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use super::utils::check_cast;
use super::TRANSMUTES_EXPRESSIBLE_AS_PTR_CASTS;
use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::sugg::Sugg;
use rustc_errors::Applicability;
use rustc_hir::Expr;
use rustc_lint::LateContext;
use rustc_middle::ty::{cast::CastKind, Ty};
/// Checks for `transmutes_expressible_as_ptr_casts` lint.
/// Returns `true` if it's triggered, otherwise returns `false`.
pub(super) fn check<'tcx>(
cx: &LateContext<'tcx>,
e: &'tcx Expr<'_>,
from_ty: Ty<'tcx>,
from_ty_adjusted: bool,
to_ty: Ty<'tcx>,
arg: &'tcx Expr<'_>,
) -> bool {
use CastKind::{AddrPtrCast, ArrayPtrCast, FnPtrAddrCast, FnPtrPtrCast, PtrAddrCast, PtrPtrCast};
let mut app = Applicability::MachineApplicable;
let sugg = match check_cast(cx, e, from_ty, to_ty) {
Some(PtrPtrCast | AddrPtrCast | ArrayPtrCast | FnPtrPtrCast | FnPtrAddrCast) => {
Sugg::hir_with_context(cx, arg, e.span.ctxt(), "..", &mut app)
.as_ty(to_ty.to_string())
.to_string()
},
Some(PtrAddrCast) if !from_ty_adjusted => Sugg::hir_with_context(cx, arg, e.span.ctxt(), "..", &mut app)
.as_ty(to_ty.to_string())
.to_string(),
// The only adjustments here would be ref-to-ptr and unsize coercions. The result of an unsize coercions can't
// be transmuted to a usize. For ref-to-ptr coercions, borrows need to be cast to a pointer before being cast to
// a usize.
Some(PtrAddrCast) => format!(
"{} as {to_ty}",
Sugg::hir_with_context(cx, arg, e.span.ctxt(), "..", &mut app).as_ty(from_ty)
),
_ => return false,
};
span_lint_and_sugg(
cx,
TRANSMUTES_EXPRESSIBLE_AS_PTR_CASTS,
e.span,
&format!("transmute from `{from_ty}` to `{to_ty}` which could be expressed as a pointer cast instead"),
"try",
sugg,
app,
);
true
}
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