Rollup merge of #137183 - compiler-errors:dead-regionck-code, r=lcnr

Prune dead regionck code

We never encounter `ObligationCauseCode`s that correspond to region obligations that originate from "within" a body, since we don't do HIR regionck anymore on bodies. So prune some dead code.

7 files changed, 9 insertions, 241 deletions

diff --git a/compiler/rustc_hir_typeck/src/method/confirm.rs b/compiler/rustc_hir_typeck/src/method/confirm.rs
index 8fb425ff0c9..3b107fbf173 100644
--- a/compiler/rustc_hir_typeck/src/method/confirm.rs
+++ b/compiler/rustc_hir_typeck/src/method/confirm.rs
@@ -11,7 +11,7 @@ use rustc_hir_analysis::hir_ty_lowering::{
 };
 use rustc_infer::infer::{self, DefineOpaqueTypes, InferOk};
 use rustc_lint::builtin::SUPERTRAIT_ITEM_SHADOWING_USAGE;
-use rustc_middle::traits::{ObligationCauseCode, UnifyReceiverContext};
+use rustc_middle::traits::ObligationCauseCode;
 use rustc_middle::ty::adjustment::{
     Adjust, Adjustment, AllowTwoPhase, AutoBorrow, AutoBorrowMutability, PointerCoercion,
 };
@@ -136,7 +136,7 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
             "confirm: self_ty={:?} method_sig_rcvr={:?} method_sig={:?} method_predicates={:?}",
             self_ty, method_sig_rcvr, method_sig, method_predicates
         );
-        self.unify_receivers(self_ty, method_sig_rcvr, pick, all_args);
+        self.unify_receivers(self_ty, method_sig_rcvr, pick);
 
         let (method_sig, method_predicates) =
             self.normalize(self.span, (method_sig, method_predicates));
@@ -525,20 +525,12 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
         self_ty: Ty<'tcx>,
         method_self_ty: Ty<'tcx>,
         pick: &probe::Pick<'tcx>,
-        args: GenericArgsRef<'tcx>,
     ) {
         debug!(
             "unify_receivers: self_ty={:?} method_self_ty={:?} span={:?} pick={:?}",
             self_ty, method_self_ty, self.span, pick
         );
-        let cause = self.cause(
-            self.self_expr.span,
-            ObligationCauseCode::UnifyReceiver(Box::new(UnifyReceiverContext {
-                assoc_item: pick.item,
-                param_env: self.param_env,
-                args,
-            })),
-        );
+        let cause = self.cause(self.self_expr.span, ObligationCauseCode::Misc);
         match self.at(&cause, self.param_env).sup(DefineOpaqueTypes::Yes, method_self_ty, self_ty) {
             Ok(InferOk { obligations, value: () }) => {
                 self.register_predicates(obligations);
diff --git a/compiler/rustc_middle/src/traits/mod.rs b/compiler/rustc_middle/src/traits/mod.rs
index 54cd8cc3efe..fe959815f36 100644
--- a/compiler/rustc_middle/src/traits/mod.rs
+++ b/compiler/rustc_middle/src/traits/mod.rs
@@ -144,14 +144,6 @@ impl<'tcx> ObligationCause<'tcx> {
     }
 }
 
-#[derive(Clone, Debug, PartialEq, Eq, HashStable, TyEncodable, TyDecodable)]
-#[derive(TypeVisitable, TypeFoldable)]
-pub struct UnifyReceiverContext<'tcx> {
-    pub assoc_item: ty::AssocItem,
-    pub param_env: ty::ParamEnv<'tcx>,
-    pub args: GenericArgsRef<'tcx>,
-}
-
 /// A compact form of `ObligationCauseCode`.
 #[derive(Clone, PartialEq, Eq, Default, HashStable)]
 #[derive(TypeVisitable, TypeFoldable, TyEncodable, TyDecodable)]
@@ -360,8 +352,6 @@ pub enum ObligationCauseCode<'tcx> {
     /// Method receiver
     MethodReceiver,
 
-    UnifyReceiver(Box<UnifyReceiverContext<'tcx>>),
-
     /// `return` with no expression
     ReturnNoExpression,
 
diff --git a/compiler/rustc_trait_selection/messages.ftl b/compiler/rustc_trait_selection/messages.ftl
index 055a3edcc32..4db9d9915b1 100644
--- a/compiler/rustc_trait_selection/messages.ftl
+++ b/compiler/rustc_trait_selection/messages.ftl
@@ -225,14 +225,6 @@ trait_selection_mismatched_static_lifetime = incompatible lifetime on type
 trait_selection_missing_options_for_on_unimplemented_attr = missing options for `on_unimplemented` attribute
     .help = at least one of the `message`, `note` and `label` options are expected
 
-trait_selection_more_targeted = {$has_param_name ->
-    [true] `{$param_name}`
-    *[false] `fn` parameter
-} has {$has_lifetime ->
-    [true] lifetime `{$lifetime}`
-    *[false] an anonymous lifetime `'_`
-} but calling `{$ident}` introduces an implicit `'static` lifetime requirement
-
 trait_selection_msl_introduces_static = introduces a `'static` lifetime requirement
 trait_selection_msl_unmet_req = because this has an unmet lifetime requirement
 
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/mismatched_static_lifetime.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/mismatched_static_lifetime.rs
index ad2f7f00fa5..0904177ea8b 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/mismatched_static_lifetime.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/mismatched_static_lifetime.rs
@@ -33,11 +33,7 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
         };
         // If we added a "points at argument expression" obligation, we remove it here, we care
         // about the original obligation only.
-        let code = match cause.code() {
-            ObligationCauseCode::FunctionArg { parent_code, .. } => &*parent_code,
-            code => code,
-        };
-        let ObligationCauseCode::MatchImpl(parent, impl_def_id) = code else {
+        let ObligationCauseCode::MatchImpl(parent, impl_def_id) = cause.code() else {
             return None;
         };
         let (ObligationCauseCode::WhereClause(_, binding_span)
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/static_impl_trait.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/static_impl_trait.rs
index 3f15a79271d..083ce022238 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/static_impl_trait.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/static_impl_trait.rs
@@ -1,27 +1,21 @@
 //! Error Reporting for static impl Traits.
 
 use rustc_data_structures::fx::FxIndexSet;
-use rustc_errors::{Applicability, Diag, ErrorGuaranteed, MultiSpan, Subdiagnostic};
+use rustc_errors::{Applicability, Diag, ErrorGuaranteed};
 use rustc_hir::def_id::DefId;
 use rustc_hir::intravisit::{Visitor, VisitorExt, walk_ty};
 use rustc_hir::{
     self as hir, AmbigArg, GenericBound, GenericParam, GenericParamKind, Item, ItemKind, Lifetime,
     LifetimeName, LifetimeParamKind, MissingLifetimeKind, Node, TyKind,
 };
-use rustc_middle::ty::{
-    self, AssocItemContainer, StaticLifetimeVisitor, Ty, TyCtxt, TypeSuperVisitable, TypeVisitor,
-};
+use rustc_middle::ty::{self, Ty, TyCtxt, TypeSuperVisitable, TypeVisitor};
 use rustc_span::def_id::LocalDefId;
 use rustc_span::{Ident, Span};
 use tracing::debug;
 
 use crate::error_reporting::infer::nice_region_error::NiceRegionError;
-use crate::errors::{
-    ButCallingIntroduces, ButNeedsToSatisfy, DynTraitConstraintSuggestion, MoreTargeted,
-    ReqIntroducedLocations,
-};
-use crate::infer::{RegionResolutionError, SubregionOrigin, TypeTrace};
-use crate::traits::{ObligationCauseCode, UnifyReceiverContext};
+use crate::errors::ButNeedsToSatisfy;
+use crate::infer::{RegionResolutionError, SubregionOrigin};
 
 impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
     /// Print the error message for lifetime errors when the return type is a static `impl Trait`,
@@ -39,52 +33,6 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
                 sup_r,
                 spans,
             ) if sub_r.is_static() => (var_origin, sub_origin, sub_r, sup_origin, sup_r, spans),
-            RegionResolutionError::ConcreteFailure(
-                SubregionOrigin::Subtype(box TypeTrace { cause, .. }),
-                sub_r,
-                sup_r,
-            ) if sub_r.is_static() => {
-                // This is for an implicit `'static` requirement coming from `impl dyn Trait {}`.
-                if let ObligationCauseCode::UnifyReceiver(ctxt) = cause.code() {
-                    // This may have a closure and it would cause ICE
-                    // through `find_param_with_region` (#78262).
-                    let anon_reg_sup = tcx.is_suitable_region(self.generic_param_scope, *sup_r)?;
-                    let fn_returns = tcx.return_type_impl_or_dyn_traits(anon_reg_sup.scope);
-                    if fn_returns.is_empty() {
-                        return None;
-                    }
-
-                    let param = self.find_param_with_region(*sup_r, *sub_r)?;
-                    let simple_ident = param.param.pat.simple_ident();
-
-                    let (has_impl_path, impl_path) = match ctxt.assoc_item.container {
-                        AssocItemContainer::Trait => {
-                            let id = ctxt.assoc_item.container_id(tcx);
-                            (true, tcx.def_path_str(id))
-                        }
-                        AssocItemContainer::Impl => (false, String::new()),
-                    };
-
-                    let mut err = self.tcx().dcx().create_err(ButCallingIntroduces {
-                        param_ty_span: param.param_ty_span,
-                        cause_span: cause.span,
-                        has_param_name: simple_ident.is_some(),
-                        param_name: simple_ident.map(|x| x.to_string()).unwrap_or_default(),
-                        has_lifetime: sup_r.has_name(),
-                        lifetime: sup_r.to_string(),
-                        assoc_item: ctxt.assoc_item.name,
-                        has_impl_path,
-                        impl_path,
-                    });
-                    if self.find_impl_on_dyn_trait(&mut err, param.param_ty, ctxt) {
-                        let reported = err.emit();
-                        return Some(reported);
-                    } else {
-                        err.cancel()
-                    }
-                }
-                return None;
-            }
             _ => return None,
         };
         debug!(
@@ -140,39 +88,6 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
             None
         };
 
-        let mut subdiag = None;
-
-        if let SubregionOrigin::Subtype(box TypeTrace { cause, .. }) = sub_origin {
-            if let ObligationCauseCode::ReturnValue(hir_id)
-            | ObligationCauseCode::BlockTailExpression(hir_id, ..) = cause.code()
-            {
-                let parent_id = tcx.hir_get_parent_item(*hir_id);
-                if let Some(fn_decl) = tcx.hir_fn_decl_by_hir_id(parent_id.into()) {
-                    let mut span: MultiSpan = fn_decl.output.span().into();
-                    let mut spans = Vec::new();
-                    let mut add_label = true;
-                    if let hir::FnRetTy::Return(ty) = fn_decl.output {
-                        let mut v = StaticLifetimeVisitor(vec![], tcx.hir());
-                        v.visit_ty_unambig(ty);
-                        if !v.0.is_empty() {
-                            span = v.0.clone().into();
-                            spans = v.0;
-                            add_label = false;
-                        }
-                    }
-                    let fn_decl_span = fn_decl.output.span();
-
-                    subdiag = Some(ReqIntroducedLocations {
-                        span,
-                        spans,
-                        fn_decl_span,
-                        cause_span: cause.span,
-                        add_label,
-                    });
-                }
-            }
-        }
-
         let diag = ButNeedsToSatisfy {
             sp,
             influencer_point,
@@ -183,7 +98,6 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
             require_span_as_note: require_as_note.then_some(require_span),
             // We don't need a note, it's already at the end, it can be shown as a `span_label`.
             require_span_as_label: (!require_as_note).then_some(require_span),
-            req_introduces_loc: subdiag,
 
             has_lifetime: sup_r.has_name(),
             lifetime: lifetime_name.clone(),
@@ -197,45 +111,6 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
 
         let fn_returns = tcx.return_type_impl_or_dyn_traits(anon_reg_sup.scope);
 
-        let mut override_error_code = None;
-        if let SubregionOrigin::Subtype(box TypeTrace { cause, .. }) = &sup_origin
-            && let ObligationCauseCode::UnifyReceiver(ctxt) = cause.code()
-            // Handle case of `impl Foo for dyn Bar { fn qux(&self) {} }` introducing a
-            // `'static` lifetime when called as a method on a binding: `bar.qux()`.
-            && self.find_impl_on_dyn_trait(&mut err, param.param_ty, ctxt)
-        {
-            override_error_code = Some(ctxt.assoc_item.name);
-        }
-
-        if let SubregionOrigin::Subtype(box TypeTrace { cause, .. }) = &sub_origin
-            && let code = match cause.code() {
-                ObligationCauseCode::MatchImpl(parent, ..) => parent.code(),
-                _ => cause.code(),
-            }
-            && let (
-                &ObligationCauseCode::WhereClause(item_def_id, _)
-                | &ObligationCauseCode::WhereClauseInExpr(item_def_id, ..),
-                None,
-            ) = (code, override_error_code)
-        {
-            // Same case of `impl Foo for dyn Bar { fn qux(&self) {} }` introducing a `'static`
-            // lifetime as above, but called using a fully-qualified path to the method:
-            // `Foo::qux(bar)`.
-            let mut v = TraitObjectVisitor(FxIndexSet::default());
-            v.visit_ty(param.param_ty);
-            if let Some((ident, self_ty)) =
-                NiceRegionError::get_impl_ident_and_self_ty_from_trait(tcx, item_def_id, &v.0)
-                && self.suggest_constrain_dyn_trait_in_impl(&mut err, &v.0, ident, self_ty)
-            {
-                override_error_code = Some(ident.name);
-            }
-        }
-        if let (Some(ident), true) = (override_error_code, fn_returns.is_empty()) {
-            // Provide a more targeted error code and description.
-            let retarget_subdiag = MoreTargeted { ident };
-            retarget_subdiag.add_to_diag(&mut err);
-        }
-
         let arg = match param.param.pat.simple_ident() {
             Some(simple_ident) => format!("argument `{simple_ident}`"),
             None => "the argument".to_string(),
@@ -495,8 +370,7 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
                         kind: ItemKind::Impl(hir::Impl { self_ty, .. }), ..
                     }) = tcx.hir_node_by_def_id(impl_did)
                         && trait_objects.iter().all(|did| {
-                            // FIXME: we should check `self_ty` against the receiver
-                            // type in the `UnifyReceiver` context, but for now, use
+                            // FIXME: we should check `self_ty`, but for now, use
                             // this imperfect proxy. This will fail if there are
                             // multiple `impl`s for the same trait like
                             // `impl Foo for Box<dyn Bar>` and `impl Foo for dyn Bar`.
@@ -516,62 +390,6 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
             _ => None,
         }
     }
-
-    /// When we call a method coming from an `impl Foo for dyn Bar`, `dyn Bar` introduces a default
-    /// `'static` obligation. Suggest relaxing that implicit bound.
-    fn find_impl_on_dyn_trait(
-        &self,
-        err: &mut Diag<'_>,
-        ty: Ty<'_>,
-        ctxt: &UnifyReceiverContext<'tcx>,
-    ) -> bool {
-        let tcx = self.tcx();
-
-        // Find the method being called.
-        let Ok(Some(instance)) = ty::Instance::try_resolve(
-            tcx,
-            self.cx.typing_env(ctxt.param_env),
-            ctxt.assoc_item.def_id,
-            self.cx.resolve_vars_if_possible(ctxt.args),
-        ) else {
-            return false;
-        };
-
-        let mut v = TraitObjectVisitor(FxIndexSet::default());
-        v.visit_ty(ty);
-
-        // Get the `Ident` of the method being called and the corresponding `impl` (to point at
-        // `Bar` in `impl Foo for dyn Bar {}` and the definition of the method being called).
-        let Some((ident, self_ty)) =
-            NiceRegionError::get_impl_ident_and_self_ty_from_trait(tcx, instance.def_id(), &v.0)
-        else {
-            return false;
-        };
-
-        // Find the trait object types in the argument, so we point at *only* the trait object.
-        self.suggest_constrain_dyn_trait_in_impl(err, &v.0, ident, self_ty)
-    }
-
-    fn suggest_constrain_dyn_trait_in_impl(
-        &self,
-        err: &mut Diag<'_>,
-        found_dids: &FxIndexSet<DefId>,
-        ident: Ident,
-        self_ty: &hir::Ty<'_>,
-    ) -> bool {
-        let mut suggested = false;
-        for found_did in found_dids {
-            let mut traits = vec![];
-            let mut hir_v = HirTraitObjectVisitor(&mut traits, *found_did);
-            hir_v.visit_ty_unambig(self_ty);
-            for &span in &traits {
-                let subdiag = DynTraitConstraintSuggestion { span, ident };
-                subdiag.add_to_diag(err);
-                suggested = true;
-            }
-        }
-        suggested
-    }
 }
 
 /// Collect all the trait objects in a type that could have received an implicit `'static` lifetime.
diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
index 6eeb47a21f8..496a28cd39f 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs
@@ -2680,7 +2680,6 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
             | ObligationCauseCode::IntrinsicType
             | ObligationCauseCode::MethodReceiver
             | ObligationCauseCode::ReturnNoExpression
-            | ObligationCauseCode::UnifyReceiver(..)
             | ObligationCauseCode::Misc
             | ObligationCauseCode::WellFormed(..)
             | ObligationCauseCode::MatchImpl(..)
diff --git a/compiler/rustc_trait_selection/src/errors.rs b/compiler/rustc_trait_selection/src/errors.rs
index e8d30d3ee79..01a92091fc3 100644
--- a/compiler/rustc_trait_selection/src/errors.rs
+++ b/compiler/rustc_trait_selection/src/errors.rs
@@ -1119,22 +1119,6 @@ impl Subdiagnostic for ReqIntroducedLocations {
     }
 }
 
-pub struct MoreTargeted {
-    pub ident: Symbol,
-}
-
-impl Subdiagnostic for MoreTargeted {
-    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
-        self,
-        diag: &mut Diag<'_, G>,
-        _f: &F,
-    ) {
-        diag.code(E0772);
-        diag.primary_message(fluent::trait_selection_more_targeted);
-        diag.arg("ident", self.ident);
-    }
-}
-
 #[derive(Diagnostic)]
 #[diag(trait_selection_but_needs_to_satisfy, code = E0759)]
 pub struct ButNeedsToSatisfy {
@@ -1151,9 +1135,6 @@ pub struct ButNeedsToSatisfy {
     #[note(trait_selection_introduced_by_bound)]
     pub bound: Option<Span>,
 
-    #[subdiagnostic]
-    pub req_introduces_loc: Option<ReqIntroducedLocations>,
-
     pub has_param_name: bool,
     pub param_name: String,
     pub spans_empty: bool,