Rollup merge of #112772 - compiler-errors:clauses-1, r=lcnr

Add a fully fledged `Clause` type, rename old `Clause` to `ClauseKind`

Does two basic things before I put up a more delicate set of PRs (along the lines of #112714, but hopefully much cleaner) that migrate existing usages of `ty::Predicate` to `ty::Clause` (`predicates_of`/`item_bounds`/`ParamEnv::caller_bounds`).

1. Rename `Clause` to `ClauseKind`, so it's parallel with `PredicateKind`.
2. Add a new `Clause` type which is parallel to `Predicate`.
    * This type exposes `Clause::kind(self) -> Binder<'tcx, ClauseKind<'tcx>>` which is parallel to `Predicate::kind` 😸

The new `Clause` type essentially acts as a newtype wrapper around `Predicate` that asserts that it is specifically a `PredicateKind::Clause`. Turns out from experimentation[^1] that this is not negative performance-wise, which is wonderful, since this a much simpler design than something that requires encoding the discriminant into the alignment bits of a predicate kind, or something else like that...

r? ``@lcnr`` or ``@oli-obk``

[^1]: rust-lang/rust#112714 (comment)

clippy_lints/src/dereference.rs

@@ -26,7 +26,7 @@ use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::mir::{Rvalue, StatementKind};
 use rustc_middle::ty::adjustment::{Adjust, Adjustment, AutoBorrow, AutoBorrowMutability};
 use rustc_middle::ty::{
-    self, Binder, BoundVariableKind, Clause, EarlyBinder, FnSig, GenericArgKind, List, ParamEnv, ParamTy,
+    self, Binder, BoundVariableKind, ClauseKind, EarlyBinder, FnSig, GenericArgKind, List, ParamEnv, ParamTy,
     PredicateKind, ProjectionPredicate, Ty, TyCtxt, TypeVisitableExt, TypeckResults,
 };
 use rustc_session::{declare_tool_lint, impl_lint_pass};
@@ -1133,7 +1133,7 @@ fn needless_borrow_impl_arg_position<'tcx>(
     let projection_predicates = predicates
         .iter()
         .filter_map(|predicate| {
-            if let PredicateKind::Clause(Clause::Projection(projection_predicate)) = predicate.kind().skip_binder() {
+            if let PredicateKind::Clause(ClauseKind::Projection(projection_predicate)) = predicate.kind().skip_binder() {
                 Some(projection_predicate)
             } else {
                 None
@@ -1147,7 +1147,7 @@ fn needless_borrow_impl_arg_position<'tcx>(
     if predicates
         .iter()
         .filter_map(|predicate| {
-            if let PredicateKind::Clause(Clause::Trait(trait_predicate)) = predicate.kind().skip_binder()
+            if let PredicateKind::Clause(ClauseKind::Trait(trait_predicate)) = predicate.kind().skip_binder()
                 && trait_predicate.trait_ref.self_ty() == param_ty.to_ty(cx.tcx)
             {
                 Some(trait_predicate.trait_ref.def_id)
@@ -1209,7 +1209,7 @@ fn needless_borrow_impl_arg_position<'tcx>(
         }
 
         predicates.iter().all(|predicate| {
-            if let PredicateKind::Clause(Clause::Trait(trait_predicate)) = predicate.kind().skip_binder()
+            if let PredicateKind::Clause(ClauseKind::Trait(trait_predicate)) = predicate.kind().skip_binder()
                 && cx.tcx.is_diagnostic_item(sym::IntoIterator, trait_predicate.trait_ref.def_id)
                 && let ty::Param(param_ty) = trait_predicate.self_ty().kind()
                 && let GenericArgKind::Type(ty) = substs_with_referent_ty[param_ty.index as usize].unpack()

clippy_lints/src/derive.rs

@@ -14,7 +14,7 @@ use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::hir::nested_filter;
 use rustc_middle::traits::Reveal;
 use rustc_middle::ty::{
-    self, Binder, BoundConstness, Clause, GenericArgKind, GenericParamDefKind, ImplPolarity, ParamEnv, PredicateKind,
+    self, Binder, BoundConstness, ClauseKind, GenericArgKind, GenericParamDefKind, ImplPolarity, ParamEnv, PredicateKind,
     TraitPredicate, Ty, TyCtxt,
 };
 use rustc_session::{declare_lint_pass, declare_tool_lint};
@@ -503,7 +503,7 @@ fn param_env_for_derived_eq(tcx: TyCtxt<'_>, did: DefId, eq_trait_id: DefId) ->
 
     let ty_predicates = tcx.predicates_of(did).predicates;
     for (p, _) in ty_predicates {
-        if let PredicateKind::Clause(Clause::Trait(p)) = p.kind().skip_binder()
+        if let PredicateKind::Clause(ClauseKind::Trait(p)) = p.kind().skip_binder()
             && p.trait_ref.def_id == eq_trait_id
             && let ty::Param(self_ty) = p.trait_ref.self_ty().kind()
             && p.constness == BoundConstness::NotConst
@@ -516,7 +516,7 @@ fn param_env_for_derived_eq(tcx: TyCtxt<'_>, did: DefId, eq_trait_id: DefId) ->
     ParamEnv::new(
         tcx.mk_predicates_from_iter(ty_predicates.iter().map(|&(p, _)| p).chain(
             params.iter().filter(|&&(_, needs_eq)| needs_eq).map(|&(param, _)| {
-                tcx.mk_predicate(Binder::dummy(PredicateKind::Clause(Clause::Trait(TraitPredicate {
+                tcx.mk_predicate(Binder::dummy(PredicateKind::Clause(ClauseKind::Trait(TraitPredicate {
                     trait_ref: ty::TraitRef::new(tcx, eq_trait_id, [tcx.mk_param_from_def(param)]),
                     constness: BoundConstness::NotConst,
                     polarity: ImplPolarity::Positive,

clippy_lints/src/future_not_send.rs

@@ -4,7 +4,7 @@ use rustc_hir::intravisit::FnKind;
 use rustc_hir::{Body, FnDecl};
 use rustc_infer::infer::TyCtxtInferExt;
 use rustc_lint::{LateContext, LateLintPass};
-use rustc_middle::ty::{self, AliasTy, Clause, PredicateKind};
+use rustc_middle::ty::{self, AliasTy, ClauseKind, PredicateKind};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 use rustc_span::def_id::LocalDefId;
 use rustc_span::{sym, Span};
@@ -93,7 +93,7 @@ impl<'tcx> LateLintPass<'tcx> for FutureNotSend {
                                 infcx
                                     .err_ctxt()
                                     .maybe_note_obligation_cause_for_async_await(db, &obligation);
-                                if let PredicateKind::Clause(Clause::Trait(trait_pred)) =
+                                if let PredicateKind::Clause(ClauseKind::Trait(trait_pred)) =
                                     obligation.predicate.kind().skip_binder()
                                 {
                                     db.note(format!(

clippy_lints/src/methods/needless_collect.rs

@@ -16,7 +16,7 @@ use rustc_hir::{
 };
 use rustc_lint::LateContext;
 use rustc_middle::hir::nested_filter;
-use rustc_middle::ty::{self, AssocKind, Clause, EarlyBinder, GenericArg, GenericArgKind, PredicateKind, Ty};
+use rustc_middle::ty::{self, AssocKind, ClauseKind, EarlyBinder, GenericArg, GenericArgKind, PredicateKind, Ty};
 use rustc_span::symbol::Ident;
 use rustc_span::{sym, Span, Symbol};
 
@@ -175,7 +175,7 @@ fn check_collect_into_intoiterator<'tcx>(
                 .caller_bounds()
                 .into_iter()
                 .filter_map(|p| {
-                    if let PredicateKind::Clause(Clause::Trait(t)) = p.kind().skip_binder()
+                    if let PredicateKind::Clause(ClauseKind::Trait(t)) = p.kind().skip_binder()
                             && cx.tcx.is_diagnostic_item(sym::IntoIterator,t.trait_ref.def_id) {
                                 Some(t.self_ty())
                             } else {

clippy_lints/src/methods/unnecessary_to_owned.rs

@@ -14,7 +14,7 @@ use rustc_lint::LateContext;
 use rustc_middle::mir::Mutability;
 use rustc_middle::ty::adjustment::{Adjust, Adjustment, OverloadedDeref};
 use rustc_middle::ty::subst::{GenericArg, GenericArgKind, SubstsRef};
-use rustc_middle::ty::{self, Clause, EarlyBinder, ParamTy, PredicateKind, ProjectionPredicate, TraitPredicate, Ty};
+use rustc_middle::ty::{self, ClauseKind, EarlyBinder, ParamTy, PredicateKind, ProjectionPredicate, TraitPredicate, Ty};
 use rustc_span::{sym, Symbol};
 use rustc_trait_selection::traits::{query::evaluate_obligation::InferCtxtExt as _, Obligation, ObligationCause};
 
@@ -345,12 +345,12 @@ fn get_input_traits_and_projections<'tcx>(
     let mut projection_predicates = Vec::new();
     for predicate in cx.tcx.param_env(callee_def_id).caller_bounds() {
         match predicate.kind().skip_binder() {
-            PredicateKind::Clause(Clause::Trait(trait_predicate)) => {
+            PredicateKind::Clause(ClauseKind::Trait(trait_predicate)) => {
                 if trait_predicate.trait_ref.self_ty() == input {
                     trait_predicates.push(trait_predicate);
                 }
             },
-            PredicateKind::Clause(Clause::Projection(projection_predicate)) => {
+            PredicateKind::Clause(ClauseKind::Projection(projection_predicate)) => {
                 if projection_predicate.projection_ty.self_ty() == input {
                     projection_predicates.push(projection_predicate);
                 }
@@ -407,7 +407,7 @@ fn can_change_type<'a>(cx: &LateContext<'a>, mut expr: &'a Expr<'a>, mut ty: Ty<
 
                         let mut trait_predicates = cx.tcx.param_env(callee_def_id)
                             .caller_bounds().iter().filter(|predicate| {
-                            if let PredicateKind::Clause(Clause::Trait(trait_predicate))
+                            if let PredicateKind::Clause(ClauseKind::Trait(trait_predicate))
                                     = predicate.kind().skip_binder()
                                 && trait_predicate.trait_ref.self_ty() == *param_ty
                             {

clippy_lints/src/needless_pass_by_value.rs

@@ -126,7 +126,7 @@ impl<'tcx> LateLintPass<'tcx> for NeedlessPassByValue {
             .filter_map(|pred| {
                 // Note that we do not want to deal with qualified predicates here.
                 match pred.kind().no_bound_vars() {
-                    Some(ty::PredicateKind::Clause(ty::Clause::Trait(pred))) if pred.def_id() != sized_trait => {
+                    Some(ty::PredicateKind::Clause(ty::ClauseKind::Trait(pred))) if pred.def_id() != sized_trait => {
                         Some(pred)
                     },
                     _ => None,

clippy_lints/src/ptr.rs

@@ -19,7 +19,7 @@ use rustc_infer::infer::TyCtxtInferExt;
 use rustc_infer::traits::{Obligation, ObligationCause};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::hir::nested_filter;
-use rustc_middle::ty::{self, Binder, Clause, ExistentialPredicate, List, PredicateKind, Ty};
+use rustc_middle::ty::{self, Binder, ClauseKind, ExistentialPredicate, List, PredicateKind, Ty};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 use rustc_span::source_map::Span;
 use rustc_span::sym;
@@ -697,7 +697,7 @@ fn matches_preds<'tcx>(
             ObligationCause::dummy(),
             cx.param_env,
             cx.tcx
-                .mk_predicate(Binder::dummy(PredicateKind::Clause(Clause::Projection(
+                .mk_predicate(Binder::dummy(PredicateKind::Clause(ClauseKind::Projection(
                     p.with_self_ty(cx.tcx, ty),
                 )))),
         )),

clippy_lints/src/unit_return_expecting_ord.rs

@@ -4,7 +4,7 @@ use rustc_hir::def_id::DefId;
 use rustc_hir::{Closure, Expr, ExprKind, StmtKind};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::ty;
-use rustc_middle::ty::{Clause, GenericPredicates, PredicateKind, ProjectionPredicate, TraitPredicate};
+use rustc_middle::ty::{ClauseKind, GenericPredicates, PredicateKind, ProjectionPredicate, TraitPredicate};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 use rustc_span::{sym, BytePos, Span};
 
@@ -45,7 +45,7 @@ fn get_trait_predicates_for_trait_id<'tcx>(
     let mut preds = Vec::new();
     for (pred, _) in generics.predicates {
         if_chain! {
-            if let PredicateKind::Clause(Clause::Trait(poly_trait_pred)) = pred.kind().skip_binder();
+            if let PredicateKind::Clause(ClauseKind::Trait(poly_trait_pred)) = pred.kind().skip_binder();
             let trait_pred = cx.tcx.erase_late_bound_regions(pred.kind().rebind(poly_trait_pred));
             if let Some(trait_def_id) = trait_id;
             if trait_def_id == trait_pred.trait_ref.def_id;
@@ -63,7 +63,7 @@ fn get_projection_pred<'tcx>(
     trait_pred: TraitPredicate<'tcx>,
 ) -> Option<ProjectionPredicate<'tcx>> {
     generics.predicates.iter().find_map(|(proj_pred, _)| {
-        if let ty::PredicateKind::Clause(Clause::Projection(pred)) = proj_pred.kind().skip_binder() {
+        if let ty::PredicateKind::Clause(ClauseKind::Projection(pred)) = proj_pred.kind().skip_binder() {
             let projection_pred = cx.tcx.erase_late_bound_regions(proj_pred.kind().rebind(pred));
             if projection_pred.projection_ty.substs == trait_pred.trait_ref.substs {
                 return Some(projection_pred);

clippy_utils/src/eager_or_lazy.rs

@@ -73,7 +73,7 @@ fn fn_eagerness(cx: &LateContext<'_>, fn_id: DefId, name: Symbol, have_one_arg:
             .flat_map(|v| v.fields.iter())
             .any(|x| matches!(cx.tcx.type_of(x.did).subst_identity().peel_refs().kind(), ty::Param(_)))
             && all_predicates_of(cx.tcx, fn_id).all(|(pred, _)| match pred.kind().skip_binder() {
-                PredicateKind::Clause(ty::Clause::Trait(pred)) => cx.tcx.trait_def(pred.trait_ref.def_id).is_marker,
+                PredicateKind::Clause(ty::ClauseKind::Trait(pred)) => cx.tcx.trait_def(pred.trait_ref.def_id).is_marker,
                 _ => true,
             })
             && subs.types().all(|x| matches!(x.peel_refs().kind(), ty::Param(_)))

clippy_utils/src/qualify_min_const_fn.rs

@@ -27,14 +27,14 @@ pub fn is_min_const_fn<'tcx>(tcx: TyCtxt<'tcx>, body: &Body<'tcx>, msrv: &Msrv)
         for (predicate, _) in predicates.predicates {
             match predicate.kind().skip_binder() {
                 ty::PredicateKind::Clause(
-                    ty::Clause::RegionOutlives(_)
-                    | ty::Clause::TypeOutlives(_)
-                    | ty::Clause::Projection(_)
-                    | ty::Clause::Trait(..)
-                    | ty::Clause::ConstArgHasType(..),
+                    ty::ClauseKind::RegionOutlives(_)
+                    | ty::ClauseKind::TypeOutlives(_)
+                    | ty::ClauseKind::Projection(_)
+                    | ty::ClauseKind::Trait(..)
+                    | ty::ClauseKind::ConstArgHasType(..),
                 )
-                | ty::PredicateKind::Clause(ty::Clause::WellFormed(_))
-                | ty::PredicateKind::Clause(ty::Clause::ConstEvaluatable(..))
+                | ty::PredicateKind::Clause(ty::ClauseKind::WellFormed(_))
+                | ty::PredicateKind::Clause(ty::ClauseKind::ConstEvaluatable(..))
                 | ty::PredicateKind::ConstEquate(..)
                 | ty::PredicateKind::TypeWellFormedFromEnv(..) => continue,
                 ty::PredicateKind::AliasRelate(..) => panic!("alias relate predicate on function: {predicate:#?}"),

clippy_utils/src/ty.rs

@@ -94,7 +94,7 @@ pub fn contains_ty_adt_constructor_opaque<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'
                         match predicate.kind().skip_binder() {
                             // For `impl Trait<U>`, it will register a predicate of `T: Trait<U>`, so we go through
                             // and check substitutions to find `U`.
-                            ty::PredicateKind::Clause(ty::Clause::Trait(trait_predicate)) => {
+                            ty::PredicateKind::Clause(ty::ClauseKind::Trait(trait_predicate)) => {
                                 if trait_predicate
                                     .trait_ref
                                     .substs
@@ -107,7 +107,7 @@ pub fn contains_ty_adt_constructor_opaque<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'
                             },
                             // For `impl Trait<Assoc=U>`, it will register a predicate of `<T as Trait>::Assoc = U`,
                             // so we check the term for `U`.
-                            ty::PredicateKind::Clause(ty::Clause::Projection(projection_predicate)) => {
+                            ty::PredicateKind::Clause(ty::ClauseKind::Projection(projection_predicate)) => {
                                 if let ty::TermKind::Ty(ty) = projection_predicate.term.unpack() {
                                     if contains_ty_adt_constructor_opaque_inner(cx, ty, needle, seen) {
                                         return true;
@@ -268,7 +268,7 @@ pub fn is_must_use_ty<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
         ty::Tuple(substs) => substs.iter().any(|ty| is_must_use_ty(cx, ty)),
         ty::Alias(ty::Opaque, ty::AliasTy { def_id, .. }) => {
             for (predicate, _) in cx.tcx.explicit_item_bounds(def_id).skip_binder() {
-                if let ty::PredicateKind::Clause(ty::Clause::Trait(trait_predicate)) = predicate.kind().skip_binder() {
+                if let ty::PredicateKind::Clause(ty::ClauseKind::Trait(trait_predicate)) = predicate.kind().skip_binder() {
                     if cx.tcx.has_attr(trait_predicate.trait_ref.def_id, sym::must_use) {
                         return true;
                     }
@@ -707,7 +707,7 @@ fn sig_from_bounds<'tcx>(
 
     for pred in predicates {
         match pred.kind().skip_binder() {
-            PredicateKind::Clause(ty::Clause::Trait(p))
+            PredicateKind::Clause(ty::ClauseKind::Trait(p))
                 if (lang_items.fn_trait() == Some(p.def_id())
                     || lang_items.fn_mut_trait() == Some(p.def_id())
                     || lang_items.fn_once_trait() == Some(p.def_id()))
@@ -720,7 +720,7 @@ fn sig_from_bounds<'tcx>(
                 }
                 inputs = Some(i);
             },
-            PredicateKind::Clause(ty::Clause::Projection(p))
+            PredicateKind::Clause(ty::ClauseKind::Projection(p))
                 if Some(p.projection_ty.def_id) == lang_items.fn_once_output() && p.projection_ty.self_ty() == ty =>
             {
                 if output.is_some() {
@@ -747,7 +747,7 @@ fn sig_for_projection<'tcx>(cx: &LateContext<'tcx>, ty: AliasTy<'tcx>) -> Option
         .subst_iter_copied(cx.tcx, ty.substs)
     {
         match pred.kind().skip_binder() {
-            PredicateKind::Clause(ty::Clause::Trait(p))
+            PredicateKind::Clause(ty::ClauseKind::Trait(p))
                 if (lang_items.fn_trait() == Some(p.def_id())
                     || lang_items.fn_mut_trait() == Some(p.def_id())
                     || lang_items.fn_once_trait() == Some(p.def_id())) =>
@@ -760,7 +760,7 @@ fn sig_for_projection<'tcx>(cx: &LateContext<'tcx>, ty: AliasTy<'tcx>) -> Option
                 }
                 inputs = Some(i);
             },
-            PredicateKind::Clause(ty::Clause::Projection(p))
+            PredicateKind::Clause(ty::ClauseKind::Projection(p))
                 if Some(p.projection_ty.def_id) == lang_items.fn_once_output() =>
             {
                 if output.is_some() {
@@ -950,7 +950,7 @@ pub fn ty_is_fn_once_param<'tcx>(tcx: TyCtxt<'_>, ty: Ty<'tcx>, predicates: &'tc
     predicates
         .iter()
         .try_fold(false, |found, p| {
-            if let PredicateKind::Clause(ty::Clause::Trait(p)) = p.kind().skip_binder()
+            if let PredicateKind::Clause(ty::ClauseKind::Trait(p)) = p.kind().skip_binder()
             && let ty::Param(self_ty) = p.trait_ref.self_ty().kind()
             && ty.index == self_ty.index
         {