Auto merge of rust-lang#132479 - compiler-errors:fx-feat-yeet, r=fee1-dead

Yeet the `effects` feature, move it onto `const_trait_impl`

This PR merges the `effects` feature into the `const_trait_impl` feature. There's really no need to have two feature gates for one feature.

After this PR, if `const_trait_impl` **is** enabled:
* Users can use and define const traits
* `HostEffect` const conditions will be enforced on the HIR
* We re-check the predicates in MIR just to make sure that we don't "leak" anything during MIR lowering

And if `const_trait_impl` **is not** enabled:
* Users cannot use nor define const traits
* `HostEffect` const conditions are not enforced on the HIR
* We will raise a const validation error if we call a function that has any const conditions (i.e. const traits and functions with any `~const` in their where clasues)

This should be the last step for us to be able to enable const traits in the standard library. We still need to re-constify `Drop` and `Destruct` and stuff for const traits to be particularly *useful* for some cases, but this is a good step :D

r? fee1-dead
cc `@rust-lang/project-const-traits`

Author: bors

compiler/rustc_ast_passes/src/errors.rs

@@ -594,8 +594,8 @@ pub(crate) struct ConstBoundTraitObject {
     pub span: Span,
 }
 
-// FIXME(effects): Consider making the note/reason the message of the diagnostic.
-// FIXME(effects): Provide structured suggestions (e.g., add `const` / `#[const_trait]` here).
+// FIXME(const_trait_impl): Consider making the note/reason the message of the diagnostic.
+// FIXME(const_trait_impl): Provide structured suggestions (e.g., add `const` / `#[const_trait]` here).
 #[derive(Diagnostic)]
 #[diag(ast_passes_tilde_const_disallowed)]
 pub(crate) struct TildeConstDisallowed {

compiler/rustc_const_eval/src/check_consts/check.rs

@@ -20,7 +20,6 @@ use rustc_mir_dataflow::Analysis;
 use rustc_mir_dataflow::impls::MaybeStorageLive;
 use rustc_mir_dataflow::storage::always_storage_live_locals;
 use rustc_span::{Span, Symbol, sym};
-use rustc_trait_selection::error_reporting::InferCtxtErrorExt;
 use rustc_trait_selection::traits::{
     Obligation, ObligationCause, ObligationCauseCode, ObligationCtxt,
 };
@@ -419,13 +418,8 @@ impl<'mir, 'tcx> Checker<'mir, 'tcx> {
 
         let errors = ocx.select_all_or_error();
         if !errors.is_empty() {
-            // FIXME(effects): Soon this should be unconditionally delaying a bug.
-            if matches!(call_source, CallSource::Normal) && tcx.features().effects() {
-                tcx.dcx()
-                    .span_delayed_bug(call_span, "this should have reported a ~const error in HIR");
-            } else {
-                infcx.err_ctxt().report_fulfillment_errors(errors);
-            }
+            tcx.dcx()
+                .span_delayed_bug(call_span, "this should have reported a ~const error in HIR");
         }
     }
 }
@@ -663,8 +657,9 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                     // typeck ensures the conditions for calling a const trait method are met,
                     // so we only error if the trait isn't const. We try to resolve the trait
                     // into the concrete method, and uses that for const stability checks.
-                    // FIXME(effects) we might consider moving const stability checks to typeck as well.
-                    if tcx.features().effects() && trait_is_const {
+                    // FIXME(const_trait_impl) we might consider moving const stability checks
+                    // to typeck as well.
+                    if tcx.features().const_trait_impl() && trait_is_const {
                         // This skips the check below that ensures we only call `const fn`.
                         is_trait = true;
 

compiler/rustc_const_eval/src/check_consts/ops.rs

@@ -120,7 +120,7 @@ impl<'tcx> NonConstOp<'tcx> for FnCallNonConst<'tcx> {
                     let implsrc = selcx.select(&obligation);
 
                     if let Ok(Some(ImplSource::UserDefined(data))) = implsrc {
-                        // FIXME(effects) revisit this
+                        // FIXME(const_trait_impl) revisit this
                         if !tcx.is_const_trait_impl(data.impl_def_id) {
                             let span = tcx.def_span(data.impl_def_id);
                             err.subdiagnostic(errors::NonConstImplNote { span });

compiler/rustc_const_eval/src/check_consts/qualifs.rs

@@ -192,7 +192,7 @@ impl Qualif for NeedsNonConstDrop {
             return false;
         }
 
-        // FIXME(effects): Reimplement const drop checking.
+        // FIXME(const_trait_impl): Reimplement const drop checking.
         NeedsDrop::in_any_value_of_ty(cx, ty)
     }
 

compiler/rustc_const_eval/src/const_eval/machine.rs

@@ -431,7 +431,7 @@ impl<'tcx> interpret::Machine<'tcx> for CompileTimeMachine<'tcx> {
             // sensitive check here. But we can at least rule out functions that are not const at
             // all. That said, we have to allow calling functions inside a trait marked with
             // #[const_trait]. These *are* const-checked!
-            // FIXME(effects): why does `is_const_fn` not classify them as const?
+            // FIXME(const_trait_impl): why does `is_const_fn` not classify them as const?
             if (!ecx.tcx.is_const_fn(def) && !ecx.tcx.is_const_default_method(def))
                 || ecx.tcx.has_attr(def, sym::rustc_do_not_const_check)
             {

compiler/rustc_feature/src/removed.rs

@@ -100,6 +100,9 @@ declare_features! (
      Some("renamed to `doc_notable_trait`")),
     /// Allows using `#[unsafe_destructor_blind_to_params]` (RFC 1238).
     (removed, dropck_parametricity, "1.38.0", Some(28498), None),
+    /// Uses generic effect parameters for ~const bounds
+    (removed, effects, "CURRENT_RUSTC_VERSION", Some(102090),
+     Some("removed, redundant with `#![feature(const_trait_impl)]`")),
     /// Allows defining `existential type`s.
     (removed, existential_type, "1.38.0", Some(63063),
      Some("removed in favor of `#![feature(type_alias_impl_trait)]`")),

compiler/rustc_feature/src/unstable.rs

@@ -462,8 +462,6 @@ declare_features! (
     (unstable, doc_masked, "1.21.0", Some(44027)),
     /// Allows `dyn* Trait` objects.
     (incomplete, dyn_star, "1.65.0", Some(102425)),
-    /// Uses generic effect parameters for ~const bounds
-    (incomplete, effects, "1.72.0", Some(102090)),
     /// Allows exhaustive pattern matching on types that contain uninhabited types.
     (unstable, exhaustive_patterns, "1.13.0", Some(51085)),
     /// Allows explicit tail calls via `become` expression.

compiler/rustc_hir_analysis/src/check/compare_impl_item.rs

@@ -205,7 +205,6 @@ fn compare_method_predicate_entailment<'tcx>(
         trait_m_predicates.instantiate_own(tcx, trait_to_impl_args).map(|(predicate, _)| predicate),
     );
 
-    // FIXME(effects): This should be replaced with a more dedicated method.
     let is_conditionally_const = tcx.is_conditionally_const(impl_def_id);
     if is_conditionally_const {
         // Augment the hybrid param-env with the const conditions

compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs

@@ -563,7 +563,6 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
                         if let Err(guar) = ty.error_reported() {
                             return ty::Const::new_error(tcx, guar).into();
                         }
-                        // FIXME(effects) see if we should special case effect params here
                         if !infer_args && has_default {
                             tcx.const_param_default(param.def_id)
                                 .instantiate(tcx, preceding_args)

compiler/rustc_hir_analysis/src/impl_wf_check/min_specialization.rs

@@ -459,7 +459,7 @@ fn trait_predicates_eq<'tcx>(
     predicate1: ty::Predicate<'tcx>,
     predicate2: ty::Predicate<'tcx>,
 ) -> bool {
-    // FIXME(effects)
+    // FIXME(const_trait_impl)
     predicate1 == predicate2
 }