Auto merge of #122524 - cuviper:beta-next, r=cuviper

[beta] backports

- AST validation: Improve handling of inherent impls nested within functions and anon consts #122004
- Downgrade const eval dangling ptr in final to future incompat lint #122204

r? cuviper

Author: bors

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -925,35 +925,38 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                         only_trait: only_trait.then_some(()),
                     };
 
-                self.visibility_not_permitted(
-                    &item.vis,
-                    errors::VisibilityNotPermittedNote::IndividualImplItems,
-                );
-                if let &Unsafe::Yes(span) = unsafety {
-                    self.dcx().emit_err(errors::InherentImplCannotUnsafe {
-                        span: self_ty.span,
-                        annotation_span: span,
-                        annotation: "unsafe",
-                        self_ty: self_ty.span,
-                    });
-                }
-                if let &ImplPolarity::Negative(span) = polarity {
-                    self.dcx().emit_err(error(span, "negative", false));
-                }
-                if let &Defaultness::Default(def_span) = defaultness {
-                    self.dcx().emit_err(error(def_span, "`default`", true));
-                }
-                if let &Const::Yes(span) = constness {
-                    self.dcx().emit_err(error(span, "`const`", true));
-                }
+                self.with_in_trait_impl(None, |this| {
+                    this.visibility_not_permitted(
+                        &item.vis,
+                        errors::VisibilityNotPermittedNote::IndividualImplItems,
+                    );
+                    if let &Unsafe::Yes(span) = unsafety {
+                        this.dcx().emit_err(errors::InherentImplCannotUnsafe {
+                            span: self_ty.span,
+                            annotation_span: span,
+                            annotation: "unsafe",
+                            self_ty: self_ty.span,
+                        });
+                    }
+                    if let &ImplPolarity::Negative(span) = polarity {
+                        this.dcx().emit_err(error(span, "negative", false));
+                    }
+                    if let &Defaultness::Default(def_span) = defaultness {
+                        this.dcx().emit_err(error(def_span, "`default`", true));
+                    }
+                    if let &Const::Yes(span) = constness {
+                        this.dcx().emit_err(error(span, "`const`", true));
+                    }
 
-                self.visit_vis(&item.vis);
-                self.visit_ident(item.ident);
-                self.with_tilde_const(Some(DisallowTildeConstContext::Impl(item.span)), |this| {
-                    this.visit_generics(generics)
+                    this.visit_vis(&item.vis);
+                    this.visit_ident(item.ident);
+                    this.with_tilde_const(
+                        Some(DisallowTildeConstContext::Impl(item.span)),
+                        |this| this.visit_generics(generics),
+                    );
+                    this.visit_ty(self_ty);
+                    walk_list!(this, visit_assoc_item, items, AssocCtxt::Impl);
                 });
-                self.visit_ty(self_ty);
-                walk_list!(self, visit_assoc_item, items, AssocCtxt::Impl);
                 walk_list!(self, visit_attribute, &item.attrs);
                 return; // Avoid visiting again.
             }

compiler/rustc_const_eval/src/errors.rs

@@ -27,10 +27,13 @@ pub(crate) struct DanglingPtrInFinal {
     pub kind: InternKind,
 }
 
-#[derive(Diagnostic)]
+#[derive(LintDiagnostic)]
 #[diag(const_eval_mutable_ptr_in_final)]
 pub(crate) struct MutablePtrInFinal {
-    #[primary_span]
+    // rust-lang/rust#122153: This was marked as `#[primary_span]` under
+    // `derive(Diagnostic)`. Since we expect we may hard-error in future, we are
+    // keeping the field (and skipping it under `derive(LintDiagnostic)`).
+    #[skip_arg]
     pub span: Span,
     pub kind: InternKind,
 }

compiler/rustc_const_eval/src/interpret/intern.rs

@@ -19,6 +19,7 @@ use rustc_errors::ErrorGuaranteed;
 use rustc_hir as hir;
 use rustc_middle::mir::interpret::{CtfeProvenance, InterpResult};
 use rustc_middle::ty::layout::TyAndLayout;
+use rustc_session::lint;
 
 use super::{AllocId, Allocation, InterpCx, MPlaceTy, Machine, MemoryKind, PlaceTy};
 use crate::const_eval;
@@ -195,10 +196,13 @@ pub fn intern_const_alloc_recursive<
         })?;
     }
     if found_bad_mutable_pointer {
-        return Err(ecx
-            .tcx
-            .dcx()
-            .emit_err(MutablePtrInFinal { span: ecx.tcx.span, kind: intern_kind }));
+        let err_diag = MutablePtrInFinal { span: ecx.tcx.span, kind: intern_kind };
+        ecx.tcx.emit_node_span_lint(
+            lint::builtin::CONST_EVAL_MUTABLE_PTR_IN_FINAL_VALUE,
+            ecx.best_lint_scope(),
+            err_diag.span,
+            err_diag,
+        )
     }
 
     Ok(())

compiler/rustc_lint_defs/src/builtin.rs

@@ -27,6 +27,7 @@ declare_lint_pass! {
         CENUM_IMPL_DROP_CAST,
         COHERENCE_LEAK_CHECK,
         CONFLICTING_REPR_HINTS,
+        CONST_EVAL_MUTABLE_PTR_IN_FINAL_VALUE,
         CONST_EVALUATABLE_UNCHECKED,
         CONST_ITEM_MUTATION,
         CONST_PATTERNS_WITHOUT_PARTIAL_EQ,
@@ -2905,6 +2906,51 @@ declare_lint! {
     @feature_gate = sym::strict_provenance;
 }
 
+declare_lint! {
+    /// The `const_eval_mutable_ptr_in_final_value` lint detects if a mutable pointer
+    /// has leaked into the final value of a const expression.
+    ///
+    /// ### Example
+    ///
+    /// ```rust
+    /// pub enum JsValue {
+    ///     Undefined,
+    ///     Object(std::cell::Cell<bool>),
+    /// }
+    ///
+    /// impl ::std::ops::Drop for JsValue {
+    ///     fn drop(&mut self) {}
+    /// }
+    ///
+    /// const UNDEFINED: &JsValue = &JsValue::Undefined;
+    ///
+    /// fn main() {
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// In the 1.77 release, the const evaluation machinery adopted some
+    /// stricter rules to reject expressions with values that could
+    /// end up holding mutable references to state stored in static memory
+    /// (which is inherently immutable).
+    ///
+    /// This is a [future-incompatible] lint to ease the transition to an error.
+    /// See [issue #122153] for more details.
+    ///
+    /// [issue #122153]: https://github.com/rust-lang/rust/issues/122153
+    /// [future-incompatible]: ../index.md#future-incompatible-lints
+    pub CONST_EVAL_MUTABLE_PTR_IN_FINAL_VALUE,
+    Warn,
+    "detects a mutable pointer that has leaked into final value of a const expression",
+    @future_incompatible = FutureIncompatibleInfo {
+        reason: FutureIncompatibilityReason::FutureReleaseErrorReportInDeps,
+        reference: "issue #122153 <https://github.com/rust-lang/rust/issues/122153>",
+    };
+}
+
 declare_lint! {
     /// The `const_evaluatable_unchecked` lint detects a generic constant used
     /// in a type.

tests/ui/consts/const-eval/heap/alloc_intrinsic_untyped.rs

@@ -1,9 +1,11 @@
 #![feature(core_intrinsics)]
 #![feature(const_heap)]
 #![feature(const_mut_refs)]
+#![deny(const_eval_mutable_ptr_in_final_value)]
 use std::intrinsics;
 
 const BAR: *mut i32 = unsafe { intrinsics::const_allocate(4, 4) as *mut i32 };
 //~^ error: mutable pointer in final value of constant
+//~| WARNING this was previously accepted by the compiler
 
 fn main() {}

tests/ui/consts/const-eval/heap/alloc_intrinsic_untyped.stderr

@@ -1,8 +1,31 @@
 error: encountered mutable pointer in final value of constant
-  --> $DIR/alloc_intrinsic_untyped.rs:6:1
+  --> $DIR/alloc_intrinsic_untyped.rs:7:1
    |
 LL | const BAR: *mut i32 = unsafe { intrinsics::const_allocate(4, 4) as *mut i32 };
    | ^^^^^^^^^^^^^^^^^^^
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #122153 <https://github.com/rust-lang/rust/issues/122153>
+note: the lint level is defined here
+  --> $DIR/alloc_intrinsic_untyped.rs:4:9
+   |
+LL | #![deny(const_eval_mutable_ptr_in_final_value)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to 1 previous error
 
+Future incompatibility report: Future breakage diagnostic:
+error: encountered mutable pointer in final value of constant
+  --> $DIR/alloc_intrinsic_untyped.rs:7:1
+   |
+LL | const BAR: *mut i32 = unsafe { intrinsics::const_allocate(4, 4) as *mut i32 };
+   | ^^^^^^^^^^^^^^^^^^^
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #122153 <https://github.com/rust-lang/rust/issues/122153>
+note: the lint level is defined here
+  --> $DIR/alloc_intrinsic_untyped.rs:4:9
+   |
+LL | #![deny(const_eval_mutable_ptr_in_final_value)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+

tests/ui/consts/future-incompat-mutable-in-final-value-issue-121610.rs

@@ -0,0 +1,18 @@
+// check-pass
+use std::cell::Cell;
+
+pub enum JsValue {
+    Undefined,
+    Object(Cell<bool>),
+}
+
+impl ::std::ops::Drop for JsValue {
+    fn drop(&mut self) {}
+}
+
+const UNDEFINED: &JsValue = &JsValue::Undefined;
+    //~^ WARN encountered mutable pointer in final value of constant
+    //~| WARN this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+
+fn main() {
+}

tests/ui/consts/future-incompat-mutable-in-final-value-issue-121610.stderr

@@ -0,0 +1,23 @@
+warning: encountered mutable pointer in final value of constant
+  --> $DIR/future-incompat-mutable-in-final-value-issue-121610.rs:13:1
+   |
+LL | const UNDEFINED: &JsValue = &JsValue::Undefined;
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #122153 <https://github.com/rust-lang/rust/issues/122153>
+   = note: `#[warn(const_eval_mutable_ptr_in_final_value)]` on by default
+
+warning: 1 warning emitted
+
+Future incompatibility report: Future breakage diagnostic:
+warning: encountered mutable pointer in final value of constant
+  --> $DIR/future-incompat-mutable-in-final-value-issue-121610.rs:13:1
+   |
+LL | const UNDEFINED: &JsValue = &JsValue::Undefined;
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #122153 <https://github.com/rust-lang/rust/issues/122153>
+   = note: `#[warn(const_eval_mutable_ptr_in_final_value)]` on by default
+