From b6900f27b61aa44fd623b65b6a010d54bf587f46 Mon Sep 17 00:00:00 2001
From: Ada Alakbarova <ada.alakbarova@proton.me>
Date: Tue, 11 Nov 2025 22:51:34 +0100
Subject: [PATCH] [DO NOT MERGE] eviscerate `cast_ptr_alignment`

As described in
https://rust-lang.zulipchat.com/#narrow/channel/257328-clippy/topic/Move.20.60cast_ptr_alignment.60.20to.20.60correctness.60.20again/near/546034660
---
 clippy_lints/src/casts/cast_ptr_alignment.rs | 80 +-------------------
 1 file changed, 3 insertions(+), 77 deletions(-)

diff --git a/clippy_lints/src/casts/cast_ptr_alignment.rs b/clippy_lints/src/casts/cast_ptr_alignment.rs
index 7d14ba7fcf13..9035e3d78ca7 100644
--- a/clippy_lints/src/casts/cast_ptr_alignment.rs
+++ b/clippy_lints/src/casts/cast_ptr_alignment.rs
@@ -1,3 +1,4 @@
+#![expect(unused)]
 use clippy_utils::diagnostics::span_lint;
 use clippy_utils::ty::is_c_void;
 use clippy_utils::{get_parent_expr, is_hir_ty_cfg_dependant, sym};
@@ -8,81 +9,6 @@ use rustc_middle::ty::{self, Ty};
 
 use super::CAST_PTR_ALIGNMENT;
 
-pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>, cast_from: Ty<'tcx>, cast_to: Ty<'tcx>) {
-    lint_cast_ptr_alignment(cx, expr, cast_from, cast_to);
-}
+pub(super) fn check<'tcx>(_: &LateContext<'tcx>, _: &Expr<'_>, _: Ty<'tcx>, _: Ty<'tcx>) {}
 
-pub(super) fn check_cast_method(cx: &LateContext<'_>, expr: &Expr<'_>) {
-    if let ExprKind::MethodCall(method_path, self_arg, [], _) = &expr.kind
-        && method_path.ident.name == sym::cast
-        && let Some(generic_args) = method_path.args
-        && let [GenericArg::Type(cast_to)] = generic_args.args
-        // There probably is no obvious reason to do this, just to be consistent with `as` cases.
-        && !is_hir_ty_cfg_dependant(cx, cast_to.as_unambig_ty())
-    {
-        let (cast_from, cast_to) = (cx.typeck_results().expr_ty(self_arg), cx.typeck_results().expr_ty(expr));
-        lint_cast_ptr_alignment(cx, expr, cast_from, cast_to);
-    }
-}
-
-fn lint_cast_ptr_alignment<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>, cast_from: Ty<'tcx>, cast_to: Ty<'tcx>) {
-    if let ty::RawPtr(from_ptr_ty, _) = *cast_from.kind()
-        && let ty::RawPtr(to_ptr_ty, _) = *cast_to.kind()
-        && let Ok(from_layout) = cx.layout_of(from_ptr_ty)
-        && let Ok(to_layout) = cx.layout_of(to_ptr_ty)
-        && from_layout.align.abi < to_layout.align.abi
-        // with c_void, we inherently need to trust the user
-        && !is_c_void(cx, from_ptr_ty)
-        // when casting from a ZST, we don't know enough to properly lint
-        && !from_layout.is_zst()
-        && !is_used_as_unaligned(cx, expr)
-    {
-        span_lint(
-            cx,
-            CAST_PTR_ALIGNMENT,
-            expr.span,
-            format!(
-                "casting from `{cast_from}` to a more-strictly-aligned pointer (`{cast_to}`) ({} < {} bytes)",
-                from_layout.align.bytes(),
-                to_layout.align.bytes(),
-            ),
-        );
-    }
-}
-
-fn is_used_as_unaligned(cx: &LateContext<'_>, e: &Expr<'_>) -> bool {
-    let Some(parent) = get_parent_expr(cx, e) else {
-        return false;
-    };
-    match parent.kind {
-        ExprKind::MethodCall(name, self_arg, ..) if self_arg.hir_id == e.hir_id => {
-            if matches!(name.ident.name, sym::read_unaligned | sym::write_unaligned)
-                && let Some(def_id) = cx.typeck_results().type_dependent_def_id(parent.hir_id)
-                && let Some(def_id) = cx.tcx.impl_of_assoc(def_id)
-                && cx.tcx.type_of(def_id).instantiate_identity().is_raw_ptr()
-            {
-                true
-            } else {
-                false
-            }
-        },
-        ExprKind::Call(func, [arg, ..]) if arg.hir_id == e.hir_id => {
-            if let ExprKind::Path(path) = &func.kind
-                && let Some(def_id) = cx.qpath_res(path, func.hir_id).opt_def_id()
-                && let Some(name) = cx.tcx.get_diagnostic_name(def_id)
-                && matches!(
-                    name,
-                    sym::ptr_write_unaligned
-                        | sym::ptr_read_unaligned
-                        | sym::intrinsics_unaligned_volatile_load
-                        | sym::intrinsics_unaligned_volatile_store
-                )
-            {
-                true
-            } else {
-                false
-            }
-        },
-        _ => false,
-    }
-}
+pub(super) fn check_cast_method(_: &LateContext<'_>, _: &Expr<'_>) {}