Auto merge of rust-lang#113422 - Urgau:cast_ref_to_mut-pre-beta, r=Nilstrieb

Rename and allow `cast_ref_to_mut` lint

This PR is a small subset of rust-lang#112431, that is the renaming of the lint (`cast_ref_to_mut` -> `invalid_reference_casting`).

BUT also temporarily change the default level of the lint from deny-by-default to allow-by-default until rust-lang#112431 is merged.

r? `@Nilstrieb`

Author: bors

compiler/rustc_lint/messages.ftl

@@ -155,8 +155,6 @@ lint_builtin_unused_doc_comment = unused doc comment
 lint_builtin_while_true = denote infinite loops with `loop {"{"} ... {"}"}`
     .suggestion = use `loop`
 
-lint_cast_ref_to_mut = casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
-
 lint_check_name_deprecated = lint name `{$lint_name}` is deprecated and does not have an effect anymore. Use: {$new_name}
 
 lint_check_name_unknown = unknown lint: `{$lint_name}`
@@ -320,6 +318,8 @@ lint_invalid_nan_comparisons_eq_ne = incorrect NaN comparison, NaN cannot be dir
 
 lint_invalid_nan_comparisons_lt_le_gt_ge = incorrect NaN comparison, NaN is not orderable
 
+lint_invalid_reference_casting = casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
+
 lint_lintpass_by_hand = implementing `LintPass` by hand
     .help = try using `declare_lint_pass!` or `impl_lint_pass!` instead
 

compiler/rustc_lint/src/lib.rs

@@ -50,7 +50,6 @@ extern crate tracing;
 
 mod array_into_iter;
 pub mod builtin;
-mod cast_ref_to_mut;
 mod context;
 mod deref_into_dyn_supertrait;
 mod drop_forget_useless;
@@ -78,6 +77,7 @@ mod opaque_hidden_inferred_bound;
 mod pass_by_value;
 mod passes;
 mod redundant_semicolon;
+mod reference_casting;
 mod traits;
 mod types;
 mod unused;
@@ -99,7 +99,6 @@ use rustc_span::Span;
 
 use array_into_iter::ArrayIntoIter;
 use builtin::*;
-use cast_ref_to_mut::*;
 use deref_into_dyn_supertrait::*;
 use drop_forget_useless::*;
 use enum_intrinsics_non_enums::EnumIntrinsicsNonEnums;
@@ -119,6 +118,7 @@ use noop_method_call::*;
 use opaque_hidden_inferred_bound::*;
 use pass_by_value::*;
 use redundant_semicolon::*;
+use reference_casting::*;
 use traits::*;
 use types::*;
 use unused::*;
@@ -218,7 +218,7 @@ late_lint_methods!(
             BoxPointers: BoxPointers,
             PathStatements: PathStatements,
             LetUnderscore: LetUnderscore,
-            CastRefToMut: CastRefToMut,
+            InvalidReferenceCasting: InvalidReferenceCasting,
             // Depends on referenced function signatures in expressions
             UnusedResults: UnusedResults,
             NonUpperCaseGlobals: NonUpperCaseGlobals,

compiler/rustc_lint/src/lints.rs

@@ -743,10 +743,10 @@ pub enum InvalidFromUtf8Diag {
     },
 }
 
-// cast_ref_to_mut.rs
+// reference_casting.rs
 #[derive(LintDiagnostic)]
-#[diag(lint_cast_ref_to_mut)]
-pub struct CastRefToMutDiag;
+#[diag(lint_invalid_reference_casting)]
+pub struct InvalidReferenceCastingDiag;
 
 // hidden_unicode_codepoints.rs
 #[derive(LintDiagnostic)]

compiler/rustc_lint/src/cast_ref_to_mut.rs renamed to compiler/rustc_lint/src/reference_casting.rs

@@ -3,15 +3,16 @@ use rustc_hir::{Expr, ExprKind, MutTy, TyKind, UnOp};
 use rustc_middle::ty;
 use rustc_span::sym;
 
-use crate::{lints::CastRefToMutDiag, LateContext, LateLintPass, LintContext};
+use crate::{lints::InvalidReferenceCastingDiag, LateContext, LateLintPass, LintContext};
 
 declare_lint! {
-    /// The `cast_ref_to_mut` lint checks for casts of `&T` to `&mut T`
+    /// The `invalid_reference_casting` lint checks for casts of `&T` to `&mut T`
     /// without using interior mutability.
     ///
     /// ### Example
     ///
     /// ```rust,compile_fail
+    /// # #![deny(invalid_reference_casting)]
     /// fn x(r: &i32) {
     ///     unsafe {
     ///         *(r as *const i32 as *mut i32) += 1;
@@ -28,14 +29,14 @@ declare_lint! {
     ///
     /// `UnsafeCell` is the only way to obtain aliasable data that is considered
     /// mutable.
-    CAST_REF_TO_MUT,
-    Deny,
+    INVALID_REFERENCE_CASTING,
+    Allow,
     "casts of `&T` to `&mut T` without interior mutability"
 }
 
-declare_lint_pass!(CastRefToMut => [CAST_REF_TO_MUT]);
+declare_lint_pass!(InvalidReferenceCasting => [INVALID_REFERENCE_CASTING]);
 
-impl<'tcx> LateLintPass<'tcx> for CastRefToMut {
+impl<'tcx> LateLintPass<'tcx> for InvalidReferenceCasting {
     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
         let ExprKind::Unary(UnOp::Deref, e) = &expr.kind else {
             return;
@@ -68,7 +69,7 @@ impl<'tcx> LateLintPass<'tcx> for CastRefToMut {
 
         let e = e.peel_blocks();
         if let ty::Ref(..) = cx.typeck_results().node_type(e.hir_id).kind() {
-            cx.emit_spanned_lint(CAST_REF_TO_MUT, expr.span, CastRefToMutDiag);
+            cx.emit_spanned_lint(INVALID_REFERENCE_CASTING, expr.span, InvalidReferenceCastingDiag);
         }
     }
 }

src/tools/clippy/clippy_lints/src/renamed_lints.rs

@@ -31,7 +31,7 @@ pub static RENAMED_LINTS: &[(&str, &str)] = &[
     ("clippy::stutter", "clippy::module_name_repetitions"),
     ("clippy::to_string_in_display", "clippy::recursive_format_impl"),
     ("clippy::zero_width_space", "clippy::invisible_characters"),
-    ("clippy::cast_ref_to_mut", "cast_ref_to_mut"),
+    ("clippy::cast_ref_to_mut", "invalid_reference_casting"),
     ("clippy::clone_double_ref", "suspicious_double_ref_op"),
     ("clippy::cmp_nan", "invalid_nan_comparisons"),
     ("clippy::drop_bounds", "drop_bounds"),

src/tools/clippy/tests/ui/rename.fixed

@@ -28,9 +28,9 @@
 #![allow(clippy::module_name_repetitions)]
 #![allow(clippy::recursive_format_impl)]
 #![allow(clippy::invisible_characters)]
-#![allow(cast_ref_to_mut)]
 #![allow(suspicious_double_ref_op)]
 #![allow(invalid_nan_comparisons)]
+#![allow(invalid_reference_casting)]
 #![allow(drop_bounds)]
 #![allow(dropping_copy_types)]
 #![allow(dropping_references)]
@@ -79,7 +79,7 @@
 #![warn(clippy::module_name_repetitions)]
 #![warn(clippy::recursive_format_impl)]
 #![warn(clippy::invisible_characters)]
-#![warn(cast_ref_to_mut)]
+#![warn(invalid_reference_casting)]
 #![warn(suspicious_double_ref_op)]
 #![warn(invalid_nan_comparisons)]
 #![warn(drop_bounds)]

src/tools/clippy/tests/ui/rename.rs

@@ -28,9 +28,9 @@
 #![allow(clippy::module_name_repetitions)]
 #![allow(clippy::recursive_format_impl)]
 #![allow(clippy::invisible_characters)]
-#![allow(cast_ref_to_mut)]
 #![allow(suspicious_double_ref_op)]
 #![allow(invalid_nan_comparisons)]
+#![allow(invalid_reference_casting)]
 #![allow(drop_bounds)]
 #![allow(dropping_copy_types)]
 #![allow(dropping_references)]

src/tools/clippy/tests/ui/rename.stderr

@@ -174,11 +174,11 @@ error: lint `clippy::zero_width_space` has been renamed to `clippy::invisible_ch
 LL | #![warn(clippy::zero_width_space)]
    |         ^^^^^^^^^^^^^^^^^^^^^^^^ help: use the new name: `clippy::invisible_characters`
 
-error: lint `clippy::cast_ref_to_mut` has been renamed to `cast_ref_to_mut`
+error: lint `clippy::cast_ref_to_mut` has been renamed to `invalid_reference_casting`
   --> $DIR/rename.rs:82:9
    |
 LL | #![warn(clippy::cast_ref_to_mut)]
-   |         ^^^^^^^^^^^^^^^^^^^^^^^ help: use the new name: `cast_ref_to_mut`
+   |         ^^^^^^^^^^^^^^^^^^^^^^^ help: use the new name: `invalid_reference_casting`
 
 error: lint `clippy::clone_double_ref` has been renamed to `suspicious_double_ref_op`
   --> $DIR/rename.rs:83:9

src/tools/miri/tests/fail/both_borrows/shr_frozen_violation1.rs

@@ -1,7 +1,7 @@
 //@revisions: stack tree
 //@[tree]compile-flags: -Zmiri-tree-borrows
 
-#![allow(cast_ref_to_mut)]
+#![allow(invalid_reference_casting)]
 
 fn foo(x: &mut i32) -> i32 {
     *x = 5;

src/tools/miri/tests/fail/modifying_constants.rs

@@ -1,7 +1,7 @@
 // This should fail even without validation/SB
 //@compile-flags: -Zmiri-disable-validation -Zmiri-disable-stacked-borrows
 
-#![allow(cast_ref_to_mut)]
+#![allow(invalid_reference_casting)]
 
 fn main() {
     let x = &1; // the `&1` is promoted to a constant, but it used to be that only the pointer is marked static, not the pointee