Auto merge of #118661 - fee1-dead-contrib:restore-const-partialEq, r=compiler-errors

Restore `const PartialEq`

And thus fixes a number of tests. There is a bug that still needs to be fixed, so WIP for now.

r? `@compiler-errors`

38 files changed, 149 insertions, 194 deletions

diff --git a/compiler/rustc_const_eval/src/util/type_name.rs b/compiler/rustc_const_eval/src/util/type_name.rs
index b6240906611..a82b65b19a8 100644
--- a/compiler/rustc_const_eval/src/util/type_name.rs
+++ b/compiler/rustc_const_eval/src/util/type_name.rs
@@ -120,7 +120,6 @@ impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> {
         &mut self,
         print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
         args: &[GenericArg<'tcx>],
-        _params: &[ty::GenericParamDef],
     ) -> Result<(), PrintError> {
         print_prefix(self)?;
         let args =
diff --git a/compiler/rustc_infer/src/infer/error_reporting/mod.rs b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
index 0004f16fc4e..745c3d195ad 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/mod.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
@@ -641,7 +641,6 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                 &mut self,
                 print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
                 _args: &[GenericArg<'tcx>],
-                _params: &[ty::GenericParamDef],
             ) -> Result<(), PrintError> {
                 print_prefix(self)
             }
@@ -1237,9 +1236,9 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
             (&ty::Adt(def1, sub1), &ty::Adt(def2, sub2)) => {
                 let did1 = def1.did();
                 let did2 = def2.did();
-                let (sub_no_defaults_1, _) =
+                let sub_no_defaults_1 =
                     self.tcx.generics_of(did1).own_args_no_defaults(self.tcx, sub1);
-                let (sub_no_defaults_2, _) =
+                let sub_no_defaults_2 =
                     self.tcx.generics_of(did2).own_args_no_defaults(self.tcx, sub2);
                 let mut values = (DiagnosticStyledString::new(), DiagnosticStyledString::new());
                 let path1 = self.tcx.def_path_str(did1);
diff --git a/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs b/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs
index b8dc42b73cd..8fe6c1b0d86 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs
@@ -757,7 +757,6 @@ impl<'a, 'tcx> FindInferSourceVisitor<'a, 'tcx> {
                             .tcx
                             .generics_of(def.did())
                             .own_args_no_defaults(self.tcx, args)
-                            .0
                             .iter()
                             .map(|&arg| self.arg_cost(arg))
                             .sum::<usize>()
@@ -1186,7 +1185,7 @@ impl<'a, 'tcx> Visitor<'tcx> for FindInferSourceVisitor<'a, 'tcx> {
                 }
                 let args = self.infcx.resolve_vars_if_possible(args);
                 let generic_args =
-                    &generics.own_args_no_defaults(tcx, args).0[generics.own_counts().lifetimes..];
+                    &generics.own_args_no_defaults(tcx, args)[generics.own_counts().lifetimes..];
                 let span = match expr.kind {
                     ExprKind::MethodCall(path, ..) => path.ident.span,
                     _ => expr.span,
diff --git a/compiler/rustc_infer/src/infer/error_reporting/note_and_explain.rs b/compiler/rustc_infer/src/infer/error_reporting/note_and_explain.rs
index e2e9102a61a..b93fe02aaea 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/note_and_explain.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/note_and_explain.rs
@@ -116,7 +116,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                             // FIXME: extract this logic for use in other diagnostics.
                             let (trait_ref, assoc_args) = proj.trait_ref_and_own_args(tcx);
                             let item_name = tcx.item_name(proj.def_id);
-                            let item_args = self.format_generic_args(proj.def_id, assoc_args);
+                            let item_args = self.format_generic_args(assoc_args);
 
                             // Here, we try to see if there's an existing
                             // trait implementation that matches the one that
@@ -775,7 +775,7 @@ fn foo(&self) -> Self::T { String::new() }
                 let span = Span::new(pos, pos, span.ctxt(), span.parent());
                 (span, format!(", {} = {}", assoc.ident(tcx), ty))
             } else {
-                let item_args = self.format_generic_args(assoc.def_id, assoc_args);
+                let item_args = self.format_generic_args(assoc_args);
                 (span.shrink_to_hi(), format!("<{}{} = {}>", assoc.ident(tcx), item_args, ty))
             };
             diag.span_suggestion_verbose(span, msg(), sugg, MaybeIncorrect);
@@ -784,13 +784,9 @@ fn foo(&self) -> Self::T { String::new() }
         false
     }
 
-    pub fn format_generic_args(
-        &self,
-        assoc_def_id: DefId,
-        args: &[ty::GenericArg<'tcx>],
-    ) -> String {
+    pub fn format_generic_args(&self, args: &[ty::GenericArg<'tcx>]) -> String {
         FmtPrinter::print_string(self.tcx, hir::def::Namespace::TypeNS, |cx| {
-            cx.path_generic_args(|_| Ok(()), args, &self.infcx.tcx.generics_of(assoc_def_id).params)
+            cx.path_generic_args(|_| Ok(()), args)
         })
         .expect("could not write to `String`.")
     }
diff --git a/compiler/rustc_lint/src/context.rs b/compiler/rustc_lint/src/context.rs
index e3bda0828cb..024e542d4af 100644
--- a/compiler/rustc_lint/src/context.rs
+++ b/compiler/rustc_lint/src/context.rs
@@ -1285,7 +1285,6 @@ impl<'tcx> LateContext<'tcx> {
                 &mut self,
                 print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
                 _args: &[GenericArg<'tcx>],
-                _params: &[ty::GenericParamDef],
             ) -> Result<(), PrintError> {
                 print_prefix(self)
             }
diff --git a/compiler/rustc_middle/src/hir/map/mod.rs b/compiler/rustc_middle/src/hir/map/mod.rs
index d376036d832..4af886a9718 100644
--- a/compiler/rustc_middle/src/hir/map/mod.rs
+++ b/compiler/rustc_middle/src/hir/map/mod.rs
@@ -336,7 +336,8 @@ impl<'hir> Map<'hir> {
     /// Returns the `BodyOwnerKind` of this `LocalDefId`.
     ///
     /// Panics if `LocalDefId` does not have an associated body.
-    pub fn body_owner_kind(self, def_id: LocalDefId) -> BodyOwnerKind {
+    pub fn body_owner_kind(self, def_id: impl Into<DefId>) -> BodyOwnerKind {
+        let def_id = def_id.into();
         match self.tcx.def_kind(def_id) {
             DefKind::Const | DefKind::AssocConst | DefKind::AnonConst => {
                 BodyOwnerKind::Const { inline: false }
@@ -356,20 +357,17 @@ impl<'hir> Map<'hir> {
     /// This should only be used for determining the context of a body, a return
     /// value of `Some` does not always suggest that the owner of the body is `const`,
     /// just that it has to be checked as if it were.
-    pub fn body_const_context(self, def_id: LocalDefId) -> Option<ConstContext> {
+    pub fn body_const_context(self, def_id: impl Into<DefId>) -> Option<ConstContext> {
+        let def_id = def_id.into();
         let ccx = match self.body_owner_kind(def_id) {
             BodyOwnerKind::Const { inline } => ConstContext::Const { inline },
             BodyOwnerKind::Static(mt) => ConstContext::Static(mt),
 
-            BodyOwnerKind::Fn if self.tcx.is_constructor(def_id.to_def_id()) => return None,
-            BodyOwnerKind::Fn | BodyOwnerKind::Closure
-                if self.tcx.is_const_fn_raw(def_id.to_def_id()) =>
-            {
-                ConstContext::ConstFn
-            }
-            BodyOwnerKind::Fn if self.tcx.is_const_default_method(def_id.to_def_id()) => {
+            BodyOwnerKind::Fn if self.tcx.is_constructor(def_id) => return None,
+            BodyOwnerKind::Fn | BodyOwnerKind::Closure if self.tcx.is_const_fn_raw(def_id) => {
                 ConstContext::ConstFn
             }
+            BodyOwnerKind::Fn if self.tcx.is_const_default_method(def_id) => ConstContext::ConstFn,
             BodyOwnerKind::Fn | BodyOwnerKind::Closure => return None,
         };
 
diff --git a/compiler/rustc_middle/src/ty/generics.rs b/compiler/rustc_middle/src/ty/generics.rs
index 12294b0a602..c3699b114c4 100644
--- a/compiler/rustc_middle/src/ty/generics.rs
+++ b/compiler/rustc_middle/src/ty/generics.rs
@@ -320,21 +320,21 @@ impl<'tcx> Generics {
         &'tcx self,
         tcx: TyCtxt<'tcx>,
         args: &'tcx [ty::GenericArg<'tcx>],
-    ) -> (&'tcx [ty::GenericArg<'tcx>], &'tcx [ty::GenericParamDef]) {
-        let mut own_args = self.parent_count..self.count();
-        let mut own_params = 0..self.params.len();
+    ) -> &'tcx [ty::GenericArg<'tcx>] {
+        let mut own_params = self.parent_count..self.count();
         if self.has_self && self.parent.is_none() {
-            own_args.start = 1;
             own_params.start = 1;
         }
 
+        let verbose = tcx.sess.verbose();
+
         // Filter the default arguments.
         //
         // This currently uses structural equality instead
         // of semantic equivalence. While not ideal, that's
         // good enough for now as this should only be used
         // for diagnostics anyways.
-        let num_default_params = self
+        own_params.end -= self
             .params
             .iter()
             .rev()
@@ -342,12 +342,12 @@ impl<'tcx> Generics {
                 param.default_value(tcx).is_some_and(|default| {
                     default.instantiate(tcx, args) == args[param.index as usize]
                 })
+                // filter out trailing effect params, if we're not in `-Zverbose`.
+                || (!verbose && matches!(param.kind, GenericParamDefKind::Const { is_host_effect: true, .. }))
             })
             .count();
-        own_params.end -= num_default_params;
-        own_args.end -= num_default_params;
 
-        (&args[own_args], &self.params[own_params])
+        &args[own_params]
     }
 
     /// Returns the args corresponding to the generic parameters of this item, excluding `Self`.
diff --git a/compiler/rustc_middle/src/ty/print/mod.rs b/compiler/rustc_middle/src/ty/print/mod.rs
index 948246c64e2..5e09154789a 100644
--- a/compiler/rustc_middle/src/ty/print/mod.rs
+++ b/compiler/rustc_middle/src/ty/print/mod.rs
@@ -83,7 +83,6 @@ pub trait Printer<'tcx>: Sized {
         &mut self,
         print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
         args: &[GenericArg<'tcx>],
-        params: &[ty::GenericParamDef],
     ) -> Result<(), PrintError>;
 
     // Defaults (should not be overridden):
@@ -142,12 +141,10 @@ pub trait Printer<'tcx>: Sized {
                         // on top of the same path, but without its own generics.
                         _ => {
                             if !generics.params.is_empty() && args.len() >= generics.count() {
-                                let (args, params) =
-                                    generics.own_args_no_defaults(self.tcx(), args);
+                                let args = generics.own_args_no_defaults(self.tcx(), args);
                                 return self.path_generic_args(
                                     |cx| cx.print_def_path(def_id, parent_args),
                                     args,
-                                    params,
                                 );
                             }
                         }
diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs
index 90358686fef..39adfac55ce 100644
--- a/compiler/rustc_middle/src/ty/print/pretty.rs
+++ b/compiler/rustc_middle/src/ty/print/pretty.rs
@@ -965,7 +965,7 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                 define_scoped_cx!(cx);
                 // Get the (single) generic ty (the args) of this FnOnce trait ref.
                 let generics = tcx.generics_of(trait_ref.def_id);
-                let (own_args, _) = generics.own_args_no_defaults(tcx, trait_ref.args);
+                let own_args = generics.own_args_no_defaults(tcx, trait_ref.args);
 
                 match (entry.return_ty, own_args[0].expect_ty()) {
                     // We can only print `impl Fn() -> ()` if we have a tuple of args and we recorded
@@ -1031,7 +1031,7 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                 p!(print(trait_ref.print_only_trait_name()));
 
                 let generics = tcx.generics_of(trait_ref.def_id);
-                let (own_args, _) = generics.own_args_no_defaults(tcx, trait_ref.args);
+                let own_args = generics.own_args_no_defaults(tcx, trait_ref.args);
 
                 if !own_args.is_empty() || !assoc_items.is_empty() {
                     let mut first = true;
@@ -1183,7 +1183,6 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                 )
             },
             &alias_ty.args[1..],
-            &self.tcx().generics_of(alias_ty.def_id).params,
         )
     }
 
@@ -1232,7 +1231,7 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                     let dummy_cx = Ty::new_fresh(cx.tcx(), 0);
                     let principal = principal.with_self_ty(cx.tcx(), dummy_cx);
 
-                    let (args, _) = cx
+                    let args = cx
                         .tcx()
                         .generics_of(principal.def_id)
                         .own_args_no_defaults(cx.tcx(), principal.args);
@@ -2030,26 +2029,14 @@ impl<'tcx> Printer<'tcx> for FmtPrinter<'_, 'tcx> {
         &mut self,
         print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
         args: &[GenericArg<'tcx>],
-        params: &[ty::GenericParamDef],
     ) -> Result<(), PrintError> {
         print_prefix(self)?;
 
-        let tcx = self.tcx;
-        let verbose = tcx.sess.verbose();
-        let mut args = args
-            .iter()
-            .copied()
-            .zip(params)
-            // If -Zverbose is passed, we should print the host parameter instead
-            // of eating it.
-            .filter(|(_, param)| verbose || !param.is_host_effect())
-            .peekable();
-
-        if args.peek().is_some() {
+        if !args.is_empty() {
             if self.in_value {
                 write!(self, "::")?;
             }
-            self.generic_delimiters(|cx| cx.comma_sep(args.map(|(arg, _)| arg)))
+            self.generic_delimiters(|cx| cx.comma_sep(args.iter().copied()))
         } else {
             Ok(())
         }
@@ -2881,7 +2868,8 @@ define_print_and_forward_display! {
     TraitPredPrintModifiersAndPath<'tcx> {
         if let Some(idx) = cx.tcx().generics_of(self.0.trait_ref.def_id).host_effect_index
         {
-            if self.0.trait_ref.args.const_at(idx) != cx.tcx().consts.true_ {
+            let arg = self.0.trait_ref.args.const_at(idx);
+            if arg != cx.tcx().consts.true_ && !arg.has_infer() {
                 p!("~const ");
             }
         }
diff --git a/compiler/rustc_middle/src/ty/util.rs b/compiler/rustc_middle/src/ty/util.rs
index 1da090a7e46..8b1d33848ea 100644
--- a/compiler/rustc_middle/src/ty/util.rs
+++ b/compiler/rustc_middle/src/ty/util.rs
@@ -782,7 +782,8 @@ impl<'tcx> TyCtxt<'tcx> {
             || self.extern_crate(key.as_def_id()).is_some_and(|e| e.is_direct())
     }
 
-    pub fn expected_host_effect_param_for_body(self, def_id: LocalDefId) -> ty::Const<'tcx> {
+    pub fn expected_host_effect_param_for_body(self, def_id: impl Into<DefId>) -> ty::Const<'tcx> {
+        let def_id = def_id.into();
         // FIXME(effects): This is suspicious and should probably not be done,
         // especially now that we enforce host effects and then properly handle
         // effect vars during fallback.
diff --git a/compiler/rustc_symbol_mangling/src/legacy.rs b/compiler/rustc_symbol_mangling/src/legacy.rs
index 14cd46cb062..0178ff53b24 100644
--- a/compiler/rustc_symbol_mangling/src/legacy.rs
+++ b/compiler/rustc_symbol_mangling/src/legacy.rs
@@ -342,7 +342,6 @@ impl<'tcx> Printer<'tcx> for SymbolPrinter<'tcx> {
         &mut self,
         print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
         args: &[GenericArg<'tcx>],
-        _params: &[ty::GenericParamDef],
     ) -> Result<(), PrintError> {
         print_prefix(self)?;
 
diff --git a/compiler/rustc_symbol_mangling/src/v0.rs b/compiler/rustc_symbol_mangling/src/v0.rs
index 112e06a0dc2..e002e345ae6 100644
--- a/compiler/rustc_symbol_mangling/src/v0.rs
+++ b/compiler/rustc_symbol_mangling/src/v0.rs
@@ -298,7 +298,6 @@ impl<'tcx> Printer<'tcx> for SymbolMangler<'tcx> {
                     )
                 },
                 args,
-                &self.tcx.generics_of(impl_def_id).params,
             )?;
         } else {
             self.push_disambiguator(key.disambiguated_data.disambiguator as u64);
@@ -801,7 +800,6 @@ impl<'tcx> Printer<'tcx> for SymbolMangler<'tcx> {
         &mut self,
         print_prefix: impl FnOnce(&mut Self) -> Result<(), PrintError>,
         args: &[GenericArg<'tcx>],
-        _params: &[ty::GenericParamDef],
     ) -> Result<(), PrintError> {
         // Don't print any regions if they're all erased.
         let print_regions = args.iter().any(|arg| match arg.unpack() {
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
index 95ffd07e397..f7e8dc62a62 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
@@ -3628,17 +3628,19 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
             is_derivable_trait &&
                 // Ensure all fields impl the trait.
                 adt.all_fields().all(|field| {
-                    let field_ty = field.ty(self.tcx, args);
+                    let field_ty = ty::GenericArg::from(field.ty(self.tcx, args));
                     let trait_args = match diagnostic_name {
                         sym::PartialEq | sym::PartialOrd => {
                             Some(field_ty)
                         }
                         _ => None,
                     };
+                    // Also add host param, if present
+                    let host = self.tcx.generics_of(trait_pred.def_id()).host_effect_index.map(|idx| trait_pred.skip_binder().trait_ref.args[idx]);
                     let trait_pred = trait_pred.map_bound_ref(|tr| ty::TraitPredicate {
                         trait_ref: ty::TraitRef::new(self.tcx,
                             trait_pred.def_id(),
-                            [field_ty].into_iter().chain(trait_args),
+                            [field_ty].into_iter().chain(trait_args).chain(host),
                         ),
                         ..*tr
                     });
@@ -3659,6 +3661,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                     trait_pred.skip_binder().self_ty(),
                     diagnostic_name,
                 ),
+                // FIXME(effects, const_trait_impl) derive_const as suggestion?
                 format!("#[derive({diagnostic_name})]\n"),
                 Applicability::MaybeIncorrect,
             );
diff --git a/library/core/src/cmp.rs b/library/core/src/cmp.rs
index fadf2fcc9fc..85246f4f3dc 100644
--- a/library/core/src/cmp.rs
+++ b/library/core/src/cmp.rs
@@ -224,6 +224,7 @@ use self::Ordering::*;
     append_const_msg
 )]
 #[rustc_diagnostic_item = "PartialEq"]
+#[cfg_attr(not(bootstrap), const_trait)]
 pub trait PartialEq<Rhs: ?Sized = Self> {
     /// This method tests for `self` and `other` values to be equal, and is used
     /// by `==`.
@@ -1414,12 +1415,23 @@ mod impls {
     macro_rules! partial_eq_impl {
         ($($t:ty)*) => ($(
             #[stable(feature = "rust1", since = "1.0.0")]
+            #[cfg(bootstrap)]
             impl PartialEq for $t {
                 #[inline]
                 fn eq(&self, other: &$t) -> bool { (*self) == (*other) }
                 #[inline]
                 fn ne(&self, other: &$t) -> bool { (*self) != (*other) }
             }
+
+            #[stable(feature = "rust1", since = "1.0.0")]
+            #[rustc_const_unstable(feature = "const_cmp", issue = "92391")]
+            #[cfg(not(bootstrap))]
+            impl const PartialEq for $t {
+                #[inline]
+                fn eq(&self, other: &$t) -> bool { (*self) == (*other) }
+                #[inline]
+                fn ne(&self, other: &$t) -> bool { (*self) != (*other) }
+            }
         )*)
     }
 
diff --git a/src/tools/clippy/clippy_lints/src/derive.rs b/src/tools/clippy/clippy_lints/src/derive.rs
index 61faaa10b8a..d8abe411030 100644
--- a/src/tools/clippy/clippy_lints/src/derive.rs
+++ b/src/tools/clippy/clippy_lints/src/derive.rs
@@ -450,12 +450,12 @@ fn check_partial_eq_without_eq<'tcx>(cx: &LateContext<'tcx>, span: Span, trait_r
         && let Some(def_id) = trait_ref.trait_def_id()
         && cx.tcx.is_diagnostic_item(sym::PartialEq, def_id)
         && let param_env = param_env_for_derived_eq(cx.tcx, adt.did(), eq_trait_def_id)
-        && !implements_trait_with_env(cx.tcx, param_env, ty, eq_trait_def_id, &[])
+        && !implements_trait_with_env(cx.tcx, param_env, ty, eq_trait_def_id, adt.did(),&[])
         // If all of our fields implement `Eq`, we can implement `Eq` too
         && adt
             .all_fields()
             .map(|f| f.ty(cx.tcx, args))
-            .all(|ty| implements_trait_with_env(cx.tcx, param_env, ty, eq_trait_def_id, &[]))
+            .all(|ty| implements_trait_with_env(cx.tcx, param_env, ty, eq_trait_def_id, adt.did(), &[]))
     {
         span_lint_and_sugg(
             cx,
diff --git a/src/tools/clippy/clippy_lints/src/implied_bounds_in_impls.rs b/src/tools/clippy/clippy_lints/src/implied_bounds_in_impls.rs
index 9a66cbde53c..4811691c80d 100644
--- a/src/tools/clippy/clippy_lints/src/implied_bounds_in_impls.rs
+++ b/src/tools/clippy/clippy_lints/src/implied_bounds_in_impls.rs
@@ -194,6 +194,10 @@ fn is_same_generics<'tcx>(
         .enumerate()
         .skip(1) // skip `Self` implicit arg
         .all(|(arg_index, arg)| {
+            if [implied_by_generics.host_effect_index, implied_generics.host_effect_index].contains(&Some(arg_index)) {
+                // skip host effect params in determining whether generics are same
+                return true;
+            }
             if let Some(ty) = arg.as_type() {
                 if let &ty::Param(ty::ParamTy { index, .. }) = ty.kind()
                     // `index == 0` means that it's referring to `Self`,
diff --git a/src/tools/clippy/clippy_lints/src/loops/explicit_iter_loop.rs b/src/tools/clippy/clippy_lints/src/loops/explicit_iter_loop.rs
index 1c2b7a169fc..c7980060807 100644
--- a/src/tools/clippy/clippy_lints/src/loops/explicit_iter_loop.rs
+++ b/src/tools/clippy/clippy_lints/src/loops/explicit_iter_loop.rs
@@ -118,7 +118,7 @@ fn is_ref_iterable<'tcx>(
             .liberate_late_bound_regions(fn_id, cx.tcx.fn_sig(fn_id).skip_binder())
         && let &[req_self_ty, req_res_ty] = &**sig.inputs_and_output
         && let param_env = cx.tcx.param_env(fn_id)
-        && implements_trait_with_env(cx.tcx, param_env, req_self_ty, trait_id, &[])
+        && implements_trait_with_env(cx.tcx, param_env, req_self_ty, trait_id, fn_id, &[])
         && let Some(into_iter_ty) =
             make_normalized_projection_with_regions(cx.tcx, param_env, trait_id, sym!(IntoIter), [req_self_ty])
         && let req_res_ty = normalize_with_regions(cx.tcx, param_env, req_res_ty)
diff --git a/src/tools/clippy/clippy_lints/src/needless_pass_by_value.rs b/src/tools/clippy/clippy_lints/src/needless_pass_by_value.rs
index 27da44812eb..2c5c3dcaa75 100644
--- a/src/tools/clippy/clippy_lints/src/needless_pass_by_value.rs
+++ b/src/tools/clippy/clippy_lints/src/needless_pass_by_value.rs
@@ -186,6 +186,7 @@ impl<'tcx> LateLintPass<'tcx> for NeedlessPassByValue {
                         cx.param_env,
                         ty,
                         t,
+                        None,
                         [Option::<ty::GenericArg<'tcx>>::None],
                     )
                 })
diff --git a/src/tools/clippy/clippy_utils/src/ty.rs b/src/tools/clippy/clippy_utils/src/ty.rs
index 1e748a46922..868c92f2f54 100644
--- a/src/tools/clippy/clippy_utils/src/ty.rs
+++ b/src/tools/clippy/clippy_utils/src/ty.rs
@@ -214,7 +214,8 @@ pub fn implements_trait<'tcx>(
     trait_id: DefId,
     args: &[GenericArg<'tcx>],
 ) -> bool {
-    implements_trait_with_env_from_iter(cx.tcx, cx.param_env, ty, trait_id, args.iter().map(|&x| Some(x)))
+    let callee_id = cx.enclosing_body.map(|body| cx.tcx.hir().body_owner(body).owner.to_def_id());
+    implements_trait_with_env_from_iter(cx.tcx, cx.param_env, ty, trait_id, callee_id, args.iter().map(|&x| Some(x)))
 }
 
 /// Same as `implements_trait` but allows using a `ParamEnv` different from the lint context.
@@ -223,9 +224,10 @@ pub fn implements_trait_with_env<'tcx>(
     param_env: ParamEnv<'tcx>,
     ty: Ty<'tcx>,
     trait_id: DefId,
+    callee_id: DefId,
     args: &[GenericArg<'tcx>],
 ) -> bool {
-    implements_trait_with_env_from_iter(tcx, param_env, ty, trait_id, args.iter().map(|&x| Some(x)))
+    implements_trait_with_env_from_iter(tcx, param_env, ty, trait_id, Some(callee_id), args.iter().map(|&x| Some(x)))
 }
 
 /// Same as `implements_trait_from_env` but takes the arguments as an iterator.
@@ -234,6 +236,7 @@ pub fn implements_trait_with_env_from_iter<'tcx>(
     param_env: ParamEnv<'tcx>,
     ty: Ty<'tcx>,
     trait_id: DefId,
+    callee_id: Option<DefId>,
     args: impl IntoIterator<Item = impl Into<Option<GenericArg<'tcx>>>>,
 ) -> bool {
     // Clippy shouldn't have infer types
@@ -245,20 +248,29 @@ pub fn implements_trait_with_env_from_iter<'tcx>(
     }
 
     let infcx = tcx.infer_ctxt().build();
+    let args = args.into_iter().map(|arg| {
+        arg.into().unwrap_or_else(|| {
+            let orig = TypeVariableOrigin {
+                kind: TypeVariableOriginKind::MiscVariable,
+                span: DUMMY_SP,
+            };
+            infcx.next_ty_var(orig).into()
+        })
+    }).collect::<Vec<_>>();
+
+    // If an effect arg was not specified, we need to specify it.
+    let effect_arg = if tcx.generics_of(trait_id).host_effect_index.is_some_and(|x| args.get(x - 1).is_none()) {
+        Some(GenericArg::from(callee_id.map(|def_id| tcx.expected_host_effect_param_for_body(def_id)).unwrap_or(tcx.consts.true_)))
+    } else {
+        None
+    };
+
     let trait_ref = TraitRef::new(
         tcx,
         trait_id,
         Some(GenericArg::from(ty))
             .into_iter()
-            .chain(args.into_iter().map(|arg| {
-                arg.into().unwrap_or_else(|| {
-                    let orig = TypeVariableOrigin {
-                        kind: TypeVariableOriginKind::MiscVariable,
-                        span: DUMMY_SP,
-                    };
-                    infcx.next_ty_var(orig).into()
-                })
-            })),
+            .chain(args).chain(effect_arg),
     );
 
     debug_assert_matches!(
diff --git a/tests/ui/consts/fn_trait_refs.stderr b/tests/ui/consts/fn_trait_refs.stderr
index 3d82837d530..e5ebe1d8528 100644
--- a/tests/ui/consts/fn_trait_refs.stderr
+++ b/tests/ui/consts/fn_trait_refs.stderr
@@ -4,12 +4,6 @@ error[E0635]: unknown feature `const_fn_trait_ref_impls`
 LL | #![feature(const_fn_trait_ref_impls)]
    |            ^^^^^^^^^^^^^^^^^^^^^^^^
 
-error[E0635]: unknown feature `const_cmp`
-  --> $DIR/fn_trait_refs.rs:8:12
-   |
-LL | #![feature(const_cmp)]
-   |            ^^^^^^^^^
-
 error: ~const can only be applied to `#[const_trait]` traits
   --> $DIR/fn_trait_refs.rs:15:15
    |
@@ -80,6 +74,6 @@ LL |     T: ~const FnMut<()> + ~const Destruct,
    |
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
-error: aborting due to 12 previous errors
+error: aborting due to 11 previous errors
 
 For more information about this error, try `rustc --explain E0635`.
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-in-impl.rs b/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-in-impl.rs
index 5120e6bfb41..50c46579086 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-in-impl.rs
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-in-impl.rs
@@ -1,4 +1,4 @@
-// known-bug: #110395
+// check-pass
 #![feature(const_trait_impl)]
 
 #[const_trait]
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-in-impl.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-in-impl.stderr
deleted file mode 100644
index 4007fd455f8..00000000000
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-in-impl.stderr
+++ /dev/null
@@ -1,8 +0,0 @@
-error: ~const can only be applied to `#[const_trait]` traits
-  --> $DIR/call-generic-in-impl.rs:9:16
-   |
-LL | impl<T: ~const PartialEq> const MyPartialEq for T {
-   |                ^^^^^^^^^
-
-error: aborting due to 1 previous error
-
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-chain.rs b/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-chain.rs
index 3febb328a83..0df370bff8d 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-chain.rs
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-chain.rs
@@ -1,8 +1,8 @@
 //! Basic test for calling methods on generic type parameters in `const fn`.
 
-// known-bug: #110395
+// check-pass
 
-#![feature(const_trait_impl)]
+#![feature(const_trait_impl, effects)]
 
 struct S;
 
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-chain.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-chain.stderr
deleted file mode 100644
index 37faa3f6bce..00000000000
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-chain.stderr
+++ /dev/null
@@ -1,14 +0,0 @@
-error: ~const can only be applied to `#[const_trait]` traits
-  --> $DIR/call-generic-method-chain.rs:18:32
-   |
-LL | const fn equals_self<T: ~const PartialEq>(t: &T) -> bool {
-   |                                ^^^^^^^^^
-
-error: ~const can only be applied to `#[const_trait]` traits
-  --> $DIR/call-generic-method-chain.rs:22:40
-   |
-LL | const fn equals_self_wrapper<T: ~const PartialEq>(t: &T) -> bool {
-   |                                        ^^^^^^^^^
-
-error: aborting due to 2 previous errors
-
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-dup-bound.rs b/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-dup-bound.rs
index e618160d3b6..b0d5d068515 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-dup-bound.rs
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-dup-bound.rs
@@ -1,6 +1,6 @@
-// known-bug: #110395
+// check-pass
 
-#![feature(const_trait_impl)]
+#![feature(const_trait_impl, effects)]
 
 struct S;
 
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-dup-bound.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-dup-bound.stderr
deleted file mode 100644
index 90cfe04a9a8..00000000000
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-dup-bound.stderr
+++ /dev/null
@@ -1,14 +0,0 @@
-error: ~const can only be applied to `#[const_trait]` traits
-  --> $DIR/call-generic-method-dup-bound.rs:18:44
-   |
-LL | const fn equals_self<T: PartialEq + ~const PartialEq>(t: &T) -> bool {
-   |                                            ^^^^^^^^^
-
-error: ~const can only be applied to `#[const_trait]` traits
-  --> $DIR/call-generic-method-dup-bound.rs:25:37
-   |
-LL | const fn equals_self2<T: A + ~const PartialEq>(t: &T) -> bool {
-   |                                     ^^^^^^^^^
-
-error: aborting due to 2 previous errors
-
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-fail.rs b/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-fail.rs
index 53778b3af3d..043939750a8 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-fail.rs
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-fail.rs
@@ -1,10 +1,9 @@
-// FIXME(effects)
-// check-pass
 #![feature(const_trait_impl, effects)]
 
 pub const fn equals_self<T: PartialEq>(t: &T) -> bool {
     *t == *t
-    // (remove this) ~^ ERROR can't compare
+    //~^ ERROR mismatched types
+    // FIXME(effects): diagnostic
 }
 
 fn main() {}
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-fail.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-fail.stderr
new file mode 100644
index 00000000000..5074c4a2261
--- /dev/null
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-fail.stderr
@@ -0,0 +1,12 @@
+error[E0308]: mismatched types
+  --> $DIR/call-generic-method-fail.rs:4:5
+   |
+LL |     *t == *t
+   |     ^^^^^^^^ expected `host`, found `true`
+   |
+   = note: expected constant `host`
+              found constant `true`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0308`.
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-nonconst.rs b/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-nonconst.rs
index b9331caaf8e..76bc738123d 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-nonconst.rs
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-nonconst.rs
@@ -21,7 +21,6 @@ const fn equals_self<T: ~const Foo>(t: &T) -> bool {
 // it not using the impl.
 
 pub const EQ: bool = equals_self(&S);
-//~^ ERROR
-// FIXME(effects) the diagnostics here isn't ideal, we shouldn't get `<false>`
+//~^ ERROR: the trait bound `S: ~const Foo` is not satisfied
 
 fn main() {}
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-pass.rs b/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-pass.rs
index 09f35a27737..abd5d2fdb39 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-pass.rs
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-pass.rs
@@ -1,8 +1,8 @@
 //! Basic test for calling methods on generic type parameters in `const fn`.
 
-// known-bug: #110395
+// check-pass
 
-#![feature(const_trait_impl)]
+#![feature(const_trait_impl, effects)]
 
 struct S;
 
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-pass.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-pass.stderr
deleted file mode 100644
index 1f7cf689e95..00000000000
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/call-generic-method-pass.stderr
+++ /dev/null
@@ -1,8 +0,0 @@
-error: ~const can only be applied to `#[const_trait]` traits
-  --> $DIR/call-generic-method-pass.rs:18:32
-   |
-LL | const fn equals_self<T: ~const PartialEq>(t: &T) -> bool {
-   |                                ^^^^^^^^^
-
-error: aborting due to 1 previous error
-
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/const-impl-trait.rs b/tests/ui/rfcs/rfc-2632-const-trait-impl/const-impl-trait.rs
index 8e4de57b019..14d306fc31f 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/const-impl-trait.rs
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/const-impl-trait.rs
@@ -3,6 +3,7 @@
 #![feature(
     associated_type_bounds,
     const_trait_impl,
+    effects,
     const_cmp,
 )]
 
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/const-impl-trait.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/const-impl-trait.stderr
index 4a9090d0b53..ddedf8f1d8d 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/const-impl-trait.stderr
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/const-impl-trait.stderr
@@ -1,39 +1,28 @@
-error[E0635]: unknown feature `const_cmp`
-  --> $DIR/const-impl-trait.rs:6:5
+error[E0277]: can't compare `impl PartialEq + Destruct + Copy` with `impl PartialEq + Destruct + Copy`
+  --> $DIR/const-impl-trait.rs:28:17
    |
-LL |     const_cmp,
-   |     ^^^^^^^^^
-
-error: ~const can only be applied to `#[const_trait]` traits
-  --> $DIR/const-impl-trait.rs:11:30
-   |
-LL | const fn cmp(a: &impl ~const PartialEq) -> bool {
-   |                              ^^^^^^^^^
-
-error: ~const can only be applied to `#[const_trait]` traits
-  --> $DIR/const-impl-trait.rs:15:30
-   |
-LL | const fn wrap(x: impl ~const PartialEq + ~const Destruct)
-   |                              ^^^^^^^^^
-
-error: ~const can only be applied to `#[const_trait]` traits
-  --> $DIR/const-impl-trait.rs:16:20
+LL |     fn huh() -> impl ~const PartialEq + ~const Destruct + Copy {
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ no implementation for `impl PartialEq + Destruct + Copy == impl PartialEq + Destruct + Copy`
    |
-LL |     -> impl ~const PartialEq + ~const Destruct
-   |                    ^^^^^^^^^
-
-error: ~const can only be applied to `#[const_trait]` traits
-  --> $DIR/const-impl-trait.rs:23:29
+   = help: the trait `~const PartialEq` is not implemented for `impl PartialEq + Destruct + Copy`
+note: required by a bound in `Foo::{opaque#0}`
+  --> $DIR/const-impl-trait.rs:24:22
    |
 LL |     fn huh() -> impl ~const PartialEq + ~const Destruct + Copy;
-   |                             ^^^^^^^^^
+   |                      ^^^^^^^^^^^^^^^^ required by this bound in `Foo::{opaque#0}`
 
-error: ~const can only be applied to `#[const_trait]` traits
-  --> $DIR/const-impl-trait.rs:27:29
+error[E0277]: can't drop `impl PartialEq + Destruct + Copy`
+  --> $DIR/const-impl-trait.rs:28:17
    |
 LL |     fn huh() -> impl ~const PartialEq + ~const Destruct + Copy {
-   |                             ^^^^^^^^^
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `~const Destruct` is not implemented for `impl PartialEq + Destruct + Copy`
+   |
+note: required by a bound in `Foo::{opaque#0}`
+  --> $DIR/const-impl-trait.rs:24:41
+   |
+LL |     fn huh() -> impl ~const PartialEq + ~const Destruct + Copy;
+   |                                         ^^^^^^^^^^^^^^^ required by this bound in `Foo::{opaque#0}`
 
-error: aborting due to 6 previous errors
+error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0635`.
+For more information about this error, try `rustc --explain E0277`.
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/const_derives/derive-const-use.rs b/tests/ui/rfcs/rfc-2632-const-trait-impl/const_derives/derive-const-use.rs
index 69098542b7e..42d7283699f 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/const_derives/derive-const-use.rs
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/const_derives/derive-const-use.rs
@@ -1,5 +1,6 @@
 // known-bug: #110395
-#![feature(const_trait_impl, const_cmp, const_default_impls, derive_const)]
+
+#![feature(const_trait_impl, const_cmp, const_default_impls, derive_const, effects)]
 
 pub struct A;
 
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/const_derives/derive-const-use.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/const_derives/derive-const-use.stderr
index 046dbae0eae..c561f80653c 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/const_derives/derive-const-use.stderr
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/const_derives/derive-const-use.stderr
@@ -1,15 +1,28 @@
-error[E0635]: unknown feature `const_cmp`
-  --> $DIR/derive-const-use.rs:2:30
-   |
-LL | #![feature(const_trait_impl, const_cmp, const_default_impls, derive_const)]
-   |                              ^^^^^^^^^
-
 error[E0635]: unknown feature `const_default_impls`
-  --> $DIR/derive-const-use.rs:2:41
+  --> $DIR/derive-const-use.rs:3:41
    |
-LL | #![feature(const_trait_impl, const_cmp, const_default_impls, derive_const)]
+LL | #![feature(const_trait_impl, const_cmp, const_default_impls, derive_const, effects)]
    |                                         ^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 2 previous errors
+error: const `impl` for trait `Default` which is not marked with `#[const_trait]`
+  --> $DIR/derive-const-use.rs:7:12
+   |
+LL | impl const Default for A {
+   |            ^^^^^^^
+   |
+   = note: marking a trait with `#[const_trait]` ensures all default method bodies are `const`
+   = note: adding a non-const method body in the future would be a breaking change
+
+error: const `impl` for trait `Default` which is not marked with `#[const_trait]`
+  --> $DIR/derive-const-use.rs:15:16
+   |
+LL | #[derive_const(Default, PartialEq)]
+   |                ^^^^^^^
+   |
+   = note: marking a trait with `#[const_trait]` ensures all default method bodies are `const`
+   = note: adding a non-const method body in the future would be a breaking change
+   = note: this error originates in the derive macro `Default` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0635`.
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/const_derives/derive-const-with-params.rs b/tests/ui/rfcs/rfc-2632-const-trait-impl/const_derives/derive-const-with-params.rs
index 2a5d0176ba0..b479c967b0d 100644
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/const_derives/derive-const-with-params.rs
+++ b/tests/ui/rfcs/rfc-2632-const-trait-impl/const_derives/derive-const-with-params.rs
@@ -1,7 +1,7 @@
-// known-bug: #110395
+// check-pass
 
 #![feature(derive_const)]
-#![feature(const_trait_impl)]
+#![feature(const_trait_impl, effects)]
 
 #[derive_const(PartialEq)]
 pub struct Reverse<T>(T);
diff --git a/tests/ui/rfcs/rfc-2632-const-trait-impl/const_derives/derive-const-with-params.stderr b/tests/ui/rfcs/rfc-2632-const-trait-impl/const_derives/derive-const-with-params.stderr
deleted file mode 100644
index 3a8c4833414..00000000000
--- a/tests/ui/rfcs/rfc-2632-const-trait-impl/const_derives/derive-const-with-params.stderr
+++ /dev/null
@@ -1,10 +0,0 @@
-error: ~const can only be applied to `#[const_trait]` traits
-  --> $DIR/derive-const-with-params.rs:6:16
-   |
-LL | #[derive_const(PartialEq)]
-   |                ^^^^^^^^^
-   |
-   = note: this error originates in the derive macro `PartialEq` (in Nightly builds, run with -Z macro-backtrace for more info)
-
-error: aborting due to 1 previous error
-
diff --git a/tests/ui/suggestions/invalid-bin-op.stderr b/tests/ui/suggestions/invalid-bin-op.stderr
index 018250c8c1b..2bd745c645a 100644
--- a/tests/ui/suggestions/invalid-bin-op.stderr
+++ b/tests/ui/suggestions/invalid-bin-op.stderr
@@ -16,10 +16,6 @@ help: consider annotating `S<T>` with `#[derive(PartialEq)]`
 LL + #[derive(PartialEq)]
 LL | struct S<T>(T);
    |
-help: consider introducing a `where` clause, but there might be an alternative better way to express this requirement
-   |
-LL | pub fn foo<T>(s: S<T>, t: S<T>) where S<T>: PartialEq {
-   |                                 +++++++++++++++++++++
 
 error: aborting due to 1 previous error