Auto merge of rust-lang#122712 - matthiaskrgr:rollup-xup9a3i, r=matth…

…iaskrgr

Rollup of 12 pull requests

Successful merges:

 - rust-lang#121258 (Reject overly generic assoc const binding types)
 - rust-lang#121823 (never patterns: suggest `!` patterns on non-exhaustive matches)
 - rust-lang#122060 (Stabilize `imported_main`)
 - rust-lang#122158 (Provide structured suggestion for `#![feature(foo)]`)
 - rust-lang#122642 (Improve wording of `Vec::swap_remove`)
 - rust-lang#122675 (core: document default attribute stabilization)
 - rust-lang#122687 (`NormalizesTo`: return nested goals to caller)
 - rust-lang#122691 (Fix ICE: `global_asm!()` Don't Panic When Unable to Evaluate Constant)
 - rust-lang#122693 (Fix heading anchors in doc pages.)
 - rust-lang#122699 (Fix a typo in the 1.77.0 relnotes)
 - rust-lang#122700 (Remove redundant files, rename base riscv32 file)
 - rust-lang#122701 (Detect allocator for box in `must_not_suspend` lint)

r? `@ghost`
`@rustbot` modify labels: rollup

RELEASES.md

@@ -82,7 +82,7 @@ Cargo
 
 - [Extend the build directive syntax with `cargo::`.](https://github.com/rust-lang/cargo/pull/12201/)
 - [Stabilize metadata `id` format as `PackageIDSpec`.](https://github.com/rust-lang/cargo/pull/12914/)
-- [Pull out as `cargo-util-schemas` as a crate.](https://github.com/rust-lang/cargo/pull/13178/)
+- [Pull out `cargo-util-schemas` as a crate.](https://github.com/rust-lang/cargo/pull/13178/)
 - [Strip all debuginfo when debuginfo is not requested.](https://github.com/rust-lang/cargo/pull/13257/)
 - [Inherit jobserver from env for all kinds of runners.](https://github.com/rust-lang/cargo/pull/12776/)
 - [Deprecate rustc plugin support in cargo.](https://github.com/rust-lang/cargo/pull/13248/)

compiler/rustc_codegen_ssa/src/mono_item.rs

@@ -2,6 +2,7 @@ use crate::base;
 use crate::common;
 use crate::traits::*;
 use rustc_hir as hir;
+use rustc_middle::mir::interpret::ErrorHandled;
 use rustc_middle::mir::mono::MonoItem;
 use rustc_middle::mir::mono::{Linkage, Visibility};
 use rustc_middle::ty;
@@ -40,23 +41,34 @@ impl<'a, 'tcx: 'a> MonoItemExt<'a, 'tcx> for MonoItem<'tcx> {
                         .iter()
                         .map(|(op, op_sp)| match *op {
                             hir::InlineAsmOperand::Const { ref anon_const } => {
-                                let const_value = cx
-                                    .tcx()
-                                    .const_eval_poly(anon_const.def_id.to_def_id())
-                                    .unwrap_or_else(|_| {
-                                        span_bug!(*op_sp, "asm const cannot be resolved")
-                                    });
-                                let ty = cx
-                                    .tcx()
-                                    .typeck_body(anon_const.body)
-                                    .node_type(anon_const.hir_id);
-                                let string = common::asm_const_to_str(
-                                    cx.tcx(),
-                                    *op_sp,
-                                    const_value,
-                                    cx.layout_of(ty),
-                                );
-                                GlobalAsmOperandRef::Const { string }
+                                match cx.tcx().const_eval_poly(anon_const.def_id.to_def_id()) {
+                                    Ok(const_value) => {
+                                        let ty = cx
+                                            .tcx()
+                                            .typeck_body(anon_const.body)
+                                            .node_type(anon_const.hir_id);
+                                        let string = common::asm_const_to_str(
+                                            cx.tcx(),
+                                            *op_sp,
+                                            const_value,
+                                            cx.layout_of(ty),
+                                        );
+                                        GlobalAsmOperandRef::Const { string }
+                                    }
+                                    Err(ErrorHandled::Reported { .. }) => {
+                                        // An error has already been reported and
+                                        // compilation is guaranteed to fail if execution
+                                        // hits this path. So an empty string instead of
+                                        // a stringified constant value will suffice.
+                                        GlobalAsmOperandRef::Const { string: String::new() }
+                                    }
+                                    Err(ErrorHandled::TooGeneric(_)) => {
+                                        span_bug!(
+                                            *op_sp,
+                                            "asm const cannot be resolved; too generic"
+                                        )
+                                    }
+                                }
                             }
                             hir::InlineAsmOperand::SymFn { ref anon_const } => {
                                 let ty = cx

compiler/rustc_const_eval/src/transform/check_consts/ops.rs

@@ -99,7 +99,7 @@ impl<'tcx> NonConstOp<'tcx> for FnCallNonConst<'tcx> {
     #[allow(rustc::untranslatable_diagnostic)]
     fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, _: Span) -> Diag<'tcx> {
         let FnCallNonConst { caller, callee, args, span, call_source, feature } = *self;
-        let ConstCx { tcx, param_env, .. } = *ccx;
+        let ConstCx { tcx, param_env, body, .. } = *ccx;
 
         let diag_trait = |err, self_ty: Ty<'_>, trait_id| {
             let trait_ref = TraitRef::from_method(tcx, trait_id, args);
@@ -297,10 +297,12 @@ impl<'tcx> NonConstOp<'tcx> for FnCallNonConst<'tcx> {
             ccx.const_kind(),
         ));
 
-        if let Some(feature) = feature
-            && ccx.tcx.sess.is_nightly_build()
-        {
-            err.help(format!("add `#![feature({feature})]` to the crate attributes to enable",));
+        if let Some(feature) = feature {
+            ccx.tcx.disabled_nightly_features(
+                &mut err,
+                body.source.def_id().as_local().map(|local| ccx.tcx.local_def_id_to_hir_id(local)),
+                [(String::new(), feature)],
+            );
         }
 
         if let ConstContext::Static(_) = ccx.const_kind() {

compiler/rustc_feature/src/accepted.rs

@@ -203,6 +203,8 @@ declare_features! (
     (accepted, impl_header_lifetime_elision, "1.31.0", Some(15872)),
     /// Allows referencing `Self` and projections in impl-trait.
     (accepted, impl_trait_projections, "1.74.0", Some(103532)),
+    /// Allows using imported `main` function
+    (accepted, imported_main, "CURRENT_RUSTC_VERSION", Some(28937)),
     /// Allows using `a..=b` and `..=b` as inclusive range syntaxes.
     (accepted, inclusive_range_syntax, "1.26.0", Some(28237)),
     /// Allows inferring outlives requirements (RFC 2093).

compiler/rustc_feature/src/unstable.rs

@@ -495,8 +495,6 @@ declare_features! (
     (unstable, impl_trait_in_assoc_type, "1.70.0", Some(63063)),
     /// Allows `impl Trait` as output type in `Fn` traits in return position of functions.
     (unstable, impl_trait_in_fn_trait_return, "1.64.0", Some(99697)),
-    /// Allows using imported `main` function
-    (unstable, imported_main, "1.53.0", Some(28937)),
     /// Allows associated types in inherent impls.
     (incomplete, inherent_associated_types, "1.52.0", Some(8995)),
     /// Allow anonymous constants from an inline `const` block

compiler/rustc_hir_analysis/messages.ftl

@@ -118,6 +118,11 @@ hir_analysis_enum_discriminant_overflowed = enum discriminant overflowed
     .label = overflowed on value after {$discr}
     .note = explicitly set `{$item_name} = {$wrapped_discr}` if that is desired outcome
 
+hir_analysis_escaping_bound_var_in_ty_of_assoc_const_binding =
+    the type of the associated constant `{$assoc_const}` cannot capture late-bound generic parameters
+    .label = its type cannot capture the late-bound {$var_def_kind} `{$var_name}`
+    .var_defined_here_label = the late-bound {$var_def_kind} `{$var_name}` is defined here
+
 hir_analysis_field_already_declared =
     field `{$field_name}` is already declared
     .label = field already declared
@@ -316,6 +321,22 @@ hir_analysis_opaque_captures_higher_ranked_lifetime = `impl Trait` cannot captur
     .label = `impl Trait` implicitly captures all lifetimes in scope
     .note = lifetime declared here
 
+hir_analysis_param_in_ty_of_assoc_const_binding =
+    the type of the associated constant `{$assoc_const}` must not depend on {$param_category ->
+        [self] `Self`
+        [synthetic] `impl Trait`
+        *[normal] generic parameters
+    }
+    .label = its type must not depend on {$param_category ->
+        [self] `Self`
+        [synthetic] `impl Trait`
+        *[normal] the {$param_def_kind} `{$param_name}`
+    }
+    .param_defined_here_label = {$param_category ->
+        [synthetic] the `impl Trait` is specified here
+        *[normal] the {$param_def_kind} `{$param_name}` is defined here
+    }
+
 hir_analysis_paren_sugar_attribute = the `#[rustc_paren_sugar]` attribute is a temporary means of controlling which traits can use parenthetical notation
     .help = add `#![feature(unboxed_closures)]` to the crate attributes to use it
 
@@ -432,6 +453,8 @@ hir_analysis_transparent_non_zero_sized_enum = the variant of a transparent {$de
     .label = needs at most one field with non-trivial size or alignment, but has {$field_count}
     .labels = this field has non-zero size or requires alignment
 
+hir_analysis_ty_of_assoc_const_binding_note = `{$assoc_const}` has type `{$ty}`
+
 hir_analysis_ty_param_first_local = type parameter `{$param_ty}` must be covered by another type when it appears before the first local type (`{$local_type}`)
     .label = type parameter `{$param_ty}` must be covered by another type when it appears before the first local type (`{$local_type}`)
     .note = implementing a foreign trait is only possible if at least one of the types for which it is implemented is local, and no uncovered type parameters appear before that first local type

compiler/rustc_hir_analysis/src/astconv/bounds.rs

@@ -1,12 +1,15 @@
-use rustc_data_structures::fx::FxIndexMap;
+use std::ops::ControlFlow;
+
+use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_errors::{codes::*, struct_span_code_err};
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::{DefId, LocalDefId};
-use rustc_middle::ty::{self as ty, Ty};
+use rustc_middle::ty::{self as ty, IsSuggestable, Ty, TyCtxt};
 use rustc_span::symbol::Ident;
-use rustc_span::{ErrorGuaranteed, Span};
+use rustc_span::{ErrorGuaranteed, Span, Symbol};
 use rustc_trait_selection::traits;
+use rustc_type_ir::visit::{TypeSuperVisitable, TypeVisitable, TypeVisitableExt, TypeVisitor};
 use smallvec::SmallVec;
 
 use crate::astconv::{AstConv, OnlySelfBounds, PredicateFilter};
@@ -433,14 +436,8 @@ impl<'tcx> dyn AstConv<'tcx> + '_ {
                 binding.kind
             {
                 let ty = alias_ty.map_bound(|ty| tcx.type_of(ty.def_id).instantiate(tcx, ty.args));
-                // Since the arguments passed to the alias type above may contain early-bound
-                // generic parameters, the instantiated type may contain some as well.
-                // Therefore wrap it in `EarlyBinder`.
-                // FIXME(fmease): Reject escaping late-bound vars.
-                tcx.feed_anon_const_type(
-                    anon_const.def_id,
-                    ty::EarlyBinder::bind(ty.skip_binder()),
-                );
+                let ty = check_assoc_const_binding_type(tcx, assoc_ident, ty, binding.hir_id);
+                tcx.feed_anon_const_type(anon_const.def_id, ty::EarlyBinder::bind(ty));
             }
 
             alias_ty
@@ -530,3 +527,167 @@ impl<'tcx> dyn AstConv<'tcx> + '_ {
         Ok(())
     }
 }
+
+/// Detect and reject early-bound & escaping late-bound generic params in the type of assoc const bindings.
+///
+/// FIXME(const_generics): This is a temporary and semi-artifical restriction until the
+/// arrival of *generic const generics*[^1].
+///
+/// It might actually be possible that we can already support early-bound generic params
+/// in such types if we just lifted some more checks in other places, too, for example
+/// inside [`ty::Const::from_anon_const`]. However, even if that were the case, we should
+/// probably gate this behind another feature flag.
+///
+/// [^1]: <https://github.com/rust-lang/project-const-generics/issues/28>.
+fn check_assoc_const_binding_type<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    assoc_const: Ident,
+    ty: ty::Binder<'tcx, Ty<'tcx>>,
+    hir_id: hir::HirId,
+) -> Ty<'tcx> {
+    // We can't perform the checks for early-bound params during name resolution unlike E0770
+    // because this information depends on *type* resolution.
+    // We can't perform these checks in `resolve_bound_vars` either for the same reason.
+    // Consider the trait ref `for<'a> Trait<'a, C = { &0 }>`. We need to know the fully
+    // resolved type of `Trait::C` in order to know if it references `'a` or not.
+
+    let ty = ty.skip_binder();
+    if !ty.has_param() && !ty.has_escaping_bound_vars() {
+        return ty;
+    }
+
+    let mut collector = GenericParamAndBoundVarCollector {
+        tcx,
+        params: Default::default(),
+        vars: Default::default(),
+        depth: ty::INNERMOST,
+    };
+    let mut guar = ty.visit_with(&mut collector).break_value();
+
+    let ty_note = ty
+        .make_suggestable(tcx, false)
+        .map(|ty| crate::errors::TyOfAssocConstBindingNote { assoc_const, ty });
+
+    let enclosing_item_owner_id = tcx
+        .hir()
+        .parent_owner_iter(hir_id)
+        .find_map(|(owner_id, parent)| parent.generics().map(|_| owner_id))
+        .unwrap();
+    let generics = tcx.generics_of(enclosing_item_owner_id);
+    for index in collector.params {
+        let param = generics.param_at(index as _, tcx);
+        let is_self_param = param.name == rustc_span::symbol::kw::SelfUpper;
+        guar.get_or_insert(tcx.dcx().emit_err(crate::errors::ParamInTyOfAssocConstBinding {
+            span: assoc_const.span,
+            assoc_const,
+            param_name: param.name,
+            param_def_kind: tcx.def_descr(param.def_id),
+            param_category: if is_self_param {
+                "self"
+            } else if param.kind.is_synthetic() {
+                "synthetic"
+            } else {
+                "normal"
+            },
+            param_defined_here_label:
+                (!is_self_param).then(|| tcx.def_ident_span(param.def_id).unwrap()),
+            ty_note,
+        }));
+    }
+    for (var_def_id, var_name) in collector.vars {
+        guar.get_or_insert(tcx.dcx().emit_err(
+            crate::errors::EscapingBoundVarInTyOfAssocConstBinding {
+                span: assoc_const.span,
+                assoc_const,
+                var_name,
+                var_def_kind: tcx.def_descr(var_def_id),
+                var_defined_here_label: tcx.def_ident_span(var_def_id).unwrap(),
+                ty_note,
+            },
+        ));
+    }
+
+    let guar = guar.unwrap_or_else(|| bug!("failed to find gen params or bound vars in ty"));
+    Ty::new_error(tcx, guar)
+}
+
+struct GenericParamAndBoundVarCollector<'tcx> {
+    tcx: TyCtxt<'tcx>,
+    params: FxIndexSet<u32>,
+    vars: FxIndexSet<(DefId, Symbol)>,
+    depth: ty::DebruijnIndex,
+}
+
+impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for GenericParamAndBoundVarCollector<'tcx> {
+    type Result = ControlFlow<ErrorGuaranteed>;
+
+    fn visit_binder<T: TypeVisitable<TyCtxt<'tcx>>>(
+        &mut self,
+        binder: &ty::Binder<'tcx, T>,
+    ) -> Self::Result {
+        self.depth.shift_in(1);
+        let result = binder.super_visit_with(self);
+        self.depth.shift_out(1);
+        result
+    }
+
+    fn visit_ty(&mut self, ty: Ty<'tcx>) -> Self::Result {
+        match ty.kind() {
+            ty::Param(param) => {
+                self.params.insert(param.index);
+            }
+            ty::Bound(db, bt) if *db >= self.depth => {
+                self.vars.insert(match bt.kind {
+                    ty::BoundTyKind::Param(def_id, name) => (def_id, name),
+                    ty::BoundTyKind::Anon => {
+                        let reported = self
+                            .tcx
+                            .dcx()
+                            .delayed_bug(format!("unexpected anon bound ty: {:?}", bt.var));
+                        return ControlFlow::Break(reported);
+                    }
+                });
+            }
+            _ if ty.has_param() || ty.has_bound_vars() => return ty.super_visit_with(self),
+            _ => {}
+        }
+        ControlFlow::Continue(())
+    }
+
+    fn visit_region(&mut self, re: ty::Region<'tcx>) -> Self::Result {
+        match re.kind() {
+            ty::ReEarlyParam(param) => {
+                self.params.insert(param.index);
+            }
+            ty::ReBound(db, br) if db >= self.depth => {
+                self.vars.insert(match br.kind {
+                    ty::BrNamed(def_id, name) => (def_id, name),
+                    ty::BrAnon | ty::BrEnv => {
+                        let guar = self
+                            .tcx
+                            .dcx()
+                            .delayed_bug(format!("unexpected bound region kind: {:?}", br.kind));
+                        return ControlFlow::Break(guar);
+                    }
+                });
+            }
+            _ => {}
+        }
+        ControlFlow::Continue(())
+    }
+
+    fn visit_const(&mut self, ct: ty::Const<'tcx>) -> Self::Result {
+        match ct.kind() {
+            ty::ConstKind::Param(param) => {
+                self.params.insert(param.index);
+            }
+            ty::ConstKind::Bound(db, ty::BoundVar { .. }) if db >= self.depth => {
+                let guar = self.tcx.dcx().delayed_bug("unexpected escaping late-bound const var");
+                return ControlFlow::Break(guar);
+            }
+            _ if ct.has_param() || ct.has_bound_vars() => return ct.super_visit_with(self),
+            _ => {}
+        }
+        ControlFlow::Continue(())
+    }
+}

compiler/rustc_hir_analysis/src/astconv/generics.rs

@@ -16,7 +16,7 @@ use rustc_middle::ty::{
     self, GenericArgsRef, GenericParamDef, GenericParamDefKind, IsSuggestable, Ty, TyCtxt,
 };
 use rustc_session::lint::builtin::LATE_BOUND_LIFETIME_ARGUMENTS;
-use rustc_span::symbol::kw;
+use rustc_span::symbol::{kw, sym};
 use smallvec::SmallVec;
 
 /// Report an error that a generic argument did not match the generic parameter that was
@@ -41,9 +41,11 @@ fn generic_arg_mismatch_err(
     if let GenericParamDefKind::Const { .. } = param.kind {
         if matches!(arg, GenericArg::Type(hir::Ty { kind: hir::TyKind::Infer, .. })) {
             err.help("const arguments cannot yet be inferred with `_`");
-            if sess.is_nightly_build() {
-                err.help("add `#![feature(generic_arg_infer)]` to the crate attributes to enable");
-            }
+            tcx.disabled_nightly_features(
+                &mut err,
+                param.def_id.as_local().map(|local| tcx.local_def_id_to_hir_id(local)),
+                [(String::new(), sym::generic_arg_infer)],
+            );
         }
     }