Rollup merge of #142275 - aDotInTheVoid:gen-ty-of, r=fmease

rustdoc: Refractor `clean_ty_generics`

Refactoring towards #142226

[Zulip Discussion](https://rust-lang.zulipchat.com/#narrow/channel/266220-t-rustdoc/topic/Why.20sometimes.20.60predicates_of.60.20.28vs.20.60explicit_predicates_.2E.2E.2E/near/523182529)

The old `clean_ty_generics` was almost always called with the same args, so rename it to `clean_ty_generics_inner`, and add a new wrapper that generates those args from a `DefId`. Having this be the main entrypoint to `clean_ty_generics` should make it easier to start calling `inferred_outlives_of` #142264 (comment) (and is more readable even if we don't)

Also, replaces all calls in rustdoc to `tcx.predicates_of` to `tcx.explicit_predicates_of`, which lets us remove `filter_non_trait_generics`

r? ```@fmease```

Author: fmease

src/librustdoc/clean/auto_trait.rs

@@ -11,7 +11,7 @@ use tracing::{debug, instrument};
 
 use crate::clean::{
     self, Lifetime, clean_generic_param_def, clean_middle_ty, clean_predicate,
-    clean_trait_ref_with_constraints, clean_ty_generics, simplify,
+    clean_trait_ref_with_constraints, clean_ty_generics_inner, simplify,
 };
 use crate::core::DocContext;
 
@@ -101,7 +101,7 @@ fn synthesize_auto_trait_impl<'tcx>(
             // Instead, we generate `impl !Send for Foo<T>`, which better
             // expresses the fact that `Foo<T>` never implements `Send`,
             // regardless of the choice of `T`.
-            let mut generics = clean_ty_generics(
+            let mut generics = clean_ty_generics_inner(
                 cx,
                 tcx.generics_of(item_def_id),
                 ty::GenericPredicates::default(),

src/librustdoc/clean/blanket_impl.rs

@@ -90,11 +90,7 @@ pub(crate) fn synthesize_blanket_impls(
                     stability: None,
                     kind: clean::ImplItem(Box::new(clean::Impl {
                         safety: hir::Safety::Safe,
-                        generics: clean_ty_generics(
-                            cx,
-                            tcx.generics_of(impl_def_id),
-                            tcx.explicit_predicates_of(impl_def_id),
-                        ),
+                        generics: clean_ty_generics(cx, impl_def_id),
                         // FIXME(eddyb) compute both `trait_` and `for_` from
                         // the post-inference `trait_ref`, as it's more accurate.
                         trait_: Some(clean_trait_ref_with_constraints(

src/librustdoc/clean/inline.rs

@@ -264,25 +264,21 @@ pub(crate) fn build_trait(cx: &mut DocContext<'_>, did: DefId) -> clean::Trait {
         .map(|item| clean_middle_assoc_item(item, cx))
         .collect();
 
-    let predicates = cx.tcx.predicates_of(did);
-    let generics = clean_ty_generics(cx, cx.tcx.generics_of(did), predicates);
-    let generics = filter_non_trait_generics(did, generics);
+    let generics = clean_ty_generics(cx, did);
     let (generics, supertrait_bounds) = separate_self_bounds(generics);
     clean::Trait { def_id: did, generics, items: trait_items, bounds: supertrait_bounds }
 }
 
 fn build_trait_alias(cx: &mut DocContext<'_>, did: DefId) -> clean::TraitAlias {
-    let predicates = cx.tcx.predicates_of(did);
-    let generics = clean_ty_generics(cx, cx.tcx.generics_of(did), predicates);
+    let generics = clean_ty_generics(cx, did);
     let (generics, bounds) = separate_self_bounds(generics);
     clean::TraitAlias { generics, bounds }
 }
 
 pub(super) fn build_function(cx: &mut DocContext<'_>, def_id: DefId) -> Box<clean::Function> {
     let sig = cx.tcx.fn_sig(def_id).instantiate_identity();
     // The generics need to be cleaned before the signature.
-    let mut generics =
-        clean_ty_generics(cx, cx.tcx.generics_of(def_id), cx.tcx.explicit_predicates_of(def_id));
+    let mut generics = clean_ty_generics(cx, def_id);
     let bound_vars = clean_bound_vars(sig.bound_vars());
 
     // At the time of writing early & late-bound params are stored separately in rustc,
@@ -311,30 +307,26 @@ pub(super) fn build_function(cx: &mut DocContext<'_>, def_id: DefId) -> Box<clea
 }
 
 fn build_enum(cx: &mut DocContext<'_>, did: DefId) -> clean::Enum {
-    let predicates = cx.tcx.explicit_predicates_of(did);
-
     clean::Enum {
-        generics: clean_ty_generics(cx, cx.tcx.generics_of(did), predicates),
+        generics: clean_ty_generics(cx, did),
         variants: cx.tcx.adt_def(did).variants().iter().map(|v| clean_variant_def(v, cx)).collect(),
     }
 }
 
 fn build_struct(cx: &mut DocContext<'_>, did: DefId) -> clean::Struct {
-    let predicates = cx.tcx.explicit_predicates_of(did);
     let variant = cx.tcx.adt_def(did).non_enum_variant();
 
     clean::Struct {
         ctor_kind: variant.ctor_kind(),
-        generics: clean_ty_generics(cx, cx.tcx.generics_of(did), predicates),
+        generics: clean_ty_generics(cx, did),
         fields: variant.fields.iter().map(|x| clean_middle_field(x, cx)).collect(),
     }
 }
 
 fn build_union(cx: &mut DocContext<'_>, did: DefId) -> clean::Union {
-    let predicates = cx.tcx.explicit_predicates_of(did);
     let variant = cx.tcx.adt_def(did).non_enum_variant();
 
-    let generics = clean_ty_generics(cx, cx.tcx.generics_of(did), predicates);
+    let generics = clean_ty_generics(cx, did);
     let fields = variant.fields.iter().map(|x| clean_middle_field(x, cx)).collect();
     clean::Union { generics, fields }
 }
@@ -344,14 +336,13 @@ fn build_type_alias(
     did: DefId,
     ret: &mut Vec<Item>,
 ) -> Box<clean::TypeAlias> {
-    let predicates = cx.tcx.explicit_predicates_of(did);
     let ty = cx.tcx.type_of(did).instantiate_identity();
     let type_ = clean_middle_ty(ty::Binder::dummy(ty), cx, Some(did), None);
     let inner_type = clean_ty_alias_inner_type(ty, cx, ret);
 
     Box::new(clean::TypeAlias {
         type_,
-        generics: clean_ty_generics(cx, cx.tcx.generics_of(did), predicates),
+        generics: clean_ty_generics(cx, did),
         inner_type,
         item_type: None,
     })
@@ -483,7 +474,6 @@ pub(crate) fn build_impl(
     }
 
     let document_hidden = cx.render_options.document_hidden;
-    let predicates = tcx.explicit_predicates_of(did);
     let (trait_items, generics) = match impl_item {
         Some(impl_) => (
             impl_
@@ -549,9 +539,7 @@ pub(crate) fn build_impl(
                 })
                 .map(|item| clean_middle_assoc_item(item, cx))
                 .collect::<Vec<_>>(),
-            clean::enter_impl_trait(cx, |cx| {
-                clean_ty_generics(cx, tcx.generics_of(did), predicates)
-            }),
+            clean::enter_impl_trait(cx, |cx| clean_ty_generics(cx, did)),
         ),
     };
     let polarity = tcx.impl_polarity(did);
@@ -713,8 +701,7 @@ pub(crate) fn print_inlined_const(tcx: TyCtxt<'_>, did: DefId) -> String {
 }
 
 fn build_const_item(cx: &mut DocContext<'_>, def_id: DefId) -> clean::Constant {
-    let mut generics =
-        clean_ty_generics(cx, cx.tcx.generics_of(def_id), cx.tcx.explicit_predicates_of(def_id));
+    let mut generics = clean_ty_generics(cx, def_id);
     clean::simplify::move_bounds_to_generic_parameters(&mut generics);
     let ty = clean_middle_ty(
         ty::Binder::dummy(cx.tcx.type_of(def_id).instantiate_identity()),
@@ -761,44 +748,6 @@ fn build_macro(
     }
 }
 
-/// A trait's generics clause actually contains all of the predicates for all of
-/// its associated types as well. We specifically move these clauses to the
-/// associated types instead when displaying, so when we're generating the
-/// generics for the trait itself we need to be sure to remove them.
-/// We also need to remove the implied "recursive" Self: Trait bound.
-///
-/// The inverse of this filtering logic can be found in the `Clean`
-/// implementation for `AssociatedType`
-fn filter_non_trait_generics(trait_did: DefId, mut g: clean::Generics) -> clean::Generics {
-    for pred in &mut g.where_predicates {
-        if let clean::WherePredicate::BoundPredicate { ty: clean::SelfTy, ref mut bounds, .. } =
-            *pred
-        {
-            bounds.retain(|bound| match bound {
-                clean::GenericBound::TraitBound(clean::PolyTrait { trait_, .. }, _) => {
-                    trait_.def_id() != trait_did
-                }
-                _ => true,
-            });
-        }
-    }
-
-    g.where_predicates.retain(|pred| match pred {
-        clean::WherePredicate::BoundPredicate {
-            ty:
-                clean::QPath(box clean::QPathData {
-                    self_type: clean::Generic(_),
-                    trait_: Some(trait_),
-                    ..
-                }),
-            bounds,
-            ..
-        } => !bounds.is_empty() && trait_.def_id() != trait_did,
-        _ => true,
-    });
-    g
-}
-
 fn separate_self_bounds(mut g: clean::Generics) -> (clean::Generics, Vec<clean::GenericBound>) {
     let mut ty_bounds = Vec::new();
     g.where_predicates.retain(|pred| match *pred {

src/librustdoc/clean/mod.rs

@@ -793,7 +793,11 @@ pub(crate) fn clean_generics<'tcx>(
     }
 }
 
-fn clean_ty_generics<'tcx>(
+fn clean_ty_generics<'tcx>(cx: &mut DocContext<'tcx>, def_id: DefId) -> Generics {
+    clean_ty_generics_inner(cx, cx.tcx.generics_of(def_id), cx.tcx.explicit_predicates_of(def_id))
+}
+
+fn clean_ty_generics_inner<'tcx>(
     cx: &mut DocContext<'tcx>,
     gens: &ty::Generics,
     preds: ty::GenericPredicates<'tcx>,
@@ -1297,11 +1301,7 @@ pub(crate) fn clean_middle_assoc_item(assoc_item: &ty::AssocItem, cx: &mut DocCo
                 None,
             );
 
-            let mut generics = clean_ty_generics(
-                cx,
-                tcx.generics_of(assoc_item.def_id),
-                tcx.explicit_predicates_of(assoc_item.def_id),
-            );
+            let mut generics = clean_ty_generics(cx, assoc_item.def_id);
             simplify::move_bounds_to_generic_parameters(&mut generics);
 
             match assoc_item.container {
@@ -1389,7 +1389,7 @@ pub(crate) fn clean_middle_assoc_item(assoc_item: &ty::AssocItem, cx: &mut DocCo
                 let bounds = tcx.explicit_item_bounds(assoc_item.def_id).iter_identity_copied();
                 predicates = tcx.arena.alloc_from_iter(bounds.chain(predicates.iter().copied()));
             }
-            let mut generics = clean_ty_generics(
+            let mut generics = clean_ty_generics_inner(
                 cx,
                 tcx.generics_of(assoc_item.def_id),
                 ty::GenericPredicates { parent: None, predicates },