match &impl_item {
         Some(impl_) => clean_ty(impl_.self_ty, cx),
-        None => {
-            clean_middle_ty(ty::Binder::dummy(tcx.type_of(did).subst_identity()), cx, Some(did))
-        }
+        None => clean_middle_ty(
+            ty::Binder::dummy(tcx.type_of(did).subst_identity()),
+            cx,
+            Some(did),
+            None,
+        ),
     };
 
     // Only inline impl if the implementing type is
@@ -630,6 +637,7 @@ fn build_const(cx: &mut DocContext<'_>, def_id: DefId) -> clean::Constant {
             ty::Binder::dummy(cx.tcx.type_of(def_id).subst_identity()),
             cx,
             Some(def_id),
+            None,
         ),
         kind: clean::ConstantKind::Extern { def_id },
     }
@@ -641,6 +649,7 @@ fn build_static(cx: &mut DocContext<'_>, did: DefId, mutable: bool) -> clean::St
             ty::Binder::dummy(cx.tcx.type_of(did).subst_identity()),
             cx,
             Some(did),
+            None,
         ),
         mutability: if mutable { Mutability::Mut } else { Mutability::Not },
         expr: None,