From a123aa96c3f01d0162bef3112fbb841bc1ea83e9 Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Sun, 14 Apr 2024 11:07:02 -0400
Subject: [PATCH 1/2] generics.is_empty, rather than checking params

---
 compiler/rustc_hir_analysis/src/check/wfcheck.rs   |  2 +-
 .../rustc_hir_analysis/src/hir_ty_lowering/mod.rs  |  2 +-
 compiler/rustc_hir_analysis/src/lib.rs             |  2 +-
 compiler/rustc_hir_typeck/src/method/confirm.rs    |  2 +-
 .../rustc_hir_typeck/src/method/prelude2021.rs     |  2 +-
 compiler/rustc_hir_typeck/src/method/probe.rs      |  2 +-
 compiler/rustc_hir_typeck/src/method/suggest.rs    | 14 +++-----------
 compiler/rustc_middle/src/ty/generics.rs           |  5 +++++
 compiler/rustc_middle/src/ty/print/mod.rs          |  2 +-
 .../src/traits/object_safety.rs                    |  2 +-
 .../rustc_trait_selection/src/traits/select/mod.rs |  2 +-
 .../clippy_lints/src/iter_without_into_iter.rs     |  2 +-
 .../clippy_utils/src/ty/type_certainty/mod.rs      |  2 +-
 src/tools/rustfmt/src/items.rs                     |  6 +++---
 14 files changed, 22 insertions(+), 25 deletions(-)

diff --git a/compiler/rustc_hir_analysis/src/check/wfcheck.rs b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
index c26f982fa473c..b128e160eaa97 100644
--- a/compiler/rustc_hir_analysis/src/check/wfcheck.rs
+++ b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
@@ -430,7 +430,7 @@ fn check_gat_where_clauses(tcx: TyCtxt<'_>, trait_def_id: LocalDefId) {
             }
             let gat_generics = tcx.generics_of(gat_def_id);
             // FIXME(jackh726): we can also warn in the more general case
-            if gat_generics.params.is_empty() {
+            if gat_generics.is_empty() {
                 continue;
             }
 
diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
index 63aeb165a4808..3d6ed8e2047d1 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs
@@ -411,7 +411,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         // Traits always have `Self` as a generic parameter, which means they will not return early
         // here and so associated type bindings will be handled regardless of whether there are any
         // non-`Self` generic parameters.
-        if generics.params.is_empty() {
+        if generics.is_empty() {
             return (tcx.mk_args(parent_args), arg_count);
         }
 
diff --git a/compiler/rustc_hir_analysis/src/lib.rs b/compiler/rustc_hir_analysis/src/lib.rs
index c374f9762d69b..52da17d5a306c 100644
--- a/compiler/rustc_hir_analysis/src/lib.rs
+++ b/compiler/rustc_hir_analysis/src/lib.rs
@@ -185,7 +185,7 @@ pub fn check_crate(tcx: TyCtxt<'_>) {
         let def_kind = tcx.def_kind(item_def_id);
         match def_kind {
             DefKind::Static { .. } => tcx.ensure().eval_static_initializer(item_def_id),
-            DefKind::Const if tcx.generics_of(item_def_id).params.is_empty() => {
+            DefKind::Const if tcx.generics_of(item_def_id).is_empty() => {
                 let instance = ty::Instance::new(item_def_id.into(), ty::GenericArgs::empty());
                 let cid = GlobalId { instance, promoted: None };
                 let param_env = ty::ParamEnv::reveal_all();
diff --git a/compiler/rustc_hir_typeck/src/method/confirm.rs b/compiler/rustc_hir_typeck/src/method/confirm.rs
index 36860e446fc2b..a1fc8d4f46eed 100644
--- a/compiler/rustc_hir_typeck/src/method/confirm.rs
+++ b/compiler/rustc_hir_typeck/src/method/confirm.rs
@@ -450,7 +450,7 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
         // `foo.bar::<u32>(...)` -- the `Self` type here will be the
         // type of `foo` (possibly adjusted), but we don't want to
         // include that. We want just the `[_, u32]` part.
-        if !args.is_empty() && !generics.params.is_empty() {
+        if !args.is_empty() && !generics.is_empty() {
             let user_type_annotation = self.probe(|_| {
                 let user_args = UserArgs {
                     args: GenericArgs::for_item(self.tcx, pick.item.def_id, |param, _| {
diff --git a/compiler/rustc_hir_typeck/src/method/prelude2021.rs b/compiler/rustc_hir_typeck/src/method/prelude2021.rs
index 0e43cb40485a5..cd7bbe29c3564 100644
--- a/compiler/rustc_hir_typeck/src/method/prelude2021.rs
+++ b/compiler/rustc_hir_typeck/src/method/prelude2021.rs
@@ -282,7 +282,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 if !self_ty_name.contains('<') {
                     if let Adt(def, _) = self_ty.kind() {
                         let generics = self.tcx.generics_of(def.did());
-                        if !generics.params.is_empty() {
+                        if !generics.is_empty() {
                             let counts = generics.own_counts();
                             self_ty_name += &format!(
                                 "<{}>",
diff --git a/compiler/rustc_hir_typeck/src/method/probe.rs b/compiler/rustc_hir_typeck/src/method/probe.rs
index 28e17e1de36c3..706565f790cb8 100644
--- a/compiler/rustc_hir_typeck/src/method/probe.rs
+++ b/compiler/rustc_hir_typeck/src/method/probe.rs
@@ -1871,7 +1871,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         let generics = self.tcx.generics_of(method);
         assert_eq!(args.len(), generics.parent_count);
 
-        let xform_fn_sig = if generics.params.is_empty() {
+        let xform_fn_sig = if generics.is_empty() {
             fn_sig.instantiate(self.tcx, args)
         } else {
             let args = GenericArgs::for_item(self.tcx, method, |param, _| {
diff --git a/compiler/rustc_hir_typeck/src/method/suggest.rs b/compiler/rustc_hir_typeck/src/method/suggest.rs
index 754866c85c4a0..0a6611dfec1ba 100644
--- a/compiler/rustc_hir_typeck/src/method/suggest.rs
+++ b/compiler/rustc_hir_typeck/src/method/suggest.rs
@@ -1881,10 +1881,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
                 self.tcx.value_path_str_with_args(def.did(), infer_args)
             } else {
-                self.ty_to_value_string(target_ty)
+                self.ty_to_string(target_ty)
             }
         } else {
-            self.ty_to_value_string(rcvr_ty.peel_refs())
+            self.ty_to_string(rcvr_ty.peel_refs())
         };
         if let SelfSource::MethodCall(_) = source {
             let first_arg = static_candidates.get(0).and_then(|candidate_source| {
@@ -2485,7 +2485,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     return;
                 };
 
-                let name = self.ty_to_value_string(actual);
+                let name = self.ty_to_string(actual);
                 let inner_id = kind.did();
                 let mutable = if let Some(AutorefOrPtrAdjustment::Autoref { mutbl, .. }) =
                     pick.autoref_or_ptr_adjustment
@@ -2829,14 +2829,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         }
     }
 
-    /// Print out the type for use in value namespace.
-    fn ty_to_value_string(&self, ty: Ty<'tcx>) -> String {
-        match ty.kind() {
-            ty::Adt(def, args) => self.tcx.def_path_str_with_args(def.did(), args),
-            _ => self.ty_to_string(ty),
-        }
-    }
-
     fn suggest_await_before_method(
         &self,
         err: &mut Diag<'_>,
diff --git a/compiler/rustc_middle/src/ty/generics.rs b/compiler/rustc_middle/src/ty/generics.rs
index e984f54370178..f8dd5717e04ae 100644
--- a/compiler/rustc_middle/src/ty/generics.rs
+++ b/compiler/rustc_middle/src/ty/generics.rs
@@ -145,6 +145,11 @@ pub struct Generics {
 }
 
 impl<'tcx> Generics {
+    /// Are there no generics (including parent generics)?
+    pub fn is_empty(&self) -> bool {
+        self.count() == 0
+    }
+
     /// Looks through the generics and all parents to find the index of the
     /// given param def-id. This is in comparison to the `param_def_id_to_index`
     /// struct member, which only stores information about this item's own
diff --git a/compiler/rustc_middle/src/ty/print/mod.rs b/compiler/rustc_middle/src/ty/print/mod.rs
index 9d0e1123e43ac..622fea4e4d58f 100644
--- a/compiler/rustc_middle/src/ty/print/mod.rs
+++ b/compiler/rustc_middle/src/ty/print/mod.rs
@@ -157,7 +157,7 @@ pub trait Printer<'tcx>: Sized {
                         // If we have any generic arguments to print, we do that
                         // on top of the same path, but without its own generics.
                         _ => {
-                            if !generics.params.is_empty() && args.len() >= generics.count() {
+                            if !generics.is_empty() && args.len() >= generics.count() {
                                 let args = generics.own_args_no_defaults(self.tcx(), args);
                                 return self.path_generic_args(
                                     |cx| cx.print_def_path(def_id, parent_args),
diff --git a/compiler/rustc_trait_selection/src/traits/object_safety.rs b/compiler/rustc_trait_selection/src/traits/object_safety.rs
index 5e1343b50ce7f..2434f68e1c140 100644
--- a/compiler/rustc_trait_selection/src/traits/object_safety.rs
+++ b/compiler/rustc_trait_selection/src/traits/object_safety.rs
@@ -397,7 +397,7 @@ pub fn object_safety_violations_for_assoc_item(
         // Associated types can only be object safe if they have `Self: Sized` bounds.
         ty::AssocKind::Type => {
             if !tcx.features().generic_associated_types_extended
-                && !tcx.generics_of(item.def_id).params.is_empty()
+                && !tcx.generics_of(item.def_id).is_empty()
                 && !item.is_impl_trait_in_trait()
             {
                 vec![ObjectSafetyViolation::GAT(item.name, item.ident(tcx).span)]
diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
index e363119393ad1..7fda5cbc9bb42 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -1773,7 +1773,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             // If this type is a GAT, and of the GAT args resolve to something new,
             // that means that we must have newly inferred something about the GAT.
             // We should give up in that case.
-            if !generics.params.is_empty()
+            if !generics.is_empty()
                 && obligation.predicate.args[generics.parent_count..]
                     .iter()
                     .any(|&p| p.has_non_region_infer() && self.infcx.shallow_resolve(p) != p)
diff --git a/src/tools/clippy/clippy_lints/src/iter_without_into_iter.rs b/src/tools/clippy/clippy_lints/src/iter_without_into_iter.rs
index c749a71233033..1d782254a5e74 100644
--- a/src/tools/clippy/clippy_lints/src/iter_without_into_iter.rs
+++ b/src/tools/clippy/clippy_lints/src/iter_without_into_iter.rs
@@ -225,7 +225,7 @@ impl {self_ty_without_ref} {{
             && let ImplItemKind::Fn(sig, _) = item.kind
             && let FnRetTy::Return(ret) = sig.decl.output
             && is_nameable_in_impl_trait(ret)
-            && cx.tcx.generics_of(item_did).params.is_empty()
+            && cx.tcx.generics_of(item_did).is_empty()
             && sig.decl.implicit_self == expected_implicit_self
             && sig.decl.inputs.len() == 1
             && let Some(imp) = get_parent_as_impl(cx.tcx, item.hir_id())
diff --git a/src/tools/clippy/clippy_utils/src/ty/type_certainty/mod.rs b/src/tools/clippy/clippy_utils/src/ty/type_certainty/mod.rs
index 762830ffd78d9..8dc049e4eef29 100644
--- a/src/tools/clippy/clippy_utils/src/ty/type_certainty/mod.rs
+++ b/src/tools/clippy/clippy_utils/src/ty/type_certainty/mod.rs
@@ -176,7 +176,7 @@ fn qpath_certainty(cx: &LateContext<'_>, qpath: &QPath<'_>, resolves_to_type: bo
             .get(*lang_item)
             .map_or(Certainty::Uncertain, |def_id| {
                 let generics = cx.tcx.generics_of(def_id);
-                if generics.parent_count == 0 && generics.params.is_empty() {
+                if generics.is_empty() {
                     Certainty::Certain(if resolves_to_type { Some(def_id) } else { None })
                 } else {
                     Certainty::Uncertain
diff --git a/src/tools/rustfmt/src/items.rs b/src/tools/rustfmt/src/items.rs
index f6f51fbd8eaf9..adb521b13d811 100644
--- a/src/tools/rustfmt/src/items.rs
+++ b/src/tools/rustfmt/src/items.rs
@@ -1725,7 +1725,7 @@ fn rewrite_ty<R: Rewrite>(
     result.push_str(&format!("{}type ", format_visibility(context, vis)));
     let ident_str = rewrite_ident(context, ident);
 
-    if generics.params.is_empty() {
+    if generics.is_empty() {
         result.push_str(ident_str)
     } else {
         // 2 = `= `
@@ -2834,7 +2834,7 @@ fn rewrite_generics(
     // FIXME: convert bounds to where-clauses where they get too big or if
     // there is a where-clause at all.
 
-    if generics.params.is_empty() {
+    if generics.is_empty() {
         return Some(ident.to_owned());
     }
 
@@ -3191,7 +3191,7 @@ fn format_generics(
 
     // If the generics are not parameterized then generics.span.hi() == 0,
     // so we use span.lo(), which is the position after `struct Foo`.
-    let span_end_before_where = if !generics.params.is_empty() {
+    let span_end_before_where = if !generics.is_empty() {
         generics.span.hi()
     } else {
         span.lo()

From 34a04e94e1293b3ee9f1629b862feabb22add257 Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Sun, 14 Apr 2024 11:08:32 -0400
Subject: [PATCH 2/2] And also .count() == 0 -> is_empty()

---
 compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs       | 2 +-
 compiler/rustc_hir_analysis/src/variance/constraints.rs         | 2 +-
 compiler/rustc_hir_analysis/src/variance/mod.rs                 | 2 +-
 compiler/rustc_monomorphize/src/collector.rs                    | 2 +-
 compiler/rustc_monomorphize/src/polymorphize.rs                 | 2 +-
 .../rustc_trait_selection/src/traits/select/confirmation.rs     | 2 +-
 6 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs b/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
index 822bf95305fc0..28b8fa0cd33ee 100644
--- a/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
+++ b/compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs
@@ -1312,7 +1312,7 @@ fn generics_args_err_extend<'a>(
             // it was done based on the end of assoc segment but that sometimes
             // led to impossible spans and caused issues like #116473
             let args_span = args.span_ext.with_lo(args.span_ext.lo() - BytePos(2));
-            if tcx.generics_of(adt_def.did()).count() == 0 {
+            if tcx.generics_of(adt_def.did()).is_empty() {
                 // FIXME(estebank): we could also verify that the arguments being
                 // work for the `enum`, instead of just looking if it takes *any*.
                 err.span_suggestion_verbose(
diff --git a/compiler/rustc_hir_analysis/src/variance/constraints.rs b/compiler/rustc_hir_analysis/src/variance/constraints.rs
index 20e4110e1378d..22ff976d7774b 100644
--- a/compiler/rustc_hir_analysis/src/variance/constraints.rs
+++ b/compiler/rustc_hir_analysis/src/variance/constraints.rs
@@ -98,7 +98,7 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
         debug!("build_constraints_for_item({})", tcx.def_path_str(def_id));
 
         // Skip items with no generics - there's nothing to infer in them.
-        if tcx.generics_of(def_id).count() == 0 {
+        if tcx.generics_of(def_id).is_empty() {
             return;
         }
 
diff --git a/compiler/rustc_hir_analysis/src/variance/mod.rs b/compiler/rustc_hir_analysis/src/variance/mod.rs
index 42885b0c83282..03fe55f0c4a23 100644
--- a/compiler/rustc_hir_analysis/src/variance/mod.rs
+++ b/compiler/rustc_hir_analysis/src/variance/mod.rs
@@ -40,7 +40,7 @@ fn crate_variances(tcx: TyCtxt<'_>, (): ()) -> CrateVariancesMap<'_> {
 
 fn variances_of(tcx: TyCtxt<'_>, item_def_id: LocalDefId) -> &[ty::Variance] {
     // Skip items with no generics - there's nothing to infer in them.
-    if tcx.generics_of(item_def_id).count() == 0 {
+    if tcx.generics_of(item_def_id).is_empty() {
         return &[];
     }
 
diff --git a/compiler/rustc_monomorphize/src/collector.rs b/compiler/rustc_monomorphize/src/collector.rs
index ee6c154e6e84e..79d7e6a5bbbfb 100644
--- a/compiler/rustc_monomorphize/src/collector.rs
+++ b/compiler/rustc_monomorphize/src/collector.rs
@@ -1561,7 +1561,7 @@ impl<'v> RootCollector<'_, 'v> {
         match self.tcx.def_kind(id.owner_id) {
             DefKind::Enum | DefKind::Struct | DefKind::Union => {
                 if self.strategy == MonoItemCollectionStrategy::Eager
-                    && self.tcx.generics_of(id.owner_id).count() == 0
+                    && self.tcx.generics_of(id.owner_id).is_empty()
                 {
                     debug!("RootCollector: ADT drop-glue for `{id:?}`",);
 
diff --git a/compiler/rustc_monomorphize/src/polymorphize.rs b/compiler/rustc_monomorphize/src/polymorphize.rs
index 6d237df073f81..1a9329b3899ca 100644
--- a/compiler/rustc_monomorphize/src/polymorphize.rs
+++ b/compiler/rustc_monomorphize/src/polymorphize.rs
@@ -51,7 +51,7 @@ fn unused_generic_params<'tcx>(
     debug!(?generics);
 
     // Exit early when there are no parameters to be unused.
-    if generics.count() == 0 {
+    if generics.is_empty() {
         return UnusedGenericParams::new_all_used();
     }
 
diff --git a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
index 25ba985397e6c..76b29c9e11bac 100644
--- a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
@@ -619,7 +619,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             // higher-ranked things.
             // Prevent, e.g., `dyn Iterator<Item = str>`.
             for bound in self.tcx().item_bounds(assoc_type).transpose_iter() {
-                let arg_bound = if defs.count() == 0 {
+                let arg_bound = if defs.is_empty() {
                     bound.instantiate(tcx, trait_predicate.trait_ref.args)
                 } else {
                     let mut args = smallvec::SmallVec::with_capacity(defs.count());