Rollup merge of rust-lang#131968 - compiler-errors:old-effect-handling, r=fee1-dead

Rip out old effects var handling code from traits

Traits no longer have an effect parameter, so this removes logic associated with it. It also removes logic surrounding confirming `~const Destruct` bounds, which I added a looooong time ago, and which I don't feel like we need anymore -- if it needs to be added back, it should be rewritten :D

cc `@fee1-dead`

Author: matthiaskrgr

compiler/rustc_const_eval/src/check_consts/qualifs.rs

@@ -6,13 +6,10 @@ use rustc_errors::ErrorGuaranteed;
 use rustc_hir::LangItem;
 use rustc_infer::infer::TyCtxtInferExt;
 use rustc_middle::mir::*;
-use rustc_middle::traits::BuiltinImplSource;
 use rustc_middle::ty::{self, AdtDef, GenericArgsRef, Ty};
 use rustc_middle::{bug, mir};
-use rustc_trait_selection::traits::{
-    ImplSource, Obligation, ObligationCause, ObligationCtxt, SelectionContext,
-};
-use tracing::{instrument, trace};
+use rustc_trait_selection::traits::{Obligation, ObligationCause, ObligationCtxt};
+use tracing::instrument;
 
 use super::ConstCx;
 
@@ -195,50 +192,8 @@ impl Qualif for NeedsNonConstDrop {
             return false;
         }
 
-        // FIXME(effects): If `destruct` is not a `const_trait`,
-        // or effects are disabled in this crate, then give up.
-        let destruct_def_id = cx.tcx.require_lang_item(LangItem::Destruct, Some(cx.body.span));
-        if !cx.tcx.has_host_param(destruct_def_id) || !cx.tcx.features().effects {
-            return NeedsDrop::in_any_value_of_ty(cx, ty);
-        }
-
-        let obligation = Obligation::new(
-            cx.tcx,
-            ObligationCause::dummy_with_span(cx.body.span),
-            cx.param_env,
-            ty::TraitRef::new(cx.tcx, destruct_def_id, [
-                ty::GenericArg::from(ty),
-                ty::GenericArg::from(cx.tcx.expected_host_effect_param_for_body(cx.def_id())),
-            ]),
-        );
-
-        let infcx = cx.tcx.infer_ctxt().build();
-        let mut selcx = SelectionContext::new(&infcx);
-        let Some(impl_src) = selcx.select(&obligation).ok().flatten() else {
-            // If we couldn't select a const destruct candidate, then it's bad
-            return true;
-        };
-
-        trace!(?impl_src);
-
-        if !matches!(
-            impl_src,
-            ImplSource::Builtin(BuiltinImplSource::Misc, _) | ImplSource::Param(_)
-        ) {
-            // If our const destruct candidate is not ConstDestruct or implied by the param env,
-            // then it's bad
-            return true;
-        }
-
-        if impl_src.borrow_nested_obligations().is_empty() {
-            return false;
-        }
-
-        // If we had any errors, then it's bad
-        let ocx = ObligationCtxt::new(&infcx);
-        ocx.register_obligations(impl_src.nested_obligations());
-        let errors = ocx.select_all_or_error();
-        !errors.is_empty()
+        // FIXME(effects): Reimplement const drop checking.
+        NeedsDrop::in_any_value_of_ty(cx, ty)
     }
 
     fn in_adt_inherently<'tcx>(

compiler/rustc_hir_typeck/src/callee.rs

@@ -537,40 +537,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 //
                 // This check is here because there is currently no way to express a trait bound for `FnDef` types only.
                 if let ty::FnDef(def_id, _args) = *arg_ty.kind() {
-                    let fn_once_def_id =
-                        self.tcx.require_lang_item(hir::LangItem::FnOnce, Some(span));
-                    let fn_once_output_def_id =
-                        self.tcx.require_lang_item(hir::LangItem::FnOnceOutput, Some(span));
-                    if self.tcx.has_host_param(fn_once_def_id) {
-                        let const_param: ty::GenericArg<'tcx> =
-                            ([self.tcx.consts.false_, self.tcx.consts.true_])[idx].into();
-                        self.register_predicate(traits::Obligation::new(
-                            self.tcx,
-                            self.misc(span),
-                            self.param_env,
-                            ty::TraitRef::new(self.tcx, fn_once_def_id, [
-                                arg_ty.into(),
-                                fn_sig.inputs()[0].into(),
-                                const_param,
-                            ]),
-                        ));
-
-                        self.register_predicate(traits::Obligation::new(
-                            self.tcx,
-                            self.misc(span),
-                            self.param_env,
-                            ty::ProjectionPredicate {
-                                projection_term: ty::AliasTerm::new(
-                                    self.tcx,
-                                    fn_once_output_def_id,
-                                    [arg_ty.into(), fn_sig.inputs()[0].into(), const_param],
-                                ),
-                                term: fn_sig.output().into(),
-                            },
-                        ));
-
-                        self.select_obligations_where_possible(|_| {});
-                    } else if idx == 0 && !self.tcx.is_const_fn_raw(def_id) {
+                    if idx == 0 && !self.tcx.is_const_fn_raw(def_id) {
                         self.dcx().emit_err(errors::ConstSelectMustBeConst { span });
                     }
                 } else {

compiler/rustc_middle/src/traits/select.rs

@@ -161,9 +161,7 @@ pub enum SelectionCandidate<'tcx> {
 
     /// Implementation of a `Fn`-family trait by one of the anonymous
     /// types generated for a fn pointer type (e.g., `fn(int) -> int`)
-    FnPointerCandidate {
-        fn_host_effect: ty::Const<'tcx>,
-    },
+    FnPointerCandidate,
 
     TraitAliasCandidate,
 
@@ -180,9 +178,6 @@ pub enum SelectionCandidate<'tcx> {
     BuiltinObjectCandidate,
 
     BuiltinUnsizeCandidate,
-
-    /// Implementation of `const Destruct`, optionally from a custom `impl const Drop`.
-    ConstDestructCandidate(Option<DefId>),
 }
 
 /// The result of trait evaluation. The order is important

compiler/rustc_middle/src/ty/util.rs

@@ -907,24 +907,6 @@ impl<'tcx> TyCtxt<'tcx> {
         }
     }
 
-    /// Constructs generic args for an item, optionally appending a const effect param type
-    pub fn with_opt_host_effect_param(
-        self,
-        caller_def_id: LocalDefId,
-        callee_def_id: DefId,
-        args: impl IntoIterator<Item: Into<ty::GenericArg<'tcx>>>,
-    ) -> ty::GenericArgsRef<'tcx> {
-        let generics = self.generics_of(callee_def_id);
-        assert_eq!(generics.parent, None);
-
-        let opt_const_param = generics
-            .host_effect_index
-            .is_some()
-            .then(|| ty::GenericArg::from(self.expected_host_effect_param_for_body(caller_def_id)));
-
-        self.mk_args_from_iter(args.into_iter().map(|arg| arg.into()).chain(opt_const_param))
-    }
-
     /// Expand any [weak alias types][weak] contained within the given `value`.
     ///
     /// This should be used over other normalization routines in situations where

compiler/rustc_mir_build/src/build/matches/test.rs

@@ -454,12 +454,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         };
 
         let eq_def_id = self.tcx.require_lang_item(LangItem::PartialEq, Some(source_info.span));
-        let method = trait_method(
-            self.tcx,
-            eq_def_id,
-            sym::eq,
-            self.tcx.with_opt_host_effect_param(self.def_id, eq_def_id, [compare_ty, compare_ty]),
-        );
+        let method = trait_method(self.tcx, eq_def_id, sym::eq, [compare_ty, compare_ty]);
 
         let bool_ty = self.tcx.types.bool;
         let eq_result = self.temp(bool_ty, source_info.span);

compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs

@@ -43,7 +43,6 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
 }
 
 struct ConstToPat<'tcx> {
-    id: hir::HirId,
     span: Span,
     param_env: ty::ParamEnv<'tcx>,
 
@@ -62,7 +61,6 @@ impl<'tcx> ConstToPat<'tcx> {
     ) -> Self {
         trace!(?pat_ctxt.typeck_results.hir_owner);
         ConstToPat {
-            id,
             span,
             infcx,
             param_env: pat_ctxt.param_env,
@@ -149,15 +147,7 @@ impl<'tcx> ConstToPat<'tcx> {
             tcx,
             ObligationCause::dummy(),
             self.param_env,
-            ty::TraitRef::new_from_args(
-                tcx,
-                partial_eq_trait_id,
-                tcx.with_opt_host_effect_param(
-                    tcx.hir().enclosing_body_owner(self.id),
-                    partial_eq_trait_id,
-                    [ty, ty],
-                ),
-            ),
+            ty::TraitRef::new(tcx, partial_eq_trait_id, [ty, ty]),
         );
 
         // This *could* accept a type that isn't actually `PartialEq`, because region bounds get

compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs

@@ -3701,12 +3701,10 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                         }
                         _ => 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).chain(host),
+                            [field_ty].into_iter().chain(trait_args),
                         ),
                         ..*tr
                     });

compiler/rustc_trait_selection/src/traits/project.rs

@@ -1642,24 +1642,9 @@ fn confirm_fn_pointer_candidate<'cx, 'tcx>(
         sig,
     );
 
-    let host_effect_param = match *fn_type.kind() {
-        ty::FnDef(def_id, args) => tcx
-            .generics_of(def_id)
-            .host_effect_index
-            .map_or(tcx.consts.true_, |idx| args.const_at(idx)),
-        ty::FnPtr(..) => tcx.consts.true_,
-        _ => unreachable!("only expected FnPtr or FnDef in `confirm_fn_pointer_candidate`"),
-    };
-
-    confirm_callable_candidate(
-        selcx,
-        obligation,
-        sig,
-        util::TupleArgumentsFlag::Yes,
-        host_effect_param,
-    )
-    .with_addl_obligations(nested)
-    .with_addl_obligations(obligations)
+    confirm_callable_candidate(selcx, obligation, sig, util::TupleArgumentsFlag::Yes)
+        .with_addl_obligations(nested)
+        .with_addl_obligations(obligations)
 }
 
 fn confirm_closure_candidate<'cx, 'tcx>(
@@ -1739,24 +1724,16 @@ fn confirm_closure_candidate<'cx, 'tcx>(
 
     debug!(?obligation, ?closure_sig, ?obligations, "confirm_closure_candidate");
 
-    confirm_callable_candidate(
-        selcx,
-        obligation,
-        closure_sig,
-        util::TupleArgumentsFlag::No,
-        // FIXME(effects): This doesn't handle const closures correctly!
-        selcx.tcx().consts.true_,
-    )
-    .with_addl_obligations(nested)
-    .with_addl_obligations(obligations)
+    confirm_callable_candidate(selcx, obligation, closure_sig, util::TupleArgumentsFlag::No)
+        .with_addl_obligations(nested)
+        .with_addl_obligations(obligations)
 }
 
 fn confirm_callable_candidate<'cx, 'tcx>(
     selcx: &mut SelectionContext<'cx, 'tcx>,
     obligation: &ProjectionTermObligation<'tcx>,
     fn_sig: ty::PolyFnSig<'tcx>,
     flag: util::TupleArgumentsFlag,
-    fn_host_effect: ty::Const<'tcx>,
 ) -> Progress<'tcx> {
     let tcx = selcx.tcx();
 
@@ -1771,7 +1748,6 @@ fn confirm_callable_candidate<'cx, 'tcx>(
         obligation.predicate.self_ty(),
         fn_sig,
         flag,
-        fn_host_effect,
     )
     .map_bound(|(trait_ref, ret_type)| ty::ProjectionPredicate {
         projection_term: ty::AliasTerm::new_from_args(tcx, fn_once_output_def_id, trait_ref.args),