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use rustc_hir::{Expr, ExprKind};
use rustc_span::sym;
use crate::LateContext;
/// Given an expression, peel all of casts (`<expr> as ...`, `<expr>.cast{,_mut,_const}()`,
/// `ptr::from_ref(<expr>)`, ...) and init expressions.
///
/// Returns the innermost expression and a boolean representing if one of the casts was
/// `UnsafeCell::raw_get(<expr>)`
pub(crate) fn peel_casts<'tcx>(
cx: &LateContext<'tcx>,
mut e: &'tcx Expr<'tcx>,
) -> (&'tcx Expr<'tcx>, bool) {
let mut gone_trough_unsafe_cell_raw_get = false;
loop {
e = e.peel_blocks();
// <expr> as ...
e = if let ExprKind::Cast(expr, _) = e.kind {
expr
// <expr>.cast(), <expr>.cast_mut() or <expr>.cast_const()
} else if let ExprKind::MethodCall(_, expr, [], _) = e.kind
&& let Some(def_id) = cx.typeck_results().type_dependent_def_id(e.hir_id)
&& matches!(
cx.tcx.get_diagnostic_name(def_id),
Some(sym::ptr_cast | sym::const_ptr_cast | sym::ptr_cast_mut | sym::ptr_cast_const)
)
{
expr
// ptr::from_ref(<expr>), UnsafeCell::raw_get(<expr>) or mem::transmute<_, _>(<expr>)
} else if let ExprKind::Call(path, [arg]) = e.kind
&& let ExprKind::Path(ref qpath) = path.kind
&& let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id()
&& matches!(
cx.tcx.get_diagnostic_name(def_id),
Some(sym::ptr_from_ref | sym::unsafe_cell_raw_get | sym::transmute)
)
{
if cx.tcx.is_diagnostic_item(sym::unsafe_cell_raw_get, def_id) {
gone_trough_unsafe_cell_raw_get = true;
}
arg
} else {
let init = cx.expr_or_init(e);
if init.hir_id != e.hir_id {
init
} else {
break;
}
};
}
(e, gone_trough_unsafe_cell_raw_get)
}
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