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|
use clippy_utils::{diagnostics::span_lint_and_then, meets_msrv, msrvs, source};
use if_chain::if_chain;
use rustc_ast::Mutability;
use rustc_hir::{Expr, ExprKind, Node};
use rustc_lint::LateContext;
use rustc_middle::ty::{self, layout::LayoutOf, Ty, TypeAndMut};
use rustc_semver::RustcVersion;
use super::CAST_SLICE_DIFFERENT_SIZES;
pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'tcx>, msrv: Option<RustcVersion>) {
// suggestion is invalid if `ptr::slice_from_raw_parts` does not exist
if !meets_msrv(msrv, msrvs::PTR_SLICE_RAW_PARTS) {
return;
}
// if this cast is the child of another cast expression then don't emit something for it, the full
// chain will be analyzed
if is_child_of_cast(cx, expr) {
return;
}
if let Some(CastChainInfo {
left_cast,
start_ty,
end_ty,
}) = expr_cast_chain_tys(cx, expr)
{
if let (Ok(from_layout), Ok(to_layout)) = (cx.layout_of(start_ty.ty), cx.layout_of(end_ty.ty)) {
let from_size = from_layout.size.bytes();
let to_size = to_layout.size.bytes();
if from_size != to_size && from_size != 0 && to_size != 0 {
span_lint_and_then(
cx,
CAST_SLICE_DIFFERENT_SIZES,
expr.span,
&format!(
"casting between raw pointers to `[{}]` (element size {from_size}) and `[{}]` (element size {to_size}) does not adjust the count",
start_ty.ty, end_ty.ty,
),
|diag| {
let ptr_snippet = source::snippet(cx, left_cast.span, "..");
let (mutbl_fn_str, mutbl_ptr_str) = match end_ty.mutbl {
Mutability::Mut => ("_mut", "mut"),
Mutability::Not => ("", "const"),
};
let sugg = format!(
"core::ptr::slice_from_raw_parts{mutbl_fn_str}({ptr_snippet} as *{mutbl_ptr_str} {}, ..)",
// get just the ty from the TypeAndMut so that the printed type isn't something like `mut
// T`, extract just the `T`
end_ty.ty
);
diag.span_suggestion(
expr.span,
&format!("replace with `ptr::slice_from_raw_parts{mutbl_fn_str}`"),
sugg,
rustc_errors::Applicability::HasPlaceholders,
);
},
);
}
}
}
}
fn is_child_of_cast(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
let map = cx.tcx.hir();
if_chain! {
if let Some(parent_id) = map.find_parent_node(expr.hir_id);
if let Some(parent) = map.find(parent_id);
then {
let expr = match parent {
Node::Block(block) => {
if let Some(parent_expr) = block.expr {
parent_expr
} else {
return false;
}
},
Node::Expr(expr) => expr,
_ => return false,
};
matches!(expr.kind, ExprKind::Cast(..))
} else {
false
}
}
}
/// Returns the type T of the pointed to *const [T] or *mut [T] and the mutability of the slice if
/// the type is one of those slices
fn get_raw_slice_ty_mut(ty: Ty<'_>) -> Option<TypeAndMut<'_>> {
match ty.kind() {
ty::RawPtr(TypeAndMut { ty: slice_ty, mutbl }) => match slice_ty.kind() {
ty::Slice(ty) => Some(TypeAndMut { ty: *ty, mutbl: *mutbl }),
_ => None,
},
_ => None,
}
}
struct CastChainInfo<'tcx> {
/// The left most part of the cast chain, or in other words, the first cast in the chain
/// Used for diagnostics
left_cast: &'tcx Expr<'tcx>,
/// The starting type of the cast chain
start_ty: TypeAndMut<'tcx>,
/// The final type of the cast chain
end_ty: TypeAndMut<'tcx>,
}
/// Returns a `CastChainInfo` with the left-most cast in the chain and the original ptr T and final
/// ptr U if the expression is composed of casts.
/// Returns None if the expr is not a Cast
fn expr_cast_chain_tys<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'tcx>) -> Option<CastChainInfo<'tcx>> {
if let ExprKind::Cast(cast_expr, _cast_to_hir_ty) = expr.peel_blocks().kind {
let cast_to = cx.typeck_results().expr_ty(expr);
let to_slice_ty = get_raw_slice_ty_mut(cast_to)?;
// If the expression that makes up the source of this cast is itself a cast, recursively
// call `expr_cast_chain_tys` and update the end type with the final target type.
// Otherwise, this cast is not immediately nested, just construct the info for this cast
if let Some(prev_info) = expr_cast_chain_tys(cx, cast_expr) {
Some(CastChainInfo {
end_ty: to_slice_ty,
..prev_info
})
} else {
let cast_from = cx.typeck_results().expr_ty(cast_expr);
let from_slice_ty = get_raw_slice_ty_mut(cast_from)?;
Some(CastChainInfo {
left_cast: cast_expr,
start_ty: from_slice_ty,
end_ty: to_slice_ty,
})
}
} else {
None
}
}
|
